Human activity pushing mammals to grow more active at night, global study finds

(U.S. Fish and Wildlife Service)

(Courthouse News) Mammals worldwide are becoming more active at night due to human activity such as agriculture and hunting, according to a large-scale analysis of more than 60 species on six continents, the journal Science reported Thursday.

Researchers used GPS, remotely triggered cameras and radio collars to collect data on when animals are active, compared to human activities.

The researchers found that mammals were 1.36 times more nocturnal in response to human activity, which includes residential settlements, agriculture, hunting and hiking.

The meta-analysis was conducted by researchers from the University of California- Berkeley’s College of Natural Resources and Boise State University, and looked at 76 studies of 62 species across six continents.

Both meat- and plant-eating animals that generally spend their time equally divided between day and night increased their nocturnal activity by 68 percent around human activity, the study found.

“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 Kaitlyn Gaynor, UC Berkeley Ph.D. candidate and lead author.

“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.”

The study did not look at mammals lighter than 1 kilogram (2.2 pounds). They ranged in size from the common opossum to the African elephant.

Many scientific studies have analyzed how human activity has affected wildlife populations and habitat, but this study shows “the subtler ways in which we affect animal behavior,” Gaynor said.

“We assert that fear of humans is the primary mechanism driving the increase in wildlife nocturnality, given its prevalence across activity types and the widespread evidence that mammals perceive and respond to risk from people,” the authors wrote.

The research shows how nonhuman animals adapt to human activity, and could help us coexist with them, the authors said.

“The separation of humans and wildlife in time, if not space, may also limit contact rates between people and dangerous animals and therefore reduce some forms of negative encounters between the two, such as disease transmission and attacks on people,” the researchers wrote.

“In situations where humans pose a lethal threat to wildlife, increased nocturnality may be advantageous to individual animals and has been linked to increased probability of survival.”