SOCIAL ORGANIZATION AND BEHAVIOR
Mouse lemurs live within a dispersed yet complex social structure and are not solitary although they forage alone (Radespiel 2000; Schwab 2000; Weidt et al. 2004; Dammhahn & Kappeler 2005). Within this dispersed
multi-male/multi-female system exist social relationships in which individual mouse lemurs are able to personally
recognize other mouse lemur individuals and have established relationships with them (Radespiel 2000; Weidt et al. 2004).
This is evidenced by regular encounters with conspecifics and steady home ranges and stable sleeping groups
(Radespiel 2000; Weidt et al. 2004). However, not all mouse lemurs have the same level of nighttime gregariousness; M. rufus,
being strongly solitary during its nightly activity periods, has been seen with conspecifics in only around 10% of observations (Atsalis 2008).
M. berthae has been seen in close proximity to another only 3.2 times in 100 hours of observation (Schwab 2000). In all, M. murinus may be the
most social of mouse lemurs studied, seen in close proximity with conspecifics 96 times per 100 hours of observation with females found frequently
in proximity throughout the night (Schwab 2000; Radespiel et al. 2001a).
Even though they exist in a dispersed social structure, mouse lemurs organize themselves into matrilineal groups (Radespiel et al. 2001b).
Photo: Verena Behringer
Sleeping groups are the basal social unit in mouse lemurs (Radespiel et al. 2001b; Weidt et al. 2004). While often alone at night,
at communal sleeping sites mouse lemurs are often found with others although again, there is variation between species as well as season
(see Radespiel 2006; Atsalis 2008). M. murinus sleeping groups can contain up to 16 individuals, but M. rufus sleeping groups usually
contain between 1 and 5 (Rasoazanabary 2006; Atsalis 2008). However, there are differences in the formation of sleeping groups between
the species of mouse lemur. In M. murinus for example, females usually sleep with a regular group of other females at sleeping sites,
while males usually sleep alone (Radespiel 2000). M. ravelobensis as well as M. berthae form sleeping groups comprised of both sexes
(Weidt et al. 2000). In M. murinus, such sleeping groups consist of closely related individuals and when no close female kin are available,
females will sleep alone (Radespiel et al. 2001b). Further, M. myoxinus do not form sleeping groups and usually sleep alone (Schwab 2000).
These differences underscore variation among the mouse lemurs relative to one another but overall, the same general dispersed social
organization follows (Weidt et al. 2004).
While the sleeping site changes, the composition of a discrete sleeping group stays relatively constant (Weidt et al. 2004). Sometimes, a
sleeping group of M. ravelobensis will aggregate prior to entering the sleeping site but at other times group members also enter individually
(Braune et al. 2005). In this species, within group coordination and between group spacing is maintained through various mechanisms including
vocal and olfactory communication (Braune et al. 2005). M. ravelobensis groups utilize exclusive sleeping sites (Braune et al. 2005).
Mouse lemurs exhibit a variety of social behaviors (Dammhahn & Kappeler 2005). Grooming and huddling occurs at the
beginning and end of the night, and other behaviors such as chasing and fighting are seen (M. berthae)
(Dammhahn & Kappeler 2005). In M. berthae, there are indications of female dominance over male individuals, as is also the
case in captive M. murinus (Radespiel & Zimmermann 2001b; Dammhahn & Kappeler 2005). In captivity, amongst
themselves, male individuals sometimes establish dominance relationships (Andrès et al. 2001; Radespiel et al. 2002).
Most social encounters in M. ravelobensis are not aggressive, and those that are usually occur right before
the mating season (Weidt et al. 2004).
There is evidence that male M. rufus, M. murinus, M. ravelobensis and M. berthae disperse while females are philopatric
(Atsalis 2000; Radespiel et al. 2001b; 2003b; Dammhahn & Kappeler 2005). However, male dispersal is not universal,
and in some populations, both sexes of M. murinus disperse, albeit more often in males (Radespiel et al. 2003a).
In M. griseorufus, young males disperse (Génin 2008). Dispersal in M. murinus occurs before 7 months old,
before the mating season (Radespiel et al. 2003a).
Mouse lemurs are best described as promiscuous, but although their mating systems are incompletely
known (reviewed in Kappeler 2000; Kappeler & Rasoloarison 2003; reviewed in Atsalis 2008). For example, the mating system
of M. berthae is promiscuous, and there is evidence to suggest scramble competition (Dammhahn & Kappeler 2005).
