Challenging Months in the Forest

The success of our orangutan reintroduction programs, which recommenced in February 2012, has been an amazing journey for all of us to be part of and such a joy to share our stories and lessons learned. The large majority of our orangutans have adapted well, though we have had experienced disappointments. We are continually learning so we can improve all of our processes from pre-release, release and post-release. This is the first time that orangutan reintroductions in Borneo have been so thoroughly prepared for and monitored post-release. We aim for high rates of success, and our post-release monitoring enables intervention if and when needed, but we have to be realistic in accepting that it is impossible to achieve a 100% success rate.

Natural mortality rates for wild orangutans are estimated to vary from 2-8% depending on age, with higher mortality rates occurring their first year, after independence from their mother, and after maturation for adult males. This means for every 100 orangutans we release, we would expect between 2 to 8 orangutans to die every year from natural causes. Obviously a reintroduction program should expect higher rates of mortality because of the historical backgrounds of our orangutans. The survival rate for rehabilitated orangutans released during their juvenile-adolescence years has been reportedly varied between 20-80% (Russon et al, 2009); significantly different to what we would expect within wild populations.

A rehabilitant orangutan in release site.

A rehabilitant orangutan in release site.

Following 28 months of reintroductions in Kalimantan and the release of 162 orangutans, we have recently experienced two losses in East Kalimantan, which have been difficult for all of our team members as we know each individual orangutan so well. Unfortunately these took place within a short time-frame. However, we remain committed to our task of reintroduction and post-release monitoring to reestablish new genetically viable populations of orangutans to bolster conservation of the species in the wild in the long-term.

The Departure and Return of our Orangutans

Maduri was released in Kehje Sewen Forest on March 20, 2014. Despite her best efforts to adapt in her new environment, trying several natural food and learning to live in the trees, she had faced difficulties since the beginning of her release. So the Post Release Monitoring (PRM) Team focused their efforts on closely monitoring her development daily. But on May 6, 2014 at 8.30 am, the PRM Team and the vet on duty found Maduri lying on the ground, lethargic and weak with a wound to her neck. At the time, the team was also intensively treating and caring for Kent, another orangutan who was also found with some serious injuries. So their concentration and focus were divided in two.



Our vet checked her condition and decided to evacuate Maduri to Camp 103. She immediately received intensive care including intravenous liquids and was encouraged to eat. Unfortunately, all attempts failed. Maduri sadly passed away at Camp 103 on May 7, 2014.

As the same time Kent, who was released on March 22, 2014, was found with open wounds to the nape of his neck, chest and left arm on April 30, 2014, which we believed were probably a result of conflict with another male. The PRM Team had previously witnessed a fight between Kent and Bajuri, another released male orangutan, on March 24, 2014 but no injuries had been observed.



It doesn’t take long for infections to establish in a wild setting, and in line with our procedures the vet and PRM Team decided to evacuate Kent to the acclimatization enclosure and provided intensive care. Our vet cleaned and treated his wounds daily and provided forest fruits as supplement.

His condition began to improve, he started to eat well and was very active. However, because Kehje Sewen was in fruiting season, it was swarming with bees. There were several bee hives around the enclosure and Kent’s condition worsened again due to bee stings. The bees did not just sting Kent but also stung our vet who was on site treating him. Annoyed and in pain from sting bites, Kent couldn’t help but scratch his body, which aggravated and worsened his wounds. The team tried to remove the bees through various methods but to no avail.

PRM Team decided to evacuate Kent to the acclimatization enclosure.

PRM Team decided to evacuate Kent to the acclimatization enclosure.

Just like Kent, Maduri was also suspected to have received injuries to her neck from a fight with another orangutan. Although her injuries were not as bad as Kent’s, the fight would likely have caused her significant stress, which influenced her eating patterns and left her unsure of her range.The fight could have been triggered by many things including a dispute over territory or food resources.

After the passing of Maduri, the team concentrated on Kent’s health. His wounds had significantly worsened and unfortunately the facility at camp is not adequate to support the type of intensive care he required, so for the first time in 28 months we made the decision to evacuate Kent and return him to Samboja Lestari on May 23, 2014.

6 2014.05

Our vet checked her condition and decided to evacuate Maduri to Camp 103.


Following the death of Maduri and then Kent’s evacuation to Samboja Lestari, we received another blow when the team found the remains of Wani in the Gunung Belah area on June 12, 2014. Large teeth marks indicated that Wani might have been attacked, or at least scavenged upon, by another large mammal. Clouded leopards (Neofelis diardi borneensis) occur in Kehje Sewen, although they are not known to generally attack lone adult female orangutans. However there are reports of clouded leopards attempting to take orangutan infants, for example in the Ketambe Forest in Aceh, seven rehabilitated juvenile orangutans died after attacks by clouded leopards (Rijksen, 1978). Possibly it is more than likely that Wani had died and her remains were scavenged by Bornean bearded pigs (Sus barbatus). There have been cases of this species killing (but did not prey on) several young rehabilitated orangutans in Gunung Beratus Conservation Forest, East Kalimantan, and also in Tanjung Puting National Park, Central Kalimantan.



