New research suggests human activity forces cheetahs to expend more energy, and is the ultimate cause of their population decline.

Cheetahs are down from a population of 100,000 a century ago to 10,000 today, in the past their disappearance has largely been blamed on large predators monopolizing their food sources, Queen's University Belfast reported.

In the first study of its kind, researchers found that even though they are the fastest runners, cheetahs do not expend more energy than other similar-sized mammals.

Cheetahs are believed to acquire more energy loss in searching for prey than in outbursts of running, which are relatively infrequent.

To make their findings the researchers looked at 19 free-roaming African cheetahs for two weeks across two sites, one of desert conditions and a much wetter region. The team injected heavy water into the cheetahs and tested their feces to determine how much of this water had been lost on a daily basis and thus calculate their energy expenditure.

"What we found was that the cats' energy expenditure was not significantly different from other mammals of similar size - cheetahs may be Ferraris but most of the time they are driving slowly. What our study showed was that their major energy costs seem to be incurred by travelling, rather than securing prey. If you can imagine walking up and down sand dunes in high temperatures day in, day out, with no water to drink you start to get a feel for how challenging these cats' daily lives are, and yet they remain remarkably adapted and resilient," lead researcher Michael Scantlebury from Queen's School of Biological Sciences said.

The large cats can even withstand predators such as hyenas stealing their prey. Human activity, such as erecting fences that keep over-hunted prey contained, are believed to be forcing the cheetahs to use up more energy by searching for prey.

"Too often we blame lions and hyenas for decimating cheetah populations when in fact, it is likely to be us humans that drive their declines. Imagine how hard it must be for a small cub to follow its mother further and further through the desert to look for food, while she herself is fighting for survival," manuscript co-author John Wilson of North Carolina State University said.

The findings were published Oct. 2 in the journal Science.