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Abstract

Human activities are the main current driver of global change. From hunter-gatherers through to Neolithic societies-and particularly in contemporary industrialised countries-humans have (voluntarily or involuntarily) provided other animals with food, often with a high spatio-temporal predictability. Nowadays, as much as 30-40% of all food produced in Earth is wasted. We argue here that predictable anthropogenic food subsidies (PAFS) provided historically by humans to animals has shaped many communities and ecosystems as we see them nowadays. PAFS improve individual fitness triggering population increases of opportunistic species, which may affect communities, food webs and ecosystems by altering processes such as competition, predator-prey interactions and nutrient transfer between biotopes and ecosystems. We also show that PAFS decrease temporal population variability, increase resilience of opportunistic species and reduce community diversity. Recent environmental policies, such as the regulation of dumps or the ban of fishing discards, constitute natural experiments that should improve our understanding of the role of food supply in a range of ecological and evolutionary processes at the ecosystem level. Comparison of subsidised and non-subsidised ecosystems can help predict changes in diversity and the related ecosystem services that have suffered the impact of other global change agents.

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... Therefore, quantitatively, during periods of food shortage the ecosystem still offered sufficient resources to cover their energetic requirements. However, qualitatively, over the long-term, these predictable resources could have detrimental impacts on fitness and demographic parameters because they entail greater human-related risks (Arrondo et al., 2020;Casas-Díaz et al., 2016;Oro et al., 2013;Plaza & Lambertucci, 2017). ...
... As a result, we could expect food availability to have a higher impact on the most abundant species with lower dietary plasticity, such as griffon vultures, suggesting that this species could be more prone to nonnatural mortality when sudden changes in food availability affect their foraging behavior, increasing the use of more anthropized areas than resulted in a significantly higher individual mortality risk (Arrondo et al., 2020;Cortés-Avizanda et al., 2015). Thus, quantitatively, food availability should not be a limiting factor during sanitary restrictions , although qualitatively food shortages could influence breeding output and survival Oro et al., 2013), resulting in modified foraging behavior with changes in food availability, thereby increasing non-natural mortality. As our models show, while the griffon vulture population was F I G U R E 6 The scavenger ecosystem Population Dynamic P System model presented in this work has been used to simulate the results (10 years) of the experiments necessary to obtain the response surface using the Box-Behnken methodology. ...
... Our findings suggest that food shortages due to the implementation of sanitary policies resulted in only a moderate impact on vulture population growth, probably thanks to the supplementary feeding network which provided alternative food and the designation of Supplementary Feeding Zones (Morales-Reyes et al., 2017). Also important was the availability of alternative food sources (intensive farms, landfills) that were used more regularly than expected (Fern andez-G omez et al., 2022;Plaza & Lambertucci, 2017), although these sites can have detrimental effects on fitness and survival, as has been documented for some obligate and facultative scavengers (Oliva-Vidal, Martínez, et al., 2022;Oliva-Vidal, Sebasti an-Gonz alez, et al., 2022;Oro et al., 2013;Plaza & Lambertucci, 2018). The increasing use of veterinary drugs, rodenticides, and other toxic substances may also have long-term effects on vulture populations. ...
Article
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The prediction of population responses to environmental changes, including the effects of different management scenarios, is a useful tool and a necessary contributor to improving conservation decisions. Empirical datasets based on long‐term monitoring studies are essential to assess the robustness of retrospective modeling predictions on biodiversity. These allow checks on the performance of modeling projections and enable improvements to be made to future models, based on the errors detected. Here, we assess the performance of our earlier model to assess the impact of vulture food shortages caused by sanitary regulations on the population dynamics of Spanish vultures during the past decade (2009–2019). This model forecasts the population trends of three vulture species (griffon, Egyptian, and bearded vultures) in Spain (home to 90% of the European vulture population) under various food shortage scenarios. We show that it underestimated bearded and griffon vulture population numbers and overestimated Egyptian vultures. The model suggested that the most plausible food shortage scenario involved an approximate 50% reduction of livestock carcass availability in the ecosystem compared with the previous situation without sanitary carcass removal. However, the observed annual population growth for the period 2009–2019 (7.8% for griffon vulture, 2.4% for Egyptian vulture, and 3.5% for bearded vulture) showed that food shortages had little impact on vulture population dynamics. After assessing the robustness of the model, we developed a new model with updated demographic parameters and foraging movements under different hypothetical food shortage scenarios for the period 2019–2029. This model forecasts annual population increases of about 3.6% for the bearded vulture, 3.7% for the Egyptian vulture, and 1.1% for the Griffon vulture. Our findings suggest that food shortages due to the implementation of sanitary policies resulted in only a moderate impact on vulture population growth, probably thanks to the supplementary feeding network which provided alternative food. Also important was the availability of alternative food sources (intensive farms, landfills) that were used more regularly than expected. We discuss the computational performance of our modeling approach and its management consequences to improve future conservation measures for these threatened species, which provide essential ecosystem services.
... Las pesquerías de arrastre, en particular, ponen a disposición de las aves que se alimentan en la superficie y en los primeros metros de agua, una cantidad significativa de recursos a los que no tendrían acceso en condiciones naturales. Por otro lado, los basurales urbanos constituyen importantes fuentes de alimento utilizadas por una gran variedad de especies de aves alrededor del mundo, particularmente especies oportunistas y carroñeras (ver revisiones en Oro et al. 2013y Plaza & Lambertucci 2017. Debido a que este alimento es en general más abundante, de más fácil acceso y más predecible que el de origen natural, su aprovechamiento ha generado efectos positivos tanto a nivel individual como poblacional en un gran número de especies (Oro et al. 2013, y referencias allí citadas). ...
... Por otro lado, los basurales urbanos constituyen importantes fuentes de alimento utilizadas por una gran variedad de especies de aves alrededor del mundo, particularmente especies oportunistas y carroñeras (ver revisiones en Oro et al. 2013y Plaza & Lambertucci 2017. Debido a que este alimento es en general más abundante, de más fácil acceso y más predecible que el de origen natural, su aprovechamiento ha generado efectos positivos tanto a nivel individual como poblacional en un gran número de especies (Oro et al. 2013, y referencias allí citadas). Sin embargo, el uso de estos recursos de origen antrópico puede resultar en mortalidad y aumentar la probabilidad de contraer infecciones por patógenos, de envenenamiento por ingestión de sustancias tóxicas y/o de consumir accidentalmente objetos no comestibles como plásticos (ver revisiones en Plaza & Lambertucci 2017, Montevecchi 2023. ...
... Muchos estudios muestran que el uso de subsidios de alimento de origen antrópico puede favorecer la fecundidad y supervivencia de los individuos de muchas especies y, en consecuencia, el crecimiento poblacional (ver revisión en Oro et al. 2013). La información analizada indica que, entre las aves marinas que reproducen en la costa patagónica argentina, la Gaviota Cocinera es la que se asocia más frecuentemente y en mayores abundancias a fuentes de alimento derivadas de actividades humanas y, posiblemente, la única que podría ver significativamente afectada su ecología alimentaria y demografía por este comportamiento. ...
Article
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Las aves marinas son uno de los grupos de aves más amenazados a nivel global. Sin embargo, varias actividades humanas también proveen recursos que estas aves pueden utilizar en su beneficio. Se presenta una síntesis del conocimiento sobre el uso de recursos antrópicos por parte de las aves marinas que se reproducen en el litoral patagónico argentino. Las investigaciones realizadas indican que un total de quince especies utilizan recursos antrópicos para su alimentación y/o nidificación durante los meses de la temporada reproductiva. De los diferentes recursos de alimento de origen antrópico identificados, el provisto por la pesca comercial durante las operaciones en el mar es utilizado por el mayor número de especies (doce) y el que representa la oferta de mayor extensión geográfica. Un menor número de especies hacen uso de residuos urbanos (cuatro) y de recursos derivados de la pesca recreativa (tres) y la actividad agrícola-ganadera (seis). En relación a los recursos antrópicos para nidificar, la información disponible es mayormente anecdótica, e indica que seis especies aprovechan ambientes y/o estructuras antrópicas para construir sus nidos, y siete incorporan materiales antrópicos en los mismos. Se discuten los posibles beneficios y costos asociados a dicho uso, y se consideran los posibles conflictos derivados en relación a otras especies y las poblaciones humanas. Se espera que esta síntesis de conocimiento, identificando limitaciones de estudios previos y vacíos de información, contribuya a la definición de prioridades de investigación y al desarrollo de recomendaciones para el monitoreo de las interacciones entre aves marinas reproductoras y actividades humanas.
... As cities grow larger and natural spaces get smaller, several birds find food, shelter, and breed in these artificial yet polluted areas. A deeper analysis of this development deepens our understanding of human and wildlife interactions (Oro et al. 2013). Dump areas provide optimal bird habitats in towns and cities, where natural habitats are frequently fragmented or deteriorated. ...
... Municipal solid waste results from human activities, causing significant levels of pollution and health problems. Food leftovers produced by people act as food subsidies for other species, vastly changing the ecosystem structure and function, especially for leftovers from farms and dumpsites (Oro et al. 2013). Municipal solid waste mainly comes from places where people live, including small businesses, hospitals, clinics, and other commercial activities. ...
... With this knowledge, we can generate better conservation efforts and strategies for protecting bird populations and their homes (Maurice et al. 2020). Food subsidies from the dumpsites have multiple effects on bird communities, including behaviour changes and health impacts (Robb et al. 2008, Oro et al. 2013. Birds feed on organic foods like meat, fish, fruits, and eggs, ORNIS HUNGARICA 2024. ...
Article
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Urban dumpsites, often regarded as environmental eyesores, may play an unexpected ecological role by providing habitats for avian species. In this context, the present study was conducted to justify whether dumpsites can sustain bird populations and enhance urban biodiversity. We recorded the bird abundance and species richness through surveys at four well-known urban dumpsites in Kolkata and surrounding areas between February and June 2024. We encountered a variety of common and rare bird species that use the dumpsite for feeding, breeding, and roosting using established methods. The dumping area close to the agricultural fields had a higher bird species richness compared to the urbanized area. However, the urban dumping areas exhibited comparatively higher bird abundance. House Crow (Corvus splendens) and Cattle Egret (Bubulcus ibis) were the two most common species at the dumpsites. This work emphasizes the importance of studying the bird groups concerning landfill sites and management, as a significant influx of birds could lead to various environmental challenges in metropolitan areas.
... Urbanization and the associated increase in anthropogenic waste materials have led to the proliferation of generalist scavenger species, such as the pied crow (Corvus albus), in many developing regions (Marzluff & Neatherlin, 2006;Oro et al., 2013). These urban-adapted birds play a crucial role in the management of solid waste by consuming food scraps, organic refuse, and other waste products (Djagoun et al., 2020). ...
... During the dry season, when natural food sources like insects, small vertebrates, and plant matter become scarce, pied crows have been observed to increasingly rely on anthropogenic waste materials as a food source (Djagoun et al., 2020;Yom-Tov, 2003). This shift in foraging strategy leads Pied Crows to spend more time and effort scavenging at waste disposal sites, landfills, and other areas with high concentrations of human-generated refuse (Oro et al., 2013). Conversely, during the rainy season, the increased precipitation and lower temperatures can result in a greater availability of natural food sources for Pied Crows, potentially reducing their need to rely on waste materials (Shochat, 2004). ...
... In regions of sub-Saharan Africa with more consistent rainfall, such as the tropical rainforests of Central Africa, pied crows may have access to a more stable and diverse natural prey base throughout the year, which could minimize their reliance on anthropogenic waste materials (Shochat, 2004). However, even in these areas, extreme weather events like droughts or heavy rainfall may still impact the availability and accessibility of both natural and anthropogenic food sources, potentially influencing pied crow foraging behavior (Oro et al., 2013). The potential impact of weather changes on pied crow foraging behavior in different sub-Saharan African regions can have important implications for waste management strategies and the mitigation of the potential negative impacts of these urban-adapted birds on local ecosystems (Oro et al., 2013;Shochat, 2004). ...
Article
Pied crow (Corvus albus) is a highly adaptable and opportunistic scavenger species that has successfully colonized many urban and peri-urban areas across the African continent. The impact of weather changes on pied crow foraging behavior in different African regions can have important implications for waste management strategies and the mitigation of the potential negative impacts of these urban-adapted birds on local ecosystems. This study aimed to investigate how changes in weather condition influence the foraging strategy of pied crow (Corvus albus) on waste materials in Bonaberi neighborhood of Douala in Cameroon. Observational surveys were conducted over a 4-month period in Bonaberi to monitor the foraging behavior of pied crows. Data were collected on crow numbers, time spent foraging, food types consumed, and foraging locations during both the dry and rainy seasons. Weather data, including sunshine, rainfall, cloud cover, and wind speed, were also recorded. Statistical models were used to analyze the relationship between weather variables and pied crow foraging patterns. In this study, weather condition revealed a significant association on day-period X2=116.908 df=6 P=0.000, aggregation behavior of birds X2=12.514 df12 P<0.05, and the behavioral activity of birds X2=27.937 df=9 P=0.001 respectively. Additionally, weather changes significantly associated with various food-types birds X2=55.011 df=15 P=0.001. More so, weather changes showed a significant relation on the presence of humans on dumpsites X2=13.968 df=6 P=0.030. Furthermore, changes of weather and highway traffic intensity associated significantly X2=15.804 df=6 P=0.015. Also, the aggregation of birds and their location at dumpsites associated significantly X2=17.528 df=12 P<0.05. More so, the aggregation of birds showed a significant relation on their activity X2=14.477 df=12 P<0.05. The study demonstrates that pied crows exhibit behavioral plasticity in their foraging strategies in response to seasonal changes in weather patterns. The increased utilization of waste materials during the dry weather suggests that these urban-adapted birds play an important role as scavengers in managing solid waste, especially in developing regions where waste management infrastructure may be limited. Understanding the relationship between weather changes and pied crow foraging behavior on waste materials is crucial for developing effective waste management strategies and mitigating the potential negative impacts of these urban-adapted birds on local ecosystems across Africa.
... It is estimated that as much as one-third of all food produced is wasted, likely ending up in landfills. 43 As it stands, global municipal waste is predicted to increase to 2.4 billion tons by 2050, more than double the current predictions for population growth. Thus, this phenomenon is set to keep growing. ...
... Nowadays, various species of gulls, corvids, squirrels, and bears, are known to be opportunistic or specialized exploiters of landfills as a new food resource. 43 A key question that has just started being investigated is what feeding on anthropogenic organic wastes means for the physiology of wildlife, and what the implications are for their life histories and, in broader terms, how it determines health outcomes. Free-living animals feeding on human waste have the advantage of predictable and abundant food resources that may help them to cope with seasonal harshness as shown in urban gray squirrels 44 (see also the metaanalysis by Chamberlain et al. 45 ). ...
Article
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Conventional physiological research has focused on elucidating the endogenous mechanisms that underly the adaptations of species to life in extreme habitats, such as polar regions or deserts. In this review article, we argue that even habitats that are not considered extremes are facing unpredictable, rapid, and strong modifications due to human activities that expose animals to novel extreme conditions. Thus, physiological research on these animals can offer insight on the role of physiological plasticity in driving their resilience and adaptation. To this end, we discuss how stress physiology (with a particular focus on oxidative stress) has a central role in mediating the interaction between the exposome (measure of all the environmental exposures of an individual in a lifetime) and cellular processes (bio‐exposome) in the contexts of relevant extreme anthropogenic changes to the habitat conditions. We also provide concrete examples on the relationship between oxidative stress and the bio‐exposome in free‐living animals, and how this research can be relevant to human health. Finally, we propose future research directions integrating the bio‐exposome and the One Health framework to achieve a holistic understanding of the proximate mechanisms underlying individual responses to extreme anthropogenic environmental changes.
... When resources are low, the mean group size may decrease to reduce competition for food within the group (Kifle & Bekele, 2022;Webber & Vander Wal, 2021). Food provisioning may alleviate these constraints, and having a predictable food source can buffer temporal and spatial variation in resources (Oro et al., 2013). Such circumstances can lead to increased local population densities, larger long-term group sizes and a higher likelihood of social contact (Oro et al., 2013). ...
... Food provisioning may alleviate these constraints, and having a predictable food source can buffer temporal and spatial variation in resources (Oro et al., 2013). Such circumstances can lead to increased local population densities, larger long-term group sizes and a higher likelihood of social contact (Oro et al., 2013). This may be especially true in harsh environments or food-limited seasons, with stronger effects of food provisioning on social behaviour in certain seasons, subsequently affecting the social structure of groups . ...
Article
Group living confers crucial survival and reproductive advantages for individuals, with group size, composition and resource availability affecting individual fitness, sociality and behaviour. Both sociodemographic and anthropogenic factors influence behaviour, with social organisation and individual characteristics shaping time budgets and affecting the distribution of affiliative and aggressive interactions. Cattle, Bos taurus, are social ungulates, but the majority of cattle research is conducted on farms and may not be an accurate representation of their more naturalistic social structures. We investigated the relationships between sociodemographic factors (sex, dominance and group size), anthropogenic factors (supplementary provisioning), and social behaviours in free-ranging, feral cattle. We analysed social relationships (dominance, affiliation, aggression, and global social network values) for cattle living in five mixed-sex groups (ranging from 9 to 63 animals per group). We found that more dominant cattle had more affiliative partners, performed allogrooming for longer, and performed more affiliation. Females received more affiliation than males, and males directed affiliation preferentially towards females, with 258 male-to-female interactions and 145 male-to-male interactions. Females performed less aggression in larger groups, and animals in provisioned groups received more aggression. Our results indicate that cattle group social organisation has important sex-specific effects on its members. These social dynamics highlight the importance of understanding the distribution of interactions in mixed-sex groups, and how sociodemographic factors can asymmetrically influence behaviour.
... usually come along with a surplus of predictable anthropogenic food sources, which are typically exploited by generalist wildlife species (Oro et al. 2013). Such urban exploiters (sensu McKinney 2006), adapted to the presence of humans, benefit from various anthropogenic sources of excess food, and thus thrive in urbanized areas (Kark et al. 2007;Angert et al. 2011). ...
