(Schweigger, 1812)
West African mud turtle
Recognition
The carapace (to 22 cm) is elongated, oval, broadest behind the center, and has a low vertebral keel (usually in the form of a protuberance on the 4th vertebral). In adults the 1st vertebral is flared anteriorly and the 5th is flared posteriorly; both are broader than long. The 2nd through 4th vertebrals are as broad as long, or slightly longer than broad. Eight neurals are present in a continuous series; neural 1 is in contact with the nuchal bone, but the 8th neural is well-separated from the suprapygal bones. The posterior marginals are not serrated. In color the carapace varies from yellowish brown to olive, dark brown, or black. The plastron is large, almost covering the entire carapacial opening, has a short anterior lobe less than twice as long as the interabdominal seam, and is deeply notched posteriorly. Its posterior lobe is only slightly constricted or not constricted at the level of the abdominal-femoral seam. The plastral formula is: abd > fem > hum >< intergul > an >< pect > gul. The intergular varies from 1.3 to 1.5 times as long as broad. The bridge is broad and lacks an axillary scute. Usually the plastron is yellow, but it may contain some dark pigment medially or at the outer edges of the seams. The head is moderate in size with a slightly protruding snout and an upper jaw bearing two toothlike cusps. The seam between the frontal and temporal scales is long. The postocular scale normally touches the masseteric scale; the supralabial scale is usually absent, but, if present, is small. There are two chin barbels. The head is olive to brown with light vermiculations. The neck and limbs are yellow to gray, and each foreleg has several enlarged transverse scales on its anterior surface.
Males have longer tails and slightly concave plastra; the plastra of females are flat.
Distribution
Pelusios castaneus occurs from Guinea and Senegal to northwestern Angola and the Central African Republic in West Africa; it also occurs on the Sao Tome Islands. Introduced on Guadeloupe, Lesser Antilles, according to Schwartz and Thomas (1975).
Geographic Variation
Pelusios castaneus is now considered monotypic, but certain characters seem to change clinally throughout its range from west to east and from savannah to forest zones: smoothing of the rhamphotheca, darkening and reduction of sinuosity of the light dorsal vermiculations on the head, and development of peripheral plastral pigmentation (Roger Bour, pers. comm.).
Habitat
Pelusios castaneus lives in a variety of habitats such as rivers, streams, marshes, swamps, lakes, and shallow ponds. Many of these water bodies are dry for much of the year and the turtles are forced to aestivate buried either in the sand on shore or in the bottom mud.
Natural History
Much of the biology of the West African mud turtle has been confused with that of other Pelusios species. As part of the courtship, the male repeatedly approaches the female from behind, swims underneath her and touches her throat with his muzzle. During the intercourse, the male swings his fully outstretched neck in front of the retracted head of the female (Rödel, 1989; as P. w. williamsi).
Cansdale (1955) reported (as P. subniger) that in West Africa it nests in February and March laying 6-18 eggs (with soft, chalky surfaces) per clutch; he stated the eggs hatch in June or July. Villiers (1958) reported a female (as P. subniger) laid 12 eggs, and that the eggs of a captive from Dakar measured 36 x 21 mm. Rödel's (1989) captive female deposited her eggs in the water in March and September; a clutch of nine 40 x 21 mm eggs successfully hatched after 76-84 days. Hatchlings (30-40 mm) have an almost black carapace with yellow markings on the ventral side of the marginals, a plastron with a few very small yellow blotches, and a yellow, interrupted stripe running from the lower rim of the orbit to the tympanum on the dark gray head.
Rödel's (1989) animals take all kinds of animal matter, such as dog food, fish, earthworms, and snails; they also accept strawberries and bananas.
Remark
This species is possibly related to P. castanoides and P. seychellensis (Broadley, 1981a; Bour, 1983).
IUCN Red List Status (1996)
Not listed.