ARTIODACTYLA

Artiodactyla Id code: amd018

Bovidae
Cephalophus monticola

(Thunberg, 1789)

(Eng) Blue duiker

(Fre) Céphalophe bleu

Taxonomic notes

As in Wilson & Reeder (1993) and East (1996), the blue duiker is regarded here as separate from the closely related C. maxwellii.

IUCN threat category

Not listed. However it is cited as Lower Risk, least concern in East (1996).

Available information

The species' ecology has been studied in several areas of its range of distribution. In East Africa, a study on habitat selection in virgin and exploited areas of the Kibale Forest was conducted by Nummelin (1990). Williams et al. (1996) investigated aspects of the ecology of the species, particularly habitat selection and population density, in Zanzibar. In West Africa, a similar study to that of Nummelin was carried out by Fimbel (1994) in disturbed and undisturbed areas of the Tiwai Forest in Sierra Leone. The ecology of the species in a forested area is described by Dubost (1980, 1983a, 1983b), that focused mainly on behavioural aspects. Some notes on habitat use are also found in Heymans & Lejoly (1981), while Gautier-Hion et al. (1980) give a rather accurate description of its feeding habits. The presence of the species at Idjwi Island (Lake Kivu, former Zaire), was assessed by Rahm & Christiansen (1966). In Southern Africa, the species' ecology has been widely studied in Natal (South Africa) (Bowland, 1990; Bowland & Perrin 1994; Rowe-Rowe, 1994). Activity, reproduction, and intraspecific relationships are discussed by Crawford (1984), who studied this species in a coastal forest of the Cape Province (South Africa). Notes on habitat use in Namibia are reported by Tinley (1969). A complete account of the ecology of the species in this subregion is found in Mills & Hes (1997) and Skinner & Smithers (1990).

General information on the species' ecology is reported by several authors (Estes, 1991; Haltenorth & Diller, 1977; Kingdon, 1997; Stuart & Stuart, 1997). Status and distribution, together with some information on its ecology, are found in East (1988, 1989, 1990).

Known extent of occurrence

This duiker occurs from east Nigeria to Kenya and Tanzania, southwards to Angola, Zambia, Malawi, east Zimbabwe and Mozambique; it is also present in Natal and Cape Province and on Zanzibar, Bioko and Pemba islands (Wilson & Reeder, 1993; East, 1996). Its distribution map was first obtained from Skinner & Smithers (1990), then refined following the boundaries of the more reliable country maps in East (1988, 1989, 1990), as indicated by Dr. R. East (23 June '97) (Fig. 8.6.54.a.).

Categorical-discrete (CD) distribution model

The species occurs in lowland and mountain rainforest, riverine forest and moist savanna; its also inhabits forest patches and gallery forest in the savanna zone (Kingdon, 1997; Skinner & Smithers, 1990; East, 1988, 1989, 1990)

Based on these environmental preferences, the following scores were assigned (Fig. 8.6.54.b) (8.6.54.a):

Score (*)
1	Forests.
2	Forest mosaics; moist woodlands and thickets.
3	Other savanna types and croplands.
(*) Scores increased for vegetation types occurring inside a 1-km buffer around permanent water.
		suitable		moderately suitable		unsuitable		Total
OCCURRENCE		km²	%	km²	%	km²	%	km²	%
certain		3 398 353	54	2 023 507	32	863 844	14	6 285 704	100
possible		2 122	0	5 918	0	6 796	0	14 836	0
Total		3 400 475	54	2 029 425	32	870 640	14	6 300 540	100

Tab 8.6.54.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	3634	935	46 480	51.59	1.4	47.2
moderately suitable	4493	453	11 405	11.59	1.35	37.17
Total AO	417	13 024	255 127	96.03	1.42	32.58

Tab 8.6.54.b: Area of Occupancy fragmentation indexes.

Probabilistic-continuous (PC) distribution model

The output of the probabilistic-continuous (PC) distribution model is shown in Fig. 8.6.54.c.

Validation

% of EO in sample areas	Number of valid plots	Index of Accordance (%)
7.25	156	66.03

Tab 8.6.54.c: Categorical-discrete (CD) distribution model validation parameters.

