Using the Phenology of Pond-Breeding Amphibians to Develop Conservation Strategies

Researchers suggest that regulatory agencies interested in protecting pond-breeding amphibians should consider wetland isolation, wetland size, and pond hydroperiod (total number of days pond is flooded annually) when modifying existing wetland regulations. Another criterion that has received less attention is the effect of the timing of inundation on the reproductive success of pond-breeding amphibians. Over 3 years, we monitored the timing of movements of adult and recently metamorphosed anurans and caudates at seven small, isolated wetlands in southern Rhode Island. Based on dates of immigration for adults and emigration for metamorphs, we concluded that different species of amphibians require ponds to be flooded for 125 days to at least 580 days. For species that breed primarily in seasonally flooded ponds, 95% of metamorphs had emigrated from breeding ponds by 31 July in only two species (   Rana sylvatica and Ambystoma opacum), whereas species using semipermanent ponds required inundation until 18 November. Our results suggest that in most years ponds must be inundated for 4-9 months, with water in ponds from March through August, for successful reproduction of the majority of pond-breeding amphibians in Rhode Island. We recommend that biologists gather data on amphibian movement phenology in other regions to help regulators and managers develop relevant legislation to protect the habitat of pond-breeding amphibians.