Cercopithecus erythrotis, Waterhouse, 1838

Russell A. Mittermeier, Anthony B. Rylands & Don E. Wilson, 2013, Cercopithecidae, Handbook of the Mammals of the World – Volume 3 Primates, Barcelona: Lynx Edicions, pp. 550-755 : 689-690

74.

Red-eared Monkey

Cercopithecus erythrotis

French: Cercopitheque a nez rouge / German: Rotohrmeerkatze / Spanish: Cercopiteco de orejas rojas

Other common names: Red-eared Guenon, Russet-eared Guenon; Bioko Red-eared Monkey (erythrotis), Cameroon Red-eared Monkey (camerunensis)

Taxonomy. Cercopithecus erythrotis Waterhouse, 1838 ,

Equatorial Guinea, Bioko Island.

C. erythrotisis a member of the C. cephus superspecies group as defined byJ. Kingdon in his 1997 Field Guide to African Mammals. It also includes C. cephus , C. petaurista , C. sclaten, C. ascanius , and C. erythrogaster . C. P. Groves in his 2001 Primate Taxonomy had the same composition for his cephus species group. The subspecies camerunensis hybridizes with C. ¢. cephus in a small area south of the Sanaga River in Cameroon. Two subspecies recognized.

Subspecies and Distribution.

C.e.erythrotisWaterhouse,1838—mountainousareasinC&SBiokoI(EquatorialGuinea).

C. e. camerunensis Hayman, 1940 — SE Nigeria (E of lower Cross River) and NW Cameroon (N of lower Sanaga River), also in a small areajust S of the Sanaga River, near its mouth, between Tinaso and Lake Tisongo.

Descriptive notes. Head-body 45-55 cm (males) and 40-45 cm (females), tail 56— 77 cm (males) and 46-65 cm (females); weight 3-5—4-5 kg (males) and 2.3-3.5 kg (females). The Red-eared Monkey takes its name from a fringe of rusty-red hairs on outer margin ofits ears. A more distinctive feature is its rusty-red tail. Ventrally, tail is red for most ofits length, dorsal surface is a darker brown-red, and tip is blackish. A black brow band extends to ears. Bare skin around eyes is bluish-gray, and muzzle is naked and pink. Upper cheeks have tufts of white and lemon-yellow hairs, and lower cheeks are black. There is a triangular reddish nose spot, and throatis whitish. Crown of head, back, and upper outer leg surfaces are grayish, with orange-brown speckles, becoming grayer on flanks. Lower arms are dark gray, and belly and inner surfaces of limbs are gray. Scrotum is covered in bright orange-red hairs, and the penis is pink. Vulva is light blue. In both sexes, callosities are chocolate-colored. The “Bioko Red-eared Monkey” (C. e. erythrotis ) is smaller, with a darker pelage and shorter tail. The “Cameroon Redeared Monkey” (C. e. camerunensis) has a lighter colored, yellower pelage with shorter hairs. It is larger than the Bioko Red-eared Monkey and has a longertail.

Habitat. The Bioko Red-eared Monkey occurs in primary and secondary lowland tropical and submontane moist forest near rivers. On the mainland, the Cameroon Redeared Monkey is more abundant in mature forest than young secondary forest. This may be because of competition with the Diana Monkey (C. diana ), which flourishes in disturbed and edge habitats. The Cameroon Red-eared Monkey is also more abundant in wetter forests in the southern part of its distribution than in more northerly semideciduous forests. On Bioko Island (where the Diana Monkey is absent), the Bioko Red-eared Monkey is the most abundant monkey species. There,it is most commonly found in mature lowland forest, although it also occurs in secondary lowland forest and overgrown cacao plantations, and above an elevation of 2000 m on Pico Basilé in montane forest and grassland. It will also live in close proximity to people on Bioko Island.

Food and Feeding. Fruits are evidently a major component of the diets of Red-eared Monkeys, along with leaves, shoots, and arthropods. They also raid agricultural crops.

Breeding. There is no information available for this species.

Activity patterns. The Red-eared Monkey uses all levels of the forest canopy. On Bioko Island, they are generally seen at 5-25 m above the ground but sometimes in the upper canopy at 45 m. In Cameroon, they feed and travel lower in the forest canopy than other arboreal guenons. Red-eared Monkeys also go to the ground and have been seen traveling through montane grassland and on beaches on southern Bioko Island.

Movements, Home range and Social organization. Groups of 8-12 Red-eared Monkeys are typical on south-eastern Bioko, whereas they have 4-30 individuals in south-western Cameroon. Groups have a single male, adult females, and young. No published information is available on their home range or ranging behavior.

Status and Conservation. CITES Appendix II. Classified as Vulnerable on The [UCN Red List, including both subspecies. The Red-eared Monkeyis listed as Class B in the African Convention on the Conservation of Nature and Natural Resources. It is believed to have declined in numbers by 30% over the past 27 years (three generations) because of hunting and habitat loss. The bushmeattrade is a significant threat to Redeared Monkeys, and it is the most common monkey in bushmeat markets in Malabo on Bioko Island. A survey counted 622 Red-eared Monkey carcasses for sale in the Malabo market in March—October 1991. An estimated 1025 Red-eared Monkey carcasses are sold annually at three markets in and around Cameroon’s Korup National Park. Despite this, Red-eared Monkeys still manage to persist in relatively high abundance in some areas. They are elusive and can be hard to detect, and they are reasonably adept at evading capture by bushmeat hunters. This has enabled them to survive over a large area in much of their historic distribution. Although also threatened by deforestation through timber extraction and conversion of forest to agricultural land, they are the most common primate on Bioko Island. In 2006, the Bioko Red-eared Monkey was estimated to number ¢.21,000 individuals, down from more than 30,000 individuals in 1986. The Cameroon Red-eared Monkey is believed to have undergone a decline of c.30% over the past 27 years. Red-eared Monkeys are protected by national legislation in Cameroon and Nigeria, and they can be found in several protected areas, including Korup National Park and several forest reserves in Cameroon, Cross River National Park in Nigeria, and Basilé National Park and Southern Island Scientific Reserve on Bioko Island. Despite such protection, hunting is often as severe inside protected areas as it 1s outside of them.

Bibliography. Butynski & Koster (1994), Butynski et al. (2009), Fa et al. (2000), Gartlan & Struhsaker (1972), Gonzéalez-Kirchner (1996), Groves (2001), Hearn et al. (2006), Linder (2008), Maté & Colell (1995), Oates (2011), Oates, Gippoliti & Groves (2008c), Struhsaker (1969, 1970).

Figures

69. Owl-faced Monkey (Cercopithecus hamlyni), 70. Lesula (Cercopithecus lomamiensis), 71. Spot-nosed Monkey (Cercopithecus petaurista), 72. Red-bellied Monkey (Cercopithecus erythrogaster), 73. Sclater’s Monkey (Cercopithecus sclateri), 74. Red-eared Monkey (Cercopithecus erythrotis), 75. Mustached Monkey (Cercopithecus cephus), 76. Red-tailed Monkey (Cercopithecus ascanius)

Subspecies and Distribution. C.e.erythrotisWaterhouse,1838—mountainousareasinC&SBiokoI(EquatorialGuinea). C. e. camerunensis Hayman, 1940 — SE Nigeria (E of lower Cross River) and NW Cameroon (N of lower Sanaga River), also in a small areajust S of the Sanaga River, near its mouth, between Tinaso and Lake Tisongo.