Humans Frighten African Savannah Mammals More Than Lions

With blade-like claws, immense rippling strength, keen eyesight, quick reactions and powerful jaws lined with sharp teeth, lions are predators that few animals would choose to confront. Their ability to hunt in groups makes them even more formidable.

"Lions are the biggest group-hunting land predator on the planet, and thus ought to be the scariest," conservation biologist Michael Clinchy from Western University in Canada said in 2023.

Humans provoke greater fear than lions

Yet, among more than 10,000 wildlife recordings from the African savannah, 95 percent of the species studied showed considerably more fear in response to the sounds of another animal. Humans are not technically apex predators, but we are the species other mammals appear to fear most.

In effect, we are the monsters beneath their beds.

"The fear of humans is ingrained and pervasive," said Clinchy. "There's this idea that the animals are going to habituate to humans if they're not hunted. But we've shown that this isn't the case."

In research published last year, Western University ecologist Liana Zanette and her colleagues played a range of calls and noises to animals visiting waterholes in South Africa's Greater Kruger National Park, then documented how they reacted.

This protected region supports the world's largest surviving lion (Panthera leo) population, meaning the area's other mammals are highly familiar with the threat posed by these carnivores.

Wildlife recordings at Greater Kruger National Park

The team broadcast recordings of people talking in local languages, including Tsonga, Northern Sotho, English and Afrikaans. They also used sounds associated with human hunting, such as barking dogs and gunfire, alongside recordings of lions communicating with one another.

"The key thing is that the lion vocalizations are of them snarling and growling, in 'conversation' as it were, not roaring at each other," said Clinchy. "That way the lion vocalizations are directly comparable to those of the humans speaking conversationally."

Some experimental participants were less than impressed by the work.

"One night, the lion recording made this elephant so angry that it charged and just smashed the whole thing," Zanette said, referring to the camera equipment.

That seems a perfectly reasonable reaction.

Nearly all of the 19 mammal species examined were twice as likely to leave the waterholes after hearing people speak than after hearing lions or even hunting-related noises. The animals included rhinos, elephants, giraffes, leopards, hyenas, zebras and warthogs, several of which can be dangerous themselves.

Human fear and savannah conservation

However, our fear of such animals seldom prevents humans from determining their fate. From bringing down enormous mammoths to managing the most dangerous modern dinosaur, we have taken on every challenge.

As by far the planet's deadliest animal, and a major force shaping evolution, humans have unfortunately earned every racing heartbeat of terror we create in other species.

"It was specifically hearing human vocalizations which inspired the greatest fear," the team explain in their paper, "suggesting that wildlife recognize humans as the real danger, whereas related disturbances such as barking dogs are merely lesser proxies."

Because humans are now so widespread, animals can only ever escape us temporarily. These mammals will therefore continue to have their fears repeatedly activated.

That is especially troubling for the already declining populations of numerous savannah animals, including giraffes. Earlier work by the team indicates that persistent fear on its own can reduce prey populations across generations.

Conservation biologists may also be able to use this understanding to protect vulnerable species. In South African locations known for poaching, they intend to play recordings of human conversations to discourage endangered Southern white rhinos from entering the area.

"I think the pervasiveness of the fear throughout the savannah mammal community is a real testament to the environmental impact that humans have," said Zanette.

"Not just through habitat loss and climate change and species extinction, which is all important stuff. But just having us out there on that landscape is enough of a danger signal that they respond really strongly. They are scared to death of humans, way more than any other predator."

The research was published in Current Biology.

An earlier version of this article was published in October 2023.