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Synurbanization. Synurbanization refers to the adaptation of wildlife to urban environments (reviewed by Luniak 2004). The study of synurbanization has grown recently, as we try to tease apart the degree to which phenotypic plasticity and microevolutionary processes leading to divergent selection contribute to changes in animals under human-altered conditions. The creation of a new urban ecosystem has benefitted some animals, namely small mammals and birds. These species have adjusted to urban pressures through higher population densities, reduced migratory behavior, prolonged breeding seasons, greater longevity, prolonged circadian rhythms, and changes in feeding behavior (as listed in Luniak 1996). For example, many birds benefit from supplementary feeding in urban areas, leading to earlier lay dates, larger clutches and chicks, and higher hatching and fledging success (reviewed in Robb et al. 2008). Top-down processes may also affect these species, as predation pressure may be reduced when predators shift their diet to anthropogenic sources (Rodewald et al. 2011; Stracey 2011). More omnivorous species can mitigate the costs of searching for and killing live prey by modifying their behavior to depend on anthropogenic food, a trend that is becoming increasingly apparent for coyotes, raccoons, and black bears (Prange et al. 2003; Gehrt 2007). Urban populations also tend to be more aggressive, take more risks, are less neophobic, are more exploratory/bold and have reduced escape behaviors compared to rural populations (Miranda et al. 2013; Sih et al. 2012). These personality traits can be linked to fitness: bolder and more aggressive individuals have greater reproductive success, and exploratory individuals have higher survival (Smith and Blumstein 2008), suggesting these personality traits are beneficial when inhabiting a novel and risky urban environment. The home ranges of both bats (Gehrt and Chelsvig 2003) and coyotes (Canis latrans) (McClennen et al. 2001, Grubbs and Krausman 2009) did not differ between fragmented and unfragmented habitats, and both species used human-generated corridors during travel, suggesting that species which can persist in urban environments (i.e., synanthropes, Gerht et al. 2011) are able to adjust their behavior to habitat fragmentation and human activities. Studies integrating bottom-up and top-down ecological interactions with behaviour and physiology and linking these traits with fitness are sorely needed, as the sublethal consequences of urban modifications are both acute and chronic. (a) A fox (Vulpes vulpes) is walking in a residential area at night, and (b) a grey heron (Ardea cinerea) has acquired food from a local street vendor in Amsterdam. Images by Sam Hobson. [Colour online.]  

Synurbanization. Synurbanization refers to the adaptation of wildlife to urban environments (reviewed by Luniak 2004). The study of synurbanization has grown recently, as we try to tease apart the degree to which phenotypic plasticity and microevolutionary processes leading to divergent selection contribute to changes in animals under human-altered conditions. The creation of a new urban ecosystem has benefitted some animals, namely small mammals and birds. These species have adjusted to urban pressures through higher population densities, reduced migratory behavior, prolonged breeding seasons, greater longevity, prolonged circadian rhythms, and changes in feeding behavior (as listed in Luniak 1996). For example, many birds benefit from supplementary feeding in urban areas, leading to earlier lay dates, larger clutches and chicks, and higher hatching and fledging success (reviewed in Robb et al. 2008). Top-down processes may also affect these species, as predation pressure may be reduced when predators shift their diet to anthropogenic sources (Rodewald et al. 2011; Stracey 2011). More omnivorous species can mitigate the costs of searching for and killing live prey by modifying their behavior to depend on anthropogenic food, a trend that is becoming increasingly apparent for coyotes, raccoons, and black bears (Prange et al. 2003; Gehrt 2007). Urban populations also tend to be more aggressive, take more risks, are less neophobic, are more exploratory/bold and have reduced escape behaviors compared to rural populations (Miranda et al. 2013; Sih et al. 2012). These personality traits can be linked to fitness: bolder and more aggressive individuals have greater reproductive success, and exploratory individuals have higher survival (Smith and Blumstein 2008), suggesting these personality traits are beneficial when inhabiting a novel and risky urban environment. The home ranges of both bats (Gehrt and Chelsvig 2003) and coyotes (Canis latrans) (McClennen et al. 2001, Grubbs and Krausman 2009) did not differ between fragmented and unfragmented habitats, and both species used human-generated corridors during travel, suggesting that species which can persist in urban environments (i.e., synanthropes, Gerht et al. 2011) are able to adjust their behavior to habitat fragmentation and human activities. Studies integrating bottom-up and top-down ecological interactions with behaviour and physiology and linking these traits with fitness are sorely needed, as the sublethal consequences of urban modifications are both acute and chronic. (a) A fox (Vulpes vulpes) is walking in a residential area at night, and (b) a grey heron (Ardea cinerea) has acquired food from a local street vendor in Amsterdam. Images by Sam Hobson. [Colour online.]  

