The orangutans that live in Indonesia are primate animals, just like us humans.
They are extremely intelligent and are known for having interesting traits not found in other apes.
They are also kept in zoos in Japan, but there may be a few people who have observed them carefully because they do not make very flashy movements.
In this article, we’ll take a peek together to see what characteristics orangutans have and what interesting secrets they have!



~ Basic information. ~

Mammalia-Primates-Hominidae-Orangutan genus.

Bornean orangutan.
Male length:120~140cm weight:70~90Kg.
Female length:80~100cm weight:50~70Kg.

Orangutans are primates, just like us humans, and are also called “apes” because of their high intelligence, especially among primates, similar to humans. (*There are five species of apes: orangutans, chimpanzees, gorillas, bonobos, and gibbons.

Apes basically form groups and act in groups, but only orangutans do not form groups and prefer to act alone.

Male orangutans reach sexual maturity and can reproduce at about 11 years of age, while females reach sexual maturity at about 7-8 years of age.

Males that have reached sexual maturity can mate all year round, but females ovulate once a month and accept males for only a few days, and if pregnancy is not established, menstruation occurs just like in humans.

Orangutan females go through a gestation period of 233-275 days and on average give birth to one orangutan baby once every seven years.

The bond between the mother and the child is so strong that the child lives with the mother until she becomes pregnant again and has another child.

Incidentally, in the wild, only females raise their children and males are not involved, but in zoos, males have been seen trying to help raise their children.


As adults, orangutan males may develop characteristic folds called “flanges” around their faces.

However, flanges can only be seen in a limited number of males, who have fought other males and are strong! This is a characteristic found only in males who think that.

Another interesting feature is that the more confident you become, the larger the flange becomes.

Males with large flanges, i.E., Evidence of strength, are popular with females, but when they lose confidence due to losing to other males, the flanges become smaller.




Orangutan’s Q&A.

How did the orangutan get its name?

The name “orangutan” is thought to have originated from the Malay word meaning “forest people. “Orang” is a word for a person, and “utan” is a word for a forest.

In fact, the orangutan has another name, “shojo” in Chinese characters. The shojo is an imaginary creature that resembles an orangutan, and is said to have red hair all over its body and love to drink.

Incidentally, chimpanzees, which are ape animals like orangutans, are sometimes called “kuro shojo” and gorillas are sometimes called “oh shojo”.


Why do orangutans live there?

Orangutans live only on the Indonesian islands of Sumatra and Borneo.

So why do orangutans live only in this limited area? The answer to this question becomes clear when we look at the lives of orangutans.

Orangutans are plant-eating animals, and 99% of their food is said to be fruits, leaves, and other plants. When I go to bed, I make a bed of branches and leaves on the tree and sleep. In other words, orangutans spend most of their day in trees.

For that reason, the body of the orangutan has arms twice as long as the legs, and the hands are made to be short on the thumb and long on the other fingers, making it suitable for living in trees about 30m above the ground. On the other hand, on the ground, you cannot run or jump quickly.

In other words, orangutans depend on tropical rainforests for most of their lives, including food and places to live, and can only survive in rich tropical rainforests such as Sumatra and Borneo.

In the past, in addition to their current habitat, many orangutans used to live in the Malaysian Peninsula and Java. However, we humans have cut through forests to use wood and to create ranches and fields, and we have reduced the number of places where orangutans can live.

The orangutans of Java are thought to have become extinct around the 17th century, although the exact reason and timing are unknown.


What do orangutans eat?

Wild orangutans feed on plant leaves and fruits, bark and flowers, and plants such as mushrooms and moss. 99% Of their food is plants, and depending on their habitat, they seem to eat at least 160 different kinds of plants.

In the case of fruits, they eat figs and durians, but like humans, they tend to prefer sweet and juicy fruits.

The remaining 1% of the food is insects (ant, termite, bee, etc.), But in rare cases, people have been seen licking the soil to replenish minerals and eating dead monkeys, birds, eggs, and other animals.

The orangutans living in the zoo eat a variety of vegetables (cabbage, carrots, sweet potatoes, Chinese cabbage, tomatoes, etc.), Fruits (apples, bananas, oranges, pineapples, etc.), And animal products (boiled eggs, dried fish, milk, yogurt, etc.).


How intelligent are orangutans?

Orangutans are said to be highly intelligent animals, along with chimpanzees. Its intelligence is thought to be roughly the same as a five-year-old’s if we compare it to a human.

Wild orangutans, who have nothing to do with humans, are also known to behave very intelligently.

In the case of wild orangutans, it has been witnessed that they use the branches of trees with many leaves like umbrellas during torrential rains, eat medicinal herbs to control parasitic infections, and chew medicinal herbs with their mouths to treat pain and inflammation, and then rub the juice that comes out into their bodies.

Incidentally, among the orangutans kept in zoos, surprisingly, there are orangutans who use iPads.

How he uses his iPad is that he acts like a human being, watching videos of orangutans like himself, watching anime, drawing pictures, and using game apps to his advantage.


Is it true that a new species of orangutan has just been discovered?

It’s true.Prior to 2001, orangutans were considered to be a single species, regardless of their habitat.

However, as a result of various studies, since 2001, the mainstream has been the idea that the “sumatra orangutan” distributed in Sumatra and the “borneo orangutan” distributed in Borneo are separate species, and that the orangutan is a total of two species.

Later, on November 2, 2017, a new species of orangutan was confirmed in Sumatra, surprising people all over the world. This is because it is very rare to find a new species of an animal as large as an orangutan.

