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 19 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). Finally, group sizes tend to be larger
in contiguous forest and smaller in riparian or smaller areas of forest (Oates
1977b; von Hippel 1996).
Photo: Kim Bauers
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). 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
(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 (Grunau & Kuester 2001).
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; 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). 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).
C. guereza occidentalis
Photo: Alain Houle
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
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 18 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).
Photo: Bertrand Deputte
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).
"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).
Content last modified: December 17, 2007
Written by Kurt Gron.
Cite this page as:
Gron KJ. 2007 December 17. Primate Factsheets: Guereza (Colobus guereza) Behavior. <http://pin.primate.wisc.edu/factsheets/entry/guereza/behav>. Accessed 2008 May 11.
