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 impeccable skills in learning which plants are editable, and which are dangerous! Our caregivers work with the orphans by modelling what and how to eat. Here are some of orangutans most loved forest foods!

Have you heard about the tropical fruit jackfruit? The jackfruit is a species from the Artocarpus genus tree, is a very big fruit that, when you open it, has a sticky fleshy compartment inside with a 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 human, and others are a bit different, with a juicy white or red flesh inside, and the taste is in general more acidic that domesticated jack fruit. Fruits from Artocarpus tree ripen in the fruit season which is 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 had their fill. Then they have a nap, and when they wake up from the nap, they start eating again. Oh what a life!

Edible parts of these palms that disguise themselves as climbers are found in the forest all the year. During part of the year, the plant produces some 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 constant and much-desired food source. But it is not at all easy to get to the pith, because it requires the orangutans to splice off the branch from the stem but each rattan liana is excellently protected by layers of murderous spikes and thorns. One must learn how to touch it with fingertips and teeth, lips withdrawn, and pull in the right direction, which also requires quite some strength, and young orangutans cannot do that yet. The caregivers then assist them so that the infants learn that the delicious part resides inside that spiky exterior.

The huge, round leaves provide exceptional shelter during heavy rain for the orangutans. But what this tree can also provide is 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 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. The 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 already eat the flowers!

This part of the tree is between the wood and the bark and 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 the nutritious part.

Wild Durians are probably the favourite fruits of orangutans! Eating them is delicious but not without its struggle for the orangutans – after all 'durio' means thorn in Indonesian. Durian fruits will split open and expel their seeds when mature, so ones has to open them along those split linesSometimes the orangutans fill their hands with leaves so that they can pull the spiky skin open – this is tool use!. The fruit is very smelly, but very tasty and has a lot of vitamins, calories and nutrients for the orangutans. The orangutans eat the flesh around the seeds but not the seed itself, which they spit out. , This makes orangutans seed dispersers – so they basically plant their favourite fruit by spreading the seeds in the forest. However often the durian season is short which makes the fruit even more attractive, and orangutans never miss an opportunity to be in 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 favourite forest food of orangutans. Its gigantic leaves can be utilised as umbrellas against rain or to pad nests, the orangutans also play with them or use them as fans against mosquitoes. 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 tine, like a small berry and the seed no larger than a sesame seed. But the fruits grow in umbels, close to each other so the orangutans eat them like we eat grapes, for hours. However, the sap is super sticky. Therefore, during the Macaranga season, the orangutans’ mouths are coated in glue, and bits of forest attach themselves to the glue. The sticky cover creates a dark coating all over the orangutan's mouths, so they look as if the applied lipstick (but poorly). Telltale, we call it the Macaranga mouth. The orangutans really love this fruit when it is available! 

Orangutans spend a long period with their mothers before they can be fully independent. During that time, they need to learn all the vital skills that will allow them to survive by themselves in the forest. This knowledge is passed from mother to child. However, in the event of the death of the mother, our staff must provide the environment and the right experiences to the orangutans where they can be able to learn all these skills, and at the same time, they teach the orangutans what the mother would do. Depending on their age, psychological condition and pre-knowledge, the orphan orangutans start at different levels of the rehabilitation programme and these are the vital skills they will need to learn in the programme to ensure their survival once they will be released.

is one of the most important skills for an orangutan to be able to survive in the forest independently. According to Schuppli et al. 2021, Wild orangutans individually consume around 100-200 food items, they are mainly frugivores, however they also eat leaves, flowers, piths, stems, bark-cambium and insects. Therefore, young orangutans need to learn what is eatable in the forest and avoid the plants that will harm them. They also need to learn where they will find the food and when is the season for each type of food as in some periods they will need to rely more on leaves and bark-Cambium.

Our teams onsite undergo botany training in order to learn about local plant species, and which ones are safe for consumption by orangutans, then they must transfer that knowledge to the orangutans taking the approach as an orangutan mother would; eating it themselves in front of the orangutan, that will bring curiosity to the orangutan and will imitate their subrogate mothers.

Our primary objective is to release orangutans into a life in the wild and it’s essential for their survival that they do not believe that all humans are good to them. That is why we take extreme care to limit the exposure of the orangutans to humans outside of the caretakers and orangutans must learn to discriminate between familiar, trustworthy humans and strangers whom they must not trust but avoid. 

Further on, they will need to recognise the dangers in the forest and how to avoid them, so they don’t get close to snakes or dangerous animals. 

When we want to teach orangutans that something could pose a threat we do as their mothers would: we go into hiding or try to repel the danger by shaking a tree, or a branch and giving warning orangutan calls.

Wild Orangutans build nests on an almost daily basis as a place to sleep at night or also as a place to rest during the day. Resting in the nest on the trees, provides more comfort to the orangutans, helping them in their mental and physical recovery while sleeping. The nest also has an anti-predator role, because that gives some camouflage and they are high in the trees.

They also reduce the risk of annoying insects that can bring diseases to the orangutans as ticks or mosquitoes, and moreover, the nest also provides more thermoregulation while sleeping. For all these reasons, it is also important that the orphan orangutans learn how to build a nest and get used to sleeping surrounded by leaves. The caregivers do daily nest-building classes for the orangutans, modelling and encouraging nest building by themselves.

Orangutans are arboreal primates, meaning they mostly move on the trees and their body is adapted to it with big shoulders, long arms, and feet that are more similar to hands so they can hold branches and trunks with them. The orphans need to have the right environment where they can practice how to move in the canopy, which branches are safe for their weight and which ones could break, as well as the safest way to transfer from one tree to another depending on the tree fortress. That is why our FOREST SCHOOL is the ideal surrounding for them to learn this kind of locomotion, however for us, as humans, we cannot really teach them how to do that, but what we can do is to be high on the trees with safety climbing equipment and encourage the orangutans to stay up on the trees to practices all this arboreal locomotion.

Even though orangutans are known as semi-solitary animals, they also have social encounters while they are in the wild, and developing social skills is also essential for them so that they can live in the wild with other orangutans. It is important that they have experiences not only with other orangutans from the same age, to play and explore the environment but also with older and younger orangutans – this gives them skills in how to read body language and when they can be the stronger or weaker playmates. 

They also can learn vital survival skills as nest building, locomotion or finding food from other orangutans. That is why in the FOREST SCHOOL, we sometimes mix individuals from different levels always under the supervision of the surrogate mothers. It provides these experiences with other orangutans they will not just develop their social skills but they will also learn other orangutans skills from each other.