Characterizing Turtle Nesting Habitat in the Eastern Georgian Bay Region

Abstract

Reptile populations are decreasing throughout the globe, holding the highest proportion of species listed as threatened worldwide. To ensure proper management and conservation for reptile species at risk, it is essential to identify, characterize, and understand the microhabitat environment at critical life stages. Nesting is a critical life stage for turtles, and nest site selection can affect successful hatching. As Ontario is at the northern range limit for native freshwater turtles in the province, selection of nest sites that have high quality thermal and hydrological conditions may be particularly important in this region. Soil-filled bedrock depressions are known nesting habitats of turtles in the Eastern Georgian Bay region and vary in soil texture from the sand environment of turtle nests in more southern populations. Due to the difference in soil from more commonly studied regions, little is known about the nesting habitat in the eastern Georgian Bay area and how landscape characteristics and soil properties further influence the conditions during incubation. We surveyed 48 300m transects in a 660 ha study area, classifying land cover type for all surveyed points, and soil depth, canopy openness, ground cover type, moss and lichen height, slope, and aspect for all points classified as available habitat. Only 22.1% of the surveyed landscape was considered available turtle nesting habitat, and of this, only 2.6-10% of these points (dependent on species) were suitable for nesting (equal to 0.57-2.21% of total points surveyed). Our results demonstrate that suitable turtle nesting habitat in this environment is extremely limited (both by soil depth and canopy cover), with canopy openness being the most limiting factor. Due to the already limited habitat, it is even more important to understand the thermal and hydrological characteristics of nesting habitat in the Eastern Georgian Bay region, so that soil properties can be used to inform creation of habitat. We also determined that a majority of the soil on the landscape is sandy clay loam, with a low organic matter content. The information gained through characterization of the soil can be used to determine appropriate soils for artificial nest construction and ensure more successful methods of conservation for turtle species at risk. We recommend that artificial nesting habitat must have sufficient depth (at least 10cm) and canopy cover requirements (90-100% openness), as these are the most limiting factors. When creating artificial nest habitat, we recommend the use of sandy clay loam soil, due it’s favourable thermal and hydrological characteristics.