Lesser bushbaby
Galago

SOCIAL ORGANIZATION AND BEHAVIOR

The social fabric of the lives of bushbabies is as varied as their habitats and for many species, incompletely known. However, the social systems of the bushbabies are best described as non-gregarious (Pullen et al. 2000). For example, G. moholi spends 70% of its activity period solitary (Bearder & Doyle 1974b; Doyle & Bearder 1977). This is not a rule however, with some populations of G. alleni being found about half of the time in association with one or several conspecifics while other populations of the same species do not show this pattern (Ambrose 2003).

The lives of bushbabies are typified by a dichotomy of daily activity; divided between solitary evening and nighttime activities alternating with morning and daytime social aggregation, especially at the sleeping site (Charles-Dominique 1972; Bearder & Martin 1980; Harcourt & Nash 1986). Individuals are not often seen together at night (Harcourt & Nash 1986). Because some of the activity period is spent solitary, social groupings are perhaps best quantified through sleeping group size, which can vary between solitary sleeping up to ten individuals per sleeping site (data compiled from the literature by Bearder 1987 & Bearder et al. 2003). Only G. demidoff does not sometimes sleep alone and has a minimum sleeping group size of two individuals (Bearder et al. 2003). Home ranges in G. zanzibaricus males show only slight overlap, as is mostly the case in females of comparable age; however females sometimes share ranges with other females who are likely kin (Nash 1984; Harcourt & Nash 1986). Males will sleep with each individual whose range overlaps his, mostly one or several adult females and immatures per night (Harcourt & Nash 1986). Adult male G. moholi never sleep together (Bearder & Martin 1980). The overlap in male ranges might be explained by low sample size, tolerance of smaller emigrating males, or the process of replacement of a resident male. Adults of G. zanzibaricus likely defend their ranges (Harcourt & Nash 1986). G. moholi females range structure is related to their age, with like-aged females showing little range overlap while those with somewhat larger age differences may overlap extensively (Bearder & Martin 1980). In both G. alleni and G. demidovii, female ranges vary in their overlap with one another and the ranges of males usually overlap at least one female range. G. alleni male home ranges are vast and may overlap the home ranges of more than 8 different females. Male ranges either do not overlap or overlap to an insignificant degree. Small areas of male overlap are sometimes deemed common areas, and may be shared by several males in G. demidovii and G. alleni (Charles-Dominique 1977a).

In G. moholi, males exhibit a linear, age-based dominance hierarchy, with only the highest ranking males defending their territories. Such individuals are usually some of the largest present in a given area and initiate agonistic contact, often resulting in the displacement of subordinate males. Regardless of rank, adult males are not tolerant of one another (Bearder & Martin 1980). There are two classes of mature G. moholi males, dominant heavier males who interact with females more often and submissive, nonterritorial adult males who weigh less and interact with females less (Bearder 1987). It is suggested that there are four classes of adult male in G. demidovii, each with particularities of home range extent and overlap relating to contacts with both female home ranges as well as with other adult males (Charles-Dominique 1977a). To show submission, individuals descend to ground-level (Bearder & Doyle 1974b; Bearder & Martin 1980). Adult male G. alleni are extremely intolerant of one another and are in pronounced competition with other males (Charles-Dominique 1977).

Female G. moholi exhibit more ambiguous social relationships, although agonistic territorial behavior is sometimes seen at the borders of home ranges (Bearder & Martin 1980). Affiliative interactions in G. senegalensis consist of urine-washing, grappling, chasing, play and grooming (Bearder & Doyle 1974b).

Females in G. zanzibaricus tend not to emigrate from their natal range while males do, usually at puberty (Nash 1984; Harcourt & Nash 1986). In some species, young pubescent males may spend time in a so-called "vagabond" phase of life, in which they are nomadic and do not spend much time in a given area (Charles-Dominique 1977a). Emigration in G. moholi is rigidly defined, with the pre-reproductive pubescent male traveling either unidirectionally either east or west over several nights, ending up several kilometers from the natal range (Bearder 1987).

