Q＆A

What does “orangutan” mean?

Orangutan means “people of the forest”. In Indonesian or Malay, “orang” means “people/person” and “ utan (coming from the word hutan)” means “forest”. So, for example, if you want to say “Japanese”, you will say “orang jepun”. However, this name was given by foreigners and there is a theory that this is not how orangutans were originally called by the locals. Some of the local names for orangutans include: Kogiu, kahui, kisau and maias depending on the tribes. But now, the name “orangutan” is most commonly used even among locals.

What is their life expectancy?

To be honest, we still have no conclusion on how long they can live up to. Recently, it has been reported by a study that the Sumatran orangutan’s life expectancy could be at minimum 58 years for males and 53 years for females (At age 53, an orangutan was seen carrying around a baby so they might live even longer) (Wich et. al., 2004). Under the care of human hands, the world record for the oldest orangutan was a Bornean orangutan, Gypsy (female, Tama Zoo Park) who lived up to around 62 years old (passed away in 2017). For Sumatran orangutans, Puan (from Perth Zoo) lived up to around 62 years old (passed away in 2018) according to the Guinness World Records. For male orangutan, the oldest one was Bornean orangutan, Jojo (from Singapore Zoo) who lived up until around 61 years old (passed away in 2018).

Is the orangutan a smart animal?

Like chimpanzees, orangutans have high levels of intelligence next to humans. Orangutans can basically do anything that chimpanzees can do, like using their hands as well as sign languages, and being able to recognise themselves in front of mirrors (mirror-image recognition). They do not use equipment often in the wild , but when they are under human care or at a rehabilitation centre, they frequently use them. It is commonly thought that since chimpanzees are genetically closer to humans and, are smarter than orangutans. However, for example, gorillas, which are also genetically closer to humans, have the tendency of not being able to recognise mirror-images well, having worse results than orangutans. Recently, they are many studies on comparing the four great ape species (chimpanzees, bonobos, orangutans and gorillas) by carrying out the same experiment on each of them. We are excited to find out more regarding the intelligence of orangutans

What is their natural enemy?

The strongest and the worst predator is no other than us, humans. Currently, orangutans are under the threat of extinction by various activities carried out by humans. However, this kind of relationship between orangutans and humans is not new. Until at least 10,000 years ago, orangutans used to live across Asia: Thailand, Peninsular Malaysia, Vietnam, and, Southern China. One theory states that one of the major reasons why orangutans are not living across these vast areas anymore is due to the large-scale hunting done by humans. In several sites of ruin, together with bones of polyps, many orangutan teeth were discovered from the soil (Dobois, 1992; Hooijer, 1948) too. Hence, for the people living in the past, orangutans were also one of the major targets of their hunts. Other than humans, clouded leopards and Sumatran tigers were also thought to be predators of orangutans. At the rehabilitation centres, there are also cases where pythons eat baby orangutans. However, leaving babies aside, it would be very difficult for non-human animals to prey on such large, powerful orangutans that mainly live high up in trees.

What kinds of diseases/sicknesses do they contract?

We think that orangutans can contract basically any disease or sickness that we humans get. It is also reported that even in the wild, they have suffered from cases such as tuberculosis, hepatitis, Japanese encephalitis, dengue fever, malaria, and mumps (Wolfe et. al. 2002, Kilbourn et. al. 2005). Under human care, there are also cases of kidney failure, pneumonia, cancer and diabetes. At the Sepilok Orangutan Rehabilitation Centre, there were many orangutans getting contracted with pneumonia, bronchitis, and parasites. Some died because of the parasites (Kuze et al. 2008).

Is it true that the grip strength of orangutans is 300kg?

We often hear that orangutans have a grip strength of 300 kg, but there is no evidence to back that up. It might be true that they have that sort of strength as they live mainly on top of the tree and are able to hang just with one finger despite adult males weighing more than 80kg. However, to our understandings there is no scientific data and evidence to prove that their grip strength is 200kg or even 300kg.

What is a “Long Call”?

This is the voice made only by male with flanges. It starts with a bubble-forming sound and ends with a roar which could be heard even from 800m away. It is common to last for about 1 – 2 minutes but there are also those which last only for a short ten seconds. It is said to be a way of attracting females as well as to announce one's presence and keeping other males in check (Mitani 1985).
Listen to the voice

Are orangutans polygamous (having more than one wife)?