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Urbanization is modifying previously pristine natural habitats and creating "new" ecosystems for wildlife. As a result, some animals now use habitat fragments or have colonized urban areas. Such animals are exposed to novel stimuli that they have not been exposed to in their evolutionary history. Some species have adapted to the challenges they fac...

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... Taking an evolutionary perspective, the niches occupied by species have been growing broader. The earliest organisms were likely similar to the hydrothermal bacteria, while at the present time, many species are forced to broaden their niches due to human behaviour (Luniak 2004;Birnie-Gauvin et al. 2016). We suggest that an important driver for niche broadening is resource depletion. ...
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This paper argues that intelligence can be approximated by the ability to produce accurate predictions. It is further argued that general intelligence can be approximated by context dependent predictive abilities combined with the ability to use working memory to abstract away contextual information. The flexibility associated with general intelligence can be understood as the ability to use selective attention to focus on specific aspects of sensory impressions to identify patterns, which can then be used to predict events in novel situations and environments. The argumentation synthesizes Godfrey-Smith’s environmental complexity theory, adding the notion of niche broadness as well as changes concerning the view of cognition and control, and Hohwy’s predictive mind theory, making explicit the significance of accuracy as a composite of trueness and precision where the nervous system acts as a distributed controller motivating actions that keep the body in homeostasis.
... For this reason, understanding whether these species can adapt and persist within modern city-scapes has become an urgent priority among ecologists and conservationists today (e.g. Birnie-Gauvin et al. 2016;Ouyang et al. 2018). ...
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Urbanisation can alter local microclimates, thus creating new thermal challenges for resident species. However, urban environments also present residents with frequent, novel stressors (e.g., noise, human interaction) which may demand investment in costly, self-preserving responses (e.g., the fight-or-flight response). One way that urban residents might cope with this combination of demands is by using regional heterothermy to reduce costs of thermoregulation during the stress response. In this study, we used black-capped chickadees (nurban = 9; nrural = 10) to test whether known heterothermic responses to stress exposure (here, at the bare skin around the eye): (1) varied consistently among individuals (i.e., were repeatable), and (2) were most pronounced among urban individuals compared with rural individuals. Further, to gather evidence for selection on stress-induced heterothermic responses in urban settings, we tested: (3) whether repeatability of this response was lower among birds sampled from urban environments compared with those sampled from rural environments. For the first time, we show that heterothermic responses to stress exposures (i.e. changes in body surface temperature) were highly repeatable across chronic time periods (R = 0.58) but not acute time periods (R = 0.13). However, we also show that these responses did not differ between urban and rural birds, nor were our repeatability estimates any lower in our urban sample. Thus, while regional heterothermy during stress exposure may provide energetic benefits to some, but not all, individuals, enhanced use of this response to cope with urban pressures appears unlikely in our study species.
... Animals inhabiting urban environments must cope with anthropogenic light and noise, increased exposure to toxicants, altered predator and prey communities, and shifts in disease exposure (Marzluff, 2001;Isaksson, 2018). While some animals are able to thrive under these conditions (i.e., "urban exploiters"; Blair, 1996;McKinney, 2006), there is an underlying assumption that inhabiting urban habitats is costly for most individuals (Birnie-Gauvin et al., 2016;Murray et al., 2019). Several studies have examined the physiological and fitness consequences of urbanization by comparing urban and rural dwelling birds within species and found urban birds exhibit lower body condition (Capilla-Lasheras et al., 2017;Murray et al., 2019) and reduced reproductive success (Chatelain et al., 2021). ...
