The moustached guenon or moustached monkey (Cercopithecus cephus) is a species of primate in the family Cercopithecidae. It is found in Angola, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Equatorial Guinea, and Gabon. This monkey is an arboreal, omnivorous, and medium-sized mammal. According to the IUCN, the population of the moustached monkeys is considered to be large. They are widely used in biological labs.
Taxonomy The moustached guenon belongs to the genus Cercopithecus, a genus of Old World monkeys, and in the C. cephus group. It is named by its unique moustached face in the monkeys, which has three recognized subspecies: (1) Red-tailed moustached monkey (C. cephus cephus); (2) Gray-tailed Moustached Monkey (C. cephus cephodes); (3) White-nosed Moustached Monkey (C. cephus ngottoensis). However, the C. cephus group also includes many other long-tailed monkey that has other unique morphological patterns except the moustache, for example, the regular red-tailed monkeys (Cercopithecus scanius), the red-bellied monkey (C. e. erythrogaster) and the white-throated monkey (Cercopithecus erythrogaster). The diversity of the moustached guenon is one of the highest among Cercopithecus species. In addition, it is not the only primate genus with the "moustached" patterns (see also moustached tamarins).
Habitat and distribution Cercopithecus cephus usually live in undistributed forests, and they are not easy to be recorded by ground-level cameras because they are arboreal. The C. cephus are diurnal and share vertical spaces with other species. They are born to jump between the tropical trees (up to 20m from a tree to another), and they are widespread in Gabon and Northern Congo. The main region starts from the Sanaga River's South and East side and goes all the way to the Ubangi watersheds, which are mostly covered by the lowland tropical rainforests; however, the gallery forests, flooded forests and mangrove forests are also available for them.
Biographical patterns
Size and weight For adults, the average weight of this species is around 4.1 kg for males and 3.6 kg for females. The average length (head-to-body) is 58 cm for males and 49 cm for females; and the average tail length is 78 cm for males and 69.5 cm for females.
Lifespan The average life span is around 22 years for the wild guenon and up to 36 in captivity.
Face patterns The Cercopithecus genus evolved with special visual patterns for higher efficiency in association; therefore, they can have a higher chance of survival. The C. cephus has powerful and enlarged cheekbones, the most common moustache is the crescent white strip of fur under the nose, and the surrounding fur is black, which shows a strong color contrast; hence, the face patterns can be considered as visual signals. On the top of the white stripe, the main area of the face is greyish blue, and the eyes are copper. The face pattern does not necessarily help to distinguish the male and female guenon. Like other Old World monkeys, the guenon also developed the hairless rump pad for comfortable sitting.
Behaviour
Polyspecific associations The C. cephus cooperates with the C. nictitans and the C. pogonias ships; for example, the cephus monkeys alert the other two groups when they observe the eagles because they live lower than the other two groups, which will give loud vocal alerts to the cephus monkeys when they feel an aerial danger. Studies have shown that these types of associations did not randomly occur in the evolution process. Moreover, the eagle predation mainly shaped these surviving tactics and foraging strategies. The diet of C.cephus includes fruit, insects and leaves, respectively; fruit is the dominant food resource for this species. The polyspecific associations are the main reason that these three species can share the same living area. Up to six guenon species can share the same living area, but four guenon species generally share a common area. Colour patterns in the Cercopithecus provide unique visual identities for each genus which allowed the development of the polyspecific association of the guenon communities. For the red-tailed and the nose-spotted moustached monkeys, the most observable differences are on their faces; however, genital colour contrasts and head movements are some of the less observable differences.
Foraging and antipredator strategies Guenon's foraging efficiency has been shaped significantly by the polyspecific pattern; meanwhile, the quantification of their availability to food remains unsolved due to the complexity of tropical rainforests and the high diversity of food. The antipredator tactics among the three species are also called troop activity, which starts at daybreak and finishes at sunset. The higher interspecific competition was discovered during the troop activity than during the foraging period (fruit feeding time). Nocturnal predators usually come from the ground, making the three species prefer to leave the dense forest at night and sleep in a large tree's crown. Each troop/group of guenon consists of one alpha male and 10 to 40 females (like a harem); the average size of a troop is 22 members. An outsider male may occasionally come to mate with one of the females; however, there will be a chance to fail and the female will escort him out of the territory. The C. cephus has surprisingly large cheek pouches which can carry the same amount of food as its stomach, which allows it to store lots of fruits for later eating in a less dangerous area. The regular foraging time fulfills the day time, and the guenon have the habit to sleep with full stomach. Vocal communications, visual identifications, and tactile activities are involved in the troop's daily social activities, and the guenons usually can give loud and continuous sounds and fast movements combined with the readily visual signals.
Guenon hybridizations and adaptive radiation The moustached monkey's vocal performance is similar to that of C. ascanius and C. erythrotis, and hybridization exists among the three species. Therefore, Thomas Struhsaker suggests categorizing these three species as one species. However, hybridization also increases the risk of guenon's adaptive advantages, that they might lose their visual patterns during the hybridization. The hybridization rate remains low between the moustached monkeys and other guenon subspecies due to the guenon's unique face pattern.
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