Cities are not only urban centers for us humans, they also provide a habitat for numerous animals. But the animal city dwellers sometimes differ significantly from their relatives in the countryside. While pigeons in the forest usually flee as soon as a person approaches, their counterparts in the city peck right at our feet. A survey study has now systematically evaluated which behaviors animals display in the city and in the country. The result: city animals are braver, more curious and more active, but also more aggressive than their wilder counterparts.
We humans change our environment profoundly. In this way, we are also presenting the animal world with new challenges: where there were once meadows and forests, there are now streets and houses. While we have displaced many animals, others have adapted to life in the city. Many studies have already determined how this affected their behavior for individual species. However, a comprehensive overview across species and national borders has so far been missing.
City and country animals in comparison
Now a team led by Tracy Burkhard from the University of Montpellier in France has evaluated 81 studies from 28 countries, which together include 133 species. The researchers discovered universal patterns: “We found that urbanization changes behavior worldwide in a consistent, predictable way,” reports Burkhard. “The urban populations were bolder and more aggressive than their counterparts outside of cities. They also tended to be more active and showed more exploratory behavior.”
Since most of the studies evaluated related to birds, the results for this group of animals are clearest. But similar tendencies also emerged for mammals, reptiles, amphibians and insects. “These patterns suggest that urban populations are subject to parallel, directional selection or that animals migrating to the city are exposed to environmental filtering by typical urban conditions that favor certain types of behavior,” explain the researchers.
Adaptation as an advantage and a risk
The characteristics adapted to urban life help the animals to settle and survive in an environment that usually has little in common with their original habitat. For example, bolder and more exploratory individuals have a better chance of finding new food sources in the city and its rapidly changing conditions. They are also less stressed by the constant human presence.
But that is precisely what also brings risks: “If animals are more willing to take risks and are less afraid of the presence of people, we will come into contact with wild animals much more often in certain areas, and that is potentially bad for us and the wild animals,” says Burkhard. This makes conflicts between people and animals more likely and the risk of zoonoses also increases.
From the researchers’ perspective, the results underline the need to take the behavior and needs of animals into account in urban planning. For example, interconnected green spaces can create corridors through which non-winged urban animal populations can also connect with one another. At the same time, Burkhard and her colleagues emphasize that there is still a great need for research in the field of urban evolutionary ecology, especially with regard to previously little-studied animal groups such as insects, amphibians and reptiles.
Source: Tracy Burkhard (Université de Montpellier, France) et al., Journal of Animal Ecology, doi: 10.1111/1365-2656.70269