Endangered Bornean orangutans survive in managed forest, decline near oil palm plantations

JULY 17, 2019

by Public Library of Science

Recent surveys of the population of endangered Bornean orangutans in Sabah, the Malaysian state in the north-east of Borneo, show mixed results. Populations have remained stable within well-managed forests, where there is little hunting, but declined in landscapes comprising extensive oil palm plantations, according to a new study in the open-access journal PLOS ONE by Donna Simon of the World Wide Fund for Nature—Malaysia, and colleagues. The study is the largest and most complete population survey of orangutans on Borneo, home to this endangered and endemic species.

Lowland forest is the most important habitat for orangutans in Sabah. Over the past 50 years, however, extensive logging and land clearance for agriculture caused habitat loss and fragmentation, which led to a drastic decline in their numbers, but the full extent of the effects on orangutan population have been difficult to estimate.

In the current study, the authors conducted aerial transects totaling nearly 5,500 kilometers across Sabah state, almost three times the length of a previous survey done in 2002-2003. Based on the number of nests, they calculated a population of 9,558 orangutans, including a previously unknown population of about 1,770 orangutans in many widely dispersed sub-populations.

Continued