CIRILO, S.R.**; HILL, S.; ESPINOZA, N.R.; BLOB, R.W.; Erskine College, Due West, SC; Erskine College, Due West, SC; Erskine College, Due West, SC; Clemson Univ., SC: Limb Bone Strain Rates in Divergent Locomotor Modes: Turtles and Frogs Compared

Empirical data indicate that bones experiencing higher rates of strain during loading can withstand greater strain magnitudes before yield failure. Here, we test for potential differences in strain rate that could affect load bearing capacity in two vertebrate lineages with dramatically different locomotor habits: emydid turtles, which typically walk slowly, and ranid frogs, which typically use rapid jumps. Strain rates were collected in vivo from strain gauges implanted on the femur of multiple individual river cooters (Pseudemys concinna) and bullfrogs (Rana catesbeiana). Strain recordings were made as the animals walked or jumped on a treadmill while being filmed with high-speed video. Strain rate was positively correlated with strain magnitude in each species. In addition, the time of foot contact with the ground for jumping frogs was as much as four times shorter than that for walking turtles. This difference likely contributes to the substantially greater peak strain rates found in frogs versus turtles. Thus, differences in limb bone loading rates between turtles and frogs could contribute to differences in load bearing capacity of the limb bones between these lineages.