Effects of slope, substrate, and temperature on the locomotion of the ornate box turtle, Terrapene ornata

Ornate box turtles, from the Sand Hills of Nebraska, five in a habitat characterized by slopes, a fine sand substrate, and temperatures that can vary greatly, both diurnally and seasonally. We examined the locomotor responses of these turtles to slope, substrate, and temperature. Only 25% of the turtles could successfully walk on slopes as steep as -40degrees. They were better at walking upslope, but their speed progressively decreased as slope increased. As grade increased, they primarily adjusted stride frequency on upslopes but stride length on downslopes. Turtles appear to be much more affected by slopes than are lizards. Speed was significantly reduced on sand substrates in comparison to Styrofoam, and this was primarily because of a reduction in effective stride length. Speed increased with increasing temperature from 20 to 35 C, almost entirely resulting from an increase in stride frequency; however, the Q(10) for locomotor performance was low. Turtle speeds in the field averaged 0.05 m/s, and, although there was a tendency for higher speeds at higher operative environmental temperatures, this was not statistically significant. Within their natural Sand Hill habitat, these turtles are often active under conditions of slope, substrate, and temperature that are suboptimal for locomotion. However, locomotor performance is not adversely affected to any appreciable degree by the potential constraints of their habitat.