Composition, population dynamics, and ecology of the anuran community at Occoquan Bay National Wildlife Refuge, Woodbridge, Virginia

The anuran community of Occoquan Bay National Wildlife Refuge, Woodbridge, Virginia, was sampled by using trapping and visual survey methods from 2002 to 2004, and by call survey methods from 2000 to 2004, to determine its composition, distribution, and population dynamics. Twelve study areas, representing four different microhabitats, were sampled with traps and visual surveys, and call surveys were conducted at eleven breeding areas. A total of thirteen anuran species were detected on the refuge. Twelve species were detected by capture and visual surveys. Rana clamitans, Rana catesbeiana, and Rana palustris were captured in the greatest numbers. Rana clamitans and Rana palustris were captured in the greatest number of sampling areas. Density per hectare was greatest for Rana clamitans, followed by Rana catesbeiana and Rana palustris. Among the microhabitat types that were sampled, species richness and species diversity was greatest in the lowland wet forest areas, with the transitional areas following in diversity. Species richness and diversity was lowest in the grassland and upland forest areas. Using call surveys, Hyla versicolor was added to the anuran inventory developed from capture and visual survey data, for a total of thirteen species. Call surveys indicated that Rana clamitans, detected at 100% of the breeding ponds surveyed, was the most widespread species, followed by Hyla chrysoscelis and Pseudacris crucifer (each detected at 91% of eleven ponds), and Hyla cinerea and Rana palustris (each detected at 82% of eleven ponds). Analysis of call index values indicated that Pseudacris crucifer was the most abundant species. Call surveys were used to assess the breeding effort trends of the thirteen species detected. Regression analysis of call survey data did not indicate a significant increasing or decreasing trend during the survey period for nine of thirteen species. Data collected for Bufo fowler i and Rana sylvatica were insufficient for analysis. One species, Rana catesbeiana, showed an increasing trend in breeding effort, while only Hyla versicolor showed a decreasing trend for the survey period.