By Dr Helen Morrogh-Bernard and Simon Husson, Borneo Nature Foundation

Dr Helen Morrogh-Bernard

We started studying orangutans in the Sebangau forest over 20 years ago, slowly coming to know the lives of over 50 individuals by diligently following them from dawn to dusk in the dense peat-swamp forest habitat.

Uncovering the secrets of orangutans in the wild takes a long time. They live largely solitary lives and have very long life histories, as they do not reach maturity until the age of 15 and females reproduce just once every six years. While most days follow the same pattern: an early start at sun-rise, slowly moving from fruiting tree to fruiting tree to find all the food they need for them and their infant, occasionally meeting another orangutan for the briefest of interactions before making a nest to sleep in at the end of the day; every now and again they will do something that amazes you, and even something new to science! The first time we saw their self-medication behaviour was a case in point. At first we thought Indah had found a Dracaena shrub to eat the leaves from – but then we realised she was just chewing the leaves to form a paste which she spent half an hour rubbing onto her upper arms.

Later on we found out that this plant contains a powerful anti-inflammatory agent, so it seems she was treating her aches and pains – not surprising perhaps considering they spend so much of their lives hanging from branches! Since our first discovery of this behaviour we have witnessed it 2 or 3 times a year, and nearly every female in the population does it, passing the behaviour on to their offspring. Remarkably Sebangau is the only place where this behaviour has been recorded, so why is it unique to this forest? Intriguingly, indigenous Dayak people in the nearby village use the same plant for much the same reason, to treat their limbs for rheumatism and strokes, leading us to wonder who learnt the behaviour from whom, the orangutan or us? Whether there is a link or not, it’s clear we still have so much to learn.