Animals that live near human activity are becoming nocturnal just to avoid us, and the implications for ecosystems around the world could be huge.
A team of researchers conducted a meta-analysis which included data about 62 species across six continents and found an overwhelming trend: To avoid encountering humans, animals are becoming nocturnal at the expense of their biologically predetermined schedules.
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Of the species studied that typically split their activity equally between day and night, more than 80 percent of those living near humans increased their nighttime activity. The new results were published in the journal Science this week.
"Catastrophic losses in wildlife populations and habitats as a result of human activity are well documented, but the subtler ways in which we affect animal behavior are more difficult to detect and quantify," lead author of the study Kaitlyn Gaynor said in a statement.
Rather than spend their days doing tasks relevant to survival, like foraging or hunting, these animals are sleeping.
By forcing their entire day to fit into the night, these diurnal species are restricting their diets, exposing themselves to new predators, and diminishing their ability to hunt.
And while you might expect this change in places where humans are hunting these creatures, increased nighttime activity is found no matter what the humans nearby are up to.
The analysis found evidence that animals alter their daily routines even when humans are doing something seemingly non-threatening, like hiking, near them.
It’s not rare for animals to switch things up so they can avoid potential hazards, but because humans are so widespread, there may be implications for the long-term survival of these species because of their shifting cycles.
"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," co-author Justin Brashares in a statement.
But it’s not all bad news. Animals that are able to adapt to a human presence likely have coexistence figured out, at least to some degree.
In fact, it's even possible that these animals may be using us in some way.
“Some animals may choose to associate more closely with humans in order to avoid predators that are more sensitive to human presence,” Clinton Epps, a wildlife researcher from Oregon State University who had no role in the study, explained via email. “This pattern is known as human shielding.”
So while these new findings are groundbreaking, they aren't exhaustive.
“This study is not intended to address every complexity but rather to identify broad patterns in animal responses to human activities,” Epps added.
But the research does pose many questions that will be important for future experiments.
For example, when did the switch to nocturnality occur? Which species are negatively impacted the most? What species benefits from this move the most? The answer to seamless human and animal coexistence might lie within these future results.