Degree Name

Master of Science (MS)

Semester of Degree Completion

1980

Thesis Director

Edward O. Moll

Abstract

Batagur baska, Callagur borneoensis, Cuora amboinensis, Cyclemys dentata, Orlitia borneensis, Siebenrockiella crassicollis, and Trionyx cartilagineus are suggested to be omnivorous by diet analysis. Cyclemys and Orlitia are the more herbivorous of the seven species examined. Batagur and Callagur are two closely related sympatric species that appear to have diverged sufficiently to eliminate competition for food resourses, as indicated by Morista's Index of Niche Overlap. Along the Perak River and it's tributaries in West Malaysia, Batagur and Callagur feed primarily upon the fruit of the berembang tree. In Trengganu (eastern Malaysia), the berembang is absent or rare along the rivers, thus other fruits and leaves make up the diet of these two species. Two other species share similar habitats, Cuora and Siebenrockiella. They also appear to have eliminated competition for food resourses. Cuora tends to be more herbivorous feeding along the shoreline and Siebenrockiella more of a scavenger. Little is known about the diet of Orlitia. Based on one individual's two fecal samples, Orlitia is herbivorous.

Examined for certain reproductive characters were Cuora amboinensis, Cyclemys dentata, and Siebenrockiella crassicollis. Cuora appears to be a seasonal nester on the east (involving April, May, and June) and west (including at least October and and November) coasts of West Malaysia. Nesting occurs during the dry periods; between the northeast and southwest monsoons. Clutch size is small with relatively large eggs and the reproductive potential is at least six eggs per nesting season. Cyclemys is also a seasonal nester (May and June on east coast and at least March on the west coast). They produce one or two clutches of large eggs with a reproductive potential around three to five eggs per season. Siebenrockiella is a seasonal nester in the east coast drainages (prior to June and again in December). It is not conclusive if they are seasonal nesters on the west coast drainages (some activity in January and October). Siebenrockiella lays multiple clutches (as does Cuora) of relatively large eggs with a reproductive potential of six to nine eggs per season. Cyclemys has a slightly different nesting strategy than Cuora and Siebenrockiella. It is suggested that Cyclemys' nesting strategy is to reduce predation of the nesting female. Whereas, Cuora's and Siebenrockiella's strategy is to prevent predation on the eggs. Cuora, Cyclemys and Siebenrockiella compromise with a reproductive strategy found among semi-aquatic, tropical turtles.

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