5 km offshore near Cedar Key on the Gulf coast of north-western peninsular Florida (Fig. 1). Biological communities on this island are diverse and include salt marsh, mangroves and a mixed hardwood hammock that covers much of the upland area of the island. The island is part of the Cedar Keys National Wildlife Refuge and supports

a large rookery of colonial-nesting water birds. The rookery is concentrated largely at the western half of the island, and there is a white sand beach that extends in a large arc along its southern edge (Fig. 1). Cottonmouths feed largely on fish carrion and are most abundant in or near the hammock, which supports the colonial bird rookeries (Lillywhite & McCleary, 2008). From June 2000 to September 2010, the activity of cottonmouths was monitored along a stretch of the south beach that extended from a midpoint on the island to a point 750 m to the west (Fig. 1). Beginning at Selleckchem PFT�� dark, several persons (range 1–5, mean ACP-196 nmr 2.5) walked over this area carefully searching each segment and proceeding once in each direction with respect to the length of the beach. We looked for snakes that were easily seen foraging in relatively open ground above the intertidal near the edge where beach transitioned to hammock. Rookery trees, largely supporting nests of Brown

Pelicans, Pelecanus occidentalis, and Double-crested Cormorants, Phalacrocorax auritus, could be found at varying distances along this path. Snakes were encountered in larger numbers on relatively open ground beneath these trees, which were either rooted on the beach or had canopy extending over the beach. The observers walked with headlamps, and snakes were easily observed in artificial light either crawling, feeding or coiled. The snakes were not disturbed by a beam of light and moved away only when the observer came very close to the snake (typically within 1 m). Because inactive snakes are usually coiled in sheltered or concealed sites within the hammock and emerged at dark to move below rookeries, including open areas at the edge of the beach, we used the number of snakes sighted as an index of snake activity.

find more Each survey lasted from 60 to 90 min, depending on time taken to photograph snakes or record other information. Surveys were conducted largely during the period from March to November when snakes were nocturnally active. Overall, during 77 searching transects, we sighted a total of 860 snakes (mean 11.17 snakes per night; range 0–44). We recorded the location and estimated the size of each snake that was sighted during visual surveys beginning at dark. The observers were close enough to snakes to estimate the total length and to place each individual within a size category (young-of-the-year below 45 cm; juveniles 46–75 cm; and adults >75 cm). To ensure consistency on both the survey procedures and the field size estimations of the snakes, H. B. L. was present during all the observation sessions.