The water chevrotain has a disjunct distribution, from Sierra Leone to Ghana , and from Nigeria to former Zaire , marginally entering Uganda . A first rough distribution map was obtained from Kingdon (1971-77), subsequently revised by Dr. R. East ( 23 June ‘97 ) and updated on the basis of information found in Kingdon (1997).
Categorical-discrete (CD) distribution model
The species occurs in riverine valleys within lowland rainforest, but also in gallery forests and thick bush near water (Kingdon, 1997; Coe, 1975).It 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). It is exclusively nocturnal, being active between the hours of 1800 and 0600 (Dubost, 1978 in Nowak, 1991; Robin, 1990). Foraging in in clearings, floodplains, and along river banks 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)
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, 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 reduce the incidence of severe injuries inflicted by the tusks (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 (Robin, 1990). However, like the musk deer and Chinese water deer, the upper canine teeth tusks well developed and sabre-like in males, protruding out of the mouth on either side of the lower jaw (Happold, 1973; 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)
As with many small forest ungulates, the water chevrotain is strictly solitary (Robin, 1990; Kingdon, 1997). Adult female 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, on the other hand, 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 typically 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). May hide almost completely submerged (Happold, 1973).
H. aquaticus forages primarily in mature forest, along 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 includes 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 - other small frugivores 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).