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New Study Shows Human Activity Creates a More Nocturnal Animal World

Rapid expansion of human activity across the globe is causing wildlife to become more nocturnal, according to a new joint study conducted by researchers at Boise State University and the University of California, Berkeley, and published in the journal, Science.

While animals have long been documented altering their spatial patterns out of fear and avoidance of human beings, the article, “The Influence of Human Disturbance on Wildlife Nocturnality,” posits that animals may also choose to separate themselves from humans in time. The study is the first of its kind to attempt to quantify the global effects of human activities on the temporal activity patterns of wildlife.

“We are finding more and more species, like bears, elk, and mountain lions, becoming more active at night in order to avoid human presence,” explained Neil Carter, a Boise State assistant professor in human environment systems. “We were curious whether these shifts were occurring worldwide and if they depended on the types of human activities, like hunting or recreation.”

Carter worked closely with lead author Kaitlyn Gaynor, Justin Brashares and Cheryl Hojnowski from UC Berkeley on the study.

The researchers examined the anthropogenic impacts on mammal activity patterns by conducting a meta-analysis of 76 studies of 62 species from six continents. This global study revealed that human presence had a strong effect on wildlife activity – animals increased their nocturnality by an average factor of 1.36 in response to human disturbance. For example, an animal that typically split its activity evenly between the day and night would respond to human disturbance by increasing its nocturnal activity to 68 percent of its total activity. The meta analysis found that 83 percent of animals responded to humans in this way – be they lethal activities, like hunting, nonlethal activities, including hiking, and even human infrastructure. This finding indicates a significant, widespread increase in nocturnality among mammals living alongside people.

This finding was consistent across continents, habitats, taxa and human activities.

“These results were shocking and a real eye-opener to how pervasive these shifts are,” Carter said. “Because an animal’s interaction with its environment, like finding mates or food, is largely shaped by the times of day that it is active, becoming more nocturnal to avoid humans has profound implications on wildlife communities and ecosystem services. As the human footprint expands, understanding the consequences of these shifts on animal populations and their evolution is vital.”