Spatial Ecology of Northern Map Turtles (Graptemys geographica) in a Lotic and a Lentic Habitat

Abstract

Lentic (i.e., lake) and lotic (i.e., river) environments differ in several biotic and abiotic variables such as water velocity, productivity, thermal regimes, and depth. These variables can interact with important factors such as sex, body size, and life-history stage to shape the spatial ecology of aquatic animals such as freshwater turtles. We used radio-telemetry to study seasonal movement patterns and home-range size of juvenile and adult Northern Map Turtles (Graptemys geographica) both in a small lake and in a large river in eastern Ontario, Canada. Adult females in the lotic environment moved longer distances and had larger home ranges than conspecifics from the lentic environment. Males and juvenile females at each site had similar patterns of space use. A seasonal effect on movement was only apparent for adult females in the lotic environment in which adult females moved longer distances during the nesting season. Differences in swimming abilities resulting from a larger body size, in natal homing, or in nest site availability are potential factors explaining the site difference in the spatial ecology of adult females. Our findings illustrate the complexity of interactions shaping patterns of space use by aquatic reptiles.