The Relation of Air Breathing and Locomotion to Predation on Tadpoles, Rana berlandieri, by Turtles

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Abstract
To examine how air breathing affects susceptibility to predation in anuran larvae, predatory encounters were staged between tadpoles of the frog Rana berlandieri and turtles (Chrysemys picta) in a laboratory setting. Swimming and air-breathing movements of tadpoles increased the distance at which turtles recognized and attacked tadpoles. Turtles attacked only one nonmoving tadpole more than 30 cm distant but attacked moving tadpoles up to 175 cm distant. However, only 5% of tadpoles attacked while moving were actually swimming to breathe air. Locomotor stamina (and hence its enhancement by air breathing) had little bearing on the outcome of predatory encounters. Encounters (no. = 171) averaged 11.4 s (SD = 7.0 s), and fewer than 10% exceeded 20 s. Tadpoles' escapes from turtles involved burst speed or maneuverability rather than stamina. Escaped and captured tadpoles differed in speed and number of abrupt turns, but not in distance swum and swimming time. Lactate concentrations of tadpoles did not change during simulated predatory encounters. Tadpoles increased movement after a predator's attack. The data suggest that air breathing increases tadpole recognition by visually oriented predators and does little to aid a tadpole's escape in a predatory encounter. Thus, the real benefit of air breathing to most tadpoles in nature remains an open question.