Urban wildlife refers to animal species that live in or frequently use urban and suburban areas, which are spaces dominated by human structures and activities, such as cities, towns, and surrounding neighborhoods. These environments differ from natural habitats in terms of habitat fragmentation, human presence, and resource distribution, yet many species have adapted to survive and even flourish in urban settings. Urban wildlife contributes to local biodiversity, ecosystem function, and public health considerations.Luniak, M. (2004). Synurbization—adaptation of animal wildlife to urban development. The 4th International Symposium on Urban Wildlife Conservation. CiteSeerX 10.1.1.122.3057. PDF
Other species simply tolerate cohabiting around humans and use the remaining urban forests, parklands, green spaces and garden/street vegetations as niche habitats, in some cases gradually becoming sufficiently accustomed around humans to also become synanthropic over time. These species represent a minority of the natural creatures that would normally inhabit an area, and contain a large proportions of feral and introduced species as opposed to truly native species. For example, a 2014 compilation of studies (which were biased towards work in Europe, with very few studies from south and southeast Asia) found that only 8% of native bird and 25% of native plant species were present in urban areas compared with estimates of non-urban density of species.
Urban wildlife can be found at any latitude that supports human dwellings. The list of animals that will venture into urbanized human settlements to forage on horticultures or to scavenge from trash runs from monkeys in the tropics to polar bears in the Arctic.
Different types of urban areas support different kinds of wildlife. One general feature of bird species that adapt well to urban environments is they tend to be the species with bigger brains, perhaps allowing them to be more behaviorally adaptable to the more volatile urban environment. Arthropods (insects, spiders and millipedes), gastropods (land snails and slugs), various worms and some reptiles (e.g. house geckos) can also thrive well in the niches of human settlements.
Adaptation to urban environments Many species adjust to urban environments through a process called synurbization, which describes the behavioral and ecological changes that allow animals to cope with human-dominated landscapes. These adaptations may include changes in feeding behavior, daily activity, movement patterns, and tolerance of human presence. Examples of species that have adapted to urban life include blackbirds (Turdus merula), striped field mice (Apodemus agrarius), and urban foxes.
Ecological characteristics Urban ecosystems tend to favor generalist species, which can survive on a wide range of foods and in varied habitats. Species that require specific habitats, such as forest specialists, often decline as urbanization increases. Typical urban wildlife includes small mammals such as rats, mice, and squirrels; birds such as pigeons and sparrows; medium-sized mammals like raccoons, foxes, and coyotes; reptiles; and various invertebrates. Many of these species utilize human-provided food sources, such as trash bins, gardens, and sewer systems, and may adjust their behavior, for example becoming more active at night to avoid humans.
Cities create opportunities for new ecological interactions among species. However, urban wildlife communities are often dominated by resilient generalists and invasive species, which can reduce the diversity of native animals and contribute to ecological uniformity across cities.
Evolution Urban environments can exert novel selective pressures on organisms, sometimes leading to new adaptations. For example, the weed Crepis sancta, found in France, has two types of seed, heavy and fluffy. The heavy ones land near the parent plant, whereas the fluffy seeds float further away on the wind. In urban environments, seeds that float far often land on infertile concrete surfaces. Within about 5-12 generations the weed has been found to evolve to produce significantly more heavy seeds than its rural relatives. Among vertebrates, a case is urban great tits, which have been found to sing at a higher pitch than their rural relatives so that their songs stand out above the city noise, although this is probably a learned rather than evolved response. Urban silvereyes (an Australian bird) make contact calls that are higher frequency and slower than those of rural silvereyes. As it appears that contact calls are instinctual and not learnt, this has been suggested as evidence that urban silvereyes have undergone recent evolutionary adaptation so as to better communicate in noisy urban environments.
As a consequence of synurbization, animals that inhabit urban environments have differences in morphology, physiology and behavior when compared to animals that inhabit less urbanized areas. Hormone-mediated maternal effects are capable mechanisms of offspring phenotypic developmental modification. For instance, when female birds deposit androgens into their eggs, this affects many diverse aspects of offspring development and phenotype. Environmental factors that can influence the concentration of androgens in avian eggs include nest predation risk, breeding density, food abundance and parasite prevalence, all factors of which differ between urban and natural habitats. In a study that compared antibody and maternal hormone concentrations in eggs between an urban population and a forest population of European blackbirds, there were found to be clear differences in yolk androgen concentrations between the two populations. Although these differences cannot be attributed definitively (more studies have to be performed), they might result from different environments causing females to plastically adjust yolk androgens. Different yolk androgen levels are likely to program offspring phenotype.
