Artiodactyla Id code: amd335Bovidae Cephalophus adersi Thomas, 1918 (Eng) Ader's duiker (Fre) Céphalophe de Zanzibar Taxonomic notes It has been considered conspecific with both C. natalensis and C. calliipygus, but here they are all regarded as separate species (Wilson & Reeder, 1993; East, 1996). IUCN threat category Endangered (EN: criteria C1). Available information Little is known on the ecology of this duiker. The only ecological study conducted on this species is the one by Williams et al. (1996), which focused mainly on its habitat use and requirements in Zanzibar. General information on the ecology and distribution of the species is found in Kingdon (1997). Status and distribution, together with some ecological notes, are discussed in East (1988). Known extent of occurrence 
The Aders’ duiker occurs only on Zanzibar (Tanzania) and in Kenya's Arabuko-Sokoke forest (Wilson & Reeder, 1993; East, 1996). The distribution map in Fig. 8.6.47.a was obtained from Kingdon (1971-77) and matched with the two specific country maps in East (1988). Dr. R. East (23 June '97) revised a preliminary map. Categorical-discrete (CD) distribution model The species is only found in coastal and thicket forest (East, 1988; Williams et al., 1996). Based on these environmental preferences, the following scores were assigned (Fig. 8.6.47.b) (Tab. 8.6.47.a):
Tab 8.6.47.a: Cumulative size (km 2) of areas pertaining to each environmental suitability class within the Extent of Occurrence.
Tab 8.6.47.b: Area of Occupancy fragmentation indexes. Probabilistic-continuous (PC) distribution model The output of the probabilistic-continuous (PC) distribution model is shown in Fig. 8.6.47.c. Validation No occurrence of the species within the four sample areas. Comments and conservation issues This species has one of the smallest ranges of all African mammals: out of a total of about 3 800 km2, only 27% is either suitable or moderately suitable. The species is restricted to forests and forest mosaics and these vegetation types are reduced to small remnants on Zanzibar Island and the small forest left on mainland Kenya. These forest remnants are divided into at least 14 patches of very small size and the LPI shows that the single largest patch is only a third of the total AO. Protected areas include about 200 km2 (20%) of the total AO and this is mostly suitable areas. The total amount protected is however very small and this and the small size of the total population require that the species be classified as Endangered.
Tab 8.6.47.c: Percent of environmental suitability classes within EO (as obtained from the categorical-discrete distribution model) inside and outside the protected areas. References East R. (Ed.) (1988). Antelope Global Survey and Regional Action plans, Part I: East and North East Africa. IUCN/SSC Antelope Specialist Group. East R. (Ed.) (1996). Antelope survey update. IUCN/SSC Antelope Specialist Group: n° 2. Kingdon J. (1971-77). East African Mammals. VOL I: primates, hyraces, pangolins, protoungulates, sirenians. VOL IIA: Insectivores and bats. VOL IIB: hares and rodents. VOL IIIA: carnivores. VOL IIIB: large mammals. VOL IIIC: bovids. VOL IIID: bovids. Academic Press, London and New York. Kingdon J. (1997). The Kingdon field guide to African Mammals. Academic Press, London and New York: Natural World. Williams J.M., Mwinyi A.A., Ali R. (1996). A population survey of the three mini-antelope: Ader's duiker, Zanzibar blue duiker, and suni of Unguja, Zanzibar. Gnusletter: 15(2), 6-7. Wilson D.E., Reeder D.M. (Eds) (1993). Mammal Species of the World: A Taxonomic and Geographic Reference. Second edition. Smithsonian Institution Press, Washington D.C.
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