M. murinus in most cases mates within the framework of scramble competition polygyny but likely not exclusively so
(Eberle & Kappeler 2002). In captive populations of this species, both scramble competition and contest competition are seen and in
truth, the nature of the M. murinus mating system remains unclear; a wide ranging species such as M. murinus may be potentially flexible
exhibiting different mating systems as a result of the various environments in which they range (Eberle & Kappeler 2004b; Eberle et al. 2007; Génin 2007).
Mouse lemurs seasonally restrict mating to specific times of the year (when pooled between species roughly between
September-January but perhaps at other times); however there is variation between and within species between duration
and temporal onset of breeding (see Radespiel 2006 for a summary; Blanco 2008). Reproductive activity in mouse lemurs
is triggered by seasonal changes in the length of daylight (e.g. Wrogemann et al. 2001; Randrianambinina et al. 2003).
New data regarding M. griseorufus places their mating season between September and January, during the rainy season (Génin 2008).
During the breeding season, there are morphological changes in the genitals of both sexes (Atsalis 2008).
Male testes swell at the onset of the breeding season to a substantial size (see review of species and research in Atsalis 2008).
For example, the testes of captive M. murinus swell 5-10 times larger during the breeding season (Perret 1992).
The female vagina is closed except during estrus and birth and estrus, and at the beginning of an estrus cycle will exhibit
changes in color and morphology (Bourlière et al. 1961; Martin 1972; van Horn & Eaton 1979; Perret 1990).
Mouse lemur females can have more than one estrus cycle per breeding season (Blanco 2008).
For example, M. rufus females in the wild average 2.5 estrus cycles per reproductive season, each averaging 59 days
(Wrogemann & Zimmermann 2001). M. murinus females average 2.25 cycles per season each lasting 52 days
(Wrogemann et al. 2001). Although not all females show estrus synchrony, in wild M. rufus most come into estrus at the beginning of the
mating season and as the season passes, the proportion of females in estrus is reduced (Atsalis 2008; Blanco 2008).
In captive M. murinus, once breeding season is entered, the first female estrus is strongly synchronized within a population, but subsequent
cycles are not so (Radespiel & Zimmermann 2001a). Females in a given population of M. murinus are not all receptive
at the same time (Eberle & Kappeler 2004b). M. murinus females, both spatially and over time were not synchronized in their receptivity
(Eberle & Kappeler 2002). M. griseorufus females do not have synchronized estrus (Génin 2008). Receptivity is short-lived, with M. rufus
and M. murinus females receptive only for several hours of a single day of each estrus cycle (Wrogemann & Zimmermann 2001; Eberle & Kappeler 2004a).
In the western Malagasy Kirindy Forest, an individual female will come into estrus for only a single night, and will mate with several males during
that night and up to 11 times (Eberle & Kappeler 2004a; Eberle et al. 2007).
In captivity, M. murinus males form a dominance hierarchy, with higher ranking males showing more sexual behaviors than
lower ranking males and mating more often (Andrès et al. 2001; Radespiel et al. 2002). Before and during early
estrus, males search for chemosensory indications of receptive females (Andrès et al. 2001). Females reply
aggressively to male solicitations before the female becomes receptive (Andrès et al. 2001). In captivity,
sexual behaviors include smelling and licking of genitalia, sexual pursuit, and mounting. Copulation occurs in a
dorsal-ventral position with the male behind the female (Andrès et al. 2001). In captivity, the duration of
copulation varies (Wrogemann & Zimmermann 2001). M. murinus deposit sperm plugs during copulation (Eberle et al. 2007).
In captivity, there is experimental evidence for (M. murinus) female mate choice between available males (Craul et al. 2004).
Also in captivity, higher-ranking male M. murinus individuals usually have more reproductive success than subordinates although in a different
study of the species also in captivity, even though dominant males mated more, they only fathered around half the offspring born into the group
(Andrés et al. 2001; Radespiel et al. 2002).
M. rufus have a gestation length of 57 days, while the value for M. murinus is 62 days (Colas 1999; Wrogemann et al. 2001).
One wild M. griseorufus had a gestation length of 52 days (Génin 2008).
M. murinus and M. rufus reproduce in the first year of their lives (Perret 1992; Atsalis 2008; Sylvia Atsalis pers. comm.).
M. murinus testicular development in captive males averages around 186 days and wild M. rufus reproduce in the first year of their
lives (Perret 1992; Atsalis 2007).
At birth, M. murinus born in captivity weigh 7.2 g (0.3 oz) (M) and 4.6 g (0.2 oz) (F) (data compiled by Smith & Lee 1998).
The offspring of M. rufus have a gray back and a cream-colored belly contrasting sharply with the golden brown of their mother (Atsalis 2008).
