Orang-utan Classification and Evolution

The Orang-utan is one of the largest primates in the world and is the only member of the Great Ape family that is found outside of Africa. There are three species of Orang-utan found in the steamy jungles on the islands Borneo and Sumatra which are the Bornean Orang-utan, the Sumatran Orang-utan and the Tapanuli Orang-utan. The Bornean Orang-utan is more numerous and widespread than its cousins on Sumatra with three distinct sub-species of Bornean Orang-utan found in differing geographic regions on the island. Orang-utans are one of the closest living relatives to modern Humans and we in fact share 96.4% of our DNA with these forest dwelling apes. The three species are actually so similar in both behaviour and appearance that their name Orang Hutan in their native Malaysian communities, literally means "Person of the Forest". All three species of Orang-utan are today severely affected by Human activity in their native habitats and are listed by the IUCN on their Red List as Critically Endangered.

Orang-utan Anatomy and Appearance

The Orang-utan is a large arboreal animal which means that it spends the majority of its life high in the trees and therefore have evolved some very special adaptations to make living in the forest easier. As the Orang-utan is simply too heavy to leap like a monkey, they use their long arms to swing on the tree branches until they can get close enough to grab onto the next one. The hands and feet of the Orang-utan are both equally effective at grasping onto branches and their opposable thumbs also make their nimble digits very dexterous. The Bornean Orang-utan tends to be slightly larger in size than the Sumatran Orang-utan, which is more lightly coloured along with having a longer beard than its cousin. Tapanuli Orang-utans are similar in appearance to the Sumatran Orang-utan but have frizzier hair, smaller heads and flatter faces. Male Orang-utans develop fleshy cheek pads as they mature but these are much more pronounced on the faces of male Bornean Orang-utans, and all three species also have a throat pouch that is used to make deep calls that echo through the forest.

Orang-utan Distribution and Habitat

Although Orang-utans would have once been found on a number of the forested, tropical islands in Indonesia, today they are confined to just two which are the islands of Borneo and Sumatra. Their tree-dwelling lifestyle means that Orang-utans prefer dense tropical forests in the lowlands where there is an ample and varied supply of food. Along with also being found in hillside forests, in valleys and around peat-swamps, there are a number of isolated populations on both islands that are found in the high mountain jungles at much higher altitudes. The Bornean Orang-utan is found in three remaining locations on Borneo but the Sumatran Orang-utan now only inhabits the very northern tip of Sumatra, with the majority of wild individuals being found in just one province. The Tapanuli Orang-utan is found in a remote region in northwestern Sumatra with the entire population found in an area just 1,000 sqaure kilometres. All three species however are severely threatened by the drastic decline of their habitats which have been deforested for timber or cleared for agriculture.

Orang-utan Behaviour and Lifestyle

There are two big differences between Orang-utans and other Great Apes which are the fact that they are solitary and that they spend almost all of their lives high in the trees. The large size of the Orang-utan means that it moves very slowly through the forest but often because they spend so much of their time foraging for and eating fruits in the surrounding trees. They make nests to sleep in at night high in the canopy by folding branches over and padding them out with leaves to ensure a comfortable night. Although they do have their own patches of forest, Orang-utans are not particularly territorial and will even tolerate feeding together around trees that have an abundance of ripened fruits (Sumatran Orang-utans seem to be more sociable than Bornean Orang-utans). Male Orang-utans though will make their presence known by producing loud long-calls using their throat pouches to both intimidate rival males and to attract a female to mate with.

Orang-utan Reproduction and Life Cycles

After a gestation period that lasts for around nine months, the female Orang-utan gives birth to a single infant in a special nest built high in the trees. Young Orang-utans cling onto their mother's hair to stay secure whilst she is moving through the trees in search of food and are not fully weaned until they are three years old. However, Orang-utans will remain with their mother until they often seven or eight years old as she teaches them the skills they need to survive in the forest. This includes both learning about what plants to eat and where they can be found and also involves them being taught how to use tools such as sticks and leaves to make life easier. The Orang-utan is one of the most slow-developing mammals on the planet that cannot breed itself until it is between 12 and 15 years old. Females tend to have a maximum of three offspring during their life which means that in areas where populations have been affected by hunting or habitat loss, they take a very long time to recover.

Orang-utan Diet and Prey

The Orang-utan is an omnivorous animal that although does eat a mixture of both plant and animal matter, the majority of their diet is comprised of numerous types of fruit. Their large size and frugivorous nature means that Orang-utans must spend most of their day eating, which is possibly the reason why they have evolved to being semi-solitary animals. Despite the fact that Orang-utans do move throughout large home ranges, they have their own patch of forest nonetheless that tends to contain the perfect amount of food to sustain that individual (or a mother with young). Orang-utans eat both ripe and unripe fruits including mangoes, lychees, durian and figs which grow in abundance in some places and are where a number of individuals may meet up to feed. When there is a good fresh water source the Orang-utan collects it in its cupped hands then drinks it as it falls, but they don't need to drink too much as they get the majority of the moisture that they need from their food.

Orang-utan Predators and Threats

Historically, Orang-utans on both Borneo and Sumatra would have been threatened by a number of large, ground-dwelling carnivores which is possibly why they have evolved to lead an almost completely arboreal life. Large felines such as Tigers and Clouded Leopards are the primary predators of the Orang-utan, along with Crocodiles and the occasional large Asian Black Bear. However, due to drastic deforestation in both Malaysia and Indonesia the population numbers of the Orang-utan's predators have fallen drastically with some being even more endangered today than the Orang-utans themselves. Humans are by far the biggest threat to the remaining Orang-utan populations as they have not only destroyed much of their unique forest homeland but also hunt and capture the young that are then sold into the exotic pet trade.

Orang-utan Interesting Facts and Features

The Orang-utan is a very distinctive animal in the tropical Indonesian forests with its bright, red and orange hair leading to it also being known as the Red Ape. The Orang-utan is not only the largest tree-dwelling animal in the world, but it is also one of the most intelligent. In order to make the most of the seasonal changes in the tropical rainforest, Orang-utans are known to make a mental map of where the different fruit trees are and when they will bare their ripened fruits. Like a number of other Great Apes, Orang-utans are also known to use tools to facilitate their lives in their jungle, often using sticks and branches to collect honey from bee hives or extract ants and termites from inside hollow trees. Although the exact tool skill -set seems to depend on individual populations they are really quite remarkable, with some Orang-utans actually known to use large leaves as an umbrella to keep the worst of the rain off, and also put smaller leaves on the soft pads of their hands and feet to protect them in thorny vegetation.

Orang-utan Facts

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Pongo

Scientific Name: Pongo pygmaeus, Pongo abelii, Pongo tapanuliensis
Type: Mammal
Diet: Omnivore
Size: 1.25m - 1.5m (4ft - 5ft)
Weight: 30kg - 90kg (66lbs - 200lbs)
Top Speed: 6kph (2.7mph)
Life Span: 30-40 years
Lifestyle: Diurnal
Conservation Status: Critically Endangered

Color: Red, Orange, Grey, Brown, Black
Skin Type: Hair
Favourite Food: Fruits
Habitat: Open grassland and plains
Average Litter Size: 1
Main Prey: Fruits, Bark, Insects
Predators: Human, Tiger, Clouded Leopard
Special Features: Red hair and longer arms than legs


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