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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.]
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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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... Yet, some animals can survive and 34 even thrive in urban environments, exploiting new human-provided resources for foraging and 35 roosting [3]. However, tolerance and adaptation to these human-modified environments may 36 put wildlife under considerable chronic stress [4,5] and deleteriously affect animal health by 37 altering the body condition, immune function and shifting microbiome composition [6][7][8][9][10][11]. This 38 may thereby increase susceptibility to infections and exacerbate the natural shedding of 39 infectious agents in human-modified landscapes [12,13]. ...
Understanding wildlife's stress and infection response patterns is crucial, especially for species like bats that are ecologically important and potential zoonotic reservoirs. While highly sensitive to habitat destruction and land use change, bats have shown adaptability in human-modified landscapes. This study investigates the impact of urbanisation on the endemic Reunion free-tailed bat (Mormopterus francoismoutoui), which roosts in a variety of rapidly urbanised habitats. We analysed 412 urine samples from 11 roosts across Reunion Island, covering a gradient of urban and agricultural land use. We measured urinary cortisol, microbiome diversity and the shedding of Leptospira bacteria and paramyxovirus. After accounting for natural cortisol level variations due to circadian rhythm, age, sex, reproduction and capture-induced stress, we found that bats roosting in agricultural and urban areas were in better condition and had lower cortisol levels, suggesting adaptation to human-modified landscapes. Less-stressed bats had more diverse urinary microbiomes and reduced pathogen shedding, suggesting that landscape modifications may indirectly alter the natural epidemiology of bat-borne infectious agents. These patterns were particularly pronounced in females, supporting sex-dependent plasticity to urbanisation in bats. Our study highlights how rapid urbanisation may elicit plastic responses in bats, with potential cascading effects on zoonotic risk of transmission.
... Cities are environments where organisms are exposed to an array of novel, potentially extreme, conditions, such as air pollution, noise and light pollution, heatwaves, and easy access to food of low nutritional quality. The impact of urban life on the organismal physiology may be strong, and HPA-axis responsiveness and protection against oxidative stress are important mechanisms driving acclimation or adaptation to urban habitats.[87][88][89][90][91][92] For example, increasing urban cover was associated with decreased nonenzymatic antioxidant capacity and immune response to a mimicked bacterial infection in nestlings of a South African raptor (i.e., black sparrowhawk, Accipiter melanoleucus), suggesting that urbanization impairs aspects of immune function by limiting the capacity of nestlings to prevent oxidative stress.93 ...
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.
... As anthropogenic habitats rapidly expand globally [1], wildlife in human-modified environments faces numerous challenges, including habitat fragmentation, increased disturbance, and landscape and vegetation structure alterations [2]. These changes significantly affect food availability, which is vital for maintaining physical condition, reproduction, and overall fitness [3][4][5]. ...
... Dietary choices, including food processing and consumption, shape the nutritional specialization, physiology, anatomy, and foraging and vigilance behaviours of animals [2]. Diet analysis also informs key ecological processes, such as habitat selection and species competition. ...
The European ground squirrel (Spermophilus citellus) is an endangered mammal that inhabits open habitats with low vegetation in central and southeastern Europe. Its southernmost range includes northern Greece, where populations are declining due to habitat degradation and fragmentation. Limited behavioural research on Greek populations underscores the need for studies to support conservation efforts. The present study examined the species’ diet and seasonal changes in food consumption in an anthropogenic area of Central Macedonia, Greece. Between 2022 and 2023, feeding behaviour was documented recording plant parts, taxa, and feeding durations, while plant availability was assessed through surface sampling. The results revealed that Cynodon, Carex–Cyperus, Salvia, Solanum, and Plantago were the dominant plant genera in the species’ diet, while rhizomes and leaves were the most frequently consumed plant parts. Seasonal dietary shifts were observed, with ground squirrels selecting specific plants and plant parts based on availability. Under resource-limited conditions, they adapted by consuming nutritious rhizomes or the less-common, but toxic, S. elaeagnifolium. These findings highlight the species’ dietary adaptability to Mediterranean and human-modified environments, providing valuable ecological insights and informing habitat conservation and improvement strategies.
... pressures can have contrasting effects among mammalian species, behavioural flexibility in mammals allows them to better adapt to urban environments (Santini et al. 2019;Ritzel and Gallo 2020). Generally, mammals are easily disturbed by human activities, which drive changes in their behaviour that can impact diet, reproduction, stress, activity budgets and disease prevalence (Ditchkoff et al. 2006;Birnie-Gauvin et al. 2016;Ritzel and Gallo 2020). These adaptive responses may scale up to impacts on ecosystem function (Alberti 2015). ...
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.
