HSV Lecture 2015 – Studying primates before they all go: The orang-utans of Kalimantan

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Studying primates before they all go: The orang-utans of Kalimantan

HSV Public Lecture by Robert Bender, environmentalist and HSV member, at Balwyn Library on 25 June 2015


Robert’s lecture was based on his experiences of an Earthwatch Institute expedition he undertook in 1986. Earthwatch Institute expeditions enable interested amateurs to pay their own way and join a research project as extra ‘hands’.

He began by explaining that on current scientific information the orang-utan lineage diverged from other apes, i.e. gorillas, chimpanzees and humans, about 12–16 million years ago. Around 400,000 years ago orang-utans branched into two species, Pongo abelli, now found in Sumatra, and Pongo pygmaeus, found in Borneo.

Research into primate behaviour has been a post WWII development, with Louis Leakey encouraging some of his students to do environmental in-the-field studies. Three key ape researchers, all Leakey’s students, were Dian Fossey (born 1932), gorilla researcher who was murdered at age 53, Jane Goodall (born 1934), chimpanzee researcher, and Birute Galdikas (born 1946), orang-utan researcher in Borneo.


The name orang-utan comes from the Malay and Indonesian words meaning ‘person of the forest’.

Nowadays the two species of orang-utans survive in Borneo and in NW Sumatra. Historically the orang-utan range extended well into SE Asia but, due to human expansion, forest clearing and illegal logging, their range and numbers have been greatly reduced.

Birute Galdikas arrived in Tanjung Puting Reserve, Kalimantan, Indonesian Borneo, in 1970 with her photographer husband Rod Brindamour, to conduct field research for a PhD.

A major aspect of her field work consists of following orang-utans from dawn to dusk, naming each one and mapping their individual ranges. Shortly after arriving in Kalimantan Birute found it necessary to set up an orphanage for rescued orang-utan infants.

The pattern of orang-utan behaviour is that they are active from sunrise around 6 am to sundown 6 pm. In order to observe the orang-utans the Earthwatch group and other trainee local rangers needed to do a two-hour walk, which required leaving the camp at 4.30 am, a long day of field observations and return to the camp around 8 pm. With added evening lectures this made for a very long day, so volunteers tended to go out observing only every second day.

Orang-utans are primarily herbivorous except for eating termites, a rich source of valuable protein. Young orang-utans stay with their mother for up to six years, learning the requirements for survival. Otherwise they are solitary animals due to scarcity of food. Males are distinctly bigger at around 100 kg, compared to 50 kg for females. With this degree of sexual dimorphism, one male typically dominates a harem of females. This gives rise to many non-breeding males.

The orang-utans play an important role in the forest, dispersing the seeds from the fruit trees on which they forage. Typically the fruit ripens a few at a time, so the orang-utans needs to forage each tree on a regular basis as they seek out the ripe fruit. This is something the young are taught by their mothers.

Orang-utan numbers are falling primarily due to loss of habitat. Birute estimates when she arrived in 1970 there were about 160,000 orang-utans in Borneo, however by 1986 there were only about 60,000.

Since establishing her primary home in Tanjung Puting Reserve, Birute has married a local Dayak rice farmer and village elder Pak Bohap. They have two children.

Robert’s talk was illustrated with slides showing the Earthwatch group he travelled with (ten women and three men) and the ex-captive orang-utans (those, being too numerous to be supported by the sparse local food supply, that turned up in the camp area for a daily feed of pineapple).

Some of the orang-utans had been taught sign language which they were still able to use when requesting food. Sub-adults who hung around the camp site could be mischievous, stealing shampoo and toothpaste when the Earthwatchers were visiting the bathing site.

Two of the Earthwatch group Robert travelled with were trained nurses who volunteered to help in the nursery where ex-captive infants typically arrived with respiratory infections.

[When the advertised speaker was unable to come due to ill health, we were all most grateful that Robert Bender had conveniently brought along a USB stick with digital presentation of a talk he had given earlier in 2015 to another group.]

Report by Rosslyn Ives