Predator diet and prey adaptive responses: Can tadpoles distinguish between predators feeding on congeneric vs. conspecific prey?

Abstract

Predator diet can play an important role in facilitating detection of predation risk among prospective prey, and such detection should have adaptive significance in reducing mortality in environments where not all predators confer similar risk. In the laboratory, we tested behavioural and morphological responses of tadpoles from two congeneric frog species (bullfrog ( Rana catesbeiana Shaw, 1802) and mink frog ( Rana septentrionalis Baird, 1854)) to cues from an odonate predator (genus Aeshna Fabricius, 1775). In a separate experiment we found that both frog species had similar baseline vulnerability to Aeshna predation, implying that species’ responses to predators feeding on conspecific vs. congeneric prey also would be similar. Both species reduced their activity in the presence of predators feeding on tadpoles of either species vs. those fed invertebrates (Libellulidae) or not subjected to predators (controls). Bullfrog tadpoles grew bigger than controls when exposed to predators fed mink frog tadpoles only, whereas mink frogs failed to show a comparable response. Neither species exhibited changes in shape that were attributable to predator diet. Our results suggest that closely related frog species do not distinguish between predators feeding on conspecific vs. congeneric prey, implying that selection favours generalized antipredator responses when prey species are subject to similar predation risk.