In captivity, aggression is most common between members of the same sex while affinitive behaviors are mostly seen between the sexes in G. senegalensis (Nash & Flinn 1978). In the wild, confrontations are usually avoided, but rare violence can result in serious injury and/or the displacement of a formerly dominant male by a vagabond male (Charles-Dominique 1977a).

When G. moholi encounters a conspecific they will greet each other with nose-to-nose contact and smelling, which may be followed by grooming or agonistic behavior, especially when the individuals are unfamiliar with one another (Doyle 1974).

REPRODUCTION

The mating system of bushbabies (G. moholi) is best described as dispersed and not strictly polygynous. Certain males have a better chance of mating success than others but females may still mate with more than one male (Pullen et al. 2000). Female bushbabies exhibit estrus swelling of the sex skin and the vagina is closed at all other times other than estrus (Nash 1983; Zimmermann 1989; Lipschitz et al. 2001). Estrus and the mating period lasts 1-3 days with some evidence from the wild suggesting that females do not all come into estrus at the same time (Gucwinska & Gucwinski 1968; Doyle et al. 1971; Pullen et al. 2000). G. moholi copulations in the wild last, on average, 9 minutes, but can range from 2 to 53 minutes. Copulation is often serial, with 2-5 prolonged mounts punctuated with rest and grooming (Pullen et al. 2000). Copulations between captive G. senegalensis are similarly prolonged (LT Nash, per. comm.).

In both the wild and captivity, females may mate with more than one male during a single estrus (Gucwinska & Gucwinski 1968; Pullen et al. 2000). In G. moholi, larger males have better mating success (Pullen et al. 2000). The copulation posture of bushbabies is dorso-ventral, with the male grasping the heels of the female from behind (Charles-Dominique 1977a; Lipschitz 1996b). G. demidovii copulates while suspended from a branch, while other species do not practice suspensory copulation (Charles-Dominique 1977a). The typical mating sequence in captivity of G. moholi consists of the male approaching the female, chasing her, grabbing her and mounting (Lipschitz 1996a). Nose-to-nose touching and genital sniffing may also precede copulation (Lipschitz 1996b). In the wild, all matings in this species are initiated by very persistent males and females are generally averse to their mating attempts (Pullen et al. 2000). In captivity however, females sometimes approach present her hindquarters to a male during behavioral estrus (Lipschitz 1996b).

Several species of bushbaby have two mating and birth seasons per year in the wild, including G. senegalensis, G. zanzibaricus and G. moholi, while other bushbabies of comparable size (G. gallarum) likely follow this pattern as well (Haddow & Ellice 1964; Butler 1967; Harcourt 1986a; Pullen et al. 2000; Butynski & de Jong 2004). Individual females in some species are capable of breeding twice in the same year (Harcourt 1986a; Bearder et al. 2003). Just prior to and during mating seasons, the weight of males and the volume of their testes increases (Pullen et al. 2000).

Among the bushbabies, gestation lengths can range from around 111 days to around 142 with smaller species generally having shorter gestation lengths (Gucwinska & Gucwinski 1968; Doyle et al. 1971; Bearder & Doyle 1974a; Charles-Dominique 1977a; Izard & Simons 1986; Lipschitz 1996a; Izard & Nash 1988; Nash et al. 1989; Zimmermann 1989; Nekaris & Bearder 2007). The average ovarian cycle in captive G. moholi is 38.5 days (Lipschitz 1996b). Sexual maturity is reached across bushbaby species with available data between 8 and 18 months of age (Charles-Dominique 1977a; Izard & Nash 1988; Nash 1993; data compiled by Nekaris & Bearder 2007).

Per pregnancy in most bushbaby species, usually one infant is born, with the possibility of twins and extremely rarely, triplets (Butler 1967; Doyle et al. 1971; Riordan 1971; Nash 1983; Harcourt 1986a; Izard & Simons 1986; Nash et al. 1989; Zimmermann 1989; Bearder et al. 2003). There are several species that are exceptions however. One is G. moholi, which has higher rates of twinning than most other bushbabies (Izard & Simons 1986; Izard & Nash 1988; Nash et al. 1989; Bearder et al. 2003). Bushbaby mothers can give birth to up to 4 infants per year (G. moholi) (Bearder et al. 2003). Estrus is sometimes seen for several days directly following birth and conceptions are possible during this postpartum estrus (Doyle et al. 1969; Zimmermann 1989; Nash 2003).

