City Life Makes Animals Bolder

The city mouse really may be bolder than the country mouse.

A new global analysis led by Assistant Professor of Biology Tracy Burkhard, finds that animals living in cities tend to be bolder, more aggressive, more exploratory, and more active than animals of the same species living in rural areas.

Assistant Professor of Biology Tracy BurkhardResearchers from Lewis & Clark, CEFE-CNRS in Montpellier, France, and North Dakota State University conducted this first-of-its-kind global meta-analysis comparing behavior in a variety of urban and nonurban animal populations. Their findings, published in the British Ecological Society’s Journal of Animal Ecology, draw on data from 81 existing studies of animal behavior. Together, these studies represent 133 species across 28 countries, including birds, mammals, amphibians, reptiles, and insects.

“We found that no matter where you are in the world, urbanization is changing behavior in consistent, predictable ways,” says Burkhard. “The strongest result was that animals seem to be more risk positive. They’re more bold.”

The pattern was strongest among birds, which also made up the majority of available research. More than 70 percent of the studies included in the analysis focused on birds, while insects, amphibians, and reptiles together accounted for just 10 percent of the data. The researchers say that gap points to the need for more study of how urban life affects a broader range of animals.

Anne Charmantier, research director at CNRS, University of Montpellier, and a coauthor of the research says: “Our study shows that the research effort is very imbalanced across taxa; in particular birds are much more commonly studied than amphibians, reptiles, or insects. The lack of data in some animal classes limits some of our conclusions and should be seen as an encouragement to study all organisms living in cities.”

The study also suggests that urban animal behavior is not limited to the species people most often associate with city life, such as rats, gulls, and pigeons. Similar shifts are showing up in species more commonly connected to rural habitats, including birds such as the whitethroat, yellowhammer, and redpoll, as they adapt to urban environments.

Those changes could have real consequences for both people and wildlife. Animals that are more willing to take risks may also be more likely to come into close contact with humans, potentially increasing the chance of conflict or disease transmission.

“If animals are more risk-taking and they’re less averse to human presence, we’re going to be coming into contact with wildlife a lot more in certain areas, and that is potentially bad for both us and wildlife,” says Burkhard.

As cities continue to grow, the researchers say urban planners should consider not only where animals live, but how city environments may shape the way they behave. Creating more diverse urban habitats could help support a wider range of animal behaviors—and healthier relationships between people and the wildlife living alongside them.

Biology