Range

The Sumatran orangutan is restricted in range to just the northern portion of the Indonesian Island of Sumatra. Over 80% of their population is found in just one province, Aceh.

Habitat

They make their home in lowland, sub tropical broadleaf, riparian and montane forests, mountainous areas along with peat swamps.

Most of their habitat is primary forests with even small amounts of logging making a forest less likely to be inhabited by orangutans.

Reproduction

The Sumatran orangutan is capable of breeding year round. Peaks are seen in times where fruit is abundant. Females are said to be attracted to males with a larger cheek pouch.

Their interbirth interval (the time between births) is the longest of any land mammal and leads to a baby being born every 9 years. Sexual maturity is also not achieved until 12 years old for females and 15 years for males.

Both of these variables have contributed to their critically endangered status as it leads to the population recovering incredibly slowly.

Their gestation period lasts for 8.5 months. Twins are possible but due to the intense care given to young by their mother they will likely not both survive.

At birth the infant has a pink face but this develops to black as they age.

Young spend the first year of their life clinging to their mother. In the second year they begin to climb around on the mother. By year 3 they are starting to make small trips away from mum but still within her watch. They are weaned at 5 to 6 years old.

Females remain with their mother for up to 12 years in total. This is to allow them to gain the valuable skills they will need to raise their own young.

Once they leave mum a female will immediately establish her own territory while males will need to wait till they are mature and can challenge other males to maintain their territory.

Behaviour

They are able to communicate through a range of vocalizations. At present a total of 32 vocalizations have been recorded. Communication also takes place through expressions, gestures and touch.

Sumatran orangutans spend the majority of their life in the trees. Here they are safe from their predators.

Adult males are almost entirely solitary and will not tolerate another male in their presence. Females will on occasion come together to eat and also allow their young to play together at this time. A group of young males may also travel together for a few day’s at a time.

Males utilize a long call which can cover up to 1.9km (1.2miles) of forest and acts as a warning to other males to not enter his territory. It is also used to alert females to his present for mating. To assist with carrying this call they have a large throat pouch.

When males are fighting they begin by standing face to face with each other and then breaking branches. If this is unsuccessful they will charge one another and then bite the opponent on the cheek pouch in an attempt to win.

Predators and Threats

Predators of the Sumatran orangutan include Sumatran tigers, clouded leopards, large pythons and crocodiles. These primarily target young animals.

Humans present the largest threat to Sumatran orangutans. One of the largest challenges they currently face is logging especially for palm oil plantations. They are also under threat from logging and fires along with poaching. Poaching takes place for both the pet trade and bush meat.

Quick facts

The orangutan is found in Asia making it the only non-human great ape to not make their home in Africa.

Orangutans are the largest arboreal (tree-climbing) animal on Earth.

Sumatran orangutans are extremely intelligent. In many zoos they are known escape artists and have been known to break out of their enclosures in highly creative ways.

They have been seen to use tools. To get termites they will strip leaves off a branch and reach this in to the termite mound to extract termites to eat.

The word orangutan is derived from two Indonesian words which translate as ‘man of the forest.’