Plummeting cheetah numbers may be down to humans making them travel farther to find their prey, scientists have suggested.
Cheetah numbers have tumbled from 100,000 a century ago to less than 10,000 today, and it was thought that bigger predators such as lions had been monopolising the food available as habitats shrink.
It had been thought that competition with other predators meant cheetahs were not getting enough access to prey to fuel the enormous amount of energy they use in their super-fast chases, scientists said.
But a new study led by Queen's University Belfast has found that cheetahs do not actually use significantly more energy than other similar-size animals.
And they use up more energy in searching for their prey than in their infrequent sprints.
The researchers suggested human activities which reduced their prey or made it harder to track down was undermining the ability of cheetahs to get enough food.
The study followed 19 wild cheetahs each for two weeks across two sites in southern Africa, one in the Kalahari desert and the other in a wetter area, injecting heavy water into the animals before tracking them and collecting their faeces.
Analysis of the faeces samples showed how much of the heavy water they were losing each day and their energy expenditure, the scientists said.