What Do Orangutans Eat? Fruit, Leaves, Bark and Insects

A fruit-based diet

All three orangutan species are frugivores, meaning that fruit is their favorite and most important food. When fruit is easy to find, they may spend most of their feeding time on it, often well over half and sometimes around 80% in good fruit seasons. Researchers have recorded several hundred different plant foods eaten by orangutans at a single study site.

Favorite fruits include:

• Wild figs, which ripen at different times throughout the year and are an important everyday food.
• Durian, whose large spiny fruits orangutans open with their strong hands and teeth.
• Fruits of forest trees and lianas (woody vines), often with soft, oily or sugary pulp around the seeds.
• Seeds, including hard-shelled seeds that orangutans crack with powerful jaws.

Because orangutans swallow many seeds and pass them later, often far from the parent tree, they help spread the seeds of many rainforest plants. For some plants they may be one of the few animals large enough to swallow the seeds, which makes orangutans important “gardeners” of the forest. Losing orangutans can therefore change which trees grow back in a forest over time.

What do orangutans eat when there is no fruit?

The rainforests of Borneo and Sumatra do not produce fruit evenly. Many trees, especially the tall dipterocarps, fruit together in “mast” years every few years, with long periods of scarcity in between. Borneo’s forests are particularly unpredictable.

During lean periods orangutans switch to fallback foods: young leaves, shoots, the soft pith inside plant stems and, above all, the inner bark (cambium) of trees, which they strip off with their teeth. Bornean orangutans eat much more bark than Sumatran orangutans. Field studies in Borneo have shown that orangutans lose body fat and burn their reserves during these hard months, then eat large amounts and regain weight when fruit returns. Slow movement and long rests help them save energy.

Leaves, flowers and honey

Leaves make up a steady part of the diet even when fruit is plentiful. Orangutans also eat flowers, the sap and young growth of vines and palms, and honey. They will break into nests of stingless bees and sometimes honeybees to reach honey and larvae.

Insects, eggs and the rare bit of meat

Orangutans eat termites, ants and other insects, which provide protein and fat. They open rotting branches and termite nests by hand, and Sumatran orangutans also use tools to reach them. Bird eggs are eaten when found.

Meat is rare. A few wild orangutans, mostly Sumatran, have been observed catching and eating slow lorises, and some Bornean orangutans have grabbed fish from shallow water. Compared with chimpanzees, which hunt monkeys regularly, orangutans are almost entirely plant eaters.

Soil and medicinal plants

In some places orangutans eat soil from mineral licks, termite mounds or riverbanks. This may supply minerals and help neutralize tannins and other bitter compounds in leaves and seeds.

Orangutans also use some plants in ways that look like self-medication. Bornean orangutans have been seen chewing leaves of a Dracaena plant into a foam and rubbing it on their limbs, and in 2022 a wild male Sumatran orangutan named Rakus was observed applying chewed leaves of a medicinal vine to a wound on his face, which then healed.

Mental maps and tools for finding food

Finding fruit in a huge forest is a challenge. Orangutans appear to remember where important fruit trees grow and when they are likely to fruit, and they travel directly to them. Flanged males even seem to plan their travel route the evening before and signal it with their long calls.

Tool use helps too. Sumatran orangutans in swamp forests poke sticks into tree holes to get insects and honey, and use small sticks to remove the stinging hairs that protect the nutritious seeds of Neesia fruits. Bornean orangutans use leaves as “gloves” and napkins when handling spiny or messy foods. Young orangutans learn which foods are safe and how to process them by watching their mothers for years; see how long do orangutans stay with their mothers?

Diet differences between the species

These differences reflect the forests they live in. Sumatran forests generally produce fruit more reliably than Borneo’s, which may help explain why Sumatran orangutans are more sociable and gather in larger groups at fruiting trees. Learn more about their homes in where do orangutans live?