PARENTAL CARE

As the birth of the infant nears, G. zanzibaricus females start sleeping on their own and isolate themselves whereas before they sleep with conspecifics (Charles-Dominique 1977a; Harcourt 1986a). Births occur in nests or the hollows of trees (Bearder 1987). Pooled, multi-species data give the birth weight at about 5 to 24 g (0.2 to 0.8 oz) (Gucwinska & Gucwinski 1968; Doyle et al. 1971; Izard & Nash 1988; data compiled by Nekaris & Bearder 2007 and Zimmermann 1989 for older data). The eyes are open at birth and the pelage is ubiquitously grey and meager (Gucwinska & Gucwinski 1968; Charles-Dominique 1977a; Doyle 1979; Zimmermann 1989). Thick fur comes in between two and three weeks old (Charles-Dominique 1977a).

In captivity (G. moholi), at one day old, infants are capable of clinging to a branch and within the first several days of life, can walk quadrupedally. By two weeks of age, infants can quadrupedally run (Doyle 1979). Infants start following their mothers about between 4 and 6 weeks old (Doyle & Bearder 1977). Play begins very early, within the first week of age (Doyle 1979). Among juvenile G. senegalensis, young males play more often than females (Nash 1993).

While the mothers are engaging in other activities, such as foraging nearby, juveniles are parked, usually in tree forks or tangles, motionlessly hiding from potential threats (Doyle 1974; Charles-Dominique 1977a; Harcourt 1986a; Bearder 1987; Ambrose 2003). They sometimes remain parked for prolonged periods of time, up to three hours, but if the parking is prolonged, the mother will occasionally visit (Doyle 1974; Doyle & Bearder 1977). If directly disturbed or seemingly forgotten, the infant may emit a distress call and the mother comes running (Doyle et al. 1969; Charles-Dominique 1977a).

In G. senegalensis, up until 12 weeks of age in captivity, adult-type vocalizations are not heard, with infants instead producing characteristic "zek" calls (Zimmermann 1989). G. moholi infants utter three distinct types of distress vocalization which are given in increasing situations of distress to which the mother responds by coming to the infants and grooming them (Mascagni & Doyle 1993). In situations of danger, the mother will carry the infant away in her mouth (Charles-Dominique 1977a). In captivity, infants first emerge from their nest box at ten to 14 days of age, and in the wild starting between 3 and 7 days of age, the mother carries the infant out of the nest with her and starts parking it (Gucwinska & Gucwinski 1968; Doyle et al. 1969; Charles-Dominique 1977a). In the wild, independent movement and exploration begins about 2-3 weeks old (Charles-Dominique 1977a). Consumption of solid foods commences at one month of age, when infants start stealing food from the mouths of their mothers (Charles-Dominique 1977a). In the wild, juveniles usually forage alone (Bearder 1987).

The typical maternal infant carrying posture is in the mouth, often by the nape (Gucwinska & Gucwinski 1968; Doyle et al. 1969; Ward & Scott 1970; Doyle & Bearder 1977; Doyle 1979; Harcourt 1986a; Ambrose 2003; Bearder 2003; Nash 2003). Carrying with the infant clinging to the fur of the mother is rare, but has been observed in G. gallarum (Butynski & de Jong 2004). In captivity, all sexes and ages are patient with juveniles, and sometimes play, groom, and show interest towards them (Bearder & Doyle 1972). In semi-natural captive conditions, grooming frequencies between mother and offspring do not change as the infant ages, persisting until full adult separation from the mother (Doyle et al. 1969).

