Population Responses of Wood Frog (Rana Sylvatica) Tadpoles to Overwintered Bullfrog (Rana Catesbeiana) Tadpoles

Abstract

A fundamental goal in ecology is to understand how environmental variation influences the distribution of individuals within a population. In this study, we used laboratory experiments to examine the population responses of sympatric Wood Frog (Rana sylvatica) tadpoles to native overwintered Bullfrog (Rana catesbeiana) tadpoles. For periods of up to two weeks, we measured growth, activity, and refuge use of Wood Frog tadpoles in small mesocosms with and without an overwintered Bullfrog tadpole present. Bullfrog tadpoles had a negative effect on the growth of Wood Frog tadpoles allotopic (naïve) to Bullfrogs, whereas the presence of Bullfrogs had no effect on growth of syntopic (experienced) Wood Frog tadpoles. There were also differential behavioral responses of the Wood Frog populations to overwintered Bullfrog tadpole visual and chemical cues. Only allotopic Wood Frog tadpoles decreased activity levels and increased use of refugia in the presence of overwintered Bullfrog tadpoles. These observations indicate overwintered Bullfrog tadpoles might exert a selective pressure on sympatric Wood Frog tadpoles, and that experience might allow for the development of strategies to maximize performance for species coexisting with overwintered Bullfrog tadpoles.