2004: Population and Distribution of Turtles in Lake Matoaka

Emily Thompson (Biology) College of William and Mary

The research questions addressed in this study were (1) What is the population size of sliders in Lake Matoaka, and (2) What is the relative species distribution of turtles in Lake Matoaka? Lake Matoaka has two "arms"- one downhill of development by the College of William and Mary and the other undeveloped and surrounded by the College Woods. The introduced species of turtles in Lake Matoaka are descendents of unwanted pets that have been dumped in the lake. Since turtles have been shown in other studies to show a strong sense of homing, the hypothesis is that there is a larger concentration of introduced species of turtles on the east/developed arm of the lake than on the west/ undeveloped arm of the lake. The hypotheses assumes that people will dump turtles from the developed side of the lake and that those turtles will exhibit fidelity to that side. The native turtles captured in the study are Red Belly Sliders (Pseudemys rubriventris), Eastern Painted Turtles (Chrysemys picta picta), Common Snapping Turtles (Chelydra serpentina serpentina), and Stinkpot Turtles (Sternotherus odoratus). The introduced turtles are Red Ear Sliders (Pseudemys scripta elegans) and slider hybrids.
Turtles were collected by hand during June when females were laying eggs on land and were trapped with hoop nets in the lake for the entire study. A total of 245 turtles were collected and 6 turtles were recaptured. One turtle was recaptured in the same location and one turtle moved from the East to the West arm of the lake. Although the number of recaptures was very small, the recapture data show that the turtles are not loyal to one small cove and that they do move freely around the lake. A population estimate of 2057 Red Belly Sliders was estimated using the Schnabel method, but the estimate is probably high because the number of total recaptures was very low.
Species composition is similar on the East versus the West arms of the lake. The introduced Red Ear Sliders are present on both arms but the overall turtle population of the lake is dominated by native species. The hypothesis that more introduced species would be captured on the East/developed arm of the lake is not supported. An interesting trapping trend was observed when two traps were set on the same arm of the lake: one trap was very successful in catching turtles while the other failed to trap turtles. When only one trap is set on one arm, trapping success varied non-systematically. These data suggest that the turtles may be moving around the lake in feeding or social groups, but the sample size is too small to draw any conclusions about turtle behavior.

For additional documentation Emily Thompson provided a PowerPoint Presentation entitled "Population And Distribution of Turtles in Lake Matoaka"  provided here in PDF form.