The Red Ape story


In the Indonesian and Malay languages, the word orangutan translates literally as ‘Person of the Forest’, ‘orang’ being the word for person and ‘hutan’ meaning forest. Other names and spellings for orangutan are orang-utan, orang-utang, orangoutan, orango, orangután, orangutang, maias, mawas, and the Red Ape.

Orangutans are one of the Great Apes, in the order of Primatas (Primates) and genus Pongo (different from that of gorillas and chimpanzees). There are two species of orangutan: Pongo abeli, the Sumatran orangutan, and Pongo pygmaeus, the Bornean orangutan, which is subsequently divided into three further subspecies. The orangutan is the only non-human Great Ape that lives outside of Africa, as well as being the only ape with rusty, reddish-orange hair that covers its body (thus, the title Red Ape).

Orangutans are indigenous to the islands of Sumatra (Indonesia) and Borneo (comprised of states of both Indonesia and Malaysia). However, orangutans were once widespread throughout Asia and they thrived in India, Burma, China, Vietnam and Laos, as well as Indonesia and Malaysia. Today, orangutans are only found in pocketed areas of Sumatra and Borneo, with recent estimates putting their numbers at 6,000 – 6,600 and 50,000 – 55,000, respectively.

The primary threat to the orangutan’s survival is deforestation due to the proliferation of palm oil plantations on both Sumatra and Borneo. Palm oil, the most widely traded and used vegetable oil in the world, can be found in countless consumer items, from foods to cosmetics to shampoos and detergents. It can even be found in livestock feed and is now being used as a biofuel.


As stated above, the orangutan is the only Great Ape that lives outside of Africa, as well as being the only ape with rusty, reddish-orange hair that covers its body. The two orangutan species differ morphologically in hair colour and length, and facial features. Sumatran orangutans have elongated faces and longer hair, with lighter hair colour. Also, the cheek pads/flanges of Sumatran orangutan males are smaller than those of Bornean orangutan males.

There is large sexual dimorphism in orangutans, meaning males and females are easily distinguishable. The most obvious difference is the development of cheek pads/flanges in males; cheek pads/flanges very rarely develop in females. Another obvious differences is the difference in size between males and females. The weight of a female can range from approximately 70-110 pounds (31-50 kilograms). A female’s height can range from approximately 3 feet to 4 feet, 2 inches (1-1.3 meters). On the other hand, males can weigh between 130-260 pounds (57-118 kilograms) with heights ranging from 3-6 feet (1-1.8 meters). The weight and height of males can differ considerably according to their development into adulthood. Younger males without cheek pads/flanges are often labelled as subordinate/non-dominant/unflanged/sub-adult males. Once they develop cheek pads/flanges, they are labelled as dominant/flanged/developed males.

Orangutans are arboreal (tree dwellers) and the orangutan is the largest tree dwelling animal in the world. In order to sleep, the orangutan will build a nest in a tree by bending branches and leaves, occasionally using large leaves as an umbrella to protect itself from the rain. An orangutan’s movement in the trees is described as semi-brachiating, i.e., it does not travel through the canopy strictly using a hand-over-hand motion with its body suspended below its arms. The orangutan climbs and uses its legs, as well. Orangutans have an incredible arm span, reaching up to 7 feet, 5 inches in length (2.29 metres). Just because orangutans are classified as arboreal does not mean that they never come down to the ground. As opposed to other Great Apes who walk on their knuckles, orangutan locomotion is described as fist walking.

Orangutans are primarily frugivores (fruit-eaters), consuming over 150 different fruit species and over 300 plant species. However, they have been observed eating insects, soil and small vertebrates. There are only two reported cases of cannibalism in orangutans. The incidents took place in Bukit Lawang (Sumatra) one month apart from each another in 2007. Evidence for a third incident in 2009, also in Bukit Lawang among semi-wild orangutans, is still being examined before a full report is released.
Orangutans can be classified as solitary animals with semi-solitary populations. Within the primate world, this statement is highly debated because in captivity, orangutans show an incredible capacity and interest in being socialised. The classification of orangutans as solitary animals can also be debated because, as the home range of the orangutan is vast and mass fruiting seasons can occur in different areas of the orangutan’s home range at different times throughout the year, multiple orangutans are more likely to meet and tolerate or socialise with one another during these seasons than at other times of the year. There is, however, evidence of frequent displays of socialism in adolescent orangutans, primarily amongst females. Adolescent females are more tolerant of company than older females. Subordinate males may form relations with other sub-adult males, whereas a dominant male is unlikely to socialise with any other orangutan unless he is actively carrying out a courtship with a female that has reached reproductive maturity (between 11 to 15 years of age) within his home range.

Orangutan courtships can last as little as one day to a few months before the male and the female orangutan part ways. Unlike other primate species, the male may not know if the female is receptive or ready to conceive because, as with humans, orangutans have hidden estrus; that is, it is not apparent whether or not the female is in heat. Thus, when copulation takes place, it may or may not be timed to the period of high fertility in the female. Other primate species do show signs of estrus during times of high fertility.

Once a female has become pregnant, she may not bare another offspring until her child is 7 or even 8 years of age, the longest birthing interval of any non-human primate. However, depending on environmental conditions, the inter-birth period may be from 5 to 10 years. The gestation period is around 34 weeks and the female orangutan gives birth to one infant (twins are very rare). Offspring may weigh approximately 3.3-4.4 pounds (1.5-2 kilograms) and are born with a pink or light coloured face that darkens with age. Infant orangutans are dependent on their mothers until around 8 years of age and for the first three years of their life, will cling onto the mother’s hair on her back or sides when she moves. Orangutans are classified as juveniles until around seven years of age with an average weight of 54.7 pounds (25 kilograms). The juveniles become independent between 7-9 years of age and will then start to form home ranges for themselves, although female juveniles are likely to stay in home ranges nearby to their mothers. In the wild, orangutans can live up to 45 years of age and even longer in captivity.

