Primate Info Net Banner Wisconsin PRC Logo

Guereza
Colobus guereza

SOCIAL ORGANIZATION AND BEHAVIOR

Guereza social groups are generally small and cohesive, generally ranging between 3 to 15 individuals with most groups at most study sites averaging within that range (Marler 1972; Oates 1977b; see von Hippel 1996 and Oates 1994 for reviews and Krüger et al. 1998 as an example). Groups of up to 23 have been studied and group sizes of up to 30-40 individuals are reported in the southern gallery forests of the Central African Republic, but even if the largest numbers are correct, groups this size are not typical of the species (Rose 1977; Fay 1985; von Hippel 1996; Fashing 2001a). Finally, group sizes tend to be larger in contiguous forest and smaller in riparian or smaller areas of forest (Oates 1977b; von Hippel 1996).

Colobus guereza occidentalis
C. guereza occidentalis
Photo: Alain Houle

The usual composition of guereza groups includes one adult male (although several can be present as group size grows and in several populations, multimale groups are common), several adult females, and immature individuals (Oates 1977b; 1977c; Dunbar 1987; Oates 1994; von Hippel 1996; Oates et al. 2000; Fashing 2001c). The society appears to be matrilineally organized with females and immature individuals forming the closely bonded core of the group (Bocian 1997). Within multi-male groups, one male is dominant to the others and interactions between the adult males are aggressive, with some males eventually being forced out (Bocian 1997; Oates et al. 2000). When not a member of a group, males are seen either alone, or with other non-group males (pers. obs. cited in Fashing 2001c; Harris et al. 2009). Multi-male groups are unstable and often relapse into a single-male structure however it is unclear whether or not group size is limited by social constraints, environmental constraints, or some other factor (Dunbar & Dunbar 1976; Oates 1994; Chapman & Pavelka 2005). Group structure follows this general pattern throughout the guereza range (Oates 1994). In captivity, females do not exhibit a hierarchy of rank, but in the wild, some adult females have dominance relationships (Grunau & Kuester 2001; Harris 2005).

Guerezas are not strictly territorial, although some populations participate in core area defense, especially during encounters with other groups that are usually aggressive in nature (von Hippel 1996; Harris 2006a; Fashing 2007). Adult males are significantly more active in inter-group encounters than females, although females do sometimes participate (von Hippel 1996; Fashing 2001c; Harris 2005; 2006b). Inter-group encounters function in mate defense and resource defense and often consist of chasing, increased activity, displays, vocalization but only rarely physical attacks (von Hippel 1996; Fashing 2001c; Harris 2005; 2006a). In addition, in at least one study, nearby guereza groups could be hierarchically ranked relative to one another, based on the outcome of encounters between themselves (Harris 2006b). While the group is resting, the male will often rest higher and away from the group, possibly to detect other groups and raptors (Oates 1977c).

During group movements, the members of a guereza group stay near one another and follow a leading animal, often in single file and along a similar path, often changing leaders during each progression (Dunbar & Dunbar 1976; Oates 1977a; Fashing 1999)

Within the guereza group, the majority of interactions are friendly and not agonistic, with allogrooming the main affinitive social behavior, especially between females (Oates 1977c; Bocian 1997; Grimes 2000; Harris 2005). Adult males rarely groom others within the group (Oates 1977c; unpub. data cited in Fashing 2007). When agonistic encounters within a group do occur, captive research shows that affiliative behavior occurs soon thereafter between former opponents, consisting of close proximity, grooming, embracing, mouth-opening, and hand touching (Björnsdotter et al. 2000). Captive data shows that facial expressions, vocalizations, and gestures/body positions in female guerezas do not signal dominance or subordination (Grunau & Kuester 2001).