... While we found no significant impact of cattle ranching on gazelles, our results showed that the provision of excess food for jackals and wild boar had substantial knock-on effects on the gazelle encounter rate. Through cascading effects, excess food can thus negatively impact avoider populations, and may eventually lead to a decline in species richness (Oro et al. 2013), which further highlights the complexity of conservation and management in peri-urban areas (Shafer 1995). Our study provided the rare opportunity to follow such a cascading process. ...
Article
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A major side effect of urbanization is the increased availability of food for wildlife in peri‐urban areas. Most research has focused on highly adaptive exploiter species that thrive under such conditions, overlooking avoider species, which are often predated upon by exploiters. Moreover, peri‐urban areas are often grazed by livestock, mainly to reduce the frequency and intensity of fires, a practice that can also adversely affect vulnerable wildlife species. We examined the long‐term effects of excess food provided to discourage exploiter species, namely golden jackal (Canis aureus) and wild boar (Sus scrofa), from foraging on farmland and in human residencies. Both species prey on endangered mountain gazelles (Gazella gazella) in our peri‐urban study area, which is nested within a mosaic of settlements and agricultural lands in Mediterranean Israel. Because the park is routinely subjected to seasonal cattle ranching, we included cattle stocking rate (mean ± SD: 51.77 ± 18.21 cow grazing days/ha) as an alternative factor, into our analysis. We used Generalized Linear Mixed Models to analyze an extensive dataset, comprising 724 surveys conducted over 17 years, and modeled gazelle encounter rates in response to excess food and cattle ranching, while controlling for environmental factors. Our results suggest that anthropogenic excess food through diversionary feeding led to decreasing gazelle densities, probably through increased predation by exploiter species. When diversionary feeding ceased after 12 years, gazelle encounter rates increased. We argue that this increase corresponds to population recovery, although it could be consistent with alternative mechanisms such as altered space‐use and movement patterns. To conserve vulnerable and endangered wildlife species in urban and peri‐urban areas, managers should reduce the availability of anthropogenic food for predators and scavengers. Furthermore, moderate cattle ranching (i.e., seasonal with low stocking rates) could mitigate potential adverse impacts of cattle ranching on mountain gazelle populations.
... Compreender como a urbanização afeta a dimensão trófica dos nichos de espécies é relevante tanto do ponto de vista evolutivo como ecológico (Felice et al. 2019;Oro et al. 2013). No entanto, apesar do aumento previsto da população urbana em todo o mundo (Seto et al. 2010(Seto et al. , 2012(Seto et al. , 2013 United Nations 2023) e das conhecidas implicações ambientais globais do processo de urbanização (Jägerbrand & Spoelstra 2023;McKinney 2006), esta questão ainda está em aberto. ...
... No entanto, as cidades ainda abrigam uma gama de animais menos restritos em suas dimensões de nicho, e que podem até incorporar recursos antropogênicos em sua dieta(Athreya et al. 2013;Johnson et al. 2015;Murray et al. 2015;Plummer et al. 2015), fatores que são importantes para explicar a sua sobrevivência em ambientes urbanos(Møller 2009). Esses recursos antropogênicos podem ser disponibilizados indiretamente à fauna por meio do plantio de plantas exóticas, criação de animais domésticos(Athreya et al. 2013;Braczkowski et al. 2018;Zietsman et al. 2019), alimentos para animais de estimação e restos de dejetos humanos(Murray et al. 2016;Newsome et al. 2015;Oro et al. 2013;Plaza et al. 2019), ou diretamente fornecendo alimentos através de comedouros(Plummer et al. 2019). Compreender as necessidades alimentares das espécies é crucial, principalmente porque é um dos principais elementos que caracterizam o seu nicho ecológico e estruturam as comunidades locais(Lovette & Fitzpatrick 2016;MacArthur & Pianka 1966;Tilman 1982). ...
Thesis
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Paisagens urbanas são cada vez mais dominantes ao redor do mundo criando uma nova interface para a fauna silvestre. Apesar de ter sido ignorado por muito tempo pelos ecólogos, o entendimento dos processos em áreas urbanas recebe crescente atenção para a construção de um arcabouço atual de desenvolvimento sustentável e conservação da biodiversidade. Assim, é preciso explorar de forma detalhada como as diferentes características de áreas urbanas filtram espécies e selecionam características da fauna silvestre. Neste sentido, esta tese se propôs, utilizando espécies de aves silvestres no Distrito Federal (DF) como um modelo, a estudar a relação da expansão e intensificação urbana. O objetivo geral foi investigar as assembleias de aves urbanas e sua relação com o processo de urbanização. Pretendo entender como a urbanização afeta os indivíduos que nela persistem, avaliando sua morfologia, saúde e o uso dos recursos alimentares. Também discorro sobre adaptações metodológicas realizadas em decorrência das dificuldades da amostragem de aves nos ambientes urbanos. A tese está estruturada em oito capítulos interligados pelo tipo de ambiente explorado durante o estudo: ambientes urbanos. Esses capítulos utilizam diferentes abordagens e tem distintos objetivos. Apesar disso, todo o direcionamento do trabalho está focado nos impactos que a urbanização provoca na fauna em seus diferentes aspectos (em nível de comunidade ou de população) e os determinantes ambientais relevantes para os animais que nela vivem. Além disso, em alguns capítulos abordo questões metodológicas, tendo em vista as dificuldades de amostragem de aves nos ambientes urbanos. Por último, apresento um capítulo compilando o conhecimento atual sobre os ambientes urbanos em forma de um texto de divulgação científica para a população, que incorpora meus achados nos ambientes urbanos de Brasília. Meus resultados mostram que as áreas urbanas impactam de forma direta as aves, tanto em nível de comunidade como em nível das populações. Em nível de comunidades, observei clara redução da diversidade (taxonômica, filogenética e funcional) e mudança da estrutura da comunidade em área com maior intensidade urbana. Em nível d populações, observei um aumento da proliferação de doenças (lesões nas patas), aumento do estresse crônico (razão H/L), e mudanças morfológicas e alimentares. Esses achados confirmam minha hipótese inicial de que as áreas urbanas promovem pressões significativas sobre as espécies, afetando os animais que nela persistem. Meus achados são relevantes pois o entendimento de como as espécies lidam com as pressões ambientais causadas pelas modificações urbanas podem ajudar gestores a tornar as cidades mais amigáveis à fauna, principalmente quando pensamos nos desafios globais de manutenção das populações nativas que estão em declínio.
... In our area, rabbits are also important prey for non-breeding individuals (Blanco 1997), which may be attracted to the general area also by the large concentration of organic waste remains provided by rubbish dumps. The latter represents a predictable, concentrated resource whose importance for kites and other species is well known, especially for younger, inexperienced individuals that may have trouble capturing more difficult live prey and thus frequently congregate in large numbers at landfills or other sites with substantial human subsidies (e.g., De Giacomo and Guerrieri 2008; Oro et al. 2013;Plaza and Lambertucci 2017;Vicente-Hernández et al. 2023). In turn, the formation and rapid growth of a very large congregation of non-breeding individuals (up to over 10,000 floaters) probably acted as a major magnet for the settlement of immigrant breeders, many of which may have been even directly recruited from the nearby crowd of floaters. ...
... This stresses the need to monitor and assess the status of wide-ranging mobile species at large-enough spatial and demographic scales. Anthropogenic subsidies from landfills can be important to sustain some species, but are often accompanied by hidden costs and their role is controversial (Oro et al. 2013;Plaza and Lambertucci 2017). Here, we show how they can act as traps, especially for social or semi-social species, which can gather in large numbers, thus triggering "attraction spirals" conducive to maladaptive sinks. ...
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Accurate identification of decreasing trends is a prerequisite for successful conservation, but can be challenging when immigration compensates local declines in abundance. Here, we show that a potential declining trend driven by low vital rates was overridden and converted into a spectacular increase by massive immigration into the population of a semi-social raptor, the black kite Milvus migrans, breeding in a highly contaminated area near a major landfill. Immigration was promoted by a growing food-base of live prey, coupled with the attraction exerted by the progressive gathering of a large flock of non-breeders at the area, resulting in an “attraction spiral” that lured large numbers of breeders to settle into a contaminated population incapable of self-sustenance. Immigration was so prevalent that, in little more than a decade, over 95% of the original population was substituted by immigrants, which showed the enormous potential of immigration as a rescue mechanism. At the same time, immigration may hide cryptic threats, as shown here, and expose some species, especially group-living mobile ones, to rapid attraction to anthropogenic subsidies, whose potential role as evolutionary traps is well known. The dynamics exposed here may become increasingly common, affecting many other species in our growingly anthropogenic world. Our results remark the often overlooked importance of immigration in ecology, evolution, and conservation as a key player for population dynamics and their more realistic forecast.
... This can involve voluntary feeding in residential neighborhoods, temples, or wildlife tourism areas, as well as inadvertent provisioning from farms, plantations, and waste food dumps. Provisioned food is typically high in calories, easily digestible, and more predictable than natural resources, impacting wildlife at both individual and population levels (Oro et al. 2013). This practice, prevalent in many Asian countries and particularly in India, affects primate behavior, leading to changes in growth, reproduction, foraging habits, and social dynamics (Oro et al. 2013;Sengupta et al. 2015). ...
... Provisioned food is typically high in calories, easily digestible, and more predictable than natural resources, impacting wildlife at both individual and population levels (Oro et al. 2013). This practice, prevalent in many Asian countries and particularly in India, affects primate behavior, leading to changes in growth, reproduction, foraging habits, and social dynamics (Oro et al. 2013;Sengupta et al. 2015). Roads along the wildlife habitats are major provisioning spots (Sengupta and Radhakrishna 2018;Riley et al. 2021;Ilham 2023) which can elevate the chances of disease transmission and primate road kills (Ilham 2023;Praill et al. 2023). ...
Article
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Human-dominated landscapes and structures such as roads are known to facilitate human interactions with wildlife, especially with non-human primates. One significant interaction is food provisioning along roads in wildlife habitats, which impacts the behavior, ecology, and health of wild animals. The genus Macaca is well known for such interactions, being highly adaptive and flexible to anthropogenic situations. Such interactions can have serious consequences for the long-term survival of endangered habitat specialists such as lion-tailed macaques (LTM: Macaca silenus), endemic to the Western Ghats of India. In this study, we identified and confirmed provisioning and habituation of LTMs along roads and plantations in eight landscapes, through road surveys, media and social media reports, published research papers, and interactions with various stakeholders. The locations were the Anamalai range, Nelliyampathy, Sholayar, Nadugani, Sabarimala, Gavi, Vellimalai, and the Agumbe Hills. The intensity and frequency of interactions vary across these locations. Overall, about 25% of the population in these landscapes interacts with humans, representing approximately 11% of the estimated total population of LTMs in the Western Ghats. On the basis of long-term scientific data available from the Puthuthottam population, we have used this area as a case study for the development of LTM-human interactions. Immediate interventions to reduce these interactions and further research are recommended to understand the causes of increasing interactions between humans and LTMs.
... However, cities still harbor a range of animals that are less restricted in their niche dimensions, and that can even incorporate anthropogenic resources into their diet (Athreya et al. 2013;Johnson et al. 2015;Murray et al. 2015;Plummer et al. 2015), factors that are important in explaining their survival in urban environments (Møller 2009). These anthropogenic resources can be made available to fauna indirectly through the planting of exotic plants, domestic animal husbandry (Chamberlain et al. 2009;Athreya et al. 2013;Narango et al. 2017Narango et al. , 2018Braczkowski et al. 2018;Zietsman et al. 2019), untended pet food and human waste remains (Oro et al. 2013;Newsome et al. 2015a;Murray et al. 2016;Plaza et al. 2019), or directly by providing food through feeders (Galbraith et al. 2015;Plummer et al. 2019). Understanding the food requirements of species is crucial, mainly because it is one of the main elements that characterize their ecological niche and structure local communities (MacArthur and Pianka 1966;Tilman 1982;Lovette and Fitzpatrick 2016). ...
... Understanding how urbanization affects the trophic dimension of species niches is relevant from both evolutionary and ecological points of view (Oro et al. 2013;Felice et al. 2019). However, despite the projected increase in urban population worldwide (Seto et al. 2010(Seto et al. , 2012(Seto et al. , 2013United Nations 2023) and the known global environmental implications of the urbanization process (McKinney 2006;Jägerbrand and Spoelstra 2023), this is still an open question. ...
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Among the many changes associated with the urbanization process, changes in resource availability can directly impact local wildlife populations. Urban areas suppress native vegetation and convert natural environments into impervious surfaces, modifying the composition and quantity of available food resources. Understanding the food requirements of species is crucial, mainly because it is one of the main elements that characterize their ecological niche and structure local communities. Our aim in this study was to assess the impact of urbanization intensity on the isotopic niche space of birds commonly found in urban areas of Brasília, the capital of Brazil, a big city in central Brazil with approximately 3 million inhabitants. By analyzing the δ¹³C and δ¹⁵N isotopic metrics of feathers from bird species found along a gradient of urbanization intensity, we evidenced a simplification but not a displacement of the bird assembly isotopic space due to urban intensification. Bird assemblage access similar food resources in the higher urban intensification areas, although less diversified than in lower urban intensification areas. In most cases, the response to urban intensification is more specific than convergent among guild members. The studied species maintain themselves in highly intensified urban areas by restricting, changing, and expanding their access to resources. The trophic dimension is one of the key components of the species' ecological niche, and understanding the urban intensification impacts on this dimension is essential for maintaining biodiversity and ecosystem services in cities.
... Due to anthropogenic changes, such as changes in land use or species management, some species have become vulnerable to extinction, while others have become highly abundant (Batt 1997;Jefferies et al. 2004;Allombert et al. 2005;Castro et al. 2005;Rotem et al. 2011;Oro et al. 2013). Such highly abundant species may come into conflict with humans when more intensely interfering with human interests (Marzano et al. 2013;Stroud et al. 2017) and may have a large impact on other species (Jefferies et al. 2006;Latham et al. 2011), either negatively, through for instance resource competition, or positively through facilitation (van der Wal et al. 2000;Arsenault and Owen-Smith 2002;Stahl et al. 2006). ...
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Human-wildlife conflicts are generally tackled using single-species studies and ensuing management solutions, ignoring species interactions that may moderate or augment these issues. We investigate the effects of interactions between four goose species foraging in the province of Friesland, the Netherlands, on species distributions, energetics, and consequent economic costs of agricultural damages and management, using an individual-based model. In Friesland, geese are allowed to graze on (semi-)natural grasslands and selected agricultural grasslands (accommodation areas), while they are scared off other agricultural grasslands (scaring areas). We show that interspecific competition and facilitation drive spatial redistribution of goose species. With increasing population sizes, most species are forced to increase foraging in the scaring areas, leading to more scaring events and more additional foraging to compensate for energy spent on fleeing behaviour. Our modelling results underline that careful consideration should be given to how management may affect the spatial distribution of foraging geese.
... Wildlife feeding often occurs outside controlled contexts through unregulated tourist attractions, whereby wildlife may be attracted because of incidental provisioning activities, such as dumps or fishing discards (Oro et al. 2013), after which the public takes notice and begin feeding the animals to lure them closer. In these contexts, there are considerable risks to animal and human welfare because of a lack of codes of conduct guiding appropriate human behaviour or education around the risks (Healy et al. 2020). ...
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Context Food provisioning is widely used in elasmobranch tourism to elicit encounters between tourists and these typically elusive species. Wildlife tourism operations usually target a single species, although behavioural responses of these species often differ among provisioning locations. Likewise, provisioned foods are often consumed by multiple non-target species, which may also differ in their behavioural responses despite being exposed to the same provisioning event. Few studies have compared behaviour and movement patterns of multiple species in response to provisioning, particularly of those occupying similar niches. Aims This study aimed to compare the movement patterns of two sympatric ray species, the smooth stingray (Bathythosia brevicaudata) and the southern eagle ray (Myliobatis tenuicaudatus), around a site where they are fed as part of an unregulated but popular tourist attraction in south-eastern Australia. Methods Using passive acoustic telemetry, we compared the presence, duration of visits, and space use around the provisioning site for the two ray species. Key results Both species responded to provisioning at the site, but in different ways, suggesting different temporal use of the provisioning site (i.e. time-sharing). Southern eagle rays exhibited stronger attachment to the site, potentially indicating habituation to regular provisioning and a greater risk of being negatively affected than were smooth stingrays. Conversely, smooth stingrays appeared to focus their use of the site on periods of higher provisioning activity (i.e. daytime and on weekends) and may temporarily displace the smaller eagle rays during these times. Despite their attachment, both species made movements out of the study area, suggesting limited impacts on broader-scale behaviours. Conclusions Smooth stingrays and southern eagle rays exhibited distinct temporal patterns of site use in response to food provisioning, reflecting differences in their behavioural responses. These patterns suggest that even closely related and co-occurring species may adopt different approaches to accessing the same anthropogenic resource. Implications This research has highlighted the need for a broader approach to assessing and managing wildlife provisioning activities, that takes into account species-specific responses and interspecific interactions.
... Urban organic waste accumulating in landfills provides a spatially and temporally predictable food source for many vertebrates, especially facultative avian scavengers (Plaza and Lambertucci, 2017), particularly when natural food resources are scarce (Oro et al., 2013;Gilbert et al., 2016). Landfills often serve as important foraging grounds for inexperienced individuals, such as juveniles or non-territorial birds (i.e., floaters) (Turrin et al., 2015;Vicente-Hernández et al., 2023) and function as stopover sites for migratory birds (Blanco, 1994(Blanco, , 1996. ...
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Bird-aircraft collisions pose serious safety risks and economic costs, especially near urban areas where landfills attract large numbers of foraging birds. Madrid, home to four airports and Europe's largest known seasonal concentrations of black kites (Milvus migrans) near a major landfill, represents as a potential conflict zone. This study tracked 15 non-breeding black kites using GPS telemetry over three years to evaluate whether their movements compromise aviation safety. Results revealed a strong preference for roosting sites and adjacent landfills, while airports and their surroundings (1, 8 and 13 km buffers) were largely avoided. Flights over airports were infrequent and mostly over the largest airport, likely due to its size and nearby habitat with abundant wild prey. Airport use peak in June, coinciding with maximum numbers of highly mobile immatures and non-breeders (floaters), with midday being the most active period. Use of the study area -including airports and their surroundings-decreased as birds aged. Although black kites were the most frequently recorded species in bird strike incidents at Madrid airports, collisions were low relative to their high local abundance, suggesting a lower-than-expected collision frequency. Nonetheless, targeted habitat management such as reducing prey availability near airports could further mitigate risks posed by black kites and other larger, more hazardous species. This study highlights the value of tracking animal movements to address and solve human-wildlife conflicts in critical infrastructure areas.
