The rise of wildlife camera traps on public lands and backyards not only delights viewers on social media with candid glimpses of the lives of roaming animals but also offers critical scientific insight into when animals are active. These camera trap images recently led to a global study published in Science Advances that has dramatically revised scientific understanding of when wild mammals are active – and the pervasive influence of human activity on their behavior patterns. 

A team of over 200 researchers, including Kadambari Devarajan, a former Northeast CASC fellow, and Northeast CASC Research Ecologist Toni Lyn Morelli, compiled a dataset of 8.9 million observations from more than 20,000 camera traps sites across 38 countries and six continents. This allowed them to analyze the activity patterns of 445 mammal species, from gorillas to skunks to foxes, hares, and porcupines. The findings challenge long-held traditional classifications of animal activity. For decades, scientists have used four fixed classifications to describe when animals are active: Species can be diurnal (active during the day), nocturnal (active at night), crepuscular (active at twilight), or cathermeral (active at multiple times). But the new analysis revealed that only 39% of the 445 species fit neatly into one of the classifications and most (74%) regularly shifted their activity patterns in response to environmental conditions and human activities. Of many examples of this behavioral flexibility, elk were active during both night and day in areas with little human presence, but they adopted a night-only schedule in areas where humans were highly present. Similar patterns emerged for gray foxes, snowshoe hares, striped skunks, and porcupines.  

This study indicates that human activities during key time periods could interfere with an animal’s ability to access food, shelter, or mates. By building the largest database of standardized wildlife activity, this research team was able to reassess how species are interacting with changing environments. Understanding how human activity may change animal behavior can help wildlife managers plan more effective conservation strategies.