Urban wildlife is wildlife that can live or thrive in urban environments. Some urban wildlife, such as house mice, are synanthropic, ecologically associated with humans. 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 adaptable to the changeable urban environment.
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. 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 evolution so as to better communicate in noisy urban environments.
On the Cape Peninsula near Cape Town in South Africa, human development have been encroaching on baboon habitat for years and the baboons have adapted remarkably well in raiding homes for food. Elsewhere in Africa, vervet monkeys as well as baboons adapt to urbanisation, and similarly enter houses and gardens for food. African penguins are also known to invade urban areas, searching for food and a safe place to breed. Simon's Town, next to the popular Boulders Beach had to take action to restrict penguin movement due to the noise and damage they caused. There are reports of leopards roaming suburban areas in cities such as Nairobi, Kenya and Windhoek, Namibia. Reptiles like the house gecko (Hemidactylus) can be found in houses.
In India, the situation is similar to Africa. Monkeys, such as langurs, also enter cities for food, and cause havoc in food markets when they steal fruit from the vendors. In Mumbai, leopards have entered neighbourhoods surrounding the Sanjay Gandhi National Park and killed several people, as the park itself is besieged by a surrounding burgeoning population, where poaching and illegal woodcutting is rife.
Urban areas range from fully urban, areas have little green space and are mostly covered by paving, tarmac, or building, to suburban areas with gardens and parks. Pigeons found scavenging on scraps of food left by humans and nesting on buildings, even in the most urban areas, as the tall buildings resemble that of their natural rocky homes in the mountains. Rats can also be found scavenging on food. Gulls of various types also breed and scavenge in various UK cities. A study by the bird biologist Peter Rock[disambiguation needed], Europe's leading authority on urban gulls, into the rise of herring gulls and lesser black-backed gulls in Bristol has discovered that in 20 years the city's colony has grown from about 100 pairs to more than 1,200. From a gull's point of view, buildings are simply cliff-sided islands, with no predators and lots of food nearby. The trend is the same in places as far apart as Gloucester and Aberdeen. With an endless supply of food, more city chicks survive each year; to become accustomed to urban living. They in turn breed even more birds, with less reason to undertake a winter migration.
From a study conducted on great tits living in 10 European cities and in 10 nearby forests. An analysis was made of the way the birds used songs to attract mates and establish territorial boundaries. Hans Slabbekoorn, of Leiden University in the Netherlands, said that city birds adapt to life by singing faster, shorter, and higher pitch songs in the cities compared to forests. The forest birds sing low and they sing slow. Great tits living in noisy cities have to compete with the low-frequency sounds of heavy traffic, which means their songs go up in pitch to make themselves heard. A bird that sang like Barry White in the forest sounded more like Michael Jackson in the big city.
The advent of these animals has also drawn a predator, as Peregrine falcons have also been known to nest in urban areas, nesting on tall buildings and predating pigeons. The peregrine falcon is becoming more nocturnal in urban environments, using urban lighting to spot its prey. This has provided them with new opportunities to hunt night-flying birds and bats. Red foxes are also in many urban and suburban areas in the UK as scavengers. They scavenge, and eat insects and small vertebrates such as pigeons and rodents. People also leave food for them to eat in their gardens. One fox was even found living at the top of a skyscraper.
In some cases even large animals have been found living in cities. Berlin has wild boars. Wild roe deer are becoming increasingly common in green areas in Scottish towns and cities, such as in the Easterhouse suburb of Glasgow. Moscow has feral dogs, a few of which have even learned to use the Moscow subway system. Urban waterways can also contain wildlife, including large animals. In London, since improvements in water quality in the Thames, seals and porpoises have been seen in its waters in the center of the city .
Close proximity to avian life hasn't presented a problem for people in the past, but there are new concerns about the spread of bird flu (the H5N1 virus) via infected migratory birds. Some scientists are worried that persistent human expansion could indirectly lead to a disease pandemic of global proportions.
Numerous animals can also live within buildings. The house mouse, a small mammal, is specialised for living alongside humans, and is found inside buildings. Insects that sometimes inhabit buildings include the cockroach, the silverfish, and many various species of small beetles. See also housefly.
Sewers and other underground spaces
Sewers also contain wildlife. The best known wildlife of sewers is rats. An escaped pet boa constrictor was found living in sewage pipes in a block of flats in Manchester. A type of worm known as the tubifex worm is quite abundant as well. There is also the London Underground mosquito. A popular legend of sewer wildlife is that certain species of alligator live in the sewers of Louisiana, New York, Florida, and so forth.
Many North American species have successfully adapted to urban environments and are thriving. Typical examples include coyotes, the top predator of such regions. Other common urban animals include: predators such as red foxes, grey foxes and bobcats that prey on small animals such as rodents. Omnivores such as raccoons, Virginia opossums and striped skunks are seldom seen and mainly come out at night; In the south and southeastern United States and Mexico the nine-banded armadillo joins these other omnivores but due to the armadillo's lack of thick fur they are unable to thrive in more northern climates. Squirrels, including the American red squirrel, fox squirrel and eastern grey squirrel are extremely common in suburbs with enough trees. Herbivores forage in the early morning and evening with cottontail rabbits and in dryer parts of the country jackrabbits as well as the two most common deer species in North America the white tailed deer and the mule deer, shy of humans they are often spotted as a mother with fawns or a lone buck creeping through the trees and bushes. As whitetails prefer forest edge and meadow to actual dense forest the cutting of forests has actually made more habitat for the white tailed deer which has increased its numbers beyond what they were at when Europeans arrived in America. In some cities older deer seem to have learned how to cross the street as they look back and forth while crossing roads looking for cars while fawns and younger deer will recklessly run out without looking; most traffic accidents involving deer happen with deer that have just left their mother who are less likely to watch for cars.
These animals sometimes come into conflict with humans, as these animals will open garbage bags in search of food, eat food left out for pets, take unattended pets themselves, feed on prized garden plants, dig up lawns or pose as traffic hazards when they run out into the road. Coyotes pose a risk to small children, who should not be left unsupervised in areas coyotes are known to inhabit; they are large enough to easily kill/eat a child and lack the fear of humans most wild canids exhibit. While there are media accounts of alligators being found in sewer pipes and storm drains, most experts[who?] think that such 'sewer alligators' are unlikely to sustain a breeding population in such an environment due to a lack of place to bury their eggs. The National Zoo of Washington, DC has breeding populations of tropical geckos throughout its steam tunnels; which venture into Rock Creek Park and develop limited breeding populations during the spring/summer, however these populations die out during the fall/winter.
Marmosets can be found living wild in city parks in Brazil. Urban-dwelling marmosets tend to return more often to the same sleeping sites than jungle-dwelling marmosets. Urban-dwelling marmosets tend to prefer to sleep in tall trees with high first branches and smooth bark. It has been suggested they do this to avoid cats.
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