... These suboptimal habitats are also prone to biological invasions, frequent human disturbances (Perera 2001), and extractions (Chokkalingam et al. 2001) that may alter critical habitat structure, rendering them less suitable for conservation-dependent agamids. Subsidized predation by human commensals or competition against disturbance-tolerant generalists can also challenge long-term persistence of sensitive agamid species (Oro et al. 2013). Nonetheless, with sustainable management actions, these suboptimal habitats can offer opportunities to promote conservation. ...
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Sri Lanka's unique agamid lizards, many restricted to this tropical island nation, face threats from habitat loss and climate change. To protect these endangered reptiles, we implemented a machine‐learning approach, species distribution modeling to map their habitat suitability and identify priority conservation areas. Focusing on 14 threatened species and their known species‐presence information, we combined numerous bio‐climatic environmental predictors and forest cover to predict their spatial distribution in Sri Lanka based on habitat suitability. Results revealed that while all species have some habitat in protected zones like Sinharaja Forest Reserve, the Central Highlands and the Knuckles Range, over 40% of their most critical habitats remain unprotected. These unprotected areas, often in high‐elevation forests of the Central Highlands and Knuckles Mountain Range, are vital for species with tiny ranges. The research also highlighted that some human‐modified landscapes, like agroforests, could support conservation if managed sustainably. By pinpointing gaps in Sri Lanka's current network of protected areas, this study provides a roadmap for expanding the country's conservation network. The methods used here, particularly the modeling approach, could help protect other poorly studied species worldwide, ensuring limited resources target the most urgent needs. Practitioner Points ∘ Species distribution modeling (SDM) is a powerful tool for identifying conservation gaps/hotpots, including unprotected critical habitats, even for species with limited data, guiding targeted conservation actions. ∘ Prioritize wet and montane zones: Key conservation lands like Sinharaja Forest, the Knuckles Range, and Central Highlands require expanded and enhanced protection and habitat connectivity to safeguard Ceylonese endemic agamids. ∘ Integrate human‐modified landscapes: Secondary forests and agroforests can complement protected areas if restored and managed to support biodiversity, offering a buffer against habitat loss.
... fruit and nut trees), urban habitats provide predictable food resources for wildlife, either directly (i.e. through bird feeders) or unintentionally via accidental feeding of wildlife (i.e. garbage or composts) (Oro et al. 2013;Plaza and Lambertucci 2017;Hansen et al. 2020;Rimbach et al. 2023). Cities provide not only predictable food sources, but also reliable water resources and shelter in anthropogenic structures, which might contribute to the maintenance of small mammal populations and could be one explanation for the absence of patterns in species diversity along the urbanization gradient. ...
Article
Context Urbanization is a global phenomenon with profound forms of land-use change. Urban areas are characterized by habitat fragmentation and replacement of natural habitat by human-made structures, which alter environmental conditions such as natural resources, light and noise levels, and ambient temperature. Animal communities respond to urbanization in various ways, often showing shifts towards generalist species and declines in species richness. However, mixed results are found in the literature, with neutral or even positive effects on species diversity. Aims Our goal was to investigate whether community composition, species diversity and evenness of terrestrial small mammals vary with increasing levels of urbanization, approximated as impervious surface cover and human population density. Methods We conducted a camera trap survey in 33 gardens in the city of Münster, Germany, and its surroundings. We recorded a total of 25,982 photos with animals (excluding pets). For analysis, we included only photos of the same species captured at least 60 s apart, resulting in a final dataset of 7090 photos. Key results Eight taxa were recorded, with Apodemus spp. dominating (72.6%). The probability of occurrence of all species was not affected by increasing impervious surface cover. We found that community composition, species diversity and evenness do not vary with changing impervious surface cover or human population density. Although associations among species were mostly neutral, trends included a positive association between Myodes glareolus and Crocidura spp., and negative associations between Apodemus spp. and Crocidura spp., and Rattus norvegicus and Sciurus vulgaris. Conclusions Our results suggest that composition, species diversity and evenness of this small mammal community are not affected by the two measures of degree of urbanization, impervious surface cover and human population density. The small mammal community of Münster is likely to be the result of generalist species expressing high phenotypic plasticity to bypass the urban filters explaining our overall neutral results. Implications Urban gardens can harbor a small mammal community as diverse as gardens outside of the city, highlighting the importance of these green areas in the urban matrix. Further studies will be needed to address whether our findings are generalizable to multiple cities in Europe.
... and implications for ecosystem health (Moleón Sanchez-Zapata, Margalida, et al. 2014). Removal of organic waste has emerged as a globally important ecosystem service (Costanza et al. 1997), as humans discard large quantities of animal carcasses (Oro et al. 2013;Mateo-Tomás et al. 2015). Obligate vertebrate scavengers, such as vultures, are recognised as important contributors to carcass removal and associated ecosystem services (Markandya et al. 2008;Moleón Sánchez-Zapata, Selva, et al. 2014). ...
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Slaughterhouses in The Gambia serve as critical feeding sites for diverse vertebrate scavenger communities, including hooded vultures, domestic dogs, pigs and avian species such as pied crows, black kites and cattle egrets. This study investigated how the quantity and type of organic waste influence the composition and competitive interactions of scavengers across five slaughterhouses. Using multivariate statistical models, we found that waste quantity was the strongest predictor of scavenger community composition, explaining 32.7% of the variation, with hooded vultures being most abundant at high‐waste sites. Specific waste types influenced feeding behaviour, suggesting niche differentiation among species; for instance, cattle egrets focused on blood and insects, while vultures dominated meat‐based resources. Competitive interactions varied by species, with domestic dogs frequently displacing vultures without physical conflict, whereas hooded vultures dominated interactions against other birds. Activity patterns revealed temporal separation, with vultures and dogs active primarily in the morning, and other avian scavengers more active in the afternoon, reducing interspecific competition. The study highlights the essential role of hooded vultures in waste management and disease mitigation but also emphasises how poor fencing facilitates mammalian access, intensifying competition and potentially threatening obligate scavengers. Improving fencing, controlling feeding, and incorporating targeted waste management strategies are recommended to support scavenger conservation and enhance ecosystem services in urbanised environments.
... In our study system, human modi cation is related to agricultural and exurban areas that see increased human presence in the evening. These areas also contain valuable food resources (Oro et al. 2013, Kennedy et al. 2019, which may prompt deer to forage in these areas during the day but move away to avoid periods of elevated risk at night. This interpretation is further supported by the fact that deer, particularly females, selected for human modi cation most strongly from January to April when food was most scarce but avoided human modi cation most strongly during hunting season when humans pose the greatest risk. ...
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Background Behavioral responses of prey to predation risk have ecological impacts that can be as great as direct mortality. Risk response involves either behavioral changes or spatial avoidance, but it is not clear how prey decide between these strategies. Theory often suggests that prey pair responses to risks based on the hunting mode of the prey (hunting mode hypothesis), but prey may ignore hunting mode to prioritize responding to the most lethal predators (lethality hypothesis). Furthermore, prey may respond to the spatial distribution of these risks (risky places hypothesis) or respond only during the periods of highest risk (risky times hypothesis). Methods To test these hypotheses, we evaluated the behavioral responses of white-tailed deer (Odocoileus virginianus) to risks from two natural mesopredators and human sources of mortality. Specifically, we determined, for each source of risk, whether deer responded with behavioral state changes or spatial avoidance and whether this behavior changed with time (diurnally and annually). We collared and tracked 40 female and 29 male deer. To determine the response of deer to risk, we collected data on the distribution of coyotes (Canis latrans), bobcats (Lynx rufus), human modification, hunters, and roads. We used hidden Markov models (HMM) to determine whether each covariate impacted the probability of transitioning between behavioral states and selection functions (SSF) to determine whether deer spatially avoided each covariate. Results Generally, deer changed behavioral state in response to both mesopredators but avoided human modification. In response to mesopredators, deer consistently shifted to slower movement behavioral states. Spatial responses to human modification varied depending on the time of day. During daylight hours, deer selected for human modification, but during the crepuscular and nighttime period, deer avoided human modification. Conclusions Space use was most strongly related to more lethal humans, providing support for the lethality hypothesis. Despite prioritizing humans, mesopredators impacted behavioral state, suggesting that mesopredators still have important impacts on prey behavior. Finally, temporal patterns of avoidance align with other studies that indicate avoidance of predators is time-dependent, but further highlight the complex push-pull relationship of human modified areas on wildlife.
... The ecological impacts of these changes go beyond the evident habitat transformation and destruction, and can have more subtly effects, such as the use of part of agricultural production as food subsidies to feed wildlife and even endangered species either directly or indirectly through remains of intensively kept livestock (Apollonio et al., 2010;Penteriani et al., 2021, Mohammadi et al., 2019, Ć irović, and Penezić, 2020, Ciucci et al., 2020. The consequences of these actions are not negligible as food supplies may alter the species' feeding preferences and, at the end, the structure and functionality of guilds and trophic webs (Strong et al., 2010;Oro et al., 2013). ...
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The rise of intensive livestock farming poses a significant global threat to biodiversity, affecting scavenger species reliant on carcasses from these operations. Assessing avian scavenger dependence on such resources in human-modified environments is challenging using conventional methods. This study analyzes GPS-tracking and stable isotopes of 77 Eurasian griffon vultures (Gyps fulvus) in the Iberian Peninsula to explore variations in resource consumption. By means of Bayesian isotopic mixing models we examined the influence of home range size, degree of human transformation of landscapes, and individual characteristics on diet. Elevated δ 13 C levels indicate pig consumption, likely due to their reliance on corn-derived feed supplements. Populations in areas with higher Human Footprint Index, like the Ebro Valley, showed utilization of variated livestock resources (sheep and pig), broadening population trophic niches and individual heterogeneity. Conversely, in populations of less transformed (natural) environments, like the Cazorla Mountains, focal birds relied almost exclusively on extensive or semi-extensive sheep farming, with diet variations linked to home range size changes. Finally, the Cádiz mountains population heavily depended on pig remains, likely from vulture feeding stations and farms. We detected sex differences in diet probably linked to asymmetric behavioural responses between males and females to local changes in resource abundance and predictability. These findings demonstrate that Iberian griffon vulture populations heavily rely on intensive livestock from farming and supplementary feeding schemes, sometimes violating regional and European regulations. This dependence threatens individual health and population viability due to ingestion of veterinary drugs, pollutants, and direct mortality from infrastructure accidents , especially in humanized areas. Stable isotopes prove valuable in assessing the real avian scavengers' reliance on carrion resources on a broad scale, surpassing estimates from widely-used methods.
... Anthropogenic effects on the environment, such as habitat loss and degradation, often alter the abundance and quality of food resources (Civitello et al., 2018;Oro et al., 2013;Robb et al., 2008). These changes in resources can impact disease dynamics in complicated ways. ...
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Resource quality can have conflicting effects on host–parasite interactions; for example, higher resource quality might increase host investment in immune function, or conversely, might permit greater parasite reproduction. Thus, anticipating the impact of changing resource quality on host–parasite interactions is challenging, especially because we often lack a mechanistic understanding of how resource quality influences host physiology and fitness to alter infection outcomes. We investigated whether there are generalizations in how resource quality affects multiple host clones' interactions with different parasites. We used the Daphnia freshwater zooplankton model system to experimentally investigate how a resource quality gradient from high‐quality green algae to poor‐quality cyanobacteria diets influences host fitness, physiology, and infection by two parasites: a bacterium, Pasteuria ramosa, and a fungus, Metschnikowia bicuspidata. We ran a separate experiment for each parasite using a factorial design with four diets, two Daphnia dentifera host clones, and parasite‐inoculated and ‐uninoculated treatments (16 treatments per experiment). Diet strongly influenced infection by the fungus but not the bacterium. These relationships between diet and infection cannot be explained by changes in feeding rate (and, therefore, parasite exposure). Instead, the impact of diet on fungal infection was associated with impacts of diet on the earliest stage of infection: hosts that fed on poor quality diets had very few attacking spores in their guts. Diet did not significantly influence host immune responses. Diet influenced spore production differently for the two parasites, with reduced resource quality limiting the number of fungal spores and the size (but not number) of bacterial spores. Diet, host clone, and infection all affected host fitness. Interestingly, diet influenced the impact of the bacterium, a parasitic castrator that induces gigantism; for one clone, infected hosts fed high‐quality diets still produced a substantial number of offspring, whereas resource limitation hindered gigantism. Finally, there were often costs of resisting infection, though these generally were not affected by diet. Overall, we show that resource quality differentially impacts the exposure, infection, and proliferation processes for different parasites and host clones, which highlights the need to use multi‐genotype and multi‐parasite studies to better understand these complex interactions.
... This may reflect a dietary focus on anthropogenic prey (i.e., exotic or human-associated species) with stronger C 4 signals (Jahren et al. 2008;Gámez et al. 2022) that do well in the hot, dry summer months because of access to watered and fertilized gardens and urban greenbelt areas (Newsome et al. 2015b;Suri et al. 2017). Together these findings suggest that reliance on anthropogenic subsidies around cities may vary temporally, with implications for ecosystems, communities and trophic interactions through altering processes like competition, predator-prey interactions, as well as nutrient transfer within and between biotopes (Oro et al. 2013;Newsome et al. 2015b). ...
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Urbanisation critically alters the availability of resources and the nature of risks for wildlife by fragmenting natural habitats and disrupting ecosystems. Despite these challenges, carnivores frequently persist in and around urban environments, where novel opportunities, such as anthropogenic food, may outweigh associated ecological risks. Here, we investigate the responses of an urban adapter to novel resources, using stable isotope analysis of vibrissae (whiskers) to understand the spatiotemporal foraging patterns of caracals (Caracal caracal) on the fringes of the city of Cape Town, South Africa. Caracals are medium‐sized felids and the largest remaining predators on the Cape Peninsula. Using isotopic niche metrics and home range estimates, we assess the effects of demographics, seasonality, and urbanisation on variation in individual foraging behaviour from GPS‐collar monitored caracals (n = 28) across an urban gradient. Despite a wide isotopic niche at the population level, we observed high levels of individual specialisation. Adult and male niches were wider, likely due to larger home ranges, which facilitate the exploitation of diverse prey across trophic levels. Patterns in δ¹³C were seasonal, with increases during the warmer, drier summer months across the Peninsula irrespective of habitat use. Taken together with niche contraction for caracals in urban areas, our findings suggest higher reliance on human‐subsidised resources in summer. Caracals using areas dominated by wildland cover had higher δ¹⁵N values and larger niches than those using urban‐dominated areas. Across the study area, δ¹⁵N values varied spatially, with increased enrichment in caracals using more coastal and wetland areas and prey, particularly in winter. Individual foraging flexibility in caracal is clearly a key strategy for their success in this rapidly transforming landscape. Understanding spatiotemporal shifts in dietary niche and trophic ecology in adaptable urban carnivores, like the Cape Peninsula caracals, is fundamental for understanding the ecological needs of wildlife in and around rapidly growing cities.
... Another important but non-intuitive driver of fragmentation is behavioural change in animals within human-dominated landscapes (see also Chapters 9 and 14). The mechanisms leading to such behavioural changes may vary from behavioural flexibility to anthropogenic selection on behaviour (Swaddle 2016), but regardless of the mechanism, the utilization of anthropogenic resources and the ensuing higher exposure of wildlife to humans may lead to various behavioural modifications, such as reduced anti-predatory behaviours Geffroy et al. 2020), increased dependence on anthropogenic resources ( Oro et al. 2013;Hulme-Beaman et al. 2016), and reduced dispersal (Evans et al. 2012;Berger-Tal and Saltz 2019). Such local adaptations may create behavioural barriers between urban-adapted populations and rural populations of the same species, even when these populations are geographically adjacent. ...
Chapter
Human activities pose existential challenges to wildlife and ecosystems everywhere. In many species, behavioural adjustments are often the first responses when environments are altered. But how can an understanding of such responses—and knowledge of animal behaviour more generally—contribute to solving real-world problems? This book focuses on the many challenges facing wildlife and their habitats, and how a deeper understanding of animal behaviour can be used to predict and mitigate the anthropogenic impacts. The book is organised into two parts. Part 1 focusses on the myriad of environmental challenges that are affecting wildlife, the many ways in which behavioural responses to these challenges can be used to contribute to our understanding of the wildlife and environmental impacts, as well as potential solutions and interventions for addressing them. Part 2 extends upon these themes by examining how application of behavioural knowledge can contribute to better practical outcomes for wildlife conservation and management, animal welfare, the control of pests and diseases, and even improvements to the health, security and well-being of human society. It concludes with a synthesis of the key themes and lessons for shaping the discipline so that it is better equipped to address the many challenges that the world is facing, both now and into the future— and to elevate the application of behavioural knowledge to the next level of efficacy for real-world benefits.
... Inputs of angling baits in freshwater ecosystems are a source of human subsidies (Oro et al. 2013), but knowledge of ecological impacts on ecosystems is limited. In Lake Balaton (Hungary), annual nutrient inputs from ground baiting (16.3 t of N and 5.2 t of P) were 0.7% of total annual N and 3.2% of total annual P loads of the lake (Boros, Mozsár, and Specziár 2022). ...
