With around 15,000 plant species on Borneo, the forest foods can be overwhelming to a little orphan orangutan. 4,000 of these plants are included in the Bornean orangutans’ diet, and thus it is essential that the orphans develop the skills to learn which plants are edible, and which are dangerous! The caregivers work with the orphans by modelling what and how to eat. Here are some of the orangutans' most loved forest foods!

Have you heard of the tropical jackfruit tree? The jackfruit is a species from the Artocarpus genus tree, which has a large fruit with a sticky fleshy compartment inside with that encases delicious meat around the seeds! The wild fruits of this genus that orangutans find in the forest are quite variable; some of them are more similar to the jackfruit consumed by humans, and others are a bit different, with a juicy white or red flesh inside. The taste is generally more acidic that domesticated jack fruit. Fruits from Artocarpus tree ripen from December to April, and orangutans can spend hours eating and filling their bellies full of them. Sometimes when they find one of these trees with lots of fruit, they refuse to move until they've had their fill! Then they have a nap, and when they wake up, they start eating again. Oh what a life!

Edible parts of these palms, that disguise themselves as climbers, are found in the forest all year round. During part of the year, the plant produces small fruits, similar to 'snake fruit', which is quite sweet, and these the orangutans love to eat. But they also like the unripe fruit which is very bitter to our taste. During the rest of the year, the pith of the rattan palm provides the orangutans a constant and much-desired food source. It takes quite a bit of work to get to the pith; the orangutans must splice off the branch from the stem while being careful not to injure themselves on the layers of spikes and thorns! One must learn how to touch the rattan with their fingertips and teeth, lips withdrawn, and pull in the right direction, to avoid injury. This skill requires quite some strength, and young orangutans often have trouble. The caregivers then assist them so that the infants learn that the delicious part resides inside that spiky exterior.

The huge, round leaves provide the orangutans with exceptional shelter during heavy rain. But this tree also provides a nutritious and tasty food source for the orangutans. The fruit is quite similar to that of a small coconut, and depending on the fruit’s stage of maturity, the orangutans can enjoy eating it in a multitude of different ways. For example, when the fruit is not yet ripe, the orangutans must be strong to open the hard shell to get the soft pulp inside, similar to young coconut meat. Young orangutans often ask for help from their caregivers to open the fruit with their machetes, but as the orangutans gain strength, they can do it themselves with their strong jaws. When the fruit is ripe, the skin turns yellow and can be bitten and chewed to get to the pulp. Sometimes the orangutans spend a very long time eating just one of these delicious fruits. And sometimes they don’t even wait that long and choose to eat the flowers instead!

The cambium is the part of the tree between the wood and the bark, which  is made up of cells that are not yet mature but are full of nutrients for plants growth. Cambium is an important fall-back food for orangutans when fruit availability is low. Usually, the orangutans chose tree species that have thicker cambiums and contain more water. However, when the orangutans are young, they learn from their foster mothers which trees have the best bark to bite open and strip off. Then they scrape off the soft layer of cambium with their lower incisors and chew it thoroughly to get to the nutritious part.

Wild Durians are probably the favorite fruits of orangutans! Eating this delicious treat is not without its struggles for the orangutans – after all 'durio' means thorn in Indonesian. Durian fruits will split open and expel their seeds when mature, so the orangutans have to learn to  open the fruits along those split lines. Sometimes the orangutans fill their hands with leaves so that they can pull the spiky skin open – a clever use of natural tools! The durian fruit is very smelly, but very tasty and has a lot of vitamins, calories, and nutrients for the orangutans. They eat the flesh around the seeds but not the seed itself, which they spit out--this makes orangutans seed dispersers. They basically plant their favorite fruit by spreading the seeds in the forest. However, the durian season is short, which makes the fruit even more attractive, and orangutans never miss an opportunity to explore the fruiting Durio trees.

Macaranga gigantea is a pioneer tree that will grow where the forest has been opened and sunlight can enter.  It is another favorite forest food of orangutans. Its gigantic leaves can be utilized as umbrellas against rain or to pad nests. The orangutans also play with the leaves or use them as fans against mosquitoes. Pretty clever! But in fruiting years, the trees provide plenty of food for several months. The orangutans will eat that fruit whether unripe or ripe. We are not entirely sure, but we think they eat it all, rind, flesh and seed. The fruit is tiny, like a small berry, with the seed no larger than a sesame seed. But the fruits grow in umbels, or clusters, close to each other, so the orangutans eat them like we eat grapes. However, the sap is super sticky. Therefore, during the Macaranga season, the orangutans’ mouths are often coated in sap, and bits of forest attach themselves to the sticky substance. The sap cover creates a dark coating all over the orangutan's mouths, so they look as though they applied a messy coat of lipstick! We call this telltale look the Macaranga mouth. The orangutans really love this fruit when it is available!