Gaynor, along with co-authors Justin Brashares and Cheryl Hojnowski of UC Berkeley, and Neil Carter of Boise State University, applied a meta-analysis approach, using data for 62 species across six continents to look for global shifts in the timing of daily activity of mammals in response to humans. These data were collected by various approaches, including remotely triggered cameras, GPS and radio collars, and direct observation. For each species in each study site, the authors quantified the difference in animal nocturnality under low and high human disturbance.

On average, mammals were 1.36 times more nocturnal in response to human disturbance. This means that an animal that naturally split its activity evenly between the day and night increased its nighttime activity to 68% around people. This finding was consistent across carnivore and herbivore species of all body sizes greater than 1 kg (small mammals were not included in the study). The pattern also held across different types of human disturbance, including activities such as hunting, hiking, mountain biking, and infrastructure such as roads, residential settlement, and agriculture.

“While we expected to find a trend towards increased wildlife nocturnality around people, we were surprised by the consistency of the results around the world,” said Gaynor. “Animals responded strongly to all types of human disturbance, regardless of whether people actually posed a direct threat, suggesting that our presence alone is enough to disrupt their natural patterns of behavior.”