The Effect of Soil Temperatures on Emergence from Hibernation of Terrapene carolina and T. ornata

Abstract

Dates of emergence from hibernation, and the estimated ambient subsurface temperatures in the hibernacula, were used to investigate the effects of those temperatures on the emergence from hibernation of the box turtles, Terrapene carolina triunguis and T. o. ornata. In the spring, near St. Louis, Missouri, box turtles move from their hibernacula toward the surface of the ground as they follow a minimum ambient temperature of ca. 7 C. They emerge after 5 consecutive days of subsurface (10-20 cm) temperatures of 7 C or higher. An occasional individual (ca. 3% of the instances in this study) emerges prematurely and is unlikely to survive. Should the subsurface temperatures dip substantially below 7 C about the time of emergence, the turtles extend their period of hibernation until the conditions are appropriate for emergence. After emergence, the turtles remain in the vicinity of their hibernacula and, if the surface temperatures drop precipitously, they re-enter the ground. During and after the first warm spring rains they wander away from the vicinity of their hibernacula. Virtually all field observations previously reported in the literature are con- sistent with this analysis of the events surrounding the emergence of Terrapene carolina and T. ornata from hibernation.