Ruffed lemur
Varecia

SOCIAL ORGANIZATION AND BEHAVIOR

Ruffed lemur social organization is marked by significant variation in both group organization as well as group composition. This has been suggested to be the result of the social system being adaptable to allow for an inability of the species to change its feeding ecology (Vasey 2003). Some of the variation in past studies of ruffed lemur social organization might be attributed to the short-term or seasonal nature of field studies not adequately covering yearlong patterns of social behavior (Vasey 2003). Ruffed lemurs are organized into dispersed social networks which include core groups organized within a core community. Even though the core community lives within a discrete community home range, the entire community is never seen together in the same location at the same time (Morland 1991a; Rigamonti 1993; Vasey 1997a; 2006). The structure of the core group is variable but often consists of two reproductive females in addition to males and subadults, and can range from a pair of individuals up to 9 (Vasey 1997a). Rare interactions between group males are typically agonistic (Morland 1991b).

Perhaps the ruffed lemur social structure is best described as multi-male/multi-female fission-fusion social organization (Vasey 1997a; 2006). Such communities are dispersed core social groups that interact with other core groups in the community, however interaction between different core social groups is curtailed during the cold rainy season, the period of gestation and mating (Rigamonti 1993; Vasey 1997a; 2006). During this period of the year, small subgroups are formed and range over small areas within the communal home range (Morland 1991b). Often, these subgroups consist of a male, female, and their offspring or even just an adult male and adult female and might be misconstrued as monogamous (Morland 1991b; White 1989). In captivity, the relationships between mothers and their adult female offspring are not stable throughout the year, with affiliative behavior seen between the two during the birth season but not the mating season (White et al. 1992). The fission-fusion nature of the social organization is manifested on two levels, the yearlong daily changes in subgroups and the seasonal dispersal of core groups into core areas (Vasey 2006).

Even though ruffed lemur communities are not cohesive units, the home range is communally defended. In addition, there is some evidence that only females participate in communal home range defense against females from other groups, which includes agonistic behaviors including chasing, scent-marking, calling, and sometimes physical contact with members of neighboring communities (Morland 1991a; 1991b; Vasey 1997a; 2006). Territorial disputes occur most often during the hot months when resources are more readily available and happen at the boundaries between communal home ranges (Morland 1991b; Vasey 2006). During such disputes, males will scent-mark but will not chase, remain uninvolved and are relatively silent (Morland 1991b; Vasey 2006). Group size is very variable, with cohesive groups ranging from a pair to 31 individuals (White 1991; Morland 1991a; Rigamonti 1993; Vasey 1997a; 2003; 2006).

In captive and free-ranging ruffed lemurs, females are almost always dominant to males, winning almost all agonistic encounters with them and rarely showing submissive behavior towards a male (Kaufman 1991; Raps & White 1995; Meyer et al. 1999). In the wild, the nature of female group dominance is more ambiguous. While it is possible for females to be dominant, wild groups cannot be described definitively so, as there is some inter-group variation in dominance patterns (Overdorff et al. 2005).

In the wild, common aggressive behaviors include attacks, cuffs, grapples, and chases while in captivity the aggressive repertoire includes the stare, charge, chase, lunge, cuff, feint-to-cuff, bipedal hop, pounce on, push down, and bite (Pereira et al. 1988; Overdorff et al. 2005). In the wild, chatter vocalizations are used to signal submission (Overdorff et al. 2005). Captive animals also chatter to show submission in addition to displacement, head turning/eye aversion, cowering/flinching, grimacing, backing away, fleeing, and jumping away (Pereira et al. 1988). In the wild, affiliative behaviors include the greeting behavior performed by females in which their bodies are intertwined. In addition, other wild affiliative behaviors include playing and social grooming. Often, affiliative behaviors are highly seasonal and some are only performed by one sex, such as the male behaviors of the squeal approach and anogenital inspections, which only occur during the mating season (Morland 1991a). In captivity, affinitive social behaviors include group movement, huddling together with bodily contact, greeting by sniffing and social grooming, an activity performed by all group lemurs over 5 months of age (Pereira et al. 1988). In captivity, all group members will play, but subadults participate more often than adults. Play can include wrestling, grappling, chasing, fleeing and solitary play (Pereira et al. 1988).

