Animals seem to be more risk positive. They're more bold.
As cities expand across the globe, the creatures sharing those spaces are quietly transforming — not in body, but in spirit. A landmark synthesis of 80 studies spanning 133 species and 28 countries has confirmed what scattered observations long suggested: urban animals are bolder, more aggressive, and less wary of humans than their rural counterparts, a behavioral shift that holds from songbirds in Europe to mammals in North America. The finding, published in the Journal of Animal Ecology, invites us to reckon with a deeper truth — that when we reshape the landscape, we reshape the living world within it, and that world reshapes us in return.
- A first-of-its-kind global meta-analysis has confirmed that urban wildlife consistently takes more risks, approaches humans more readily, and responds to threats with greater aggression than rural populations of the same species.
- The shift is not confined to familiar city opportunists like rats and pigeons — even birds traditionally tied to wild habitats, such as whitethroats and yellowhammers, are growing bolder as they colonize urban environments.
- Increased boldness means increased contact, and increased contact means rising risks: more human-wildlife conflict, more property confrontations, and a greater likelihood of zoonotic disease transmission between animals and people.
- Scientists warn of a critical blind spot — over 70 percent of the data comes from birds, leaving insects, amphibians, and reptiles largely unstudied, meaning the full scale of urban behavioral change remains unknown.
- Urban planners are now being called to treat animal behavior as a design variable, with connected greenspaces and wildlife corridors proposed as tools to ease the tension between expanding cities and the creatures adapting to survive within them.
Something is changing in the way animals carry themselves in cities. A sweeping new analysis drawing on 80 studies from 28 countries has found that urban wildlife — birds, mammals, insects — consistently behave with greater boldness, aggression, and exploratory drive than their rural relatives. The pattern holds across continents and across species. Conducted by researchers at Lewis & Clark College, CEFE-CNRS, and North Dakota State University, it is the first global synthesis of its kind, examining 133 distinct species through the lens of behavioral ecology.
The shift is not subtle. Urban animals approach humans with less hesitation, venture into unfamiliar spaces more readily, and respond to perceived threats more aggressively. Birds show the strongest effect — unsurprising, given they dominate the dataset — but the change extends well beyond the usual urban suspects. Species like whitethroats and yellowhammers, birds historically tied to rural and wild habitats, are now exhibiting the same risk-embracing tendencies as city pigeons and gulls.
Lead author Dr. Tracy Burkhard described the core finding plainly: urbanization reshapes animal behavior in consistent, predictable ways worldwide. That consistency is precisely what makes the implications serious. As animals grow less wary of humans, contact between the two intensifies — and with it, the risk of conflict and zoonotic disease transmission. Bolder animals in shared spaces are not just a curiosity; they are a public health and safety variable.
The research also reveals how much remains unknown. Insects, amphibians, and reptiles together account for just 10 percent of the data, leaving vast portions of urban animal life unstudied. Co-author Dr. Anne Charmantier called this gap an urgent prompt for broader scientific inquiry. Meanwhile, the findings are already pressing urban planners to think differently — to treat connected greenspaces and wildlife corridors not as amenities, but as infrastructure for a world where humans and animals are growing ever closer, whether we plan for it or not.
Across the globe, something is shifting in how animals behave when they move into cities. A sweeping analysis of research from 28 countries has found that urban wildlife—from birds to insects to mammals—consistently display bolder, more aggressive, and more exploratory behavior than their rural relatives. The pattern holds whether you're looking at cities in Europe, Asia, North America, or elsewhere. The research, published in the Journal of Animal Ecology by teams at Lewis & Clark College in Portland, CEFE-CNRS in Montpellier, and North Dakota State University, represents the first global synthesis of its kind, drawing together data from 80 separate studies examining 133 distinct species.
The behavioral shift is unmistakable and consistent. Urban animals take more risks. They approach humans with less caution. They explore their surroundings more actively and respond to threats with greater aggression. Birds showed the strongest effect—which makes sense, given that over 70 percent of the research examined avian species—but the pattern appears across the animal kingdom. It's not just the usual suspects either. While city rats, gulls, and pigeons have long been known to adapt to urban life, the same behavioral changes are now visible in species traditionally associated with wild or rural habitats: whitethroats, yellow hammers, and redpolls, birds that would normally avoid human settlements, are becoming bolder as they colonize cities.
