African Elephants Avoid Hills, Satellite Tracking Shows

John Roach
for National Geographic News

August 3, 2006

African savannah elephants avoid traipsing up hills, even if the hills
have an abundance of food, according to a study that tracked the animals' movements over several years.

Scientists believe climbing hills costs elephants too much energy.

The finding suggests that conservationists must consider topography as they develop plans to protect elephants, said Fritz Vollrath, a zoologist at England's University of Oxford.

For example, migration corridors created for elephants should contain as little elevation gain as possible, running through valleys rather than mountain passes.

"Elephants can't afford to go over passes, so there might be a problem there," said Vollrath, who is also a chairperson at the Kenya-based charity Save the Elephants.

The finding poses a problem, however, because humans tend to settle in valleys, which contain water and good soil for crops. This may lead to potential conflicts between people and the migrating animals, Vollrath says.

And as human populations continue to swell, they are encroaching ever further into the elephants' traditional habitat.

(See an interactive feature with African elephant video, audio, fast facts, and more.)

Vollrath and colleagues Jake Wall and Iain Douglas-Hamilton report their findings in the July 25 issue of the journal Current Biology.

Caitlin O'Connell-Rodwell is a research associate who studies elephant biology at Stanford University in Palo Alto, California.

She says in an email that the finding could actually help reduce conflicts between humans and elephants by offering strategies to keep elephants away from human settlements.

"It is certainly worth considering the elephant's physiological limitations in any kind of deterrent plan," she said.

Energy Cost

According to Vollrath, walking uphill for elephants, which weigh 4.4 to 5.5 tons (4 to 5 metric tons), is like a human pushing a car uphill.

"That's a lot harder than pushing on level ground. … You put a lot of sweat into pushing up a hill, if you can even do it," he said.

In the current study, Vollrath and his colleagues calculate that a walk up a 328-foot (100-meter) hill requires an elephant to burn the energy it gains in a half hour of foraging.

"You have to spend a lot of time eating just to walk up a hill," Vollrath said.

Otherwise the elephants pay for the uphill hike with their body reserves. And unlike a car, he adds, elephants can't coast downhill.

"Walking downhill, if you are a hiker, is as much sweat as walking up hill," he said.

So when confronted with a hill, elephants prefer to take a detour along level terrain, the researchers conclude.

Tracking Elephants

The team's finding is based on tracking data collected from more than 50 elephants.

The elephants were fitted with collars that communicated their position to a satellite or cell phone every hour.

When the tracking data was plotted on a topographic map, the researchers noticed the elephants preferred to stick to level land, even when a hilltop promised abundant food.

"We have to look into this—the energy cost of terrain—and see how to integrate it into our conservation decisions," Vollrath said.

Stanford University's O'Connell-Rodwell says farmers in India are already taking elephants' aversion to hills into their planning.

"[They] have used the concept of ditches to prevent crop-raiding elephants, because elephants do not like steep inclines, in particular a steep decent and then steep rise," she said.

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