What is Urban Wildlife?
Urban wildlife animal communities consist of species that utilize human dominated ecosystems. Although urban species vary in their use and exploitation of developed areas, they all come into contact with humans either in cities or on the woodland-urban interface. Examples of common urban wildlife species in the United States include both native species (e.g. raccoons, red-tailed hawks, and coyotes) and invasive species (English sparrows, European starlings, house mice, rock doves, and Norwegian rats).
Characteristics of successful urban wildlife:
May utilize human food sources, such as birdfeeders, garbage, or pet food
Are typically omnivorous and generalists with regard to food and habitat
Are often strong competitors and can exclude native species
May have a higher tolerance of human disturbance
Can change their behavior and adapt to major environmental disturbances
For further reading (also see references at bottom of page):
Ditchkoff, S. S., S. T. Saalfeld, and C. J. Gibson. 2006. Animal behavior in urban ecosystems: modifications due to human-induced stress. Urban Ecosystems 9:5–12.
McKinney, M. L. 2002. Urbanization, biodiversity, and conservation. BioScience 52:883–890.
Shochat, E., P. S. Warren, S. H. Faeth, N. E. McIntyre, and D. Hope. 2006. From patterns to emerging processes in mechanistic urban ecology. Trends in Ecology and Evolution 21:186–191.
Why Study Urban Wildlife?
Wildlife is present even in the densest of cities. In order to preserve biodiversity, maintain ecosystem function, reduce property damage, foster safe neighborhoods, and encourage positive associations with wildlife, the study of urban animal communities seeks to understand stressors on wildlife populations, species interactions, and sources of human-wildlife conflict. Current directions in urban wildlife research are the development of more mechanistic approaches to understanding human-wildlife relationships that include the incorporation of behavior and species interactions.
Understand Urban Ecosystems:
Despite large effects on animal ecology in developed areas, many species persist. It is of great interest to scientists to understand which species thrive in urban areas or are able to tolerate human presence and what characteristics are associated with persistence. In order to appreciate the ecosystem-level impacts of urbanization, a deeper understanding of how behavior and demography of urban wildlife are influenced by alterations to native habitat.
Investigate Landscape Connectivity and Function:
Development heavily fragments natural landscapes, and species that are able to effectively utilize urban zones may benefit from higher functional connectivity. Refuges and parks in urban areas can act as stepping-stones for animals navigating human-dominated landscapes. Protecting and enhancing animal movement paths is important to the preservation of genetic viability of urban wildlife populations. Corridors for wildlife can also rescue small populations from extinction by allowing new individuals to immigrate from larger, healthier populations.
Mitigate Human-Wildlife Conflict:
Wild animals are increasingly coming into contact with people as cities continue to sprawl into undeveloped regions. Urban, suburban, and exurban growth can increase edge habitat, creating more opportunity for humans and wildlife to come into contact. Human welfare and safety depend on a thorough understanding of urban wildlife and their interactions with the anthropogenic landscape. Pets and livestock are often most at risk from interactions with urban wildlife and may require extra precautions to ensure their protection from native predators. Urban wildlife research can seek out solutions to human-wildlife conflicts to minimize property damage and safety risks while still preserving intact wildlife populations.
Encourage Biophilia and a Connection to Nature:
Much of the world lives in cities or on the fringes of development. In these heavily modified landscapes, it can be challenging for the public to experience more pristine ecosystems. Public parks and open space not only increase habitat and connectivity for urban wildlife, but also expose people to nature in their own backyards. There are many opportunities in urban environmental education that can enhance the lives of children and citizens while also fostering an appreciation for conservation.
Types of Urban Wildlife
Urban wildlife species can be considered human obligates, associates, exploiters, adapters, or avoiders. These designations relate to the degree to which urban wildlife benefits from or is harmed by anthropogenic habitat change. Whereas some species are able to take advantage of human food subsidies or refuge from predators, others persist in human dominated landscapes by avoiding contact with people as much as possible.
Human obligates might not be considered wildlife by some because they are often domestic animals, however they play a major role in urban wildlife community composition. Obligates compete with, disturb, and most importantly, predate upon native species. Species interactions between obligates and natives greatly influence community function and diversity both in and on the fringes of urban development. Domestic cats in particular are known for their impressive predatory skills and their impacts on native and migratory bird species.