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Recreational anglers use ground baiting to attract fish and increase catch inputs organic matter that can have important effects on water quality by increasing eutrophication. However, nutrient inputs from angling bait by recreational fisheries have not yet been estimated. We quantified nutrient inputs from angling baits in small lakes supporting specialized carp, put-and-take, and specialized roach recreational fisheries with a 2-year field survey of angling activity and in-person angler questionnaires. Angling activity was highly variable among recreational fisheries and averaged 82 (±74 SD) angler-day/ha/year in lakes with specialized carp fisheries, 145 (±80) in lakes with put-and-take fisheries, and 36 (±18) in lakes with specialized roach fisheries. Angling activity also differed temporally among recreational fisheries, with high angling activity in spring and summer for specialized carp and specialized roach fisheries, and in autumn and winter for put-and-take fisheries. The type and amount of baits used by anglers strongly differed among recreational fisheries, with specialized carp anglers using boilies (2.5 ± 1.5 SD kg/angler/ day) and seeds (2.1 ± 1.9 kg/angler/day), put-and-take anglers using exclusively pellets (0.39 ± 0.15 kg/angler/day), and specialized roach anglers using ground baits (0.72 ± 0.36 kg/angler/day). Nutrient inputs from angling baits were highly variable among recreational fisheries and ranged from 0.5 (±0.2 SD) kg/ha/year of nitrogen and 0.1 (±0.0) kg/ha/year of phosphorus in specialized roach fisheries to 10.2 (±9.3) kg/ha/year of nitrogen and 1.6 (±1.5) kg/ha/year of phosphorus in specialized carp fisheries. Our findings revealed that ecological consequences of ground baiting differed among recreational fisheries, which should be useful for developing fishery-specific regulations to efficiently manage ground baiting.
... Wildlife can benefit greatly from living in cities but also face many consequences. Urban areas provide year-round anthropogenic food sources and green spaces that benefit wildlife (Bateman and Fleming 2012, Lowry et al. 2013, Oro et al. 2013. They also offer refuge from large predators such as wolves Canis lupus, mountain lions Puma concolor, and bears (Ursus spp.), which typically avoid urban areas (Bateman andFleming 2012, Nicholson et al. 2014), although exceptions exist Berger 2003, Riley et al. 2021). ...
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As urbanization increases, wildlife increasingly encounters people. Coyotes Canis latrans and red foxes Vulpes vulpes are two canid species that have readily adapted to urban environments. Citizen science has emerged as a low‐cost method of collecting data on urban‐adapted species that can benefit management agencies but may provide different results than traditional methods. We analyzed data collected by citizen scientists and via motion‐triggered camera traps to see how each related to the anthropogenic features of distance to roads, building density, and median household income and the natural feature of distance to water. We also investigated the potential benefits of advertising the citizen science project on social media. We used occupancy models to analyze data from a grid of 67 cameras across Wichita, Kansas, USA, from March 2023 to February 2024. We used generalized linear models to evaluate data collected simultaneously from a website we created and advertised on social media where members of the public could report sightings of urban canids. The camera‐trap occupancy models suggested that red fox occurrence was only related positively to building density and coyote occurrence was related negatively to building density and positively to income. The citizen science models suggested that sighting reports of both species were more likely closer to roads, at intermediate building densities, and in high income neighborhoods. Coyotes and red foxes were both most likely to be detected by people during crepuscular periods but most likely to be detected by cameras at night. We also found that advertisements increased sighting reports and generated six times as much revenue for the wildlife agency than was spent. Our study suggests that citizen science data differ from camera‐trap data by tracking human activity patterns and distribution, but citizen science projects can provide other benefits such as generating interest in and revenue for management agencies.
... The learning behavior observed in scouts, parallels observations in other social organisms. For instance, honeybees navigating predictable floral landscapes [42,43], seabirds exploiting consistent food subsidies [44], flocking birds following established migratory routes [45], and wolves hunting within familiar territories [46] all demonstrate how the ability to anticipate resource locations can significantly enhance collective foraging efficiency. ...
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Liquid brains conceptualize living systems operating without central control, where collective outcomes emerge from local but dynamic interactions. Therefore, movement is expected to shape the connectivity among individuals, allowing the system to optimize its efficiency. We empirically measured ant movement behavior across large spatiotemporal scales, closely reflecting the ecology of our model species, Aphaenogaster senilis. We then incorporated this into a liquid brain framework, enabling a quantitative replication of ant foraging efficiency and their spatiotemporal dynamics. Our results highlight that a simple feedback mechanism explains the foraging patterns of this species. Indeed, such feedback is modulated by adjusting the proportion of two coexisting movement behaviors: while the recruits facilitated information transfer and food exploitation by aggregating closely to the nest, the scouts mostly bypassed this feedback, enabling the discovery of alternative food sources. These findings underscore how complex systems frameworks can benefit from empirical insights, enhancing our understanding of the mechanisms underlying collective intelligence in biological systems.
... operations (González Zevallos & Yorio, 2006;Oro et al., 2013). Climatic anomalies (Montevecchi & Myers, 1997;Trathan et al., 2015) and changes in environmental and oceanographic conditions (e.g., sea surface temperature and salinity, winds, wave height, currents, and tides) are considered the main natural stressors for facilitating the transfer of seabird carcasses to the coast (Haman et al., 2013;Wiese & Elmslie, 2006). ...
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Beached birds on marine coastal beaches, along with other megafauna, are a valuable source of biological information, offering insights into species occurrence and factors that negatively affect their populations. The main objective of this study was to evaluate the spatial and temporal variation, and species composition, of coastal and marine birds found on sandy beaches in the Bahía de San Antonio Protected Natural Area (Río Negro Province, Argentina), and to relate resulting species abundance and richness to oceanographic and environmental variables. A biweekly survey was carried out over two years (2020–2022), during which 672 beached birds were recorded. The overall encounter rate of beached birds was 1.35 birds/km. Most birds were identified to the species level, totaling 27 species belonging to 11 orders. The three most frequently encountered species were Magellanic Penguin Spheniscus magellanicus (49.38%), Kelp Gull Larus dominicanus (43.75%), and Neotropic Cormorant Nannopterum brasilianum (22.5%). The height of high tide and wind direction significantly affected beached bird abundance at various spatial and temporal scales. We conclude that the assemblage of beached birds is heterogeneous, mainly consisting of species that inhabit the Río Negro Province coast, rather than those from farther offshore. Future studies in the area should include drift experiments and cover a larger geographic scale.
... operations (González Zevallos & Yorio, 2006;Oro et al., 2013). Climatic anomalies (Montevecchi & Myers, 1997;Trathan et al., 2015) and changes in environmental and oceanographic conditions (e.g., sea surface temperature and salinity, winds, wave height, currents, and tides) are considered the main natural stressors for facilitating the transfer of seabird carcasses to the coast (Haman et al., 2013;Wiese & Elmslie, 2006). ...
Article
Beached birds on marine coastal beaches, along with other megafauna, are a valuable source of biological information, offering insights into species occurrence and factors that negatively affect their populations. The main objective of this study was to evaluate the spatial and temporal variation, and species composition, of coastal and marine birds found on sandy beaches in the Bahía de San Antonio Protected Natural Area (Río Negro Province, Argentina), and to relate resulting species abundance and richness to oceanographic and environmental variables. A biweekly survey was carried out over two years (2020–2022), during which 672 beached birds were recorded. The overall encounter rate of beached birds was 1.35 birds/km. Most birds were identified to the species level, totaling 27 species belonging to 11 orders. The three most frequently encountered species were Magellanic Penguin Spheniscus magellanicus (49.38%), Kelp Gull Larus dominicanus (43.75%), and Neotropic Cormorant Nannopterum brasilianum (22.5%). The height of high tide and wind direction significantly affected beached bird abundance at various spatial and temporal scales. We conclude that the assemblage of beached birds is heterogeneous, mainly consisting of species that inhabit the Río Negro Province coast, rather than those from farther offshore. Future studies in the area should include drift experiments and cover a larger geographic scale.
... Sin embargo, estos picos de disponibilidad de carroña pueden tener consecuencias directas no solo sobre las comunidades de carroñeros, sino sobre el resto del ecosistema (Olea et al. 2019). Por ejemplo, a nivel individual, el aumento de los recursos tróficos en los ecosistemas mediado por la caza puede tener un impacto en la fertilidad, tamaño corporal, fisiología, supervivencia y el área de campeo de las especies carroñeras (Oro et al. 2008(Oro et al. , 2013Margalida et al. 2011Margalida et al. , 2013. A nivel poblacional, se pueden producir cambios en el tamaño y/o densidad poblacional, estructura demográfica, comportamiento (patrones de búsqueda de alimentos o migración) o en la dieta de las especies (Mundy et al. 1992;Pulido 2007;Jackson et al. 2008;Donázar et al. 2010). ...
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Vertebrate scavengers play a crucial role in ecosystems by stabilizing food webs, accelerating nutrient recycling, and eliminating potential disease sources. In El Hondo Natural Park (SE Spain), a wetland of international importance for birds, periodic mortality events occur, such as the hunting of waterfowl. Uncollected hunting remains create predictable pulses of carrion utilized by different scavenger species. This study describes the community of terrestrial vertebrate scavengers and their patterns of consumption of carrion that simulates hunting in El Hondo. Thirty-nine waterfowl carcasses were placed after hunting events in three areas adjacent to the hunting reserves, and their consumption was monitored with camera traps. We recorded seven species of vertebrate scavengers, highlighting the role of the red fox (Vulpes vulpes) and the brown rat (Rattus norvegicus) as the main carrion consumers, although the latter showed lower efficiency, increasing the persistence time of carrion in the ecosystem. We also identified other vertebrate species, such as insectivorous birds, that consumed invertebrates attracted by the carrion. The results demonstrated that waterfowl hunting remains are used by a diverse community of vertebrates in wetlands. Additionally, our results suggest that hunting in protected areas can favour the presence of invasive species, such as the brown rat. This highlights the need to adequately manage the interactions between human activities and scavenger communities for the effective conservation of threatened ecosystems that are essential for biodiversity, such as wetlands.
... These proximal mechanisms of search are at the core of understanding ecological traps that can result from rapid changes in prey resource distribution [5]. They could also determine how likely predators are to switch to conspicuous, often predictable anthropogenic resources causing important conservation issues [6,7]. However, understanding the rules and cognitive strategies used by individuals to search for prey in the wild is scientifically challenging, especially when data about the resources and the behaviour of consumers are often limited [8][9][10]. ...
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Finding scattered resources is a challenge for marine predators, their search strategies shaping in turn their response to global changes. Three types of search strategies are generally considered: random opportunistic search, reliance on conspicuous social cues or long-term individual fidelity to predictably productive areas. More complex strategies, namely intermediate, composite and/or those varying across time and environmental conditions are likely to prevail but are rarely explored. We investigated memory strategies in Cape gannets, a marine predator heavily relying on social cues, and closely related to the northern gannet which shows long-term individual foraging fidelity. Repeat GPS tracks within seasons revealed that two different individuals leaving the colony more than 3 days apart showed random chances to forage in a similar direction, whereas within-individuals, birds persisted in a same direction for longer timescales, reaching random levels only after 10 days, or 9 consecutive trips. This strategy of transient individual preferences within a breeding season was observed in most individuals every year. These results suggest a consistent and complex search strategy mixing social cues and private information updated every few days. Our simple approach can readily be applied to other central place foragers to better understand the evolutionary ecology of search strategies.
... In recent years, wildlife's use of human food subsidies has been highlighted as a major threat to biodiversity (Oro et al. 2013;Newsome et al. 2015). Although there are many examples of successful populations that use human food subsidies from places like urban waste dumps (Kristan et al. 2004;Evans and Gawlik 2020), evidence for detrimental consequences for wildlife is also ample (see a general review, Newsome et al. 2015;Rodewald et al. 2011). ...
Article
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Wildlife feeding and nutrition are key drivers of several demographic parameters, such as breeding success and survival, influencing long-term population viability. To comply with the diet requirements that ensure offspring survival, parents adapt their forage strategies to the environmental conditions and resource availability. This is especially important for central-place foragers like raptors, where prey availability in the surroundings of nest and livestock carcasses significantly impact both foraging efforts and breeding success. Here we take advantage of 20 years extensive monitoring (2001–2020) of the Canarian Egyptian vulture (Neophron percnopterus majorensis) on the Fuerteventura Island (Canary Islands, Spain) to assess (1) what factors drive vulture diet diversity and, (2) how the number of livestock and diet diversity coupled together with environmental conditions affect breeding success and, ultimately, the conservation of vulture populations. We identified 3,787 prey items belonging to 37 different species. Diet diversity was positively related to the number of wild prey and to low livestock grazing pressure periods. Breeding success was positively related to the number of wild prey, low herbivory pressure and, to a lesser extent, to diet diversity. These results demonstrate the importance of wild prey on Canarian Egyptian vulture’s diet, albeit livestock carcasses are the most abundant feeding resource. We argue that livestock have controversial conservation implications for this species because it provides a stable feeding resource, but, in turn, is one of the major ecosystem disruptors. Overgrazing by livestock can negatively affect wild primary consumers, which are essential for this endemic vulture population.
... Our results contribute thus to enlarge the information available on vertebrate communities relying on anthropogenic food subsidies in the form of carrion. In the face of global change, this information would help to improve our understanding of the scavenger communities increasingly consuming human-mediated carrion such as hunting remains or livestock carcasses (Oro et al. 2013;Mateo-Tomás et al. 2015). ...
... Carcass use is a key ecological process, capable of altering entire food chain dynamics at the ecosystemic level (DeVault et al. 2003;Focardi et al. 2017). Scavengers play a dual role in this process, actively enhancing energy transfer pathways and redistributing nutrients (DeVault et al. 2003(DeVault et al. , 2016, while also serving as vital agents in mitigating the potential spread of diseases by decreasing the time host reservoirs are in contact (Ogada et al. 2012), thereby reducing the necessity for human management of carrion (Margalida and Colomer 2012;Bellan et al. 2013;Oro et al. 2013;Mateo-Tomás et al. 2015). Consistent with their prominent contribution to the global biomass of wild mammals (Greenspoon et al. 2023), ungulate species are the most significant suppliers of these calorie-and protein-rich food sources in terrestrial ecosystems (Selva et al. 2003;Focardi et al. 2017;Bassi et al. 2018), with diseases, roadkill, hunting, and natural predation typically playing the most prominent role as possible causes (Wikenros et al. 2013;Morant et al. 2023). ...
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Carcass utilization by scavengers is crucial for ecosystem dynamics, influencing energy transfer and nutrient cycling. Through the provision of unconsumed carcasses, the return of wolves (Canis lupus) to European ecosystems can trigger complex cascading effects on scavenger communities. Here, we investigate the scavenging dynamics of mammalian species in a prey-rich Mediterranean coastal area close to a large city where wolves have recently returned. Using camera traps, we monitored the scavenging activity on fallow deer (Dama dama) carcasses preyed upon by wolves over a five-year period following the predator’s return. We developed models to assess how competition between red foxes (Vulpes vulpes), wild boars (Sus scrofa), and wolves evolved over time, focusing on their carcass use, direct interactions, and spatiotemporal associations. Wolves exhibited consumption of only minor portions of prey and a negligible reuse of carcasses, while foxes and wild boars engaged in indirect competition for access to this emerging trophic niche. We found a notable temporal change in scavenging activity over the monitoring period, with wild boars progressively emerging as the primary scavenger and providing a substantial removal of carcass biomass. Our findings suggest that wild boars can assume a prominent scavenging role in environments where carcass availability is both abundant and predictable. This study underscores the importance of understanding scavenger temporal dynamics in the context of apex predator recolonization and highlights the need for further research to explore the long-term impacts of these interactions on community structure and ecosystem services as wolf populations continue to expand across Europe.
... Parmi les différents facteurs évoqués par Tissot et al. (2022) pouvant influencer les barrières du Perfect Storm, la disponibilité alimentaire est un facteur qui est aussi bien réduit qu'augmenté par les activités anthropiques selon les environnements. Par exemple, les activités humaines peuvent entraîner une augmentation de la disponibilité alimentaire que ce soit par l'eutrophisation, affectant certaines espèces aquatiques (par exemple Pihl 1994; Kido et Kneitel 2021; Dorgham 2014), ou par les importantes quantités de nourriture gaspillées et jetées qui deviennent accessibles à certaines espèces terrestres(Giraudeau et al. 2018;Oro et al. 2013;Tuomainen et Candolin 2011). Cependant, elles peuvent également diminuer la disponibilité alimentaire pour de nombreuses espèces, comme c'est par exemple le cas suite à la déforestation ou l'urbanisation d'un environnement(Bodo et al. 2021;Tuomainen et Candolin 2011). ...
Thesis
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Transmissible cancers are a rare phenomenon where cancer cells are transmitted from one individual to another. Even though there are currently only fourteen known cases of transmissible cancers in natural environments, their ecological and evolutionary impacts are significant for both host species and ecosystems. Given the lack of knowledge surrounding these transmissible cancers, this thesis focuses on the conditions for the emergence and spread of these cancers, the influence of environmental variables affected by human activities on these dynamics, and their consequences for hosts and ecosystems. The first task was to complete the conceptual model of the « Perfect Storm », which theorizes the conditions for the emergence of transmissible cancers, by adding a second barrier to the first barrier of acquiring transmissibility. This second barrier consists of environmental factors that can influence their spread within host populations. Indeed, abiotic and biotic variables can affect transmissible cancer cells and/or hosts infected by these cells, thus influencing their dissemination in host populations. This work also suggests that human activities can have a significant impact on the emergence and spread of transmissible cancers by altering variables affecting both barriers. To go beyond a conceptual model, laboratory experiments were conducted using the model organism Hydra oligactis and/or the zebrafish Danio rerio. An experimental evolution study of tumors in Hydra oligactis revealed that the first barrier of the Perfect Storm (i.e., acquisition of transmissibility) does not seem to be a major obstacle since some spontaneous tumors are transmissible from their onset. Therefore, the rarity of transmissible cancers may, for certain species, be more due to the difficulty of overcoming the second barrier related to environmental conditions influencing the survival of transmissible tumor cells and/or their host. A third study showed that food availability could influence the emergence and spread of transmissible cancers by promoting the appearance and progression of tumors when it is increased. Finally, this thesis addresses the evolutionary and ecological consequences of transmissible cancers for their hosts by showing that the presence of these tumor cells in hosts is not insignificant, both for the hosts and surrounding species. Their presence, on the one hand, induces changes in the host’s life-history traits, which mitigate the cost imposed by the tumor, and on the other hand, makes the host more susceptible to becoming a super-spreader of symbionts, thus impacting pathogen dynamics. Understanding these impacts is crucial for assessing the risks these cancers pose to biodiversity and ecosystem health, particularly due to oncogenic pollution of anthropogenic origin. In conclusion, this thesis provides new information on the earliest stages governing the appearance of transmissible tumors and the conditions necessary for their propagation. This work also connects some fundamental aspects of cancer biology to ecological and evolutionary dynamics, highlighting the increasing importance of this research in the context of global and anthropogenic changes.