Comments and conservation issues

One of the duikers with the widest distribution range. The known EO of more than 6 million km² is largely suitable and the AO accounts for about 86% of it. The reliability of the CD model is good (Index of Accordance 66.03%), and the model shows that northern Mozambique is sufficiently suitable; the boundary of the EO along the Tanzania-Mozambique border should be verified. The small area of possible presence in Kenya appears to be largely unsuitable. The southern part of the range (in South Africa) is also of poor quality and highly fragmented. The best part of the range is the large block of suitable areas in the central African countries. The high AWMSI indicates the highly intricate pattern of the boundaries of the suitable areas, possibly due to the association to riverine areas. About 7.5% of the total AO is included in existing protected areas. The species is not considered threatened although it is intensively hunted and trapped.

OCCURRENCE	SUITABILITY CLASS	inside	outside	Total
certain	suitable	3.08	50.86	53.94
	moderately suitable	3.02	29.10	32.12
	unsuitable	2.24	11.47	13.71
possible	suitable	0.01	0.03	0.03
	moderately suitable	0.02	0.08	0.09
	unsuitable	0.02	0.09	0.11
Total		8.38	91.62	100

Tab 8.6.54.d: Percent of environmental suitability classes within EO (as obtained from the categorical-discrete distribution model) inside and outside the protected areas.

References

Bowland A.E. (1990). The ecology and conservation of blue duiker and red duiker in Natal. Ph. D. Thesis, University of Natal, Pietermaritzburg.

Bowland A.E., Perrin M.R. (1994). Density estimate methods for the blue duikers Philatomba monticola and red duikers Cephalophus natalensis in Natal, South Africa. J. African Zool.: 108, 505-519.

Crawford R.J.M. (1984). Activity, group structure, and lambing of blue duiker Cephlophus monticola in the Tsitsikamma National Park, South Africa. South African Journal of Wildlife research: 14(3), 65-68.

Dubost G. (1980). L'écologie et la vie sociale du Céphalophe bleu (Cephalophus monticola Thunberg), petit ruminant forestier africain. Z. Tierpsychol.: 54, 205-266.

Dubost G. (1983a). Le comportament de Cephalophus monticola Thumberg et C. dorsalis Gray et la place des céphalophes au sein des ruminants, Part I. Mammalia: 47(2), 141-177.

Dubost G. (1983b). Le comportament de Cephalophus monticola Thumberg et C. dorsalis Gray et la place des céphalophes au sein des ruminants, Part II. Mammalia: 47(3), 281-310.

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.) (1989). Antelopes Global Survey and Regional Action Plans. Part 2: Southern and South-central Africa. IUCN/SSC Antelope Specialist Group.

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.

Estes R.D. (1991). The Behavior Guide to African Mammals. Including Hoofed Mammals, Carnivores, Primates. The University of California Press.

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.

Gautier-Hion A., Emmons L.H., Dubost G. (1980). A comparison of the diets of three major groups of primary consumers of Gabon (primates, squirrels and ruminants). Oecologia (Berlin): 45, 182-189.

Haltenorth T., Diller H. (1980). A field guide to the mammals of Africa, including Madagascar. Collins, London.

Heymans J., Lejoly J. (1981). Sur la répartition des Cephalophinae en foret ombrophile. Rev. Zool. Africaine: 95, 1-10.

Kingdon J. (1997). The Kingdon field guide to African Mammals. Academic Press, London and New York: Natural World.

Mills G., Hes L. (1997). The complete book of Southern African mammals. Struik Publishers.

Nummelin M. (1990). Relative habitat use of duikers, bush pigs, and elephants in virgin and selectively logged areas of Kebale Forest, Uganda. Tropical Zoology: 3, 111-120.

Rahm U., Christiaensen A. (1966). Les mammiferès de l'Ile Idjwi (Lac Kivu, Congo). Les mammifères de la foret equatoriale de l'est du Congo. Ann. Mus. Roy. Afr. Cent.: n° 149.

Rowe-Rowe D.T. (1994). The ungulates of Natal. Natal Parks, Game & Fish Preservation Board, Pietermaritzburg, Natal, R.S.A.

Skinner J.D., Smithers R.H.N. (1990). The mammals of the Southern African subregion. University of Pretoria, Pretoria.

Stuart C., Stuart T. (1997). Field guide to the larger mammals of Africa. Struik Publishers.

Tinley K.L. (1969). Dik-dik Madoqua kirki in South West Africa: Notes on distribution, ecology and behaviour. Madoqua: 1, 7-33.

Williams J.M., Mwinyi A.A., Ali R. (1996). A population survey of the three mini-antelope: Ader's duiker, Zanzibar blue duiker, and suni of Unguja, Zanzibar. Gnusletter: 15 (2), 6-7.

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.