Effect of an alien turtle predator on movement activity of European brown frog tadpoles

Abstract

An increasing amount of attention has been devoted to studying the impact of non-native plant and animal species on native species. In this paper, we examined the antipredator response of naïve European brown frog (Rana temporaria Linnaeus, 1758) tadpoles to water-borne chemical cues from invasive red-eared slider turtles (Trachemys scripta elegans Wied, 1838) in the presence and the absence of conspecific tadpoles. The level of swimming activity was expressed as the length of the tadpoles’ trajectory. The tadpoles showed a decrease in swimming activity when predator stimuli were present, which was highly significant when the tadpoles were measured individually and did not have contact (visual and chemical) with other tadpoles. In the absence of chemical cues of slider turtles, the presence of other tadpoles had no effect on the level of swimming activity. Moreover, for the first time in tadpoles, we found that the decrease in swimming activity was also accompanied by changes in swimming trajectory, with tadpoles exposed to predator cues swimming in more zigzagged trajectories. Our experiment shows that invasive slider turtles, as a novel predator, have a measurable influence on the swimming behaviour of European brown frog tadpoles. Consequences of the reduced swimming activity of tadpoles, like its impact on growth, are discussed.