... It helps to improve survival rate and body condition, enhance reproductive performance, reduces cost of feeding time, to minimize risk of migration, predation and extinctions particularly for endangered species. Thus, ecological and biological processes of many species are regulated by those human generated food items [12]. However, the reduction of food availability in waste disposal sites may also have a negative impact such as shifting in feeding behaviors and other costs [13]. ...
... The 'green wave surfing' hypothesis focuses on how following the natural forage maturation benefits migrants by affecting their accumulation of fat [42]. However, ecosystems are being altered by anthropogenic food sources becoming increasingly available and exploited by a large number of species [70]. Red deer across Europe extensively used agricultural farmlands [27,[71][72][73][74], and high access to such resources lead to higher body mass [25,75]. ...
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The timing of migration is fundamental for species exploiting seasonally variable environments. For ungulates, earlier spring migration is expected with earlier vegetation green-up. However, other drivers, such as access to agricultural farmland and variation in local conditions, are also known to affect migration. We investigated the timing of spring migration for 96 male and 201 female red deer (Cervus elaphus) using a long-term dataset (2005–2020). Overall, the timing of migration was mainly characterized by large individual variability between and within years (95% range 6 April to 18 June). The spring migration timing was, as expected, later with colder winter and spring conditions (North Atlantic Oscillation (NAO) winter and April indices) and later peak vegetation green-up (NDVI), with a five-day delay in green-up causing a migration delay of 1.2 days. Timing was also influenced by local conditions in summer and winter home ranges. Red deer with greater access to farmland and a more variable topography (hence variable plant phenology) in winter delayed migration. Similarly, individuals with higher-elevation summer ranges (with delayed onset of plant growth) also delayed migration. Our analyses highlight that the timing of red deer migration is determined by multiple drivers affecting foraging conditions in the landscape, indicative of considerable phenotypic plasticity.
... Incidental mortality is not the only issue for seabirds attending vessels. Other effects may include changes in their foraging behavior and patterns of distribution since seabirds learn to find and follow fishing vessels (Oro et al. 2013), and also plastic pollution associated with debris generated by vessels (Copello & Quintana 2003;Phillips & Waluda 2020). Highly productive waters in the Patagonian shelf and shelf-break are heavily used by a range of fishing fleets, chiefly bottom and mid-water trawlers targeting the Argentine hake (Merluccius hubbsi), Hoki (Macruronus magellanicus), Southern blue whiting (Micromesistius australis) and the Argentine red shrimp (Pleoticus muelleri), among others, but also the benthic otter trawl net vessels targeting the Patagonian scallop (Zygochlamys patagonica) and a massive jigging fleet targeting the Argentine Shortfin Squid (Illex argentinus) along the continental shelf-break. ...
Chapter
The Patagonian shelf-break represents the transition zone from the relatively shallow waters of the continental shelf to the deep plains exceeding 2000 m depth. Along this pronounced slope, shelf-edge and wind-driven upwelling fronts support high and persistent levels of primary and secondary productivity, attracting an important abundance and diversity of marine megafauna, including seabirds and marine mammals. Among seabirds, albatrosses, large petrels, and shearwaters are highly migratory seabirds capable of ranging vast distances and abundant in this region of the planet. Seabird species may use these fronts as primary foraging areas if their prey are at a disadvantage while exposed to thermal, haline, or nutritional stresses. Recent surveys conducted in the northern Patagonian shelf and shelf-break areas show a spatial correlation between seabird abundance and species richness with confluence zones near the slope, and the differential use of some species and composition of seabird assemblages in waters either north or south of the Malvinas-Brazil confluence. The Patagonian shelf and shelf-break, and its biodiversity, is exposed to a variety of threats originated or enhanced by anthropogenic activities. In the past four decades, many seabird populations and other megafauna have experienced declines product of the widespread human perturbation and losses of original marine and breeding habitats. Compared to other bird species, the conservation status of seabirds is rapidly declining, with more than one third of the 326 extant seabird species listed as threatened with extinction. Pelagic species, chiefly Procellariforms (albatrosses, petrels and shearwaters), are particularly threatened, and their populations have declined faster than coastal species. The exploration and exploitation of non-renewable resources, activities that are showing an expansion over the Patagonian shelf and the shelf-break, have the potential to alter the at-sea distribution of pelagic seabirds at micro and meso-scale. Regarding the exploitation of renewable resources, the distribution of fishing effort is highly overlapped with foraging seabirds, showing impacts that range from food supplementation through scavenging behind vessels, to resource competition and incidental mortality. Albatrosses and petrels are susceptible to threats operating throughout their wide distribution ranges extending across national boundaries into international waters. Recent evidence has also demonstrated that the negative effects of seabird bycatch and other stressors affecting species on land and at sea can be exacerbated by the effects of climate change and its concomitant changes in atmospheric circulation, water masses, and prey distribution. These environmental changes have even the potential of generating significant shifts in the distribution of human activities and the overlap with seabirds. Addressing this issue likely represents one of the major environmental conservation challenges that will require well-informed management practices and the implementation of meaningful policy responses.
... Supplemental feeding is also a popular means to increase the likelihood of encountering wildlife. For example, feeding stations can increase density of game species for hunters (i.e., ~2.8 trillion tonnes of shelled corn is provided to big game ungulates every year in the U.S; Oro et al., 2013, Murray et al., 2016, food is provided for wildlife watching (i.e., bird watching; Valentine andBirtles, 2004, Dayer et al., 2019), and in tourism to generate consistent, predictable, and up-close encounters with wildlife (Meyer et al., 2022). Feeding from these supplemental food sources can exceed the caloric intake required to meet daily requirements (Brunnschweiler et al., 2018), thus providing surplus energy leading to increased fat stores and accelerated growth . ...
Thesis
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Wildlife tourism often uses food-based attractants to aggregate focal species, unintentionally attracting and feeding non-focal species, the impact of which is poorly understood. In South Australia's Neptune Islands Group Marine Park, bait and berley (southern bluefin tuna Thunnus maccoyii) is used to entice white sharks (Carcharodon carcharias) to cage-diving vessels, inadvertently attracting silver trevally (Pseudocaranx georgianus). These silver trevally form large aggregations around cage-diving vessels as they consume the bait and berley, often impeding tourists' views of the focal white sharks. The impacts of the white shark tourism industry on the spatiotemporal distribution and behaviour of silver trevally, and potential flow-on effects on their physiological processes (i.e., growth, reproduction, healing) is unknown. This study aimed to comprehensively assess how the aggregatory behaviour and feeding of bait and berley may affect silver trevally movements, abundance, growth, and physiological condition. Due to impacts on the spatiotemporal distribution and activity of similar non-focal species, I first monitored the movements, distribution, and activity of 25 silver trevally in response to cage-diving operators using a fine-scale acoustic telemetry array (Chapter 2). The number of days silver trevally were present per week and the number of hours per day at the Neptune Islands increased by 32% and 20%, respectively, when operators were present. However, a seasonal exodus by 76% of individuals triggered by low water temperature suggested that silver trevally are not permanent residents of the Neptune Islands, and still undergo natural movements away from this near-continuous source of food. Cage-diving tourism also reduced the core space use of silver trevally, aggregating them at the surface (< 5 m depth), close to food-based operators. Despite changes in space use and residency, overall activity did not substantially increase when operators were present, despite frequently observed bursts of acceleration. The near-continuous feeding on bait and berley, large amount of time spent at the Neptune Islands, and the lack of increased activity might result in an energy surplus in silver trevally and affect growth, reproduction, and physiology. With an understanding of the spatiotemporal distribution and activity of the silver trevally (Chapter 2), the size of the affected population remained unknown. Therefore, I developed and tested novel mark-resight methods (Chapter 3), using the most precise method to quantify and assess trends in the population size of silver trevally occupying the Neptune Islands (Chapter 4). I tagged 700 silver trevally with conventional identification tags, undertook monthly surveys over two years, and used the acoustically tagged silver trevally from Chapter 2 to estimate resighting probability to improve the precision of modelled population size. I estimated up to ~4000 silver trevally at the Neptune Islands, with the population size decreasing with temperature, aligning with the seasonal exodus observed in Chapter 2. However, the number of silver trevally was not affected by the intensity of cage-diving operations. I then tested the physiological effects of silver trevally exposure to bait and berley using age-at-length, bioelectrical impedance, and fatty acid analysis (Chapter 5). The silver trevally at North Neptune Islands that are frequently exposed to bait and berley were larger than silver trevally of the same age from locations with similar habitats, but without supplemental feeding from cage-diving operations. This was supported by the higher levels of Eicosapentaenoic and Oleic acid in silver trevally from North Neptune Islands. Eicosapentaenoic and Oleic acid, which are known to be high in the bait and berley used, are also known to be important for multiple physiological functions and to increase the overall growth performance, welfare, and condition of teleosts. However, mortality rate and body condition were similar across locations, indicating that while silver trevally may grow faster, consumption of bait and berley may not lead to negative effects on the health or fitness of silver trevally. This is the first study to assess the ecology of silver trevally in temperate southern Australia, and how it is influenced by wildlife tourism, providing a baseline for impacts of supplemental feeding on a non-focal species. I found effects on the movement, behaviours, and growth of silver trevally, but broader impacts on their health and physiology were undetected. Importantly, despite the effects described here, exodus from the Neptune Islands during cold periods, and the effect of temperature on population size, indicates that silver trevally are still undergoing natural movements and behaviours triggered by thermal cues. Overall, my study comprehensively assesses the ecology of silver trevally through a multidisciplinary approach, showing that small and non-focal species can be affected by provisioning, despite under representation in management frameworks and investigative studies.
... and temporal distribution of these foods also tends to be highly predictable (Oro et al. 2013;McLennan and Ganzhorn 2017), which reduces the need for the animals to be searching constantly for food (Orams 2002). ...
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The availability of manmade foodstuffs in the environment may significantly alter the diets, behavior and health of wild animals and the ecosystems ecology. One of the principal problems faced by urban populations of capuchin monkeys is their contact with household refuse, which may provoke a number of impacts on the health of these animals. The present study tested the use of feeding platforms as a strategy to reduce the consumption of unhealthy foodstuffs by these animals and analyzed the influence of this measure on the activity patterns and social interactions of the study groups. For this, we verified the patterns of use of a feeding platform by a capuchin group in an urban park in Goiânia, central Brazil, and compared this study population with those of other parks where alternative feeding protocols are implemented, ranging from continuous provisioning to no intervention whatsoever. Behavioral data were collected using scan sampling. The data analysis was divided into two steps: (i) comparison of the different conditions found in the populations with varying types of feeding platform usage and (ii) comparison of the time budget among sites in the context of seasonal variation. The presence of feeding platforms effectively reduced the consumption of refuse in the study groups, although it did also cause an increase in agonism in the animals and altered their activity patterns, leading to a greater dependence on provisioned resources. The results of this study highlight the complex interaction between human activities and the local wildlife in the urban setting, and the need for more detailed studies, to develop more effective management strategies.
... This likely arises due to humans providing shields for ungulates and small mammals from carnivores' predation risk, often termed the "human shield hypothesis" (Berger 2007;Pérez-Flores et al. 2022). Alternatively, it could be due to the higher availability of anthropogenic resources near security posts or supplemental feeding (Oro et al. 2013;Hill et al. 2021). This also means that animals may become accustomed to the presence of humans near security posts and may become more vulnerable to being hit by vehicles when attempting to cross the roads. ...
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Collisions between wildlife and vehicles are a growing conservation issue in Nepal. We examined spatial and temporal patterns of wildlife roadkill in Banke National Park and Bardia National Park. During six surveys conducted between April and June 2022, 101 animal carcasses were recorded along a 126-km stretch of the east-west national highway that runs through the two national parks. The opportunistic secondary data from national park records showed that there were 375 roadkill incidents between July 2017 and May 2022. Based on primary and secondary data (476 road fatalities from 35 different species), mammals were the most affected group (77.31%), followed by reptiles (12.61%), birds (6.93%), and amphibians (3.15%). The number of road fatalities per km was higher in Banke (0.77) than in Bardia (0.49). Poisson regression models show that road sections with high visibility (β = −0.41) and road sections passing through human settlements (β = −0.72) have fewer road fatalities. In contrast, mortality rates were higher on road sections that crossed water bodies (β = 0.54), passed through the core of the national park (β = 0.82), and near park checkpoints (β = 1.03). Seasonal variations in traffic accidents show a higher number of fatalities in winter (χ² = 17.54). Overall, our results identify landscape features that may make roads more susceptible to traffic accidents, highlighting the need to consider their spatial distribution when prioritizing roadside mitigation measures. We recommend regulating vehicle speeds along wildlife concentration areas and clearing roadside vegetation to improve visibility, especially in winter, should help reduce the number of wildlife roadkill.
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Humans are altering natural environments at unprecedented rates. Ecological generalism is one of the strongest predictors of survival in light of these changes which, in animals, may be shaped by bold and innovative behaviours. Species with greater habitat generalism are proposed to behave more boldly (e.g., touching and ingesting novel food). Species with greater dietary generalism are proposed to behave more innovatively (e.g., novel problem-solving to access food). Support for both hypotheses exists but remains largely restricted to broad comparisons between generalists and specialists. Further comparative data are needed to understand the extent to which these behavioural patterns might shape more nuanced ecological variation between species, such as species with finer-scale niche differences. We compared bold and innovative behaviour in two wild sympatric generalists, the Northern raccoon ( Procyon lotor ) and Virginia opossum ( Didelphis virginiana ), using a pull-string task with strings and wires attached to vertical cups containing high-value food. Although both species are broadly classified as generalists, raccoons show relatively greater habitat and dietary flexibility than opossums. Because they live sympatrically, it offers a unique opportunity to test – at the same time and locations – whether these finer-scale niche differences are reflective of differences in their bold and innovative behaviour. We predicted that raccoons would display bolder behaviour (in terms of touching our novel task) and more innovative behaviour (in terms of solving it). We found that both species were equally likely to acknowledge and touch the task, but raccoons were more likely to display innovation to access the food. Raccoons’ propensity for using innovation to solve novel foraging challenges may contribute to their greater ecological flexibility compared to opossums. More broadly, our findings may help explain differences in how each species adapts to environmental changes. Highlights Bold and innovative behaviour may help some species adapt to environmental changes We administered a novel pull-string task to wild raccoons and opossums Raccoons displayed more innovative, not bolder, behaviour than opossums Both species are generalists, but raccoons are more flexible than opossums Differences in innovation may shape their finer-scale niche differences
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Predicting animal movements and spatial distributions is crucial for our comprehension of ecological processes and provides key evidence for conserving and managing populations, species and ecosystems. Notwithstanding considerable progress in movement ecology in recent decades, developing robust predictions for rapidly changing environments remains challenging. To accurately predict the effects of anthropogenic change, it is important to first identify the defining features of human‐modified environments and their consequences on the drivers of animal movement. We review and discuss these features within the movement ecology framework, describing relationships between external environment, internal state, navigation and motion capacity. Developing robust predictions under novel situations requires models moving beyond purely correlative approaches to a dynamical systems perspective. This requires increased mechanistic modelling, using functional parameters derived from first principles of animal movement and decision‐making. Theory and empirical observations should be better integrated by using experimental approaches. Models should be fitted to new and historic data gathered across a wide range of contrasting environmental conditions. We need therefore a targeted and supervised approach to data collection, increasing the range of studied taxa and carefully considering issues of scale and bias, and mechanistic modelling. Thus, we caution against the indiscriminate non‐supervised use of citizen science data, AI and machine learning models. We highlight the challenges and opportunities of incorporating movement predictions into management actions and policy. Rewilding and translocation schemes offer exciting opportunities to collect data from novel environments, enabling tests of model predictions across varied contexts and scales. Adaptive management frameworks in particular, based on a stepwise iterative process, including predictions and refinements, provide exciting opportunities of mutual benefit to movement ecology and conservation. In conclusion, movement ecology is on the verge of transforming from a descriptive to a predictive science. This is a timely progression, given that robust predictions under rapidly changing environmental conditions are now more urgently needed than ever for evidence‐based management and policy decisions. Our key aim now is not to describe the existing data as well as possible, but rather to understand the underlying mechanisms and develop models with reliable predictive ability in novel situations.
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Echinococcus multilocularis (Em) is a neglected zoonotic cestode circulating among wild canids and voles across the northern hemisphere, and is the aetiological agent of alveolar echinococcosis in humans. The expansion of the European distribution of this parasite has been raising public health concerns in recent decades. We aimed to investigate the occurrence of Em and other taeniids in wild carnivore faeces in the Apuan Alps Regional Park and the Monte Pisano mountain chain (northern Tuscany), a few hundred kilometres from the nearest report of Em in Italy. Using standard flotation-sieving and nested PCR of partial cox1 sequences on single harvested Taeniid eggs, we detected several Em haplotypes in red foxes and grey wolves in both study areas, suggesting limited genetic diversity. However, these findings could not be confirmed using more sensitive qPCR probes from the same samples. In addition, we report eggs of Taenia krabbei and T. hydatigena from wolves, Dipylidium caninum and Mesocestoides sp. in foxes, and T. polyacantha and Mesocestoides litteratus in both foxes and mustelids. Further investigation of the distribution of Em in the northern Apennines is necessary to assess if the presence of this potentially lethal zoonotic parasite is stable and expanding southward.
