10 Intriguing Orangutan Facts

Orangutans Are the Largest Tree-Dwelling Mammal

Adult male orangutans grow up to 5 feet tall and can weigh as much as 300 pounds. Females, on the other hand, only reach about half that size — growing to about 3.5 feet and 100-150 pounds on average. Their hefty size makes them the largest arboreal, or tree-dwelling, mammals in the world. In fact, orangutans spend an estimated 95% of their time in trees, eating, sleeping, and traveling from tree to tree. In contrast, other apes are classified as semi-terrestrial — in spite of the fact that they also climb, nest, and travel in trees, albeit for less time.

Their Arms Can Stretch as Far as 8 Feet

Because of their large size and arboreal lifestyle, orangutans have huge arm spans that can stretch as far as 8 feet. These long appendages — in combination with their narrow feet and hands and opposable thumbs and big toes — help the animals move among the trees, also known as quadrumanous scrambling. Orangutans’ bodies have also adapted to their habitat by developing modified ligaments that result in extremely flexible hip and shoulder joints.  

Orangutans Can Live Up to 45 Years (Or Longer in Captivity)

Orangutans live between 35 years and 45 years in the wild. That said, they can live well into their 50s when living in captivity. Interestingly, though, orangutans are among the slowest animals to mature — males live alone until they find a mate, and females don’t reproduce until they’re in their teens. 

Fruit Accounts for Up to 90% of an Orangutan’s Diet

An orangutan’s diet consists of over 400 plant varieties, and includes bark, leaves, and fruit — with fruit accounting for between 60% and 90% of their food. This includes fruit that other animals don’t consider to be ripe as well as durians, a smelly fruit covered in sharp spikes that help orangutans compete for food. In addition to getting fats and sugars from fruit, orangutans get protein from eating nuts and carbohydrates from leaves. They also occasionally eat meat and generally spend as many as six hours a day foraging and eating.

Orangutans Build Highly Engineered Arboreal Nests

Because they spend so much time in the trees, orangutans are known for building complex arboreal nests that both protect them from predators and provide a place to sleep. These nests, usually from 30 to 60 feet off the ground, are built by weaving together branches, twigs, and leaves. Research on orangutan nest structure revealed that the animals use thicker branches to build the frame of the nest and smaller branches to create a more comfortable mattress. Orangutans build new nests every day, but sometimes reuse existing structures.

Male Orangutans Fight by Grappling and Biting

While orangutans are less aggressive than other primates, mature males do fight with one another during mating. This typically involves biting, scratching, and wrestling, and frequently leads to injuries — like missing fingers and eyes — or possibly death. Some male orangutans are also aggressive towards females, and females may exhibit aggression towards one another if there is a food shortage. 

They Nurse Until They’re Six Years or Older

Orangutan infants stay with their mothers until they are 6 to 8 years old, during which time they continue to nurse. This means that orangutans nurse their young longer than any mammal. Because of this extended child rearing period, female orangutans only give birth once every eight years.

Female orangutans stay close to their mothers even after they reach maturity, though males tend to migrate away from them and live more solitary lives. 

They’re the World’s Largest Seed Dispersers

Because orangutans eat so much fruit, they play an important role in spreading seeds. This ultimately helps to secure the continued availability of food and genetic diversity of plant life in their habitats. Once consumed, it takes approximately 76 hours for seeds to make it through an orangutan’s digestive tract, where they are then excreted — intact — in their feces.

Interestingly, the amount of time it takes seeds to travel through an orangutan’s digestive system has significant implications for long-term food supply. It has been observed that within 76 hours, females typically return to their home range, while males generally travel farther away and disperse their seeds across a wider geographic area. This ultimately leads to males depositing seeds in a way that spreads the genes of various plant populations across a much larger region, according to a study published in the Journal of Experimental Biology. 

Orangutans Use Tools

You may already be familiar with images and videos of orangutans using sign language and mimicking human behavior in captivity. However, these impressive cognitive abilities extend to the wild, where orangutans are known to use stick tools to accomplish tasks like removing seeds from fruit and extracting insects from holes in trees. Not only do orangutans use sticks for these activities, they choose sticks of specific lengths to accomplish particular tasks. 

What’s more, sticks can be used for scratching themselves and leaves are used for cleaning themselves, drinking, and protecting themselves when looking for food. Orangutans have also been observed making umbrellas out of leaves to protect themselves during inclement weather, according to research on orangutan behavior and ecology.

All Three Species of Orangutans Are Critically Endangered

Due to the pressures of logging, habitat destruction, and other sources of deforestation, all three species of orangutans are critically endangered and experiencing declining populations. Sadly, there are only about 14,000 Sumatran orangutans, 104,000 Bornean orangutans, and 800 Tapanuli orangutans currently in the wild. Orangutans are also threatened by the fires and smoke caused by land clearing in palm oil plantations, the poaching of infants to sell on the black market, and the hunting of adults for meat.