The team trapped four wild mountain lions in the Santa Cruz Mountains and found they spent about 10 to 20 percent of their total daily energy taking down prey, which can be up to four times bigger than themselves. "People just didn't believe you could get a mountain lion on a treadmill, and it took me three years to find a facility that was willing to try," Williams said in a statement. To calibrate the collars, they put captive mountain lions on a treadmill and measured their oxygen consumption, then converted that to energy use. Williams and colleagues used specially designed radio collars to track the American predators' movement and speed. (Read more about mountain lions in National Geographic magazine.) Unlike cheetahs, mountain lions use sheer strength to take down prey such as white-tailed deer. In other words, Dollar says, "you want the biggest bang for your energetic buck." Wilson and colleagues' finding fits perfectly into an ecological theory called optimal foraging, which says an animal will spend the least amount of energy needed to get the most energy-rich food, says Luke Dollar, a conservation scientist and head of National Geographic's Big Cats Initiative. When prey is not scarce, cheetahs are able to rest most of the day because they eat high-calorie meals-impalas, mostly. "If they're going to spend more energy finding food than getting out of their food, that puts them in an energy deficit," Wilson explained. (Learn more about National Geographic's Big Cats Initiative.) ![]() Habitat development has led to fewer prey animals for cheetahs in South Africa. ![]() The big cats spent the most energy walking long distances to find food. In comparison, an African wild dog, which is smaller than a cheetah, burns about 15,000 kilojoules a day. The scientists were surprised to find that cheetahs spend about 9,000 kilojoules a day, less than the 12,000 kilojoules predicted as an upper end, says Wilson. When the cheetahs work hard, their bodies use the isotopes at different rates than when relaxing, so scientists get a measure of their energy use from the water in the cats' feces. The team injected the animals with water containing harmless isotopes, or chemical varieties, of hydrogen and oxygen. Scientists captured and tranquilized 19 wild cheetahs from wildlife reserves in the Karongwe and Kalahari regions of South Africa. So researchers wanted to learn whether food thieves might be forcing cheetahs to spend energy chasing down more food. Sporting more speed than brawn, cheetahs often lose their hard-won meals to more powerful rivals, like African lions. The studies, published Thursday in the journal Science, show that "these cats, in their own individual ways, figured out a way to make hunting cost-effective," Williams says. In California pumas, specially designed radio collars-think Fitbits for big cats-show that the ambush predators exert a huge effort to take down prey, but then make up for that the rest of the time by hiding and waiting. "I guess both humans and cheetahs rest a lot to offset high-energy activities," said cheetah-study co-author Johnny Wilson, a biologist at North Carolina State University in Raleigh. In fact, a cheetah's energy use is "remarkably similar" to that of a person who burns an average of 2,000 calories a day, or about 9,000 kilojoules. ( Watch an exclusive National Geographic video of the world's fastest animal.) The experiments tracked energy budgets for mountain lions in Santa Cruz, California, and cheetahs on two South African game reserves, measuring how many kilojoules of energy they use daily.Ĭheetahs keep their energy use low, the researchers found, even after accounting for their explosive bursts of speed when taking down prey. ( Read "Cheetahs on the Edge" in National Geographic magazine.)Īs people alter wild habitats, they may throw this delicate balance off-kilter and make it harder for big cats to make a living, scientists caution. The studies are the first to calculate the actual, minute-by-minute costs of being a big, wild carnivore-information sorely needed by scientists working to save big cats, says ecologist Terrie Williams of the University of California, Santa Cruz, who led the mountain lion study. Perhaps more surprising, though, cheetahs spend only about as much energy in a day as a person does, the scientists found. Like your pet kitty relaxing at home, cheetahs and mountain lions exert as little energy as possible and rest up for bursts of activity, two new studies reveal Thursday.
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