Hewitt, 1931
Yellow-bellied mud turtle
Recognition
The yellowish, olive, or blackish carapace may have a marbled pattern of yellow and brown marks. It is oval, elongated (to 23 cm), and rather narrow in males (especially in the subspecies P. c. intergularis). A low vertebral keel may be present on the 4th and 5th vertebrals, and the posterior marginals may be slightly serrated. Vertebral 1 is anteriorly flared and is the largest; the 5th vertebral is posteriorly flared; the 4th is the smallest; and vertebrals 1-4 may be as long as or longer than broad. Five to eight neurals are present (the 1st, 7th and 8th are always reduced or absent) and well-separated from both the nuchal and suprapygal bones (Broadley, 1983). The plastron is large, almost covering the entire carapacial opening, and its anterior lobe is much shorter than the posterior lobe, which is slightly constricted at the seam separating the abdominal and femoral scutes and has a deep anal notch. The plastral formula is variable: abd > fem > intergul > hum > pect >< gul >< an, and the intergular is 1.35-1.72 times as long as broad. The bridge is broad, but lacks an axillary scute. The plastron is yellow with some dark pigment along the seams. The brown to olive-black head is moderate in size with a slightly protruding snout. Two barbels occur on the chin. Other skin is yellow to brown. Several transverse rows of enlarged scales occur on the forelegs.
Males have narrower plastra and longer, thicker tails. The posterior lobe on the female plastron is broad.
Distribution
Pelusios castanoides is found in eastern Africa from Kenya southward to northeastern South Africa. Populations also occur on the Seychelles Islands and Madagascar.
Geographic Variation
Two subspecies are currently recognized. Pelusios castanoides castanoides Hewitt, 1931, the East African yellow-bellied mud turtle, ranges from Malawi and Mozambique in East Africa south to Swaziland and eastern South Africa; it also occurs on Madagascar. It has a yellow, olive, or black carapace, and an intergular scute separated from the adjacent gular scutes by diagonal seams. The Seychelles yellow-bellied mud turtle, P. c. intergularis, Bour, 1983 occurs on the Seychelles Islands. It has a dark carapace with a marbled pattern of yellow and brown marks, and a pentagon-shaped intergular scute with longitudinally parallel (straight) seams separating it from the gulars. The Madagascar population, named P. castaneus kapika by Bour (1978), is indistinguishable from P. c. castanoides (Broadley, 1981a; Bour, 1983).
Habitat
Pelusios castanoides inhabits marshes and swamps. During the dry season it aestivates in the mud.
Natural History
Two captives from Malawi each laid 25 eggs (30-33 x 21.5-23.0 mm) at the end of September (Mitchell, in Broadley, 1981a).
P. castanoides feeds mainly on large pulmonate snails and floating water lettuce (Broadley, 1981a). Justin Gerlach (pers. comm.) reports the Seychelles subspecies to be nocturnal, feeding on fruits, plant shoots, snails, and crabs.
IUCN Red List Status (1996)
Not listed in Baillie and Groombridge (1996), but P. c. intergularis is considered Critically Endangered in Seychelles Red Data Book 1997 (Gerlach, 1997a). Its population on the Seychelles is as small as 300-350 individuals.