Tragulus nigricans, Thomas, 1892

Don E. Wilson & Russell A. Mittermeier, 2011, Tragulidae, Handbook of the Mammals of the World – Volume 2 Hoofed Mammals, Barcelona: Lynx Edicions, pp. 320-334 : 333

9.

Balabac Chevrotain

Tragulus nigricans

French: Chevrotain de Balabac / German: Balabac-Kantschil / Spanish: Ciervo ratén de Balabac

Other common names: Pilandok

Taxonomy. Tragulus nigricans Thomas, 1892 ,

Balabac, Philippines.

This species was resurrected as a distinct species in 2004 based on skull morphology. 1. nigricans was originally allied with 1" napu due to similarities in body size and markings. Skull measurements demonstrate clear differentiation between T. nigricans , 1. napu , and 1. kanchil , the species from nearby Borneo and surrounding small islands. 7. nigricans is a restricted area species endemic to the Philippines, and there are no subspecies. It has been suggested that the chevrotain population of Pulau Banggi ( Malaysia), which lies midway between Balabac and the Bornean mainland, and which was almost certainly (and perhaps repeatedly) connected to both by former (late Pleistocene) land bridges, might belong to this species. Recent morphometric study of specimens from Pulau Banggi indicates its distinctiveness from both 7. napu and 1. nigricans , suggesting that morphometrically the Pulau Banggi population is more closely related to 7. kanchil . Throat patterns and coloration of the upperparts, however, suggests a napurelated taxon, and for now the subspecies T. napu banguei is retained for the Banggi population. Monotypic.

Distribution. Balabac, Ramos, and Bugsuk Is, Palawan region, Phillipines. In the late 1990s, a small stock of eight Balabac Chevrotains escaped from their enclosures on Calauit Island, a small island off the coast of Busuanga Island, north of Palawan, where the species had been maintained and bred since 1982. These animals were reported to have increased to at least 21 free-living individuals by 2006. Apparently the species was also introduced to the larger island of Palawan. No recent records confirm that it is still extant there, although unconfirmed reports suggest that it may survive in southern Palawan.

Descriptive notes. Head-body 40-47. 5 cm, tail 6.5-8. 5 cm, shoulder height 18 cm; weight unknown. The Balabac Chevrotain is very small in stature, and smaller than its apparent close relative 71. napu from neighboring Borneo. T. nigricans is one of the most darkly-colored chevrotains, with an overall dark brown coat. The upperparts are broadly washed with black, and the neck is mixed black and fulvous. Each individual hair has sections of different colors. The base is generally pale, ranging from white to ashy brown, the mid-section is tawny, orange, or brown, and there is a long black tip. The abdominal region is generally orange-brown in color. The lower abdomen, groin, and insides of the thighs are white. The hindlegs have a white stripe on the front that extends from the upper thigh to the tarsal joint; the rest of the leg is fulvous in color. The inner surfaces of the front legs are white, and this coloration extends across the chest in between the front legs as a whitish patch. The tail is dark brown with a white tip. 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. In contrast to these white stripes, the rest of the throat is jet black; in some specimens the black coloration even overtakes and obscures the stripes. Towards the chest, these black and white markings disappear into a broad brown band that crosses the lower throat. The head itself is generally darker in color than the rest of the body. 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. A naked glandular patch on underside of the jaw is bordered with white, which runs into the white patch at the top of the throat. Dental formula is 10/3,C1/1,P3/3,M 3/3 (x2)= 34.

Habitat. 7. nigricans inhabits both primary and secondary forests as well as shrubland on Balabac Island, using both large blocks of forest and smaller fragments. It may frequent mangroves and more open areas to forage. Dense vegetation within the forest interior provides shelter for this species during the daytime.

Food and Feeding. It is reported that 7. nigricans feeds mostly on leaves, which would set it aside from most other chevrotain species, which are primarily frugivorous. One photograph of a captive animal shows it feeding on grass-like leaves, which would confirm the above observation.

Breeding. There is apparently a distinct breeding season, but it is unclear when this occurs and whether it coincides with the distinct dry and wet seasons in the species’ range. Litter size is reportedly almost always one, rarely two.

Activity patterns. Reported to be nocturnal. These chevrotains leave their shaded resting spots at night, entering into clearings to feed. Most encounters between humans and the Balabac Chevrotain occur along roads at night, when their eye shine is frequently observed from vehicles.

Movements, Home range and Social organization. Nothing known.

Status and Conservation. Classified as Endangered on The IUCN Red List, and is probably the most range-restricted of all chevrotain species. The species is subject to poaching for food, using guns or snares, and there is minor domestic trade in live animals for local zoos and private collectors. The species is also affected by habitat loss due to conversion of former habitat to coconut plantations and other agriculture.

Bibliography. Allen & White (1910), Huffman (2009), Meijaard & Groves (2004a, 2004b), Oliver (1992), Oliver et al. (2008), Rabor (1977), Rico & Oliver (2008), Sanborn (1952), Timm & Birney (1980).

Figures

1. White-spotted Chevrotain (Moschiola meminna), 2. Yellow-striped Chevrotain (Moschiola kathygre), 3. Indian Chevrotain (Moschiola indica), 4. Silver-backed Chevrotain (Tragulus versicolor), 5. Lesser Indo-Malayan Chevrotain (Tragulus kanchil), 6. Northern Chevrotain (Tragulus williamsoni), 7. Javan Chevrotain (Tragulus javanicus), 8. Greater Indo-Malayan Chevrotain (Tragulus napu), 9. Balabac Chevrotain (Tragulus nigricans), 10. Water Chevrotain (Hyemoschus aquaticus)

Distribution. Balabac, Ramos, and Bugsuk Is, Palawan region, Phillipines. In the late 1990s, a small stock of eight Balabac Chevrotains escaped from their enclosures on Calauit Island, a small island off the coast of Busuanga Island, north of Palawan, where the species had been maintained and bred since 1982. These animals were reported to have increased to at least 21 free-living individuals by 2006. Apparently the species was also introduced to the larger island of Palawan. No recent records confirm that it is still extant there, although unconfirmed reports suggest that it may survive in southern Palawan.