The Interactive Effects of Fish Predation and Conspecific Density on Survival and Growth of Tadpoles of Rana sylvatica in a Subarctic Wetland

In nature, prey are often simultaneously exposed to predators and competitors, leading to conflicting demands between survival and growth. Larval amphibians are model organisms to investigate the balancing of life history trade-offs because individuals must metamorphose before a wetland dries. Therefore, we deployed enclosures in a natural wetland to investigate the interactive effects of Wood Frog (Rana sylvatica) density (50 or 100 tadpoles) and Brook Stickleback (Culaea inconstans) presence on survival and growth of tadpoles. We hypothesized that the effects of conspecific density on tadpole survival and growth would be dependent on the presence of fish predators. Stickleback predation significantly decreased Wood Frog survival; however, a trend of higher tadpole survival with fish was detected at high conspecific densities. Wood Frog time to and mass at metamorphosis was not significantly affected by either conspecific density or stickleback presence. Our results demonstrate that Brook Sticklebacks can play a significant role in regulating Wood Frog survival in a Subarctic wetland, but the impact is likely dependent on tadpole density. Therefore, this research highlights the dynamic and complex effects of competition and predation in a Subarctic wetland. Our study also contributes to the limited understanding of factors affecting amphibian community structure in Subarctic wetlands.