By injecting heavy water into cheetahs, the researchers could monitor the cats' feces to see how much water cheetahs excreted each day, as an indicator of energy use. Cheetahs expelled more heavy water (a rarer, but not radioactive, form of water also used in experiments with human metabolism) as the big cats went looking for food, rather than in the quick bursts used to chase prey down.
Given their reputation as speedy felines, ecologist Michael Scantlebury at the Queen's School of Biological Sciences in Belfast likens them to Ferraris - capable of incredible bursts of speed, "but most of the time they are driving slowly." During their slow drives, which consume most of the cheetahs' energy, the radio-collared cats walked around fences and trekked long distances in search of prey made scarcer by human competition, the scientists report in the journal Science.
"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," states Scantlebury, "and yet they remain remarkably adapted and resilient."