The scientific name of the Crab-eating Macaque is Macaca fascicularis. Macaca comes from the Portuguese word macaco, which was picked up from makaku, a Fiot (West African language) word (kaku means ‘monkey’ in Fiot). Fascicularis is Latin for ‘a smal

Depending on sub-species, the body length of the adult monkey is 38-55 centimetres (15–22 in) with comparably short arms and legs. The tail is longer than the body, typically 40–65 cm (16–26 in). Males are considerably larger than females, weighing 5-9 kilograms (11-20 lb) compared to the 3–6 kg (7-13 lb) of female individuals. Macaca fascicularis is a very social animal that lives in groups anywhere from 5-60+ animals. These groups are multi-male groups, normally containing 2-5 males and 2-3 times as many females. The number of immature is usually comparative to the number of females. Their group size often depends on the level of predation and availability of food. Their 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 female-based groups. Males generally first emigrate from their natal group at the age of 4-6. They will remain in a group up to four or five 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. High-ranked males generally are more successful at reproduction and high-ranked females generally fare better at raising surviving offspring. The females are organized into matrilines, which are the female-based families consisting of the resident females and their offspring. Matrilines are ranked and some families have greater social power than others and this difference in rank is maintained over several generations. Matrilineal overthrows rarely occur and when they do they have severe consequences to the reproductive success of the defeated matriline in the following year. After a gestation period of 167–193 days, the female gives birth to one infant. The infant’s weight at birth is approximately 350 grams (12 oz). Infants are born with black fur and this fur will begin to turn to a yellow-green, grey-green, or reddish-brown shade (depending on the sub-species) after about three months of age. It is suggested this natal coat indicates to others the status of the infant and other group members treat infants with care and rush to their defence when distressed. Newly immigrated males will sometimes commit infanticide on infants not their own, and high-ranked females sometimes kidnap the infants of lower-rank females. These kidnappings usually result in the fatality of the infants, as the other female usually is not lactating. Young juveniles stay with the mother and relatives mainly, and as male juveniles get older they become more peripheral to the group. Here they play together forming crucial bonds that may help them when the emigrate from their natal group. Males that emigrate with a partner seems to be more successful than those that move off alone. Young females on the other hand stay in the centre of the group and become incorporated into the matriline they were born into. Results of a research shows that male Crab-eating Macaques will groom females in order to get sex. The study found that a female has a greater likelihood to engage in sexual activity with a male if he had recently groomed her, compared to males who had not groomed her