 The birth rate for orangutans has been decreasing largely due to a lack of sufficient nutrients as a result of habitat loss.A 2011 study on female orangutans in free-ranging rehabilitation programs found that individuals that were supplemented with food resources had shorter interbirth intervals, as well as a reduced age, at first birth.The Bornean orangutan is more common than the Sumatran, with about 54,500 individuals in the wild, whereas about 15,000 Sumatran orangutans are left in the wild.