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Long-tailed macaque
Macaca fascicularis

SOCIAL ORGANIZATION AND BEHAVIOR

Long-tailed macaques live in multi-male/multi-female groups of six to 58 individuals, with the smallest groups found where there are no felids on the island of Simeulue in Indonesia (van Schaik & van Noordwijk 1985). One reason primates form groups is the benefit of increased protection against predators. In a group, there is higher likelihood of detecting a predator, and the chance of an individual primate becoming a victim of that predator decreases as group size increases. Frugivorous primates living in areas with predators must make a tradeoff; increasing group size enhances protection against predators but it also increases competition for fruit resources, which can be densely clumped and seasonally variable (van Schaik & van Noordwijk 1988; Sterck & Steenbeek 1997). On Simeulue, long-tailed macaques do not have to maintain large groups because of the lack of predators and therefore may have smaller groups to avoid feeding competition (van Schaik & van Noordwijk 1985). One way to reduce feeding competition in larger groups during times of fruit scarcity in areas other than Simeulue is for long-tailed macaque groups to split up into smaller foraging parties (Wheatley 1980; van Noordwijk & van Schaik 1987; van Schaik & van Noordwijk 1988).

Female long-tailed macaques remain in their natal groups and exhibit strong dominance hierarchies in which rank is passed on from mother to daughter and remains within a matriline (de Jong et al. 1994; van Noordwijk & van Schaik 1999). Females in a long-tailed macaque group are related in some way, either as sisters, half-sisters, cousins, or mother-daughter (de Jong et al. 1994). One measure of rank, especially among females, is the direction of grooming. Higher-ranking individuals enjoy more and longer-lasting grooming sessions from low-ranking individuals than vice versa (Wheatley 1999). Other important indicators of rank among female long-tailed macaques are the "bared-teeth display," in which the submissive female bares her teeth to the dominant female, and displacement, in which a dominant female displaces a submissive animal at a feeding site (van Noordwijk & van Schaik 1987; Sterck & Steenbeek 1997). When long-tailed macaque groups divide and forage separately, the main group consists of the highest-ranking females while the lower-ranking females form their own subgroup to forage (Sterck & Steenbeek 1997). High-ranking females benefit because of easier access to food, increased safety from predators and aggressive male macaques, as well as increased reproductive success (Wheatley 1999).

Males also exhibit a strict dominance hierarchy, with the highest-ranking male having the highest access to reproductive females and fathering the majority of infants born in the group during his tenure (Engelhardt et al. 2004). The second-ranking male, or beta male, fathers the remaining 20% of infants born into the group (de Jong et al. 1994). Aggressive interactions between males result in serious injuries, especially lacerations from their long, sharp canine teeth. Injuries obtained while fighting can lead to increased mortality through infection or predation (Wheatley 1999; van Noordwijk & van Schaik 2001). The relationship between the alpha female and male is maintained by grooming. The alpha female grooms the alpha male frequently, and interferes through aggressive behavior if lower-ranking females associate with him. Males of any rank groom females most frequently during estrus (Wheatley 1999).

Males emigrate from their natal groups with groups of their peers before sexual maturity, usually between four and six years old (de Jong et al. 1994). They generally immigrate into adjacent groups, but in their new groups young males will not attempt to establish themselves in the dominance hierarchy until at least seven years of age. Usually by nine years, they will attempt to take over the top position. If one male of the peer group attains the top rank, rather than challenging him, his peers will immigrate into a new group (van Noordwijk & van Schaik 2001). Males migrate multiple times over their lives and if they are unsuccessful at achieving the top dominance rank, they will immigrate into a new group and attempt another take-over. The average residence of males in a group is 45 months (van Noordwijk & van Schaik 1999; 2001). Even though they leave their natal groups, the sons of high-ranking females are more likely to have higher ranks in the dominance hierarchy of their new group than sons of low-ranking females (van Noordwijk & van Schaik 1999). Once a young male gains the position of highest-ranking male in the group, he will only hold that position, on average, for a period of three years (de Jong et al. 1994). When a male takes over for a former dominant male, the group conditions are conducive to infanticide. Males kill infants that are unlikely to be their own in order to shorten interbirth intervals. Females that lose a nursing infant will come into estrus faster than if they reared the infant completely. By inducing cycling in females, infanticidal males thus increase their chances of siring offspring as soon as possible after a take-over (Hrdy 1974).

REPRODUCTION

Reproductive output is linked to dominance status among female long-tailed macaques. The highest-ranking females have more offspring over their lifetimes than lower-ranking females, not only because they begin to reproduce at a younger age but also because their offspring have a higher chance of survival (van Noordwijk & van Schaik 1999). Some factors that contribute to the higher rate of survival for high-ranking females' offspring include: better access to food, a more central position in the main foraging group which offers protected from predators and a decreased likelihood of being harassed by low-ranking females (van Noordwijk & van Schaik 1987). Long-tailed macaques exhibit birth seasonality, which varies slightly across their range. In Gunung Leuser National Park on Sumatra, the majority of the births occur between July and November (van Noordwijk & van Schaik 1999). Where they are studied on West Java, there is a concentration of births in January and February (Engelhardt et al. 2004). Female reproductive success is linked to food availability; during years of high food abundance, birth rates are higher than years with food scarcity and in years with mast fruiting events, births occur earlier and are more frequent than in years with average fruit availability (van Noordwijk & van Schaik 1987; van Schaik & van Noordwijk 1988).

