Orangutan

## Red apes of the forest

Orangutans, whose name means “people of the forest,” live in tropical and swamp forests on the Southeast Asian islands of Borneo and Sumatra. These shaggy red apes are the largest arboreal mammal and the only great ape found in Asia. The other great apes - gorillas, chimpanzees, and bonobos—are all native to Africa.

Orangutans spend most of their life in the trees, swinging confidently from branch to branch. With arms longer than their body and long, strong fingers and prehensile feet, life in the trees works well for them. In fact, orangutans look a bit awkward on the ground, using their arms as we might use a pair of crutches or lifting those arms high above their head when they walk. Adult male orangutans are much larger than the adult females.

## Two species

There are some differences between the two orangutan species:

### Sumatran orangutan

Lives on Sumatra. The hair is longer and lighter-colored than the Bornean species. The adult male’s cheek pads, called flanges, form rigid half circles on the sides of his face and both males and females usually develop beards as they age.

### Bornean orangutan

Lives on Borneo. Adult males have much larger flanges and a large throat pouch. The hair is shinier, and the females rarely have any beard at all. Bornean orangutans are more heavy-set than the Sumatran species.

## Daydreamers

Orangutans are the loners and the daydreamers of the great apes. While the other great ape species are usually found in groups socializing, foraging, or playing, orangutans tend to be more solitary and seem to have a more internal approach to everything. While other great apes might go from tree to tree searching for fruit, an orangutan just sits in the forest canopy for hours on end until the location of the hidden fruit seems to mysteriously reveal itself and the animal swings over for its meal.

## Relaxed problem solvers

Scientists like to explain the orangutan’s unique approach to problem solving with this example: If a chimpanzee is given an oddly shaped peg and several different holes to try to put it in, the chimpanzee immediately tries shoving the peg in various holes until it finds the correct hole. But an orangutan approaches the challenge quite differently. It may scare off into space or even scratch itself with the peg. Then, after a while, it offhandedly sticks the peg into the correct hole while looking at something else that has caught its interest!

## Swinging through the treetops

Orangutans spend most of their lives in trees and travel by swinging from branch to branch with their long arms. They usually build a new nest every night but may occasionally reuse one. The apes also use leafy branches to shelter themselves from rain and sun, and sometimes they drape large leaves over themselves like a poncho!

## Fruit salads on the menu

Primarily fruit eaters, orangutans also eat leaves, flowers, bark, termites, ants and other insects, and even bird eggs. Their mornings and afternoon are spent foraging for these food items, with naptime spent during the midday’s heat. Sometimes several mothers and their young encounter each other by a fruit tree within their overlapping ranges. They peacefully feed together and watch their youngsters play. Adult males, however, generally don’t care for company—especially with other males.

At the San Diego Zoo, the orangutans are offered cabbage, romaine lettuce, kale, carrots, yams, broccoli, bananas, apples, oranges, and grapes. Treats might include papaya, corn, turnip, onion, popcorn, raisins, peanut butter, and walnuts. The orangutan's motto is: food should never be boring!

## Watch out!

Sumatran orangutans, especially younger ones, have to worry about tigers, as well as other predators such as clouded leopards and crocodiles. To stay safe, they tend to spend more time in the trees than Bornean orangutans, which don’t have those predators on their island so can safely spend more time on the ground.

## The long call

Adult females have a home range that may overlap with another female’s. Adult males tend to be more nomadic, visiting female ranges as needed. If a male accidentally swings into a territory occupied by a more dominant male, the dominant male gives a booming roar called a “long call” to scare the intruder off.

The male orangutans’ calls also serve as an invitation to any available females within hearing distance. The females seem to be impressed by a male orangutan’s cheek pads, but the pads have another purpose. When males are fighting, they charge at each other and break branches. If that doesn’t scare one of them away, they grab and bite each other on the cheek pads or ears until one of them gives up and runs away!

## Life with Mom

Wild orangutan females usually have their first baby at age 15 or so. Newborns have pink faces that change to dark brown or black as they age, and look adorable with tufts of hair that stand straight up. For its first few weeks of life, the baby holds tight to its mother’s belly as she swings through the forest in search of fruit. When it is older and better at balancing, the youngster rides "piggyback" so it can see what’s going on. Like most mammal offspring, young orangutans are much more active than their parents. They are also more social and enjoy interacting and playing with other orangutan youngsters.

Orangutan youngsters stay with their mothers until they’re about eight years old, the longest childhood of the great apes. The solitary animals must learn all the lessons of finding fruit, building night nests, and other survival techniques before they set off on their own. Fruit trees are spread out over the rain forests where orangutans live, flowering and fruiting at different times. The youngsters learn a mental map of the forest layout and where ripe fruit is likely to be at any given time.