Female guerezas (at least in Kibale National Park, Uganda) do not typically disperse from their natal groups, although they may disperse when groups dissolve (Bocian 1997; Harris et al. 2009). One voluntary female dispersal event has also been recorded (Fashing 2007). In Kibale National Park, females may remain in their groups as adults even though their groups do not contain unrelated mates (due to long male tenure length) (Harris et al. 2009). Adult females within groups are often closely related but this is not true for all groups. Close adult female relatives may also occur among neighboring groups even though females are typically philopatric (Harris et al. 2009). Males typically disperse as subadults or adults. They may become solitary or join bachelor groups; they may immigrate into other groups by joining on the periphery or staging takeovers; and they may also disperse secondarily (Marler 1972; Dunbar & Dunbar 1974; Oates 1974; Harris et al. 2009). Males that take over groups often have tenure lengths reaching five years or more (Harris et al. 2009). Some multi-male groups may consist of father-son pairs, but others apparently contain unrelated males (Harris et al. 2009). In Kibale National Park, Uganda, close adult male relatives sometimes occur among neighboring groups, but overall low levels of among-group adult male relatedness suggest that males often disperse beyond their neighbors (Harris et al. 2009).

It is uncertain as to whether or not females disperse from their natal groups as it has never been observed but they might transfer, particularly during disruptions in the composition of the group (Bocian 1997; pers. obs. cited in Fashing 2001c; Harris 2005). Dispersal is probably more common among males in guerezas than in females (unpub. data cited in Fashing 2007).

REPRODUCTION

Colobus guereza
Photo: Bertrand Deputte

Little is known about reproduction in the guereza (Harris & Monfort 2006). The species exhibits a harem-based, polygynous mating system and there is no strong seasonality of births (Oates 1974 cited in Oates 1994; Bocian 1997). About half of copulations are solicited by males and half by females (Harris & Monfort 2006). Solicitation behavior includes approaching the prospective partner and performing low-intensity mouth clicking or tongue-smacking (Hollihn 1973; Grimes 2000). To present, a female stands with her hindquarters facing a male with her arms bent, holding the body low without the tail raised. The copulation posture consists of the male grasping the female's ankles and trunk from behind (Oates 1977c). Copulations usually occur within a group, but extra-group copulations have been observed in some populations (Fashing 2001c; Harris 2005). In addition, within multi-male groups, sometimes more than one male has mating access to females (von Hippel 1996).

The ovarian cycle is around 24 days, with females receptive about 5 days before ovulation until 2-3 days after ovulation (Harris & Monfort 2006). Females exhibit no external signs of estrus (Oates 1994; Bocian 1997).

Gestation length in wild individuals is around 158 days (5.2 mo) (estimated at 170 days (5.6 mo) in captivity) and the interbirth interval is around 22 months with a minimum of 16 months between births (Dunbar & Dunbar 1974; Rowell & Richards 1979; Harris & Monfort 2006). Birthrates are higher in habitats that are more forested (Dunbar 1987). Age at sexual maturity has been estimated at around 4 years old (48 months) in females and 6 years (72 months) in males (Oates 1977c).

PARENTAL CARE

At birth, guereza infants have white hair and pink to red skin in stark contrast with the black-and-white adults (Wooldridge 1971; Horwich & Manski 1975; Oates 1977c; Ackerman 1991). By three weeks old the face and ears start to darken and become grey (Oates 1977c). The natal coat and skin continue to darken and reach adult coloration around 3-4 months old with males attaining adult coloration faster than females (Oates 1977c; 1994; Ackerman 1991). Some grey coloration can persist above the ears on top of the head through 6-7 months after birth (Ackerman 1991).

In captivity, six main behaviors are shown by females to infants, most frequently between birth and 4 weeks of age. These include the "kiss," "two handed grasp," "tail pull-up," "urogenital licking," "leg pull out," and grooming (Horwich and Manski 1975). At birth in the wild, the infant is dependent on the mother, clinging to her during group movements. In the first 5 weeks of life in captivity, infant guerezas can't control who is carrying them as they are not very mobile. After this age, they often choose their mothers and start actively returning to the mother at around 3 or 4 weeks old (Woolridge 1971; Horwich & Manski 1975). Infant guerezas will repetitively perform new motor skills once learned, often over and over for 15-20 minutes (Wolldridge 1971). Around 8-9 weeks old, the infant will start to eat vegetation, but in small quantities. Social play with other infant is also seen around this age. From the 14th to 17th week, the infant often plays, investigates, feeds, and moves on its own, but still clings to the mother during group movement. At 20 weeks, some movement independent of the mother occurs during group progressions. By 50 weeks old, the juvenile no longer clings to the mother and does not suckle anymore (Oates 1977c).

