A landmark study published in Science has revealed that human physical presence — independent of habitat destruction, urbanization, or infrastructure — significantly alters the behavior and movement of wildlife across the United States.
Researchers from UC Santa Barbara, the Smithsonian's National Zoo, and Yale University combined GPS tracking data from 4,581 individual mammals and birds spanning 37 species with anonymized cellphone geolocation data, marking the first time mobile phone location data has been used to study how human presence affects animal movement.
The findings were striking: 57% of the species studied were affected by both human presence and landscape modification. For 67% of mammal species and 68% of bird species, human presence was associated with changes in territory size or environmental niche — the way animals use habitats and resources.
"Humans have complicated effects on wildlife — from our physical presence to how we reshape habitats — but we can't understand our full impact without information on both," said co-lead author Ruth Oliver, an assistant professor at UCSB's Bren School of Environmental Science & Management.
The COVID-19 lockdowns of 2020 created a unique natural experiment. As human movement patterns shifted dramatically during pandemic restrictions, researchers were able to separate the effects of people simply being present from the effects of permanent landscape changes like roads and cities.
The study uncovered dramatically different responses across species. Wolves, for example, expanded their habitat use in response to human presence — potentially reflecting their long, adversarial history with people and an instinct to spread out away from human activity. White-tailed deer showed the opposite pattern: their environmental niches expanded as landscapes became more developed but contracted as human presence increased. Sandhill cranes displayed yet another pattern.
Sensitivity to human presence was especially strong in relatively undeveloped areas like national parks, suggesting that even low-impact human visitation can meaningfully alter wildlife behavior in places specifically set aside for conservation.
About 67% of mammal species and 41% of bird species reduced their habitat use when both human presence and landscape alteration were combined — a compounding effect that could have significant implications for conservation planning.
The research is part of the COVID-19 Bio-Logging Initiative, an international collaboration involving 600 partners that assembled 1 billion location records from roughly 13,000 animals. The initiative has produced multiple findings about how wildlife responded during the global "anthropause" — the period when pandemic restrictions dramatically reduced human activity.
The team is now investigating whether these behavioral changes help or harm wildlife — specifically, whether animals that alter their behavior in response to human pressures face higher or lower mortality risk.
"Our results give me some optimism that we can achieve wildlife coexistence through more nuanced policies that more smartly consider where and when we need to give animals space," Oliver said.
