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 2013 May 24.
