A century ago, more than 100,000 cheetahs roamed the wild. Today, the majestic cats number fewer than 10,000—and conservationists and scientists have been trying to figure out why. One common theory: Bigger predators chased away the cheetahs’ prey, making it harder for them to get enough food.
A new study sheds light on another culprit: human-created barriers, such as fences and roads, that force cheetahs to travel long distances to find food.
The study tracked 19 cheetahs from two African parks to test the amount of energy they had to expend on different activities.
“If you mess with the environment and put up a road, fence, or house, you might not be killing animals outright, but you might force some animals to move differently or move further, which increases their energy cost,” said biologist Mike Scantlebury of Queen’s University in Belfast, who coauthored the study, which was published Thursday in Science.
He noted that in some parts of South Africa, cheetahs coexist with farmers, livestock, and dogs that protect those animals, forcing the cats to make longer journeys in search of prey.
Tracking cheetahs is no small feat. The researchers attached radio collars to monitor their movements and injected them with a type of “heavy” water that worked as a tracer.
The more rapidly the water was flushed out of the animals’ bodies, the more energy they expended. By collecting the cheetahs’ poop, they could see the real-time energy expenditure.
Not that it was simple.
“You’d be surprised—if you turn your back and not watch the cheetahs for a second, you’d have to try to find the poop buried in the sand,” said Scantlebury.
After two weeks of tracking the cats’ daily activities, the researchers were able to match each day’s action with each feline’s energy expenditure.
As expected, sleeping used less energy than walking. The animals’ overall energy expenditure wasn’t out of whack with that of other animals their size. “If you’re a person who is a marathon runner, you’d generally eat more than me,” said Scantlebury. “But although cheetahs are supreme athletes, they don’t eat more—their bodies are extremely efficient.”
Other things surprised the researchers: On days the cats were hunting down prey, they didn’t expend significantly more energy. Instead, it was on days they had to walk far that they used much of their energy.
On average, the cats spent 2.86 hours a day actively looking for prey, but those hours were responsible for 42 percent of their daily energy expenditure. Their chases, on the other hand, were “spectacular but brief,” said Scantlebury.
The researchers also found that the animals didn’t expend too much energy when lions and other predators stole their prey.
Scantlebury said that instead of blaming lions, it’s time to look at ourselves.