Cephalophus dorsalis, Gray, 1846

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 : 719-720

244.

Western Bay Duiker

Cephalophus dorsalis

French: Céphalophe a dorsale / German: Schwarzriickenducker / Spanish: Duiker de dorso oscuro occidental

Other common names: \ Western Black-backed Duiker

Taxonomy. Cephalophus dorsalis Gray, 1846 ,

Sierra Leone.

C. dorsalis formerly included populations of both Western Bay Duiker and the Eastern Bay Duiker ( C. castaneus ) as subspecies. Monotypic.

Distribution. Guinea-Bissau to Togo; an isolated population exists in E Nigeria (E of the Cross River) and W Cameroon.

Descriptive notes. Head-body 76-85 cm, tail 8.1-11. 6 cm, shoulder height 45-50 cm; weight 17.9-23. 4 kg. A heavily built duiker, with females slightly larger than males. Body size of the Western Bay Duiker is smaller and lighter than the Eastern Bay Duiker ( C. castaneus ). The pelage is coarse, with the hair shortest on the neck; in some animals, the hair on the rump is noticeably longer. General coloris a bright chestnut or reddish-brown; the legs are darker brown from below the shoulder and hocks. The underparts are colored as above, but with a black patch on the chest that extends into a dark median stripe along the belly. A distinctive and well-defined black dorsal stripe runs from the nape of the neck to the tail (in some specimens from Ghana, the stripe begins at the shoulders, not the nape). This stripe may expand on the shoulders, in some individuals connecting with the dark coloration of the legs. The dorsal stripe is generally narrower than in the Eastern Bay Duiker: its width averages 4: 94 cm in the Western Bay Duiker from the Guinean forest block of West Africa, butis significantly narrower in Nigeria and Cameroon, averaging only 2: 67 cm wide. The tail is black above (an extension of the dorsal stripe) and white below. Well-developed, pocket-like inguinal glands are present near the stifle. The face has a very dark brown or black frontal blaze, occasionally with reddish tones. A poorly-developed tuft of hair is present at the top of the head;it is usually blackish. The lips, chin, and a spot above each eye are white; there is also a bright rufous eyebrow streak. The ears are short, broad, and lined with white hairs. A long slit in front of each eye marks the preorbital glands, which are larger in males. Short, conical horns are present in both sexes, but longer in males; the bases of the horns are ridged. Dental formulais10/3, C0/1,P 3/3, M 3/3 (x2) = 32.

Habitat. A forest specialist, frequently seen in moist lowland primary forest and occasionally observed in secondary growth. The Western Bay Duiker is encountered in both gallery (closed-canopy riverine) and non-gallery forests in Sierra Leone. This species is rarely observed in forest fragments with high human disturbance, and is thus now absent from forest patches within savanna—forest mosaics. Dense thickets and dead trees are essential refugia. The Western Bay Duikeris preyed upon by nocturnal predators such as Leopards (Panthera pardus) and large pythons.

Food and Feeding. Primarily frugivorous (85-98% of the dietis fruits and seeds, based on two samples). The sense of smell is well developed and is used in finding food. The Western Bay Duiker has a large gape, enabling it to feed on large and tough-skinned fruits that other duikers cannot chew. For fruits with very large seeds (stones), the pulp is chewed away and the stones spat out. The stones of Ricinodendron heudelotii, Gambeya beguei, and Hugonia planchonii may be swallowed whole along with the fruit but are often regurgitated; these stones are frequently found in daytime resting places. Fruits from the above-mentioned species, as well as Ongokea gore, Elaeis guineensis, Blighia unijugata, and Irvingia gabonensis, have been recovered in stomach-content analyses in Ghana. Pentaclethra macrophylla and Klainedoxa gabonensis have been consumed by individuals in Liberia, and Dacryodes klaineana, Chrysophyllum taiense, and Dialium aubrevillei are in the diet of duikers in Ivory Coast. This species will consume animal matter, including bird eggs. A captive individual actively hunted and consumed small and medium-sized birds; doves were entirely eaten except for the wings and feet.

Breeding. Western Bay Duikers breed year-round. Most data on the species’ breeding behavior comes from a single female in Ghana. Estrus lasts no more than a day, during which the male courts the female with intense chasing. Ritualized leg-kicking by the male (“laufschlag”) is minimal in this species, and (when performed) occursjust prior to copulation. Gestation lasts for approximately 238 days; litter size is one and weight at birth is 1.6-1. 7 kg. Infants are dark brown or nearly black in color; the dorsal stripe is difficult to discern except faintly on the rump. Neonates lie up in a sheltered spot for several weeks, and begin trying solid food at three weeks of age. Weaning occurs at 3-5 months. The bright reddish adult body color appears at five or six months of age. Females reach sexual maturity at approximately 18 months; the onset of puberty in males has not been determined. Individuals may live for more than 16 years in captivity.

Activity patterns. Nocturnal. Observations of captive Western Bay Duikers indicate that 65% of night-time hours, and only 17% of daylight hours, are spent active. Encounter rates in the wild are 50 times higher at night than during the day. Sheltered resting places are used during the day; rumination frequently occurs at thesesites.

Movements, Home range and Social organization. The Western Bay Duiker is poorly known compared to the Eastern Bay Duiker, which it likely resembles in habits. This species is typically solitary, but no data on home range size has been collected. Latrine areas are not used by this species.

Status and Conservation. CITES Appendix II. Classified as Least Concern on The [UCN Red List. This species is no longer common as a result of habitat loss. Overhunting may also play a role in the decline of this species, although its nocturnal nature makesit less susceptible to hunting than sympatric diurnal duikers. It is rare in Guinea-Bissau, Guinea, Sierra Leone, Togo, and Nigeria, and uncommon in Ivory Coast. The Western Bay Duiker is only considered common in protected areas in Liberia and Ghana.

Bibliography. East (1999), Grubb & Groves (2001), IUCN/SSC Antelope Specialist Group (2008b), Kortenhoven (2009), Lydekker (1914), Newing (1994, 2001), 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. Guinea-Bissau to Togo ; an isolated population exists in E Nigeria (E of the Cross River) and W Cameroon .