Cercopithecus ascaniusblack-cheeked white-nosed monkey

Geographic Range

Redtail monkeys (Cercopithecus ascanius) are found in Africa from the Central African Republic eastwards through Kenya and south into Angola and Zambia. Populations are most dense in Uganda. (Smuts, et al., 1987)


Redtail monkeys can live in a rather large variety of habitats. They are mainly found in the middle canopy of tropical rain forest habitats. However, they have also been observed in swamp forests, secondary forests, riverine gallery forest, and other woodlands (Smuts et al. 1987). (Smuts, et al., 1987)

Physical Description

This relatively small primate exhibits some sexual dimorphism in weight and body length. Males have an average mass of 4.1 kg and a length of approximately 46 cm. Redtail monkey females, in contrast, average 2.9 kg in mass and about 38 cm in length (Torstar Books 1984; Smuts et al. 1987).

Other than size differences, males and females of this species are very similar. The recognizable markings of adult redtail monkeys include a black face, bluish skin around the eyes, a white spot on the nose, and white cheek fur. The name 'redtail' comes from the chestnut-colored fur on the underside of the tail. The rest of the body is covered with a speckled brown coat and gray or black limbs, depending on the subspecies (Torstar Books 1984).

Redtail monkey infants have woolly gray fur at birth. Although they are born with a visible nose spot, young redtail monkeys have a brown tail and no cheek whiskers. As they mature, their markings begins to resemble those of adults (Kingdon, 1984). (Kingdon, 1984; Smuts, et al., 1987; Torstar Books, 1984)

  • Sexual Dimorphism
  • male larger
  • Range mass
    2 to 6 kg
    4.41 to 13.22 lb
  • Average mass
    males: 4.1 kg; females: 2.9 kg
  • Average length
    males: 46 cm; females 38 cm


Cercopithecus ascanius displays a polygynous-promiscuous mating system (Cords et al., 1984). This type of mating characterizes populations in which one male mates promiscuously with the females of the group. Since females show no outward signs of receptiveness they frequently elicit matings with males from their own group or from wandering male groups through a behavior known as presenting (Estes, 1991). (Estes, 1991)

Redtail monkeys generally breed throughout the year, although the peak season is from November to February (Smuts et al., 1987). The majority of pregnancies produce a single infant.

Although data are lacking for C. ascanius, in general, species in the genus Cercopithecus have gestations ranging in duration from around 5 months to a maximun of 7 months. Newborns typically weigh around 400 g, and are entirely dependent upon the mother for transportation and nourishment (Nowak, 1999). It is reasonable to assume that C. ascanius is similar in these respects to other members of the genus.

Males generally reach sexual maturity at the age of six, females mature at four or five years of age (Smuts et al., 1987). (Smuts, et al., 1987)

  • Breeding interval
    It is likely that females are capable of producing young each year.
  • Breeding season
    Redtail monkeys generally breed throughout the year, although the peak season is from November to February
  • Average number of offspring
  • Average number of offspring
  • Average gestation period
    6 months
  • Average gestation period
    147 days
  • Range age at sexual or reproductive maturity (female)
    4 to 5 years
  • Average age at sexual or reproductive maturity (male)
    6 years

As in most primates, parental care is mainly the responsibility of females. Young are altricial, and must be carried for the first several weeks of life. Mothers provide food (milk) for their young, as well as transportation and grooming.

Female guenons typically have life-long associations with their kin. The dominance rank of a female within her social group will affect the dominance rank of her daughters. (Nowak, 1999; Smuts, et al., 1987)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female
  • post-independence association with parents
  • extended period of juvenile learning
  • maternal position in the dominance hierarchy affects status of young


Although data are not available for this species, other members of the genus Cercopithecus are known to live in captivity for more than 30 years. It is likely that C. ascanius is similar to other members of the genus in lifespan. Lifespan in the wild is likely to be somewhat shorter than it is in captivity. (Nowak, 1999)


This diurnal, arboreal species is quite agile and active. Their main hours of activity are in the early morning and late evening (Kingdon, 1984).

