Orangutans are great apes and are one of humans’ closest relatives (“orangutan” means “man of the forest” in the Malay language). There are three species of orangutan, the Bornean orangutan (Pongo pygmaeus), the Sumatran orangutan (Pongo abelii) and the newly discovered Tapanuli orangutan (‘Pongo tapanuliensis’) of South Sumatra.
They are the only great apes that exist outside of Africa. Orangutans live about 45 – 55 years in the wild. Females reach puberty at around 10 but do not give birth until they are approximately 15 years old. Pregnancy lasts 8½ months, after which the infant suckles until age three. Even when weaned, the infant is carried by its mother until it is four years old and stays with her until it is between 6 and nine depending on each individual but generally about seven years old.
Females bear an infant only once every seven to nine years, so a female can produce, at most, four offspring over her lifetime unless on the rare occasion she has twins. Their slow reproductive rate is detrimental to who are endangered.
Orangutans live in rainforest trees. They search for food during the day and construct nest-platforms of leaves and branches for sleeping, often building a new one every night. Their diet is largely rainforest fruits, but they also eat leaves, shoots, bark, and other material.
Adults are usually solitary, except when About 2.5 square kilometres of prime habitat in Sumatra can support nine individuals. For each genetically healthy viable subpopulation, at least 500 individuals are needed because average home-range sizes differ, that means about 998 square kilometres per subpopulation in Borneo and about 595 square kilometres in Sumatra. All 3 species of orangutan are in crisis.
The major threats to the survival of orangutans are identified as habitat loss, mainly from conversion to oil palm plantations; habitat degradation; and habitat fragmentation.… Habitat loss is caused by forest conversion to permanent agriculture. Habitat degradation is caused mainly by timber extraction. Fragmentation is a by-product of habitat loss and degradation.
Animal populations shrink because the remaining rainforest cannot support all the refugee animals in addition to the normal populations already there. The displaced animals become stressed and may starve, be killed, or die because they cannot find enough food or unoccupied land for home range and feeding grounds.
Displaced orangutans, for example, have been observed to cause a “shock wave” of refugee crowding in adjacent forests leading to increased physiological stress and reduced reproduction. Habitat loss also makes it easier for the illegal wildlife traders to find the species they want to trade and steal them from the forest
All of the thousands of square kilometres of rainforest which have been destroyed for oil palm plantations in Indonesia and Malaysia in the past could have supported:
Bornean and Sumatran orangutans – 40 to 65 viable breeding subpopulations of 500 animals each
Sumatran rhinoceros – 550–650 rhinos
Asian elephant – 200–550 elephant families
Sumatran tiger – 400–670 tigers
When shrinking habitats push orangutans nearer to human settlements they raid fruit orchards and oil palm plantations, and get trapped or shot. One orangutan can eat as many as 50 young oil palm shoots in one raid so you can see why they are consider a pest by palm plantation owners and villagers when they raid their crops.
Sometimes plantation managers offer a bounty for each dead orangutan. Areas of oil palm disrupt animal social systems by hindering migration patterns and blocking travel corridors. A single plantation may cover an enormous area. In Indonesia, an average company manages a plantation area of about 40 to 100 square miles.
97 Large rainforest animals, such as elephants, tigers, and orangutans, need to be able to move over large distances under forest cover. To find water and food, young adults need to leave the family and establish their own territories in order to mate successfully.
Plantations block animals because companies do not keep corridors of forest available for animal movement. Furthermore, animals may be killed if they “trespass” onto the plantation or search for food outside the forest. Tigers and Orangutans frequently come into conflict with plantation workers.