Animals Are Becoming Nocturnal to Avoid Humans

January 5, 2020 at 6:18 pm

Mammals are staying up all night and sleeping all day to avoid contact with humans, having potentially disastrous effects on their health and overall chances of survival, study says

Foxes are one of the 64 mammals studied whose sleep cycle has been significantly altered by humans

Diurnal mammals are becoming nocturnal to avoid the stresses of humans encroaching on their habitats, a recent study finds.

Lions and tigers and bears – animals that used to hunt and play and mate during the day – are being forced to reverse their circadian sleep cycles to avoid human contact.

These wild mammals (along with 61 others studied) are apparently afraid of any and all interaction with humans, not just hunters, University of California Berkley researchers found.

Activities such as farming, mining, logging and urban development keep the animals lurching in the shadows during daylight hours, which they would otherwise spend in the sun.

Asian sun bears, for example, spends 80% of their waking hours soaking up vitamin D when undisturbed by human activity. But in areas where humans are pushing into their domain, they spend 90% of their waking hours in the dark, National Geographic reports.

Mammals have been diurnal for at least 65 million years, The New York Times notes. Forcing them into a nocturnal circadian rhythm could have untold consequences on the animals’ health and overall chances of survival.

Those include “consequences on fitness, population persistence, community interactions, and evolution,” the the researchers say.

Even human activity as seemingly innocuous as hiking and camping in the woods can cause animals to avoid the little natural habitat they have left during the day.

Coyotes in California’s Santa Cruz mountains are now sleeping during the day to avoid hikers and having to hunt an entirely new class of nocturnal prey at night, says Kaitlyn Gaynor, an ecologist at Berkeley.

In Africa, elephants are coming out at night to eat farmers crops, she adds.

On average, the 64 animals studied have become 20% more nocturnal, with some becoming much more so, depending on how much their habitat has been diminished.

“It’s a little bit scary,” said ecologist Marlee Tucker of Goethe University Frankfurt in Germany. “Even if people think that we’re not deliberately trying to impact animals, we probably are without knowing it.”