Animals around the world are literally turning to the dark side in order to avoid contact with humans. According to a study published in the journal Science, human activity is disturbing the natural sleep patterns of the planet’s mammals, causing them to flee daylight and head for the protection of night.
Researchers at the University of California, Berkeley analyzed 76 studies containing data on the daily activity of mammals in response to humans for 62 species across six continents captured in a variety of ways, like using remotely triggered cameras, GPS, radio collars, and observations. Animals ranged from lions in Tanzania to coyotes in California.
The scientists compared how much time the creatures spent active at night under different types of human disturbance ranging from recreational activities like hunting and hiking to features like agriculture and roads. Across the board, animals that would normally split their time evenly between night and day spent almost 20 percent more time engaged in nighttime activity when humans were around. The findings were consistent across carnivorous and herbivorous large mammals (small mammals weren’t studied).
Why animals are forsaking the daylight shouldn’t come as a surprise – they’re avoiding humans out of fear. Animals respond to all types of human disturbance, regardless of whether those humans pose a threat or not – suggesting “our presence alone is enough to disrupt their natural patterns of behavior.” This “risk avoidance” could upset carefully balanced systems like food chains throughout the animal kingdom.
The researchers believe the changes in animal behavior could lead to mismatches between the environment and animals' innate traits. For example, they could change how they normally forage for food, leading to increased competition for resources. While the switch could also make normally dayside animals more vulnerable to nighttime predators, the researchers say it could prove beneficial by helping the animals avoid direct contact with people.
"On the positive side, the fact that wildlife is adapting to avoid humans temporally could be viewed as a path for coexistence of humans and wild animals on an increasingly crowded planet," said co-author Justin Brashares in a statement. "However, animal activity patterns reflect millions of years of adaptation – it's hard to believe we can simply squeeze nature into the dark half of each day and expect it to function and thrive."