Cephalophus adersi, Thomas, 1918

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 : 727-728

258.

Aders’s Duiker

Cephalophus adersi

French: Céphalophe d'Aders / German: Sansibar-Ducker / Spanish: Duiker de Aders

Other common names: Zanzibar Duiker

Taxonomy. Cephalophus adersi Thomas, 1918 ,

Zanzibar.

A taxonomically distinct duiker with poorly resolved affinities. Monotypic.

Distribution. Zanzibar I, Tanzania, and the Arabuko Sokoke Forest in SE Kenya; a second mainland population has very recently been confirmed in the Boni and Dodori National Rerserves in NE Kenya.

Descriptive notes. Head—body 63-78 cm, tail 6-13. 8 cm, shoulder height 37-5—-44 cm; weight 9 kg (range: 6.8-12. 4 kg). The pelage of Aders’s Duikeris soft, with a consistent texture across the neck and body. Overall color is tawny red, growing darker and more richly colored on the rump and becoming somewhat grayer on the neck. Specimens from southern Zanzibar (Jozani forest) are reportedly paler. The darker dorsum gradually pales on the flanks; the belly and inner surfaces of the upper limbs are white, and the underside of the neck is pale gray. There is no dorsal stripe. Leg coloration is reddish, darkening to blackish-brown at the hooves. All limbs, especially the front legs, are marked with distinctive irregular white spots on their lower halves. The rump and upper hindlegs are characteristically marked with a horizontal band of white hair (approximately 15 cm wide) that merges with the paler underparts at the stifle. The tail is slender and mostly tawny in color, with a terminal tuft of whitish hair. The face is grayish-fawn with a rufous forehead. Preorbital glands are present, but are quite small (the slits are never more than 1-8 cm long). A tuft of bright red hairs is present at the top of the forehead, forming a flat-topped crest; its hairs are approximately 4 cm long. Spike-like horns are present in both sexes, but they are much shorter and often hidden within the coronal tuft in females. Horn length averages 4-6 cm in males (range: 3.5-5. 3 cm) and 2-8 cm in females (range: 1.4-3. 5 cm). Dental formula is10/3,C0/1,P 3/3, M 3/3 (x2) = 32.

Habitat. Undisturbed coastal thickets and forests. In Zanzibar, Aders’s Duiker is most common in tall thicket forest on coral rag substrates, a habitat with a relatively high canopy (at least 3 m) and an open understory. Population densities are highest in undisturbed older growth areas (averaging 11-4 ind/km?), but the speciesis also occasionally encountered at secondary thicket. The species is restricted to Cynometra manilkera forest in Arabuko Sokoke Forest, where it occurs in densities of approximately 2-8 ind/km?®.

Food and Feeding. Aders’s Duikers feed primarily on fallen fruits, dicotyledoneus leaves (both fresh and fallen), and flowers, seeds, buds, and sprouts. Groups of Sykes’ Monkeys (Cercopithecus albogularis) or Zanzibar Red Colobus (Piliocolobus kirkii ) are often followed: the items dropped, discarded, and dislodged by the primates are a principal food source. Most specific dietary information is anecdotal. Stomach contents of a single adult male contained the fruits of Tetracella littoralis, Diospyros consolatae, and Ficus sur. Other species reported to be consumed include Mystroxylon aethipicum, Cassine aethiopica, Canthium sp., Polyspheria sp., and Fuclea schimperi. Aders’s Duikers can apparently glean sufficient water from their diet to manage without drinking from pools (surface water is absent in the majority of coral rag forests).

Breeding. There is little specific information available for this species. Aders’s Duiker is reported to breed throughout the year; pregnant females have been captured in June-November, and a lactating female was observed in December.

Activity patterns. Diurnal or crepuscular feeding occurs from dawn until around 11:00 h, followed by a period of rest and rumination. At about 15:00 h, Aders’s Duikers generally become active and continue foraging until nightfall.

Movements, Home range and Social organization. There islittle specific information available for this species. Usually solitary, but sometimes observed in groups of two or three individuals. Regular pathways are commonly used. Aders’s Duikeris reported to defend territories. Although the preorbital glands are small, their secretions are used to mark prominent twigs; dung heaps may also help delineate territories. This species is very shy, alert, and has excellent senses of hearing and smell.

Status and Conservation. Classified as Critically Endangered on The IUCN Red List. There are no remaining natural predators on Zanzibar; pythons (Python sebae) are uncommon and generally small, and Leopards (Panthera pardus) are extremely rare and possibly extirpated. Humans have a major impact on the continued survival of Aders’s Duiker. Overhunting has led to long-term declines in Zanzibar. At Mtende, Aders’s Duikers were once estimated to comprise 70% of hunters’ kills, although trapping success has decreased dramatically in recent decades. Habitat destruction and fragmentation threaten remaining populations, primarily as the result of collection of firewood (which is a principal source of income for many families). Dogs are known to have destroyed an introduced population of Aders’s Duiker on Funzi Island, where these antelopes had previously thrived. The last formal estimates of population size (.1999) concluded that perhaps 600 Aders’s Duikers remain on Zanzibar and fewer than 300-420 live in Arabuko-Sokoke Forest, Kenya. Since these estimates, a third population has been discovered in north-eastern Kenya (Boni and Dodori National Reserves). Aders’s Duikers are commonly recorded in camera-traps in this area, and this population may prove to be a stronghold for the species.

Bibliography. Andanje et al. (2011), Daniels (2004), East (1999), Finnie (2008), Kanga (1995), Kingdon (1982, 1997), Wilson (1987, 2001).

Figures

On following pages: 259. Western White-bellied Duiker (Cephalophus leucogaster); 260. Uele White-bellied Duiker (Cephalophus arrhenii); 261. Red-flanked Duiker (Cephalophus rufilatus); 262. Natal Red Duiker (Cephalophus natalensis); 263. Harvey's Duiker (Cephalophus harveyi); 264. Black-fronted Duiker (Cephalophus nigrifrons); 265. ltombwe Duiker (Cephalophus hypoxanthus); 266. Rwenzori Duiker (Cephalophus rubidus); 267. Mount Elgon Duiker (Cephalophus fosteri); 268. Mount Kenya Duiker (Cephalophus hooki)

Distribution. Zanzibar I, Tanzania , and the Arabuko Sokoke Forest in SE Kenya ; a second mainland population has very recently been confirmed in the Boni and Dodori National Rerserves in NE Kenya .