Wani could have also have died from sickness and then nature does the rest. Likely we’ll never know. Only one fact remains, which is that Wani is very sadly no longer with us. In her efforts to adapt in her new home in Kehje Sewen, Wani showed remarkable improvement in her survival skills. She identified natural food and was feeding well, despite her reluctance to build arboreal nests. However in the last few weeks of her life, Wani had started to build her nests in the trees and we were very encouraged. The last PRM note on June 5 indicated that her behavior was improving with healthy feeding behavior and good quality nests. The team decided to leave Wani alone without our constant presence, which would have naturally changed her behavior, while the team focused on other orangutans. Sadly, we had to face her death a week later.

Wani showed remarkable improvement in her survival skills.

Wani showed remarkable improvement in her survival skills.

Working for the Best

Inevitably, the last two months have been tough for the BOS Foundation. The team is doing all they can to ensure the well-being of all of our orangutans through PRM activities but of course we cannot observe everything that happens in the wild. Orangutans often simply don’t want to be followed, which is something we expect and would be demonstrated in wild orangutans. After the death of Maduri and Wani, we are now hoping the best for Kent’s recovery. The latest report from Samboja Lestari confirmed that Kent underwent surgery on May 27 to suture his wounds and he is now receiving intensive care. He is now recovering thanks to the loving care and adequate medical facilities.

We continue to work intensively on Kent’s recovery.

We continue to work intensively on Kent’s recovery.

Maduri and Wani will always be in our hearts, and we continue to work intensively on Kent’s recovery and for the continuation of a successful reintroduction program. The teams at Samboja Lestari and in Kehje Sewen Forest have been amazing in ensuring the welfare of our orangutans! We can’t thank you enough. Last but not least we thank all of you for your ongoing support for the BOS Foundation as we work towards ensuring the long-term success of our programs.

Text: Nur Hariyanto, Syahik Nurbani, Monica Devi Krisnasari, Media R. Clemm, Paulina Wijanarko, Meirini Sucahyo, Fransiska Sulistyo, Agus Irwanto, Aldrianto Priadjati, Sri Suci Utami Atmoko, Jacqui Sunderland-Groves, Simon Husson

Photos: Agus Purniawan, Awal Choirianto, Syahik Nur Bani, Suwardy



Singleton, I., Wich, S.A., Stephens, S., Utami Atmoko, S.S., Leighton, M., Rosen, N., Traylor-Holzer, K., Lacy, R., and Byers, O (eds.). 2004: Orangutan Population and Habitat Viability Assessment: Final Report. IUCN/SSC Conservation Breeding Specialist Group, Apple Valley, MN.

Marshall, A.J., Lacy, R., Ancrenaz, M., Byers, O., Husson, S.J., Leighton, M., Meijaard, E., Rosen, N., Singleton, I., Stephens, S., Traylor-Holzer, K., Utami Atmoko, S.S., van Schaik, C.P., Wich, S.A. 2009. Orangutan population biology, life history, and conservation. In Serge A. Wich, S. Suci Utami Atmoko, Tatang Mitra Setia and Carel P. van Schaik, eds. Orangutans: Geographic Variation in Behavioral Ecology and Conservation, pp. 311-326. Oxford University Press, New York.

Russon, A.E. 2009. Orangutan rehabilitation and reintroduction: Success, failures, and role in conservation. In Serge A. Wich, S. Suci Utami Atmoko, Tatang Mitra Setia and Carel P. van Schaik, eds. Orangutans: Geographic Variation in Behavioral Ecology and Conservation, pp. 327-350. Oxford University Press, New York.





Updates from Kehje Sewen: The Friendship between Upi, Casey and Noel and the Search for Leo

Upi, Casey and Noel Meet Up

Upi has made a full recovery, regained her appetite and is spending most of her time once again foraging for food.

2014.06.29_9 IMG-20140629-WA0013_Upi_Kenang


More than half of her day is spent foraging and she is eating various forest fruits, lianas, shoots and Scleria (commonly known as nutrushes). She usually wakes up at around 7.30 in the morning, climbs out of her nest and begins her search for food. She has occasionally been seen to prefer to eat inside her nest and some mornings will reach out, grab a liana to eat and start munching away whilst still comfortably in her nest. Generally though she tends to roam far throughout the forest to find her preferred foods. At the end of a day spent foraging, Upi either returns to her old nest or build a new one nearby.

2014.06.29_2 IMG-20140629-WA0004_Upi_Kenang

Upi and Noel are having party.

