Meeting Abstract
Frogs are known for their saltatorial locomotion, which is comprised mainly of repeated jumps and landings. We wished to determine how the characteristics of these landings vary between two species that differ in body masses and lengths: Lithobates pipiens (means=65g, 9.8cm) and Lithobates catesbeianus (means=272g, 16.3cm). We used a force plate and ADInstruments LabPro Software to measure the magnitude and duration of impact forces. Landing forces for each species were almost always characterized by two main peaks, the first during forelimb contact and subsequent deceleration, and the second when the bulk of the body hits the ground. L. catesbeianus had greater peak impact forces in the horizontal and vertical directions than L. pipiens, as well as longer total durations. However, when normalized for mass, L. pipiens had significantly higher maximum impact forces per gram than its larger counterpart, with the smaller pipiens reaching approximately 2.4 times their body mass, and catesbeianus topping out at 1.7. Lithobates pipiens absorbed much more of the impact with its forelimbs, as the second peak showed a larger decrease from the initial impact force. When size was accounted for in timing, we found that the two species showed differences in the manner of their deceleration. Per gram, L. catesbeianus spend significantly more time braking on the vertical axis than L. pipiens, while L. pipiens, decelerated significantly more on the horizontal axis during landing. Per centimeter, L. pipiens spent more time decelerating in both directions. It should also be noted that, while almost all timing variables showed significant differences between the species, the time between the initial and second peaks did not differ, suggesting that frogs share deceleration behaviors regardless of mass, and may hint at limitations of the endurance of muscle contractions in their forelimbs.