Who are they? Domestic cat, domestic dog, livestock (cow, goat, sheep)
Human associates and exploiters are often generalist or omnivorous species that can take advantage of anthropogenic resource subsidies, or food supplied by humans. Human food sources can take the form of gardens, garbage, domestic animals, pet food, or other human exploiters. Exploiter populations in particular are able to achieve much higher numbers in urban areas than in wildlands due to the prevalence of available food. However, exploiters can also reach high numbers in developed areas due to release from predation or the ability to outcompete other native species in a novel environment (McKinney 2006). Relationships between exploiters and local residents vary; songbirds that use backyard feeders are often regarded positively, whereas predators that kill pets are likely to have negative associations. Property damage and disease transmission can also generate negative attitudes toward certain exploiters, including raccoons.
Who are they? Raccoon, Virginia opossum, European starling, house finch, rock dove, house mouse, California gull, American crow, Eurasian collared dove, house sparrow, grey squirrel
Human adapters are species that may utilize human resources and survive in human dominated areas, but do not necessarily receive an added benefit from living with humans. These species are often located on the periphery of development and may be relatively common in areas dominated by rural and exurban development. Adapters generally have not had a history of antagonism with humans and are often generalists that can use a wide variety of habitats. Deer are sometimes regarded as human adapters, as they can achieve high population sizes from wild areas to suburban habitats.
Who are they? Bobcat, coyote, white-tailed deer, black bear, American robin, red fox, striped skunk, Northern cardinal, lesser goldfinch, red-tailed hawk
Human avoiders are not expected to use urban areas, but occasionally may find themselves amongst people when attempting to disperse or migrate. Avoiders often have either a history of conflict with humans or very specific habitat requirements for reproduction or foraging that are unattainable in human settlements. These species can experience high mortality rates or decreased reproductive rates in human dominated habitats. Mountain lions, for example, are human avoiders, but occasionally come into conflict with human communities by eating livestock or pets.
Who are they? Mountain lion, grey wolf, grey fox, Pileated woodpecker (This category is largely comprised of local native species with particular habitat requirements, and is challenging to characterize. Unlike urban wildlife, native wildlife assemblages are highly distinct and diverse across the United States. When thinking about human avoiders, consider which species you see in open spaces or state parks near your town, but not within its limits.)
Disturbances and Threats to Urban Wildlife
Urban ecosystems are often comprised of similar disturbances, including:
Light and noise pollution
Chemical runoff and pollution
These disturbances can result in biotic homogenization, or the selection of the same animals that can tolerate human development and proliferate in urban landscapes across large spatial scales (McKinney 2006). Biotic homogenization threatens to favor the same generalist species in all cities, while diminishing populations of local endemics and specialists, which can be easily outcompeted by generalist and invasive species in disturbed habitats (Shochat et al. 2010).
Direct effects: Structure and function of the urban wildlife community is facilitated by differential responses to development and the degree to which species can utilize human resources. While some bat species are disturbed by anthropogenic light pollution (Stone et al. 2009), amphibians may be impacted primarily by loss of aquatic habitat or chemical runoff into waterways (Brand et al. 2010), and carnivores can be poisoned by the bioaccumulation of rodenticides (Riley et al. 2007). Other species have higher risk of disease in developed habitats due to higher population densities or interaction with domestic animals (Daszak et al. 2000). Large predators are at risk of decline due to spatial constraints and habitat fragmentation that decrease population size and genetic diversity (Bateman and Fleming 2012). Behavioral responses to development can inhibit wildlife from obtaining necessary resources or finding suitable mates for reproduction (Habib et al. 2006).
Indirect effects: Urbanization can alter interactions between species and therefore impact some species indirectly. Indirect effects often occur as a result of changes in the predator community (Prange and Gehrt 2004) or resource composition (Oro et al. 2013). For example, mesopredator release can occur with the loss of top predators, increasing predation pressure on native songbirds and small mammals (Crooks and Soule 2010). Anthropogenic subsidies can also produce indirect effects by decoupling predator-prey feedbacks (Rodewald et al. 2011).
