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The Ministry of Environment and Forestry of the Republic of Indonesia (KLHK), with the Natural Resources Conservation Center (BKSDA) of East Kalimantan, assisted by the Borneo Orangutan Survival (BOS) Foundation conducts its 25th orangutan release from Samboja Lestari Rehabilitation Center to the Kehje Sewen Forest. Meet the five lucky orangutans.


Riana was rescued from Bontang after being kept as a pet for four years. She had been chained around her neck to a tree, in an unshaded yard. A rescue team from the BOS Foundation, together with the Tenggarong BKSDA, had to cut the chain from her neck, which was scarred from years of being held captive in that manner. 

She was five years old when she first arrived at the Samboja Lestari Orangutan Rehabilitation Centre in East Kalimantan on 15 February 2018. She refused to drink milk or eat the fruits offered to her, as she had grown accustomed to being fed a diet of rice and tea. It took her quite a while to accept fruit, milk, and other natural foods. 

During her time at Forest School, Riana showed positive progress. According to the surrogate mothers, Riana is an intelligent, independent, and easy-going individual. She was good at socialising with other orangutans in Forest School and learned to recognise and forage for natural foods from her more experienced peers. 

Riana is active but not aggressive. She happily headed to Forest School alongside her friends every day without requesting to be carried by a surrogate mother or holding a surrogate mother’s hand. She also rarely played on the ground, preferring instead to remain in the canopy. 

After graduating from Forest School in 2020, Riana was moved to a pre-release island in Samboja. She showed positive progress for a year. Unfortunately, in 2021, she had to be moved to a socialisation cage after the pre-release island she was occupying experienced a landslide. At ten years old, Riana has grown into a beautiful, independent orangutan ready to be released to the wilds of the Kehje Sewen Forest. 


Mayer was illegally kept as a pet for two months by a resident of Muara Wahau, before being handed over when he was in poor health to the East Kalimantan BKSDA. 

On 12 May 2014, the BKSDA brought Mayer and another baby orangutan, Andreas, to the Samboja Lestari Orangutan Rehabilitation Centre. Mayer, who was under 12 months old at the time, had a poor appetite and was underweight. Like other newcomers, Mayer had to undergo an extended period of quarantine prior to joining Forest School. 

It didn’t take long for Mayer to adjust to his new environment. Within a year, a relatively short time, he was ready to move to the next stage of Forest School. Mayer has since grown into an active, healthy individual. Mayer is known for his independent nature and the little attention he gives to our surrogate mothers and technicians. 

From a young age, Mayer has exhibited aggressive behaviour toward other orangutans. He immediately gets angry if other orangutans disturb him and will chase them down to seek revenge. Mayer knows how to use his teeth to inflict painful justice. 

This 10-year-old, tough orangutan is waiting for his turn to be released back to the wild.


Together with Mayer, Andreas was brought to the Samboja Lestari Orangutan Rehabilitation Centre by the East Kalimantan BKSDA on 12 May 2014. As with Mayer, Andreas had been illegally kept as a pet by residents of Muara Wahau in East Kutai Regency, East Kalimantan, who only surrendered him after his health began to deteriorate. 

Andreas was just 12 months old when he arrived at Samboja Lestari and was suffering from severe diarrhoea due to a worm infection. His small body was very thin for an orangutan of his age. Our veterinary team faced great challenges in dealing with Andreas, as he was significantly traumatised by his negative interactions with humans. He was terrified of being touched and would scream and even bite when our vets tried to treat him. 

Our dedicated vets and surrogate mothers provided Andreas with the care and love needed to build his trust in them. While he grew accustomed to being handled by our veterinary team and surrogate mothers, he remained cautious of people he didn’t know. 

After undergoing a three-month quarantine period, Andreas gradually recovered and was able to overcome his fear of socialising. He gained more weight and grew thicker hair. Andreas was then ready to join his peers in Forest School. 

After a year in the small group, Andreas was ready to move up to a higher level of Forest School. In his new environment, Andreas had no difficulty interacting with his friends. According to the surrogate mothers, Andreas attained skills at a higher level than that of his peers. He was able to observe and imitate the skills of larger orangutans and became a very active explorer. 

Now, alongside Mayer, Andreas is ready to be released into the Kehje Sewen Forest. 


Leann was directly handed over to the Samboja Lestari Orangutan Rehabilitation Centre by a local resident of Bengalon, East Kalimantan, on 10 October 2014. She was around 3 to 4 years of age at the time. Leann was placed in a small Forest School group for about a year before finally joining a larger group. 

Leann experienced rapid development, and it didn’t take long for her to move through the different levels of Forest School. She actively played and practised her foraging and nest-making skills. Despite being somewhat of a loner, Leann still occasionally socialised with other orangutans. She graduated from Forest School and was placed on a pre-release island on 13 April 2020. 

On the island, Leann was still a bit of a loner; she would only gather with other females on the feeding platform in the mornings or afternoons when our technicians delivered supplementary food. Unfortunately, like Riana, Leann had to be moved to the socialisation enclosure after the pre-release island she was occupying experienced landslides following heavy rainfall and flooding. 

Leann occupies the same socialisation complex as Riana, Elaine, and Andreas. Initially, the team thought that Leann was becoming more social with her peers, as the females seemed to gather in the corner of the cage to eat food together and make nests out of leaves and stems. However, it has become more evident that Leann truly is more comfortable on her own, as she mostly ignores the other orangutans in her complex once her nest is completed and ready to lay in. 

Leann’s independent nature will definitely help her adjust to life in the wild when she is released to the forest. 


Elaine was handed over to the BOS Foundation by a resident of Bengalons. She had been kept as a pet for a month after allegedly being found in the resident’s back garden. She was 9 to 10 months old when she arrived at the Samboja Lestari Orangutan Rehabilitation Centre on 5 December 2011.

Elaine became attached to the surrogate mothers and technicians she had known for a long time. However, she acted differently when she saw a new person for the first time as her demeanour changed to become more noisy and dominant. 

As an active orangutan, Elaine was always determined to get what she wanted. She had resided on a pre-release island starting from 2018 – where she had become highly skilled at nest-building – until being moved to a socialisation cage with Andreas, Leann, and Riana after their island experienced a landslide. 

Elaine easily recognises natural food sources and has shown good progress, both during her time in Forest School and on the pre-release island. She is now 13 years old and is ready to be released into the Kehje Sewen Forest alongside Riana, Andreas, Mayer, and Leann. 

If you want to support our release efforts, please consider donating today!

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