“The effects of human activity on wildlife extend far beyond the direct removal of individuals or habitats,” says Kaitlyn Gaynor of the University of California-Berkeley. “Our mere presence can have subtle but consequential impacts on animal behaviour."
“We ultimately included 141 case studies in our analysis, and 83 per cent of these showed some increase in nocturnal activity around people,” she says. “When we pooled these individual cases together, the result was powerful and striking: human activity is creating a more nocturnal natural world.”
On average, mammals become 1.36 times more nocturnal in areas of human activity. Coyotes, for example, usually split their activity evenly between night and day, but in popular hiking areas they shift to 70 per cent nocturnality.
“While it is clear that animals are drastically changing their behaviour around people, we don’t yet understand the consequences of this shift for individual animals or populations,” says Gaynor.
She is in two minds about whether the findings are more a cause for concern or hope. On the one hand, it could be a sign of how well large mammals are able to adapt to co-exist with humans.
“As long as animals are able to meet their needs during the night, they may actually thrive in human-dominated landscapes, and avoid direct encounters with people that could potentially be dangerous for both parties,” she says.
On the other hand, working the night-shift may be a case of making the best of a bad job. “Many of the animals in our study are adapted to being active in the daylight, and may not be as successful at finding food, avoiding predators, or communicating in the darkness,” says Gaynor. “We may even see compromised reproduction
or survival.”