Borneo – Cheeky Monkeys

Pig-tailed macaque (Macaca nemestrina) picking figs (Photo by Jan Young)

Dear Readers, macaques might not be the rarest of the primates in Borneo, but they are fascinating animals to watch. There are two species: the pig-tailed macaque, which is pretty much ubiquitous across southern Asia, and the long-tailed macaque (Macaca fascicularis) (also known as the crab-eating macaque) which is equally wide-spread. Both species have a troubled relationship with humans: as their forest homes are destroyed they venture into towns and cities and, with their intelligence and highly-evolved social structures, can wreak havoc on households, agricultural land and food markets. We have retaliated by culling them, and by using them as experimental animals: indeed, the population increase in Malaysia happened after a ban on exporting the macaques for drug and cosmetic research in 1982 (previously 10,000 animals were sent into captivity every year). One could argue that if we hadn’t cut down their homes they wouldn’t be being a nuisance in ours of course.

Long-tailed macaques (Photo by John Tomsett)

I loved watching the macaques: their lives are so complex, their interactions mirror ours, and they are so agile. Plus, generally, they seemed completely indifferent to our presence, and had no desire whatsoever to interact, apart from an alpha male occasionally blinking at us or bearing his teeth half-heartedly if our boat drifted too close (we would immediately withdraw). Macaques have a very complicated dominance hierarchy: the males protect ‘their’ females but the females determine pretty much everything else, from where to feed to how long to linger. The youngsters are just youngsters, playing, running, getting into scrapes and generally being a nuisance. Anyone locked down with small children can relate, I’m sure.

Photo by John Tomsett

Mother macaque with baby

We were stunned into silence by the appearance of the young macaque pictured below, however. It took us a second or so to realise that he had lost both his hand and his foot on the right hand side. Was this from a close encounter with a crocodile or other predator? Was he injured by another macaque? Was this even the result of a snare? We will never know but what was remarkable was that the wounds seemed to have healed, the monkey seemed alert, and that s/he was hopping along with the rest of his troop without obvious distress. Of course, s/he will always be more vulnerable to predators than her companions, but she will also benefit from their group cohesion when it comes to finding food and identifying predators. A lot of good things accrue from being part of a community, as many of us are finding during the current crisis.

Macaques are interwoven into the ecology of the rainforests in which they live in many different ways. Other mammals such as bearded pigs and mouse deer will follow the sounds of macaques as they search for food, and may be able to identify the different calls that the monkeys make when they find a fruiting tree. Indigenous hunters of the Penan people have learned to copy these calls to lure pigs, and apparently the contented ‘mmm’ of a macaque feeding on fruit is enough to bring the unsuspecting prey within reach of a spear. Macaques also store fruit in their cheek pouches to eat later, and will spit out the seeds a good way away from the parent plant, hence helping with dispersal. Macaques have also taken to hunting the rats that live in the oil-palm plantations, and, being creatures of broad taste, will also eat the oil palms themselves. In the mangroves the long-tailed macaques will find and eat crabs and shellfish. Macaques will eat the fruit of up to 90% of the trees in the forest, and seem to be immune to some of the defences of the plants – they can tolerate some the highly-corrosive sap of some members of the mango family, for example. However, they cannot survive ingestion of the calcium oxalate crystals, or rhapides, produced by some palms and other plants (I talked about them in my post on Virginia creeper).


We had the good fortune to catch up with some macaques again at the Mud Volcano in Tabin – an area of salt-rich minerals which are visited by many animals. On the morning that we visited, the macaques were dominating the area – an unfortunate bearded pig who popped in for a chance to get some mud therapy took one look at all the monkeys and ran off. Very sensible too. These guys might argue amongst themselves, but they are a formidable force when they band together.

Pig-tailed macaques at the mud volcano. Notice the alpha male keeping watch.

Macaque drinking the therapeutic muddy waters

Young macaque considering his options

We witnessed some very interesting behaviour while we were at the mud volcano, including a female who, while happy to mate with one male, saw another off most determinedly when he attempted to get friendly. Macaques have been the centre of many long-term studies of primate behaviour and I have no doubt that once individuals were identified, it would become as fascinating as any soap opera, though trudging through the hot, humid rainforest while being pestered by a wide range of bitey little critters would dampen the enthusiasm of all but the most determined scientists. Secretly, though, I envy those who’ve had the chance to do such things: my short stints of observing primates have filled me with an urge to understand more about our cousins, who are so like us in some ways and so completely different in others. Long may they play, unhindered, in the forests of Asia.





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