SOCIAL ORGANIZATION AND BEHAVIOR
Group size in bamboo lemurs can vary by location. Differences can at least
partially be attributed to the degree of forest degradation at each particular
study site (Grassi 2006). In general, H. griseus have variable group
sizes between two and nine individuals, although groups can sometimes be as
large as 11 individuals (Tan 1999; review in Mutschler & Tan 2003; Grassi
2006). H. aureus groups are usually small (2-4 individuals), but can
contain up to eight individuals (Meier et al. 1987; Tan 2006). H.
meridionalis groups of up to seven members have been observed (Mutschler
& Tan 2003). H. occidentalis groups of up to six individuals have
been seen (Mutschler & Tan 2003).
Photo: Edward Louis
Some of the best long-term information about social groups comes from the
Aloatran bamboo lemur (H. alaotrensis). This species lives in small
"one male" groups (Mutschler & Tan 2003). Groups can be as large as nine
individuals, but are usually smaller, averaging just over four individuals per
group (Mutschler 2002; Nievergelt et al. 2002). Groups larger than two contain
subadults, and groups can contain more than one adult of the same sex. This
includes groups with one adult of each sex (42% of groups), two adult females
and an adult male (19%), two adult males and an adult female (12%) and multiple
males and females (27%). Groups are generally stable, and changes occur by
immigration of adult males, births, deaths, and emigration. Further, groups
generally stay in and use the same general territory over time. The species is
rarely encountered alone (Nievergelt et al. 2002).
Both sexes disperse from their natal groups in H. alaotrensis, with
indirect evidence indicating females disperse as subadults and males disperse as
adults (Mutschler et al. 2000). H. aureus disperse at around three
years of age (Tan 2000 cited in Mutschler & Tan 2003).
H. alaotrensis and H. griseus are territorial and defend
their territories from other Hapalemur groups (Nievergelt et al. 1998; Tan
2006). In H. alaotrensis, intergroup interactions occur near the
borders of the territory and involve both adult sexes, with the resident group
detecting another group and immediately moving toward the territorial boundary
(Nievergelt et al. 1998). Males play a more active role than females in
territorial defense (Nievergelt et al. 1998). Intergroup interactions are
characterized by visual monitoring including staring, scent marking (including
marking of substrates, tail scent marking, and marking of group members),
displays (locomotive and confrontation displays), chasing, and vocalizations
(Nievergelt et al. 1998). Intergroup interactions are similar in H.
griseus, where there are characterized by scent-marking, vocalization and
chasing (Tan 2006).
In the wild, female H. alaotrensis are dominant over males (Waeber
& Hemelrijk 2003). Females lead group progressions more than males, they
are more aggressive, and groom more often (Waeber & Hemelrijk 2003).
Aggressive behaviors include open mouth displays, visual monitoring, vocal
threats, chasing and fighting. Submissive behaviors include avoidance,
whimpering, vocalizations, and vocal threats/rumbles (Waeber & Hemelrijk
2003). H. aureus have an ambiguous dominance relationship between
males and females (Tan 2006). In the wild, there is some evidence to indicate
that female H. griseus are dominant over males, and in captivity, this
is the case (Tan 2006; Digby & Stevens 2007).
In H. alaotrensis, depending on the number of resident adult females
in the group, the mating system is either monogamous or polygynous. While
social groups may contain more than one adult male, only one adult male within
the group reproduces (Nievergelt et al. 2002). Extra-group paternity is
uncommon (Nievergelt et al. 2002). However, more than one female within a group
may be reproductive, and the reproductive females may be related (Nievergelt et
al. 2002). In the wild, H. alaotrensis give birth over a six-month
period, from September to February and twinning is common (at least a third of
births) (Mutschler et al. 2000; Nievergelt et al. 2002). Wild H.
alaotrensis females reproduce for the first time as early as two years old,
while males begin reproduction as early as three years of age (Nievergelt et al.
In Ranomafana National Park in eastern Madacascar, most H. griseus
mating takes place in June and July with a subsequent birth season in October
and November. Elsewhere, in Maroantsetra, the birth season is different,
occurring between January and February (Petter & Peyrieras 1975). At
Ranomafana National Park, H. aureus mating occurs in July and August,
with a subsequent birth season in November and December (Tan 2000 cited in Tan
2006). Most births in wild H. griseus are singletons, and H.
aureus gives birth to singletons as well (Tan 2000 cited in Tan 2006). The
interbirth interval in wild H. griseus is 12 months (Wright 1990; Tan
2000 cited in Tan 2006).
