Sun-tailed Monkey (Cercopithecus solatus)
This species has cheek pouches to carry food in while it forages. The dental formula of the sun-tailed monkey is 2:1:2:3 on both the upper and lower jaws (Ankel-Simons, 2000). The sun-tailed monkey is colored dark gray to black, having a white ruff and a chestnut-orange saddle (Harrison, 1988). The tip of the tail is colored yellow-orange with the rest colored whitish on the ventral side and speckled gray dorsally (Harrison, 1988; Groves, 2001). Males have a powder-blue colored scrotum (Harrison, 1988). Infants are born with hair that is orange streaked black and skin with little pigmentation (Orbell et al., 1991). At seven weeks the skin of the infant begins to darken (Orbell et al., 1991). At eleven weeks the infant begins to develop adult coloration, with darkening hair and black skin (Orbell et al., 1991). The tip of the tail is yellow-orange by eleven weeks also (Orbell et al., 1991). Adult females have an average body mass of about 3.9 kilograms (Gautier et al., 1992). Adult males have an average body mass of 6.9 kilograms (Fleagle, 1999).
The sun-tailed monkey is endemic to the country of Gabon. This species is found in central Gabon in the Foret des Abeilles (Forest of the bees) and in Lope Reserve (White, 1995; Harrison, 1988; Blom et al., 1992; Brugiere et al., 1998). The sun-tailed monkey lives in areas of dense vegetation, such as narrow valleys (Brugiere et al., 1998). This species will use logged areas of the forest probably because of the dense secondary vegetation, which is good for the cryptic nature of this species and herbaceous plants and insects are found in greater abundance (Brugiere and Gautier, 1999).
The sun-tailed monkey is a frugivorous species. Peignot et al. (1999) found that in a semi-free ranging group, insects and grasses were the most preferred food items eaten, while fruit was only the third preferred food item. Gautier (1998) found that the diet of the sun-tailed monkey was composed of fruits, seeds, herbaceous plants, insects, and small vertebrate prey. Gautier et al. (1986) found that foraging mainly occurs on the ground.
This is a diurnal and a terrestrial species, but does go into the forest for some activities. Terrestriality may result from long daily travel, large home range size, and diet (Gautier, 1998). Mean group size for this species is 17 individuals (Gautier, 1998; Brugiere et al., 2002). Peignot et al. (1999) found that moving and playing occurs mainly from ground level up to 2 meters, resting and grooming occurs at 4 meters and above, and foraging occurs throughout all levels of the forest, but most frequently at above 2 meters. Resting and grooming may occur at higher levels because individuals are less attentive to potential predators when engaging in these activities (Peignot et al., 1999). Groups will sleep in the canopy, 10 to 15 meters above the ground (Peignot et al., 1999).
The sun-tailed monkey is hunted by humans, Homo sapiens, who hunt them with snares and shotguns (Gautier and Brugiere, 1996; Gautier, 1989). When this species is alarmed, it will flee to the ground (Gautier et al., 1986).
The sun-tailed monkey moves along the ground quadrupedally (Fleagle, 1988). When this species leaps from tree to tree, the body is held in a vertical position like the prosimians (Peignot et al., 1999). This may occur because the supports used to be vertical trunks in the lower levels of the forest (Peignot et al., 1999). The sun-tailed monkey will also move by bipedal walking on the ground in grassy areas possibly to see and to avoid any potential predators (Peignot et al., 1999).
The sun-tailed monkey has a unimale social system with a polygynous mating system (Peignot et al., 1999, 1996). Solitary males are known to occur (Gautier, 1998; Peignot et al., 2002; Brugiere et al., 1998). Adult males will actively defend their groups from other males trying to usurp them (Peignot et al., 1996, 2002). The males disperse from their natal groups in this species (Peignot et al., 2002). A dominance hierarchy exists amongst females in a group, and young males are generally submissive to the adult male of the group (Peignot et al., 2002). Off spring will inherit their mother's social position (Peignot et al., 2002). This species avoids polyspecific associations (Gautier, 1998).
Social play of this species includes: chasing, tag, open-mouthed wrestling, and rough-and-tumble (Peignot et al., 1999). Social play mainly occurs amongst juvenile and adolescent males (Peignot et al., 1999).
Due to its cryptic nature, the sun-tailed monkey lacks a loud long distance call and high-pitched contact calls (Gautier, 1988; Peignot et al., 2002).
warning bark: This call is uttered by the adult male (Gautier et al., 1986).
staring: This display by the sun-tailed monkey is used as a threat display (Estes, 1991). The eyes are fixed on the stimulus and the eyebrows are raised and the scalp is retracted, the facial skin is also stretched by moving the ears back (Estes, 1991). Underneath the eye lids the color is different which contrasts sharply with the surrounding facial color (Estes, 1991)
staring with open mouth: This is the stare accompanied by the mouth being open but the teeth are covered (Estes, 1991). This is a threat expression and often occurs with head-bobbing (Estes, 1991).
head-bobbing: This is used as a threat display by the sun-tailed monkey and head bobs up and down (Estes, 1991). This often occurs with staring with open mouth (Estes, 1991).
fear grimace: The lips are retracted so that the teeth are shown; the teeth are clenched together (Estes, 1991). This display functions as an appeasement signal to reduce aggression in aggressive encounters (Estes, 1991).
yawning: This is where the mouth is opened to reveal the canines, and is performed by the adult male (Estes, 1991). This is used as an expression of tension or as a threat display (Estes, 1991).
social grooming: This is when one individual will groom another, removing dead skin and parasites.
The sun-tailed monkey gives birth to a single offspring. Females are the ones who solicit copulation from the male (Estes, 1991). The age of first reproduction for females is about 4 years old (Peignot et al., 1999). The interbirth interval for this species is about 18 months (Peignot et al., 1999). In captivity a sex bias in births was found where males are born more frequently than females (Peignot et al., 1996).
presenting: This behavior is preformed by the female to elicit copulation from the male; this pattern tells the male that she is ready for copulation (Estes, 1991).
pouting: Females do this during copulation while looking over their shoulder at the male (Estes, 1991). The lower lip is extruded forward while the lips remain closed (Estes, 1991).
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Peignot, P., Fontaine, B., and Wickings, E.J. 1999. Habitat exploitation, diet and some data on reproductive behaviour in a semi-free-ranging colony of Cercopithecus lhoesti solatus, a guenon species recently discovered in Gabon. Folia Primatologica. Vol. 70, 29-36.
Peignot, P., Fontaine, B., and Wickings, E.J. 2002. A preliminary study on the social relationships in a semi-free ranging colony of sun-tailed monkeys (Cercopithecus solatus), a species recently discovered in Gabon. Primates. Vol. 43(2), 139-146.
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Last Updated: January 1, 2004.
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