Dr. Tracy Burkhard, an assistant professor of biology at Lewis & Clark College and the study's lead author, framed the finding plainly: urbanization reshapes animal behavior in predictable, consistent ways across the world. The core shift is toward risk-taking. Animals in cities are less wary of human presence. They venture into spaces they might otherwise avoid. They interact with people and human infrastructure more readily.
This behavioral transformation carries real consequences. As animals become less averse to humans, contact between the two increases—and increased contact creates friction. There is a heightened risk of human-wildlife conflict: more aggressive encounters, more property damage, more confrontations in spaces where people and animals now share territory. There is also a public health dimension. Animals that are bolder and less cautious around humans are more likely to transmit zoonotic diseases—illnesses that jump from animals to people. The closer the contact, the greater the transmission risk. Burkhard noted the tension plainly: if animals are more willing to take risks and less afraid of human presence, contact will intensify in certain areas, and that outcome is potentially harmful to both humans and wildlife.
The research also exposes a significant gap in scientific knowledge. The 80 studies examined were heavily weighted toward birds, which accounted for more than 70 percent of the data. Insects, amphibians, and reptiles together made up just 10 percent. This imbalance means that for most species living in cities, we simply don't know how urbanization is reshaping their behavior. Dr. Anne Charmantier, a research director at CNRS and co-author of the study, emphasized that this knowledge gap should be seen as an urgent call for more research across all animal groups, not just the charismatic or visible ones.
The findings carry implications for how cities are designed and managed. Urban planners typically focus on human needs—transportation, housing, commerce. But the research suggests that animal behavior must now be part of the conversation. Creating connected greenspaces that allow urban animal populations to maintain genetic diversity and social structure could help mitigate some of the behavioral shifts. Maintaining corridors between fragmented habitats, preserving patches of vegetation, and designing cities with wildlife movement in mind are no longer optional considerations. As urbanization accelerates globally, the animals living alongside us are changing in ways we're only beginning to understand. The question now is whether cities can be redesigned to accommodate those changes, or whether the cost of urbanization for wildlife—and for us—will continue to rise.
Notable Quotes
No matter where you are in the world, urbanisation is changing behaviour in consistent predictable ways. The strongest result was that animals seem to be more risk positive.— Dr. Tracy Burkhard, Lewis & Clark College
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.— Dr. Tracy Burkhard
The Hearth Conversation Another angle on the story
So these animals are bolder in cities. But is that actually a problem? Isn't adaptation a sign of success?
It depends on what you mean by success. Yes, these animals are surviving and reproducing in cities. But boldness in an urban context often means less fear of humans, which increases contact. More contact means more conflict—more attacks, more disease transmission, more damage. It's not adaptation in the way we usually celebrate it.
You mentioned disease. Are we talking about something like COVID, or smaller risks?
Both scales exist. Zoonotic diseases range from minor to catastrophic. The point is that when animals lose their natural wariness of humans, they spend more time near us, in our spaces, eating our food, living in our buildings. That proximity is where transmission happens.
The study looked at 133 species. That sounds comprehensive.
It sounds that way, but it's not. Over 70 percent of the data is about birds. We barely know what's happening with insects, amphibians, reptiles. We're drawing conclusions about urbanization's effects on the animal kingdom based on a very bird-heavy picture. That's a real limitation.
What would change if we knew more about insects and reptiles?
We might find that the pattern is even stronger, or weaker, or different in ways we can't predict. Insects are incredibly diverse and ecologically important. If urbanization is reshaping their behavior in ways we don't understand, that could have cascading effects we're not prepared for.
So what's the practical takeaway for cities?
Urban planners need to think about animal behavior when they design spaces. Connected greenspaces, habitat corridors, vegetation patches—these aren't luxuries. They're infrastructure for managing the reality that cities are now shared spaces. Without intentional design, the boldness we're seeing in urban animals will only increase the friction between us.