In the wild and in captivity, infants are the focus of the attention of other members of the guereza group, especially females, and are often handled by these individuals, sometimes shortly after birth (Wooldridge 1971; Oates 1977c). This handling occurs for the first four months of the infant's life but is curtailed thereafter, except for grooming. Such handling occurs most frequently in the first two weeks of the infant's life and infants are often uncomfortable at being held by individuals other than their mothers (Oates 1977c). However, the mother allows others to take and handle the infant. In fact, in captive animals, more care may be given early in the infant's life by non-mothers however this pattern does not necessarily follow in the wild (Horwich & Manski 1975; Oates 1977c). In captivity, males will play and groom only when with infants and their interest in the infant appears keyed toward their defense (Horwich & Manski 1975; Ackerman 1991). However, males are generally disinterested in infants at birth, only increasing their interest after the infant is 4-5 weeks old (Horwich & Manski 1975).

Infants are always carried by the mother ventrally, with the infant grasping the mother's fur (Woolridge 1971).

In the wild, infant mortality in a small sample exceeded one third of infants dying before their pelage changed while after the color change, mortality was low (Dunbar & Dunbar 1974). High infant mortality is observed elsewhere in the wild as well (Oates 1977b). Infanticide has been observed in guerezas, usually committed by non-group or newly immigrated males (Onderdonk 2000; Harris & Monfort 2003).

COMMUNICATION

Guereza vocalizations and sounds can be roughly assigned to six basic categories "roaring," "snorting," "purring," "cawing," "squeaking and screaming," and "tongue clicking" (Marler 1972; Oates 1977c). Perhaps the most frequent, characteristic, and studied vocalization of the guereza is high-intensity "roaring" bouts, which occur mainly during the night and at dawn, but can also occur during the day and at lower intensities when potential predators are nearby or during heightened arousal (Marler 1972; Oates 1974 cited in Oates 1977c; Oates 1977c; Bocian 1997; Fashing 1999; Oates et al. 2000). Roaring can be heard up to a mile (1.6 km) away and usually only one adult male per group will roar, even in multi-male groups (Marler 1972; Bocian 1997; Harris 2005). Roaring is contagious and functions in long-range communication; once an individual adult male starts roaring, other males in neighboring groups will also begin roaring, each calling from a different location (Marler 1972; Bocian 1997; Fashing 1999; Oates et al. 2000). Night roaring is spontaneous and most roaring is not associated with the nearby presence of other guereza groups (Oates 1977c). Variation in roaring among males can be explained by the ranking of their group relative to others and might also signal their fighting ability (Harris 2005; 2006b). Male roars have been shown to contain both honest and exaggerated information about body size (Harris et al. 2006).

Colobus guereza
Photo: Tara Harris

"Snorting" is heard from all wild males in a group and sometimes from females in captivity. This type of vocalization can be uttered in response to potential predators, when approaching another animal before aggression, and is a potential alarm call (Marler 1972). "Purring" is heard prior to group movements and functions to help coordinate the group but also may be a low intensity alarm call (Marler 1972; Oates 1977c). "Cawing" is usually heard from females and infants, and occurs in situations of light distress. "Squeaks and screaming," like "cawing" is heard from females and sub-adults. This vocalization is usually heard in times of strong distress, especially when infants feel threatened (Marler 1972). "Tongue-clicking," while is used as an indicator of mild aggression, in both inter- and intra-group interactions. Its main function is likely as a threat (Marler 1972).

LISTEN TO VOCALIZATIONS

Seven facial expressions used in communication have been described in addition to ten body postures and movements, and six types of tactile communication (see Oates 1977c). Two of the most conspicuous displays performed by guereza adult males include flashy leaps during roaring, and "stiff legs," often accompanying tongue clicking when two guereza groups meet (Oates 1977c).

Content last modified: May 12, 2009

Written by Kurt Gron. Reviewed by Peter Fashing and Tara Harris.

Cite this page as:
Gron KJ. 2009 May 12. Primate Factsheets: Guereza (Colobus guereza) Behavior . <http://pin.primate.wisc.edu/factsheets/entry/guereza/behav>. Accessed 2014 September 1.