Article
A central theme in the field of ecology is understanding how environmental variables influence a species’ distribution. In the last 20 years, there has been particular attention given to understanding adaptive physiological traits that allow some species to persist in urban environments. However, there is no clear consensus on how urbanization influences physiology, and it is unclear whether physiological differences in urban birds are directly linked to adverse outcomes or are representative of urban birds adaptively responding to novel environmental variables. Moreover, though low-density suburban development is the fastest advancing form of urbanization, most studies have focused on animals inhabiting high intensity urban habitats. In this study, we measured a suite of physiological variables that reflect condition and immune function in male song sparrows ( Melospiza melodia ) from rural and suburban habitats. Specifically, we measured hematological indices [packed cell volume (PCV), hemoglobin concentration, mean corpuscular hemoglobin concentration (MCHC)], circulating glutathione (total, reduced, and oxidized), oxidative damage (d-ROM concentration), antioxidant capacity, and components of the innate immune system [bacteria killing ability (BKA), white blood cell counts]. We also measured whole-animal indices of health, including body condition (scaled mass index length) and furcular fat. Song sparrows inhabiting suburban environments exhibited lower hemoglobin and MCHC, but higher body condition and furcular fat scores. Additionally, suburban birds had higher heterophil counts and lower lymphocyte counts, but there were no differences in heterophil:lymphocyte ratio or BKA between suburban and rural birds. PCV, glutathione concentrations, and oxidative damage did not differ between suburban and rural sparrows. Overall, suburban birds did not exhibit physiological responses suggestive of adverse outcomes. Rather, there is some evidence that sparrows from rural and suburban habitats exhibit phenotypic differences in energy storage and metabolic demand, which may be related to behavioral differences previously observed in sparrows from these populations. Furthermore, this study highlights the need for measuring multiple markers of physiology across different types of urban development to accurately assess the effects of urbanization on wildlife.
... Wildlife living in urban environments are presented with a series of environmental hazards, from loss of habitat and food resources to higher levels of pollution and other stressors (e.g. vehicular and pedestrian traffic), ultimately reducing fitness and survival for many species (Grimm et al. 2008;Isaksson 2015;Birnie-Gauvin et al. 2016;Parris 2016). The loss of biodiversity in cities could deprive human urban dwellers from the well-known physical and mental health benefits associated with nature interaction, such as better health, lower stress levels and low mental distress (Bratman et al. 2019;Miller 2005;Soga & Gaston 2020). ...
... Native non-volant mammals, particularly canopy dwelling species, could be considered the most adversely impacted by urbanization and associated hazards such as increased mortality from vehicle collisions and electrocution (Gordo et al. 2013;Rodewald & Gehrt 2014;Correa et al. 2018), and they could be particularly prone to local extinction if unable to cross and move around the surrounding urban matrix (Andren 1994;Birnie-Gauvin et al. 2016). However, studies on non-volant mammals that live in cities are limited and most of these studies are restricted to temperate and subtropical regions (Magle et al. 2012;McDonnell & Hahs 2008;Magle et al. 2019;Schnetler et al. 2020). ...
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City life is harsh and inhospitable for many animal species, particularly for non-volant mammals that face increased mortality risks in urban settings. Yet, studies on non-volant city mammals are limited and mostly restricted to temperate regions. Here, I evaluated the density and adaptability of the common marmoset (Callithrix jacchus), a species with a series of advantageous pre-adaptations that could facilitate city life, in highly built up urban environments of a tropical city Joao Pessoa (>800,000 people), in NE Brazil. I surveyed a total of 56 streets from seven randomly chosen districts within the city. I used multiple linear regression to determine the factors that could influence marmoset abundance. I found a total of 53 tree species of which half could be used as food resources. To reach food resources marmosets moved along and crossed streets using insulated power lines and phone cables. Marmoset density (66.9 ind/km2) was significantly low compared to populations inhabiting forest remnants. Nevertheless, along streets with high canopy cover, their density was similar to that reported for forest fragments. Canopy cover and trees providing food resources were key predictors of marmoset abundance. The presence of an exotic tree species (Terminalia catappa) that provides gum, showed to be key for groups persisting in extremely urbanized areas. Planting more of this species and increasing connectivity between forested areas are management strategies that might help long term persistence of marmosets in highly built up areas. Marmosets are common in Brazilian cities and could provide opportunities for contact with nature and increased well-being of human urban dwellers.