Cumulative effects: Many anthropogenic impacts on wildlife populations are exacerbated by urbanization and development (Sala et al. 2000). For example, fragmenting the landscape by building roads and housing reduces the ability for species impacted by climate change to track their suitable climate envelope. Complex and cumulative effects of urbanization and other ecosystem changes therefore threaten to dramatically restructure wildlife communities.
Reducing Human-Wildlife Conflict
One of the best ways to avoid human-wildlife conflict is to reduce attractants for unwanted animals. To reduce conflict with urban wildlife, residents can:
Lock all outdoor garbage cans
Regularly dispose of fallen fruit from fruit trees
Keep pets indoors at night
Keep goats, sheep, and chickens in a covered enclosure at night
Keep cats indoors as much as possible, especially when migratory birds are in the area
Use birdfeeders specifically designed not to spill or be accessible by non-target species
Be aware of any wildlife-borne diseases in your region that could infect you or your pet
For more tips on coexisting with wildlife, visit the California Department of Fish and Wildlife “Keep Me Wild” campaign homepage.
Brand, A. B., J. W. Snodgrass, M. T. Gallagher, R. E. Casey, and R. Van Meter. 2010. Lethal and sublethal effects of embryonic and larval exposure of Hyla versicolor to Stormwater pond sediments. Archives of environmental contamination and toxicology 58:325–331.
Crooks, K. R., and M. E. Soule. 2010. Mesopredator release and avifaunal extinctions in a fragmented system. Nature 400:563-566.
Daszak, P., a a Cunningham, and a D. Hyatt. 2000. Emerging infectious diseases of wildlife: threats to biodiversity and human health. Science 287:443–9.
Ditchkoff, S. S., S. T. Saalfeld, and C. J. Gibson. 2006. Animal behavior in urban ecosystems: Modifications due to human-induced stress. Urban Ecosystems 9:5–12.
Habib, L., E. M. Bayne, and S. Boutin. 2006. Chronic industrial noise affects pairing success and age structure of ovenbirds Seiurus aurocapilla. Journal of Applied Ecology 44:176–184.
McKinney, M. L. 2002. Urbanization , Biodiversity , and Conservation. BioScience 52:883–890.
McKinney, M. L. 2006. Urbanization as a major cause of biotic homogenization. Biological Conservation 127:247–260.
Oro, D., M. Genovart, G. Tavecchia, M. S. Fowler, and A. Martínez-Abraín. 2013. Ecological and evolutionary implications of food subsidies from humans. Ecology Letters 16:1501-1514.
Prange, S., and S. D. Gehrt. 2004. Changes in mesopredator-community structure in response to urbanization. Canadian Journal of Zoology 82:1804–1817.
Riley, S. P. D., C. Bromley, R. H. Poppenga, F. A. Uzal, L. Whited, and R. M. Sauvajot. 2007. Anticoagulant exposure and notoedric mange in bobcats and mountain lions in urban southern California. Journal of Wildlife Management 71:1874–1884.
Rodewald, A. D., L. J. Kearns, and D. P. Shustack. 2011. Anthropogenic resource subsidies decouple predator-prey relationships. Ecological Applications 21:936–943.
Sala, O. E., F. S. Chapin, J. J. Armesto, E. Berlow, J. Bloomfield, R. Dirzo, E. Huber-Sanwald, L. F. Huenneke, R. B. Jackson, A. Kinzig, R. Leemans, D. M. Lodge, H. A. Mooney, M. Oesterheld, N. L. Poff, M. T. Sykes, B. H. Walker, M. Walker, and D. H. Wall. 2000. Global Biodiversity Scenarios for the Year 2100. Science 287:1770–1774.
Shochat, E., S. B. Lerman, J. M. Anderies, P. S. Warren, S. H. Faeth, and C. H. Nilon. 2010. Invasion, competition, and biodiversity loss in urban ecosystems. BioScience 60:199–208.
Stone, E. L., G. Jones, and S. Harris. 2009. Street lighting disturbs commuting bats. Current Biology 19:1123–1127.