Lead
author, Liana Zanette, sets up the camera trap and speaker system in South
Africa's Greater Kruger National Park. Credit: Current Biology, Zanette et al.
Research
published October 5 in the journal Current
Biology finds that mammals living in South Africa's Greater Kruger
National Park, home to one of the world's largest remaining lion populations,
are far more afraid of hearing human voices than lion vocalizations or hunting
sounds such as dogs barking or gunshots.
Recent global surveys show that humans
kill prey at much higher rates than other predators. "We usually think
about the top of the food chain being large carnivore predators," says
first author Liana Y. Zanette, a conservation biologist at Western University
in Canada. "But what we're interested in is the unique ecology of humans
as predators in the system, because humans are super lethal."
"Normally, if you're a mammal,
you're not going to die of disease or hunger. The thing that actually ends your
life is going to be a predator, and the bigger you are the bigger the predator that
finishes you off," says co-author Michael Clinchy, also a conservation
biologist at Western University. "Lions are the biggest group-hunting land
predator on the planet, and thus ought to be the scariest, and so we're
comparing the fear of humans versus lions to find out if humans are scarier
than the scariest non-human predator."
As part of their South African
mega-experiment, Zanette, Clinchy, and colleagues observed how 19 different
mammal species reacted to a series of recordings, including human voices, lion vocalizations,
barking dogs, and gunshots.
When recordings of humans talking at
conversational volumes start playing, several different species of animals run
away. Credit: Current Biology, Zanette et al.
The human-voice clips, which were
at conversational volume levels, came from radio or television recordings of
people speaking the four most used languages in the region, including Tsonga,
Northern Sotho, English, and Afrikaans. The dogs and gunshots were meant to
represent sounds associated with human hunting, and the lion vocalizations,
curated with the help of lion expert and co-author Craig Packer of the University
of Minnesota, were meant to signal the presence of the top predator in the
region.
"The key thing is that the
lion vocalizations are of them snarling and growling, in 'conversation' as it
were, not roaring at each other," says Clinchy. "That way the lion
vocalizations are directly comparable to those of the humans speaking
conversationally."
To observe and record the animals'
behaviors in response to the recordings, the authors used custom waterproof
systems that combine a camera trap and a speaker—and have enough battery life to
record all day and night for many months. The study was conducted in the dry
season, and the systems were placed at waterholes to capture recordings of all
the animals coming to drink. By the end of the experiment, the team had 15,000
videos to sift through.
In response to lion noises, an elephant charges
and breaks the camera trap/speaker system. Credit: Current Biology, Zanette et
al.
"We put the camera in a bear
box, not because there are bears out in South Africa, but because of the hyenas
and leopards that like to chew on them," says Zanette. "One night,
the lion recording made this elephant so angry that it charged and just smashed
the whole thing."
The researchers found that animals
were twice as likely to run and abandon waterholes in response to hearing
humans compared to hearing lions or hunting sounds. Fully 95% of species,
including giraffes, leopards, hyenas, zebras, kudu, warthog, impala, elephants,
and rhinoceroses, ran more often or abandoned waterholes faster in response to
humans than in response to lions.
"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," says Clinchy. "The fear of humans is ingrained and pervasive, so this is something that we need to start thinking about seriously for conservation purposes."
Elephant
still image from camera recording. Credit: Liana Zanette / Western University
An
automated camera-speaker (labeled) used for the study. Credit: Liana Zanette /
Western University
The
team is now investigating whether their custom sound systems can be used to
deliberately steer endangered species such as the Southern white rhino away from known
poaching areas in South Africa. So far, efforts to keep rhinos away from
certain areas through the use of human voices have been successful.
"I think the pervasiveness of the fear throughout the savannah mammal community is a real testament to the environmental impact that humans have," says 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."
by Cell Press
Source: Fear of human 'super predator' pervades the South African savanna (phys.org)
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