... Urbanisation is one of the most pervasive forms of land-cover changes on our planet because it dramatically affects resources, space, and biogeochemical and microclimatic features (Grimm et al., 2008;Chakraborty and Qian, 2024). Urbanisation can also affect the physiology (Ditchkoff et al., 2006;Birnie-Gauvin et al., 2016;Damiani et al., 2024;Giovanetti et al., 2024), behaviour (Møller, 2008;Lowry et al., 2013;Biondi et al., 2024), life-history (Bailly et al., 2016;Sepp et al., 2018;Capilla-Lasheras et al., 2022), and morphology (e.g. Iglesias-Carrasco et al., 2017;Putman and Tippie, 2020) of a number of organisms. ...
... Attenuating threats deriving from human activities is essential for the welfare of wild animals. One of the most suggested initiatives is the creation of spatial and temporal buffers: areas and periods where human activities cease or are severely restricted (Birnie-Gauvin et al. 2016;Hansen et al. 2017). ...
Mediterranean Golden Eagles ( Aquila chrysaetos homeyeri ) are crucial for maintaining the balance of the ecosystem they live in. Human presence and some human activities are recognized as major disturbance factors affecting their welfare. In the present study, we evaluated through the measurement of feather corticosterone (CORTf), the welfare state of nestlings subjected to different levels of human pressure. Nestlings were sampled in different locations in Spain and Portugal for two consecutive years (2018, 2019). CORTf levels were higher in groups of individuals living in most populated areas and positively correlated with the proximity to airports, suggesting that human presence and noise pollution generated by aircraft may be a source of stress for developing eaglets, affecting their physiological state. CORTf levels were also related to mortality, finding low mean levels in individuals dying in the short-run. Finally, the relation between CORTf and other commonly used stress indicators such as the intensity of the color of the hue of cere and the number of fault bars in the tail of the nestlings was investigated. Considering the hue of cere, a significant negative strong correlation with the corticosterone levels in nestlings was found in samples from 2018 suggesting that nestlings in poorer nutritional conditions may present higher stress levels, whereas no correlation with the number of fault bars was found.
... Though urbanization has been linked with local extinctions, many songbird species successfully persist in urban habitats (Blair 1996, Marzluff 2001, McKinney 2002, Both et al. 2006, Bonier et al. 2007, Shochat et al. 2010, Sih et al. 2010, Sol et al. 2013, Wong and Candolin 2015. Whereas some animals can thrive under urban conditions (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. Indeed, some urban-dwelling birds exhibit poor body condition (Capilla-Lasheras et al. 2017: blue tits Cyanistes caeruleus; Murray et al. (2019): meta-analysis of 81 species of birds, fish, mammals, herpetofauna, and invertebrates), reduced reproductive success (Chatelain et al. 2021: blue tits Cyanistes caeruleus and great tits Parus major), lower antioxidative capacity, and greater oxidative damage (Herrera-Dueñas et al. 2014: house sparrows Passer domesticus) compared to rural conspecifics. ...
Urbanization reflects a major form of environmental change impacting wild birds globally. Whereas urban habitats may provide increased availability of water, some food items, and reduced predation levels compared to rural, they can also present novel stressors including increased light at night, ambient noise, and reduced nutrient availability. Urbanization can also alter levels of brood parasitism, with some host species experiencing elevated levels of brood parasitism in urban areas compared to rural areas. Though the demographic and behavioral consequences of urbanization and brood parasitism have received considerable attention, their consequences for cellular‐level processes are less understood. Telomeres provide an opportunity to understand the cellular consequences of different environments as they are a well‐established metric of biological state that can be associated with residual lifespan, disease risk, and behavior, and are known to be sensitive to environmental conditions. Here we examine the relationships between urbanization, brood parasitism, and blood telomere lengths in adult and nestling song sparrows Melospiza melodia. Song sparrows are a North American songbird found in both urban and rural habitats that experience high rates of brood parasitism by brown‐headed cowbirds Molothrus ater in the urban, but not the rural, sites in our study system. Among adults and nestlings from non‐parasitized nests, we found no differences in relative telomere lengths between urban and rural habitats. However, among urban nestlings, the presence of a brood parasite in the nest was associated with significantly shorter relative telomere lengths compared to when a brood parasite was absent. Our results suggest a novel, indirect, impact of urbanization on nestling songbirds through the physiological impacts of brood parasitism.
... Simultaneously, ecological conditions in urban areas bring benefits to wildlife (Birnie-Gauvin et al., 2016). The species that successfully adapt to urban areas often exhibit distinct behaviour, movement patterns, reproduction rates, dietary habits and survival rates compared to their counterparts in natural habitats (Ritzel & Gallo, 2020;Schell et al., 2021). ...
Wildlife in cities divides people, with some animals bringing positive benefits and others causing conflict, for example due to property damage.
