Gray wolves are walking farther. Ravens are foraging in new places. Coyotes are staying put. Across 37 wildlife species tracked throughout the United States, researchers have discovered that animals don't just avoid humans—they respond to our mere presence with surprising behavioral flexibility, sometimes expanding their territory and sometimes contracting it, depending on the species.
A landmark six-year study led by Yale researchers and conducted across more than 50 academic and governmental organizations has fundamentally shifted how scientists understand wildlife in a world shaped by human activity. The work, published in Science, tracked 11.8 million location points from over 4,500 animals—22 bird species including hawks, cranes, and vultures, and 15 mammal species from white-tailed deer to wolves and coyotes. For the first time, researchers used GPS tracking combined with mobile phone data and satellite measurements to directly separate the impact of human presence alone from the effects of habitat loss caused by urbanization and agriculture.
"Animals are affected by both direct human presence and by human-caused changes to the physical environment," said Walter Jetz, director of Yale's Center for Biodiversity and Global Change. "This study is the first to directly assess at scale how both causes, separately and in combination, impact wildlife habitat usage."
The breakthrough was made possible by an unexpected window: COVID-19 lockdowns in 2020 dramatically altered human movement patterns, allowing researchers to compare animal behavior between 2019 and 2020. This natural experiment let scientists isolate how animals respond to the presence of people, regardless of whether forests had been cleared or cities had expanded. What they found was striking. More than 65% of the species studied changed their behavior based on human presence alone, independent of habitat destruction.
But the responses varied dramatically by species. Gray wolves expanded their range, likely traveling farther to avoid people. Ravens, conversely, covered more ground—not fleeing from humans but exploiting food sources associated with human activity. Coyotes took the opposite approach from wolves, restricting their movements when people were nearby. The findings revealed that individual animals could adjust their behavior from year to year, demonstrating flexibility in response to changing human activity.
The geographical pattern was equally revealing: human presence mattered most in less-developed, natural settings. In these areas, even recreational use of the landscape influenced how animals moved and which habitats they chose to occupy. Ruth Oliver, now an assistant professor at UC Santa Barbara's Bren School of Environmental Science and Management and lead author of the study, described the challenge of capturing this data: "It has been challenging to capture the impact of human presence on wildlife. Mobile device data are typically not available, but our study was made possible thanks to a unique partnership that made estimates of human presence available to researchers during the COVID-19 pandemic."
The implications for conservation are profound. While habitat loss remains the primary driver of biodiversity loss, this research shows that where and when humans are physically present fundamentally shapes animal behavior—sometimes amplifying the damage of habitat loss, sometimes mitigating it. Protecting wildlife, the researchers suggest, requires conservationists to think beyond land use change and consider the human footprint itself as a conservation variable. As our relationship with wild spaces continues to evolve, so too must our strategies for sharing them.