CLAUSSEN, D.L.*; LIM, R.; KURZ, M.; WREN, K.: The effects of slope, substrate, and temperature on the locomotion of ornate box turtles.

Ornate box turtles, Terrapene ornata, from the Sandhills of NE, live in a habitat characterized by slopes, a fine sand substrate, and temperatures that can vary greatly. We examined the locomotor responses of the turtles to these factors. Only 25% of the turtles could successfully walk on slopes as steep as -40°. 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 compliant (i.e.sand) substrates, and this was due primarily to a reduction in effective stride length. Speed increased with increasing temperature from 20 to 35 °C, due almost entirely to an increase in stride frequency; however, the Q₁₀ 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 temperatures, this was not statistically significant. Within their natural Sandhill 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 major degree by the potential constraints of their habitat.