18-5-2023 SEPILOK, BORNEO - SOUTHERN PIG TAILED MACAQUE (Macaca nemestrina) (FEMALE) (COURTESY OF MRS VALERIE FISHER)

The southern pig-tailed macaque (Macaca nemestrina), also known as the Sundaland pig-tailed macaque and Sunda pig-tailed macaque, is a medium-sized macaque that lives in southern Thailand, Malaysia, and Indonesia. It is known locally as berok.

M. nemestrina is mainly terrestrial, but also a skilled climber. Unlike almost all primates, these macaques love water. They live in large groups that split into smaller groups during daytime when they are foraging. They are omnivorous, feeding mainly on fruits, seeds, berries, cereals, fungi, and invertebrates. A study in peninsular Malaysia found them to be the primary, and perhaps the only, seed dispersers of the rattan species Daemonorops calicarpa and Calamus castaneus.

There is a hierarchy among males, based on strength, and among females, based on heredity. Thus, the daughter of the alpha female will immediately be placed above all other females in the group. The alpha female leads the group, while the male role is more to manage conflict within the group and to defend it.

Female gestation lasts around 5.7 months. She will give birth to one infant every two years. Weaning occurs at 4–5 months. Sexual maturity is reached at 3–5 years.

In Thailand, they have been trained for 400 years to harvest coconuts.

This macaque is mostly found in rainforest up to 2,000 metres (6,600 ft), but will also enter plantations and gardens.

It is found in the southern half of the Malay Peninsula (only just extending into southernmost Thailand), Borneo, Sumatra and Bangka Island. There are reports of the species having been present in Singapore before 1950, but these were likely escaped pets. The only pig-tailed macaques in Singapore today are introduced monkeys.