ABSTRACT
Multiple species of frogs in the Ranidae family have been observed to ‘skitter’ across the water surface, but little is understood about the biomechanical or physical mechanisms that underlie this behavior. All documented descriptions are anecdotal, asserting simply that the frogs can cross the water surface without sinking. To study this form of interfacial locomotion, we recorded high-speed video of the northern cricket frog Acris crepitans and quantified its kinematics. We also compared its semi-aquatic behavior with the frogs' terrestrial locomotion. Contrary to expectations based on anecdotal knowledge, we found that cricket frogs do not maintain an above-surface position throughout the locomotor cycle. Instead, the frogs are completely submerged during both the launching and landing phase of a jump cycle, similar to porpoising in other animals. It is possible that leg-retraction time constrains these frogs from performing true surface-only locomotion.
Footnotes
Author contributions
Conceptualization: T.W., G.B.G., J.J.S.; Methodology: T.W.; Software: T.W.; Validation: J.V.M.; Formal analysis: T.W., J.V.M.; Investigation: T.W., J.J.S.; Resources: J.J.S.; Data curation: T.W.; Writing – original draft: T.W., G.B.G., J.J.S.; Writing – review & editing: T.W., G.B.G., J.V.M., J.J.S.; Visualization: T.W.; Supervision: G.B.G., J.J.S.; Project administration: J.J.S.; Funding acquisition: J.J.S.
Funding
This work was supported by grants from the National Science Foundation (0966125 and 1205642 to J.J.S.) and the Institute for Critical Technology and Applied Science at Virginia Tech (to J.J.S.). T.W. was also supported by the BIOTRANS (Biological Transport) interdisciplinary graduate education program at Virginia Tech.
Data availability
Additional supplemental material is available on figshare (doi:10.6084/m9.figshare.20720935.v1) and GitHub (https://github.com/TheSochaLab/Skittering.locomotion.in.cricket.frogs).
