Orangutan babies know breast is best
The two remaining populations of orangutans – in Borneo and Sumatra – are both in serious decline, critically endangered. This is largely due to factors that include poaching, the illegal pet trade and habitat destruction.
But the orangutans' own slow rate of reproduction is also a factor. The reason for their slow reproduction has been poorly understood until recently.
A new study of orangutan teeth by Dr. Tanya Smith from The Australian Research Centre for Human Evolution has found nursing patterns related to food fluctuation in their habitat. The teeth show biomarkers for barium, which is ingested through maternal milk. In subsequent years barium levels change depending on the availability of solid food, usually seasonal fruit. This means that young orangutans return to maternal milk in years when fruit is in short supply. The pattern indicates that orangutans nurse for an astounding eight or nine years, longer than any other animal.
Because females reach sexual maturity at age 15, they are limited in the number of offspring they can produce in their average 45 to 50 year lifespan. This means orangutan numbers will be very slow to recover, if at all. The research was published in Science Advances: Cyclical nursing patterns in wild orangutans.