(Duméril and Bibron, 1835)
West African black turtle
Recognition
The carapace (to 26.3 cm) is elongated and oval, flattened across the vertebrals, and unserrated posteriorly in adults. A low medial keel is present but may be reduced to the 4th and 5th vertebrals in old individuals; there is no cervical scute. Vertebrals are broader than long; the 1st flared anteriorly, the 5th posteriorly. Posterior marginals are slightly flared. There are eight neural bones. The carapace is black to reddish brown with light seams; some individuals have growth rings and light-colored radiations on the vertebrals and pleurals. The plastral anterior lobe is broad and short, only slightly longer or about the same length as the abdominal scute. The posterior lobe is also short, but narrow, contains a posterior notch, and cannot entirely close the shell. Also, there is no abdominal-femoral constriction. The plastral formula is: abd > fem > intergul > hum > an > gul > pect; as can be seen, the abdominal scute is very long. The pectoral scute does not contribute to the bridge, and axillary and inguinal scutes are absent. Both plastron and bridge are black with cream-colored to yellow seams. The head is narrow for the genus, with a protruding, pointed snout and a slightly hooked upper jaw. Two barbels are present on the chin. The head is yellow with numerous dark-brown or black vermiculations; the yellow jaws also are darkly vermiculated and the chin yellow. Neck, limb, and tail skin is yellow to gray. Three or four large transverse scales are present on the anterior surface of the forelimbs.
The diploid chromosome number is 34 (Bull and Legler, 1980).
Males have longer, thicker tails than those of females.
Distribution
Pelusios niger is confined to West Africa where it ranges from Sierra Leone and Liberia to Gabon.
Habitat
Pelusios niger lives in permanent bodies of water with soft bottoms in the savannahs.
Natural History
Although known since 1835, very little has been published on the lifestyle of this species, and probably much has been confused with that of Pelusios subniger and P. castaneus. Cansdale (1955) reported this turtle (as subniger) digs a nest 10-12.5 cm deep in grasslands. A clutch comprises 6 to 18 eggs, but more normally 10 to 13; the eggs have pliable shells with chalky white surfaces. Cansdale also reported that they spend the dry season underground and that many are dug up while ploughing.
Young individuals we have examined had more rounded carapaces with slightly serrated posterior borders. The medial keel is more pronounced than in adults, and the surfaces of the carapacial scutes are covered with small knoblike rugosities which often form radiating lines from the raised areola of the scute. None of those with plastra <70 mm had the hinge developed. Also, several of these juveniles did not have as many dark vermiculations on the head as normally occur in adults.
Like other Pelusios, P. niger is mainly carnivorous, feeding on a wide variety of small aquatic animals.
Remark
This species has been confused with both P. subniger and P. castaneus. P. niger differs from the former by several characters including its hooked upper jaw and unconstricted plastral posterior lobe. Laurent (1965) has shown that the length of the border of the intergular scute is much longer in P. niger than in P. castaneus, while the external border of the femoral scute is much longer in P. castaneus than in P. niger.
IUCN Red List Status (1996)
Not listed.