Bornean orangutans live in tropical rainforests, but because of logging that is destroying their habitat, the supply of fruit is shrinking. In order to survive, the orangutans eat leaves that they do not digest very well and bark when food is scarce. Living near starvation has some orangutans gaining their protein by digesting their own muscles. It is a desperate strategy, but these are desperate times.
Erin Vogel of Rutgers University in New Brunswick, New Jersey, studied wild orangutans for five years and found that when they go without fruit for several months, their urine contains nitrogen compounds indicating that the apes are digesting their muscles to get some much needed protein.
They have very little of their habitat left. If we want them around for very much longer and healthy, we will need to protect partially logged forests, maybe even create new ones, by planting more trees that they can consume. They are basically wasting away and consuming muscle cells.
We could learn from this as humans face the same situations when they are poor, or dealing with something like anorexia, for instance, where there is potential for humans to digest their own muscles for protein as well. Future studies will look at fluctuations in the hunger-related hormones ghrelin and leptin during periods of food scarcity compared to times of abundance. We may just learn how to keep our own species healthier in times of scarcity.