HOLLOWS, PEEPERS, AND HIGHLANDERS: AN APPALACHIAN MOUNTAIN ECOLOGY

19. Box Turtle’s Independence

127 19 Box Turtle’s Independence F ew of us purposely search for box turtles, so it’s no wonder we have few first-hand impressions of them in their natural habitat . However, most of us have vivid memories filed away of desperate swerves to avoid squashing their high domes on the road. Instead of allowing the image of a lethargic, indifferent creature to mislead you, envision these pedestrians as animals enviably insulated from the vagaries of their setting. In fact, land tortoises seem more divorced from environmental stresses than any other Appalachian vertebrate. The turtle’s habitat provides our first hint of its independence. Box turtles live in a variety of terrestrial situations — though permanent water does not seem to be a requirement. High densities of these reptiles commonly occur in woodlots with large trees, canopy gaps, and a diversified ground cover. The turtles bask in openings in the canopy and munch on a variety of short plants. The close ground cover of woody shrubs and leaf litter provide shelter. To feed and bask, box turtles also frequently enter open areas adjacent to the woods. Much of what we know of box turtle biology comes from the labors of Charles and Elizabeth Schwartz, biologists who tracked tortoises for twenty years. By training Labrador retrievers to locate and retrieve turtles, they were able to study unprecedentedly large numbers . During nineteen years of the Schwartzes’ study, the average size of the area a turtle covered routinely, or its home range, increased from 5.2 to 12.8 acres. Home ranges were essentially equal for males 128 and females. Another study at a different field site concluded that box turtles restrict their movements to home ranges that average only about one hundred yards in diameter, which translates to about 2.5 acres. For comparison, the home ranges of snapping and wood turtles, two Appalachian relatives, average 8.4 and 3.2 acres, respectively. When not traveling, box turtles rest in forms, depressions made in vegetation and the top inch of soil. During their active season , April to October, they remain in their forms until the morning sun warms them, then travel slowly and feed for about an hour. If it is sunny but cool, they bask; if it is hot they may crawl under a few leaves or a clump of grass. A turtle may meander up to seventy yards per day, or it may move just a foot or two before making a new form for the night. On any given day, one turtle might be active while another is quiescent. Some individuals are simply more sedentary than others. Intuitively, it seems that resting forms should contribute to a turtle’s independence from environmental changes because the form insulates the turtle’s belly plate, or plastron, during hot days and cool nights. However, recent study suggests that there is no pattern in when or why turtles occupy their forms. Use is not related to an individual’s sex or size, nor to a consistent difference in air or soil temperatures. Neither have we found an obvious reason for how long they stay in a form. In essence, each individual box turtle seems to have its own internal agenda, acting independently of the environment in determining when or where to settle into a resting form or how long to stay there. One environmental condition turtles do respond to is a cold snap in autumn. Box turtles enter hibernation with the first killing frost. A wet fall without a sudden freeze provides good conditions for entering hibernation. Dry weather, which makes digging difficult , and a sudden freeze may trap some individuals above ground. Surprisingly, box turtles do not hibernate below the frost line, but remain dormant at depths of up to five inches below the leaf litter. Since the original Hollows, I have learned some amazing facts about the box turtle’s hibernation. Members of the genus Terrapene, Hollows, Peepers, and Highlanders 129 which includes the eastern box turtle, hibernate in shallow terrestrial burrows that feature a vertical extension to the surface. In cold spells, turtles turn their heads farthest from the opening. In Ohio, the average turtle spends 142 days in a burrow under three inches of leaf litter with its plastron recessed two inches into the soil. In such shallow retreats, box turtles are exposed to freezing temperatures, yet they usually survive. Able to supercool to only...