Orangutans are a semi-soiltary species, living independently and rarely interacting in adulthood. But one lineage of orangutans in Lamandau Wildlife Reserve has been surprising staff with unusual social interactions between siblings!
Sheila, born in the wild to an ex-captive orangutan in 2004, has gone on to have four of her own offspring. Orangutans are raised by their mothers for seven to eight years until she has another offspring, at which point the older one begins an independent life.
Sony (left), Sheila (middle), and Silva (right), 2022
Sheila’s third-born Sony has been living independently since 2021, when his mother gave birth to her latest offspring, Silva. It is however common for the older offspring to stay close by to his mother for several years – Sheila, Sony, and Silva can often be seen in close proximity to one another whilst foraging and exploring the forest. But of note are Sony’s recent interactions with his younger sibling.
Sony, 2025
At times, Sheila has been observed leaving Silva behind whilst venturing to a nearby tree for fruit or to the feeding platform. At four-years-old, Silva is still very much reliant on his mother and will cry when left alone - though Sheila doesn’t respond.
Sheila (left) and Silva (right)
Much to the surprise of staff, it has been Sony who on several occasions has come to the assistance of his younger brother, bending branches so that Silva can climb towards his mother, and even helping him down from taller trees. When Sheila is napping, Sony has even been seen playing with Silva to keep the young orangutan occupied.
Though orangutans are semi-solitary, siblings rarely interact in nature nor show any signs of recognising their relatedness. This unprecedented behaviour is a fascinating insight, posing many questions about this semi-solitary species and their relationships, only made possible through post-release monitoring.
Sony (left), Sheila (right) and Silva (top right)