Upi, Noel and Casey were recently observed together. They ate together, but avoided any physical contact amongst themselves. When it started raining Upi made a cover for her head, while Casey chose to build a nest and Noel sheltered under the leaves. Sitting in the rain is pretty miserable and during other observations Upi has been seen to idle the time away in her nest until the rain ceases and she can again commence her activities.

2014.06.27_10 IMG-20140627-WA0022_Casey

Casey, drinking water from the river.

The three of them ate well and played together and while Casey and Upi sometimes fight over food, it seems to be half-hearted. On the whole Upi and Casey’s relationship has improved tremendously after their initial conflict.

Leke was found by the team on a rainy day along phenology transect 1081. Upon noticing the team Leke approached them briefly before leaving to continue looking for food. She must have been hungry that day as she ate for two hours without a break!

2014.07.02_5 IMG-20140702-WA0005_Leke_Agus

The next day however, she behaved differently and tried to avoid the team. She kept moving from one tree to another and chose not to come down to the ground which is a good sign. Her appetite was as healthy as before though and she ate fruits, bark, Etlingera shoots (a herb from the ginger family), ficus leaves and termites.

2014.07.06_5 IMG-20140706-WA0053_Leke_Kenang


It was lovely to see Leke and Upi interacting as well; they were observed eating together very harmoniously.

Looking for Leo

Leo was too fast for the team to observe and it took them a while to finally catch up with him along the phenology transects. He was absorbed eating figs and though he seemed to notice the observers around, he chose to continue eating after just a glance. Not that far away the team also spotted Jumiten and Mona having fun in each other’s company and it was great to see them interact so well together.

The next day, the team detected both Leo’s and Mail’s signals along phenology transect Lembu River 1000. Unfortunately, inspite of a long pursuit neither of them could be tracked and observed.

2014.06.05_12 IMG-20140605-WA0014 Mona_Fajar


Juminten and Mona’s signals meanwhile, showed that they were still around and together and the team decided not to observe them as daylight was fading and it was time to call it a day.

The team is already planning an overnight stay in the Lembu phenology area to search for Leo and we are sure that we will be able to find him soon!

Look forward to our next update!

Text by: Bani, PRM Technician.

Quick Updates from Kehje Sewen!


The team has been busy in the forest as always, following the daily lives of our orangutans.  During five days of nest-to-nest monitoring on Casey, the Post Release Monitoring Team recorded Casey eating a good, varied diet including many different food items; fruit, leaves, young shoots and termites. During monitoring she usually woke up at around 6 am, climbed out of her nest, descended the tree and onto the ground to look for food. Orangutans are generally supposed to forage arboreally rather than terrestrially, but Casey still often searches for food on the ground. That said, she also travels and nests in the trees and the team reported that her nest making skills have continued to improve. Having been up and about for 12 hours, Casey normally settled down in her new nest for the night at around 6 pm. 2014.06.12_19 IMG-20140612-WA0032 Casey_Masino Released in April 2012, Casey has now lived in the forest for over 2 years. She has adapted well despite the disability inflicted on her hand before she first came into our care. We are so thrilled that Casey is thriving in Kehje Sewen. 2014.06.15_1 IMG-20140615-WA0012_Casey_Kenang UPI

Upi was only released recently and two weeks ago we received concerning news from the field that she seemed lethargic, had lost weight and was eating a lot less than normal. In response to the change in Upi’s behavior the Team focused on intensively monitoring her through nest-to-nest follows and data collection for 14 days straight. 2014.06.16_8 IMG-20140616-WA0010_Upi_Guswan During the following days she regained her appetite and strength. She started eating more natural foods such as lianas, rattan shoots, termites, and figs. The Team could visually see her grow stronger and gain weight. Maybe she had eaten something that didn’t agree with her, as we have seen happen in other rehabilitated orangutans we have reintroduced or she was still struggling to find a range suitable for her. Whatever the reason, she seems to have overcome this and has improved daily. Upi was active and often moved between the trees though she, like some of our other orangutans, still also travels on the ground. Sometimes when the Team were close by, she would climb down and try to follow the observers. Having been fed and cared for by humans for many years before her reintroduction, she still likes human company. This is something we will have to overcome with Upi. 2014.06.19_5 IMG-20140619-WA0010 Upi_Awal On one occasion Upi was seen with Agus. Agus tried to approach her and copulate, but she refused his attempts. Soon after, Agus gave up and left her alone.


The Team found Agus along phenology trail 1000. As always, he doesn’t like seeing the Team and he threw branches and kiss-squeaked at them. Based on their observations, the Team reported that Agus was eating well and overall looked very healthy and well. Good job guys and we look forward to posting more news on our orangutans. 2014.06.13_6 IMG-20140613-WA0005 Agus_Masino

2014.06.17_7 -WA0007 Agus_Awal  

Text by: Bani, PRM Technician.