Pig-tailed Macaques of Thailand
A northern pig-tailed macaque, Macaca leonina, thoughtfully inspects the back of its hand while grooming its fur.
A northern pig-tailed macaque thoughtfully inspects the back of its hand while grooming its fur.

Caught in shafts of light on the edge of the forest, a pig-tailed macaque is wholly absorbed as it inspects the fur on the back of its hand. The behaviour and pose are strikingly human, and reminded me of how much we have in common with our primate cousins.

This is an adult male northern pig-tailed macaque. Until quite recently pig-tailed macaques were considered one species, Macaca nemestrina, with the northern pig-tailed classed as a sub-species. However studies conducted in the early 2000s (e.g. Gippoliti, 2001) looking more closely at anatomical and behavioural differences, determined that the differences were so significant that they should be considered two distinct species. The southern pig-tailed macaque retained the original scientific name (M. nemestrina) while the northern pig-tailed macaque (previously the sub-species M. nemestrina leonina) was elevated to full species level and given the new scientific name Macaca leonina. However this change remained scientifically controversial until quite recently, and only in the past few years has it become fully accepted. The most recent (at time of writing) research on speciation of pig-tailed macaques in South East Asia, using analysis of differences in mitochondrial DNA proteins to determine molecular clock timelines, suggests that northern pig-tailed macaques separated from their southern brethren around 1.7 million years ago, and from the Siberut macaque of Western Indonesia only just over one million years ago (Abdul-Latiff and Md-Zain, 2021). Both northern and southern pig-tailed macaques occur in Thailand, with the boundary between ranges of the two species believed to lie in the Krabi region of Southern Thailand. I photographed this guy on the island of Phuket, which is very close to this boundary. The lighter colour fur, white flashes above the eyes and a thin red line running from the corner of the eye towards the ear, mark him out as distinctly a northern pig-tailed.

A northern pig-tailed macaque (Macaca leonina) looks straight ahead as it emerges from the shadows of the forest.
A northern pig-tailed macaque caught in sunlight with background in deep shadow. It can clearly be identified as a northern pig-tailed by the conspicuous white flashes above its eyes and the deep red lines running from the corner of each eye towards the ears. Phuket, Thailand.

Pig-tailed macaques are denizens of lowland and hill rainforest through much of South-East Asia. However in many locations their natural habitat is disappearing rapidly as rainforest are cleared to make way for palm oil and rubber plantations, rice paddy fields and urban development. Because of this northern pig-tailed macaques are classed as a vulnerable species by the IUCN. They are primarily fruit eating, but will also take leaves, birds eggs, insects and caterpillars, and are not averse to raiding palm oil and fruit tree plantations. Along with their relatives the crab-eating macaques (Macaca fascicularis) pig-tailed macaques have learned to live alongside humans. In Phuket the inhabit the forests and mangroves (in the case of crab-eating macaques) fringing towns and villages, especially along the eastern shores, and will often congregate in tourist areas drawn to handouts of bananas. The habituation to humans brings numerous problems. The monkeys develop a taste for the easy pickings of tourist handouts and the risks of infection and injury due to bites or scratches from fearless monkeys is significant. But for me it is the similarities between us that are the most fascinating; the strong social bonding, the way a youngster will play with a leaf or a discarded plastic drink bottle just like a small child, or the way an adult will stare at the back of his hand as if in deep introspection, and for all we know maybe he is.


Gippoliti S. 2001. on the taxonomy of Macaca nemestrina
leonina Blyth, 1863 (Primates: Cercopithecidae). Hystrix It J Mamm 12: 51–54. doi:10.4404/hystrix-12.1-4171.

Muhammad Abu Bakar Abdul-Latiff, Badrul Munir Md-Zain. 2021. Taxonomy, Evolutionary and Dispersal Events of Pig-Tailed Macaque, Macaca nemestrina (Linnaeus, 1766) in Southeast Asia with Description of a New Subspecies, Macaca nemestrina perakensis in Malaysia. Zool Stud. 2021; 60: e50. Published online 2021 Oct 8. doi: 10.6620/ZS.2021.60-50PMCID: PMC8685347

About these images

I took these shots late afternoon, on the edge of some forest on the eastern side of Phuket Island, Southern Thailand. The macaque had just climbed down from a tree and was perfectly lit by the low-angled sun, while the forest behind was in deep shade. The images were taken with a Nikon full-frame DSLR; the full size image is around 80 megapixels.

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