Habitat and Temperature Selection of Clemmys guttata in a Northern Population

Abstract

-We used temperature-sensitive radiotransmitters to study habitat use and temperature selection of spotted turtles (Clemmys guttata) on an island in Georgian Bay, Ontario, Canada. Each of two field seasons was divided into four 'subseasons: Mating, Nesting, Aestivation, and Pre-hibernation, based on seasonal changes in spotted turtle behavior. We observed distinct seasonal shifts in habitat use. In spring (May-June), turtles aggregated in ponds to court and mate. In late June, females nested on open rock outcrops. During July and August, turtles spent about half their time buried in terrestrial forms on rock outcrops and in forests, and were actively swimming and basking, and presumably feeding, during the remainder of this subseason. From September to April, turtles hibernated in sphagnum swamps. Using temperature-sensitive radiotransmitters, we determined average body temperatures while turtles were basking (25.3 C), courting and mating (15.1 C), nesting (19.8 C), foraging and feeding (16.7 C), aestivating (21.8 C), and entering hibernation (9.5 C). We also recorded air and water temperatures during these activities. Comparisons of body temperatures to air and water temperatures, and observed habitat use, suggested that high summer temperatures and avoidance of desiccation were not the proximate causes of aestivation in this northern population. The annual activity patterns, habitat use, and thermal regime of most freshwater turtles are poorly known, particularly of those species occurring at northern latitudes. For species that are restricted in habitat and distribution, and that are declining or rare, it is often important to characterize their habitat and thermal requirements to provide guidelines for conservation and management programs that set aside areas of habitat critical to the species' needs. The spotted turtle (Clemmys guttata) is restricted to eastern North America. It ranges from Ontario and Maine southward along the Atlantic Coastal Plain to central Florida, and westward into Illinois (Ernst et al., 1994; Barnwell et al., 1997). In Canada, the species curPresent Address: Department of Biological Sciences, University of South Carolina, Columbia, South Carolina 29208, USA. , i a se, a tles are s s ecies oc. s ecies t at i i ti , a i i i orta t rently is regarded as vulnerable (Oldham, unpubl. data). Few published studies have reported on habitat use and microhabitat selection by spotted turtles throughout their annual activity cycle (Ward et al., 1976; Graham, 1995; Perillo, 1997). Indeed, nothing is known about these aspects of the species' ecology at the northern limit of its range in Ontario where the Canadian Shield is a predominant geological landform. This study attempts to develop a comprehensive picture of the habitat and thermal requirements, and annual activity patterns of spotted turtles from Georgian Bay, Ontario. Several studies have examined correlations between cloacal temperatures, environmental temperatures, and activity of spotted turtles (Ward et al., 1976; Ernst, 1982; Lovich, 1988; Wilson, 1994; Mauger, unpubl. data), but none have used temperature-sensitive radiotransmitters to estimate body temperature. Because turtles are l is regarded as vulnerable (Oldham, un. ata). Few published studies have reportabitat use and microhabi at s lection by turtles throughout their a nual act vity ( ard et al., 1976; Graham, 1995; Perillo, ). I deed, nothing is known abou th se asthe species' ecology a the northern limi s range in Ontario where the Canadian is a predominant geologica landform. attempts to develop a comprehensive of the habitat and thermal requirements, al activity pa terns of spotted turtles eorgian Bay, Ontario. 178 This content downloaded from 157.55.39.120 on Mon, 05 Sep 2016 05:07:37 UTC All use subject to http://about.jstor.org/terms HABITAT USE OF CLEMMYS GUTTATA TABLE 1. Dates covered by the subseasons based on spotted turtle (Clemmys guttata) behavior, and mean (+-SE) minimum and maximum air temperatures (C) in Georgian Bay, Ontario in 1993 and 1994.