STEVE INSKEEP, host:
One of the secrets to losing weight is simply to exercise more, burn more calories, move around. It can be hard work to raise your metabolism, but it could be worse. You could be an orangutan. A study of the apes revealed something about the different ways that animals use energy. NPR's Geoff Brumfiel reports from the National Zoo in Washington, D.C.
(Soundbite of crowd chatter)
GEOFF BRUMFIEL: It's a busy day at the great ape house. Parents and kids are running around, taking just a few seconds to stop and stare before rushing along. And on the other side of the glass sits an orangutan, looking out quietly at the crowd.
Ms. BONNIE POWELL: Doesn't it look lonely?
(Soundbite of laughter)
BRUMFIEL: Bonnie Powell and Gabe Kennedy are visiting from out of town.
Does he seem very energetic to you?
Ms. POWELL: No.
Mr. GABE KENNEDY: Not very. No. Not even close.
BRUMFIEL: Do you think he's lazy or...
Mr. KENNEDY: No. I don't think he's lazy. He's stuck in that small space. I couldn't live like that. I'd die.
BRUMFIEL: In fact, chances are this orangutan is feeling just fine.
Orangutans are apes that live in the trees of Borneo and Sumatra in Southeast Asia. They're used to lounging around on their own. In their native habitat, they're often solitary. They sleep around 12 hours each night and spend hours each day resting.
Professor HERMAN PONTZER (Washington University, St. Louis): They're not the most active animals in the world.
BRUMFIEL: Herman Pontzer is Washington University in St. Louis. He's interested in learning more about how apes and humans use food. It's a fundamental question, and the answer affects how animals evolve.
Prof. PONTZER: Evolution is a game of turning energy into kids. And so we wanted to understand how the human strategy for spending energy compares to our relatives, the living apes. And we found that, really, nobody had measured it directly.
BRUMFIEL: Actually, there's a reason for that. To measure energy consumption, scientists use something called the doubly-labeled water method. Basically, it involved measuring caloric intake using multiple urine samples.
That's difficult to do in the wild, but at the�Great Ape Trust�in Des Moines, Iowa, it turned out to be a lot easier. Rob Shumaker is a researcher at the Indianapolis Zoo who helped with the dirty work.
Dr. ROB SHUMAKER (Indianapolis Zoo): We walked around with some little paper Dixie cups and just held them underneath the ape and asked them if they would pee in the cup for us.
BRUMFIEL: And they did. After gathering the samples from the orangutans, scientists analyzed them to see how many calories the animals consumed. The work is published in this week's Proceedings of the National Academy of Sciences. It shows that, pound for pound, orangutans use less energy than any mammal ever measured, except for tree sloths. Herman Pontzer.
Prof. PONTZER: It was so surprising, that we actually went back to make sure that we hadn't done something wrong. You and I, sitting in front of our computers, use more energy each day than these orangutans that are walking around and climbing around and socializing around their big enclosures.
BRUMFIEL: So what's going on?
Prof. PONTZER: We think it's something deep in their physiology, that the metabolic processes that they're using to fuel their energy needs are just basically turned down.
BRUMFIEL: And that, Shumaker and Pontzer think, is because of their diet. In the wild, orangutans live mainly off fruit. But in the forests they call home, fruit can be hard to come by for several months of the year.
Prof. PONTZER: Individuals with lower energy needs have a better chance of surviving these potential starvation periods.
BRUMFIEL: The new study will provide zoos with the sense of how much to feed captive orangutans. But Pontzer says it can also help us learn about ourselves. He's now working with hunter-gatherer societies to gauge their caloric needs. Comparing the two will tell us more about how we evolved, and could even teach us how to manage our diets in the industrial age.
Geoff Brumfiel, NPR News.
(Soundbite of music)
INSKEEP: This is NPR News.
NPR transcripts are created on a rush deadline by Verb8tm, Inc., an NPR contractor, and produced using a proprietary transcription process developed with NPR. This text may not be in its final form and may be updated or revised in the future. Accuracy and availability may vary. The authoritative record of NPR’s programming is the audio record.