Cephalophus zebra [Gray, 1838].

Citation: Ann. Nat. Hist., 1:27.

Type locality: Sierra Leone.

The taxonomic record (above) is taken from Wilson and Reeder (1993). Synonyms for Cephalophus zebra include C. doria, C. doriae, and C. zebrata (Wilson, 1987; Wilson and Reeder, 1993; Kingdon, 1997). This duiker is the only member of the subgenus Cephalophula [Knottnerus-Meyer, 1907], and is monotypic (Nowak, 1991; Kingdon, 1997).

This stocky, muscular duiker is easily distinguished from all other duikers - and indeed all other ungulates - by its dramatic coloration. Its distinctive black stripes are superficially similar to those of the now extinct thylacine or Tasmanian tiger (Thylacinus cynocephalus), and several putative thylacine skins have, in fact, come from this duiker. The zebra duiker is one of the smaller members of the genus Cephalophus (Wilson, 2001). Average weights reported by Wilson (2001) are 17 kg for males and 18 kg for females. Body length is 85-90 cm, shoulder height averages 45 cm, and the tail is approximately 15 cm in length.

The zebra duiker has one of the most distinctive coats of any mammal: the light gold or reddish-brown color of the body is punctuated by twelve to sixteen black (sometimes dark brown) transverse stripes; this array of stripes begins behind the shoulders and continues to the root of the tail (Schweers, 1984; Kingdon, 1997; Wilson, 2001). Each stripe is widest at the spine and tapers as it runs vertically down the flanks; each stripe ends at approximately the same level on the the flanks (Wilson, 1987; Walther, 1990; Kingdon, 1997). The arrangement of stripes is unique to each individual. The undersides, including the belly, chest, and throat, are pale (gold to nearly white) and lack stripes, while the head, nape of the neck, shoulders, and lower legs are a deep russet or chestnut color (Happold, 1973; Schweers, 1984; Kingdon, 1997; Wilson, 2001). The upper legs have dark garter-like markings; on the hind legs, these bands cover a tufted gland just distal to the hocks (Kingdon, 1997). The tail is often the same rufous as the rump (sometimes distinctly paler), with white hairs on the underside (Happold, 1973; Wilson, 2001).

The face is a deep chestnut brown color, save for the muzzle which is black (Kingdon, 1997). The lower jaw is white and may be "flashed" during social interactions (Schweers, 1984). There is a reduced forehead crest of darker hairs, and the skull in this region is heavily reinforced with thick bone (Happold, 1973; Walther, 1990; Kingdon, 1997; Wilson, 2001). Both sexes grow horns, which are robust, conical, and sharply pointed (Kingdon, 1997). The horns are short, growing 4-5 cm long in males and no more than 2-3 cm in females (Walther, 1990; Wilson 2001).

The reproducive biology of zebra duikers has been well-studied in captive specimens. Schweers (1984) reports the duration of estrus as 0.5-1 days, and the presence of a post-partum estrus that allows females to conceive within ten days of giving birth. In these specimens (observed at the Frankfurt Zoo), gestation period was 221-229 days and interbirth interval averaged 241 days, allowing this species to breed year-round. A single young is typical (Schweers, 1984). Details of courtship are given in the behavior section.

Just prior to giving birth (approximately two days in advance), the vulva becomes swollen; the tail, which is held away from the body a few weeks before parturition, is curved into an exaggerated s-shape to reduce contact with the genital region (Schweers, 1984; Udell, 1981). During labor, the dam lays down and rises repeatedly, with the birth usually occurring while standing (Schweers, 1984). Four out of five births observed by Schweers (1984) occurred between 0900 and 1100 hours. Udell (1981) estimated the weight of a zebra duiker at birth to be 1.8 kg, Barnes et al. (2002) report birth weights ranging from 1.27-1.75 kg [average 1.48 kg], and Schweers (1984) estimated birth weights to be 1.5-1.6 kg. This is relatively heavy for larger mammals, comprising about 10% of the maternal body weight (Schweers, 1984). Males are slightly heavier than females at birth (Barnes et al., 2002).

Immediately after birth, the mother licks the amniotic sac off of the youngster and will also eat the afterbirth once it is passed (Schweers, 1984). Young zebra duikers are born with their characteristic striping pattern, but the stripes are very close together, giving the youngster an overall darker appearance and a rather bluish cast to their coat (Schweers, 1984). The head and lower legs are dark brown in neonates (Schweers, 1984). Like most young antelope, the legs are long in proportion to the body (Schweers, 1984). The skin of juveniles is softer than that of adults, and the sensory hairs on the face appear longer (Schweers, 1984).

Zebra duiker calves are precocious, but act as "hiders", lying up in one place for 2-3 weeks after being born (Udell, 1981; Schweers, 1984). They are able to nurse within 15-30 minutes of being born, and for the first few weeks will nurse about four times per day, each session lasting several minutes (Udell, 1981; Schweers, 1984). Zebra duikers grow quickly: Barnes et al. (2002) report typical weights of 1.71-2.2 kg at 8-10 days old, 2.85-3.60 kg at 25-30 days, and 3.62-4.62 kg at 40-45 days.

