The island’s fruit bounty fluctuates, creating dips in orangutans’ food supply
The near-vegan lifestyle of wild orangutans in Borneo’s forests means the apes face recurring protein droughts severe enough that their body tissues start to waste away.
“They’re living on the margin,” says biological anthropologist Nathaniel Dominy of Dartmouth College.
Borneo, one of only two natural habitats for wild orangutans, is predominantly forested with trees that produce abundant fruit only about every five years. In bad years, the animals make do with a smaller volume of leaves and bark. During tough times, the apes average only about 1.4 grams of protein per kilogram of body mass per day, a tenth of what mountain gorillas consume, Dominy and his colleagues r