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Primates
Id code: amd076Cercopithecidae
Procolobus verus
(Van Beneden, 1838)
(Eng) Olive colobus
(Fre) Colobe de Van Beneden
Taxonomic notes
Formerly placed in Colobus, it is currently assigned by most authors to a separate genus, together with the red colobus monkey (Wilson & Reeder, 1993; Oates, 1996).
IUCN threat category
Lower Risk, but near threatened (LR: nt).
Available information
The only ecological study conducted on this species is the one by Galat & Galat-Luong (1985), who investigated its habitat, diet, and habits in the Tai Forest (Ivory Coast); the authors focused particularly on the niche separation among coexisting primates and on behavioural aspects of the species’ ecology. A comparative study of habitat use in old forest and secondary growth forest was carried out by Fimbel (1994) in Twai (Sierra Leone). Data on the species’ occurrence in the Gold Coast are reported in Booth (1979). General information on the ecology of the species is found in Bourlière (1985), Kingdon (1997) and Stuart & Stuart (1997). Status, threats, and conservation issues are discussed in Lee et al. (1988), Oates (1996), and Southwick et al. (1986).
Known extent of occurrence
The olive colobus’ geographic range extends discontinuously from Sierra Leone and Guinea to south-east Nigeria, following the course of a number of rivers. This species’ distribution map was obtained from Kingdon (1997) and revised on the basis of the information found in other recent literature sources (such as Oates, 1996). It was finally refined to match the river network (Fig. 2.3.39.a).
Categorical-discrete (CD) distribution model
This species inhabits rainforests and riparian forests, as well as the margins of forests (Bourlière, 1985; Lee et al., 1988; Kingdon, 1997).
Based on these environmental preferences, the following scores were assigned (Fig. 2.3.39.b) (2.3.39.a):
|
Score |
|
|
1 |
Forests; forest mosaics occurring inside a 1-km buffer around permanent water. |
|
2 |
Forest mosaics occurring outside a 1-km buffer around permanent water. |
|
3 |
Savannas and croplands. |
|
suitable |
moderately suitable |
unsuitable |
Total |
||||
|
km2 |
% |
km2 |
% |
km2 |
% |
km2 |
% |
|
65 497 |
51 |
50 265 |
39 |
13 313 |
10 |
129 075 |
100 |
Tab 2.3.39.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 |
121 |
540 |
1 807 |
11.48 |
1.63 |
5.02 |
|
moderately suitable |
190 |
267 |
1 177 |
12.32 |
1.46 |
4.8 |
|
Total AO |
28 |
4 145 |
9 171 |
40.76 |
1.69 |
3.1 |
Tab 2.3.39.b: Area of Occupancy fragmentation indexes.
Probabilistic-continuous (PC) distribution model
The output of the probabilistic-continuous (PC) distribution model is shown in Fig. 2.3.39.c.
Validation
No occurrence of the species within the four sample areas.
Comments and conservation issues
The small areas that compose the total EO are often so close to each other that they should probably be merged into single patches: a more detailed field study should be carried out to verify the actual distribution range of the species. Within the known EO the areas appear to be generally suitable (51% are suitable and 39% are moderately suitable) and, within the many small patches, they appear not to be further fragmented (NP of the total AO). The largest patch in Liberia and Ivory Coast accounts for about 40% of the total AO. The most unsuitable areas appear to be in Nigeria (see both models). About 5% of the suitable areas is protected (little more than 3 000 km2) and this appears to be insufficient to ensure the long-term conservation of the species.
|
SUITABILITY CLASS |
inside |
outside |
Total |
|
suitable |
2.67 |
48.07 |
50.74 |
|
moderately suitable |
2.12 |
36.82 |
38.94 |
|
unsuitable |
0.18 |
10.13 |
10.31 |
|
Total |
4.98 |
95.02 |
100 |
Tab 2.3.39.c: Percent of environmental suitability classes within EO (as obtained from the categorical-discrete distribution model) inside and outside the protected areas.
References
Booth A.H. (1979). The distribution of primates in the Gold Coast. In: Sussman R.W. (Ed.). Primate Ecology. Problem-oriented field studies. Wiley, Chichester & New York: chap. 7: 139-154.
Bourlière F. (1985). Primate communities: their structure and role in tropical ecosystems. Int J. Primatol.: 6, 1-26.
Fimbel C. (1994). The relative use of abandoned farm clearings and old forest habitats by primates and a forest antelope at Tiwai, Sierra Leone, West Africa. Biological Conservation: 70, 277-286.
Galat G., Galat-Luong A. (1985). La communauté de Primates diurnes de la foret de Tai, Côte d'Ivoire. Revue de Ecologie (La Terre et la Vie): 40, 7-32.
Kingdon J. (1997). The Kingdon field guide to African Mammals. Academic Press, London and New York:Natural World.
Lee P.C., Thornback J., Bennet E.L. (1988). Threatened Primates of Africa. IUCN, Gland - Switzerland and Cambridge, UK.
Oates J.F. (1996). African Primates Status Survey and Conservation Action plan. IUCN/SSC Primate Specialist Group.
Southwick C.H., Mittermeier R.A., Robinson J.G., Tenaza R.A. (1986). Report of the American society of primatologists subcommitee on the status of primates in the wild. Amer. J. Primatol.: 10, 371-378.
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.