In captivity, both G. moholi and G. senegalensis females lactate for an average of around 100 days after the birth of their infant with weaning at 10-14 weeks of age (Doyle 1979; Izard 1987; Zimmermann 1989). However, wild G. demidoff weans its young earlier, at around 45 days old (Charles-Dominique 1977a). Females sometimes nurse infants not belonging to them and there are not profound differences in contact and nursing between sexes of infants (Nash 2003). By ten months of age, males have reached puberty and emigrate and also around this time, courting of females starts (Charles-Dominique 1977a; Bearder 1987). Females in G. moholi start showing territorial behaviors around 200 days old (Bearder 1987).

COMMUNICATION

The vocalizations of bushbabies have been roughly divided into discrete types by function. These include social cohesion and spacing calls (social contact calls), agonistic calls (threat and distress calls), and attention and alarm calls (Charles-Dominique 1977a; Zimmermann et al. 1988). Among G. moholi and G. senegalensis, there appear to be 14 types of call in common between the two species (Zimmermann et al. 1988). However, different species vary in the total numbers of vocalizations they produce. Bushbaby vocalizations are extremely variable, often grading into one another and are produced both during inhalation as well as during exhalation (Bearder et al. 1995).

Because morphological differences are not always useful for differentiation, vocalizations are considered a good way to tell bushbaby species from one another (Ambrose 2003). This is particularly true of advertising calls, which are often unique to species in primates and in bushbabies these types of calls are the most diagnostic (Zimmermann et al. 1988; Zimmermann 1990; 1995). Loud advertisement calls are often profoundly different than those of other bushbabies and are used to tell different species apart (for example Harcourt & Bearder 1989; Butynski et al. 1998; Wickings et al. 1998; Anderson et al. 2000; Perkin et al. 2002; Butynski & de Jong 2004; Ambrose 2006; Butynski et al. 2006). Vocalizations and olfactory marking are likely the best signals functioning in intra-species individual recognition by bushbabies (Ambrose 2003). Vocalizations can be so unique that bushbabies which are not distinguishable otherwise have been suggested as potential subspecies or even full species based mainly on differences in vocal structure (Perkin et al. 2002; Ambrose 2003). It is less likely that species of bushbaby can be be differentiated based on agonistic, attention, and alarm calls (Zimmermann 1990). Advertisement calls are usually heard upon emergence from the sleeping site, reconvening before sleep at the end of the activity period, and for maintaining contact during the night (Bearder et al. 1995). Further, advertisement calls might also be given in calling bouts between members of the same sex (Bearder et al. 1995).

While usually considered non-gregarious, G. moholi emits alarm calls when predators are encountered and the alarm calling is contagious, with other bushbabies joining in and coming together, mobbing and calling for up to 30 minutes around the threat (Bearder et al. 2002).

Call frequency is affected by population density, with some species calling more over the course of the nightly activity period if more conspecifics are nearby (Courtenay & Bearder 1989).

In the wild, urine-washing is a means by which G. alleni may disperse olfactory clues throughout its home range. In this species, the soles of the feet are washed with urine, which is subsequently dispersed, especially in areas of overlap with the home ranges of conspecifics (Charles-Dominique 1977b). Urine-washing may also communicate social clues to other bushbabies (Nash 1993). There are several types of scent-marking observed in captive G. demidoff. These include urine-washing, hand-rubbing, genital-planting, cheek-/chin-rubbing, chest-rubbing, anogenital-rubbing, and substrate-biting combined with flehmen (Pitts 1988). However, urine washing may also enhance grip in some species, e.g. G. moholi (Harcourt 1981).

Displays seen in G. demidoff include defensive displays seen in both sexes, defensive anti-intruder/anti-predator displays, male-male rank demonstration displays, and dominant-female self-advertising displays. Further, it is suggested that the displays given by dominant-males in offensive situations may be species specific and are a useful tool in differentiating species of bushbaby (Pitts 1988). In the wild, aggressive postures consist of the bushbaby extending its body and tail, spreading the ears and opening the mouth (Charles-Dominique 1977a).

Content last modified: December 8, 2008

Written by Kurt Gron. Reviewed by Leanne Nash.

Cite this page as:
Gron KJ. 2008 December 8. Primate Factsheets: Lesser bushbaby (Galago) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/lesser_bushbaby/behav>. Accessed 2013 December 5.