Orangutan information

Borneo Orangutan, female with baby.

This blog is very new and is under construction. If you would like to visit orangutans in the wild have a look at www.agoodplace.co.uk which has information on my orangutan holidays to the Tanjung Puting national park, Borneo.

There are two different species of orangutans : The Borneo orangutan (Pongo pygmaeus) and the Sumatran orangutan (Pongo abelii).

According to a report published by Oryx, the International Journal of Conservation the current remaining populations are estimated at 6500 in Sumatra and 50,000 in Borneo. To read a summary of this report published in July 2008 please visit http://agoodplace.co.uk/content/view/71/139/ and select "Sumatran Orangutan in serious decline" article.



Male Sumatran orangutan

Main differences between the two species :
Sumatran orangutans are smaller in size but have larger brains.
Bornean orangutans are slightly darker in colour and the males have wider cheek pads.
Compared to the Bornean orangutan the Sumatran orangutan is more frugivorous and insectivorous.
Wild orangutans in Sumatra have been seen using tools. They have been observed snapping off branches from trees and using them to dig in tree holes to find termites.
Sumatran orangutans are more social with this behaviour usually coinciding with times of heavy fruiting.
The Sumatran orangutan spends more time in trees rarely coming down to the ground possibly due to the danger of Sumatran tigers.
The Sumatran orangutan is classified as critically endangered by the IUCN (International Union for Conservation of Nature) and the Bornean orangutan as endangered.


Male Bornean orangutan with larger cheek pads than his Sumatran relative
Male orangutans enter adult hood at between 15 and 20 years old and develop their large cheek pads. The exact purpose of these cheek pads is still not known but their are several theories such as protecting the face during fights, helping to project their long call through the forest or simply a sign of adult maturity.

What do orangutans eat ?


A Bornean orangutan picking fruit in the Tanjung Puting national park, Borneo.

Orangutans spend about a third of their day hunting for food. They tend to mainly feed in the morning and late afternoon and rest in the middle of the day ... a very civilized life. About 60 % of their diet is fruit including figs and durain. They also eat young shoots and leaves along with occasional snacks of ants, bees and honey. Small fruit such as berries are picked with their fingers and larger ones are held in their hands whilst eating. In times of fruit scarcity they will alter their eating habits to consume lower quality food such as bark, leaves and termites. Water is obtained mostly from succulent vegetation and holes in trees.


The life cycle of orangutans :

A single baby orangutan is born after an 8 month pregnancy. In very rare cases they can give birth to twins but usually one of the babies will die. During the first year the infant is carried everywhere by its mother. The baby eats little or no solid food during this period relying on its mother's milk. After about 3 years old the infant will begin to forage for food sampling food that its mother eats. They begin to form teeth at about 4 months old but will continue to suckle up to the age of 6. After about 5 years of age the young orangutan will remain with its mother but is no longer completely dependent on her. It is still difficult at this age to distinguish between male and female orangutans. They enter adolescence between 6 and 8 years old and will start to make their own nests to sleep in. By this time the mother is likely to have given birth again and the first born will be spending more and more time apart from its mother. This long inter birth interval (of about 7 years) makes orangutans particularly vulnerable to extinction. After about 9 years old they will be independent from their mother and will enter sub adulthood. A female of this age may well still live in an area of forest close to its mothers but a male will usually move further away. Although they will occasionally meet other orangutans the males tend to live a live a solitary existence. Between the ages of about 12 and 15 females usually give birth for the first time. Male orangutans enter adulthood from about 15 to 20 years old and develop their large cheek pads and gain a lot of weight.



Life expectancy : In the wild orangutans can live up to about 45 years.
Weight : An adult male can weigh up to about 120 kilos. The females are much more petite typically weighing about 45 kilos. Sumatran orangutans are slightly smaller than their Bornean relatives.

Orangutan Behaviour
Orangutans are the largest tree living animals in the world spending most of their lives either sleeping or foraging in the forest for food. They build a new nest every night to sleep in and have been known to travel up to 4 kilometers in a day. They are of course expert climbers using their feet and hands to travel through the forest. Their weight prevents them from jumping from tree to tree and instead they tend to pull two adjacent trees together. If the gap is too far they will rock the tree they are using backward and forwards to bridge the gap. In the wild they rarely descend to the forest floor and have home ranges which are not marked or defended. They tend to be solitary or semi-solitary unlike most other apes and monkeys. In Borneo the largest group will normally be a mother with two offspring; one dependent and the other approaching adolescence. It is believed that this is due to sporadic fruiting which could cause conflict if they lived in large groups. In Sumatra they can exhibit much more social behaviour at times when fig trees fruit simultaneously. My first ever encounter with orangutans was in a forest near to Ketambe in Sumatra at a time of very heavy fruiting. There were over 20 orangutans happily hanging out together but this large group size is unusual.

Mating
Under normal conditions the only time the two sexes come together is to mate. Courtship lasts between 3 and 10 days with the male orangutan continuously following the female. They will mate frequently and during this period the male will often call out to deter other males from approaching. The long call of the male orangutan is a deep rumbling bellow that can carry for more than a kilometer through the forest. Eventually the female will initiate separation and the male then plays no further role in bringing up his offspring. A child support agency has been set up to try and get the males to pay maintenance but so far it has proved ineffective. The baby orangutan will then be dependent on its mother up to 7 years or so which prevents her giving birth again during this time. They are the slowest breeding of all primates and have one of the longest inter birth intervals of any land mammals. The female reaches puberty at about 11 years old but will generally have her first infant at about 13 years old. This means that with a life expectancy of up to 45 years she will normally only have 3 or 4 offspring in her life. This long birth interval makes them particularly vulnerable to extinction, especially those in smaller fragmented populations.
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