 Cephalophus
ogilbyi
Ogilby's duiker |
Taxonomy | Description
| Reproduction | Ecology
| Behavior | Distribution
| Conservation | Remarks
| Literature |
| Taxonomy
-
Cephalophus ogilbyi [Waterhouse, 1838].
-
Citation: Proc. Zool. Soc. Lond., 1838:60.
-
Type locality: Equatorial Guinea, Fernando Po (= Bioko).
The taxonomic record (above) is taken from Wilson and Reeder (1993).
Cephalophus ogilbyi is included in the subgenus Cephalophorus
[Gray, 1842] (Nowak, 1991). Two subspecies of Ogilby's duiker
are currently recognized: C. o. ogilbyi (Nigeria, Cameroon, and Bioko
Island [Equatorial Guinea]) and the white-legged duiker C. o. crusalbum
(Gabon and Congo-Brazzaville) (East, 1999). A third subspecies, C.
o. brookei from west Africa, is now treated as distinct species: Brooke's
duiker, C. brookei (see East, 1999). Kingdon (1997) treated
the mainland specimens of C. o. ogilbyi as C. o. brookei, confining
the nominate subspecies C. o. ogilbyi to Bioko Island. C.
o. crusalbum was originally classified as a form of C. leucogaster,
but was identified as a variety of Ogilby's duiker by Grubb in 1978. This
species may be a form of bay duiker, Cephalophus dorsalis, which it
closely resembles in the field (see Wilson, 1987; East, 1999).
General Characteristics
Ogilby's duiker has the typical crouched duiker form, with massive hindquarters
and a deep slab-sided body (Kingdon, 1997). Head and body length is
85-115 cm (Kingdon, 1997). Of the measurements for C. o. crusalbum
reported by Grubb (1978), one male and one female specimen were
significantly larger than the rest of the specimens examined - total lengths
fell between 96.5-104.1 cm when these outliers were excluded. Shoulder
height is approximately 55 cm, and adult weight is between 14 and 20 kg (Kingdon,
1997). Tail length is usually between 12 and 15 cm (Kingdon, 1997).
Reported measurements for Ogilby's duiker (Cephalophus ogilbyi) |
| Source |
Adult Weight |
Head & Body Length |
Shoulder Height
|
Tail Length |
Grubb, 1978
(for C. o. crusalbum) |
- |
96.5-145.0 cm
100.3-146.0 cm  |
- |
13.2-16.4 cm |
| Happold, 1987 |
20 kg |
90 cm |
56 cm |
15 cm |
| Kingdon, 1997 |
14-20 kg |
85-115 cm |
55-56 cm |
12-15 cm |
| Walther, 1990 |
14-18 kg |
85-115 cm |
55 cm |
12-15 cm |
| Wilson, 1987 |
14-20 kg |
85-115 cm |
- |
12-15 cm |
The overall pelage color of Cephalophus ogilbyi is a deep golden brown,
chestnut, or mahogany (Happold, 1987; Kingdon, 1997). The coat is infused
with grey hairs, especially on the back (Grubb, 1978). The body color
deepens on the rump and hindquarters, but is lighter on the sides and even
paler on lower flanks (Grubb, 1978). The ventral pelage is a pale golden
brown or light grey (Grubb, 1978; Happold, 1987). The hair is generally
sparse on the body, with the result that the observed color is a combination
of hair and skin tones (Grubb, 1978). A well-defined black stripe runs
down the spine, although it is variable in its extent (usually about 3-6
cm wide from the shoulders to the base of tail) (Grubb, 1978; Happold,
1987; Kingdon, 1997). This midline stripe narrows to less than 1 cm
at the base of the tail (Gautier-Hion and Gautier, 1994). Scattered black
hairs on midline continue this dorsal stripe forward between the shoulders
and up the neck (Happold, 1987).
The legs vary in color depending on the subspecies and region, but are long
compared to other heavy-set duikers (Kingdon, 1997). C. o.
crusalbum, as its name suggests, appears to be wearing white "stockings"
on its lower legs, which are highly conspicuous when the duiker flees
(Gautier-Hion and Gautier, 1994). The white color of the front legs
extends upwards on the inside to the axillary region (Grubb, 1978). In
other populations of Ogilby's duiker the legs are golden-brown, generally
darkening in color towards the hooves (Happold, 1987). A narrow dark
brown stripe runs down the front of the forelegs (Grubb, 1978). There
is a white ring on the pastern (just above hoof) (Walther, 1990). The
tail is short and colored orange-ochre like body, with the median black stripe
continuing down its dorsal aspect (Grubb, 1978; Kingdon, 1997). Longer
white hairs are present on underside of the tail (Grubb, 1978). The
tail terminates in a tuft about 7.5 cm long which is narrow and grey-brown
(Grubb, 1978)
The neck, forequarters, and outside of the forelimbs are grey in color, paling
to whitish grey on underside of neck (Grubb, 1978). The overall coloration
of the head is greyish, with many short black hairs and relatively few ochre
ones (Grubb, 1978). The muzzle is black, contrasting with the throat
and lower jaw, which are whitish (Grubb, 1978). Two chestnut arches
over the eyes ("eyebrows") are one of the most conspicuous features of this
duiker (Gautier-Hion and Gautier, 1994; Kingdon, 1997). There is a
dark ochre-colored patch surrounding the preorbital glands (Grubb, 1978).
