Habitat Selection in the Three-Toed Box Turtle, Terrapene carolina triunguis

Abstract

A quantitative study of habitat selection in Terrapene carolina triunguis was conducted from August 1969 through January 1972. Thirtythree microenvironmental variables were measured in the vicinity of 201 form locations. Principal component analysis of these data indicated that temperature, cover and moisture are fundamental aspects of the environment at form locations. Canonical correlation of microhabitat and microclimatic variables showed that the microclimate surrounding forms was primarily influenced by ground cover aspects of the habitat. Moisture variables immediately surrounding the turtle were not correlated with features of the microhabitat, suggesting that turtles select humidity levels independent of prevailing conditions at the surface. Microclimatic factors were measured at the location of 55 active turtles within the study area. The similarity in temperature and humidity levels with those taken at form locations indicated that turtles exist within a relatively limited microclimatic range at all times during seasons of activity. Analysis of form location and trailing information indicated a seasonal shift in habitat utilization from grasslands in late spring and early fall to forested areas in summer, early spring and late fall. Activity in the grassland areas was found to coincide with moderate temperature and peak moisture conditions. At other seasons turtles burrowed beneath the litter in wooded areas to avoid temperature extremes and maintain high humidity.