Hyemoschus aquaticus [Ogilby, 1841].

Citation: Proc. Zool. Soc. Lond., 1840:35 [1841].

Type locality: Sierra Leone, Bulham Creek.

The taxonomic record (above) is taken from Wilson and Reeder (1993). Originally named Moschus aquaticus - thereby allying it with musk deer - the water chevrotain is thought to be the most ancestral of the extant tragulids (Robin, 1990; Wilson and Reeder, 1993). Three subspecies have been named (H. a. aquaticus, H. a. batesi, and H. a. cottoni), although the validity of these names is questionable (Wilson and Reeder, 1993; Kingdon, 1997).

Unusual for ungulates, female water chevrotains are larger than males, weighing (on average) over two kilograms more than the 10 kg males (Kingdon, 1997). Body length is approximately 85 cm, and shoulder height is roughly 35 cm (Robin, 1990).

The sleek coat is an overall rich reddish brown colour above and white on the undersides (Happold, 1973; Nowak, 1991; Kingdon, 1997). The body is marked with a striking pattern of horizontal white stripes running from the shoulder to the rump, with white spots on the back arranged in vertical rows (Nowak, 1991; Kingdon, 1997). The chin, throat, and chest are covered in coarse hair, and patterned with bold white inverted "v"s (Kingdon, 1997).

The hind quarters of Hyemoschus aquaticus are powerfully muscled and much higher than the shoulders, giving the body a distinctly sloped appearance (Happold, 1973; Robin, 1990; Kingdon, 1997). When walking, the head is held towards the ground, creating a profile which is a nearly perfect cone, allowing the water chevrotain to penetrate virtually impassable thickets (Dubost, 1979). The efficiency of this tunnelling profile is enhanced by a shield of thick, reinforced skin on the dorsal surface, which protects the back from injuries inflicted by dense, resistant vegetation (Dubost, 1979). This thick skin extends to the rump and throat, which also have deep muscles which may serve to reduce the incidence of severe injuries inflicted by the tusks during fights (Kingdon, 1997). The legs are short and rather delicate for the bulk of the body, while the hooves resemble those of swine with the dewclaws being held off the ground (Happold, 1973; Kingdon, 1997). There is a patch of shiny black skin behind the hocks (Kingdon, 1997). The tail is short with a fluffy white underside (Nowak, 1991; Kingdon, 1997).

The neck is short and thick (Kingdon, 1997). The small head is narrow and pointed, ending in a pointed, leathery nose with slit-like nostrils (Nowak, 1991; Kingdon, 1997). The ears are small and round (Kingdon, 1997). Neither sex has horns or antlers as defences, but like musk deer (Moschidae) and Chinese water deer (Hydropotinae), the upper canine teeth are well developed and sabre-like in males, protruding out of the mouth on either side of the lower jaw (Happold, 1973; Robin, 1990; Kingdon, 1997). Females also have enlarged canines, but they are shorter and blunter than in males (Kingdon, 1997). Male chevrotains possess unique glands under the chin in the angle of the lower jaw (Robin, 1990; Kingdon, 1997).

Due to the secretive nature of this species, little is known about its life cycle and reports vary dramatically. Females give birth to one offspring at a time, typically once every year (Dubost, 1978 in Nowak, 1991; Robin, 1990; Kingdon, 1997). Although the presence of four mammae in females indicates the potential for a larger litter size (Kingdon, 1979 in Nowak, 1991), no cases of twins have ever been reported (Dubost, 2016). Reports of gestation length are highly variable (4-9 months; see Kingdon, 1997 and Dubost, 1978 in Nowak, 1991), but Dubost (2016) provides two reliably-observed values of 219 and 272 days, as well as minimum gestations for five other females of 188, 200, 217, 231, and 233 days. The estous cycle averages 24 days in length (Dubost, 2016).