In the wild and in captivity, gestation for H. griseus is around 135
days, and captive H. alaotrensis gestation is around 145 days (Wright
1990; Beattie & Feistner 1998; Tan 2000 cited in Tan 2006). Gestation in
wild H. aureus is around 138 days (Tan 2000 cited in Tan 2006).
In captivity, H. griseus weigh an average of 45.2 g (1.6 oz) at
birth (Wright 1990). H. alaotrensis neonates are estimated to weigh
around 63 g (2.2 oz) (Steyn & Feistner 1994). Infant H. griseus in
captivity and in the wild are weaned at about four months of age and captive
H. alaotrensis are weaned between 20 and 24 weeks of age (Wright 1990;
Beattie & Feistner 1998; Tan 2000 cited in Tan 2006). Wild H.
aureus are weaned before they are six months old (Tan 2000 cited in Tan
Captive infant H. alaotrensis are born with their eyes open (Steyn
& Feistner 1994; Beattie & Feistner 1998). By six to eight days old the
infant can cling to its mother and can move independently (Beattie &
Feistner 1998). By two weeks old, infants can move skillfully by themselves
(Steyn & Feistner 1994). By three weeks of age, infants are no longer
parked, as they will not stay stationary (Taylor & Feistner 1996). Solid
foods are first consumed between five and six weeks of age in this species
(Taylor & Feistner 1996). In general, twin H. alaotrensis grow
more slowly than singletons, in addition to being carried less and weaning later
(Taylor & Feistner 1996).
Wild H. griseus mothers carry infants in their mouth until they are
two weeks old after which the infant clings to its mother. A similar pattern in
seen in H. aureus. Wild H. griseus park their infants and in
captivity, infants are usually parked for between 20 and 30 minutes. Captive
H. griseus are parked until the infant is mobile enough to start
following its mother after which it is carried on its mothers back mostly, but
also by its father and sometimes siblings. By the third month of life, carrying
is infrequent (Wright 1990). Solid foods are first consumed around six weeks of
age in wild H. griseus and around ten weeks in H. aureus (Tan
2000 cited in Tan 2006).
Little is known about communication in the genus Hapalemur. H.
griseus vocalizations have been divided into five general types, including
mother-infant contact calls and contact-seeking calls, distance communication
calls (including cohesion calls, distant contact calls, and mating calls), alarm
calls, contact-rejection calls, and distress calls (Petter &
Charles-Dominique 1979). Wild H. alaotrensis have been heard emitting
a minimum of nine types of vocalizations (Mutschler et al. 1994 cited in
Nievergelt et al. 1998). Contact calls in H. aureus are grunt-like and
the species emits a characteristic great call at night (Meier et al. 1987).
LISTEN TO VOCALIZATIONS
Several types of scent marking have been observed in H. alaotrensis
in contexts of intergroup interactions, including substrate scent marking, tail
scent marking, and scent marking of group members (Nievergelt et al. 1998).
During scent marking, males will rub substrates with the brachial glands and
females will rub substrates with their anogenital region while uriniating
(Nievergelt et al. 1998). In tail scent marking, the lemur will pull its tail
through its legs and rub its wrists along the tail, often in view of an opponent
during intergroup interactions. In scent marking of group members, the lemur
will use its wrist glands to mark other group members on their body, applying
both wrist glands at the same time (Nievergelt et al. 1998).
Several types of display communiction are also recorded for H.
alaotrensis in contexts of inter-group interactions. These include
locomotor displays (where the individual runs around in circles), and
confrontation displays (where the individual runs at another and stops just
short of the other and then jumps backwards) (Nievergelt et al. 1998).
Latrine behavior in H. griseus likely serves some communicatory
function (Irwin et al. 2004).
Content last modified: July 22, 2010
Written by Kurt Gron.
Cite this page as:
Gron KJ. 2010 July 22. Primate Factsheets: Bamboo lemur (Hapalemur) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/bamboo_lemur/behav>. Accessed 2015 July 1.