Sexual maturity in females is reached at four years of age and high-ranking daughters begin reproducing before 5.5 years of age while low-ranking daughters begin reproducing after 5.5 years. Males reach sexual maturity by age seven (Varavudhi et al. 1992; de Jong et al. 1994). Estrus is characterized by sex skin swelling, the inflation of the skin surrounding the anogenital region, and behavior patterns (Engelhardt et al. 2005). Females have a distinct set of vocalizations referred to as "copulation calls" that are heard during 80% of the copulations. Female long-tailed macaques mate multiple times throughout the day during the period of fertility (Engelhardt et al. 2004). About 80% of the infants born into a long-tailed macaque group are sired by the alpha male. One of the ways he ensures he is the dominant breeder is to guard the receptive females from subordinate males in the group (de Jong et al 1994; Engelhardt et al. 2004). The dominant male remains within five meters (16.4 ft) of the sexually receptive female and prevents other males from mating with her by aggressively displaying and physically preventing them from inspecting or coming near her (Engelhardt et al. 2004). Another male will take an opportunity to attempt to mate with the female if the dominant male is not closely guarding her, but the alpha male usually replaces him through aggressive behavior such as chasing, biting, or lunging (Engelhardt et al. 2005). Mate guarding is an energetically expensive behavior and is only seen in the few days surrounding a female's peak period of receptivity. Male long-tailed macaques are able to discern this period of receptivity because of behaviors exhibited by the female, which include solicitation, copulation calls, and grooming after copulation as well as apparent pheremonal cues (Engelhardt et al. 2004).

Females give birth to singletons and the interbirth interval averages 18 months, with females more likely to skip a year after giving birth to a surviving infant than after a year without successful reproduction (van Schaik & van Noordwijk 1988; de Jon et al. 1994). Females reach peak reproductive capacity at age 10 and they continue to reproduce until about 24 years of age, though reproduction significantly decreases after age 20 (van Noordwijk & van Schaik 1999).

PARENTAL CARE

Long-tailed macaque mothers are the primary caregivers of their newborn infants and are very protective of them, not allowing infants out of their grasp (Wheatley 1999). During the first weeks of life, the mother long-tailed macaque maintains contact with her infant almost constantly, but as the infant ages the amount of contact decreases (Meishvili et al. 1991). By four months, the mother spends significantly less time in contact with the infant and begins to exhibit normal ovarian cycles again. By the time the infant is 10 or 11 months of age the mother sharp rejects it and may act aggressively if it tries to nurse. (Meishvili et al. 1991).

Other females in the group are intensely interested in newborns, and attempt to touch, groom, and take the infant from the mother. Sometimes they are successful in "kidnapping" the infant, and if the mother is unable to retrieve the newborn, it is likely to die. High-ranking females that "kidnap" low-ranking infants are more likely to prevent the mother from rescuing the infant and subsequently the infant is more likely to die (Wheatley 1999). If an infant dies, the mother will not reproduce again until the next year, thus "kidnapping" may be a way for high-ranking females to decrease the reproductive success of low-ranking females in the group. In the first year of life, the survival rate of long-tailed macaque infants is 81%, but the overall survival rate of long-tailed macaques from birth to four years is 68% (van Noordwijk & van Schaik 1999). When infants reach juvenilehood, adult males spend more time playing with them, soliciting juveniles by making certain vocalizations (Wheatley 1999).

COMMUNICATION

Long-tailed macaques have an extensive vocal communication repertoire for use in many situations. There are two general classes of long-tailed macaque vocalizations, "harsh" and "clear" calls. Some important "harsh calls" are the "kra call," named for its sound, that are performed by allage and sex classes and are used in both mildly and highly excited macaques to show alarm and are named for their sound; "alarm calls," given by long-tailed macaques in the presence of a potential predator or when they feel threatened and are made of three to five, chirp-like pulses and "barks" which are heard during aggressive interactions between individuals (Palombit 1992; Wheatley 1999). "Clear calls" include a variety of "coos," which promote friendly interactions and avoid aggression between individuals and are heard between subordinate and dominant females as well as infants calling to their mothers (Wheatley 1999). Other calls include "screams" which are calls heard in aggressive interactions, especially by subordinates that are being victimized, "affiliation calls" given by females in an attempt to get closer to another female's infant, and "geckers" heard from infants during weaning conflicts or when in other situations of conflict (Wheatley 1999).

Content last modified: January 6, 2006

Written by Kristina Cawthon Lang. Reviewed by Carolyn Crockett.

Cite this page as:
Cawthon Lang KA. 2006 January 6. Primate Factsheets: Long-tailed macaque (Macaca fascicularis) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/long-tailed_macaque/behav>. Accessed 2014 April 25.