Effects of Weather Conditions and Drought on Activity of Spotted Turtles (Clemmys guttata) in a Southwestern Michigan Wetland

The persistence of a population of ectothermic vertebrates can be closely tied to variations in weather patterns that influence diel or seasonal cycling of temperature and moisture levels. We. studied the effects of drought and weather patterns on the summer activity and movements of Spotted Turtles (Clemmys guttata) in a small wetland in southwestern Michigan over 2 y. During the periods of time with standing water, turtles aquatically active in depressions or terrestrial in grass-sedge-rush and Sphagnum hummocks but their movements were unaffected by daily weather patterns. Turtles tended to occupy multiple core areas within a relatively contiguous home range. When the wetland dried, turtles estivated beneath vegetation, or estivated or maintained limited activity in small forest ponds immediately adjacent to the wetland. In 2006, turtles resumed activity following heavy rains during late Jul. and early Aug. In 2007, however, late summer rains were not sufficient to restore substantial standing water in the wetland and so turtle movements were relatively low. Home range and core area size were significantly smaller in 2007 than in 2006, apparently because of the relatively short summer hydroperiod that occurred during 2007. Unlike previously studied C. guttata populations, the turtles of our population did not travel among multiple upland and lowland habitats, perhaps because such environments were not of higher quality than our wetland, or because the risks of traveling to them were too great.