Study: Orangutans don't use much energy

ST. LOUIS, Aug. 3 (UPI) -- Orangutans in captivity are supreme "couch potatoes," scientists say, expending less energy in relation to body mass than almost any other large mammal.

Despite activity levels similar to orangutans living in the wild, animals studied at the Great Ape Trust, a 230-acre indoor/outdoor habitat in Des Moines, Iowa, used less energy than even sedentary humans, a release by Washington University in St. Louis said Tuesday.

"It's like finding a sloth in your family tree," study author Herman Pontzer, assistant professor of anthropology, said. "It's remarkably low energy use."

The study found an extremely low rate of energy use not previously observed in primates, but consistent with slow growth and low rate of reproduction in orangutans, Pontzer said.

This may be an evolutionary response to severe food shortages in the orangutan's native Southeast Asian rain forests, he said.

The rain forests of Borneo and Sumatra often experience crashes in the availability of ripe fruit on which orangutans depend.

Orangutans may have adapted to this over time by becoming consummate low-energy specialists, lowering their daily energy requirements to avoid starvation in food-poor times, Pontzer said.