No rush to expend energy (Image: NGS)
They might swing in the canopy, but orang-utans expend fewer calories by mass than your average human couch potato. In fact, the only placental mammal that expends less is the sloth, according to Herman Pontzer of Washington University in St. Louis, Missouri, and his team, who analysed the apes’ urine (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1001031107).
An animal’s daily energy use usually increases in direct proportion to its mass. The heavier it is, the more energy it needs. But Pontzer’s team thinks the irregularity of food availability in the orang-utans’ habitat in south-east Asia has…
