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). Three subspecies of Ogilby's duiker are currently recognized: Ogilby's duiker, C. o. ogilbyi (from Nigeria, Cameroon, and Bioko Island, Equatorial Guinea); Brooke's duiker, C. o. brookei (from West Africa); and the white-legged duiker, C. o. crusalbum (from Gabon and Congo) (East, 1999). All three subspecies are sometimes treated as distinct species. Kingdon (1997) treated the mainland specimens of C. o. ogilbyi as C. o. brookei, confining the nominate subspecies 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 (1978).

Ogilby's duiker has the typical muscular hindquarters and crouched form of duikers. Head and body length are usually 85-115 cm, although Grubb (1978) reports two specimens of C. o. crusalbum (one male, one female) with head-body length of approximately 145 cm. Shoulder height is approximately 55 cm, and adult weight is between 14 and 20 kg. Tail length is typically 12-15 cm.

The overall coloration of Ogilby's duiker is golden brown, chestnut, or mahogany, tending to be paler than other red duikers (Happold, 1987; Kingdon, 1997; Wilson, 2001). The body color is deepest on the rump and hindquarters; on the flanks, the golden body color fades gradually into the pale golden brown or light grey of the belly (Grubb, 1978; Happold, 1987). The pelage is sparse, and the general color is thus a combination of hair and skin tones (Grubb, 1978). A well-defined thin black stripe runs down the midline of the back (Grubb, 1978; Happold, 1987; Kingdon, 1997). In C. o. ogilbyi, it is very narrow (1.0-3.0 cm) and runs from the shoulders to the tail (Grubb and Groves, 2001). In C. o. brookei, the width is greater, usually 2.7-6.6 cm, but it narrows to a point before reaching the base of the tail (Grubb and Groves, 2001). In C. o. crusalbum the stripe (2.5-6.0 cm in width) extends to the tip of the tail (Grubb and Groves, 2001). In all subspecies, scattered black hairs on midline may continue the dorsal stripe cranially 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). The white-legged duiker (C. o. crusalbum), as its name suggests, has distinctively white lower legs; this feature is 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 of all three subspecies, and a white ring is present just above hoof (Grubb, 1978; Walther, 1990). The tail is short and colored orange-ochre like body except for the median black stripe (where present, see above) (Grubb, 1978; Kingdon, 1997). Longer white hairs are present on underside of the tail, while the tip of the tail bears a distinct terminal tuft of mixed white, black, and brown hairs (Grubb, 1978; Wilson, 2001).

The face is either ochre or grayish (Grubb, 1978; Wilson, 2001). 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). 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, may be rufous to dark brown in color (Gautier-Hion and Gautier, 1994; Happold, 1973; Walther, 1990; Wilson, 2001). 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 (Gautier-Hion and Gautier, 1994).

Short, upward-curving horns are present in both sexes (Walther, 1990; Kingdon, 1997). The horns are thick and possess several roughened rings on their basal halves (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) reports horn lengths for male C. o. crusalbum as 8.7-10.9 cm (n=4) and for females: 4.8-5.7 cm (n=3). Average horn lengths for C. o. ogilbyi are 8.90 cm for males (n=11) and 5.95 cm for females (n=6) (Grubb, 1978).

The growth, development, and breeding of Ogilby's duiker has not yet been studied. Juveniles are reportedly speckled (Grubb and Groves, 2001).

Ogilby's duiker inhabits primary rainforest habitats, usually with a closed canopy, although it may be found in secondary forest as well (Happold, 1987; Kingdon, 1997; Newing, 2001; Wilson, 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 (East, 1999).

On Bioko, Ogilby's duiker may fall prey to drills (Mandrillus leucophaeus) and rock pythons (Python sebae) (Butynski, Schaaf, and Hearn, 2001). On the mainland, leopard (Panthera pardus) and golden cats (Profelis aurita) are known to feed on forest duikers.

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, and Newing (1994) observed a juvenile Brooke's duiker feeding on Coelocaryon oxycarpum fruits. One Ogilby's duiker's stomach contents examined by Newing (1994) in Côte d'Ivoire was composed of 92% fruits and seeds, 7% vegetative parts, and 1% flowers. Plant species in this stomach included Dialium aubrevillei, Nauclea sp., Scottelia chevalieri, Coelocaryon oxycarpum, and the seeds of Diospyros sp. and Amphimas pterocarpoides. Ogilby's duiker is often found under trees in which monkeys are feeding, consuming fruits, seeds, and flowers that 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).

Ogilby's duiker is primarily solitary (Wilson, 2001). All observations of C. o. crusalbum 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. This is supported by observations of a captive juvenile C. o. brookei 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). Payne (1992, in Wilson, 2001) observed a similar trend in a radio-collared male Ogilby's duiker in Korup National Park, Cameroon: a marked decrease in activity was observed at sundown, and a resumption in activity did not occur until sunrise. There was often a decrease in activity during midday. 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).

Little else is known of the habits of Ogilby's duiker. The male collared by Payne (1992 in Wilson, 2001) had a home range of 0.106 km²; the core of this area was frequently used for sleeping at night. Several other individuals were seen within this home range, although the majority were at the periphery. It is unknown whether territoriality is involved. Latrine areas appear to be used (Wilson, 2001).

The principal vocalization is a "wheet" call, which is very similar to the calls of other duikers, including Peters's duiker (Cephalophus callipygus) (Butynski, Schaaf, and Hearn, 2001).

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, where it has been recorded at elevations of 2,260 m (Butynski, Schaaf, and Hearn, 2001; Kingdon, 1997).

Countries: Cameroon, Congo, Côte d'Ivoire, Equatorial Guinea (restricted to Bioko Island), Gabon, Ghana, Guinea, Liberia, Nigeria, Sierra Leone (IUCN SSC Antelope Specialist Group, 2008).

Ogilby's duiker is classified as least concern by the IUCN (2008) and both C. ogilbyi and C. (o.) brookei are listed on CITES Appendix II (CITES, 2012). The total population of Ogilby's duiker is estimated at 35,000 individuals, with roughly 12,000 C. o. ogilbyi, 18,000 C. o. crusalbum, and only 5,000 C. o. brookei (East, 1999). The major threats to survival are habitat loss due to agriculture and hunting for the bushmeat trade (IUCN, 2012). This species is highly susceptible to overhunting (East, 1999).

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).

Local names

Odabohene [Asanti] (Wilson, 2001)

N'Chumjbi [from Fernan Vaz, Gabon] (Wilson, 2001)

 

French

Céphalophe d'Ogilby (IUCN, 2008)

 

German

Ogilbyducker (Kingdon, 1997)

 

Spanish

Duiquero de Ogilby (IUCN, 2008)