ELNITSKY, M.E.*; CLAUSSEN, D.L.; Miami University: The Effects of Growth on the Scaling of Locomotor Performance of Juvenile Painted Turtles

Most studies of the locomotor performance of reptiles have focused on lizards, with chelonians, especially hatchlings and juveniles, being largely overlooked. Improved locomotor performance has been implicated in the differential survivorship of larger hatchlings during the nest exodus; however, few supporting data exist. Likewise, few data document the effects of growth and changes in body size on locomotor performance. It has been suggested that growth may constrain locomotor performance through a tradeoff of the allocation of energy. Therefore, we measured both aquatic and terrestrial locomotor performance (i.e., burst speed) at six-week intervals for 30-weeks in juvenile painted turtles, Chrysemys picta bellii, to assess the effects of growth on the scaling of locomotor performance during a period characterized by rapid growth. The scaling relationship between both aquatic and terrestrial locomotor performance and body mass varied significantly over the 30-week measurement period. Initially, measures of locomotor performance of hatchling turtles scaled positively with body mass. However, power function scaling exponents decreased at each six-week interval, such that the scaling of locomotor performance with body mass was significantly lower following the 30-week measurement period. This suggests that if locomotor performance is under strong selection, larger hatchlings may have distinct advantages over smaller conspecifics; however, if smaller hatchlings do survive, such advantages may be reduced or lost over time. The observed reductions of the scaling of locomotor performance may have been the result of a tradeoff between growth rate and further increases of locomotor performance of larger juveniles.