Cephalophus castaneus (Thomas, 1892)

Don E. Wilson & Russell A. Mittermeier, 2011, Bovidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 444-779 : 720

245.

Eastern Bay Duiker

Cephalophus castaneus

French: Céphalophe bai / German: Kongo-Schwarzriickenducker / Spanish: Duiker de dorso oscuro oriental

Other common names: Eastern Black-backed Duiker

Taxonomy. Cephalophus dorsalis castaneus Thomas, 1892 ,

Cameroons.

Formerly considered to be a subspecies of C. dorsalis , which it closely resembles. Monotypic.

Distribution. S Cameroon (E of Adamawa Highlands) and S Central African Republic to E DR Congo, S to N Angola; less abundant in eastern forests within its range.

Descriptive notes. Head-body 88-3 103.2 cm, tail 8:1-12. 6 cm, shoulder height 45-52 cm; weight 18.4-24. 2 kg. Females are slightly larger than males. The Eastern Bay Duiker is larger and darker in color than the Western Bay Duiker ( C. dorsalis ); the ears are also slightly larger. Overall coloration is a rich reddish chestnut brown, with the undersides slightly brighter than the back. A wide dorsal stripe of black hair runs along the spinal ridge from the neck to the rump, narrowing to a thin line that extends to the end ofthe tail. The width of this dorsal stripe is generally greater than 8 cm (wider than that of the Western Bay Duiker), although in some localities the width averages only 4: 6 cm. All four legs are dark brown. The tail is black bordered with white and a white terminal tuft. The throat and upper neck are whitish. Pronounced cheek muscles accentuate the broad head and reduced muzzle. White lips and chin contrast with the chestnutred face. Superciliary stripes are bright rufous, and a white spot is usually present immediately above each eye; these markings are generally less strong than in the Western Bay Duiker. A reddish frontal blaze extends up the bridge of the nose to a wide triangle on the forehead. This is extended by the bright chestnut-red tuft on the crown of the head (with hairs that are basally dark and distally red). The face and crest are usually red, not blackish as in the Western Bay Duiker. The ears are dark brown on the back; the pale interior has sparse short white hairs. The horns of males are longer than those of females, but in both sexes they are parallel and smooth from base to tip. Generally 5:1.7-9 cm in length, horns may grow up to 9-25 cm. Dental formula is 1 0/3, C 0/1, P3/3,M3/3 (x2) = 32.

Habitat. The Eastern Bay Duiker shows a distinct preference for closed-canopy forest, and is found most frequently in moist lowland areas. Its reliance on dense cover makes the species more susceptible than other duikers to human disturbances such as agriculture. Density estimates are 1-5-8-7 ind/km?.

Food and Feeding. Primarily frugivorous. Fruits comprise, on average, 86:3% of the diet (on a dry weight basis, based on stomach content analysis of 51 individuals). Small fruits, with a diameter less than 2-5 cm, constitute the greatest proportion of stomach contents and are usually eaten whole. Otherfruits up to 20 cm in diameter may also be consumed; the pulp of large-seeded fruits is usually chewed off and the seeds spat out. Large seeds up to 2 cm in diameter (from fruiting trees such as Gambeya beguei, Hugonia platysepala and H. planchonii, Ricinodendron heudelotii, Pseudospondias longifolia, Antrocaryon klaineanum, and Elaeis guineensis ) may be swallowed whole, but are usually regurgitated intact at resting sites. Seeds without strong protective coatings may be chewed and eaten. Leaves comprise 11-1% of the diet, and are consumed at higher frequencies during March, April, and May (the “short” rainy season) than any other time during the year. Flower buds, fungi, and animal matter comprise the rest of the diet; termites and other invertebrates make up most animal matter consumed, but the Eastern Bay Duiker may also feed at carcasses. Plant species most frequently consumed include Pachypodium sp., Polyalthia suaveolens, Dacryodes buttneri, Santiria trimera, Irvingia gabonensis and I. grandifolia, Klainedoxa gabonensis, Panda oleosa, Blighia welwitschii . C. castaneus may “kneel” on the carpal joints when feeding from the ground, and can stand vertically on the hindlegs for short periods to reach hanging foods that would otherwise be unreachable.

Breeding. Eastern Bay Duikers are polygynous and breed throughout the year, with a peak in births in the rainy seasons (notably May and October in Gabon) as well as in the short dry season (January-February). During courtship, a male pursues a female with his head outstretched, licking the anogenital region of the female. Males test female receptiveness by performing the flehmen response on fresh urine (each flehming lasts an average of 9-3 seconds). Unreceptive females puff at approaching males; they may avoid further advances by retiring to a sheltered spot. Receptive females remain quiet during courtship and will stop and stand for mounting. Estrus lasts for less than 24 hours, and copulation duration is typically 1-2 seconds. Each copulation attemptis followed immediately by a new pursuit. Ritualized foreleg kicking (“laufschlag”) has not been observed. Gestation is approximately 240 days; litter size is usually one. Infants are blackish-brown, with red on the back, sides, and face. White facial spots are less apparent in juveniles than in adults. First reproduction occurs around 2-5 years, and a female generally produces 0-7 young/year. Maximum recorded life span in captivity is 17 years.

