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Primates
Id code: amd040Cercopithecidae
Cercocebus galeritus
Peters, 1879
(Eng) Tana River mangabey
(Fre) Cercocèbe agile
Taxonomic notes
In accordance with Wilson & Reeder (1993), this species is considered distinct from C. agilis here, although some authors maintain a different classification (see Oates, 1996).
IUCN threat category
Endangered (EN: criteria B1+2abcde, C2a).
Available information
The species is considered highly endangered, and intensive studies on its ecology, status, and conservation biology have been carried out in the last twenty years by several authors (Decker, 1994; Groves et al., 1974; Homewood, 1975, 1978; Homewood & Mkunga, 1978; Kinnaird, 1990; Kinnaird & O'Brien, 1991, 1994; Decker & Kinnaird, 1992; Marsh, 1985; Medley, 1993). General information on the species’ ecology is found in Kingdon (1997) and Stuart & Stuart (1997). Status, distribution, and ecology are discussed in Lee et al. (1988) and Oates (1994, 1996).
Known extent of occurrence
This species is endemic of the lower Tana River in Kenya between Garsen and Wenje (Groves et al., 1974; Wilson & Reeder, 1993). The distribution map was obtained from Groves (1978) and adjusted taking into account Homewood & Rodgers (1981), Groves et al. (1974) and the river network (Fig. 2.3.3.a).
Categorical-discrete (CD) distribution model
The species’ presence is restricted to gallery forest along the floodplain of the Tana River (Homewood, 1975; Groves et al., 1974; Kingdon, 1997).
Based on these environmental preferences, the following preference scores were assigned:
|
Score |
|
|
1 |
Forests and forest mosaics occurring inside a 5-km buffer around permanent water. |
|
2 |
Savannas, savanna mosaics and croplands occurring inside a 5-km buffer around permanent water. |
|
3 |
All vegetation types occurring outside a 5-km buffer around permanent water. |
|
suitable |
moderately suitable |
unsuitable |
Total |
||||
|
km2 |
% |
km2 |
% |
km2 |
% |
km2 |
% |
|
957 |
5 |
2 777 |
14 |
16 448 |
81 |
20 182 |
100 |
Tab 2.3.3.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 |
12 |
92 |
142 |
15.17 |
1.25 |
1.88 |
|
moderately suitable |
6 |
421 |
434 |
34.48 |
1.88 |
2.68 |
|
Total AO |
2 |
1 813 |
963 |
76.55 |
2.17 |
2.45 |
Tab 2.3.3.b: Area of Occupancy fragmentation indexes.
Probabilistic-continuous (PC) distribution model
The output of the probabilistic-continuous (PC) distribution model is shown in Fig. 2.3.3.c.
Validation
No occurrence of the species within the four sample areas.
Comments and conservation issues
The known EO is drawn around the Tana River and associated forests, but when the vegetation types are analysed, the species is found restricted to an even smaller area: out of a total 20 000 km2 of EO, the AO is found to be less than 3000 km2. The CD model shows a clear distribution of forests along the river while the PC model also takes the quality of the surrounding areas in account and incorrectly extrapolates a much wider suitability for the species. Fragmentation is limited to two sections. The species is Endangered but is hardly protected.
|
SUITABILITY CLASS |
inside |
outside |
Total |
|
suitable |
0.22 |
4.52 |
4.74 |
|
moderately suitable |
0.37 |
13.39 |
13.76 |
|
unsuitable |
2.29 |
79.21 |
81.50 |
|
Total |
2.87 |
97.13 |
100 |
Tab 2.3.3.c: Percent of environmental suitability classes within EO (as obtained from the categorical-discrete distribution model) inside and outside the protected areas.
References
Decker B.S. (1994). Effects of habitat disturbance on the behavioral ecology and demographics of the Tana River red colobus (Colobus badius rufomitratus). Int J. Primatol.: 15(5), 703-737.
Decker B.S., Kinnaird M.F. (1992). Tana River red colobus and crested mangabey: results of recent censuses. Amer. J. Primatol.: 26, 47-52.
Groves C.P. (1978). Phylogenetic and population systematics of the Mangabeys (Primates: Cercopithecoidea). Primates: 19, 1-34.
Groves C.P., Andrew R.J., Horne J.F.M. (1974). Tana river colobus and mangabey. Oryx: 12(5), 565-575.
Homewood K.M. (1975). Can Tana River Mangabey survive ?. Oryx: 13, 53-59.
Homewood K.M. (1978). Feeding strategy of the Tana Mangabey Cercocebus galeritus galeritus ( Mammalia: Primates). J.Zool. (Lond.): 186, 375-391.
Homewood K.M., Mkunga J. (1978). Kenya's new primate reserve. Oryx: 14, 175-178.
Homewood K.M., Rodgers W.A. (1981). A previously undescribed Mangabey from southern Tanzania. Int J. Primatol.: 2, 47-55.
Kingdon J. (1997). The Kingdon field guide to African Mammals. Academic Press, London and New York: Natural World.
Kinnaird M.F. (1990). Pregnancy, gestation, and parturition in free-ranging Tana River crested mangabeys (Cercocebus galeritus galeritus). Am.J.Primatol: 22, 285-289.
Kinnaird M.F., O’Brien T.G. (1991). Viable populations for an endangered forest primate, the Tana River Crested Mangabey (Cercocebus galeritus galeritus). Conserv. Biol.: 5 (June), 203-213.
Kinnaird M.F., O'Brien T.G. (1994). Estimation of parameters in population viability analysis: a case study of the Tana River Crested Mangabey. Primate Conservation IUCN/SSC Primate Specialist Group: n° 14/15, 53-57.
Lee P.C., Thornback J., Bennet E.L. (1988). Threatened Primates of Africa. IUCN, Gland - Switzerland and Cambridge, UK.
Marsh C.W. (1985). A Resurvey of Tana River Primates. Report to Institut of Primate Research, Kenya and Departement of Wildlife Conservation and Management. Offset litho.
Medley K. (1993). Primate Conservation along the Tana River, Kenya: An Examination of the Forest Habitat. Conserv. Biol.: 7(1), 109-121.
Oates J.F. (1994). Africa's primates in 1992: conservation issues and options. Amer. J. Primatol.: 34, 61-71.
Oates J.F. (1996). African Primates Status Survey and Conservation Action plan. IUCN/SSC Primate Specialist Group.
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.