The third newly identified orangutan, the “tapanuri orangutan”, was once considered to be a population of the Sumatra orangutan.

However, as a result of a bone survey, it was found that the tapanuriorangutan has larger canine teeth than other orangutans and is similar to the old type of orangutan that had been found as fossils, indicating that it is a new species.

At present, only about 800 tapanuriorangutans are thought to live in the area, and compared to the other two species of orangutans, there is a high possibility that they will become extinct in the near future.


What kind of personality is an orangutan?

Orangutans are considered to be relatively quiet and reserved.

Of course, males sometimes fight with each other over females, but males do not get angry when their children interfere with them when they are mating with females.

Also, unlike other apes such as chimpanzees and gorillas, there have been no cases of humans being attacked or injured by wild orangutans at this time.


Why do orangutans live alone?

Orangutans are the only animals among the apes that do not form groups and live alone. However, in fact, living in packs has the advantage of making it easier to detect natural enemies and having an advantage when attacked by natural enemies.

Why on earth do orangutans not form flocks despite such advantages? The answer to this question can be found by looking at the food situation in the forests where orangutans live.

The rainforest where orangutans live may seem rich at first glance, but the fruit they eat as their staple food only bears fruit once every few years.

There is a long period of time when there are no fruits in the forest, so if you form a herd, there is a high possibility that you will not get enough food, but if you live alone, you will be able to secure enough food to live on.

For this reason, it is thought that orangutans basically live alone and avoid contact with other individuals.

Incidentally, orangutans store fat by eating tens of thousands of calories of fruit a day during the period when there are many fruits, and survive by burning the stored fat during the period when there are no fruits.


How long does an orangutan last?

The lifespan of orangutans is not clearly known, but in the wild, the lifespan of Sumatra orangutans is thought to be 58 years or older for males and 53 years or older for females.

Gypsy, a Borneo orangutan from the Tama Zoo in Tokyo, Japan, and Puan, a Sumatra orangutan from the Perth Zoo in Australia, are said to have lived the longest in captivity. Both were females and died at an estimated age of 62.


Can orangutans be kept as pets?

I want to keep an orangutan as a pet because he is very smart and sometimes shows human-like gestures! Some of you may have thought about it. So can orangutans actually be kept as pets?

In this article, I will mainly focus on whether or not orangutans can be kept in Japan.

Orangutans are designated as “specified animals” by Japanese law, which can be dangerous to human life and property.

Since June 1, 2020, it has been completely prohibited to keep specified animals for pet purposes, and orangutans cannot be kept as pets in Japan.

Orangutans are also classified in “AppendixⅠ” of the Washington Convention. Since animals classified in AppendixⅠ are protected worldwide, it is determined that they cannot be traded between countries unless there is a special purpose such as research.

For this reason, orangutans are designated as animals that cannot be sold or bought for pet purposes.

As mentioned above, orangutans are normally prohibited from being kept as pets, but unfortunately, there are a certain number of people in the world who would like to keep orangutans as pets.

Especially in Indonesia, keeping orangutans is considered to be the status of being rich, and there seems to be no end to the number of people who try to poach and purchase orangutans even in violation of treaties and laws.


Orangutan babies are as cute as human babies, but as they grow up, they stop listening to others. There is no end to the number of cases where people have started keeping a pet without knowing it, and then have to let it go when they can no longer keep it.

Orangutans who were caught by humans when they were small and raised as pets do not know how to survive in the wild or how to raise children. As a result, the orangutans that are given away will not be able to return to the wild, will not have children, and will spend the rest of their lives in shelters and zoos.

I think we should think about how to relate to wild animals once again, to see if we need to sacrifice the freedom of orangutans to keep them as pets.

What enemies do orangutans have?

It is said that snakes are the natural enemies of wild orangutans.

Since many poisonous snakes live in Borneo and Sumatra, orangutans sometimes seem to fall victim to snakes.

Tigers also live in Sumatra, but orangutans rarely descend to the ground, so they are rarely attacked by tigers.


However, the orangutan’s biggest enemy is not snakes or tigers, but us humans. We cut through the rainforest and robbed more and more of the orangutans of their homes. As a result, over the past 100 years, the number of orangutans has decreased by 80%.

Orangutans are protected locally, but their habitat is actually declining, and poaching for pets or for meat continues to be a constant problem. In addition, even in national parks where animals and plants are supposed to be protected, there is no end to the illegal logging of trees.

It is said that one of the major factors that are reducing the habitat of orangutans is the plant oil palm. Oil palm is a plant that produces oil called palm oil, and palm oil is called “vegetable oil” and is used in all kinds of foods and cosmetics.

In order to mass-produce this convenient and easy-to-use palm oil, it is necessary to build oil palm plantations, but the price is that the tropical rainforests of Sumatra and Borneo are being cut open in large quantities.

It is difficult for non-locals to be directly involved in the protection of orangutans, but they can be indirectly involved in the protection. All we can do is try not to waste any resources and buy products that are working to protect nature.

Paper products that are produced using methods that have less impact on nature are marked with “FSC certification” and products that use palm oil are marked with “RSPO certification,” so by choosing and using such products, you can help protect the forests where orangutans live.




Type of orangutan.

・Bornean Orangutan
・Sumatran Orangutan
・Tapanuli Orangutan


久世 濃子(2018年)『オランウータン: 森の哲人は子育ての達人』東京大学出版会

金森 朝子(2013年)『フィールドの生物学11 野生のオランウータンを追いかけて マレーシアに生きる世界最大の樹上生活者』東海大学出版会




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