Diel Activity Patterns of the Turtle Assemblage of a Northern Indiana Lake

—We investigated the daily activity patterns of seven species of turtles in a northern Indiana lake over 10 y using the numbers of captures in fyke nets as an index of activity. Chrysemys picta and Graptemys geographica were active throughout the daylight hours. Sternotherus odoratus and Chelydra serpentina were crepuscular. Trachemys scripta was diurnal; however, its activity was concentrated in the morning hours. Apalone spinifera was diurnal as well, with most activity in the afternoon and very little in the morning. Emydoidea blandingii was rarely captured, and all captures were made during daytime hours. Activity patterns did not change substantially between two sampling periods from mid-May to mid-June and from lateJuly to early-August. These activity patterns are consistent with differences in the frequency of basking: baskers are diurnal (e.g., C. picta, G. geographica, T. scripta, E. blandingii and A. spinifera), whereas those that are secretive are crepuscular (e.g., S. odoratus and C. serpentina).