REPRODUCTION

Wild ruffed lemurs exhibit a seasonal polygamous mating system contrary to initial reports of monogamy in the species (Vasey 2007). In the wild, mating occurs with community members as well as with members from other communities. In addition, a single male or female will often mate with more than one partner in a single mating season and within a community, multiple males and females actively mate (Morland 1993b; Vasey 2007). Near the northern limit of the ruffed lemur range, mating occurs in the cold rainy season, between May and July (Morland 1993b; Vasey 2007). As expected in a species with a specific mating season, births are also seasonal. In the wild on the Masoala peninsula, births occur during the hot dry season during November and are highly synchronized (Vasey 1997a). In captivity, discrete mating and birth seasons are also observed (Brockman et al. 1987).

Just prior to and during estrus, both wild and captive females exhibit swelling of the sex skin, peaking around the middle of estrus (Bogart et al. 1977; Brockman et al. 1987; Vasey 2007). Estrous cycles average 14.8 days in captivity (Brockman et al. 1987). Male testicular volume also increases as the mating season nears, peaking prior to or at the time of breeding (Bogart et al. 1977; Foerg 1982; Brockman et al. 1987). Aggression among ruffed lemurs of the same sex increases as well during the mating season (Morland 1993b).

Before copulation, the male will perform a display which includes moving toward the female while lowering his head and squealing, roar-shrieking with the female, licking or sniffing the female's genitals, submissively chattering, mounting and scent-marking. Females also perform displays that include roar-shrieking with the male, hitting, biting, and posturing of her body for mounting (Vasey 2007). The male mounts the female by grasping her hind limbs or a branch with his hind limbs and grasping her torso and thrusting. Aggressive behavior by the female is often directed towards the male who is attempting to mate with her and a mating pair will often copulate a number of times in a bout of mating (Foerg 1982; Morland 1993b).

In captivity, gestation averages around 102 days and in the wild, is slightly longer, at 106 days with an inter-birth interval of one year (Bogart et al. 1977; Foerg 1982; Rasmussen 1985; Brockman et al. 1987; Vasey 2007). Reproductive maturity in captivity is reached in both sexes around 18-20 months of age, during the second post-natal breeding season (Foerg 1982; Porton 1989). In the wild, reproductive maturity is reached later, with females only coming into estrus at 3 years old and males showing no signs of reproductive maturity until at least 5 years old (Morland 1991a). Reproductive activity in captivity for females can last into the 23rd year of life (Weigler et al. 1994).

PARENTAL CARE

In both the wild and captivity, ruffed lemur births are usually multiple, averaging around two infants per birth in captivity (Boskoff 1977; Morland 1990; Weigler et al. 1994; Vasey 2007). However, numbers of infants can range from one per birth up to five (Weigler et al. 1994; Greeley 1982; Pollock 1986). Birth weight in captivity ranges from 70 to 140 g (.15 to .31 lb), averaging between 83.0 to 101.7g (.18 to .22 lb) (Boskoff 1977; Brockman et al. 1987). At birth, newborns are covered with fur and their eyes are open (Foerg 1982). Before giving birth, a ruffed lemur mother will construct an arboreal nest within her core area, normally between 10 to 25m (32.8 to 82.0 ft) above the ground, out of branches, leaves and other foliage (Morland 1990; Vasey 1997a; 2007). Such nests are shallow and dish-shaped with only one apparent entry point (Vasey 2007). In captivity, for the first two weeks of life, mothers spend between 70% and 90% of their time in their nests with the newborns (Pereira et al. 1987).

In the wild, the infant remains in the nest until about one to three weeks of life, at which point the mother moves them out for the first time and "stashes" them while she performs other activities (Pereira et al. 1987; Morland 1990; Vasey 2007). Infant "stashing" involves placing the infant or infants in concealing foliage in the canopy and leaving them there for up to several hours at a time while she forages elsewhere, sometimes out of earshot (Morland 1990; Vasey 2007; see Vasey 1997a:42-3 for discussion of the term "stashing"). Transport of infants by the mother occurs singly, with the mother grasping the infant's belly crosswise in her mouth and continues until they are too big to carry, at around 2.5 months old (Morland 1990; Downman 1993; Vasey 2007). While "stashed," infants will rest, sit still, and not vocalize (Pereira et al. 1987; Vasey 2007).

Often, while the mother is away from her offspring, other group members will guard them in addition to emitting alarm calls when sensing danger, responding to the alarm calls of others and providing care for the infants. Males provide a lot of infant care as well; guarding, huddling, grooming and playing with the offspring of up to several different mothers (Vasey 2007). In captivity, females related to a mother have been observed nursing her offspring and close kin have served as foster parents for infants rejected by their mother (Pereira et al. 1987; Kerridge 1999). Indeed, alloparenting is widespread in wild ruffed lemur populations, with all members of the community participating in the raising of offspring (Vasey 2007). In the wild and in captivity, community members take part in "coordinated vigilance displays" in which a community member guarding or near to an infant will alarm call if leaving the infant alone or encountering a predator. Upon hearing the alarm call, other community members will alarm call as well, resulting in the communal transmission of the alarm call throughout the forest and potentially summoning the mother back to her "stashed" offspring (Pereira et al. 1987; Vasey 2007).

