Ecology of the Eastern Cottonmouth (Agkistrodon p. piscivorus) at Back Bay National Wildlife Refuge: A Comparative Study of Natural and Anthropogenic Marsh Habitats
Mark-recapture sampling and radiotelemetry were used to investigate populations of the eastern cottonmouth, Agkistrodon p. piscivorus, in both natural and anthropogenic marsh habitats at Back Bay National Wildlife Refuge (BBNWR), Virginia Beach, Virginia from autumn 1995 to late spring 1998. Mark-recapture subjects were captured, marked by ventral scale-clipping, and released back into the population. A modified Schnabel Census estimator was used to estimate population sizes and corresponding densities in both marsh systems based on a total of 244 captures of 222 individuals. Most snakes were found >0.05 in from water, but it was apparent that proximity to water played a major role in the distribution of these snakes. Most snakes were found with the body extended and in direct sunlight regardless of temperature; live vegetation served as the primary cover object for these snakes. The majority of captures were male snakes, and few gravid females were captured in either marsh in either year. Many snakes fled before capture. Snakes fled in the direction opposite the investigator no matter which medium (land or water) they occupied at the time. Aggressive behaviors were rare. Radiotelemetry subjects were captured, removed to the laboratory for radiotransmitter implantation, and subsequently released at the initial capture location. Snakes were tracked from 83–208 days, and between 54 and 101 observations were made for each subject. Snakes in the anthropogenic marsh moved greater overall distances than did snakes in the natural marsh. Discriminant Function Analysis based on comparisons of use and non-use sites and Polytomous Logistic Regression, based on use-intensity classification of sites used by radiotelemetry subjects both suggested that the most important habitat variables for determining sites used by cottonmouths in both marshes were: distance to water, distance to overstory trees, leaf litter cover, and vegetation cover. Gut analyses suggested that frogs (Rana spp.) and sunfishes (Lepomisspp.) were the primary prey sources. Snakes hibernated both singly and together. The greatest single concern for future populations of cottonmouths at BBNWR is likely the availability of adequate cover, particularly in terms of the conversion of areas containing hibernacula to management impoundments
Agkistrodon piscivorus, Back Bay National Wildlife Refuge, Eastern cottonmouth, Marsh, Virginia, Ecology and Evolutionary Biology, Forest Sciences, Zoology
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