Assateague Island National Seashore amphibian and reptile inventory: 2004-2005

Cook, Robert; Brotherton, David; Timm, Brad; Behler, John

Under a National Park Service/Wildlife Conservation Society Cooperative Agreement, an inventory of amphibians and reptiles on the Maryland portion of Assateague Island National Seashore was conducted from March through September 2004. Additional spotted turtle work continued until June 2005 to assess habitat use and seasonal activity. Five standardized sampling methods were employed; anuran call-counts, time-constrained search, coverboards, turtle traps and minnow traps. In addition, animals encountered outside of standardized surveys (temporally or spatially) were recorded as incidental encounters. We recorded 19 species, 2 migrant (sea turtles) and 17 year-round resident. The 17 resident species included 16 of the 21 (76%) resident species recorded historically (i.e. by mid-1990s) on Assateague Island, plus a new island record, grey treefrog. For the Maryland portion only, the 17 resident species represent 15 of 16 (94%) historically-recorded resident species, plus grey treefrog and common garter snake. The 17 resident species included four anurans, seven turtles, and six snakes. Fowler’s toad and northern black racer were the most abundant and widely distributed amphibian and snake species, based on total number of adults encountered and total number of localities. Among turtles, the northern diamondback terrapin was most abundant and the eastern mud turtle most widespread. “Listed” species were limited to the loggerhead sea turtle (Maryland and federally Threatened) and the leatherback sea turtle (Maryland and federally Endangered), both found washed up dead on the beach. Of the methods used, incidental encounters recorded all 19 species, followed by time-constrained search (14), turtle traps (6), minnow traps (5), anuran calling survey (4) and cover boards (2). Seventeen species were recorded in upland habitats, followed by 14 in freshwater wetlands, and three in marine. The Valentine-Green Run area had the greatest species richness and abundance, accounting for 15 of 19 species and 59.8% of animals recorded. There are relatively few species of amphibians and reptiles on Assateague Island compared to the “mainland” Delmarva Peninsula. Barrier islands typically have low herpetofaunal species richness, dominated by reptiles, due to salt water barriers, environmental stressors, and reduced habitat diversity. The 23 resident species known to have been recorded on Assateague Island, which includes three species introduced by humans, comprise 41% of the 56 resident species recorded on the adjacent mainland: The 18 resident species known from the MD portion comprises 32%. Of these 18 MD species, 14 appear to have stable population trends, two appear to be more common than previously reported, and the remaining two are uncertain. A plan for monitoring is beyond the scope of this inventory, but the results suggest that a monitoring program based on anuran calling surveys, time constrained searches, and surveys of ponds with turtle and minnow traps would be the most useful. Moreover, given the likelihood of more frequent storm overwash due to sea level rise, water quality of “freshwater” wetlands should also be monitored. It would appear that sea level rise, and its direct and indirect effects (e.g. loss of amphibians from food chain), is the single most pressing challenge to the survival and integrity island’s herpetofaunal community.

Assateague Island National Seashore amphibian and reptile inventory: 2004-2005

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