OKP Update 2016

Orangutan Kutai Project, Kutai NP, E. Kalimantan Update 2016

by Anne Russon

We are now in our sixth year of orangutan research and conservation work in Kutai National Park (KNP), East Kalimantan Indonesia. KNP is home to the only remaining large wild population of E Bornean orangutans in Indonesia, but it has been seriously threatened by human “development” for decades in the form of settlements, mines, plantations, and two massive forest fires. Only last year, 60,000 ha of KNP’s 190,000 ha were excised to legalize illegal settlements inside its boundaries.

The research site we established in 2010 is along the Sangatta River, the park’s nothern boundary. It overlaps Mentoko, the site of Rodman’s orangutan research in 1970-71 – the first wild orangutan research in Indonesia – so it offers an exceptional opportunity to compare KNP orangutans’ behavior now, when this forest is recovering from serious damage, and 1970-71, when it was near pristine.

To assess how well KNP’s orangutans are coping, our studies have focused on basic functional behavior (feeding, diet, travel, activity budgets) and feeding ecology (plant food species and their distribution, seasonality).

Findings to date

Mentoko area forest represents habitat recovering from damage. Recovering damaged habitat is important to conservation in supporting wildlife, since little pristine habitat remains. To assess how well Mentoko area orangutans are faring in recovering habitat, we compared our findings for 2010-12 (12-15 yrs natural regeneration from 1997-98 severe drought/fire damage) with those for near-pristine conditions (1970s) and 0-4 years regeneration from 1982-83 severe drought/fire damage (1983-87). Mentoko area forest was in better condition in 2010-12 than 1983-87, but different from near-pristine. Resident orangutans’ activity patterns had recovered to near-pristine values, after diverging from them early after damage. E Bornean orangutans have been recognized for their great resilience and exceptional diet flexibility is probably an important contributor; it was probably a key contributor to their surviving these disastrous droughts and fires.

A second research theme has been identifying Mentoko orangutans’ travel routes, as a first step in understanding what they know about where resources are located, when they are are available, and how to navigate to them.

Our third major theme, and a very unexpected one, has been the gradual disappearance of orangutans from our study area. They were abundant and very easy to find and follow in 2010, but almost totally absent in 2014 and later. In hindsight, our records suggest a gradual year-to-year decrease from 2010 to 2016. The explanation does not appear to be poaching. We monitor regularly, and the little poaching we have found in our area is, if anything, deceasing. We doubt that these orangutans have died because all the adults we have followed would have survived the 1997-98 droughts and fires – conditions much worse that those they face now. We think the likely explanation is the ENSO (El Niño Southern Oscillation) cycle. 2010-11 was a La Niña year and 2015-16 a very strong El Niño year, which brought very heavy rains and prolonged severe drought to our research area; over the intervening years, rainfall gradually decreased. A possible result is gradually decreasing plant food production, so our area has gradually become less attractive to orangutans. Orangutans’ disappearance was a major reason for our starting research work at a second site: it allows easier access to areas where ‘our’ orangutans may have moved, and other orangutans range there that are easy to find a follow.


Our aims have always included contributing to orangutan conservation. On a day to day basis, since starting research in KNP, we have monitored our research area and reported any evidence of illegal activities to the KNP authorities. On numerous occasions, this has resulted in catching poachers and stopping illegal activities ranging from logging to illegal planting and poaching. The number of illegal activities we detect has decreased over time, so there is some indication that our monitoring has been of some value.

Third, in collaboration with the KNP office and Indianapolis Zoo, we have planned a forest enrichment project designed to improve food availability for orangutans on a burned-over hill forest in the Mentoko area.

What next.

In line with our disappearing orangutans, upcoming activities are oriented to finding evidence to explain why they disappeared and where they go. To that end, we have begun.

Quarterly nest censuses along 6 trails within our original study area. Orangutan nests typically remain visible for several months, so regularly repeated nest censuses can help us detect when orangutans are or were present in the area censused.

Analyzing our orangutan travel data for speed and travel direction near the end of the day may provide a means of extending our estimates of areas that orangutans reach when move to areas beyond our Mentoko study area that we have difficulty accessing.

Continuing our observations of orangutan behavior around Camp Kakap should enhance of our understanding of KNP orangutans’ movements and other behavior. During the 2015-16 El Niño drought, three orangutans were sighted in the Kakap area that may be orangutans we know from our original research area. This suggests that KNP orangutans can travel up to 5-6 km from the area where we normally found them. It would contribute to determining where orangutans from the Mentoko area disappear; it also suggests that these orangutans travel much farther than other studies have suggest.

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