Global meta-analysis finds urban animals bolder and more aggressive than rural counterparts

Global Study Reveals Urban Animals Are Bolder and More Aggressive

A major new meta-analysis confirms that urbanization is driving consistent, predictable changes in animal behavior worldwide, making them more willing to take risks.

"Urbanization is changing behavior in consistent, predictable ways worldwide, with animals becoming more risk-positive."
— Dr. Tracy Burkhard, Lewis & Clark College

A global meta-analysis, published in the British Ecological Society's Journal of Animal Ecology, has found that urban populations of birds, mammals, amphibians, reptiles, and insects exhibit heightened boldness, aggression, exploration, and activity compared to their rural counterparts.

The findings were most pronounced in birds, but the researchers note that data for other animal groups remain limited.

• Researchers from Lewis & Clark College, CEFE-CNRS, and North Dakota State University combined data from 80 studies across 28 countries and 133 species.
• Over 70% of studies focused on birds; insects, amphibians, and reptiles made up just 10% of the data.
• Critically, urban animals consistently showed increased risk-taking behavior across all studied taxa, from birds to insects.

The same behavioral trends were observed even in species typically associated with rural habitats. Animals like the whitethroat, yellowhammer, and redpoll are now adapting to urban environments, displaying the same bold behaviors seen in classic city-dwelling species.

The researchers warn that these behavioral shifts carry significant risks for both humans and wildlife:

• Increased human-wildlife conflict: Bolder animals are less wary of people, leading to more frequent and potentially dangerous encounters.
• Zoonotic disease transmission: Closer contact between humans and wildlife can increase the risk of disease spillover.

"Increased risk-taking and reduced aversion to humans could lead to more frequent human-wildlife contact, potentially harmful to both."
— Dr. Tracy Burkhard

Dr. Anne Charmantier, co-author from the French National Centre for Scientific Research (CNRS), highlighted a critical gap in the research: "There is an imbalance in research effort across taxa." She called for more studies on amphibians, reptiles, and insects to better understand the full scope of urbanization's impact.

The researchers suggest that urban planners should consider animal behavior when designing cities. A key recommendation is to create connected greenspaces—such as green corridors and parks—to maintain connectivity and gene flow among urban animal populations, potentially mitigating some negative effects of isolation.