From the Forest: The Kutai Orangutan Project

morio subadult male

From the Forest is a new feature on the Orangutan Conservancy website written by those on the front lines of orangutan conservation and research. This inaugural column is written by Dr. Anne Russon of the Kutai Orangutan Project. Kutai is one of the research projects that OC helps to support.

From the Forest: The Kutai Orangutan Project
by Anne Russon

Project Background

The Kutai Orangutan project was established in 2009, with Kutai National Park (“KNP”) authorities, to improve the knowledge and protection of its orangutans. Effective protection requires understanding their habits and needs. These orangutans are not currently well known, appreciated, or protected. This project was therefore designed around a long-term study of their behavior and habitat usage.

KNP orangutans belong to the E Kalimantan population of the easternmost Bornean subspecies, P. p. morio. Bornean orangutans are now classified as three subspecies—morio (east: Sabah, E Kalimantan), wurmbii (central-west) and pygmaeus (northwest). Compared to other orangutan habitat, E Borneo is the least productive and suffers the most severe irregular droughts, so morio faces the poorest diets and the longest, harshest food lows. Morio differ from orangutans elsewhere, physically and behaviorally. They are often “black” rather than red like Sumatrans or other Bornean orangutans. They may also be the toughest, specially adapted to E Borneo’s harsh habitat. They appear to rest a lot, and travel and socialize little, perhaps because their poor diet means they must economize on energy spending. They are important scientifically for surviving at the worst margin of the orangutans’ geographic range. Conservation-wise, their special ecology and adaptations need to be taken into account.

Morio in E Kalimantan (“EK”) probably differ from morio in Sabah. They are geographically isolated and evidence for genetic differences is accumulating, so morio EK may have adapted independently and differently. They are also governed separately (Indonesia vs. Malaysia). Morio EK should probably be managed as a separate taxonomic and conservation unit. In this light, morio EK is highly vulnerable to extinction. Its most recent official population estimate is 5,250. This makes it more fragile than the Sumatran orangutan, which the IUCN classifies as critically endangered at a population estimated at 6,500. Morio EK is even more vulnerable than these numbers suggest because its population is highly fragmented, its habitat the continuing target of extensive human development.

Unfortunately, little is known about morio EK behavior today although they were the first wild orangutans studied in Indonesia. Rodman, from May 1970, and his successors (Mitani, Leighton, Suzuki) contributed greatly to early understanding of orangutans through their studies of morio in KNP into the early 1980s, but little has been done since. Lack of interest is the reason, and it probably owes to the common belief that KNP and its orangutans are write offs. KNP and its orangutans have suffered major damage, ranging from poaching, encroachment, and surrounding commercial development to massive forest fires in 1982-3 and 1997-8. The threats persist because KNP protects a large expanse of coastal lowland rich in valuable resources, coal and agricultural land. KNP was recognized as one of the few remaining protected strongholds of morio EK; its orangutan population identified as a priority population for conservation in 2004 at an estimated size at 600. News reports in 2009 emphasized continuing uncontrolled human intrusions. Pessimists claimed the park’s remaining orangutan population had already been virtually eradicated—with only 30-60 individuals surviving.

Reports of their demise are, fortunately, greatly exaggerated.

KNP officials report ca 580 km2 of KNP habitat is relatively intact and ca 600 km2 of its burned forest has been recovering as secondary forest for the last 12 years. Studies are finding high conservation value in recovering Bornean forests elsewhere; with time, they regain much of their biodiversity and carbon storing capacity—so signs for KNP are good. In 2010, systematic surveys in KNP’s eastern sector also found good evidence that the park’s orangutan population now numbers 1,000-2,000.

The upshot is that morio-EK should be a high priority for research and conservation, especially in KNP. On both research and conservation fronts, our understanding of morio-EK needs updating because of changes to their habitat. In the face of prevailing beliefs that KNP and its orangutan population are irreparably damaged and active efforts to re-allocate some of KNP to commercial development, current assessments of the conservation value of KNP and its orangutan population are urgently needed to establish the merits of protecting both. Science can contribute to all these goals.

