Tragulus nigricans [Thomas, 1892].

Citation: Annals and Magazine of Natural History, Series 6, vol. ix: 254.

Type locality: Balabac, Philippines.

The original taxonomic reference (above) is taken from Lydekker (1915). This species, frequently reported as a subspecies of Tragulus napu, was resurrected as a distinct species in 2004 based on skull morphology (see Meijaard and Groves, 2004), although several authors prior to this distinguished the Balabac chevrotain as a full species (see, for example, Rabor, 1977). T. nigricans was originally allied with T. napu due to similarities in body size and markings, although Meijaard and Groves (2004) suggest that it may be more closely related to T. javanicus. Nevertheless, these authors have kept T. nigricans in close association with T. napu. Skull measurements demonstrate clear differentiation between T. nigricans and both T. napu and the T. javanicus complex (Meijaard and Groves, 2004). This species was incorrectly referred to as Muntiacus nigricans by Allen and White (1910); otherwise there are no synonyms. Endemic to a single island in the Philippines, the Balabac chevrotain has no subspecies.

The Balabac chevrotain, like all members of the family Tragulidae, is very small in stature (Rabor, 1977). This species is smaller than T. napu from neighbouring Borneo (Meijaard and Groves, 2004). Head and body length for T. nigricans is approximately 40-50 cm; shoulder height is approximately 18 cm. No live weights for this species have been reported.

T. nigricans is one of the most darkly-colored chevrotains, with an overall dark brown coat (Rabor, 1977; Oliver, 1992). Each individual hair has sections of different colors - the base is generally light (ranging from white to ashy brown), with a tawny, orange, or brown midsection, and a long black tip (Allan and White, 1910; Lydekker, 1915; Rabor, 1977). The black tips on the hairs give the coat (especially on the upper parts) a dark-washed look (Lydekker, 1915; Meijaard and Groves, 2004). The nape of the neck is a mix of predominantly black and fulvous (yellowish-brown) hairs; the hairs are sometimes arranged into indistinct blackish lines (Rabor, 1977; Meijaard and Groves, 2004).

The abdominal region is generally orange-brown in color, with the hairs on the belly also having black tips (Allan and White, 1910; Rabor, 1977). The lower abdomen, groin, and insides of the thighs are white (Allan and White, 1910; Rabor, 1977). The hind legs have a white stripe on their fronts which extends from the upper thigh to the tarsal joint; the rest of the leg is dull orange in color. The inner surfaces of the front legs are also white, and this light coloration extends across the chest between the front legs as a whitish patch (Allan and White, 1910; Rabor, 1977). The tail is dark brown with a white tip (Allan and White, 1910).

The most striking markings of the Balabac chevrotain are on the throat, with three narrow white stripes beginning from a white patch under the chin and extending down towards the chest (Allan and White, 1910; Rabor, 1977). In intense contrast to these white stripes (and sharply defining them), the rest of the throat is jet black; in some specimens the black coloration even overtakes and obscures the stripes (Lydekker, 1915; Rabor, 1977). Towards the chest, these black and white markings disappear into a broad brown band which crosses the lower throat (Allan and White, 1910; Rabor, 1977).

The head itself is generally darker in color than the rest of the body (Rabor, 1977). Broad rufous or fulvous 'eyebrow' stripes extend from the anterior corners of the eyes to the base of ears. The bridge of the nose and forehead are dark brown, becoming increasingly infused with black towards the crown of the head. The sides of the head are more fulvous (Allan and White, 1910). A naked glandular patch on the underside of the jaw is bordered with white, which runs into the white patch at the top of the throat (Allan and White, 1910; Lydekker, 1915; Rabor, 1977). There are no horns or antlers, but the upper canines are enlarged and very sharp; these are the primary defensive weapons of T. nigricans (Rabor, 1977; Rabor 1986). Skull measurements for this species are given by Allen and White (1910) and Meijaard and Groves (2004).

Very little is known about the specific aspects of this species' life history. Rabor (1986) reports that there is a breeding season (but makes no mention as to when this occurs), and that the litter size is almost always one, rarely two. Reports for other members of the genus Tragulus suggest that the gestation period is 140-177 days, sexual maturity is reached by 5 months of age, and the life span is up to 14 years (Nowak, 1991).

Rabor (1977 and 1986) provides a brief overview of the ecology of T. nigricans:

T. nigricans inhabits both primary and secondary forests on Balabac island, utilizing both large blocks of forest as well as smaller fragments. Dense vegetation within the forest interior provides shelter for this species during the daytime. Nocturnal by nature, these chevrotains leave their shaded resting spots at night, entering into clearings where they are more visible (and vulnerable). Most encounters between humans and the Balabac chevrotain occur along roads at night, when their eye shine is frequently observed from vehicles. This species acts like the proverbial "deer in the headlights", normally freezing and staring into the light for an extended period of time before fleeing. This species is occasionally seen at the seashore. Like most chevrotains, T. nigricans is solitary, although pairs are occasionally seen. This species feeds mainly on leaves.

T. nigricans is endemic to Balabac and two neighbouring islands (Ramos and Bugsuc) in the Palawan chain of the Philippines, located between Borneo and the island of Palawan (Rabor, 1977; Oliver, 1992; Widmann, 2015). Several attempts to introduce this species to the island of Palawan have not been successful (Rabor, 1977 and 1986), although Oliver (1992) mentions unconfirmed reports that a population may have become naturalized in South Palawan. Populations have been introduced to Apulit and Calauit islands (see Widmann, 2015); a captive breeding program was initiated on Calauit in 1982 and was able to sustain a population at least until 1992 (see Oliver, 1992). Escapes from this program have lead to a free-living population of at least 21 animals in 2006 (Rico and Oliver, 2008 in Widmann, 2015). It is unknown whether chevrotains inhabiting the island of Pulau Bangi (Malaysia) between Borneo and Balabac belong to this species (Widmann, 2015).

Countries: Philippines (Widmann, 2015).

The Balabac chevrotain is classified as endangered (Criteria B1ab(iii,v)) by the IUCN (2015). No members of the family Tragulidae are listed by CITES (2009). This status of this species in the wild has never been methodically determined, and no estimates of population numbers are available. Nonetheless, population numbers have been greatly reduced over the past several decades through extensive habitat loss (to agriculture, notably coconut plantations) and intense hunting (Rabor, 1977; Oliver, 1992; Widmann, 2015). The Balabac chevrotain is hunted by locals using guns or snares; the meat is considered a delicacy and the skin is used for leather (Rabor, 1977; Rabor 1986).

The genus name Tragulus means "little goat", derived from Tragos (Greek) a goat and the diminutive suffix -ulus (Latin). The species name nigricans is a Latin adjective meaning blackish (from niger (Latin): black), referring to the dark coloration of this species.

Named after the island to which it is native, the Balabac chevrotain is also known as the Philippine chevrotain (or mouse deer) - it is the only member of the family Tragulidae to inhabit the Philippines (Rabor, 1977).

Local names

Pilandok [Palawan, Balabac] (Rabor, 1986).