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We'd like to share some good news in honour of Indonesian National Primate Day, which falls on January 30th annually. The Kehje Sewen Forest has welcomed a new resident! Following confirmation from our veterinarian in October last year that Lesan was pregnant, we are thrilled to announce that she has since given birth!

Lesan was last seen around Camp Lesik at the end of 2022, with an enlarged stomach. Shortly after this, she was not seen for some time around camp, so our team suspected that she had already given birth.

Our team was right! Lesan and her firstborn, Ayu, were spotted around Camp Lesik on January 12, but this time they were not alone: Lesan was seen holding Ayu's baby sibling, her second offspring born in the forest!


Lesan’s protective maternal instincts and affection were clearly illustrated through her behaviour around her newest baby. When our team attempted to take photos, Lesan turned away to hide her baby. Even big sister Ayu went into protective mode and attempted to scare off our team members by shaking the trees and approaching them with her teeth exposed. Lesan and Ayu did a great job of teaming up to protect their newest family member from the prying eyes of human observers!

Lesan and Her Newborn Baby (Credit photo: Avita)

Lesan Eats Palm Fruit (Credit photo: Usup)

Lesan Holds Her New Baby (Credit photo: Avita)

Lesan Kisses Her New Baby (Credit photo: Avita)

Lesan, a rehabilitated orangutan who was reintroduced to the forest in 2012, is a success story not only for her ability to survive in the wild and reproduce, but also for raising Ayu to forage on her own and build nests in nearby fruiting trees. According to observational data made by our Post-Release Monitoring (PRM) team in the field, Lesan’s ability to socialise with other orangutans, act accordingly when encountering humans, explore her ranging area, and copulate to help create a new generation of forest-born orangutans demonstrates the success of the reintroduction programme. 

Orangutans are endemic to the islands of Borneo and Sumatra and are on the verge of extinction, thus various efforts are being made to protect them, including the BOS Foundation’s rehabilitation and release programme.

As an umbrella species that plays a vital role in forest sustainability, orangutans are desperately needed in the wild. We need them to remain in Kalimantan’s forest ecosystems, their true home. Therefore, we must prevent them from being exploited and protect them at all costs.

Happy Indonesian Primate Day!

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