How Do Animals Cope with City Life?

Scientists have noticed that urban animals often differ from those in natural areas in their behavior (what they do), physiology (how their bodily systems function), and morphology (their form). How did these differences come about? Do they help animals cope with the challenges of city life? Below, we describe the results of some fascinating scientific studies of how animals in cities and natural areas differ, how they come about, and their consequences for success in cities. This description is not meant to be comprehensive, but rather to provide a brief introduction into the many fascinating ways animals change in cities and what it means for them.

Traits of Urban Wildlife


Finding Food

Many animals behavior differently in cities than in natural areas. One major challenge for urban animals is finding food: many natural food sources are scarce, and a variety of new food resources (think trash and pet food!) are available (1). Urban animals may have altered diets, which include human trash, bird seed, and/or pet food, and they may be more willing to explore new foods. Some animals, such as racoons and coyotes, may have smaller home ranges because they can find abundant food in cities without traveling far (1).

Altered food resources and temperatures in urban environments may lead to changes in the timing and success of animal breeding (2). Some birds start breeding earlier and breed for a longer time period in urban areas. Many species suffer reduced success during breeding, perhaps due in part to scarcity of special food sources needed to feed offspring, such as insect prey for bird nestlings (3).

A red house-shaped bird feeder with tan and red house finches on each side. One finch is a female, with brown feathers. The other is a male, with a bright red head and brown body.
Two House Finches at a bird feeder. Joshua J. Cotten | Unslpash
A coyote lays on a lawn with buildings in the background. Dru Bloomfield | Flickr

Building nests

Urban animals may also take advantage of other novel resources in cities, such as using artificial structures as nesting sites (2). The Black Phoebe is a clear example–these birds were once restricted to building their mud nests on sheltered banks and rocks near water, but they have now expanded into many urban areas, where they nest on human-made buildings and bridges. Similarly, Barn Swallows and Cliff Swallows often build mud nests on human-made structures.

Three barn swallow chicks peak over the edge of a mud nest, which is attached to a wall underneath a roof.
Young Barn Swallows almost ready to leave the nest. Dave Wilson Photography

Avoiding Risk

Urban environments present very different risks from natural ones. Many large predators, like mountain lions, are much rarer in cities. This means that prey animals like deer may spend less time watching for and escaping from potential predators (1). Other animals are exposed to higher densities of predators: small animals like songbirds and lizards are killed in staggering numbers by domestic cats (4). Exposure to these predators may cause a variety of behavioral changes, such as visiting their nest or young less frequently (5). Urban animals are also frequently near humans, and they may become habituated to human presence (1). However, many animals alter the timing of their activities to avoid people. For instance, many mammal species are more active at night in human-disturbed areas, which may allow them to avoid encounters with people (6).

Two gulls stand on the roof of a car in front of storefronts. One gull is gray and white, while the other is dark gray-brown.
Two gulls perched on a car. Many bird species have longer flight initiative distances in cities, which means they let humans get closer to them before they fly away. Dave King | Flickr

Coping with pollution

Cities are polluted with light, noise, and chemicals, which may disrupt communication among animals. Many animals make sounds to attract mates, recognize each other, and alert others to danger. To avoid city noise drowning out these signals, animals may sing or call more loudly, for longer durations, at different times, or even at different frequency ranges (1). For example, many birds sing at higher frequencies in urban areas, which may make their songs more audible over low frequency traffic and industrial noise (7). Fascinatingly, one study reported that when streets where quiet during the COVID-19 pandemic, White-crowned Sparrows returned to singing at lower frequencies (8). Light pollution may also impact animal behavior. Sea turtle hatchlings rely on light from the open horizon to find the ocean after they hatch, but in cities they may instead migrate inward toward lighted structures (9).

A gray and brown sparrow with a white and black striped head perches on the tip of a tree. Its bill is parted, suggesting it is singing.
A singing White-crowned Sparrow. Eric Sonstroem | Flickr

Individual differences

Individual animals show consistent differences in behavioral traits (sometimes called animal personality), such as boldness, aggression, exploration, and sociality (10). Some personalities may be better suited to urban life than others (2). For instance, urban brown anoles are bolder, less aggressive, and spend more time exploring new habitats (11).

