The Suaq orangutans show the most sophisticated and diverse behavioral repertoires of all orangutan populations. The rise of their complex culture may have been facilitated by the high level of social tolerance of the Suaq orangutans: since they tolerate even unrelated individuals close by, immatures and adults can learn from a broader variety of conspecifics. Thus, the probability that a new discovery of an individual will be passed on to other individuals is much higher at Suaq. This ultimately allows for knowledge and new techniques to be passed on from one generation to the next.

A stick tool made by Lilly. Photo Credit: Caroline Schuppli, February 2011.

Suaq orangutans use tools…

As a hallmark of their cultural complexity, Suaq is one of the only orangutan populations which shows habitual tool use in the foraging context. Tools are broken off, short, straight twigs of which the orangutans then often strip off the bark with their teeth and brush them at the end by chewing on them.

Mocca using a tool to get the seed out of a cemenang fruit. Photo credit: Anna Marzec, May 2015.

… to get seeds out of Neesia fruits…

At the edge of the Suaq peat swamp forest, there are Neesia trees (Neesia aquatica) with fruits filled with nutritious seeds, a highly preferred food of the Suaq orangutans. These seeds are hidden inside a football-shaped, extremely hard-shelled husk and protected by a mass of razor-sharp needles inside the husk. The orangutans at Suaq insert tools into the cracks of the fruits and by moving the tool up and down inside the crack, they detach the seeds and let them drop straight into their mouths.

Xavier using a tool. Photo credit: Mudin, May 2013.
Xavier using a tool to get sweat bees out of a tree hole. Photo credit: Mudin, May 2013.

…. and access to insect products.

The Suaq orangutans also use tools to feed on termites, ants or the honey of bees hidden inside nests or tree holes. They carefully insert the tool into the nest or tree hole, move it back and forth, then withdraw it and lick the insects or honey off. Most of the time, the tool is held clenched between the teeth; only the largest tools, used to hammer chunks of ter­mite nests, are handled. Suaq orangutans flexibly chose the appropriate tool in terms of length, thickness and even adjust it if needed. To avoid getting stung by bees the Suaq orangutans use leafy twigs to ward them off or sometimes wrap leaves around their hands, just like gloves.

Lisa, resting in her day nest. Photo credit: Caroline Schuppli, June 2013.

Suaq orangutans show sophisticated nest building techniques

Every evening orangutans build a nest high up in the trees to spend the night in. These nests are made of bent branches to which additional elements, such as pillows or blankets made of twigs and leaves are added. Before a rainy night, the orangutans at Suaq will add a roof on top of their nest or build their nests directly below an existing old nest to stay dry. Likewise, during their day naps, they build sunshields if they are too exposed. When being attacked by a bee swarm, the Suaq orangutans will build a nest in the leafy branches of a tree which they cover by a leafy roof. They will completely disappear in these nests to wait out the attack.

The culture of the Suaq orangutans goes beyond tool-use and complex nest building techniques and many facets of the Suaq orangutan culture still remain to be discovered.