The new survey, looking at orangutan numbers on the Indonesian island of Sumatra, has found the population to be around double that previously thought. However, biologists warn the numbers still remain at risk from deforestation and industrial development.
Orangutans are Asian species of extant arboreal great apes, native to Indonesia and Malaysia. Following population decline, they are found in only the rainforests of Borneo and Sumatra. These apes are highly intelligent and can use tools and engage in complex social and cultural practices.
The Sumatran orangutan is classed as critically endangered, according to the International Union for Conservation of Nature (IUCN). This is due to a combination of poaching, habitat destruction, and the illegal pet trade.
Despite these risks, hopes are higher following a new survey. The survey was conducted by Serge Wich, who is a primatologist based at Liverpool John Moores University (U.K.) Through this survey, the population of the apes is now estimated to be 14,600 (the previous estimated was in the mid-6000s).
The reason why the numbers appear to have gone up is not because the risks faced by orangutans has lowered, but because the survey team examined areas previously unexamined. These included higher elevations, in logged forests, and in a remote area west of Lake Toba.
The new census is published in the journal Science Advances. See: “Land-cover changes predict steep declines for the Sumatran orangutan (Pongo abelii).”