Human activity affects wildlife and the environment in various ways that even some predators tend to be afraid of humans.

In a new study, researchers find that the mere presence of human voices affect the behavior of wildlife.

Predators Afraid Of Humans

For a new study, researchers conducted a novel experiment that shows how the presence of humans can create a “landscape of fear” even among predators such as pumas. At two locations in the Santa Cruz mountains that are closed to the public, researchers placed 25 speakers that played human voices and tree frog sounds in a 1-square-kilometer area.

Interestingly, in response to the human voices, pumas significantly reduced their activities, kept their distance, and moved slower. What’s more, researchers observed that the pumas avoided the area when they heard human voices but moved into the landscape if the frog sounds were played.

Similarly, other medium-sized predators avoided the area as well once human voice recordings were played. Skunks reduced their activity by 40 percent, opossums by 66 percent, and bobcats practically gave up daytime activity and became more nocturnal, perhaps because they felt safer.

Increased Small Animal Activity

In contrast to the predators’ reduced activities, smaller animals seemed to take advantage of the opportunity as the intensity of mice and wood rats’ foraging increased by 17 percent. In fact, deer mice’s range even increased by 45 percent once the predators were out of the way.

According to researchers, this might be because they were feeling braver because of the generally reduced activity from everybody else and took advantage to forage for more food. What’s more, compared to predators, mice are not too averse to humans.

'Source Of Fear'

Researchers note that compared to other studies that merely focused on the effects of development on the animals, their study focused on the direct impacts of humans on the animals and showed how humans triggered a change in the animals’ behavior and interaction with each other.

“Humans are incredibly lethal. We are major predators, and thus a source of fear, for a lot of these species. What's novel about this study is that we can see what that fear looks like in the environment at a relatively large scale,” said lead author Justin Suraci of UC Santa Cruz.

The study is published in Ecology Letters.