Interactions between recently metamorphosed green frogs and American toads under laboratory conditions

Many research studies have focused on the interactions among larval anurans, but relatively little is known about competitive or predatory interactions among anurans following metamorphosis. The purpose of our study was to examine the effects of post-metamorphic green frogs (Rana damitans) on post-metamorphic American toads (Bufo americanus) in the terrestrial environment as a model for understanding how interspecific differences in size at metamorphosis may influence terrestrial interactions. We examined if caged, uncaged or no green frogs affected survival, growth and hiding behavior of recently metamorphosed American toads in a replicated laboratory experiment. Green frogs did not appear to prey upon small American toads. However, by the end of the experiment American toad survival was lowest in treatments with uncaged green frogs; this result suggests that green frogs may outcompete American toads for food, but such impacts in nature may be limited or may have selected for spatial segregation in the terrestrial environment. Green frogs also increased hiding activity of toads at some times, which may in part explain the trend of reduced mass gained when toads were reared with green frogs. This study represents one of the first to examine interspecific interactions among anurans with complex life cycles in the terrestrial environment.
INTRODUCTION Amphibians with complex life cycles have different strategies to deal with biotic and abiotic pressures in aquatic and terrestrial environments (Wilbur and Collins, 1973; Werner, 1986). Alterations in length [...]