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El sistema fluvio-marino del Río de la Plata (SFMRP) es un ambiente complejo, dinámico y altamente productivo dentro del cual las aves marinas tienen particular relevancia. Este sistema, de gran importancia ecológica, meteorológica y oceanográfica para la región, propicia el desarrollo de actividades humanas que traen aparejados problemas de conservación. En este trabajo caracterizamos los ensambles de aves marinas y su relación con las actividades que ocurren en el área desde una perspectiva ambiental. Dentro del ensamble de aves marinas (ca. 74 especies) del SFMRP, las gaviotas y gaviotines son los grupos más representativos y dominantes. El SFMRP también contiene una buena representación de Procellariiformes que utilizan principalmente aguas de altamar. Las principales actividades humanas desarrolladas en el área de interés, que incluyen el desarrollo urbano e industrial, las pesquerías comerciales y recreacionales, y la exploración-explotación de hidrocarburos, ocasionan fragmentación y degradación del paisaje, sobreexplotación de recursos, y contaminación (e.g., química, lumínica y sonora, entre otras). Las problemáticas ambientales destacadas afectan principalmente los movimientos, alimentación, y estado sanitario de las aves marinas que utilizan el SFMRP. Se identificaron y caracterizaron siete unidades de conservación a modo de enfoque para organizar y facilitar el desarrollo e implementación de herramientas de manejo. Destacamos la necesidad de reforzar la colaboración entre diferentes actores y sectores involucrados en el área para mitigar los impactos sobre la biodiversidad de aves marinas. Se recomienda además el establecimiento de programas de evaluación y/o monitoreo de los ensambles de aves marinas y desarrollar e implementar los planes de manejo de las unidades de conservación identificadas.
Chapter
American herring gulls (Larus smithsoniansus; hereafter herring gulls) are widely distributed, common seabirds with generalist diets. As is the case for many large gull species, herring gulls exploit human-altered landscapes for feeding and breeding, and these synanthropic birds can create a suite of human–bird conflict situations, ranging from mild annoyances (e.g., faeces on vehicles) to major risks (e.g., striking aircraft). At Brier Island, Nova Scotia, a large colony of nesting gulls uses a diversity of human and natural foraging areas and foods during the breeding season. Some gulls nest in proximity to the globally rare eastern mountain avens (Geum peckii), and there are concerns that altered soil chemistry through nutrient additions from avian faeces, or physical alterations to soil and plants from nesting gulls, may deleteriously affect this plant. In this chapter we summarize some of the issues around managing gulls, and describe some of the initial, largely unsuccessful efforts to manage them at Brier Island.
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Resource quality can have conflicting effects on host-parasite interactions; for example, higher resource quality might increase host investment in immune function, or conversely, might permit greater parasite reproduction. Thus, anticipating the impact of changing resource quality on host-parasite interactions is challenging, especially because we often lack a mechanistic understanding of how resource quality influences host physiology and fitness to alter infection outcomes. We investigated whether there are generalizations in how resource quality affects multiple host clones' interactions with different parasites. We used the Daphnia freshwater zooplankton model system to experimentally investigate how a resource quality gradient from high-quality green algae to poor-quality cyanobacteria diets influences host fitness, physiology, and infection by two parasites: a bacterium, Pasteuria ramosa, and a fungus, Metschnikowia bicuspidata. We ran a separate experiment for each parasite using a factorial design with four diets, two Daphnia dentifera host clones, and parasite-inoculated and uninoculated treatments (16 treatments per experiment). Diet strongly influenced infection by the fungus but not the bacterium. These relationships between diet and infection cannot be explained by changes in feeding rate (and, therefore, parasite exposure). Instead, the impact of diet on fungal infection was associated with impacts of diet on the earliest stage of infection: hosts that fed on poor quality diets had very few attacking spores in their guts. Diet did not significantly influence host immune responses. Diet influenced spore production differently for the two parasites, with reduced resource quality limiting the number of fungal spores and the size (but not number) of bacterial spores. Diet, host clone, and infection all affected host fitness. Interestingly, diet influenced the impact of the bacterium, a parasitic castrator that induces gigantism; for one clone, infected hosts fed high quality diets still produced a substantial number of offspring, whereas resource limitation hindered gigantism. Finally, there were often costs of resisting infection, though these generally were not affected by diet. Overall, we show that resource quality differentially impacts the exposure, infection, and proliferation processes for different parasites and host clones, which highlights the need to use multi-genotype and multi-parasite studies to better understand these complex interactions.
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In a rapidly changing world, the loss of global biodiversity presents a significant challenge. While sustainability has become a guiding principle for balancing the protection of the environment along with economic development and human well-being, its implementation can often be disjointed across various sectors. The incoherence in the integration of environmental policies can lead to unintended negative impacts on biodiversity, particularly for vulnerable species like vultures and the environmental services they provide. Vultures, as a highly threatened group of birds, are especially vulnerable to poisoning, but also to new circular economy and renewable energy policies such as the closure of landfills and wind energy. Thus, it is imperative to evaluate the mechanisms and demographic responses of vulture species to these new paradigms. My thesis examines the demography of the griffon vulture Gyps fulvus in northeast Iberian Peninsula, using long-term data to provide a comprehensive understanding of the population dynamics in response to a changing environment. In Chapter 1, we studied how the local griffon vulture population in Central Catalonia responded to reduced organic matter in an open landfill due to European sanitary measures aimed at closing landfills. Using the robust Schwarz and Arnason Jolly-Seber model, we estimated the vultures' apparent survival probability and annual abundance. We found that the available organic matter in the landfill significantly declined after a waste treatment centre was established, negatively impacting apparent survival. However, local abundance remained stable, with an increase attributed to the growth of the Catalonian breeding population. This suggests that local waste management measures had limited impact on vultures, as their high dispersal capacity allows them to find alternative food sources. In Chapter 2, we used a Bayesian hierarchical Cormack-Jolly-Seber model to analyze the age-specific demographic response of the local vulture population at the landfill, estimating apparent survival and permanent emigration probabilities under three scenarios of organic matter availability: no reduction, substantial decrease, and drastic decrease. We found a notable increase in transients among newly captured immatures and adults. Apparent survival in juveniles declined, while in immature residents increased and adult residents decreased. The results suggested that intensified intraspecific competition due to reduced food increased permanent emigration. However, resident immatures showed resilience, indicating that high-quality individuals persisted despite food scarcity. In Chapter 3, we used a multi-site Integrated Population Model (ms-IPM) to examine the dynamics of griffon vulture populations in Catalonia, Aragon, and the Valencian Community. We aimed to understand demographic processes and inform site-specific conservation strategies. We observed different trends: steady growth in Catalonia, stabilization in the Valencian Community after an initial increase, and a decline with a slight recovery in Aragon. Key growth factors varied by region: adult survival in Aragon, floater-to-breeder ratio and immigration in the Valencian Community, and all three factors in Catalonia. Density dependence affected the floater-to-breeder ratio and immigration in Catalonia and the Valencian Community, with higher emigration to the other two sites in the vultures of Valencian Community, likely due to nearing carrying capacity. Populations in Aragon and the Valencian Community are stable, while Catalonia is growing. Maintaining adult survival in Aragon is crucial, given its lower rate and potential non-natural mortality sources. This study highlights the value of ms-IPMs for understanding complex population dynamics and the need for targeted conservation strategies. In conclusion, by applying demographic models, including the ms-IPM, and addressing data heterogeneity and uncertainty, in this thesis we gained a deeper understanding of griffon vulture population dynamics. This approach helped identify key demographic drivers, identify possible environmental impacts, and inform conservation strategies, highlighting the need for cohesive policies across regions to effectively conserve vulnerable species like vultures.
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Opportunistic species, including some gulls (Laridae), can benefit from urbanization and increased anthropogenic food resources. Knowledge of the level of exploitation of anthropogenic resources by gulls is crucial to understand how changes in food availability might affect their populations, which in turn may impact other species. The Kelp Gull Larus dominicanus is widely distributed in the southern hemisphere and consumes a wide variety of resources, from waste in landfills to seabirds. We assessed if proximity to landfills influenced the diet and trophic ecology of Kelp Gull incubating adults and chicks using a combination of conventional diet sampling (stomach contents, regurgitated pellets), and carbon and nitrogen stable isotope analysis of blood plasma in seven colonies over two consecutive years in South Africa. Kelp Gulls consumed a variety of resources, including marine (e.g. fish), coastal (e.g. molluscs), terrestrial natural (e.g. insects, mammals), or terrestrial anthropogenic (e.g. chicken, bread) items. Inter‐annual differences were most apparent among gulls breeding next to a seabird colony, whereas gulls breeding at other colonies were more consistent in diet and trophic ecology. At most colonies, chicks were fed more natural and higher trophic level food items than were consumed by incubating adults. Overall, distance to landfill did not strongly affect the diet and trophic ecology and our results suggest that the Kelp Gull's broad feeding ecology allows it to buffer changes in food availability by switching among food resources. However, such dietary changes triggered by human actions may impact other species, including threatened seabirds.
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To evaluate whether the abundance of coyotes Canis latrans was influenced by the availability of anthropogenic foods in a humanized landscape, we compared three neighboring areas (hereafter referred to as NA, CA, and SA) under contrasting human pressures within the Santa Monica Mountains of California, USA. We quantified the use of anthropogenic foods by coyotes and assessed local densities within these three regions. Overall, 761 coyote feces were analyzed; identified food items were categorized into 11 food types (7 native and 4 anthropogenic). Though small mammals (lagomorphs and rodents) were the main prey of coyotes in all areas and seasons, log-linear modeling of multiway contingency tables indicates that consumption of anthropogenic foods by coyotes varied significantly throughout study areas. Thus, in the most humanized area (CA; 24% of this region is residential habitat), anthropogenic foods (trash, livestock, domestic fruit) comprised seasonally between 14 and 25% of total items in coyote diets, whereas in the least humanized area (NA; 2% residential) anthropogenic foods only comprised seasonally between 0 and 3% of items. Coyote density, estimated by foot-hold trapping surveys and by genotyping feces, was also highly variable between areas. The heavily human-impacted CA area had the highest coyote density (2.4-3.0 ind. km-2), whereas coyote density was significantly lower (0.3-0.4 ind. km-2) in the least humanized area (NA). In the third region (SA; 10% residential), with an intermediate level of human pressure, both importance of anthropogenic foods in coyote diet (4-6%) and coyote density (1.6-2.0 ind. km-2) were intermediate compared to the other regions. Our data suggest that subsidization by anthropogenic foods augments coyote densities and alters their diets in the Santa Monica Mountains, California. We include data from literature to show that anthropogenic foods are used by omnivorous mammals throughout the world. Surprisingly, however, the potential effects of allochthonous inputs on such species are not well-understood. Thus, further research on this phenomenon in humanized landscapes is needed.
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The term "invader" is typically paired with adjectives such as "non-native" and "alien", yet native species can also cause ecological and economic impacts that rival those of well-known invasive species. By spreading within their historical range, attaining extreme abundances, and exerting severe per-capita effects as a result of predation or competition, native invaders can create an unusual set of challenges for science, management, policy, and society. Identifying when, where, and why species become invaders in their native ranges requires additional scientific inquiry, outside the current focus of invasion biology. Management strategies often mitigate the symptoms rather than address the causes of problematic native species invasions. Convincing stakeholders to comply with management actions aimed at controlling native invaders creates societal challenges and policy makers must prioritize goals from varied and often conflicting human interests. We illustrate these challenges by highlighting native species that adversely affect threatened and endangered Pacific salmon (Oncorhynchus spp).
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Tipping points ? where systems shift radically and potentially irreversibly into a different state ? have received considerable attention in ecology. Although there is convincing evidence that human drivers can cause regime shifts at local and regional scales, the increasingly invoked concept of planetary scale tipping points in the terrestrial biosphere remains unconfirmed. By evaluating potential mechanisms and drivers, we conclude that spatial heterogeneity in drivers and responses, and lack of strong continental interconnectivity, probably induce relatively smooth changes at the global scale, without an expectation of marked tipping patterns. This implies that identifying critical points along global continua of drivers might be unfeasible and that characterizing global biotic change with single aggregates is inapt.
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The golden jackal and red fox are among the wildlife species protected by Israeli law as enforced by the Israel Nature and Parks Authority. In 1964, as a part of a management program to control rabies in Israel, a poison eradication campaign was launched to exterminate golden jackals, considered to be the main reservoir of the disease. The program resulted in the near-complete extermination of jackals in Israel, while foxes were only mildly affected. Jackals have since regained their original numbers and have recolonized southern Israel. We here examined the population structure of the golden jackal and red fox in Israel, 48 years after the poison eradication campaign. DNA from 88 golden jackals and 89 red foxes representing five different geographic regions was extracted and amplified at 13 microsatellite loci in order to characterize the populations on a genetic level. High genetic diversity was found among the jackal and fox populations. A possible migration route through the Jordan Rift Valley was suggested for both species by the genetic similarity of populations in northern and southern Israel. However, in both species, the animals from the center of Israel were distinctive from those north or south, indicating the relative isolation of central populations, likely due to fragmentation or a high abundance of food resources. Genetic profiles obtained for the golden jackal and the red fox in Israel may aid in their conservation management and in the study of zoonotic diseases.
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The shift in emphasis from single spe- cies to ecosystem conservation is revealing how community interactions can potentially influence single species viability and conservation. Although there is much theory and empirical data concerning the dynamic consequences of exploitative inter- actions, there is still a very poor understanding of the effects of interference interactions. Recent studies, as shown in this review, have documented widespread effects of such interactions among mammalian carnivores. Harassment, loss of kills and intraguild predation have been documented in a wide range of species. The demonstrated effects also include avoidance of larger carnivores in both time and space and reductions in one species density or even total exclusion from certain habitats or regions. Our review of the literature thus provides a range of empirical examples that together demonstrate that these interactions have very important implications on carnivore demography. We believe that the effects of interference might differ strongly from the effects of exploitative competition. This is because interference might have the potential to affect population growth in an inverse density- dependent manner and thereby also reduce popu- lation growth at low densities, therefore increasing extinction probabilities. These factors need to be considered when planning future multi-species con- servation. Further research into the temporal and spatial aspects of co-existence are required if diverse guilds and communities are to be conserved.
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Shark feeding is widespread throughout tropical, subtropical and temperate marine ecosystems and gives rise to controversy because there is little consensus regarding its management. There are few comprehensive reports that consider how shark feeding with bait might impact local fishes, despite the development of this practice during the last few decades. Although shark feeding might theoretically have parasitological effects on local non-target fish species in the vicinity of feeding areas, this aspect has never been investigated. During an extensive parasitological survey conducted between 2005 and 2007, a total of 1117 fish belonging to six common grouper and snapper species were sampled throughout the entire north coast of Moorea Island (French Polynesia), encompassing three localities where feeding has occurred frequently since the 1990s. Parasites exhibited no spatial patterns except for the infections on the blacktip grouper (Epinephelus fasciatus). On this species, the prevalence of larval cestodes that parasitise sharks as adults and the intensity of their infestation were significantly higher around shark-feeding localities compared with non-shark-feeding localities. Our results suggest for the first time that although long-term shark feeding has parasitological implications, the impacts appear limited, only involve cestode larvae from one host species and do not seem to affect the health of the fish we studied.
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1. The present study compares breeding parameters and adult survival rate in a herring gull colony before and after the closing of a large refuse tip where breeders used to find most of their food. During the first study period (1983-88) food of human origin was abundant and virtually always available. During the second period (1989-90) such food was scarce. 2. The annual adult survival rate was time-dependent. It varied from 0.826 (SE = 0.031) in 1987-88 to 0.975 (SE = 0.022) in 1985-86. The average survival rate calculated for 1983-90 was 0.881 (SE = 0.014). There was no significant difference in adult survival between males and females. The closure of the refuse tip was not followed by a significant decrease in adult survival rate. 3. After the refuse tip was closed, mean clutch size and mean production of young per breeding pair decreased by 6.7% and 49.1%, respectively. Mean adult body weight decreased by 4.6% for males and by 4.7% for females. 4. The proportion of non-breeders among former breeders and the proportion of 3- and 4-year-old individuals among ringed birds did not change after closure of the tip. 5. The results are discussed in terms of the life-history theory, which predicts that in long-lived species a decrease in food supply should affect fecundity before affecting adult survival.
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A systematic review was conducted by a multidisciplinary team to analyze qualitatively best available scientific evidence on the effect of agricultural intensification and environmental changes on the risk of zoonoses for which there are epidemiological interactions between wildlife and livestock. The study found several examples in which agricultural intensification and/or environmental change were associated with an increased risk of zoonotic disease emergence, driven by the impact of an expanding human population and changing human behavior on the environment. We conclude that the rate of future zoonotic disease emergence or reemergence will be closely linked to the evolution of the agriculture-environment nexus. However, available research inadequately addresses the complexity and interrelatedness of environmental, biological, economic, and social dimensions of zoonotic pathogen emergence, which significantly limits our ability to predict, prevent, and respond to zoonotic disease emergence.
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Selective harvesting of animals by humans can affect the sustainability and genetics of their wild populations. Bycatch - the accidental catch of non-target species - spans the spectrum of marine fauna and constitutes a harvesting pressure. Individual differences in attraction to fishing vessels and consequent susceptibility to bycatch exist, but few studies integrate this individual heterogeneity with demography. Here, we tested for the evidence and consequences of individual heterogeneity on the demography of the wandering albatross, a seabird heavily affected by fisheries bycatch. We found strong evidence for heterogeneity in survival with one group of individuals having a 5.2% lower annual survival probability than another group, and a decrease in the proportion of those individuals with the lowest survival in the population coinciding with a 7.5 fold increase in fishing effort in the foraging areas. Potential causes for the heterogeneity in survival are discussed and we suggest that bycatch removed a large proportion of individuals attracted by fishing vessels and had significant phenotypic and population consequences.