M. murinus infants are similarly colored, with a gray back with a stripe down their back and a bare abdomen (Glatston 1979). The eyes are
open within two and four days of birth in M. murinus (Martin 1972; Glatson 1979). Infants are born capable of clinging (M. murinus) (Glatson 1979).
In captivity, M. murinus infants are carried until 6 weeks old but never ride on the fur of the mother (Martin 1972; Eberle & Kappeler 2006).
Mouse lemur mothers carry their infants by the mouth, grasping the infant’s dorsum (head, neck, back) (Martin 1972; Atsalis 2008).
Allomothering is seen in M. murinus with individual females nursing and grooming infants that are not their own (Eberle & Kappeler 2003; 2006).
In addition, captive female M. murinus show a preference in care to male infants
(Colas 1999). In captivity, M. murinus infants are first seen out of the nest at three weeks old and first eat solid foods at
one month of age (Martin 1975). Play in M. murinus starts between 10 and 13 days old, and also around this time the adult sleeping posture is adopted,
in which the animal curls on its side as opposed to the infant posture of sleeping flat on their ventrum (Glatson 1979).
Leaping in wild M. murinus starts at three weeks of age (Martin 1972). Infant M. murinus are
weaned around six weeks of age (Martin 1975). Independence is attained in M. rufus by two months of age (Atsalis 2007).
In captivity, M. murinus infants emit three distinct vocalizations, 'whistles' (isolation and threat contexts),
'tsaks' (threat contexts), and 'purrs' (grooming contexts) (Scheumann et al. 2007). Infants do not mark, but start urine-washing around 40 days of age (M. murinus) (Glatson 1979).
M. griseorufus usually raise only one litter per year, consisting of only one or two offspring (Génin 2008).
The same is true for M. rufus, although the litter may two or three offspring (Atsalis 2008).
Wild M. murinus litters are usually twins, but can also be singletons or triplets (Martin 1972). In general, the majority
of wild (M. murinus) females die before they can reproduce, with only half of individuals of both sexes reaching an age
of 10 months old (Lutermann et al. 2006).
Mouse lemurs lack true scent glands, however scent marking which deposits saliva, urine, feces, and genital secretions is used
in communication (Glatston 1983; Perret 1995). Urine-marking, especially through urine-washing, is the most common marking
behavior in captive M. murinus and urine functions as the primary mode of olfactory communication (Perret 1995; Schilling 2000).
In captivity, olfactory communication in mouse lemurs functions in individual recognition, sexual attraction, conveying alarm,
and potentially in territory marking. Further, captive dominant individuals mark more than others (Glatston 1983). Females in
estrus increase ano-genital marking as well as muzzle rubbing behaviors which may serve to inform conspecifics of their reproductive state
(Buesching et al. 1998). Olfactory communicatory urine-washing and mouth-wiping (M. ravelobensis) are seen after leaving the sleeping
site at the beginning of the night but not upon retiring at the end of the activity period, probably functioning to help mouse
lemurs find their sleeping site as well as potentially marking it as their own (Braune et al. 2005).
LISTEN TO VOCALIZATIONS
Mouse lemurs have been described as very vocal, emitting seven or eight general types of vocalizations (Martin 1972; Schilling 2000).
In addition, there are several types of ultrasonic call which are emitted by M. murinus (Cherry et al. 1987; Schilling 2000).
There is evidence that mouse lemur species have differences in reproductive advertisement calls, allowing sympatric species to
find and mate with conspecifics (Zimmermann et al. 1999; Braune et al. 2008). However, there is significant variation in
predator-avoidance whistle calls such that differences within a given species can be as great as differences between species
(Zimmermann et al. 1999). The trill, which is used in group (M. ravelobensis) coordination, is different in each group and is
heard at the reunion of the sleeping group at the end of the nightly activity period (Braune et al. 2005). Further, M. murinus
females have a special trill which they utter during estrus which serves to advertise their reproductive state (Buesching et al. 1998).
Males also emit a trill call to advertise during the mating system, and in many cases this call is unique and identifiable to an
individual M. murinus male (Zimmermann & Lerch 1993). Some contact calls likely serve to communicate information about
dominance (Schilling 2000).
Visual communication such as postures and facial expressions play a limited role in mouse lemur communication (Schilling 2000). Interestingly, there is evidence of
vocal learning, in which subordinates or immigrant males may copy the vocalizations of resident males with the goal of acceptance
into a new population and/or potential reproductive opportunities (Hafen et al. 1998).
Content last modified: February 11, 2009
Written by Kurt Gron. Reviewed by Sylvia Atsalis.
Cite this page as:
Gron KJ. 2009 February 11. Primate Factsheets: Mouse lemur (Microcebus) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/mouse_lemur/behav>. Accessed 2015 January 25.