A functional analysis of how frogs jump out of water

Abstract

Euphlyctis cyanophlyctis and E. hexadactylus are two common frog species from south-east Asia. Both species have the remarkable ability to leap from a floating position out of the water. Rana esculenta is a European species from the same family that barely manages to do so. The species' morphology, however, looks roughly the same. We studied the unique abilities of the Euphlyctis species by videotaping the three species mentioned above whilst they jumped out of the water. These recordings enabled us to study the hind leg movements and to test several hypotheses. Differences between the species only became apparent when details of the behaviour were analysed. The three species mainly differed in their slip factor at the start of the propulsive phase, resulting in a difference in slip distance. This difference could be traced back to the difference in web shape by means of a physical model. The Euphlyctis species can prevent their feet from slipping because of their rounded and convex webbing, resulting in a larger take-off velocity and thereby a successful emergence out of the water.

Pygmy mole crickets jump from water

“…The generation of thrust is possible because of the viscosity of water relative to body size; the paddles and spurs act in a similar way to the smaller hairs on the moving mouth parts of copepods [5]. By contrast, frogs [6] and basilisk lizards generate a turbulent flow beneath their wide and flat feet (Reynolds numbers 5000-15000) and to run on water, a basilisk lizard must maintain a pocket of air above its feet [7,8]. Pygmy mole crickets and copepods therefore exploit the viscosity of water, basilisk lizards its mass, and pond skater insects [9], and fisher spiders [10] its surface tension.…”

Built for rowing: frog muscle is tuned to limb morphology to power swimming

“…Less celebrated is their impressive swimming ability [5][6][7] which has revealed important mechanisms of fluid propulsion [8][9][10], making frogs ideal models to probe the limits of muscle-powered swimming.…”

Do all frogs swim alike? The effect of ecological specialization on swimming kinematics in frogs

“…To date, most of our knowledge on frog locomotion is based on data for a limited set of derived frogs including ranoids [mostly ranids and bufonids (Calow and Alexander, 1973;Lutz and Rome, 1994;Kamel et al, 1996;Peters et al, 1996;Olson and Marsh, 1998;Gillis and Biewener, 2000;Nauwelaerts and Aerts, 2002;Nauwelaerts and Aerts, 2003;Nauwelaerts and Aerts, 2006;Nauwelaerts et al, 2001;Nauwelaerts et al, 2004;Nauwelaerts et al, 2005a;Nauwelaerts et al, 2005b;Johansson and Lauder, 2004;Stamhuis and Nauwelaerts, 2005)] and highly specialized aquatic pipids (Gal and Blake, 1988;Richards and Biewener, 2007;Richards, 2008;Clemente and Richards, 2013). A comparison of swimming kinematics between the highly specialized aquatic pipids and more generalized terrestrial species showed differences in joint kinematics, indicating differences in the underlying propulsive strategies of swimming across species (Richards, 2010).…”