The forehead is bright rufous in color, darkening towards the forehead
tuft located between the horns (Happold, 1987). This forelock, relatively
sparse compared to other duikers, is dark brown or rufous-black in color
(Happold, 1973; Walther, 1990; Gautier-Hion and Gautier, 1994). The
backs of the ears are covered with very short, sparse black hairs, while
several bands of white hair on the inner surface of the ear form a
conspicuous pattern (Gautier-Hion and Gautier, 1994). The internal
edges of the ears are sprinkled with orange-ochre hairs, a continuation of
the forehead coloration (Gautier-Hion and Gautier, 1994)
Horns are present in both sexes, and, unusual for duikers, are concave, curving
upwards (Walther, 1990; Kingdon, 1997). The horns are thickset and
possess several roughened rings on basal half (Happold, 1987; Kingdon, 1997).
In males they grow 8-12 cm long while in females they are significantly
shorter, only about 4 cm in length (Walther, 1990). Grubb (1978) found
the horns of C. o. crusalbum males to be 8.7-10.9 cm long (n=4), and
between 4.8 and 5.7 cm long for females (n=3). Average horn length
for C. o. ogilbyi was 8.90 cm for males (n=11) and 5.95 cm for females
(n=6) (Grubb, 1978).
Ontogeny and Reproduction
The growth, development, and breeding of Ogilby's duiker has not yet been
studied.
Ecology and Behavior
Ogilby's duiker inhabits primary rainforest habitats, usually with a closed
canopy (Happold, 1987; Kingdon, 1997; Newing, 2001). On Bioko Island,
in the absence of other medium-sized and large duikers, this species has
expanded its niche to include not only lowland forest but also
Schefflera-dominated forest and montane forest (800-1,200 m) (East,
1999).
All observations of C. ogilbyi made by Gautier-Hion and Gautier (1994)
were of solitary individuals or pairs. These sightings, made during
daylight hours, were of active individuals, suggesting that this species
is diurnal (Gautier-Hion and Gautier, 1994). This is supported by
observations of a captive juvenile at the Monrovia Zoo, Liberia, which was
active for 58 % of daylight hours (0630-1800) and only 17 % of the night
hours (1830-0600) (Newing, 2001). Although Ogilby's duiker may compete
with the nocturnal bay duiker, the effects of this competition may be mediated
by temporal separation (Kingdon, 1997; Newing, 2001).
C. ogilbyi feeds primarily on fallen fruits (Kingdon, 1997).
Gautier-Hion and Gautier (1994) observed a subadult C. o.
crusalbum eating the hard fruits of Klainedoxa gabonensis. One
Ogilby's duiker's stomach contents examined by Newing (2001) was composed
of 92% fruits and seeds, 7% vegetative parts, and 1% flowers. This
species is often found under trees in which monkeys are feeding, consuming
fruits, seeds, and flowers which fall to the ground as a result of the primates'
activity (Gautier-Hion and Gautier, 1994). Kingdon (1997) suggests
that the distribution of Ogilby's duiker may be influenced by the super-abundance
of fibrous fruits and the abundance of primates which contribute to fruit
fall. C. ogilbyi may "raid" farmlands at night (Newing, 2001).
Distribution
Ogilby's duiker is patchily distributed within its range (Kingdon, 1997).
It is a common and dominant species on Bioko Island, especially on
the relatively undisturbed upper slopes of mountains (Kingdon, 1997)
Countries: Cameroon, Congo, Equatorial Guinea [Bioko Island], Gabon,
Nigeria (IUCN, 2000).
Range Map (Redrawn from IAE, 1998)
Conservation Status
Ogilby's duiker is classified as a low risk, near threatened species by the
IUCN (2002), and is listed on CITES Appendix II (CITES, 2003). The
total population of Ogilby's duiker is estimated at 30,000 individuals, with
roughly 12,000 C. o. ogilbyi and 18,000 C. o. crusalbum (East,
1999). The major threats to survival are habitat loss due to agriculture
and hunting for the bushmeat trade (IUCN, 2002). This species is highly
susceptible to overhunting (East, 1999).
