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Artiodactyla
Id code: amd150Bovidae
Ammodorcas clarkei
(Thomas, 1891)
(Eng) Dibatag
(Fre) Dibatag, gazelle de Clarke
Taxonomic notes
No significant taxonomic notes.
IUCN threat category
Vulnerable (VU: criteria C1).
Available information
Very little is known on the species' ecology. Some information on habitat, diet, and habits is found in Kingdon (1997) and Stuart & Stuart (1997), while Spinage (1986) reports a little on its habitat. The species' presence in Somalia, Ethiopia and Eritrea is discussed in Funaioli (1971) and Yalden et al. (1996). Funaioli also gives some information on its ecology. Status and distribution are discussed in East (1988); the author also gives some information on its ecology, particularly on its habitat requirements.
Known extent of occurrence
The dibatag is endemic to the Horn of Africa, known only from eastern Ethiopia and northern Somalia (Wilson & Reeder, 1993; East, 1996). Its distribution range was obtained by joining the two country maps in East (1988). It was then updated and revised by Dr. R. East (23 June '97), who suggested marking its presence in Somalia as "possible", although no recent available information can confirm it (Fig. 8.6.9.a). Lack of data, more than distribution discontinuity between adjacent countries, might explain non-corresponding distribution across country boundaries.
Categorical-discrete (CD) distribution model
The species occurs in bushland and thickets and in thicket/grassland mosaics (East, 1988; Kingdon, 1997).
Based on these environmental preferences, the following scores were assigned (Fig. 8.6.9.b) (8.6.9.a):
|
Score |
|
|
1 |
Bushlands and thickets, grasslands, shrublands and their mosaics. |
|
2 |
Barren and sparsely vegetated areas. |
|
3 |
Croplands. |
|
suitable |
moderately suitable |
unsuitable |
Total |
|||||
|
OCCURRENCE |
km2 |
% |
km2 |
% |
km2 |
% |
km2 |
% |
|
certain |
113 101 |
39 |
506 |
0 |
16 |
0 |
113 623 |
40 |
|
possible |
158 443 |
55 |
14 273 |
5 |
16 |
0 |
172 732 |
60 |
|
Total |
271 544 |
95 |
14 779 |
5 |
32 |
0 |
286 355 |
100 |
Tab 8.6.9.a: Cumulative size (km2) of areas pertaining to each environmental suitability class within the Extent of Occurrence.
|
Number Patches (NP) |
Mean Patch Size (MPS) km2 |
Patch Size SD (PSSD) km2 |
Largest Patch Index (LPI) % |
Mean Shape Index (MSI) |
Area-Weighted Mean Shape Index (AWMSI) |
|
|
suitable |
8 |
35 300 |
93 310 |
94.65 |
1.32 |
3.47 |
|
moderately suitable |
72 |
218 |
1 013 |
2.89 |
1.28 |
3.1 |
|
Total AO |
1 |
298 125 |
0 |
100 |
1.6 |
1.6 |
Tab 8.6.9.b: Area of Occupancy fragmentation indexes.
Probabilistic-continuous (PC) distribution model
The output of the probabilistic-continuous (PC) distribution model is shown in Fig. 8.6.9.c.
Validation
No occurrence of the species within the four sample areas.
Comments and conservation issues
Information on this species is so poor that the EO is just a rough approximation of the true situation: the range in Somalia is not even known and is marked as "possible". Yet the models would indicate the potential availability of a large patch of basically suitable areas. There is no apparent fragmentation. However, virtually nothing of the current EO (and of the AO) is included in any protected area. Hunting and displacement by livestock grazing have taken most of the populations and the species’ certain presence is restricted to eastern Ethiopia. Further field surveys and research is urgent and the survival of this unique species may depend on the swiftness of conservation action.
|
OCCURRENCE |
SUITABILITY CLASS |
inside |
outside |
Total |
|
certain |
suitable |
0.58 |
38.92 |
39.50 |
|
moderately suitable |
0 |
0.18 |
0.18 |
|
|
unsuitable |
0 |
0.01 |
0.01 |
|
|
possible |
suitable |
0 |
55.33 |
55.33 |
|
moderately suitable |
0 |
4.98 |
4.98 |
|
|
unsuitable |
0 |
0.01 |
0.01 |
|
|
Total |
0.58 |
99.42 |
100 |
Tab 8.6.9.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.
Funaioli U. (1971). Guida breve dei mammiferi della Somalia. Istituto Agronomico per l'Oltremare. Biblioteca Agraria Tropicale.
Kingdon J. (1997). The Kingdon field guide to African Mammals. Academic Press, London and New York: Natural World.
Spinage C.A. (1986). The Natural History of Antelopes. Croom Helm Publishers Ltd, London. Mamm. Series.
Stuart C., Stuart T. (1997). Field guide to the larger mammals of Africa. Struik Publishers.
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.
Yalden D.W., Largen M.J., Kock D., Hillman J.C. (1996). Catalogue of the mammals of Ethiopia and Eritrea. 7. Revised checklist, zoogeography and conservation. Tropical Zoology: 9, 73-164.