Body shape, burst speed and escape behavior of larval anurans

Variation in behavior, morphology and life history traits of larval anurans across predator gradients, and consequences of that variation, have been abundantly studied. Yet the functional link between morphology and burst-swimming speed is largely unknown. We conducted experiments with two divergent species of anurans, Scaphiopus holbrookii and Rana sphenocephala, to examine how behavior and morphology influence predator vulnerability, and whether tadpole shape is related to burst-swimming performance. Scaphiopus holbrookii, a species that typically uses ephemeral pools, was more active, exhibited slower burst speeds, and was more susceptible to predation than R. sphenocephala, a species associated with more permanent aquatic sites. Our analysis of morphology and burst speed defined a shared axis of shape variation associated with burst-swimming speed regardless of species. Tadpoles with a deeper tail fin and muscle and a smaller body produced faster speeds. The nature and breadth of the morphology-speed relationship suggests it may represent a generalized ecomorphological paradigm for larval anurans.