Amphibian production in forested landscapes in relation to wetland hydroperiod: A case study of vernal pools and beaver ponds

Many amphibian species are plastic in their selection of breeding sites and use both short- and longer-hydroperiod wetlands. Understanding which wetland types are most important to amphibian production is critical for focusing conservation efforts. We compared reproduction of wood frogs (Rana sylvatica) and spotted salamanders (Ambystoma maculatum) and production of wood frog juveniles between seasonal (vernal pools) and semi-permanent (beaver-created ponds) wetlands in the central Adirondack region of the northeastern United States. In 65 seasonal wetlands and 37 semi-permanent wetlands over 3 years, densities of wood frog egg masses were similar, but seasonal wetlands contained 4× as many spotted salamander egg masses as did semi-permanent wetlands. For wood frogs, survival to metamorphosis and juvenile production were an order of magnitude higher in semi-permanent wetlands. Models of wood frog production linked to the climatic record predicted that, depending on annual variation in rainfall and survival to metamorphosis, semi-permanent wetlands may produce annually 1.2-23× the number of wood frogs that seasonal wetlands produce within the study area. Models incorporating variation in demographic traits throughout the range of wood frogs suggest that higher survival to metamorphosis in beaver ponds and higher clutch densities in vernal pools strongly influence metamorph production on a regional basis. Semi-permanent wetlands make major contributions to amphibian production in our region and may also be an important source of colonists to seasonal wetlands following periods of drought. Protection of wetlands along the landscape-level continuum of hydroperiod therefore may be critical for maintaining and restoring amphibian populations.