What do orangutans like to eat most?

With around 15,000 plant species on Borneo, the forest’s food supply can be overwhelming for a small orangutan. 4,000 of these plants are on the menu of Borneo orangutans. It is therefore important that the orphans learn which plants are edible and which are dangerous! Our supervisors show the orphans what is edible and how it can be eaten. Here are some of the orangutans’ favorite foods!

Fruits of the genus Artocarpus

Have you ever heard of the tropical fruit jackfruit? A member of the genus Artocarpus trees, jackfruit is a very large fruit which, when opened, reveals a sticky, fleshy compartment inside with a delicious flesh surrounding the pips! The wild fruits of this genus that the orangutans find in the forest are very diverse. Some of them more closely resemble the jackfruit eaten by humans, others have juicy white or red flesh inside, and the taste is generally more acidic than that of domesticated jackfruit.

The fruits of the Artocarpus tree ripen during the fruiting season from December to April, and orangutans can eat and fill their bellies for hours. If they discover one of these trees, they will fill their bellies without ifs or buts. After a relaxing digestive nap, you can continue eating immediately. Oh what a life!

Calamus plants, but more popularly known as rattan

Disguised as a climbing plant, the palm tree can be found in Borneo’s forest all year round. Not only the palm tree itself is partially edible, but also its small fruits, which resemble the «snake fruit» and are quite sweet. However, orangutans eat not only the ripe but also the unripe fruits, which are very bitter for our taste.

The fruits themselves adorn the palm tree for only a short time. During the rest of the year, the pith of the rattan palm is a constant and much sought-after food source for the orangutans. But it’s not that easy to get at the pith, because the orangutans have to split the branch off the trunk to do so. Each rattan vine is superbly protected by layers of murderous spikes and thorns, so the orphans must learn to touch them with fingertips and teeth, and to pull the vines in the right direction, which also requires some strength. Young orangutans can’t do that yet. The caretakers then help them so that the little ones learn that the delicious part is inside the prickly shell.

Borassodendron bornensis, a species of palm

In heavy rain, the large, round leaves offer the orangutans excellent protection. But this tree is also a nutritious and tasty food source. The fruit resembles that of a small coconut, and depending on how ripe it is, the orangutans can enjoy the fruit in different ways. For example, when the fruit is not yet ripe, the orangutans must be strong to open the hard shell and get to the soft flesh, which resembles young coconut flesh. The young orangutans often ask their keepers for help to open the fruit with their machetes, but as the orangutans gain strength, they can use their strong jaws to do it themselves. When the fruit is ripe, the rind will turn yellow and can be bitten off and chewed to get at the pulp. Sometimes the orangutans spend a lot of time just eating one of these delicious fruits. At times they are even too impatient and eat the flowers!

cambium, a layer of tissue in the trunk of a tree

Located between the wood and the bark, this part of the tree is made up of cells that are immature but packed with nutrients. The cambium is an important alternative food source for orangutans when the supply of fruit is scarce. Orangutans usually choose tree species that have a thicker cambium and hold more water. When the orangutans are young, however, they learn from their foster mothers which trees have the best bark to bite on and peel off. Then they scrape off the soft layer of the cambium with their lower incisors and chew it thoroughly to get at the nutritious part.

Durio Lanceolatus, also known as Durian

Wild durians are probably orangutans’ favorite fruit! Their consumption is delicious, but not without problems for the orangutans – after all, «durio» means «thorn» in Indonesian. Sometimes the orangutans stuff their hands with leaves so they can tear open the spiny shell – so they’re using a tool!

The fruit is extremely foul-smelling but very tasty and contains many vitamins, calories and nutrients. The orangutans eat the flesh around the seeds but not the seeds themselves, which they spit out. So they plant their favorite fruit by spreading the seeds in the forest – this turns orangutans into seed spreaders. However, the durian season is often short, making the fruit even more attractive, and the orangutans never miss an opportunity to hang out in the durio trees during fruit days.

The sticky, sweet berries of the Macaranga Gingantea

Macaranga gigantea is a pioneer tree that grows in open areas of the forest, where sunlight can penetrate. Its huge leaves can be used as umbrellas or to line nests. The orangutans also like to play with them or use them as fans against mosquitoes. In the years when the trees bear fruit, they provide plenty of food for several months. The orangutans eat these fruits whether they are immature or ripe. We’re not entirely sure, but we think they’ll eat anything, skin, pulp, and seeds.

The fruit is prong-shaped, like a small berry, and the seed is no larger than a sesame seed. But the fruit grows in clusters, close together, so that the orangutans eat them like we eat grapes – for hours. However, their juice is very sticky, which is why orangutans’ mouths are coated with glue during macaranga season. The sticky coating forms a dark coating on the orangutans’ mouths, making them look like they’ve put on lipstick (just badly). Telltale we call this the Macaranga Mouth.