Redtail monkeys tend to be found in medium-sized groups of 11 to 14 individuals containing one male and a matrilineal group of females (Chapman and Chapman, 2000). It is common for several of these troops to congregate together at food resources or in large trees during resting periods (Kingdon, 1984). Groups of redtail monkeys travel approximately 1.4 km each day in search of food.

Allomothering, the sharing of maternal care by other females of the group other than the infant's mother, has also been observed in redtail monkey groups, although occasionally the infant is harmed in a fight for possession of the youth (Struhsaker and Leland, 1979).

Cercopithecus ascanius males, upon reaching sexual maturity, disperse from the home range and displace other males in different groups or join all-male wandering bands (Cords 1984). After displacement of the tenured male, it is common for the incumbent male to kill all existing offspring in the group, thereby making lactating females come into estrous sooner and bear his offspring (Struhsaker, 1977). (Chapman and Chapman, Aug 2000; Cords, 1984; Kingdon, 1984; Smuts, et al., 1987; Struhsaker and Leland, 1979; Struhsaker, 1977)

  • Average territory size
    12,000 m^2

Home Range

Groups defend their home ranges of about 120 hectares primarily through visual threats and, if necessary, physical combat (Smuts et al., 1987). (Smuts, et al., 1987)

Communication and Perception

As in all primates, communication in this species is complex, and includes chemical, visual, auditory, and tactile components. The visual communication system consists of eyebrow raising, facial skin stretching, and head-bobbing (Estes, 1991). These signals are commonly used to warn potential predators or unwanted intruders. Vocal communication consists of birdlike chirps between members of a group (Kingdon, 1984). This form of communication is mainly used socially among members of the same unit. These associated individuals may also identify one another by nose-to-nose greeting, in which two individuals press their muzzles together. After this greeting they will commonly practice reciprocal social grooming or play (Estes, 1991). (Estes, 1991; Kingdon, 1984)

Food Habits

Redtail monkeys are primarily frugivorous, but supplement their diet with leaves, insects, flowers, buds, and gum (Torstar Books, 1984; Chapman and Chapman, 2000).

It is common for adults to store fruit in their large cheek pouches in order to take their meal to an area free from the threat of theft by other monkeys (Torstar Books, 1984). (Chapman and Chapman, Aug 2000; Torstar Books, 1984)

  • Animal Foods
  • insects
  • Plant Foods
  • leaves
  • fruit
  • flowers
  • sap or other plant fluids


Cercopithecus ascanius is potential prey for chimpanzees, crowned hawk-eagles, wild cats, and humans (Kingdon, 1984; Leland and Struhsaker, 1993). It is also likely that these monkeys fall victim to the same predators that trouble other small, arboreal primates in African forests. These include leopards, snakes, and a variety of avian predators. (Nowak, 1999)

Ecosystem Roles

Because these monkeys are frugivorous, and can transport fruits in their cheek pouches, it is likely that they play some role in seed dispersal. In addition, as a prey species, they probably have some effect on predator populations. (Nowak, 1999)

  • Ecosystem Impact
  • disperses seeds

Economic Importance for Humans: Positive

Redtail monkeys have been instrumental in the regeneration of Strychnos mitis, a tree species found in the Kibale Forest. Redtail monkeys feed heavily on the fruit of this tree. As they eat the fruit, they spit the intact seeds, which fall to the rainforest floor where the seeds can successfully germinate. This method of seed sowing produces more saplings annually than the fruit would normally produce without the help of redtail monkeys (Lambert 1995).

Redtail monkeys have also been useful as laboratory animals in studies on various viral diseases (Kingdon 1984).

Economic Importance for Humans: Negative

Cercopithecus ascanius regularly practices crop raiding of nearby agricultural gardens containing maize, banana, millet, bean, pumpkin, pineapple, or passion fruit crops (Kingdon, 1984). In regions of low productivity this behavior has become a serious problem for neighboring human villages.

