Long tailed or crab eating macaques (Macaca fascicularis) are found in southeast Asia from Burma to the Philippines and southward through Indochina, Malaysia, and Indonesia. They are found as far east as the Timor Islands.
Long-tailed macaques are "ecologically diverse." Some of the habitats in which they have been found are primary forests, disturbed and secondary forests, and riverine and coastal forests of nipa palm and mangrove. Long-tailed macaques live most successfully in disturbed habitats and on the periphery of forests.
In Sumatra, they achieve their highest population densities in mixed mangrove swamps, secondary hill forests, and riverine forests. Some were also observed in freshwater swamps, scrub grassland, lowland primary forests, and rubber groves.
In Thailand, long-tailed macaques occur in evergreen forests, bamboo forests, and in deciduous forests.
In Malaysia, they are abundant in coastal lowland forests.
This species has been observed drinking much water and eating crabs, they often live near bodies of water. Of the various habitats occupied by long-tailed macaques, the swamp forests seem to have the highest density of them.
In recent years, habitat alteration has expanded the range of some populations of long-tailed macaques. In Malaysia, cleared land, such as plantation areas, has been colonized by this species. It has been observed that some disturbed habitats have higher troop and population sizes than some pristine forests.
This species has the highest degree of arboreality of all macaque species. One study of long-tailed macaque behavior reported that they never came to the ground except within 5 m of the edge of a river near their tree. The population densities of this diurnal species vary from 10 to 400 per squared kilometer.
3 to 7 kg
(6.6 to 15.4 lbs)
40 to 47 cm
(15.75 to 18.5 in)
The body fur of long-tailed macaques tends to be grey-brown to reddish brown. These colors are always paler ventrally. The face is brownish-grey with cheek whiskers. The eyes are directed forward for binocular vision. The nose is flat and the nostrils are narrow and close together (catarrhine condition). Long-tailed macaques have shovel-shaped incisors, conspicuous canines, and bilophodont molars. The tooth formula is I 2/2, C 1/1, PM 2/2, and M 3/3.
The body length, not including the tail, is 40 to 47 cm. The greyish- brown or reddish colored tail is 50 to 60 cm. Long-tailed macaques exhibit sexual dimorphism in size. The average weight for males is 4.8 to 7 kg and 3 to 4 kg for females, approximately 69% of average male weight.
Females have an average interbirth interval of 390 days.
Number of offspring
162 days (average)
Time to weaning
420 days (average)
Age at sexual or reproductive maturity (female)
4 years (average)
Age at sexual or reproductive maturity (male)
6 years (average)
In Sumatra, each social group of these monkeys contains an average of 5.7 males and 9.9 adult females. Although females outnumber males, indicating that males have more mates available to them than do females, both sexes may mate with multiple partners. However, the alpha male, or highest ranking male, of the group has the greatest access to mates of any males, and probably sires the most offspring.
Males reach sexual maturity at approximately 6 years of age, whereas females mature by about 4 years of age. Higher-ranking females become reproductively mature before lower-ranking females. The offspring of these higher-ranking females have a greater chance of survival than do the offspring of lower-ranking females. Both of these phenomena are related to the greater food availability and decreased amount of aggression experienced by the higher ranking females.
Female long-tailed macaques show a conspicuous cyclicity of sexual behavior during their menstrual cycle. As they approach ovulation, females experience a swelling of the skin in the perineal region. However, there has been no direct correlation between the frequency of copulation and the degree of swelling of genital tissues. This concealment of ovulation could exist in order to persuade consorting males to stay with females longer.
As a side effect of the prolonged estrus period and concealment of ovulation, it is difficult for humans to estimate the length of gestation. However, it seems likely that the gestation averages approximately 162 days. The average interbirth intervasl is approximately 390 days, indicating that females can produce young each year if high ranking, and every other year otherwise.
Young are nursed until they are approximately 420 days of age. The average interbirth interval is reported to be 390 days, which is less than the average time until weaning. Both the length of nursing and the interbirth interval may be affected by the rank of the mother.
It is known that the births in this species peak from May to July, corresponding with the rainy season.
As in all primates, there is an extended period of juvenile dependence. Females provide the bulk of the care for offspring. The young receive nourishment, encouragement, grooming, protection, and teaching from the mother. Young females are likely to remain in the troup into which they were born, whereas males are likely to emmigrate at or near sexual maturity.
Although the lifespan of this species has not been reported, it is likely to resemble that of other members of the genus, which seem able to obtain an maximum age of around 30 years in captivity.
1.25 km^2 (average)
Long-tailed macaques live in multi-male groups consisting of about thirty members. At sexual maturity, males leave their natal group, and join either bachelor groups or new social groups. Since males leave the natal group, they are subject to more predation, disease, and injury thna are females. Once a male finds another group in which to reside, he may replace some of the existing high-ranking males. Male replacement itself is a process in which a foreign male adult successfully takes over a resident male's harem position. These events are highly aggressive activites, and the participating adults are usually injured.
Despite aggression between males, this species is characterized by a genral lack of aggression between groups. Intergroup interactions are avoided/ When these groups meet, there tend to be high levels of aggression, involving chasing the non-resident group out of the area. Loud vocalizations and branch-bouncing are characteristic parts of these interactions. Males and females may use open mouth threats. This involves showing the enemy the incisors and canines, and pulling the ears and nose back. The alpha male is usually the one who leads the aggression by doing 90% of the branch-bouncing.
Within groups, a strict linear dominance hierarchy develops among males. This hierarchy is determined by such factors as age, size, and fighting skills.
