Orangutans are fascinating to observe. If you pay attention closely, you will uncover a world of exciting behaviours and interactions. For example, when several individuals come together and form a so-called ‘party’. Our Post-Release Monitoring (PRM) team and field staff often get to watch this behaviour while on patrols.
An orangutan ‘party’ describes the gathering of two or more orangutans in one location, at a maximum of 20 metres from each other, and within eyesight. Andrea Knox, our International Communications and Research Advisor, explains: “When we say orangutans are in a ‘party’, we don’t mean that they are dancing or sitting around a hotpot together. It simply means that they are together in one group, where the actions of one individual can be seen by another and potentially impact their behaviour.”
Despite being semi-solitary animals who spend most of their lives roaming the forest alone, orangutans will sometimes meet other orangutans and interact with them for a limited time. “Orangutans are what we call a ‘solitary but social’ species”, says Andrea Knox. Except for their juvenile years and mothers raising their children, they spend most of their lives almost entirely alone. However, all other great apes species, from gorillas to humans (yes, humans are great apes!), live in social groups. “It is highly likely that our shared common ancestor with orangutans from tens of millions of years ago was a social species,” Andrea adds.
Orangutans live primarily solitary lives because their evolution was influenced by the very challenging environment of Southeast Asian rainforests. As large mammals, orangutans require a lot of food, and if they lived in social groups, there might not be enough food for an entire group in one area. This pressure is what likely saw the orangutan evolve into a semi-solitary species, albeit with the capacity to socialise. If food is plentiful, and orangutans are familiar and sociable with one another, there is nothing to stop them from coming together in a ‘party’.
While Females often enjoy company, males are not known to ‘party’ together. Once a young female orangutan reaches maturity and leaves her mother, she typically does not travel far and will establish a home range adjacent to her mother’s. Due to this, the most common form of orangutan ‘party’ is that amongst related females.
Males that have reached sexual maturity will travel much further away from their mothers and, after growing cheek pads, are less likely to tolerate other flanged males in one group. When two adult males meet in the same location, they are more likely to exchange displays of dominance than eat fruit together.
Ayu Siti Nurika Agustina, our Camp Coordinator in the Kehje Sewen Forest, East Kalimantan, observed several orangutan parties while out in the forest. “On one patrol, I saw three mother-offspring pairs in a big fig tree. Lesan and Ayu on a low branch, Sayang and Padma in the middle, and Teresa and Berani at the top.” Lesan and Teresa groomed each other, and Sayang took care of baby Padma and Ayu (Lesan’s offspring) as she moved around the trees.
However, on another occasion, our PRM team spotted Theresa and Sayang fighting in front of Camp Lesik for a reason unknown to the team. This incident may demonstrate that orangutans can also experience ups and downs within their social relationships, just as humans do.
Eko Prasetyo, our Orangutan Conservation Specialist, who once served as Camp Coordinator, also shared his experiences with orangutan ‘parties’. He has seen male and female orangutans roaming the forest and eating in the same tree together over several days. This type of behaviour or ‘party’ between two orangutans of the opposite sex, known as ‘courtship’, usually ends in copulation.
Since the rehabilitated orangutans released by the BOS Foundation were raised in social groups in Forest School, many have formed strong bonds. Once they are roaming free in the wild, reintroduced orangutans do live primarily solitary lives but are more likely to gather in ‘parties’ than their wild counterparts. During her days in the Bukit Batikap Protection Forest, Andrea Knox and the team frequently encountered orangutans in groups and easily learned who were friends and who did not get along.
One afternoon, they encountered Cindy, Riwut, Cilik, and Olbert in a ‘party’. Riwut, the daughter of Cindy, was still very dependent on her mother and still lived with her. Cilik was Cindy’s firstborn who had already matured and lived independently but was still occasionally seen visiting his family. Then there was Olbert, an unrelated, sexually mature male who had yet to grow flanges. “While they all got along, I watched in amusement as all three vied for Cindy’s attention”, Andrea recalls.
Riwut was in a playful mood and motioned for Cindy to join her in rolling around on the ground. Cilik wanted to stay close to his mother during the visit and unsuccessfully requested food from her. Olbert, meanwhile, was clearly trying to win Cindy’s attention as a male suitor worthy of mating with. While Cindy gave some time and attention to each of them, Olbert ultimately won her affections – and that is how the team believes Cindy’s third child, Comet, was conceived.
As always, we are delighted to learn more about orangutans and share stories from our teams in the forest.