35 orangutan individuals and 7 gibbon groups in the LAHG have been habituated to human presence and are regularly followed by a team of researchers. By August 2007 we have obtained nearly 10,000 hours of observations on orangutans and 1,150 hours on gibbons. Data are collected on their activity patterns, social interactions, feeding ecology, physical and nutritional health and ranging patterns. We are investigating how these apes adapt and live in a logged environment – how do they find enough food? What impact has logging had on their locomotion? Are they making selective use of their environment? Are they in good physical and energetic health? – as well as answering questions on these species’ social organisation, foraging strategies, cultural traditions and evolution. We have made some exciting discoveries, including the first observations of orangutans using plants for medication.

We have observed three instances of female orangutans using the leaves of a herbaceous plant for apparent self-medication using a method strikingly similar to that of forest-using people from the nearby village. They chew the leaves into a soapy pulp and then rub this methodically into their arms and elbow joints  - just as indigenous humans do to treat muscle aches and strokes. Records of self-medication in primates are rare, and most previous instances involve the ingestion of certain plant species to aid digestion or to treat intestinal parasites. Similar fur-rubbing behaviour has been seen in a few primate species, probably as a mosquito repellent or as part of their social behaviour, although these explanations seem unlikely in the case of the orangutan. We believe the most likely explanation of this behaviour is medication. To see film footage of this behaviour click on the links below.