Calves begin to nibble on solid food after one week, and captive hand-reared zebra duikers have been weaned at 95 days of age (Udell, 1981; Barnes et al., 2002). In the mother-reared duikers studied by Schweers (1984), the last attempts at nursing occurred at approximately 120 days of age, although successful attempts had ceased a few weeks earlier. Horn growth commences at one to two months of age, and the darker neonatal coloration begins to lighten at about two months (Udell, 1981; Schweers, 1984). Juveniles aged 7-9 months usually have their adult coloration and have reached their adult height, but can still be differentiated from adults by their delicate figures (Schweers, 1984). Males reach sexual maturity at about 2 years of age (Barnes et al., 2002). In captivity, lifespans of 11-13 years have been recorded (Weigl, 2005)

The zebra duiker is a forest-dependent species, found mostly in closed canopy primary forests (Wilson, 2001). There are records of the species in forest margins, clearings, and secondary growth, but these are relatively scarce; there is little evidence to suggest that it inhabits farmbush (Kingdon, 1997; Newing, 2001; Wilson, 2001). East (1999) gives a generalized population density of 0.2-2.0 individuals per km².

Zebra duikers feed primarily on fruits, but do not appear to be specialized into a specific dietary niche (Kingdon, 1997). Four zebra duiker stomachs examined by Wilson (2001) showed a large proportion of fruits and seeds in the diet (79%). The fruits of Diospyros sanza-minika were found in all stomachs examined; other species identified in the diet include Bussea occidentalis, Eremospatha macrocarpa, and Tetraberlinia tubmaniana. Kingdon (1997) suggests that this species may use its forehead to crack open larger thick-shelled fruits. Newing (2001) reports farmlands adjacent to forest are occasionally visited to feed on crops. Zebra duikers in both the wild and captivity have been observed consuming rodents; such omnivory occurs in many duiker species (Schweers, 1984; Wilson, 2001). Captive individuals have an apparent increased requirement for dietary copper compared to other duikers (Farst et al., 1980).

Observations of captive specimens at the Monrovia Zoo, Liberia, suggest that the zebra duiker is diurnal, being active about 71% of the daylight hours and less than 10% of the night (Newing, 2001). This is supported by an obervation of wild duikers foraging at midday (Davies, 1987 in Wilson, 2001).

Breeding pairs are believed to be the normal social unit: strong bonds form between captive pairs and are reinforced with 'friendly' interactions such as mutual rubbing, licking, and scent-marking (Udell, 1981; Kingdon, 1997). In the wild, Kingdon (1997) suggests that both sexes may defend a territory against competitors, and may also take an active role in defending their offspring. It has been inferred from heavy facial scarring that fighting is especially vigorous in this species, and it has been proposed that the distinctive stripes may serve as a focus for social interactions, reducing the likelihood of being gored in the abdomen.

The following account on the breeding behavior of the zebra duiker is summarized from the detailed study conducted by Schweers (1984) at the Frankfurt Zoo. Males determine the reproductive status of females by smelling urine with a characteristic flehmen response, curling the upper lip and opening the mouth. In the days leading up to sexual receptivity, males apply secretions from the preorbital glands to the legs, head, neck, and back of the female with increasing frequency, a behavior also noted by Udell (1981). In the wild, this may signal to other males that the female in question is being courted by another male.

Courtship is relatively simple, with the male walking swiftly behind the female while licking at her neck, hind legs, and anogenital region (this driving behavior may occur even when the female is not receptive). While being pursued, a female will keep her head low and stretched forward, with the ears folded back. The male usually runs directly behind, stretching his head forward such that his neck is horizontal and the head is held at height the female's tarsal gland (see also Udell, 1981). During the driving phase of courtship, the male (and sometimes the female) makes throaty grunting sounds (also reported by Udell, 1981).

Initial mounting attempts may occur without the female stopping, and she may speed up her pace to prevent successful intromission. As receptivity increases, the female's pace slows and the number of stops increases, allowing the male increased opportunity to mount. If she is not yet receptive, the male may lift up a front leg and press it against the female's body for an extended period of time; this is usually followed by the male tapping the female with his lips in order to restart the pursuing phase. Mounting is initiated by the male smelling and licking the female's anogenital region, followed by pushing his chin onto her croup. A ritualized high lifting of the foreleg occurs briefly before each mounting attempt; this kick is aimed past the hind legs of the female (rather than in between the legs as with the laufschlag of gazelles). Copulation attempts are brief, lasting only a few seconds, but are repeated frequently (see Udell, 1981). Successful breeding was not observed by Schweers (1984), who suggests that this likely occurred at night.

From Sierra Leone (east of the Moa River) to the Cote d'Ivoire (west of the Niouniourou River), commonest in central Liberia (Kingdon, 1997).

Countries: Côte d'Ivoire (Ivory Coast), Guinea, Liberia, and Sierra Leone (IUCN SSC Antelope Specialist Group, 2008).

The IUCN has classified the zebra duiker as vulnerable (IUCN SSC Antelope Specialist Group, 2008). It is listed on CITES Appendix II (CITES, 2012). The total population was estimated by East (1999) at 28,000 individuals, spread across 30,000 km², although Wilson (2001) suggests that an upper population figure of 15,000 is more realistic. This species is threatened by poaching for meat and the continued destruction of West Africa's remaining primary rainforests (East, 1999). Their long-term survival is dependent on protected areas to safeguard against habitat loss and to control of hunting (East, 1999).

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). The genus is from kephale (Greek: the head) and lophus (Greek: a crest), referring to the tuft of hair on the forehead of most duikers. The species name zebra is a clear reference to the prominent black stripes on the zebra duiker's body.

Local names

Were [Fulani] (Happold, 1973)

Nemmeh [Sapo] (Wilson, 2001)

Mountain deer, marked deer [in Liberia] (Wilson, 2001)

 

French

Céphalophe zèbre, Céphalophe rayé (Walther, 1990; Kingdon, 1997)

 

German

Zebraducker, Streifenducker (Wilson, 2001)

 

Spanish

Duiquero cebrado (Wilson, 2001)