Orangutans

Why are orangutans important?

Orangutans need a large amount of space to source the food and water they need to survive so by protecting orangutan habitat, we also conserve a multitude of plant and animal species. In this way, orangutans act as an ‘umbrella’ species.

Orangutans help forests by distributing seeds in their dung, increasing the biodiversity of their habitat. Through their nest building each night, orangutans create gaps in the forest canopy, which allows light through, stimulating the growth of plants in the undergrowth. The new growth contributes to carbon sequestration and countering the impacts of climate change.

How to recognise different species of orangutan

From 1996, there were only two recognised species of orangutan – the Sumatran and Bornean. However, in 2017 a third species was identified in the Batang Toru region of Sumatra, Indonesia – the Tapanuli orangutan.

Distinctive due to their reddish hair and long arms (up to two metres span), the name orangutan means ‘person of the forest’ in Malay. Their skin is a dark grey and their hair can range from an orange to red. Their legs are short, being just over half the length of their arms. Male orangutans are twice as big as females and have large cheek pads which are thought to give a reproductive advantage.

Where do orangutans live?

As the largest tree-living mammal, orangutans spend over 90% of their lives high up in the forest canopy of Sumatra and Borneo – 15-100 feet above the ground – sleeping in nests built from folded branches and leaves.

A young orangutan © Robin Claydon

Orangutan behaviour

Orangutans often use tools, for example sticks to help them catch termites and collect honey, and have also been seen holding large leaves over their heads as shelter during rainstorms.

They have a semi-solitary social system, thought to have evolved in response to the seasonal distribution of fruit and the absence of natural predators in the forest canopy. Females and their offspring have the closest bonds, although young females, particularly those that are related, may also socialise together. Young orangutans stay with their mother for up to 7-9 years, learning the crucial skills they will need to survive in the wild – longer than most other mammals. Adult males are the most solitary, and only socialise with sexually receptive females for brief courtships.

Females usually have their first baby at 15-16 years old, with an average 8 year gap between births, so they are extremely slow at reproducing. Following a pregnancy of around nine months, infants are dependent on their mothers for the first two to five years of their lives.

Orangutans are generally non-aggressive. There is also little evidence of play behaviour in the wild, except for between a female and her offspring.

They can communicate in several different ways using a variety of gestures and vocal signals to communicate about resources, territory, dominance and affection. The vocalisations of orangutans are diverse and can include grunts, screams, ‘long calls’ where males start with barking notes and then changes into heaving roars and tapers off into groans, kiss-squeaks, grumbles and ‘raspberries’.