Out of all animals, the orangutan has the longest parent-offspring bond/relationship; this period is only longer in humans. This is due to the complexity of the Southeast Asian rainforests and swamps where the mother must teach her offspring about the different types of fruit and plant species they can eat, where to find them, and what time of the year that they will be fruiting. The mother teaches her offspring everything they will need to know in order to survive on their own in the forest.


The easiest and most effective way of gathering a population census of orangutans is to conduct a transect nest count. Researchers rely on nest counts because orangutans can be hard to spot and researchers may not come across each individual orangutan. However, a nest is physical evidence of an orangutan’s presence in the area. All orangutans that are old enough and have been weaned from their mothers construct at least one nest a day, usually before stopping and going to sleep for the night. Scientists are able to approximate the length of time since an orangutan was in an area based on the decay rate of the nest. Although they can be effective, nest counts are not a totally accurate measure of determining population. One reason for this is the fact that infants that are still nursing do not build their own nests.

Both orangutan species are listed on Appendix I of CITIES and the World Conservation Union's Red List of Threatened Animals. From the Population and Habitat Viability Analysis Conference (PHVA) in Jakarta, 2004 it was announced orangutans numbered 6,600 in Sumatra and 54,000 in Borneo. Almost all Sumatran population are found in the provinces of Sumatra Utara and Aceh, with recent estimates 1 200individuals for Sumatra Utara and 5 400individuals for Aceh (Orangutan Indonesia Conservation Strategies and Action Plan 2009 ISBN:978-979-17217-1-4). Forest fragmentation has divided the Sumatran orangutan population into eleven differently-sized blocks with only three are reported to contain more than 500 individuals. The Sumatran orangutan remains critically endangered as declared by the IUCN Red List of Endangered Species and Bornean orangutans have been listed as endangered by the EN-US FWS since June 2, 1970.

There has been an estimated decline of over 80% over the last 75 years (assuming a generation length of at last 25 years Wich at al. 2008). The Sumatran orangutan population is in rapid decline and unless extraordinary efforts are made soon, it could be the first great ape species to go extinct. (Wich 2008). Protection of habitat is vital to the conservation and future well-being of the orangutan. One of the last strongholds of the Sumatran orangutan is a portion of the Gunung Leuser National Park located in the province of North Sumatra. The Leuser Ecosystem is the largest protected rainforest area in Southeast Asia. However, ecological diversity, along with orangutan populations and their home ranges in this area, continues to be diminished by logging and other human activities.


The orangutan is constantly at odds not with the forest, where it lives in harmony, but with mankind. Threats to the orangutan population range from the illegal pet trade to logging to the construction of palm oil plantations. The orangutan’s only predators are the Sumatran tiger, the clouded leopard, and humans, with humans creating the majority of the destruction to (viable) orangutan populations. Orangutans are completely dependent on the forests and the food sources found within the forests. If food resources are rich within the forest, there should not be any human-orangutan conflict; that is, assuming that humans do or will continue to extract foods from the forest while at the same time maintaining sustainability of these same food resources (PHVA Conference, Jakarta 2004). But within the last century, especially within the last 60 years, the Indonesian-Malaysian rainforest has been devastatingly damaged by humans.


OHP hopes to contribute to the continued existence of the orangutan through our research goals. Investigation of self-medicating behaviour in the wild orangutan is important for understanding how wild orangutans combat parasite infections that affect their health, reproduction and ultimately their survival. This understanding will also assist rehabilitation programs teach formerly captive orangutans how to keep themselves healthy, so they are more likely to survive in the wild after reintroduction. Additionally, as an integral part of OHP’s research is aimed at locating and studying plants consumed by orangutans that have potential medicinal properties, if a plant is discovered that possesses important medicative properties – not only for the orangutan, but for humans, as well – this likely would mean that the area where the plant is located would become protected, which means further protection for the orangutan’s natural habitat.

OHP is in the process of finding funding for the Batu Rongring Project in North Sumatra. Establishing a new educational and research facility in East Leuser block (one of the three where are reported to contain more than 500 individuals and only one in Sumatra Utara province) will have important implications for orangutan conservation. Establishing this permanent new research site will provide increased security from illegal logging, which is the biggest single factor affecting population declines. The proposed site will develop in-situ educational and research opportunities - essential to a greater understanding of the need for conservation and appreciation of the forest resource. The new site at Batu Rongring will allow us to engage with local community and promote the ideals of sustainable development, and at the same time encourage the community to find its own sustainable solutions to the various issues facing its people. In addition, studies have shown that the establishment of a permanent field research station with active field projects has had a positive impact on conservation of the areas being by the research station. It is OHP’s hope that the information gained through the research site at Batu Rongring will prove invaluable for effective orangutan rehabilitation, reintroduction, conservation and successful preservation of the species.

The fate of the orangutan is, ultimately, the responsibility of all of us (consumers and producers). Long-term, enduring steps are definitely required to save the orangutan from extinction. However, even something as seemingly inconsequential as deciding to purchase one chocolate bar over another because one contains unsustainable palm oil and the other does not, can help to make a difference in the orangutan’s future. We, as consumers, can educate one another and modify our habits, paying attention to whether or not our purchases affect the forests where the orangutan lives. If you are interested in doing something more, please do not hesitate to contact us or visit our web pages How You Can Help, Volunteer Program, or Project Assistant Vacancy. Or, you can even make a financial contribution.

Orangutan baby
Orangutan baby
Observation at practice trek
Observation at practice trek
Wild male
Wild male