Activity patterns. Nocturnal. During the day, the Eastern Bay Duiker hides in areas with highly restricted visibility (on average, visibility is only 1-2 m), such as in buttress roots of large trees, hollow logs, and recent deadfall. Hiding places may be reused from day to day, and are the principal site of rumination. Eastern Bay Duikers will often remain hidden in resting sites even when directly approached. Activity and foraging begin slightly before sunset, between 18:00 h and 18:30 h, and cease before dawn, usually between 05:30 h and 06:00 h. Most movements occur at the start and end of the night, corresponding with searching for food (19:00-21:00 h), and then a sheltered location in which to rest for the day is selected in the early morning. Females may travel 1-1-9 km every night; males average significantly more, at 4-3 km per night. Nightly foraging is interrupted 1-3 times by short rests averaging 44 minutes; these occur more frequently at the start of the night than at the end.

Movements, Home range and Social organization. Almost exclusively solitary. Social contact may occur during periods of activity, but tends to be brief. Eastern Bay Duikers are never found resting with others. Individuals inhabit home ranges that may vary from 0-07 km?® to 0-79 km?; in a study in Gabon, females generally used 0-2-0-4 km? and the single male used an area twice that size. Overlap between home ranges may result in up to six or seven duikers (including infants and juveniles) being present in a single male’s range. Home ranges vary in size depending on season, being generally larger during the dry seasons. The sense of smell is most important for social communication. Males mark vertical objects (especially tree trunks) with secretions from their preorbital glands at a frequency of 19-20 markings/hour, forming a whitish plaque of crystallized secretion on often-used branches. Eastern Bay Duikers tend to move slowly with the head stretched out at shoulder height, dropping the head so that the nose is at ground level on a regular basis. Individuals will frequently stop to smell areas marked by other duikers with preorbital gland secretions, urine, or feces. Vocalizations are rare; a weak “hon,” produced with a closed mouth, is used when two individuals are in close proximity (either in sight or when scent marks are sufficiently fresh). Being nocturnal, the sense of sight is not especially important; visual signs (such as horn scrapes on tree trunks or bushes) are not left. Likewise, detection of danger is principally by smell and hearing. Upon detection, an Eastern Bay Duiker will freeze in position; the head (with ears pricked) is then moved either side-to-side or up-anddown to better detect the threat. A threatened duiker will attempt to move off silently if possible. When startled, this species will flee directly into dense cover with the head stretched forward, and will then observe the threat while standing stock-still. Thereis no alarm vocalization or warning in the form of stamping of the forefeet.

Status and Conservation. CITES Appendix II (under C. dorsalis ). Classified as Least Concern on The IUCN Red List (under C. dorsalis ). The Eastern Bay Duiker is common to abundant in all core range countries ( Cameroon, Central African Republic, Gabon, Equatorial Guinea, Republic of the Congo, and DR Congo). However,it is believed extinct in Uganda, and is of unknown status in Angola. The Eastern Bay Duikeris frequently caught in wildlife snares; in south-western Central African Republic,this species accounted for 15% of all duikers caught. Its preference for primary forest also makes habitat loss and degradation a significant threat.

Bibliography. Dubost (1983), Dubost & Feer (1992), East (1999), Feer (1989a, 1989b, 1995), Grubb & Groves (2001), IUCN/SSC Antelope Specialist Group (2008b), Lydekker (1914), Mabrant & Maclatchy (1949), Noss (1998a, 1998b), Weigl (2005), Wilson (2001).

Figures

On following pages: 245. Eastern Bay Duiker (Cephalophus castaneus); 246. Jentink’s Duiker (Cephalophus jentinki); 247. Western Yellow-backed Duiker (Cephalophus silviculton; 248. Eastern Yellow-backed Duiker (Cephalophus curticeps); 249. Abbott's Duiker (Cephalophus spadix); 250. Black Duiker (Cephalophus niger); 251. Ogilby’s Duiker (Cephalophus ogilbyi); 252. White-legged Duiker (Cephalophus crusalbum): 253. Brooke's Duiker (Cephalophus brookel); 254. Peters's Duiker (Cephalophus callipygus).

Distribution. S Cameroon (E of Adamawa Highlands) and S Central African Republic to E DR Congo , S to N Angola ; less abundant in eastern forests within its range.