Orangutans, large arboreal apes native to Borneo and Sumatra rainforests, have a diet central to their survival. Spending much of their day foraging, these primates adapt to varied food availability. Their diet not only sustains them but also plays a role in the broader ecosystem.
The Core Diet: Fruits and Beyond
Orangutans are predominantly fruit-eaters, with fruit comprising 60% to 90% of their diet when abundant. They prefer ripe, sugary fruits like durians, figs, and jackfruit, which provide essential sugars, vitamins, and hydration. They locate these fruits by remembering temporary food sources and tracking seasonal fruiting peaks across the rainforest canopy.
Beyond fruits, orangutans consume various other plant-based foods. Young leaves, shoots, and the inner bark (cambium) of trees are regular components, providing carbohydrates and fiber. They also eat flowers, buds, and mineral-rich soil. These supplementary foods become important when fruits are scarce, providing nutrients like protein from nuts.
Seasonal Shifts and Occasional Meals
Orangutan diets change seasonally, especially during fruit scarcity, known as a “fruit crunch.” During these times, they rely on “fallback foods,” which are less preferred but more readily available. These include a wider range of leaves, bark, and less palatable fruits. The cambium layer, found between wood and bark, becomes a significant food source, offering nutrients and water when other options are scarce.
Orangutans also consume opportunistic, supplemental foods, though these are not primary dietary components. Insects like termites, ants, caterpillars, and bee larvae provide valuable protein and fat; they even use sticks to extract termites. Occasionally, orangutans eat bird eggs and, rarely, small vertebrates like lizards, rodents, or slow lorises, especially when other food is scarce.
Beyond Sustenance: Their Role in the Forest
Orangutan dietary habits play a significant ecological role beyond their own sustenance. As large fruit-eaters, they are important seed dispersers. When they consume fruits, they often swallow seeds whole, which pass unharmed through their digestive system and are excreted in new locations.
This process aids rainforest regeneration and diversity, as many fruit seedlings sprout more effectively after passing through an animal’s digestive tract. Research shows orangutan-dispersed seeds often have higher germination rates. Their movement patterns, with males dispersing seeds over wider areas, contribute to broad plant species distribution.