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Upcoming reform of the European Union (EU) Common Fisheries Policy will be the biggest change in European fisheries management for a generation. A central plank of this reform is a proposed ban on discards, to aid the creation of economically and environmentally sustainable fisheries. This, together with a global trend for declining discards, may have unforeseen knock-on consequences for the large number of scavenging seabirds that consume this plentiful subsidy. Discards have shaped many aspects of seabird foraging, distribution and population dynamics. Here, we review these effects and consider the potential for both negative and positive impacts of discard reforms for seabirds, with particular focus on the EU, and propose recommendations for ongoing research and conservation. EU seabird scavengers are dominated by a relatively small number of large generalist taxa. Many of these occur at globally significant numbers within the EU, but may be able to buffer a decline in discards by switching to feed on alternative foods. A discard ban may have negative consequences by creating a food shortage for scavenging birds. Some species may offset this by feeding more on other birds, with potentially negative population-level impacts, or by moving into novel environments. Benefits of a discard ban may be a reduction in seabird bycatch in fishing gears, as well as a reduction in populations of large generalist species that currently dominate some seabird communities. Synthesis and applications. Reform of the Common Fisheries Policy and global discard declines are essential components towards creating sustainable fisheries, but may have both detrimental and beneficial effects on seabird communities. The nature of these impacts is still poorly understood, highlighting the need for detailed long-term seabird monitoring, as well as building resilience into populations through policy measures that incorporate remedial action on major seabird conservation priorities. Research should focus on understanding how seabird foraging, in terms of functional responses and searching behaviour, is influenced by both changing discards and natural fish prey availability, and how they impact upon fitness. It is also essential to link individual-level responses with population-, community- and ecosystem-level change. Understanding these links is fundamental to ongoing seabird management and conservation, and an ecosystem-based approach to fisheries management.
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Species extinctions are biased towards higher trophic levels, and primary extinctions are often followed by unexpected secondary extinctions. Currently, predictions on the vulnerability of ecological communities to extinction cascades are based on models that focus on bottom-up effects, which cannot capture the effects of extinctions at higher trophic levels. We show, in experimental insect communities, that harvesting of single carnivorous parasitoid species led to a significant increase in extinction rate of other parasitoid species, separated by four trophic links. Harvesting resulted in the release of prey from top-down control, leading to increased interspecific competition at the herbivore trophic level. This resulted in increased extinction rates of non-harvested parasitoid species when their host had become rare relative to other herbivores. The results demonstrate a mechanism for horizontal extinction cascades, and illustrate that altering the relationship between a predator and its prey can cause wide-ranging ripple effects through ecosystems, including unexpected extinctions.
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Chance per se plays a key role in ecology and evolution, e.g., genetic mutation, resource spatiotemporal unpredictability. In community ecology, chance is recognized as a key factor in community assemblage, but less is known about its role in intraguild processes leading to species coexistence. Here we study the relevance of resource unpredictability per se as a promoter of intraguild positive interspecific interactions and as a biodiversity enhancer in an Old World avian scavenger guild, which has evolved to feed upon spatially and temporally unpredictable resources, i.e., carcasses. We performed a large-scale field experiment in which 58 carcasses were disposed of and observed until complete consumption, either in continuously active supplementary feeding stations (predictable carcasses) or disposed of at random in the field (unpredictable carcasses). Richness of scavenger species was similar at unpredictable and predictable carcasses, but their relative abundances were highly uneven at predictable carcasses leading to higher scavenger diversity (Shannon index) at unpredictable carcasses. Facilitatory interspecific processes only occurred at unpredictable resources but were disrupted in predictable conditions because the dominant specialist species (in our case, the Griffon Vulture Gyps fulvus) arrived earlier and in larger numbers, monopolizing the resource. Small, endangered scavengers congregated at supplementary feeding stations but profited less compared to unpredictable carcasses, suggesting that they could constitute an ecological trap. Our findings offer new insights into the relevance of unpredictability of trophic resources in promoting both positive facilitatory interspecific interactions and species diversity and thus maintaining the function of guilds. Finally, the preservation of randomness in resource availability and the processes associated with its exploitation should be a major goal of conservation strategies aimed to preserve scavenger guilds evolved under naturally unpredictable trophic resources.
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Background: Optimal foraging theory predicts that animals will tend to maximize foraging success by optimizing search strategies. However, how organisms detect sparsely distributed food resources remains an open question. When targets are sparse and unpredictably distributed, a Lévy strategy should maximize foraging success. By contrast, when resources are abundant and regularly distributed, simple brownian random movement should be sufficient. Although very different groups of organisms exhibit Lévy motion, the shift from a Lévy to a brownian search strategy has been suggested to depend on internal and external factors such as sex, prey density, or environmental context. However, animal response at the individual level has received little attention. Methodology/principal findings: We used GPS satellite-telemetry data of Egyptian vultures Neophron percnopterus to examine movement patterns at the individual level during consecutive years, with particular interest in the variations in foraging search patterns during the different periods of the annual cycle (i.e. breeding vs. non-breeding). Our results show that vultures followed a brownian search strategy in their wintering sojourn in Africa, whereas they exhibited a more complex foraging search pattern at breeding grounds in Europe, including Lévy motion. Interestingly, our results showed that individuals shifted between search strategies within the same period of the annual cycle in successive years. Conclusions/significance: Results could be primarily explained by the different environmental conditions in which foraging activities occur. However, the high degree of behavioural flexibility exhibited during the breeding period in contrast to the non-breeding period is challenging, suggesting that not only environmental conditions explain individuals' behaviour but also individuals' cognitive abilities (e.g., memory effects) could play an important role. Our results support the growing awareness about the role of behavioural flexibility at the individual level, adding new empirical evidence about how animals in general, and particularly scavengers, solve the problem of efficiently finding food resources.
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The domestication of dogs was an important episode in the development of human civilization. The precise timing and location of this event is debated and little is known about the genetic changes that accompanied the transformation of ancient wolves into domestic dogs. Here we conduct whole-genome resequencing of dogs and wolves to identify 3.8 million genetic variants used to identify 36 genomic regions that probably represent targets for selection during dog domestication. Nineteen of these regions contain genes important in brain function, eight of which belong to nervous system development pathways and potentially underlie behavioural changes central to dog domestication. Ten genes with key roles in starch digestion and fat metabolism also show signals of selection. We identify candidate mutations in key genes and provide functional support for an increased starch digestion in dogs relative to wolves. Our results indicate that novel adaptations allowing the early ancestors of modern dogs to thrive on a diet rich in starch, relative to the carnivorous diet of wolves, constituted a crucial step in the early domestication of dogs.
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Unintended mortality in longlines emerged in the early 1990s as one of the most important threats for pelagic seabirds worldwide. Most of the studies were focused on highly developed industrial fisheries, overlooking bycatch in small-scale artisanal fisheries. However, bycatch in smallscale fisheries might have negative effects similar to those of industrial fisheries when they overlap with hotspot areas of top predators. Moreover, different types of fishing gear coexist in the same oceanographic area, particularly in highly exploited marine ecosystems such as the western Mediterranean. We quantify for the first time the influence of trawling regime on Cory's shearwater Calonectris diomedea bycatch in the western Mediterranean longline artisanal fishery. The availability of trawling discards has substantial influence on the foraging and breeding ecology of many seabirds, and trawling inactivity may drive shearwaters to seek alternative food resources, such as baits used in longline fishing. Based on our previous knowledge of the system, we also tested other variables affecting bycatch over 8 yr (1998 to 2005). Within this 2-fishery framework, we found that trawling regime, longline fishing time and breeding stage were key factors explaining shearwater attendance to longline vessels, but mainly trawling regime and fishing time increased the incidental capture of Cory's shearwaters. More specifically, during the pre-breeding and chick-rearing periods, bycatch dramatically increased during sunrise sets in the absence of trawling activity. Importantly, this study indicates the need for an integrated multi-fisheries management approach for the conservation of seabirds and highlights the necessity of banning longline fishing during periods of trawling inactivity.
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Feeding stations are commonly used to sustain conservation programs of scavengers but their impact on behaviour is still debated. They increase the temporal and spatial predictability of food resources while scavengers have supposedly evolved to search for unpredictable resources. In the Grands Causses (France), a reintroduced population of Griffon vultures Gyps fulvus can find carcasses at three types of sites: 1. “light feeding stations”, where farmers can drop carcasses at their farm (spatially predictable), 2. “heavy feeding stations”, where carcasses from nearby farms are concentrated (spatially and temporally predictable) and 3. open grasslands, where resources are randomly distributed (unpredictable). The impact of feeding stations on vulture’s foraging behaviour was investigated using 28 GPS-tracked vultures. The average home range size was maximal in spring (1272±752 km2) and minimal in winter (473±237 km2) and was highly variable among individuals. Analyses of home range characteristics and feeding habitat selection via compositional analysis showed that feeding stations were always preferred compared to the rest of the habitat where vultures can find unpredictable resources. Feeding stations were particularly used when resources were scarce (summer) or when flight conditions were poor (winter), limiting long-ranging movements. However, when flight conditions were optimal, home ranges also encompassed large areas of grassland where vultures could find unpredictable resources, suggesting that vultures did not lose their natural ability to forage on unpredictable resources, even when feeding stations were available. However during seasons when food abundance and flight conditions were not limited, vultures seemed to favour light over heavy feeding stations, probably because of the reduced intraspecific competition and a pattern closer to the natural dispersion of resources in the landscape. Light feeding stations are interesting tools for managing food resources, but don’t prevent vultures to feed at other places with possibly high risk of intoxication (poison).
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Foraging patterns, behaviour and the distribution of animals are affected by the availability and distribution of food in the landscape. Increasing numbers of ungulates may also be in conflict with agriculture, timber, infrastructure and conservation interests. Understanding foraging habits of ungulates and how these are affected by a change in forage availability or composition are, therefore, issues of major importance both from ecological and management perspectives. Supplementary feeding (i.e. artificial supply of food) is being used to improve local habitat, and thereby affecting ungulate movements, habitat choice and migration patterns. We experimentally tested the predictions that supplementary feeding redistributes moose Alces alces during two different migration phases (early, i.e. during the onset of migration and late, i.e. in the wintering areas). We used individually marked moose and pellet group counts to investigate the effect of supplementary feeding both at the individual and population level. We monitored 30 moose with GPS-collars before, during and after the supplementary feeding experiment, corresponding to 8-10% of the moose population in two different valleys in Northern Scandinavia. During early migration, moose ignored supplementary feeding sites even though migration routes were close to the sites. At the end of the migration route, supplementary feeding affected moose movement, distribution and behaviour. In conclusion, we suggest that there is a clear difference in response to supplementary feeding by moose due to the phase of migration. We conclude that supplementary feeding can be used under certain conditions to redistribute moose in relation to browsing, or to traffic, preferably at the endpoint of migration.
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Field-based food supplementation experiments can determine whether populations are limited by natural food availability. However, they may yield spurious results if added food is hoarded by dominants, exploited by immigrants, or delivered ineffectively. Surprisingly, population-level approaches accounting for these potential sources of bias have not been established. We explored responses of free-ranging snowshoe hares (Lepus americanus Erxleben, 1777) to food supplementation by contrasting per capita browsing rates on three study sites with added food with those on three control sites during two winters. Food augmentation reduced foraging pressure by hares this reduction was significant when browse species of high dietary importance were considered. By implication, hares on manipulated sites switched from favored natural foods to supplemental food, meaning that the extra food found its mark and was not heavily exploited by immigrants or hoarded by dominants. Demographic responses to food addition were not detected on the manipulated sites, indicating that the study population was not food limited. Given the success with which we detected the signal of supplementation and eliminated potential confounding factors, we suggest that future studies using food addition in the context of herbivore population dynamics would benefit from a more mechanistic approach this may involve measurement of browsing rates on manipulated and control sites.
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Biodiversity losses are increasing as a consequence of negative anthropogenic effects on ecosystem dynamics. However, the magnitude and complexity of these effects may still be greatly underestimated. Most Old World vultures have experienced rapid population declines in recent years. In Europe, their immediate conservation depends on changes in health regulations affecting the availability of food provided by domestic carcasses. Information is lacking on the effects of a hypothetical food shortage on the population dynamics of vultures, and is necessary to assess the potential impacts of policy decisions on future changes in biodiversity and ecosystem services. A novel computational model (P-systems) was used to model these effects, forecasting a rapid decline in the Eurasian griffon vulture (Gyps fulvus). By contrast, vulture species with greater plasticity in their dietary range appeared less sensitive to declining food availability. This study extends our understanding of vulture ecosystem services, which have social and economic implications.
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Biological invasions are a major environmental concern due to their negative impacts on biodiversity and economics. We determined the population sizes and habitat-abundance relationships of the three most successful invasive bird species in Singapore: the house crow Corvus splendens, white-vented myna Acridotheres javanicus and common myna A. tristis. Estimated population sizes of the three species between February 2000 and February 2001 were between 106 000-176 000, 122 000-155 000 and 20 000-29 000, respectively. Population size of the house crow grew dramatically (>30-fold) in the last 15-16 y while that of the white-vented and common myna declined. Habitat-abundance relationships suggest that house crows are highly dependent on anthropogenic food. Their abundance was also positively related to proximity to coast. The common myna associated closely with agricultural areas while the white-vented myna probably preferred urban greenery among residential buildings. Our study shows that the three invasive bird species associated with different aspects of human-modified environment.
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Between 1989 and 1999, the Spanish population of Griffon Vulture Gyps fulvus increased from 8,064 to 22,455 breeding pairs. This increase was not linked to any clear density-dependent process of population control given that the population grew more steadily in the more densely occupied sectors. This growth was related to a small increase in the breeding range of the species supporting the strong effect of the availability of nesting sites in limiting the range of the species. Around 85% of the breeding pairs were restricted to limestone sectors where cliffs suitable for breeding colonies were more abundant. In these limestone sectors, changes in the number of breeding pairs were positively correlated to changes in livestock abundance during 1989–1999, supporting a functional relationship between food availability and vulture abundance. Any active destruction of livestock carcasses to prevent the spread of some epidemic livestock diseases (e.g. bovine spongiform encephalopathy, African swine fever, foot and mouth disease) will probably produce a concomitant reduction of the Spanish population of Griffon Vulture.
Article
(1) We studied the population dynamics of snowshoe hares (Lepus americanus) in the Kluane Lake region of the Yukon by live-trapping nine areas year-round. We provided rabbit chow as winter food to three of these populations from September to May, 1977 to 1984. (2) Peak densities were reached in 1980 and 1981 on all areas except Jacquot Island. Two areas with extra winter food maintained densities three times that of their controls, while one food-supplemented area on Jacquot Island showed little effect of improved feeding on hare density. (3) Supplementary food did not prevent the cyclic decline and all areas reached low densities by 1984. The beginning of the decline was delayed 6 months on one food area but not delayed on the other. (4) The amplitude of the cycle was 141-fold based on spring numbers and 268-fold based on August numbers. This is considerably higher than the amplitudes measured in Minnesota and Alberta. (5) The hare cycle was caused by changes in recruitment (probably determined by losses during the first 8 weeks of life), juvenile survival in autumn, and adult survival in autumn. Survival rates gradually decreased during the cycle, and were lowest in its decline phase. (6) Extra winter food did not prevent the drop in survival that occurs during the decline phase of the hare cycle, nor did it prevent the low recruitment rate that occurs during the decline.
Article
(1) Voles on three areas were provided with different levels of extra food in the form of laboratory chow and oats for approximately one year. (2) On areas with intermediate and high extra food, population density increased to twice the control density. (3) Extra food increased immigration and reproduction, and shortened the winter non-breeding season. (4) Males and females had smaller home ranges on areas with extra food. This may have facilitated immigration to these populations. (5) Voles were removed from three other areas and re-colonization was measured. Immigration was related to the density of extra food; three times as many voles colonized a high food area compared with a control. (6) These results, combined with those of previous research which has shown that a viable surplus of voles exists in natural populations, suggest that the vole's population size is limited by both behaviour and food.
Article
Supplemental feeding of white-tailed deer (Odocoileus virginianus) has become an increasingly popular management activity, particularly on private lands. Raccoons (Procyon lotor) and other small carnivores are very attracted to deer feeders and are potential predators of ground-nesting birds such as wild turkeys. We tested the hypothesis that predation on artificial ground nests was greater near deer feeders due to the increased presence of nest predators. We selected 2 ponds and 2 artificial water sources (windmills with troughs) on the basis of habitat similarity. We provided supplemental food in the form of shelled corn at one of each of the pond and windmill sites during 1997, 1998, and 1999. At each site we placed 50 artificial nests (3 chicken eggs) along a 800- × 40-m transect centered on the water source. We monitored the fate of these nests over 28 days. We identified nest predators through patterns of eggshell breakage, hair traps, and automatic cameras. We analyzed nest survival using a logit model and by Kaplan-Meier survival analysis. Raccoons and striped skunks (Mephitis mephitis) were the most common predators of the artificial nests. In years with adequate ground cover to conceal the nests, presence of supplemental deer feeders at the site significantly decreased survivorship of the artificial nests. In dry years with sparse ground cover, nest survivorship was extremely poor at all sites. The lack of cover for the nests outweighed any deleterious effects of the deer feeders. Previous studies have suggested that supplementing predators may be a way to reduce nest predation; our results suggest the contrary. We suggest that managers concerned with production of wild turkeys (Meleagris gallopavo) and other ground-nesting birds should avoid placing deer feeders in nesting habitat or avoid supplemental feeding during the nesting season.
Article
1. Man has increased the input of carrion to marine communities worldwide through the practice of discarding fisheries-derived material. A large proportion of discarded material sinks to the sea bed and becomes available to benthic scavengers. Carrion from fisheries discards will subsidize marine food webs, which can sometimes result in the enhancement of consumer populations. 2. This study examines the benthic scavengers that feed on fisheries discards in three habitats in the Irish Sea. We investigated the relationship between the abundance of scavengers feeding on carrion in terms of numbers of each species and the density of those scavenger species in the surrounding area. 3. Observations with bailed time-lapse cameras at a site offshore From Anglesey showed that the hermit crab Pagurus bernhardus was attracted to carrion in greatest abundance and aggregated at densities of up to 330 m(-2). At Red Wharf Bag, a wider range of species was observed: starfish Asterias rubens, hermit crabs P. bernhardus, whelks Buccinum undatum and swimming crabs Liocarcinus spp. There was relatively little scavenging activity at the Walney Island site where the edible crab Cancer pagurus appeared to consume the greatest proportion of the carrion. 4. Numbers of each scavenger species at the bait were only partially related to the background population density of each species at each site. The rate of consumption of carrion varied between sites and could be related to the abundance of different scavenger species at the bait. 5. Baited traps were used to investigate those benthic scavengers that were too small to be observed by time-lapse photography. The traps caught a variety of amphipod and isopod species. Some species were habitat-specific, whereas others were ubiquitous, but specialized in eating a particular type of carrion; for example, Orchomene nanus, which was only caught in traps baited with crab. 6. The results demonstrated that the responses of scavengers to fisheries discards varied between different habitats. The responses of hermit crabs, P. bernhardus, were particularly variable, with large aggregations of individuals occurring at one site but not at others, despite similar background population densities.