A Brown Anole perched on a sign. CyclicalCore | Deviant Art


Stress Hormones

Hormones play a critical role in regulation of physiological functions–how bodily systems function. A stressful situation, such as escaping from a hungry predator, triggers a cascade of “stress hormones” in humans and animals alike. This hormonal response evolved to help us fight off or run from danger.

Urban environments present many challenges for wildlife, leading scientists to predict that city-living leads to increased baseline stress hormone levels (12-13). Some studies have found that urban birds have higher baseline stress hormone levels than those in non-urban areas, but others have found no difference at all or even the opposite pattern (12-13).

City-living might also lead to reduced responsiveness to stressful events, but scientists haven’t found any consistent patterns in how urban and non-urban animals respond to acutely stressful events (12-13). This is perhaps surprising–if urban environments are challenging for organisms, why don’t we see consistent differences in stress hormone levels? We don’t really know yet! But scientists are hard at work to understand how responses to urbanization vary among different cities, species, and individual animals.

An aerial shot of a wolf pack surrounding a bison on snowy ground
This bison is likely experiencing a rush of stress hormones, which help it fight off or run from danger. Wikimedia Commons
House Sparrows in urban Phoenix have higher baseline levels of the stress hormone corticosterone than those in the nearby desert (12). Lip Kee | Flickr

Reproductive Hormones

Reproductive hormones are responsible for regulating sexual development and reproduction. You have likely heard of testosterone and estrogen–these hormones are also present in other mammals, and most animals have something similar!

Scientists have observed that urban animals often breed earlier and for longer, perhaps due to warmer temperatures and availability of food (e.g., trash, breed seed). These reproductive differences are likely driven by changes in reproductive physiology. Studies of the reproductive hormones of urban animals are still few and far between, but those that exist haven’t found any consistent differences between urban and non-urban animals (12-13). For instance, sometimes urban European Blackbirds have lower testosterone levels during breeding, but the testosterone levels of urban Dark-eyed Juncos are elevated over a long period of time than those of their non-urban counterparts (12). More research in this area is urgently needed!

Urban European Blackbirds have higher testosterone levels than those in rural areas (12). Luiz Lapa | Flickr
Urban Dark-eyed Juncos have lower testosterone levels than those in nearby natural areas (12). VJAnderson | Wikimedia Commons

Thermal Physiology

Urban areas are hot! The downtown of a city is often several degrees Celsius warmer than nearby natural areas, which is called the urban heat island effect. Buildings, asphalt, and other dark-colored urban surfaces absorb a lot of heat, and it gets trapped bouncing around among tall buildings.

Thermal physiology refers to the physiological strategies that organisms use to respond to changes in temperature. The thermal -physiology of urban animals may change to allow them to tolerate hot urban conditions. For example, crested anoles in cities can function with higher temperatures than those from rural areas (14). This may be due to changes in their genes that help prevent their proteins from becoming damaged when exposed to high temperatures (14).

Urban birds may also be better able to tolerate hot conditions: a study found that Great Tits (a European songbird) in forests suffer from reduced growth during heat waves, but the growth of city birds is not affected by extreme heat (15). We don’t yet understand why these urban nestlings were less impacted by heat, but it may have to do with changes in thermal physiology!

Crested anoles living in cities can tolerate higher body temperatures than non-urban anoles (14). RobinSings | Wikimedia Commons
Great Tits living in forests suffer reduced growth during heat waves, but city living birds do not (15). nottsexminer | Wikimedia Commons

Oxidative Balance and Inflammation

You’ve likely heard that antioxidants are good for you. This is because molecules called reactive oxygen or nitrogen species (RS), which are natural by-products of our bodily functions, can cause damage to our cells if they aren’t neutralized. These RS contribute to the progression of many diseases in humans and wildlife alike, including cancer. Antioxidants neutralize these reactive molecules and protect our body from damage. When we don’t have enough antioxidants to neutralize all of these RS, we are said to experience oxidative stress and our cells can be damaged or even killed.