... through direct mortality (Fahrig & Rytwinski, 2009): small mammals and birds have increased mortality rates due to domestic cats (Loss et al., 2013), and roads account for a large portion of mortality for some mammal species (e.g., mountain lions ;Schwab & Zandbergen, 2011;Vickers et al., 2015). Negative impacts of urbanization are sometimes sublethal and difficult to detect, particularly when wildlife populations persist in an area rather than experiencing large declines in population size or local extinction (Birnie-Gauvin et al., 2016;Giraudeau et al., 2014;Valcarcel & Fernández-Juricic, 2009;Zanette et al., 2011). In some cases, wildlife respond to disturbances from vehicles, humans, and domestic animals as a perceived risk or as a perceived competitor, spending time and energy responding to these disturbances instead of foraging (Shier et al., 2012;Valcarcel & Fernández-Juricic, 2009;Zanette et al., 2011). ...
... Evidence from a variety of species indicates that urbanization can lead to decreased body condition (Hellgren & Polnaszek, 2011;Lomas et al., 2015;Murray et al., 2019;Ware et al., 2015). In addition, anthropogenic food sources are sometimes of relatively low nutritional quality, which may place wildlife in a nutrient-deficient state and influence maintenance and reproductive capability (Birnie-Gauvin et al., 2016;Oro et al., 2013;Plummer et al., 2013). Further, wildlife that are infected with parasites can have decreased body condition as compared to non-infected animals (Debeffe et al., 2016;Stien et al., 2002;Vandegrift et al., 2008). ...
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Abstract Urban development can fragment and degrade remnant habitat. Such habitat alterations can have profound impacts on wildlife, including effects on population density, parasite infection status, parasite prevalence, and body condition. We investigated the influence of urbanization on populations of Merriam's kangaroo rat (Dipodomys merriami) and their parasites. We predicted that urban development would lead to reduced abundance, increased parasite prevalence in urban populations, increased probability of parasite infection for individual animals, and decreased body condition of kangaroo rats in urban versus wildland areas. We live trapped kangaroo rats at 5 urban and 5 wildland sites in and around Las Cruces, NM, USA from 2013 to 2015, collected fecal samples from 209 kangaroo rats, and detected endoparasites using fecal flotation and molecular barcoding. Seven parasite species were detected, although only two parasitic worms, Mastophorus dipodomis and Pterygodermatites dipodomis, occurred frequently enough to allow for statistical analysis. We found no effects of urbanization on population density or probability of parasite infection. However, wildland animals infected with P. dipodomis had lower body condition scores than infected animals in urban areas or uninfected animals in either habitat. Our results suggest that urban environments may buffer Merriam's kangaroo rats from the detrimental impacts to body condition that P. dipodomis infections can cause.
... Even when these recreational areas can attract gulls by human refuse, these resources could be scarcer than in urban areas but more valuable, increasing agonistic behaviors and displaying territorial reactions against potential competitors more frequently. In contrast, synanthropic species in urban areas modify their natural behavior, reducing dispersal and migratory patterns besides decreasing intraspecific aggression and competence [41,42], especially in opportunistic gull species [37,43]. In light of the results, the use of drones could be considered as safe and viable in coastal central urban areas, increasing risks of L. livens aggressive reactions in recreational coastal spots apart from the city. ...