Remarks
The genus Cephalophus is derived from kephale (Greek), the
head, and lophus (Greek), a crest, referring to the prominent tuft
of hair on the forehead of most duiker species. The common name duiker
("DIKE-er") is Afrikaans for "diver" or "diving buck", a reference to the
species' characteristic flight into the undergrowth when alarmed (Wilson,
1987).
-
-
French
-
Céphalophe d'Ogilby (IUCN, 2002)
-
-
German
-
Ogilbyducker (Kingdon, 1997)
-
-
Spanish
-
Duiquero de Ogilby (IUCN, 2002)
|
Literature
Cited
CITES (Convention on the International Trade in Endangered Species of Wild
Flora and Fauna). 2003. Appendix I, II, and III as adopted by the Conference
of the Parties, valid from 13 February 2003. Available online at
http://www.cites.org/
East, R. [compiler]. 1999. African Antelope Database 1998. IUCN/SSC
Antelope Specialist Group. Gland, Switzerland and Cambridge, UK: IUCN.
Gautier-Hion, A., and J. Gautier. 1994. Cephalophus ogilby
crusalbum Grubb 1978, described from coastal Gabon, is quite common in
the Foret-Des-Abeilles, central Gabon. Revue de Ecologie (La Terre et la
Vie); 49(2): 177-180.
Grubb, P. 1978. A new antelope from Gabon. Zoological Journal
of the Linnean Society; 62: 373-380.
Happold, D. C. D. 1973. Large Mammals of West Africa. London:
Longman Group, Ltd.
Happold, D. C. D. 1987. The Mammals of Nigeria. Oxford: Clarendon Press.
IEA (Institute of Applied Ecology) 1998. Cephalophus ogilbyi.
In African Mammals Databank - A Databank for the Conservation
and Management of the African Mammals Vol 1 and 2. Bruxelles: European
Commission Directorate. Available online at
http://www.gisbau.uniroma1.it/amd/amd022b.html
IUCN (International Union for Conservation of Nature and Natural Resources).
2002. 2002 IUCN Red List of Threatened Species. Available
online at http://www.redlist.org/
Kingdon, J. 1997. The Kingdon Field Guide to African Mammals.
London and New York: Academic Press, Natural World.
Newing, H. 2001. Bushmeat hunting and management: implications
on duiker ecology and interspecific competition. Biodiversity and
Conservation 10(1): 99-108.
Nowak, R. M. [editor]. 1991. Walker's Mammals of the World (Fifth Edition).
Baltimore: The Johns Hopkins University Press.
Walther, F. R. 1990. Duikers and Dwarf Antelopes.
In Grzimek's Encyclopedia of Mammals, Volume 5. Edited
by S. P. Parker. New York: McGraw-Hill. pp. 325-343.
Wilson, D. E., and D. M. Reeder [editors]. 1993. Mammal Species of the World
(Second Edition). Washington: Smithsonian Institution Press.
Available online at
http://nmnhwww.si.edu/msw/
Wilson, V. J. [compiler] 1987. Action plan for duiker conservation -
IUCN/SSC Antelope Specialist Group and Chipangali Wildlife Trust.
Additional Resources
Colell, M., C. Mate, and J. E. Fa. 1994. Hunting among Moka Bubis
in Bioko: Dynamics of faunal exploitation at the village level.
Biodiversity and Conservation; 3(9): 939-950.
East, R. [editor]. 1990. Antelopes Global Survey and Regional
Action Plans. Part 3: West and Central Africa. IUCN/SSC Antelope Specialist
Group.
East, R. [editor]. 1996. Antelope survey update. IUCN/SSC Antelope
Specialist Group: n° 2.
Eves, H. 2000. Duikers: A primary target for Africa's bushmeat trade.
Animal Keepers' Forum 27(11): 497-505.
Fa, J. E., J. Juste, J. Perez Del Val, and J. Castroviejo. 1995.
Impact of market hunting on mammal species in equatorial Guinea.
Conservation Biology; 9(5): 1107-1115.
Fa, E. J., E. J. Yuste, and R. Castelo. 2000. Bushmeat Markets
on Bioko Island as a Measure of Hunting Pressure. Conservation Biology;
14(6): 1602-1613.
Haltenorth, T., and H. Diller. 1980. A Field Guide to the Mammals
of Africa, including Madagascar. London: Collins.
van Vuuren, B. J., and T. J. Robinson. 2001. Retrieval of four
adaptive lineages in duiker antelope: Evidence from mitochondrial DNA sequences
and fluorescence in situ hybridization. Molecular Phylogenetics and
Evolution 20(3): 409-425.
Wilson, V. J., and B. L. P. Wilson. 1990. Notes on the duikers
of Sierra Leone. Arnoldia-Zimbabwe 9(33): 451-462.
|
|
