Animals Becoming Nocturnal To Avoid Being Around Humans

A tiger sits in a zoo. Wild animals, including tigers, have to adapt to life where humans walk around their habitat during daylight hours. REUTERS/Bernadett Szabo

Across the world, a variety of animals that are normally diurnal (active during the day) are starting to increase their nocturnal activity. According to new research published in the journal Science, that's likely because those animals want to avoid pesky humans.

"Many animals fear humans: we can be large, noisy, novel, and dangerous, and animals often go out of their way to avoid encountering us," ecologist at the University of California, Berkeley and study author Kaitlyn Gaynor told Newsweek.

"But it's becoming more and more challenging for wildlife to seek out human-free spaces, as the human population grows and our footprint expands across the planet," Gaynor continued. "It appears that animals are instead adjusting their activity patterns to avoid humans in time, if not space."

For the study, Gaynor and her team compiled data from 76 studies on 62 species. They found that animals living near humans were slightly more active at night than their counterparts further away from humans. For example, a species that is typically 50 percent diurnal would, on average, become 68 percent nocturnal in the presence of human disturbance.

A human "disturbance" could be people being loud, building roads and infrastructure, poaching animals or taking over their land. It could also be more seemingly-benign acts, like hiking and mountain biking in wild parks. "We may think we leave no trace when we recreate in the outdoors, but our mere presence can have lasting consequences," Gaynor said.

Non-human animals simply want to avoid humans, regardless of the intentions of said humans.

Previous studies support the idea that human activity affects animal behavior, even if those humans mean no harm to the animals in question. For example, a study in 2003 found that animals become more stressed up to a hundred meters from each side of trails on which humans like to hike or bike.

This shift towards nocturnality could have more ecological side-effects than are currently apparent. For example, a predator who starts hunting at night may kill and eat more night-active animals than day-active animals, shifting the balance of populations of one species over another. Furthermore, animals who are adapted to day-living may not forage, hunt, communicate, or mate as effectively in the dark.

"Just because we don't see wildlife on a daily basis doesn't mean it's not out there," Gaynor said. "It's important to be mindful of how our activities may be shaping animal behavior and habitat. We should all remember that we're sharing the planet with many other species—they're just taking the night shift."