Project overview

I chose ranging as the project focus because travel patterns offer a good overview of orangutans’ habitat needs and usage, social structure, and cognition (i.e., how they learn and use their environment effectively and efficiently). Aims include using research to serve conservation through regular monitoring, increasing the conservation value of these orangutans and KNP, and enabling more effective conservation programs by improving our knowledge.

habitat along the Sangata River

We started searching for a new site in the summer of 2009. With KNP field staff, we surveyed several areas of the park for orangutan presence and vulnerability to poaching and other illegal activities. On this basis, we chose an area extending ca 8 km along the Sangata River, KNP’s north border, and 1-2 km inland. It overlaps Mentoko, the earliest morio field site in Indonesia. Habitat-wise, it is recovering from extensive fire damage in 1982-3 and 1997-8. It now offers a mix of primary and secondary forest and grades from flooding riverine to stream-fed valleys and slopes, and hill dipterocarp forest. This area needs protection. The Sangata River, only ca 30 m wide, is its only barrier¬ and it is easily crossed. We can (and have) waded across in the dry season. A public road also runs 30-50 m from the river’s edge, increasing this area’s vulnerability to incursions. Damage that we find shows that this area has been and still is subject to poaching.


We began work at this site in November 2009. Early work involved setting up a basic field camp, cutting trails to allow us to explore the forest, setting up vegetation plots to allow us to monitor seasonal fluctuations in orangutan food availability, and searching for orangutans. We followed our first orangutans early in January 2010, although they lost us within a half day.

After working at this site for 20 months, we have a post, a trained field team including five local field assistants, a manager, and camp cook, 4 vegetation plots, 2 fruit trails, boat, and motorcycle. We have encountered at least 34 orangutans in our study area (6 adult females with offspring, 1 female and 4 male adolescents, 5 flanged and 13 unflanged adult males). All appear to be healthy and reproducing in normal fashion. We have followed 29 of them for a total of approximately 2,000 hours of observation. Most of the orangutans are still only semi-habituated at best. Several threaten us repeatedly, and most find ways to lose our trackers within 3-4 days.

What we can say to date is that the orangutan community in our area is strong. Based on the independent orangutans that range repeatedly in our area (7 females, 6 males), we estimate a density of 3-4/km2; this is very close to densities estimated in the 70s-80s. These orangutans and their habitat seem to be recovering well from severe damage.

By all accounts, morio is the most energy stressed of all orangutans because of the very poor and unreliable food productivity of its E Bornean habitat. Energy spending efficiencies should then be very important to morio in KNP, to offset the low energy intake. We see several patterns that might serve to reduce energy expenditures. Our orangutans re-use old nests relatively often (ca 18% night nests), about the same rate as morio in Sabah. Nest re-use does not seem necessary in our area (many nest sites are available), so it could represent energy savings. Our orangutans also nest often in the last tree in which they fed for the day—a rare pattern elsewhere. This saves the cost of travelling elsewhere to nest and ensures first access to the fruit the next day. Finally, we find food remains which show that orangutans are travelling and feeding on the ground in all areas and in all seasons. This could reduce energy expenditures (removing the costs of vertical climbing in arboreal travel) and increase energy input (they eat gingers, other terrestrial herbs, and bark from tree buttresses and roots). None of these generate large energy savings, but if E Bornean habitat is as poor as believed, then generalized penny-pinching may be the main possibility.

We have been surprised to find that our orangutans travel farther than reported in other morio studies. Travel is one of if not the most costly activities, so morio is expected to limit travel. Published findings show independent morio females travel, on average, under 300 m daily; our preliminary results suggest 350-500 m daily. The probable explanation is the varied habitat in our study area. Orangutan resources are not spread evenly throughout our study area, so orangutans may have to travel relatively long distances to satisfy their food needs.

Beyond the findings, the work we do has conservation benefits. Our regular orangutan field work effectively monitors the study area, one result of which has been detecting illegal activities in KNP. This has enabled KNP authorities to catch intruders and stop problems.

Also in the course of studying orangutans, we have identified 32 other mammal, 94 bird, and 261 tree species. They include 3 more endangered primates (Presbytis hosei cannicus, Hylobates muelleri fumereus, Nasalis larvatus), 10 threatened birds, and 24 tree species endemic to Borneo. Presbytis hosei cannicus was believed eradicated from KNP. These observations help build a good case for the park’s biodiversity value. We are also seeing interest develop in our site. In 2011, we hosted five professional visits, three MA thesis studies, and field internships for local university students. All help boost the importance of the park.

In summary, our early findings show that KNP and its orangutans are recovering well from the severe damage they have suffered, in at least some areas. They also suggest morio patterns different than those published. If they hold up, they should enhance understanding of orangutans in KNP and as a whole, and contribute to effective conservation strategies.

Dr. Anne Russon/ OC edit by Tom Mills

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Last year, The Orangutan Conservancy provided funding for Sintang Orangutan Center (SOC) to purchase an X-ray machine for their clinic and rehabilitation center in West Kalimantan.
Last year, The Orangutan Conservancy provided funding for Sintang Orangutan Center (SOC) to purchase an X-ray machine for their clinic and rehabilitation center in West Kalimantan.

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