In Gabon, births occur throughout the year, although there is a peak in births during the first few months of the semiannual dry seasons in January and July-August (Dubost and Feer, 1992). These birthing peaks correspond to peaks in the quantity and quality (protein content) of fruits which this species feeds upon (Dubost and Feer, 1992). Dubost (2016) reports a wide range of birth weights from 11 surviving neonates (510 g-1,850 g), noting that this typically equates to 4.9-7.6% of the dam's mass. Infants are usually found separated from their mothers, "lying up" for the first three months of life (Dubost, 1978 in Nowak, 1991; Kingdon, 1997). During this initial hiding period, the mother will visit her offspring periodically for nursing and to wash the infant using her tongue (Robin, 1990; Kingdon, 1997)

Young animals are usually very sedentary, and rarely play since they never come in contact with others of the same age (Robin, 1990). Suckling lasts for 3-6, or even up to 9 months (Dubost, 1978 in Nowak, 1991; Kingdon, 1997). Individuals reach sexual maturity at 9-26 months of age, at which time young animals disperse from their mother's home range (Dubost, 1978 in Nowak, 1991). Growth continues until about 2 years of age, when full adult dentition is obtained (Kingdon, 1997). Water chevrotains typically do not survive past 8 years of age, but have a potential lifespan of 11-13 years (Robin, 1990; Kingdon, 1997).

The water chevrotain inhabits river valleys and lowland rainforests, and is rarely found more than 250 meters from a source of fresh water (such as a river, marsh, or lake) (Dubost, 1978 in Nowak, 1991; Kingdon, 1997). As with many small forest ungulates, the water chevrotain is strictly solitary (Robin, 1990; Kingdon, 1997). Adult females occupy home ranges averaging 13-14 hectares in size, and are typically accompanied by their latest offspring (Dubost, 1978 in Nowak, 1991). There is little overlap between the home ranges of neighbouring animals, and even when there is cohabitation there is typically very little interaction (Kingdon, 1997). Females usually settle down and remain in the same home range for life after they reach maturity (Dubost, 1978 in Nowak, 1991; Robin, 1990). Males are much less sedentary, usually occupying a given area for less than a year before moving on (Dubost, 1978 in Nowak, 1991). The home ranges of males are much larger than those of females, averaging 20-30 hectares in size and overlapping with the home ranges of at least two females (Dubost, 1978 in Nowak, 1991; Kingdon, 1997). There is no evidence of territoriality within home ranges, but nevertheless water chevrotains are well-spaced (Dubost, 1978 in Nowak, 1991). Recorded population densities vary between 7.7 to 28.0 animals per square kilometer (Dubost, 1978 in Nowak, 1991).

Water chevrotains are hunted by most carnivores which share the same habitat, with young animals also being taken by both nocturnal and diurnal birds of prey (Robin, 1990). When in the vicinity of a predator, "freezing" is the typical response of the water chevrotain, in the hopes of going undetected (Kingdon, 1997). If seen and pursued, this species retreats to water (Kingdon, 1997). As its name suggests, H. aquaticus is quite comfortable in the water, and can dive and swim beneath the surface, although only for short periods before tiring (Kingdon, 1997). If a threat persists, water chevrotains may hide almost completely submerged (Happold, 1973).

H. aquaticus forages primarily in mature forest, along forest edges, and in secondary forest, with much less feeding activity in waterside and flooded habitats (Dubost, 1984). Scent is the primary sense used when searching for food (Kingdon, 1997). The water chevrotain is primarily a frugivore - stomach content analysis of 19 animals in Gabon revealed that fruits comprise 68.7% of all foods eaten (by dry weight - Gautier-Hion et al., 1980; Dubost, 1984). The rest of the diet is comprised of leaves (9.9%), petioles and stems (20.5%), animal matter (0.14%), flowers (0.70% ), and fungi (0.13% ), with no tree gums being consumed (Gautier-Hion et al., 1980; Dubost, 1984). Compared to duikers (Cephalophinae; other small ungulates which share the same habitat), H. aquaticus eats relatively little fruit and fungi (the diet of duikers may contain upwards of 80% fruit), but many more succulent stems (Dubost, 1984).

76 species of fruits have been identified in the diet of H. aquaticus, and many more are eaten (Dubost, 1984). Dubost (1984) found several species to be preferred - namely Cylindropsis parvifolia (Apocynaceae), Bombax buonopozense (Bombacaceae), Alchornea cordifolia (Euphorbiaceae), Coelocaryon preussi or Pycnanthus angolensis (Myristicaceae), and Cissus dinklagei (Vitaceae). Kingdon (1997) suggested that figs (Ficus), Pseudospondias fruits, palm nuts (Elaeis), and breadfruit (Treculia) are consumed, as well as the fruits of gingers and arrowroots. Most fruits consumed by H. aquaticus is a diameter between 0.5 and 2.0 cm (Dubost, 1984).

