Melanochelys trijuga

(Schweigger, 1812)
Indian black turtle

The carapace is elongated (to 38.3 cm), slightly depressed, and has three keels (a medial keel along the vertebrals and two lateral keels along the dorsal portions of the first three pleurals). The posterior marginals are not serrated (or only slightly so in juveniles) and the lateral marginals are slightly upturned. In adults, the vertebral scutes are variable in width and length. Usually the anterior four are as long as or longer than broad, but the posteriormost is broader than long. Carapacial ground color varies from reddish brown to dark brown or black; often the keels are yellow. The plastron is elongated and well-developed. Its anals are notched posteriorly, and the plastral formula is: abd >< pect > fem >< an > gul>< hum. The bridge is about as long as the posterior plastral lobe, and its inguinal scute is short. The plastron is either uniformly dark brown or black, or it may have a yellow border. The head is of moderate size with a relatively short snout and medially notched upper jaw. The head varies in color from brown to black and may contain orange or yellow spots or reticulations, or a large yellow or cream-colored blotch at the temporal region. Limbs and tail are gray to dark brown or black. The anterior surface of the forelegs is covered with large scales. All toes are fully webbed to the claws, or nearly so.
The karyotype is 2n = 52; 28 macrochromosomes (18 metacentric or submetacentric, 10 telocentric or subtelocentric) and 24 microchromosomes (Carr and Bickham, 1986).
The tail of the male is longer and thicker than that of the female, and he possesses a concave plastron.

Melanochelys trijuga ranges through most of peninsular India, Nepal, northern Bangladesh, the Myanmar/Thailand border region, and Sri Lanka; populations on the Maldives and the Chagos Islands may have been introduced (Deraniyagala, 1939).

Geographic Variation
Six subspecies have been named, but most are poorly described, and this species is in need of taxonomic revision. Melanochelys trijuga trijuga (Schweigger, 1812), the peninsular black turtle, transects central peninsular India, extending from just north of Bombay southward to Coorg in the west, to about Bezwada southward, and to Cuddalore in the east. M. t. thermalis (Lesson, 1830), the Sri Lanka black turtle, occurs on the southeastern coast of peninsular India, the Maldive Islands, and Sri Lanka. The Burmese black turtle M. t. edeniana Theobald, 1876 is occurs in Arakan, the Karenni hills, and Moulmein, Myanmar. Another race has been proposed from the Myanmar border area in Tak and Mae Hong Son provinces, Thailand, M. t. wiroti (Reimann, in Nutphand, 1979). The accompanying description and drawings of the shell are too general to distinguish it from other subspecies of M. trijuga, and the photographs appear to be of M. t. edeniana. Unfortunately no type or type series have been designated, so comparable material is lacking. Under these circumstances, it is best to consider this M. t. wiroti a synonym of M. t. edeniana. M. t. coronata (Anderson, 1879), the Cochin black turtle, occurs on the southwestern coast of peninsular India from Calicut southward through Travancore. The Bengal black turtle M. t. indopeninsularis (Annandale, 1913) is found in northeastern India, northern Bangladesh and Nepal (this subspecies differs only in size from M. t. edeniana). The last subspecies, M. t. parkeri Deraniyagala, 1939, Parker's black turtle, is restricted to lowlands in Sri Lanka. These six races are separated primarily on the coloration and pattern of the head, carapacial length, and plastron pattern. Subsp. variation in M. trijuga summarizes subspecific variation. The subspecies can best be identified by a combination of characters and their geographic ranges.

Throughout its range Melanochelys trijuga is predominantly a freshwater species inhabiting ponds, streams, and rivers with clean water. However, at times it may be found on land far from water. Deraniyagala (1939) reported that M. t. parkeri spends much time ashore and even aestivates under dead vegetation in the jungle during droughts. He also reported that some M. t. thermalis individuals on Sri Lanka live in burrows and have very flattened carapaces. Annandale (1913) thought M. t. indopeninsularis visits water during hot weather, but lives habitually, without actually entering water, in damp places. Mitchell and Rhodin (1996) studied M. t. indopeninsularis in Nepal and suggested a pattern of differential habitat use for juveniles, found in hillside streambeds, and adults, preferring lentic backwaters and oxbow lakes.

Natural History
Males of Melanochelys trijuga are aggressive during courtship, pursuing and frequently biting the female, especially on the neck. Nesting apparently occurs throughout the year, at least in M. t. thermalis (Deraniyagala, 1939), and 2-6 clutches totaling 18 eggs are laid each year (Das, 1991). Forty-seven clutches laid by female M. t. thermalis at the Columbus Zoo, Ohio contained 1-6 (mean 3.02) eggs, with as many as 11-12 eggs being laid a year (Goode, 1991). Incubating eggs of Melanochelys were found twice (March, November) at Royal Chitwan National Park, Nepal by Dinerstein et al. (1987), both times buried in grassland latrines of the greater one-horned rhinoceros. The eggs were presumably those of M. trijuga, the more common Melanochelys there, rather than the more rare M. tricarinata (the clutch sizes of 3 and 6 eggs also most closely match those of M. trijuga). The first clutch contained three oblong (46.8-49.1 x 26.7-27.6 mm) hard-shelled eggs; the second clutch was of six eggs (44.6-50.7 x 26.7-28.3 mm), and was buried approximately 30 cm deep in the rhinoceros dung. Das (1991) reported the calcareous eggs are white and elongated (39.9-55 x 24-30 mm); incubation lasts about 60-65 days. Hatchlings are about 41-46 mm in carapace length and are more brightly patterned than adults.
M. trijuga is predominantly herbivorous, feeding on aquatic plants such as Vallisneria, but Deraniyagala (1939) reported that M. t. thermalis is omnivorous and has scavenging habits.
This species spends most of the daylight hours basking, but is also active at night, coming on shore and foraging in wet grass and ditches (Annandale, 1913). When first captured, specimens are shy and may emit a strong musky odor.

IUCN Red List Status (1996)
Data deficient.