The orangutan is the “human of the forest” and spend most of its life high above the ground, where it finds 90 % of its food.
The orangutan awakens from its nest in tree tops around 7 am in the morning and start foraging. The orangutan eats fruits, seeds, and grains, as well as termites, bark, and leaves. After several hours of feeding it typically rests in “day” nests during midday, before it resumes feeding in the afternoon. While feeding it travels distances of up to 3 km (800 meters on average), and consume around 5 kilos of fruit a day. At sunset it starts preparing for night time by construction a new sleeping nest in the trees. In total the orangutan spend around 40 % of its time feeding, 40 % resting, 10 % travelling and the rest of its time doing other activities such as mating, socializing and nest-building.
Orangutans eat a wide variety of plant species but are mainly frugivores (around 60% of their intake). On the menu is fruits, leaves, bark, nuts, seeds, bird eggs, fungi and honey. In total more than 500 plant species have been identified as being part of their diet, making orangutans the “gardeners of the forest”, as they disperse seeds across the rainforest floor. Water is mostly obtained from vegetation consumed, but can also be found collected in tree leaves.
The available food supply changes with season and between years, making the orangutan foraging highly adaptive. When fruits are scarce the orangutans spend up to 90 % of their foraging eating shoots and leaves. When fruit on the other hand is abundant, especially during mast fruiting occurring every two to 10 years in the dipterocarp forest, the orangutans consumption of fruit greatly exceeds their daily caloric need, thereby putting on additional fat stores.
Most orangutans build a new tree nest every night, providing a safe haven from predators. As such, the construction of nests is crucial, and young orangutans often build "practice nests" to honing their technique. Studies of the orangutan nest-building have found orangutans to have a great deal of engineering know-how. They know how to bend and weave large, flexible branches into a strong nest scaffold, and then they use fine, leafy branches on top to acquire a springy “mattress”. This construction can take as little as five minutes, taking place more than 30 meters above ground.
Orangutans usually travel in search of food, and day ranges vary between 100 and 3000 m, with an average of 800 m. Orangutans with larger home ranges (especially flanged males) travel the greatest distances per day (up to 3 km). The orangutans primarily travel by moving “quadrumanously” through the treetops, however recent studies have found them to be more terrestrial than previous thought (by the use of camera-trapping). As such, orangutans have often been observed walking along natural ridges or logging roads (Loken et al, 2015).
Culture and habits
Orangutans are very inventive. They use tools to catch termites, and they clean their teeth with twigs or thick grass. They collect rain water with leaves, and when it rains, they use a bunch of leaves as an umbrella. In fact, scientists have discovered social behaviours in different orangutan populations, constituting on what can be called orangutan cultures. In total, cultural transmission of at least 24 behavioural treats have been observed. These include:
- Using leaves as protective gloves or napkins.
- Using sticks to poke into tree holes to obtain insects, to extract seeds from fruit or to scratch body parts.
- Using leafy branches to swat insects or gather water.
- "Snag-riding," the orangutan equivalent of a sport in which the animals ride falling dead trees, grabbing vegetation before the tree hits the ground.
- Emitting sounds such as "raspberries," or "kiss-squeaks," in which leaves or hands are used to amplify the sound.
- Building sun covers for nests or, during rain, bunk nests above the nests used for resting.
Besides evolving a distinctive culture, the orangutans are also highly intelligent creatures with an eminent ability to copy human behaviour (such as fishing, bathing, washing of clothes and brushing teeths). Read more here >>