The Borneo Rainforest- what comes to mind? A rich, tropical habitat, an endangered landscape overrun by Oil Palm and a long-limbed great ape - the Bornean Orang-utan.
We are all familiar with the orang-utan and its plight, and it is well known for the characteristics it shares with us: tool use, high intelligence and strong emotional bonds between mother and young.
However, the fascinating primate life of Borneo does not end with the orang-utan’s intelligence. In this article WLT describes some of the little known facts about the other ten primate species of Kinabatangan.
Müller's Bornean Gibbon (Hylobates muelleri) Endangered
Early in the morning, the jungle fills with a soulful crescendo of Bornean Gibbon song, duets of whooping cries that travel through the forest, echoing in the humid air. Singing is very rare in mammals, and the added complexity of duets between mated pairs adds to this remarkable behaviour.
Gibbons are also generally monogamous, which is highly unusual in both mammals and primates, only occurring in 3 per cent of mammalian species.
Proboscis Monkey (Nasalis larvatus) Endangered
Possibly one of the most bizarre looking creatures on our planet, and in part due to its caricature-like resemblance to ourselves, the Proboscis Monkey is one of Kinabatangan’s most charismatic inhabitants.
However, whereas the male’s huge pendulous nose and pot belly are well known, one rather unknown fact about this ungainly primate is its skill in swimming. Although they are mostly arboreal, they have the most aquatic lifestyle amongst primates, and even have partially webbed feet.
Silvered Langur (Presbytis cristata) Near threatened
Adult Silvered Langurs, or Leaf Monkeys, are handsome monkeys with ash-coloured fur with striking gold-orange young.
There are several theories as to why they have such eye-catching colouration, which disappears as they age. One of the theories is that it was caused by the rarity of colour vision amongst mammals. Primates have colour vision, unlike many mammalian predators, so the bright colour may make the babies easy to spot for the troop, but not for predators.
Hose’s Langur (Presbytis hosei) Vulnerable
The Hose’s Langur can only be found on the island of Borneo, where it has four distinct subspecies. One of these subspecies, Miller's Grizzled Langur (Presbytis hosei canicrus), can only be found in East Kalimantan and its history gives a frightening insight into the precarious future of primates on the island. The Miller's Grizzled Langur was thought to have gone extinct after sightings stopped after their habitat was subjected to several fires, human encroachment and continued forest degradation, but a population was ‘rediscovered’ in 2012.
There have been no confirmed sightings of Hose's Langur in Kinabatangan for a long time, so it may be locally extinct.
Red Leaf Langur (Presbytis rubicunda) Least concern
Red Leaf Langurs have been observed engaging in a peculiar behaviour: gathered around a termite mound, breaking off clumps of clay and eating the soil underneath.
Termite activity gives the mounds a different soil chemistry from the surrounding areas, and it is possible that the soil is used for supplementary minerals. However, the most popular theory is that it counters acid build-up in the forestomach and absorbs toxins that have been ingested.
Long tailed Macaque (Macaca fascicularis) Least concern
Long-tailed Macaques can be found in large social groups where tensions between individuals can erupt in fights and reconciled with bonding behaviours such as grooming.
Studies have shown a parallel between macaque behaviour after a fight and that of friends and partners arguing in human society. Both the victim and the aggressor macaques involved in a fight would show much higher levels of stress afterwards, which would continue until they had reconciled.
Pig-tailed Macaque (Macaca nemestrina) Vulnerable
The Pig-tailed Macaque have ‘harem-type’ social groups. Unlike the males, females remain with their birth troop when they reach sexual maturity and become part of a hierarchal system. When resources are limited, these hierarchies have an interesting role to play in the sex bias of young macaques; high ranking females have more daughters than sons and the young of low ranking females are more male-biased.
Sunda Slow Loris (Nycticebus coucang) Vulnerable
The huge eyes and puffed fur of the Sunda Slow Loris have made it a popular target for the pet trade.
However, despite its cute appearance, the Sunda Slow Loris is one of a very small group of mammals which have developed defensive chemicals which it can inject with a sting. It has an elbow gland which secretes a chemical that is used for communication with other individuals and to ward off predators such as pythons and eagles.
Western Tarsier (Tarsius bancanus) Vulnerable
The Western Tarsier is nocturnal and has large, round eyes like the Sunda Slow Loris, but unlike its ‘slow’ cousin, it is incredibly agile. It is able to leap horizontal distances up to 45 times its body length (almost six metres), and often catches its prey by leaping.
Human (Homo sapiens) Least concern
The primate species with the biggest impact ecologically on this area is undoubtedly humans. The community who have lived on this land for the longest, the Orang Sungai, have had a relatively small impact, historically dependent on the river for fish, prawns and various forest products.
This community have also become involved with the Model Ecologically Sustainable Community Tourism Project (MESCOT) in the area. MESCOT has developed various homestay programmes as well as jobs for local people operating tourist boats, guiding, souvenir making and performing. The conservation movement in this area has also provided local jobs (read our recent guest blog by ranger Berjaya Elahan about conducting wildlife surveys in the area, here).
More information
Forest fragmentation resulting from the development of the Oil Palm industry is the biggest threat to the rainforest habitat and each of the ten species of wild primates we have described above. By supporting the Saving Kinabatangan appeal, you will help us purchase and protect a vital piece of habitat with our partner Hutan, which is essential for future survival of Kinabatangan’s primates in the wild.