At one month of age, wild infants will begin climbing and clinging. By two to three months old, the infants will start following their mother and group members for up to 50 to 100m (164.0 to 328.1 ft) and adult mobility and behavior including traveling full-time with adults is attained at 3-4 months old (Morland 1990; Vasey 2007). In captivity, 75-80% of play in the first three months of life is with the mother (Downman 1993). By 10 weeks old, infants begin participating in greeting displays and calling begins at about 16 weeks old (Vasey 2007). Scent marking commences at six months old (Vasey 2007). Also, at around 4 months old in captivity, the infant weighs about 70% of the weight of the adults (Pereira et al. 1987). The wild infant will first sample, but not necessarily ingest, solid foods at around two months old. Wild weaning is estimated to occur at around 4 months of age but some individuals have nursed as late as 7-8 months old (Morland 1990; Vasey 2007).

Infant mortality in the wild shows great variance, and can range from a quite high 64%, possibly due to falls from arboreal nests, to zero mortality over a birth season (Morland 1990; Vasey 2007).

COMMUNICATION

Wild ruffed lemurs are extremely noisy and can be heard from about a kilometer away (Morland 1991a). Captive ruffed lemurs have three rough classes of vocalizations, high-, medium- and low-amplitude calls. High-amplitude calls include the contagious "roar/shriek chorus" which probably functions in inter-group spacing and communication as well as social functions and is communally participated in by all wild group members including 3-4 month old infants (Pereira et al. 1988; Morland 1991a; Geissmann & Mutschler 2006). "Roar/shriek choruses" can occur throughout the day but are concentrated during periods of high activity (Morland 1991a; Geissmann & Mutschler 2006). Other calls of this time are "abrupt roars" which might function to alert group members to avian predators, to communicate between group members out of visual contact and also probably to communicate a more general aggressive/defensive response to a disturbance, and "pulsed squawks" which primarily alerts group members to mammalian predators, shows high arousal and is a signal for the group to quickly aggregate (Pereira et al. 1988; Macedonia 1990; Morland 1991a). In the wild, "roar/shriek choruses" and "abrupt roars" are emitted more often during the hot seasons than during the rest of the year (Morland 1991a). Other high-amplitude calls are the "wail," which functions to bring the group back together or signal all-clear, and the "bray" and "quack," which serve possible mating functions as a male display (Pereira et al. 1988; Morland 1991a). Loud calls are delivered with the lemur's body in a "taut" posture (Vasey 2003).

Moderate-amplitude calls are the "growl" which alerts the group to a mild disturbance or to the approach of an individual, the "growl-snort" which alerts the group, "chatter" which signals subordinate status, and the "whine" which signals appeasement by males in the mating season or submission (Pereira et al. 1988; Morland 1991a). Low-amplitude calls are the "grunt," signaling mild annoyance, the "huff," signaling intense aggravation, especially when avian predators are present, and the "mew," often exchanged between mother and offspring when separated or during adults during travel (Pereira et al. 1988; Morland 1991a). Other wild vocalizations are the "cough," which signals aggression between a female and a male during mating and birth seasons, the "grumble" which advertises the presence of a male to another, the "squeak" which infants use to signal distress, and the "squeal" of affiliation between females (Morland 1991a).

In the wild and in captivity, scent-marking is also an important means of communication to the ruffed lemur and likely communicates information about sex, location and identity (Morland 1991a). Female ruffed lemurs predominantly use their ano-genital scent glands to mark while males use chest, neck, and mandible glands (Pereira et al. 1988; Vasey 2003). Females mark by squatting and rubbing their ano-genital region over a horizontal surface excepting the ground. Males mark by rubbing their chest, chin, and neck on a horizontal or vertical surface including the ground. Both sexes occasionally mark in the characteristic fashion of the opposite sex (Pereira et al. 1988; Morland 1991a). Scent-marking also plays a role in greeting displays, in which individuals "leapfrog" over one another and scent-mark the back of the other individual (Vasey 2007).

Content last modified: August 17, 2007

Written by Kurt Gron.

Cite this page as:
Gron KJ. 2007 August 17. Primate Factsheets: Ruffed lemur (Varecia) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/ruffed_lemur/behav>. Accessed 2013 May 19.