Plant genetic variation has an influence on herbivore population dynamics and other dependent communities. Conversely, different arthropod genotypes have varying abilities to live on different host plant species. Differential reproduction of herbivores could lead to adaptation to particular host plant genotypes. For instance, in two experiments that examined local adaptation and evolution of a free-feeding aphid (Chaitophorus populicola) in response to genetic variants of its host plant (Populus angustifolia), it was found that, 21 days (about two aphid generations) after aphid colony transplantation onto trees from foreign sites, aphid genotype composition had changed. In the experiments, tree cuttings and aphid colonies were collected from three different sites and used to conduct a reciprocal transplant experiment. Aphids that were transplanted onto trees from the same site produced 1.7-3.4 times as many offspring as aphids that were transplanted onto trees from different sites. These two results indicate that activities of human perturbation that cause plant evolution may also result in evolutionary responses in interacting species that could escalate to affect entire communities.
Wildlife species that inhabit urban areas often experience shifts in food and resource availability. Some species, at times, must resort to human handouts or even human refuse as a source of food. One animal notorious for relying on such means for nutritional intake is the American white ibis. In a study that tested physiological challenge, the innate and adaptive immunity of two groups of white ibis (both consisting of 10 white ibis nurtured in captivity), one group being fed a simulated anthropogenic diet and the other being fed a natural ibis diet, it was determined that wildlife consumption of a diet with anthropogenic components (such as white bread) may be detrimental to a species' ability to battle bacteriaal pathogens.
Public health and zoonotic disease Some urban wildlife species can carry diseases that can infect humans, known as zoonotic diseases. Close contact between humans and animals such as rodents, raccoons, and stray domestic animals can increase the likelihood of disease transmission. Urban rodents have been shown to carry bacterial, viral, and parasitic pathogens, while certain urban birds, including ducks and crows, may carry antibiotic-resistant bacteria.
Understanding how diseases spread among urban wildlife, humans, and other animals is complex. The One Health approach emphasizes the interconnectedness of human, animal, and environmental health to help manage and prevent zoonotic risks.
Conservation and management While some urban wildlife species thrive in cities, others are negatively affected by habitat loss, pollution, and lack of connectivity to natural areas. Conservation strategies in urban areas aim to support biodiversity through practices such as habitat restoration, creating green corridors, planting native species, and involving communities in monitoring wildlife. These efforts can help reduce conflicts between humans and animals and promote healthier urban ecosystems.
Research on urban wildlife informs city planning and management practices that balance ecological, public health, and social objectives. Providing safe movement paths for wildlife, improving habitat quality, and limiting anthropogenic threats are important for sustaining urban biodiversity.
Effects of artificial lights at night Urban environments are defined by elevated levels of artificial light at night (ALAN), which constitute a significant ecological factor affecting wildlife behavior and physiology. Empirical research demonstrates that exposure to artificial light disrupts circadian and seasonal rhythms, alters foraging behaviors, and interferes with migration across diverse taxa. In urban contexts, such disruptions influence predator-prey dynamics, reproductive cycles, and patterns of habitat utilization. Furthermore, artificial light can shift species distributions by favoring light-tolerant organisms and displacing others, thereby shaping biodiversity and ecosystem processes within urban areas.
Human–wildlife conflict While urban areas tend to decrease the overall biodiversity of species within the city, most cities retain the flora and fauna characteristic of their geographic area. As rates of urbanization and city sprawl increase worldwide, many urban areas sprawl further into wildlife habitat, causing increased human-wildlife encounters and the potential for negative and conflict-based encounters. Humans have lived alongside and near wild animals for centuries, but the expansion of the study of urban ecology has allowed for new information surrounding human-wildlife interactions. Human wildlife conflict can be categorized into disease transmission, physical attacks, and property damage, and can be inflicted by a range of wildlife, from predatory tigers to grain-eating rodents.
Benefits of human–wildlife interactions
While negative human-wildlife conflicts can be damaging to the physical health of humans or property, human-wildlife interactions can be extremely beneficial in terms of ecosystem health and cultural experiences. The presence of native species allows systems and food chains to function in a healthy way, providing ecosystem services to the humans living around these areas. These services include the provisioning of food and water, flood control, cultural services, and nutrient cycling. Due to those perceived benefits, urban rewilding is now an active movement.
Costs of conflict The most direct impacts of human-wildlife conflict include loss of livelihood due to property damage, loss of possessions due to property damage, injury, or transmission of disease from wildlife to humans. After the direct impacts of conflict, however, the people facing human-wildlife conflict are left with long-term issues including opportunity costs and long-term fear of wildlife.