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The use of drones has expanded the boundaries of several activities, which is expected to be utilized intensively in the near future. Interactions between urbanity and naturalness have been increasing while urban expansion amplifies the proximity between urban and natural areas. In this scenario, the interactions between drones and fauna could be augmented. Therefore, the aim of this study was to depict and evaluate the responses of the opportunistic and territorial seagull Larus livens to a small-sized drone during the non-breeding stage in urban areas and natural surroundings. The results evidenced that gulls do not react to drone sounds, coloration, or distance between them and the drone take-off spot. Clearly, the take-off vertical movement triggers an agonistic behavior that is more frequent in groups conformed by two adults, evidencing some kind of territorial response against the device, expressed as characteristic mobbing behavior. Thus, adult settled gulls in touristic and non-urbanized areas displayed agonistic behavior more frequently against the drone. Despite the coastal urban area being a free interaction environment, it evidences a low risk between drone management and territorial seabirds.
... Nonetheless, urban environments are also ecosystems and are increasingly recognized for their biodiversity structure and function (Savard et al., 2000). These novel ecosystems create opportunities for wildlife (Kowarik, 2011) but there can be negative consequences (Birnie-Gauvin et al., 2016). For example, urban racoons scavenge human trash that can cause physiological alterations in racoons (Schulte-Hostedde et al., 2018). ...
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Environmental change and biodiversity loss are but two of the complex challenges facing conservation practitioners and policy makers. Relevant and robust scientific knowledge is critical for providing decision-makers with the actionable evidence needed to inform conservation decisions. In the Anthropocene, science that leads to meaningful improvements in biodiversity conservation, restoration and management is desperately needed. Conservation Physiology has emerged as a discipline that is well-positioned to identify the mechanisms underpinning population declines, predict responses to environmental change and test different in situ and ex situ conservation interventions for diverse taxa and ecosystems. Here we present a consensus list of 10 priority research themes. Within each theme we identify specific research questions (100 in total), answers to which will address conservation problems and should improve the management of biological resources. The themes frame a set of research questions related to the following: (i) adaptation and phenotypic plasticity; (ii) human–induced environmental change; (iii) human–wildlife interactions; (iv) invasive species; (v) methods, biomarkers and monitoring; (vi) policy, engagement and communication; (vii) pollution; (viii) restoration actions; (ix) threatened species; and (x) urban systems. The themes and questions will hopefully guide and inspire researchers while also helping to demonstrate to practitioners and policy makers the many ways in which physiology can help to support their decisions.
... Given the extensive evidence published on the negative effects of urbanization on many taxonomic groups (Chace and Walsh, 2006;Aronson et al., 2014;Birnie-Gauvin et al., 2016), we can expect that overall, urban habitats are functioning more as ecological traps than as safe habitats for organisms. However, it is possible that, for a limited set of urban tolerant species, urban habitats can be operating as safe habitats. ...
Article
Urban areas represent a spectrum that goes from being safe habitats for biodiversity (i.e., habitats more or equally preferred, without costs to fitness) to being ecological traps (i.e., habitats more or equally preferred, but with costs to fitness). Given the imminent urban expansion, it is valuable to assess how biodiversity is responding to urbanization and thus generate timely conservation strategies. We systematically review the urban ecology literature to analyze how much do we know about the role of urban areas as ecological traps. Using a formal meta-analytical approach, we test whether urban areas are functioning as ecological traps or as safe habitats for different taxonomic groups. We generated a data set of 646 effect sizes of different measures of habitat preferences and fitness from 38 papers published between 1985 and 2020. The data set covered 15 countries and 47 urban areas from four continents, including 29 animal species. Studies from North America and Europe were best represented, and birds were the most studied taxa. Overall, the meta-analysis suggests that urbanized habitats are functioning more as safe sites than as ecological traps, mainly for certain species with characteristics that have allowed them to adapt well to urban areas. That is, many of the studied species prefer more urbanized habitats over other less urbanized sites, and their fitness is not modified, or it is even increased. However, there was high heterogeneity among studies. We also performed meta-regressions to identify variables accounting for this heterogeneity across studies and we demonstrate that outcomes may depend on methodological aspects of studies, such as study design or the approach used to measure habitat preference and fitness. More research is needed for poorly studied regions and on a wider range of species before generalizations can be made on the role of urban areas for biodiversity conservation.