Urban wildlife professionals from municipal administration, nature conservation, and hunting associations have a crucial role in shaping human‐wildlife relationships in cities and fostering conflict‐free coexistence. While many studies on urban wildlife have focused on the views of citizens, few have investigated the perspectives of experts to date. To address this knowledge gap, we interviewed 36 urban wildlife professionals giving guidance in the context of urban wildlife management, either in one of the four largest German cities by population (Berlin, Hamburg, Munich and Cologne) or at the national level.
Red foxes, wild boars, raccoons, stone martens and Eurasian beavers were the five mammal species most frequently highlighted in interviews to cause human‐wildlife conflicts. The interviewees saw wild boars and raccoons as the most controversial urban wild mammals but emphasized the need to create refuges for beavers and better inform the public about foxes.
Management in terms of public outreach, urban planning and population control, as well as establishing official contact points and stricter fines of activities violating regulations were highlighted as important elements of a toolkit to manage urban wildlife conflicts.
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... Later sessions are represented by warmer colors, smaller dots and lines with shorter dashes. The lines represent the relationship between the solving latencies in the two test types for each of the four consecutive sessions, fitted using linear regression with plug-opening latency as the response variable and string-pulling latency as covariate Alternatively, the lack of urban-rural differences in our and some other studies (Papp et al. 2015;Cook et al. 2017;Morton et al. 2023) and the better performance of rural animals in a few others (Prasher et al. 2019;Johnson Ulrich et al. 2021) can be explained by the poor nutritional conditions (Seress et al. 2018) and other forms of environmental stress and that has been suggested to occur in urban habitats (Birnie-Gauvin et al. 2016). Physiological condition and stress both can affect problem-solving performance (Bókony et al. 2014;Cook et al. 2017; but see Grunst et al. 2020), counteracting the stronger necessity for cognitive abilities to cope with such habitats. ...
Performance in tests of various cognitive abilities has often been compared, both within and between species. In intraspecific comparisons, habitat effects on cognition has been a popular topic, frequently with an underlying assumption that urban animals should perform better than their rural conspecifics. In this study, we tested problem-solving ability in great tits Parus major, in a string-pulling and a plug-opening test. Our aim was to compare performance between urban and rural great tits, and to compare their performance with previously published problem solving studies. Our great tits perfomed better in string-pulling than their conspecifics in previous studies (solving success: 54%), and better than their close relative, the mountain chickadee Poecile gambeli, in the plug-opening test (solving success: 70%). Solving latency became shorter over four repeated sessions, indicating learning abilities, and showed among-individual correlation between the two tests. However, the solving ability did not differ between habitat types in either test. Somewhat unexpectedly, we found marked differences between study years even though we tried to keep conditions identical. These were probably due to small changes to the experimental protocol between years, for example the unavoidable changes of observers and changes in the size and material of test devices. This has an important implication: if small changes in an otherwise identical set-up can have strong effects, meaningful comparisons of cognitive performance between different labs must be extremely hard. In a wider perspective this highlights the replicability problem often present in animal behaviour studies.
... Given these alterations in urban habitats, it is likely that urban populations face different physiological and behavioral challenges compared to their rural conspecifics (Birnie-Gauvin et al. 2016), and exposure to urban stressors may alter the physiology and health of urban populations (Murray et al. 2019;Isaksson and Bonier 2020). For example, a meta-analysis determined that exposure to anthropogenic pollution (such as sulfur-dioxide, organic pollutants, ozone, and heavy metals) increases oxidative stress in terrestrial animals, which can cause tissue damage linked to disease and senescence (Isaksson 2010). ...
Urban wildlife faces unique physiological and behavioral challenges compared to conspecifics which live in less altered natural habitats. Animals in urban habitats are also exposed to urban stressors and commonly make use of inappropriate food sources from trash bins and dumpsters, which may affect their heath status. The goals of this study were to evaluate overall health of an urban population of eastern gray squirrels (Sciurus carolinensis) and to assess seasonal changes in several health parameters. Squirrels (N = 45) were trapped in Durham, North Carolina, USA and briefly anesthetized with inhalant anesthetic for physical examination, body mass collection, and venipuncture via the femoral vein. Collected blood was analyzed for several health parameters via hematology and biochemistry analyses including assessment of lipids and kidney and liver values. Physical examinations were clinically unremarkable and similar across seasons. Females had higher cholesterol values and lower creatinine values compared to males. Seasonal differences occurred in few parameters and were detected only between summer and either fall or spring. Potassium and monocytes were higher in summer compared to spring, and creatinine, BUN and monocytes were higher in summer compared to fall. Overall, health parameters of urban eastern gray squirrels fell within published reference ranges for the species. Together, these results suggest that urban squirrels in this study population can maintain good health in an anthropogenic habitat.
