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Artiodactyla
Id code: amd156Bovidae
Cephalophus spadix
True, 1890
(Eng) Abbott's duiker
(Fre) Céphalophe spadix
Taxonomic notes
Possibly a subspecies of C. silvicultor (Wilson & Reeder, 1993).
IUCN threat category
Vulnerable (VU: criteria C1).
Available information
Literature available on this species is very scarce. General information on its ecology is found in Kingdon (1971-77, 1997). Status and distribution are discussed in East (1988). This author also gives some information on its ecology.
Known extent of occurrence
The Abbott’s duiker is restricted to the highlands of north-eastern and central Tanzania (Wilson & Reeder, 1993; East, 1996) as far north as zones adjacent of south Kenya, in the foothills of Mt. Kilimanjaro. Its distribution map was obtained from Kingdon (1971-77), then greatly restricted according to country maps in East (1988). Dr. R. East confirms that this species has been eliminated from parts of its former range (over-hunting and forest destruction), and now occurs only in Usambara, Uluguru, Uzungwa and Rungwe Mts. in Tanzania. Its presence both in south Kenya and in the Rubeho Mts. remains uncertain and has been marked as possible ( Fig. 8.6.62.a). As a result the current geographic range poorly matches the toponyms cited for the species (Kingdon, 1997).
Categorical-discrete (CD) distribution model
The species occurs in montane forests and high altitude marshes (East, 1988; Kingdon, 1997).
Based on these environmental preferences, the following scores were assigned (Fig. 8.6.62.b) (8.6.62.a):
|
Score |
|
|
1 |
Forests within montane and altimontane vegetation. |
|
2 |
Forest mosaics within montane and altimontane vegetation. |
|
3 |
Lowland forests, savannas and croplands. |
|
suitable |
moderately suitable |
unsuitable |
Total |
|||||
|
OCCURRENCE |
km2 |
% |
km2 |
% |
km2 |
% |
km2 |
% |
|
certain |
1 287 |
4 |
1 392 |
4 |
28 675 |
79 |
31 354 |
86 |
|
possible |
1 |
0 |
34 |
0 |
4 986 |
14 |
5 021 |
14 |
|
Total |
1 288 |
4 |
1 426 |
4 |
33 661 |
93 |
36 375 |
100 |
Tab 8.6.62.a: Cumulative size (km
2) 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 |
20 |
64 |
46 |
6.14 |
1.15 |
1.29 |
|
moderately suitable |
28 |
56 |
39 |
6.14 |
1.2 |
1.36 |
|
Total AO |
33 |
86 |
96 |
15.79 |
1.28 |
1.64 |
Tab 8.6.62.b: Area of Occupancy fragmentation indexes.
Probabilistic-continuous (PC) distribution model
The output of the probabilistic-continuous (PC) distribution model is shown in Fig. 8.6.62.c
Validation
No occurrence of the species within the four sample areas.
Comments and conservation issues
A small and fragmented EO that appears largely unsuitable. The small overall AO is further fragmented at least 33 patches and the LPI shows that none of these is more than 15% of the total. Even if the environmental preferences of the species were adjusted, the total area of the EO would still be very small and fragmented. The spatial patterns of this (sub)species appears dramatic, also because virtually none of its AO is included in any protected area in Tanzania. Considering these patterns, the species should be reclassified as endangered.
|
OCCURRENCE |
SUITABILITY CLASS |
inside |
outside |
Total |
|
certain |
suitable |
0.77 |
2.77 |
3.54 |
|
moderately suitable |
0.35 |
3.47 |
3.83 |
|
|
unsuitable |
5.06 |
73.77 |
78.83 |
|
|
possible |
suitable |
0 |
0 |
0 |
|
moderately suitable |
0 |
0.09 |
0.09 |
|
|
unsuitable |
0.56 |
13.14 |
13.71 |
|
|
Total |
6.75 |
93.25 |
100 |
Tab 8.6.62.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.
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.