Urban animals may experience greater oxidative stress than those in rural or natural areas. Some urban chemical pollutants, such as nitrogen oxides, may react to form RS in the body, leading to inflammation and oxidative stress (16). More generally, chemical, noise, and light pollution may disrupt the body’s ability to combat RS, leading to oxidative stress (16). In combination with greater exposure to RS, urban animals may often have a poor quality, junk food diet that is lower in antioxidants (16). However, more research is needed in this area.

Many fruits are high in antioxidants. Bicanski | PIXNIO
Exposure to nitrogen oxides, produced by burning of fuel, can lead to oxidative stress. United Nations Information Centre | Fickr


Body size

Body size is one of an animal’s most fundamental traits, affecting temperature regulation, mobility, the food an animal can eat, and much more. Animals may be able to cope with urbanization and changing climates by shifting their body sizes (17). Animals living in cities are often larger than those in rural or natural areas. These may be because they have to travel large distances between suitable patches of habitat in cities, making it advantageous to have large bodies and long legs (17). Animals that eat human trash or food might also be able to grow larger (17). However, this isn’t always the case. Poor quality urban food might lead to nutritional stress, reducing body size of some animals, like songbirds (17). Being small may actually be advantagageous in sweltering hot urban centers because small animals can dissipate heat more quickly (17).

Small animals lose heat faster than large animals because they have a higher surface area to volume ratio.

Arms, shoulders, knees, and toes

A variety of other morphological traits may differ between city living animals and their non-urban counterparts. For instance, many species of lizards have longer legs and toes in cities than nearby rural and natural areas, which may improve their ability to grip smooth surfaces like concrete (18). House Finches, a common urban dwelling songbird, have longer and narrower bills in cities than in nearby deserts. These changes in bill shape may be adaptations to eating larger, harder-to-crack seeds at backyard birdfeeders (18). On the other hand, urban-living foxes have shorter, wider muzzles than those in rural areas, which may be the result of developmental changes linked to “friendly” or “tame” behavioral traits (20).

A gray and red bird stands on a wooden platform next to a pile of black sunflower seeds.
A House Finch with a pile of sunflower seeds, which are commonly in bird feeders. Dick Daniels | Wikimedia

Feathers and hair

Feathers and hair serve a variety of functions, including insulating an animal from extreme temperatures. Cities are often hotter than nearby rural and natural areas, and changes in feathers and hair may allow urban animals to cope with this “urban heat island” effect. Along these lines, urban songbird chicks have fewer feathers than their rural counterparts, leaving larger patches of bare skin that may help them lose body heat faster (21). Feathers and hair come in a range of colors, which may help animals stay hidden from predators or communicate with others. Cities are often predominantly gray, and city-living animals seem to follow suit: animals in urban areas are darker in color, they have duller colors, and are often gray (22-23). These color changes may help birds hide from predators, or they may be driven by limited access to high quality food in urban areas (22-23).

The Rock Pigeon, a common urban dweller, exemplifies the dark, gray colors often found in urban animals. eBird

How do these differences come about?

**Under construction**

Are these differences adaptive?