Article
The aim of this study is to investigate vegetation changes on small Mediterranean islands under the impact of the drastic expansion of the gull colony, at local scale over eleven years using a set of permanent plots. First, we focused on functional aspects of vegetation in addition to its specific composition with regard to the plant functional types (Raunkiaer growth forms and Grime life strategies) as indicators of vegetation changes. Second, we used STATICO analysis to investigate patterns of change in the relationship between environmental variables and floristic composition. Third, we quantified the changes in the abundance of plant functional types by applying a simple comparison test between the two observation dates. Fourth, we investigated the relationship between vegetation changes (species turnover, plant functional type dynamics, and species richness) and gull density by performing simple linear regression. Our results show that gull density did not evolve equally for all plots. For areas where gull density increased, we recorded ruderalization of the vegetation. Surprisingly, in areas where there was a decrease in gull density, no clear pattern of vegetation change was apparent. We observed a statistically significant increase in the number of plant species due only to the increase in ruderal and stress ruderal and geophyte species. Gull colonies were responsible for high species turnover between 1997 and 2008. The higher the density of gulls, the lower the species number in 1997 and 2008. For high gull nest densities, we observed a high proportion of ruderal plant species and a low proportion of stress tolerant species. Gulls induced an increase of stress-ruderal species. We show that nest density recorded in 1997 is mainly responsible for the changes in vegetation composition, species turnover and proportions of plant functional types. We noted that a decrease in gull nest density does not necessarily induce a return to previous vegetation composition patterns. This may be seen as evidence of the inertial nature of the changes in island vegetation in the face of strong changes in environmental conditions such as the recent drastic expansion of gull colonies. Garbage management policy can have a strong and long-term impact on remote ecosystems.
Article
1. Wind farms are emerging as a major cause of mortality of large scavenging bird species, which may be catastrophic when they operate in concert with other threats. As a study model, we examine the impact of wind turbines on the population dynamics of a soaring bird species, when acting in conjunction with a sudden decrease in food availability following the European bovine spongiform encephalopathy (BSE) epidemic. 2. In Spain, vultures have been provided with supplementary food at traditional vulture restaurants for centuries. In 2006/2007, these feeding stations were closed as part of disease control measures. At the same time, wind farms were deployed within the vulture foraging range. We used capture–recapture data and direct observation to monitor the impacts of these changes on the vulture population. 3. The number of breeding pairs decreased by c. 24%, adult survival by 30% and fecundity by 35%. However, the population recovered as soon as the perturbations ceased, the vulture restaurants were reopened, and the most problematic wind turbines were closed. Population recovery was faster than predicted by a retrospective stochastic population model. 4. Our analyses indicate that fecundity and survival were influenced predominantly by wind turbines. Food scarcity promoted a shift in foraging behaviour that drove vultures to fly into the path of wind turbines as they sought out new food sources in a landfill site. Elasticity and sensitivity analyses of the population model showed that mortality of adult birds had a much greater effect on population declines than mortality of immature birds, whereas reduction in fecundity had negligible effects. 5. The most likely explanation for the rapid recovery of the vulture population is that the observed decline in breeding pairs was not solely because of increased mortality. The decline probably included dispersal away from the area and a greater incidence of skipped breeding during the perturbation years. Subsequent immigration from large nearby populations was probably a factor in population recovery. 6. Synthesis and applications . Where specific wind turbines are causing substantial mortality, their closure is an effective management response. For vulture populations dependent on supplemental feeding stations, the feeding sites should be relocated away from the most problematic wind turbines, or other anthropogenic sources of mortality, to prevent negative impacts. We recommend the establishment of scattered, low‐value food sources to replicate historical conditions and to avoid the problems associated with high concentrations of individuals in one place.
Article
Asymmetry in bilateral traits is often used to assess an individual's quality and stress resistance, but stress-induced variation in developmental stability is largely undocumented for free-living populations. Over many years, grizzly bears (Ursus arctos horribilis) extensively foraged around garbage dumps in Yellowstone National Park. Abrupt closure of these dumps 26 years ago was a severely stressful event and was followed by excessive mortality and a many-fold increase in grizzly home-range size. I examine how this stress affected developmental stability by comparing dentition of bears born before and after the dump closure. I predicted that (1) asymmetry in dentition should be greater in bears born after dump closure compared to before closure, and asymmetry in sexually selected canines should change more than nonsexually selected premolars following dump closure and (2) the relationship between tooth asymmetry and tooth size should change in the populations following the stressful events as compared with populations before stressful events. I found that developmental stability of canines, which are under directional sexual selection in males, was more responsive to stress compared to that of male premolars or female dentition (both under stabilizing selection), and, because of the increased cost of canine production, fewer animals were able to achieve both large size and symmetrical development of these teeth, and thus the slope of the relationship between fluctuating asymmetry and canine size increased. I conclude that stress appears to act as an honesty-reinforcement mechanism in sexual selection for symmetrical dentition.
Article
Climate change and fishing impact marine ecosystems, potentially modifying the availability of small pelagic fish to marine top predators. Some seabirds that primarily rely upon these resources have switched to feeding on fishery waste. It has therefore been argued that seabirds might become dependent upon this artificial resource. To test this hypothesis, we studied the foraging behaviour of Cape gannets Morus capensis breeding off the coast of South Africa using high-resolution Global Positioning System-tracking in relation to the availability of pelagic fish assessed by acoustic at-sea surveys, and fishing effort by the two main south African fisheries (purse seiners that compete with seabirds for pelagic fish, and demersal trawlers that process fish at sea and discharge fish waste) tracked with vessel monitoring systems. Conjoint seabird, fish and fisheries information were analysed at mesoscale (c. 100 km) and sub-mesoscale (c. 10 km) in years of high (2002), medium (2009) and low (2005) pelagic fish biomass within gannets' foraging range. We found substantial inter-annual variability in spatial use by breeding gannets, which was driven primarily by pelagic fish availability. At the mesoscale, birds and purse seiners exploited similar marine areas, but no fine-scale dependence of birds on purse seiners was detected. Crucially, fine-scale dependence of gannets upon trawlers producing fishery waste was only detected in 2005, when pelagic fish biomass was lowest, indicating a direct effect of trawlers on gannet foraging behaviour in the absence of natural prey. Further overlap analyses of gannet and trawler foraging areas during 2002–2010 confirmed that breeding birds only seek trawlers when pelagic fish availability is low, strongly suggesting reversible seabird dependency upon fishery waste. Synthesis and applications. Our study demonstrates that seabirds such as Cape gannets depend on fishery waste when their natural prey is scarce, but revert to feeding on natural resources whenever available, showing highly flexible foraging behaviour. These results have important implications in the context of the anticipated legislation banning at-sea disposal of fishery waste in different regions, including European seas, highlighting the necessity to concomitantly promote sustainable fishing allowing the restoration of pelagic fish stocks.
Article
Every year, millions of households provide huge quantities of supplementary food to wild birds. While alteration of the natural dynamics of food supply represents a major intervention in avian ecology, we have a remarkably limited understanding of the impacts of this widespread pastime. Here, we examine the many and varied responses of birds to supplementary feeding at backyard feeders - in large-scale management projects and in focused academic studies - and evaluate population responses to the bird-feeding phenomenon. Our review encompasses a wide range of species, from songbirds to raptors, and compares provisioning with a variety of foods, at different times of year and in different locations. We consider positive impacts, such as aiding species conservation programs, and negative ones, such as increased risk of disease transmission. It seems highly likely that natural selection is being artificially perturbed, as feeding influences almost every aspect of bird ecology, including reproduction, behavior, demography, and distribution. As the effects of bird feeding cascade through ecosystems and interact with processes of environmental change, we suggest areas for future research and highlight the need for large-scale experiments, with a particular focus on the backyards of an increasingly urban and generous, but sometimes fickle, human population.
Article
Omnivores have not figured prominently in our understanding of food webs and prey dynamics even though they can have substantial direct and indirect effects on the structure of ecological communities and on the dynamics of interacting species. The important role of omnivores is implicated by the paradoxical results of a food-supplementation experiment. The experiment was designed to test theories that predict how habitat change affects the distribution of habitat-selecting species. According to theories of habitat selection, a quantitative change in habitat (as caused by supplemental food) should increase consumer population size and alter habitat selectivity. Related theories of patch use predict that consumers should increase their use of enriched patches. A two-year experiment on two species of small mammals in Canada's boreal forest failed to alter population densities of red-backed voles, but did cause a dramatic shift in vole habitat use. Rather than increasing their use of feeding stations as predicted by classical theory, voles avoided them. Deer mice did not respond to the experimental treatments. The paradoxical results occurred because omnivorous black bears altered prey behavior by increasing predation risk at feeding stations. Revised theory confirms the indirect omnivore effect, and demonstrates that the behavioral paradox is far more likely for omnivores than for other types of predators. The behavioral paradox of enrichment highlights not only important new, and potentially stabilizing, roles for omnivores, but also the pervasive influences of behavior and habitat selection on population dynamics and regulation.
Article
Forcibly removing species from ecosystems has important consequences for the remaining assemblage, leading to changes in community structure, ecosystem functioning and secondary (cascading) extinctions. One key question that has arisen from single- and multi-trophic ecosystem models is whether the secondary extinctions that occur within competitive communities (guilds) are also important in multi-trophic ecosystems? The loss of consumer–resource links obviously causes secondary extinction of specialist consumers (topological extinctions), but the importance of secondary extinctions in multi-trophic food webs driven by direct competitive exclusion remains unknown. Here I disentangle the effects of extinctions driven by basal competitive exclusion from those caused by trophic interactions in a multi-trophic ecosystem (basal producers, intermediate and top consumers). I compared food webs where basal species either show diffuse (all species compete with each other identically: no within guild extinctions following primary extinction) or asymmetric competition (unequal interspecific competition: within guild extinctions are possible). Basal competitive exclusion drives extra extinction cascades across all trophic levels, with the effect amplified in larger ecosystems, though varying connectance has little impact on results. Secondary extinction patterns based on the relative abundance of the species lost in the primary extinction differ qualitatively between diffuse and asymmetric competition. Removing asymmetric basal species with low (high) abundance triggers fewer (more) secondary extinctions throughout the whole food web than removing diffuse basal species. Rare asymmetric competitors experience less pressure from consumers compared to rare diffuse competitors. Simulations revealed that diffuse basal species are never involved in extinction cascades, regardless of the trophic level of a primary extinction, while asymmetric competitors were. This work highlights important qualitative differences in extinction patterns that arise when different assumptions are made about the form of direct competition in multi-trophic food webs.
Article
Tipping points - where systems shift radically and potentially irreversibly into a different state - have received considerable attention in ecology. Although there is convincing evidence that human drivers can cause regime shifts at local and regional scales, the increasingly invoked concept of planetary scale tipping points in the terrestrial biosphere remains unconfirmed. By evaluating potential mechanisms and drivers, we conclude that spatial heterogeneity in drivers and responses, and lack of strong continental interconnectivity, probably induce relatively smooth changes at the global scale, without an expectation of marked tipping patterns. This implies that identifying critical points along global continua of drivers might be unfeasible and that characterizing global biotic change with single aggregates is inapt.
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1. The large amount of discards produced by commercial fisheries can have major impacts on marine predator populations: this abundant food may increase populations of some scavengers or decrease others via accidental bycatch. Yet, despite the conservation implications of discard practices, the ecology of individual scavengers is poorly understood. 2. Here, we assess the influence of commercial fisheries' activity on the foraging behaviour of individual breeding northern gannets Morus bassanus. Using recent developments in stable isotope mixing models (Stable Isotope Analysis in R or SIAR) we estimate individual discard consumption. Using GPS tracking and the Vessel Monitoring System (VMS), we investigate behavioural responses to trawlers. 3. Analysis of conventional diet samples, as well as stable isotope ratios of carbon and nitrogen in blood (plasma and cells), highlight marked individual differences in the proportion of fishery discards in the diet. Individual differences in foraging behaviour revealed by stable isotopes show evidence of both short-term consistency and behavioural flexibility. 4. At-sea path tortuosity of 25 gannets (tracked using GPS loggers) revealed scale-dependent adjustments in response to VMS-derived fishing vessel locations, as well as to sea surface tempera-ture, chlorophyll a concentration and copepod abundance. The results also indicate individual variability in behavioural response to trawlers. 5. Individual differences in the amount of discards estimated from SIAR were negatively correlated with differences in foraging trip length and body condition, indicating potential fitness consequences. 6. Synthesis and applications. The management of commercial fisheries and apex predators is a daunting task. Ultimately, reducing bycatch and removing dependency on discards remain key conservation priorities, but managers should also ensure that scavenging species have sufficient alternative food to meet their energetic needs, to ameliorate potential unforeseen knock-on consequences. The results of Stable Isotope Analysis (SIAR) reveal intra-population differences in discard consumption by gannets; differences that have impacts on foraging effort and body condi-tion. The use of GPS tracking and Vessel Monitoring Systems (VMS) reveal that gannet at-sea behaviour is influenced by fishing vessels, although this also varies among individuals. A combina-tion of SIAR, GPS tracking and VMS can be used to study fishery ⁄ scavenger interactions in detail at the individual level, to answer fundamental questions about scavenging behaviour.
Article
The exogenous input of nutrients and energy into island systems fuels a large array of consumers and drives bottom-up trophic cascades in island communities. The input of anthropogenic resources has increased on islands and particularly supplemented non-native consumers with extra resources. We test the hypothesis that the anthropogenic establishments of super-abundant gulls and invasive iceplants Carpobrotus spp. have both altered the dynamics of an introduced black rat Rattus rattus population. On Bagaud Island, two habitats have been substantially modified by the anthropogenic subsidies of gulls and iceplants, in contrast to the native Mediterranean scrubland with no anthropogenic inputs. Rats were trapped in all three habitats over two contrasting years of rainfall patterns to investigate: (1) the effect of anthropogenic subsidies on rat density, age-ratio and growth rates, and (2) the role of rainfall variability in modulating the effects of subsidies between years. We found that the growth rates of rats dwelling in the non-subsidized habitat varied with environmental fluctuation, whereas rats dwelling in the gull colony maintained high growth rates during both dry and rainy years. The presence of anthropogenic subsidies apparently mitigated environmental stress. Age ratio and rat density varied significantly and predictably among years, seasons, and habitats. While rat densities always peaked higher in the gull colony, especially after rat breeding in spring, higher captures of immature rats were recorded during the second year in all habitats, associated with higher rainfall. The potential for non-native rats to benefit from anthropogenic resources has important implications for the management of similar species on islands.
Article
Heavy herbivory by ungulates can substantially alter habitat, but the indirect consequences of habitat modification for animal assemblages that rely on that habitat are not well studied. This is a particularly important topic given that climate change can alter plant–herbivore interactions. We explored short‐term responses of small mammal communities to recent exclusion of R ocky M ountain elk ( C ervus elaphus ) in high‐elevation riparian drainages in northern Arizona, where elk impacts on vegetation have increased over the past quarter century associated with climate change. We used 10‐ha elk exclosures paired with unfenced control drainages to examine how browsing influenced the habitat use, relative abundance, richness and diversity of a small mammal assemblage. We found that the small mammal assemblage changed significantly after 5 years of elk exclusion. Relative abundance of voles ( M icrotus mexicanus ) increased in exclosure drainages, likely due to an increase in habitat quality. The relative abundances of woodrats ( N eotoma neomexicana ) and two species of mice ( P eromyscus maniculatus and P . boylii ) decreased in the controls, while remaining stable in exclosures. The decline of mice in control drainages was likely due to the decline in shrub cover that they use. Thus, elk exclusion may have maintained or improved habitat for mice inside the exclosures while habitat quality and mouse abundance both declined outside the fences. Finally, small mammal species richness increased in the exclosures relative to the controls while species diversity showed no significant trends. Together, our results show that relaxation of heavy herbivore pressure by a widespread native ungulate can lead to rapid changes in small mammal assemblages. Moreover, exclusion of large herbivores can yield rapid responses by vegetation that may enhance or maintain habitat quality for small mammal populations.
Article
Supplementary feeding studies are widely used to assess the effects of food availability on herbivore population dynamics. Supplementary feeding studies make the implicit and often untested assumption that supplementary feed is used by the target population. Here we describe and present the results of a supplementary feeding experiment to assess the effects of over-winter food availability on mountain hare Lepus timidus body condition, fecundity and survival in two fed and two control areas. We used passive induced transponder (PIT) tags and feeding stations equipped with PIT tag readers and data loggers to monitor individual use of supplementary feed. Fifty per cent, of 119 PIT-tagged hares, which were resident on the fed areas, used food, but individual variation in the time spent feeding was large. Food supplementation was associated with greater male body mass, earlier breeding, higher fecundity and longer survival. At the population (treatment) level these differences were not statistically significant. At the individual level the combined radio-telemetry and PIT tag data revealed a large and highly significant effect of supplementary feeding on survival. Recent syntheses of mountain hare population ecology have not identified food as a key factor determining dynamics. Our experimental study however demonstrates that food may have profound effects on individuals. In addition our study raises critical questions about the design and interpretation of supplementary feeding studies.
Article
Abstract Predators can have strong indirect effects on plants by altering the way herbivores impact plants. Yet, many current evaluations of plant species diversity and ecosystem function ignore the effects of predators and focus directly on the plant trophic level. This report presents results of a 3-year field experiment in a temperate old-field ecosystem that excluded either predators, or predators and herbivores and evaluated the consequence of those manipulations on plant species diversity (richness and evenness) and plant productivity. Sustained predator and predator and herbivore exclusion resulted in lower plant species evenness and higher plant biomass production than control field plots representing the intact natural ecosystem. Predators had this diversity-enhancing effect on plants by causing herbivores to suppress the abundance of a competitively dominant plant species that offered herbivores a refuge from predation risk.