... Many urban animals, however, suffer serious predation by human companion animals such as owned or feral cats and dogs [14][15][16] . As for parasitism, animals living in urban areas often have poorer body conditions 17,18 , are exposed to higher levels of environmental contaminants 19 , and can experience higher population densities 20 , all of which could enhance parasitic infections 21 . Indeed, some urban populations of lizards 22 , birds 23 and rodents 24 have higher levels of parasitic infections compared to nonurban populations. ...
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Studying animals in urban environments is especially challenging because much of the area is private property not easily accessible to professional scientists. In addition, collecting data on animals that are cryptic, secretive, or rare is also challenging due to the time and resources needed to amass an adequate dataset. Here, we show that community science can be a powerful tool to overcome these challenges. We used observations submitted to the community science platform iNaturalist to assess predation and parasitism across urbanization gradients in a secretive, ‘hard-to-study’ species, the Southern Alligator Lizard ( Elgaria multicarinata ). From photographs, we quantified predation risk by assessing tail injuries and quantified parasitism by counting tick loads on lizards. We found that tail injuries increased with age and with urbanization, suggesting that urban areas are risky habitats. Conversely, parasitism decreased with urbanization likely due to a loss of hosts and anti-tick medications used on human companion animals. This community science approach generated a large dataset on a secretive species rapidly and at an immense spatial scale that facilitated quantitative measures of urbanization (e.g. percent impervious surface cover) as opposed to qualitative measures (e.g. urban vs. rural). We therefore demonstrate that community science can help resolve ecological questions that otherwise would be difficult to address.
... However, studies on the effect of supplementary feeding in wildlife have also shown that long-term feeding practices can lead to reliance on supplemented food, habituation to humans, disruption of normal activities and nutritional problems such as metabolic diseases including obesity (Murray et al., 2016;Newsome and Rodger, 2008). The consumption of anthropogenic food could expose the urban individuals to pollutants, poisons or toxins from human waste (Birnie-Gauvin et al., 2016;Murray et al., 2016), as already reported in wild boars from Barcelona (Alabau et al., 2020). Furthermore, aggregating around feeding locations may also increase pathogen transmission (Becker et al., 2015;Bradley and Altizer, 2007;Murray et al., 2016;Wang et al., 2019). ...
Article
Urbanisation is a global human-induced environmental change and one of the most important threats to biodiversity. To survive in human-modified environments, wildlife must adjust to the challenging selection pressures of urban areas through behaviour, morphology, physiology and/or genetic changes. Here we explore the effect of urbanisation in a large, highly adaptable and generalist urban adapter species, the wild boar (Sus scrofa, Linnaeus 1758). From 2005 to 2018, we gathered wild boar data and samples from three areas in NE Spain: one urban (Barcelona municipality, n = 445), and two non-urban (Serra de Collserola Natural Park, n = 183, and Sant Llorenç del Munt i Serra de l’Obac Natural Park, n = 54). We investigated whether urbanisation influenced wild boar body size, body mass, body condition, and the concentration of serum metabolites, considering also the effect of age, sex and use of anthropogenic food resources. Wild boars from the urban area had larger body size, higher body mass, better body condition, and a higher triglyceride and lower creatinine serum concentrations than non-urban wild boars. In addition, urban wild boars consumed food from anthropogenic origin more frequently, which suggests that differences in their diet probably induced the biometric and the metabolic changes observed. These responses are probably adaptive and suggest that wild boars are thriving in the urban environment. Our results show that urbanisation can change the morphological and physiological traits of a large mammal urban adapter, which may have consequences in the ecology and response to urban selection pressures by the species. The phenotypic plasticity shown by wild boars provides both further and new evidence on the mechanisms that allow urban adapter species of greater size to respond to urbanisation, which is expected to continue growing globally over the coming decades.