Since females do not disperse, they are the stable core of a group. Females have a tendency to have close bonds with their maternal relatives throughout their lives. There is, however, a dominance hierarchy among females in a group. The acquisition of rank involves active intervention by maternal kin, and the differential treatment by unrelated members of the group. Grooming among females is a common activity. It is especially common for low-ranking females to groom higer-ranking females. This allows the lower-ranking females to receive less harassment, more support in aggresive interactions, and access to limited resources.
Long-tailed macaques are unique among other non-human primates because of their ability to show learned or cultural behavior. This cultural behavior was observed in the preparation of food by long-tailed macaques. On one occasion, an adult female dipped a piece of fruit into a river and then she consumed it. It was proposed that perhaps the female was cleaning sand off the fruit. Scientists investigated this further on other individuals who showed this behavior. Some of the macaques washed sandy fruit in the river, but some of them also washed fruit the scientists had cleaned prior to distributing them. There were also long-tailed macaques that simply ate the cleaned fruits without washing them. The controversy of what cultural behavior means is still being researched.
The day range of this species averages 1,900 square meters. The total of all the day ranges, or the home range, of this species averages 125 hectares.
Communication and Perception
As in other species of the genus Macaca, it is likely that these animals use a combination of visual (facial expression, body postures), auditory (vocalizations), physical (grooming, play, mating, aggression) and possible chemical (olfactory) signals as a part of their repertoire of communication.
Long-tailed macaques are omnivores, and exploit many different food types, reflecting the diversity of habitats they can utilize. The average length of feeding bouts is 18.3 minutes. There may be on average of twenty bouts per day. They eat a wide variety of foods such as fruits, crabs, flowers, insects, leaves, fungi, grasses, and clay. Clay may be eaten for the potassium found in it, although the potassium levels in the clay are low. However, 96% of the feeding time per day is spent eating fruit. Some limited observations suggest that long-tailed macaques select fruit based on ripeness, which is based on color.
To the extent that these animals are prey for other species, they may affect populations of those species. Macaca fascicularis may be an important predator in its ecosystem, and may have some impact on prey species.
Economic Importance for Humans: Negative
Long-tailed macaques have been known to feed in cultivated fields on such items as young dry rice, cassava leaves, rubber fruit, taro plants, and other crops. They also take food from graveyards, garbage cans, and garbage pits. They have also become involved in aggresive interactions with people.
Economic Importance for Humans: Positive
Long-tailed macaques, along with other species of macaques, have benefited humans through their use as research models in immunology, surgery, toxicology, and pharmacology. They are also important members of ecosystems and may serve as a basis for ecotourism ventures. They are sometimes still hunted for food.
There are nine national parks, nine reserves, and two sanctuaries in which some long-tailed macaques reside. Regardless of the type of habitat, there must be at least 500 squared kilometers of habitat necessary to support a viable population of 5,000 long-tailed macaques. This is the minimum size for a reserve for this species.
Long-tailed macaques receive some protection in temple ruins in Thailand and protection and food in temples in Bali. In Malaysia, long-tailed macaques are legally protected, and they are fed and protected in urban forests and parks. In the Philippines, there is much interest in protecting this species. In Indonesia, the species is well-protected, but some of the reserves are being considered for oil drilling and harvesting. Some people in Bali, in fact, consider these primates to be sacred. This may increase the chances of their survival in these reserves. In Thailand, long-tailed macaques may be hunted, captured, or kept in captivity only under license. The export of this species is regulated by a quota system.
Although there are some sanctuaries for long-tailed macaques, hunting is still a problem. In Thailand and Borneo, they are hunted for food. This species is also killed because it is a pest to agriculture. The fact that these macaques destroy crops has prevented some governments from making serious conservation efforts. Long-tailed macaques are collected for medical research. They are one of the five most used primate species in medical research. Many of these macaques were exported to the United States and Great Britian. Habitat loss in these organisms is occurring due to extensive logging operations.
The long-tailed macaque is also called the crab-eating macaque, or the cynomolgus or 'java' monkey.
Nancy Shefferly (editor), Animal Diversity Web Staff.
Christopher Bonadio (author), University of Michigan.
Phil Myers (editor), Museum of Zoology, University of Michigan.
Harvery, R., R. Martin, T. Clutton-Brock. 1987. Life Histories in Comparative Perspective. Pp. 181-196 in B. Smuts, D. Cheney, R. Seyfarth, R. Wrangham, T. Struhsaker, eds. Primate Societies. Chicago and London: The University of Chicago Press.
Lindburg, D. 1980. The Macaques: Ecology, Behavior, and Evolution. New York: Van Nostrand Rheinland Co..
Melnick, D., M. Pearl. 1987. Cercopithecines in Multimale Groups: Genetic Diversity and Population Structure. Pp. 121-134 in B. Smuts, D. Cheney, R. Seyfarth, R. Wrangham, T. Struhsaker, eds. Primate Societies. Chicago and London: University of Chicago.
Paul, A., J. Kuester. 1996. Differential Reproduction in Barbary Macaques. Pp. 309-313 in J. Fa, D. Lindberg, eds. Evolution and Ecology of Macaque Society. New York: Cambridge University Press.
Payne, Junaidi, F., Phillipps, Karen. 1985. The Field Guide to the Mammals of Borneo. Petaling Jaya, Malaysia: Setiakawan Printers Sdn. Bhd..
Visalberghi, E., D. Fragaszy. 1990. Food-Washing behaviour in tufted capuchin monkeys, Cebus apella, and crabeating macaques, Macaca fascicularis. Animal Behaviour, 40: 829-836.
Wolfheim, J. 1983. Primates of the World: Distribution, Abundance, Conservation. Seattle and London: University of Washington Press.
Zeller, A. 1996. The inter-play organisation and facial communication in the macaques. Pp. 527-529 in J. Fa, D. Lindberg, eds. Evolution and Ecology of Macaque Society. New York: Cambridge University Press.