Journal of Animal Ecology 1992 61, 353-360.
Modification of anti-predator behaviour in tadpoles by environmental conditioning

RAYMOND D. SEMLITSCH and HEINZ-ULRICH REYER Institute of Zoology, University of Zörich, CH-8057 Zörich, Switzerland

1. We examined the anti-predator behaviour of two closely related species of tadpoles (Rana lessonae and Rana esculenta). Eggs were hatched in the laboratory and tadpoles were conditioned for 30 days to fish, newts, odonates and Bufo tadpoles before testing tadpole responses to predator and control stimuli. 2. Rana esculenta tadpoles spent more time swimming than did R. Iessonae tadpoles, but species did not differ in refuge use. 3. Conditioning treatment affected both the percentage of time spent swimming and use of refuge. Time spent swimming was highest in tadpoles conditioned to Bufo tadpoles and lowest in those conditioned to the three predators. Time spent in the refuge was highest in tadpoles conditioned to fish, newts, and odonates and lowest in those conditioned to tadpoles. Species of tadpoles differed in their responses to conditioning, R. esculenta spent more time swimming when conditioned to tadpoles whereas R. lessonae spent less time swimming when conditioned to odonates than the other species. 4. In predator treatments, tadpoles exposed to fish predators increased time spent in the refuge compared to odonates, newts, and the tadpole and water controls. Exposure to fish, newts, and odonates decreased the percentage of time spent swimming. In addition, there was a significant conditioning X predator interaction on swimming and open-water use. 5. Our results show that R. Iessonae and R. esculenta tadpoles possess inherited differences in anti-predator behaviour which may be interpreted as general adaptations to aquatic environments, but that conditioning to predators can modify or 'fine-tune' their response to specific environments.

Key-words: amphibian, anti-predator behaviour, microhabitat, Rana, tadpole.

Anim. Behav., 1993, 46, 355-364