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Orangutan orphan eating forest food

What do orangutans love to eat the most?

Our orangutan orphans learn to choose and eat from the menu the the Bornean forest provides 

23.7.2021

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!

Fruits from the genus Artocarpus trees

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!

Orangutan and Artocarpus

Calamus plants, but more popularly known as Rattan

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 One must learn how to touch it with fingertips and teeth, lips withdrawn, and pull in the right direction, which also requires quite some strength, and young orangutans cannot do that yet.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.

Calamus (Rattan)

Borassodendron Bornensis, a type of palm tree

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!

Borassodendron Bornensis

Cambium, a layer of tissue within the tree trunk

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.

Cambium of the tree

Durio Lanceolatus, other known as durians

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.

Smelly, but very tasty durian fruit

Macaranga Gingantea's sticky, sweet berries

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! 

Using the large Macaranga Gingantea's leaf for shelter and eating the berries

What it is like to be a foster mother to orangutans

Orangutan

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