Most of the animal matter eaten by the water chevrotain is insects - this species actively hunts for ants by licking the ground along ant trails (Dubost, 1984). However, crabs, carrion, and scavenged fish have also been noted (Kingdon, 1997). The water chevrotain consumes significantly less animal matter and fungus during the dry season, as well as 44% fewer fruit species (Dubost, 1984). Young individuals which are still nursing eat smaller amounts of fruit than adults (only 48.4% of the diet) and a larger proportion of leaves (31.3%) (Dubost, 1984). In these unweaned animals, stems comprise 19.1% of stomach contents, while flowers make up only 0.80% (Dubost, 1984).

H. aquaticus is exclusively nocturnal, being active between the hours of 1800 and 0600 (Dubost, 1978 in Nowak, 1991; Robin, 1990). Foraging in clearings at night, H. aquaticus retires to a hiding spot in dense cover during the day (Kingdon, 1997). Resting postures include lying down and "sitting" on the hind legs with front legs propping the body up (Robin, 1990)

Due to their solitary nature, interactions between water chevrotains are restricted to agonistic and reproductive encounters. Males fight more frequently than females, principally over territory (Robin, 1990; Kingdon, 1997). Fights are typically short in duration, and involve the two competing males rushing at each other with mouths open, poking at each other with their muzzles and biting, using the canines in the upper jaw and incisors in the lower jaw (Robin, 1990; Kingdon, 1997). These fights may be responsible for the fact that mature males live up to several kilometers apart (Kingdon, 1997).

The water chevrotain has several vocalizations, including a scream when wounded, and an alarm bark (Kingdon, 1997). When fighting, females produce a high pulsing chatter (Kingdon, 1997). As with pigs, male chevrotains vocalize when following an estrus female, typically through a closed mouth (Kingdon, 1997). While being followed, a receptive female will stop at each cry, allowing the male to lick her rump. After several repetitions of this, the male mounts (Kingdon, 1997).

The west and central rainforest block from Sierra Leone to Uganda.

Countries: Angola, Benin?, Burkina Faso?, Burundi, Cameroon, Central African Republic, Congo, The Democratic Republic of the Congo, Côte d'Ivoire, Equatorial Guinea, Gabon, Ghana, Guinea, Guinea-Bissau?, Liberia, Nigeria, Rwanda, Senegal?, Sierra Leone, Togo?, Uganda (IUCN Antelope Specialist Group, 2003).

The estimated total population of the water chevrotain is 278,000 (East, 1999). The IUCN Antelope Specialist Group (2008) has assigned the status of "Least concern" to the water chevrotain. Due to its secretive nature, there is little information on its status in individual countries within its extensive range, although there is some evidence that it is declining in specific areas (IUCN Antelope Specialist Group, 2008). Major threats to the survival of this species include loss of habitat to agriculture and expanding human development, as well as hunting for food by humans (IUCN Antelope Specialist Group, 2008). The population of H. aquaticus in Ghana was formerly listed on CITES Appendix III (2003), but this species in no longer present in any appendix (CITES, 2009).

The genus name Hyemoschus is derived from the Greek Hus, a hog, and Moschus, the genus of the musk deer (derived from the Greek word for musk). This species was originally classified as small musk deer due in part to the long canines of the males, but its stature and habits are reminiscent of pigs. Aquaticus (Latin) living in or near water - this species is rarely found far from water, which it dives into to escape from predators. Chevrotain is a diminutive form of the French chèvre, a goat.

Local names

Giminan [Dyula] (Happold, 1973)

Diaure ndiyam [Fula/Fulani] (Happold, 1973)

Isè [Yoruba] (Happold, 1973)

 

French

Chevrotain aquatique, chevrotain africain (Robin, 1990)

 

German

Afrikanisches Hirschferkel (Robin, 1990), Zwergmoschustier (Happold, 1973).

 

Spanish

Antilope amizclero enano de agua (IUCN Antelope Specialist Group, 2008)