Mouse lemur
Microcebus sp.

SOCIAL ORGANIZATION AND BEHAVIOR

Mouse lemurs exist within a dispersed yet complex social system and are not solitary, but usually 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, seen with conspecifics only around 10% of observations (Atsalis 2007). Sleeping groups are the basal social unit in mouse lemurs (Radespiel et al. 2001; 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 2007). Sleeping groups usually consist of between two and five individuals (M. murinus) (Glaston 1986). 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. 2001). 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 actual site of sleep changes, the composition of a discrete sleeping group will stay 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. murinus and M. berthae disperse while females are philopatric (Radespiel et al. 2001; 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).

REPRODUCTION

The mating systems of the various species of mouse lemurs are best described as promiscuous, but are incompletely known (reviewed in Kappeler 2000; Kappeler & Rasoloarison 2003; reviewed in Atsalis 2007). 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 (Eberle et al. 2007). In fact, the very nature of the M. murinus mating system is unclear and up to debate (Génin 2007). This might be due to the fact that wide ranging species such as M. murinus are potentially flexible and might have several different reproductive systems, a byproduct of the various environments throughout their range (Eberle & Kappeler 2004b).

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 M. rufus as well as other species of mouse lemur appears to be predominantly motivated by yearly changes in the length of daylight (Wrogemann et al. 2001; Randrianambinina et al. 2003). In addition, mouse lemur seasonal weight fluctuations are also related to changes in daylight duration (Perret & Aujard 2001). 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 2007). Male testes swell at the onset of the breeding season to a substantial size (see review of species and research in Atsalis 2007). 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 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 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). In wild M. rufus, in which all females are in estrus at the beginning of the mating season and as the season passes, the proportion is reduced (Atsalis 2007). 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). Some M. rufus females in the wild show estrus synchrony and some do not (Blanco 2008). 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 only receptive 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).

M. murinus males in captivity 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, a dominant male M. murinus does not always have higher reproductive success than other males (Andrès 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 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).

PARENTAL CARE

At birth in captivity, M. murinus weighs 7.2 g (0.3 oz) (M) and 4.6 g (0.2 oz) (F) (data compiled by Smith & Lee 1998). M. rufus have a gray back and a cream colored belly (Atsalis 2007). The eyes are open within two days of birth in M. murinus (Martin 1972).

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). In the wild, infant carrying is in the mouth of the mother, with wild mothers seen grasping the dorsum (head, neck, back) of the infant (Martin 1972; Atsalis 2007). Allomothering is seen in captive mouse lemurs, and individual females nurse and groom infants that are not their own (Eberle & Kappeler 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). 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. 1007).

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 each annual litter typically contains two or three offspring (Atsalis 2007). 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).

COMMUNICATION

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 which may serve to inform conspecifics of their reproductive state (Buesching et al. 1998). Olfactory communicatory urine-washing and mouth-wiping (M. ravelobensis) is seen after leaving the sleeping site at the beginning of the night but not upon retiring at the end of the activity period and probably functions to help mouse lemurs find their sleeping site after activity, as well as potentially marking it as their own (Braune et al. 2005).

LISTEN TO VOCALIZATIONS

• Microcebus rufus: Vocalization  (Erik Patel; Cornell University)

Mouse lemurs have been described as very vocal, emitting seven or eight general types of vocalization (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).

Content last modified: September 26, 2008

Written by Kurt Gron.

Cite this page as:
Gron KJ. 2008 September 26. Primate Factsheets: Mouse lemur (Microcebus) Behavior. <http://pin.primate.wisc.edu/factsheets/entry/mouse_lemur/behav>. Accessed 2008 November 21.