The ancestors of orangutans may have formed polygamous groups like gorillas (since sexual dimorphism is large; males are much larger than females). However, it is now considered practically promiscuous (both males and females mating with different orangutans). Female orangutans go through estruses only once every 6-9 years. During this period, they become fertile once every month from 2-3 days and unlike the usual day routine in which they avoid males, they proactively seek males. Males on the other hand, are constantly trying to go near females, and sometimes forcefully engage in sexual intercourse (there are researchers who call this ‘rape’). Unlike the chimpanzee which has ‘sexual skin’, orangutans do not have it so sexual intercourse can still take place without females needing to be fertile. Especially in Borneo, unflanged males frequently force sexual intercourses (Mitani, 1985) but this does not cause serious injuries to the female. Fertile females will have sexual intercourse with various males, and even flanged males cannot fully prevent females from having sexual intercourses by/with other males. Also, from the long research of DNA analysis which investigated the father-child relation in Sumatra, it was found that the child’s father varies greatly. There are also no results and observations obtained to prove one male dominates over many females or females only mate with a particular male (Utami et. al. 2002).

Do orangutans have territories?

No, they do not. Multiple orangutans can be in a same area/ region at a same time. At Danum Valley, we have observed two adult males, two adult females and two children on a tree (total of six orangutans) feeding and there were barely any quarrels or fights.
In the case of flanged males:
Flanged males are naturally hostile to each other, so they try to avoid each other. But in rare cases, when two flanged males come across each other (eg. near a female going through estrus), a violent fight erupts. There are reported cases which one died during the fight, and it is also common to find injured flanged males. Therefore, we could say that there is a strong hostile relationship between flanged males. However, flanged males treat unflanged males warmly and sometimes feed on the same tree together.

How far do they move in a day?

The daily average distance is around 500m, but it is not rare to find orangutans moving only around 100m. There are also at times in which they move more than 2km a day. It is also observed that there is a tendency for flanged orangutans to move relatively short distances and young orangutans to move relatively long distances, but the distance ultimately depends on the day-to-day situation.

Are orangutans the closest animal to us humans?

The closest animal to us humans are not orangutans but chimpanzees. The common ancestors of humans and chimpanzees separated only six million years ago, but with orangutans, it is 15 million years ago. Hence, chimpanzees are closer to us humans than to orangutans. For an easier understanding, chimpanzees and humans are siblings raised in Africa whereas for orangutans, they are cousins born far away in Asia.

Are orangutans carnivorous?

Regarding whether orangutans are carnivorous, they have been observed to have captured and eaten carcasses of slow loris on Sumatra Island and slow loris and squirrels on Borneo Island. et al.,2012; Buckley et al.,2015；Makur et al.,2022）。However, compared to chimpanzees, the frequency of them eating flesh is low (each animal has only been seen eating flesh once or twice a year). In general, wild primates are able to obtain sufficient nutrients from wild plants such as leaves and fruit.

In the wild, orangutans are said to be solitary creatures, but they have been found together in a group at zoos. How is this possible?

The reason wild orangutans live solitary lives is because fruit is scarce on Borneo and Sumatra Islands where they inhabit in comparison to Africa. In the “mass fruiting” season when fruits are produced in abundance, multiple orangutans have been spotted on a single tree. Therefore, they have a measure of social nature that enable them to cohabit with other individuals. In a zoo environment where food is abundant, it is thought that cohabitation with other individuals provide adequate mutual stimulation.

I’ve heard orangutans are facing the danger of extinction, so how many wild orangutans are there now?

It is predicted that in the island of Sumatra , there are more than 13,000 Sumatran orangutans and less than 800 Tapanuli orangutans , and in the island of Borneo, there are around 57,000 orangutans (Wich et. al.,2016；Orangutan Population and Habitat Viability Assessment 2016, 2019). But just note, in prehistoric times there were said to be 380,000 on Sumatra, 420,000 on Borneo, 340,000 on Peninsular Malaysia and at least 100,000 on Java Island (Rijiksen & Meijaard, 1999). It has also been said that the orangutans have gone extinct from Java Islands in the 17th century (Dobson, 1953).