Macaques have a body length of 38-55 cm with comparably short arms and legs. The tail is longer than the body, typically 40-65 cm. Males are considerably larger than females, weighing 5-9 kilograms compared to the 3-6 kg of female individuals. The fur coat is grey to brown in colour being black or darker around the face. The Crab-eating Macaque is native to Southeast Asia. The macaque group of primates are the most widespread, second only to humans. The native range of this species includes most of mainland Southeast Asia.
A single infant weighing around 350 grams is born after a gestation period of 167-193 days. Infants are born with black fur which will begin to turn to a yellow-green, grey-green, or reddish-brown shade, after about three months of age. This natal coat may indicate to other group members the status of the infants so they are treated with care and protected.
Being “ecologically diverse”, the Crab-eating Macaque is found in a wide variety of habitats, including rainforests, riverine and coastal forests of nipa palm and mangrove. They easily adjust to human settlements and are considered sacred at some Hindu temples and on some small islands, while a pest when around farms and villages. Macaques are very social animals that live in groups of 5 to 60+ animals. These groups are multi-male groups, normally containing 2-5 males and 2-3 times as many females with their immature offspring. Their group size often depends on the level of predation and availability of food. Groups are female-centred, as the females are philopatric (i.e. remain in one place across generations) and the males move in and out of these groups. Males generally first emigrate from their natal group at the age of 4-6. They will remain in a group up to 4 or 5 years and thus will emigrate several times throughout their life. These monkeys are highly despotic and have a strict dominance hierarchy. Adult males rank higher than females. Female ranks are more stable than males, as males from time-to-time will be defeated and lose rank.
Although this species is often referred to as the Crab-eating Macaque, this name is something of a misnomer since other food items are far more common, with fruits and seeds making up 60-90% of the dietary intake. They prey on vertebrates (including bird chicks and nesting female birds, lizards, frogs, fish), invertebrates and bird eggs.