ArtiodactylaId code: amd022
(Eng) Ogilby's duiker
(Fre) Céphalophe d'Ogilby
Pending a detailed revision of the genus Cephalophus, the classification of this species should be regarded as tentative (East, 1990).
IUCN threat category
Lower Risk, near threatened (LR:nt) both as C. ogilby and as C. o. crusalbum (White-legged duiker) in Congo and Gabon.
Very little is known on the ecology of the species. Information available is reported in Kingdon (1997). Gautier-Hion & Gautier (1994) conducted a very accurate and updated survey of the species' distribution in Gabon. Status, distribution, and some information on its ecology are found in East (1990).
Known extent of occurrence
This duiker is recorded in three distinct zones close to the West African coast: from Sierra Leone to Ghana; between Nigeria, Cameroon and Bioko; in Gabon. A rough distribution map was obtained from Haltenorth & Diller (1980) and updated on the basis of the more recent and reliable country maps in East (1990) and information in Kingdon (1997). Its distribution in Gabon also takes into account Gautier-Hion & Gautier (1994). Dr. R. East revised a preliminary map (23 June '97) (Fig. 8.6.58.a).
Categorical-discrete (CD) distribution model
Primarily associated to high forest (Kingdon, 1997; East, 1990).
Based on these environmental preferences, the following scores were assigned (Fig. 8.6.58.b) (8.6.58.a):
Tab 8.6.58.a: Cumulative size (km2) of areas pertaining to each environmental suitability class within the Extent of Occurrence.
Tab 8.6.58.b: Area of Occupancy fragmentation indexes.
Probabilistic-continuous (PC) distribution model
The output of the probabilistic-continuous (PC) distribution model is shown in Fig. 8.6.58.c.
Tab 8.6.58.c: Categorical-discrete (CD) distribution model validation parameters.
Comments and conservation issues
The known EO is small and less than 50% of it is classified as suitable (260 685 km2). Although the low number of valid plots (15) suggests some caution in the interpretation of the Index of Accordance, a score of 46.67% nevertheless indicates low reliability for the CD model. Thus the following information should be considered with caution: the EO appears to be fragmented with more than 200 patches. When the moderately suitable areas are considered, the fragmentation is reduced, but not enough is known about this species to justify the extensive inclusion of forest mosaics into the range of this species’ environmental preferences. The LPI shows a significant large patch (42.82%) within the EO, confirmed by the comparison of the two shape indexes. Both models indicate that the part of the EO that extends across Nigeria and Cameroon is of relatively poor quality and possibly also more fragmented. The range in Gabon should be verified as it is large and of good quality and it may add significantly to the species’ survival. About 3% of the AO is protected by parks and reserves, a very small percentage when considering that it applies to forest habitat types.
Tab 8.6.58.d: Percent of environmental suitability classes within EO (as obtained from the categorical-discrete distribution model) inside and outside the protected areas.
East R. (Ed.) (1990). Antelopes Global Survey and Regional Action Plans. Part 3: West and Central Africa. IUCN/SSC Antelope Specialist Group.
East R. (Ed.) (1996). Antelope survey update. IUCN/SSC Antelope Specialist Group: n° 2.
Gautier-Hion A., Gautier J. (1994). Cephalophus ogilby crusalbum Grubb 1978, described from coastal Gabon, is quite common in the Foret-Des-Abeilles, central Gabon. Revue de Ecologie (La Terre et la Vie): 49(2), 177-180.
Haltenorth T., Diller H. (1980). A field guide to the mammals of Africa, including Madagascar. Collins, London.
Kingdon J. (1997). The Kingdon field guide to African Mammals. Academic Press, London and New York: Natural World.