The Sumatran orangutan is noticeable due to their long, shaggy orange hairs which cover their body. In males a ‘cape’ of long hairs hangs from the arms when they are outstretched.
They are distinguished from Bornean orangutans due to their fur being a lighter shade of orange and the Bornean orangutan being larger.
Males and females are different in appearance due to the presence of large pouches on the females cheeks known as flanges. Males and females look similar at birth. The flanges begin to develop around 15 years old and these continue to grow for the rest of their life. The size of the flange is also a show of their status within their area.
Their arms may be up to twice as long as their legs measuring as much as 2.2m (7.25ft) to help them with swinging through the trees. Their thumb is opposable to help them when climbing.
A Male Sumatran orangutan is often twice as big as the female. Males measure up to 1.5m (4.92ft) while females measure 1.2m (3.94ft) long. Males weigh up to 130kg (286.6lbs) and females weigh just 55kg (121lbs) at most. While they have similar weights to humans they are up to six times stronger.
As they are an ape they have no tail.
Sumatran orangutan’s are omnivores. The majority of their diet is fruit with a favorite being that of the durian tree. They will move around their environment throughout the year to areas where fruit is in abundance.
When fruit is hard to find they will eat a variety of other foods such as bark, birds eggs, flowers, honey, insects, leaves, roots, sap, shoots, small lizards and stems. On a rare occasion they have also been observed eating slow loris.
Much of their water needs come from their food but they do also drink from tree hollows and the dew off plants.
Male 130kg (286.6lbs)
Female 55kg (121lbs)
Male 1.5m (4.92ft)
Female 1.2m (3.94ft)
Wild 50 years
Record 62 years
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.
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.
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.
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
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.
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.’
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