Animals in the savanna are more scared of the sound of a human voice than lions, dogs, or guns, a study found

• A new study showed that mammals in the savanna are more scared of human voices than lions growls.
• The scientists discovered this by playing sounds from humans, lions, and birds from hidden speakers.

Lions, sometimes considered the king of all beasts, aren't the scariest things on the savanna. Humans are.

Mammals in South Africa were twice as likely to abandon their watering hole when they heard human voices than when they heard lions growls, according to a new study in the journal Current Biology.

The study revealed that humans are the "super predator" of the savanna, Liana Zanette, a biologist at the University of Western Ontario who studies the ecology of fear and led the research, told Insider.

The researchers planted camouflaged cameras and speakers at different watering holes across the ecosystem. They'd then play the sounds of humans, lions, dogs, gunshots, or birds, and record the animals' reactions.

In the over 4,000 times that they ran this trial, Zanette and her colleagues found that animals' reactions to humans compared to other sounds that might signal danger was, "pretty remarkable. I think it still freaks me out."

The videos below show giraffes, warthogs, leopards, and more safari favorites running from their watering holes after the scientists begin playing recordings of humans speaking.

The environmental cost of fear

Even though fear is helpful for animals to know when to run from a predator, it also comes with a cost, Zanette explained.

Animals who fear a predator nearby eat less, run more often, and have more trouble reproducing. Fear can therefore lead to a reduction of overall population numbers, Zanette said.

Classical studies in the field looked at this phenomenon by considering apex predators like lions as the top of the line. But eventually, Zanette explained, scientists realized they needed to account for humans, because they kill prey at much higher rates globally than predators do.

Naturally then, the hypothesis is that prey animals would fear humans much more than any other animal. Previous studies have held up that hypothesis, looking at cougars in California and badgers in the United Kingdom.

But this is the first study to establish that fear of humans exists in species across the savanna, Zanette said.

The possible applications of it

Zanette said that the results of her study are, "kind of depressing." But, they might be useful in inventing new ways to prevent poaching.

By playing human voices in areas known for high animal trafficking, you might be able to keep new animals away, and save them from being picked up.

"It's possible that we might be able to use fear of humans as sort of a mitigation tool to encourage management and conservation," she said.