Redtail monkeys are also one of the major carriers of yellow fever in Africa (Kingdon, 1984). When the monkeys venture into human villages to raid their crops, there is a greater chance that an infected individual could spread this disease to the villagers. (Kingdon, 1984)

Conservation Status

Although redtail monkey populations are currently healthy, there is some concern about their future status. As is the case with many rainforest dwelling animals, the threat of habitat loss by deforestation is a major concern. Since C. ascanius inhabits a relatively small area on the African continent, loss of habitat could be detrimental for the future of this primate species.

Redtail monkeys are also threatened by predation. They are potential prey for chimpanzees, crowned hawk-eagles, wild cats, and humans (Kingdon, 1984; Leland and Struhsaker, 1993).

Redtail monkey populations are depleted by distraught farmers that view them as pests and shoot them on sight (Leland and Struhsaker, 1993). (Kingdon, 1984; Leland and Struhsaker, 1993)

Other Comments

Redtail monkeys are commonly found in close association with other primate species, such as red colobus, mangabeys, and blue monkeys. Redtail monkeys form an important feeding association with colobus monkeys. Colobus monkeys bite through the tough outer skins of Mondura fruits and redtail monkeys are able to eat the fruit scraps that contain ordinarily unobtainable fruit pulp (Leland and Struhsaker, 1993). They have also been observed to interact socially with other species; playing, grooming, and helping in defense from common predators.

Redtail monkeys have been observed to mate with blue monkeys, and produce fertile offspring (Leland and Struhsaker, 1993). (Leland and Struhsaker, 1993)


Nancy Shefferly (editor), Animal Diversity Web.

Sarah Davis (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.



living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map


uses sound to communicate


young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.


Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

causes disease in humans

an animal which directly causes disease in humans. For example, diseases caused by infection of filarial nematodes (elephantiasis and river blindness).


uses smells or other chemicals to communicate

  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates


animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.


union of egg and spermatozoan


forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.


an animal that mainly eats fruit


An animal that eats mainly plants or parts of plants.


offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).


having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


having more than one female as a mate at one time


rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


associates with others of its species; forms social groups.


uses touch to communicate


Living on the ground.


defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement


the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.


uses sight to communicate


reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year


Chapman, C., L. Chapman. Aug 2000. Constraints on Group Size in Red Colobus and Red-tailed guenons:Examining the Generality of the Ecological Constraints Model. International Journal of Primatology, 21 (4): 565-595.

Cords, M. 1984. Mating Patterns and Social Structure in Redtail Monkeys. Z. Tierpsychol, 64: 313-329.

Estes, R. 1991. The Behavior Guide to African Mammals. University of California Press.

Kingdon, J. 1984. East African Mammals: An Atlas of Evolution in Africa Vol. 1. Chicago, Il: The University of Chicago Press.

Lambert, J. 1995. Redtail Monkeys and Strychnos mitis: A Plant-animal Interaction in the Kibale Forest, Uganda. International Journal of Primatology, 71(5): 353-355.

Leland, L., T. Struhsaker. 1993. Monkey Business. Animal Kingdom, 90: 24-37.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: The Johns Hopkins University Press.

Smuts, B., D. Cheney, R. Wrangham, T. Struhsaker. 1987. Primate Societies. Chicago, Il: The University of Chicago Press.

Struhsaker, T. 1977. Infanticide and Social Organization in the Redtail Monkey. Z. Tierpsychol., 45: 75-84.

Struhsaker, T., L. Leland. 1979. Advances in the Study of Behavior Vol. 9. Academic Press.

Struhsaker, T., T. Pope. 1991. Mating System and Reproductive Success - A Comparison of 2 African Forest Monkeys. Behaviour, 117: 182-205.

Torstar Books, 1984. All the World's Animals-Primates. New York, Toronto: Torstar Books Inc.