Excerpt: ...on overcast days in early May. In 78 box turtles that were under cover because their environmental temperatures were low, the body temperatures ranged from 2.7 to 30.6 degrees (mean 19.8 ± 6.38σ). The range of body temperatures in this group is greater than in the other groups shown in Figure 22 because low body temperatures were studied over a wide range of conditions, including hibernation. Box turtles actually seek cover because of low temperatures only in fall and spring and on occasional unseasonable days in summer when temperatures drop rapidly. Retreat to cover, in the normal cycle of daily activity, is governed usually by high temperatures at mid-day or by darkness at the end of the day. Turtles in dens, burrows, and grass forms, tended to burrow if temperatures remained low for more than a few hours. Box turtles under cover where they cannot bask have little control over the lower range of body temperatures. The freezing temperatures of winter can be escaped by burrowing deeper into the ground. Temperatures approaching the lethal minimum, however, seldom occur during the season of normal activity. By remaining hidden in a burrow or den therefore, box turtles are fairly well protected from predators but are at a thermal disadvantage. A number of turtles that had wet mud on their shells were found basking in early morning near ditches, ponds, and marshy areas; several others were partly buried in mud, shortly after daybreak, and another was at the edge of a pond after dark. Eight adults, located just as they emerged from cover in early morning on sunny days, had body temperatures of 19.7, 21.9, 24.2, 24.5, 25.8, 26.6, 28.7, and 29.5 degrees. In five emerging from earth forms, body temperatures were at least a degree or two below the temperature of the air; the other three came from mud or shallow water and had body temperatures higher than the air temperature. Temperature is probably the primary stimulus governing emergence after...
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