**Under construction**


  1. Sol D, Lapiedra O, González-Lagos C. Behavioural adjustments for a life in the city. Animal Behaviour. 2013 May 1;85(5):1101–12.
  2. Lowry H, Lill A, Wong BBM. Behavioural responses of wildlife to urban environments. Biological Reviews. 2013;88(3):537–49.
  3. Chamberlain DE, Cannon AR, Toms MP, Leech DI, Hatchwell BJ, Gaston KJ. Avian productivity in urban landscapes: a review and meta-analysis. Ibis. 2009;151(1):1–18.
  4. Loss SR, Will T, Marra PP. The impact of free-ranging domestic cats on wildlife of the United States. Nat Commun. 2013 Jan 29;4(1):1396.
  5. Bonnington C, Gaston KJ, Evans KL. Fearing the feline: domestic cats reduce avian fecundity through trait-mediated indirect effects that increase nest predation by other species. Journal of Applied Ecology. 2013;50(1):15–24.
  6. Gaynor KM, Hojnowski CE, Carter NH, Brashares JS. The influence of human disturbance on wildlife nocturnality. Science. 2018 Jun 15;360(6394):1232–5.
  7. Patricelli GL, Blickley JL. Avian Communication in Urban Noise: Causes and Consequences of Vocal Adjustment. The Auk. 2006 Jul 1;123(3):639–49.
  8. Derryberry EP, Phillips JN, Derryberry GE, Blum MJ, Luther D. Singing in a silent spring: Birds respond to a half-century soundscape reversion during the COVID-19 shutdown. Science. 2020 Oct 30;370(6516):575–9.
  9. Tuxbury SM, Salmon M. Competitive interactions between artificial lighting and natural cues during seafinding by hatchling marine turtles. Biological Conservation. 2005 Jan;121(2):311–6.
  10. Réale D, Reader SM, Sol D, McDougall PT, Dingemanse NJ. Integrating animal temperament within ecology and evolution. Biological Reviews. 2007;82(2):291–318.
  11. Lapiedra O, Chejanovski Z, Kolbe JJ. Urbanization and biological invasion shape animal personalities. Global Change Biology. 2017;23(2):592–603.
  12. Bonier F. Hormones in the city: endocrine ecology of urban birds. Horm Behav. 2012 May;61(5):763–72.
  13. Deviche P, Sweazea K, Angelier F. Past and future: Urbanization and the avian endocrine system. General and Comparative Endocrinology. 2022 Nov 9;114159.
  14. Campbell-Staton SC, Winchell KM, Rochette NC, Fredette J, Maayan I, Schweizer RM, et al. Parallel selection on thermal physiology facilitates repeated adaptation of city lizards to urban heat islands. Nat Ecol Evol. 2020 Apr;4(4):652–8.
  15. Pipoly I, Preiszner B, Sándor K, Sinkovics C, Seress G, Vincze E, et al. Extreme Hot Weather Has Stronger Impacts on Avian Reproduction in Forests Than in Cities. Frontiers in Ecology and Evolution [Internet]. 2022 [cited 2022 Sep 2];10. Available from:
  16. Isaksson C. Urbanization, oxidative stress and inflammation: a question of evolving, acclimatizing or coping with urban environmental stress. Functional Ecology. 2015;29(7):913–23.
  17. Martin AK, Sheridan JA. Body size responses to the combined effects of climate and land use changes within an urban framework. Global Change Biology [Internet]. [cited 2022 Jul 27];n/a(n/a). Available from:
  18. Putman, B. J., & Tippie, Z. A. (2020). Big city living: a global meta-analysis reveals positive impact of urbanization on body size in lizards. Frontiers in Ecology and Evolution, 8, 580745.
  19. Badyaev, A. V., Young, R. L., Oh, K. P., & Addison, C. (2008). Evolution on a local scale: developmental, functional, and genetic bases of divergence in bill form and associated changes in song structure between adjacent habitats. Evolution62(8), 1951-1964.
  20. Parsons, K. J., Rigg, A., Conith, A. J., Kitchener, A. C., Harris, S., & Zhu, H. (2020). Skull morphology diverges between urban and rural populations of red foxes mirroring patterns of domestication and macroevolution. Proceedings of the Royal Society B, 287(1928), 20200763.
  21. Sándor, K., Liker, A., Sinkovics, C., Péter, Á., & Seress, G. (2021). Urban nestlings have reduced number of feathers in Great Tits (Parus major). Ibis, 163(4), 1369-1378.
  22. Leveau, L. (2021). United colours of the city: A review about urbanisation impact on animal colours. Austral Ecology, 46(4), 670-679.
  23. Leveau, L. M. (2019). Urbanization induces bird color homogenization. Landscape and Urban Planning, 192, 103645.
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