Navigating the thermal landscape: thermo-spatial ecology of wood turtles (Glyptemys insculpta) in the north

Abstract

Thermal ecology studies of ectotherms, like turtles, have typically focused on a species' thermal preferences and tolerances, or on thermoregulation site selections; only recently have landscape-scale thermal ecology studies been performed. I examined the spatial and nesting ecology of wood turtles in Sudbury District of Ontario, Canada, in a thermal context. I also measured the thermal impacts of natural resource extraction on wood turtle habitat. Wood turtles (Glyptemys insculpta) cover a wide variety of terrestrial and aquatic habitats during their annual cycle, making them ideal for thermo-spatial studies. I tracked movements and thermal use of 15 radio-tagged adult turtles during the active season, comparing their selections to temperature monitoring stations spread in an array across the study area, to determine if the turtles are navigating a thermal landscape. Temperature had minimal influence on home range-scale movements, but possibly influenced movements at a smaller spatial scale. I compared the thermal landscape (using thermal imagery), soil moisture, and grain size distribution of 3 nesting beaches to determine the strongest predictor of nest-searching behaviour. Temperature range appeared to be an important cue, but females were apparently using a suite of cues to select their nest sites. I mapped the thermal landscapes of six sites: two relatively undisturbed wood turtle habitat sites, two recently-harvested forestry sites, and two active gravel pits, to find the effects of resource harvesting on wood turtle habitat. The undisturbed sites were cooler and less variable than the disturbed sites, and provided higher-quality thermal habitat. My results support the findings of previous studies: that temperature is a stronger driver of turtle behaviour at the micro-habitat scale than the home range scale, and that soil temperature co-varies with soil structural variables at the micro-habitat scale. The data from the habitat mapping provide useful information for conservation efforts when mitigating or rehabilitating wood turtle habitat.