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Effect of human disturbance on the abundance and spatial distribution of the Atlantic Ghost crab (Ocypode quadrata) (Fabricius 1798) on a Texas beach.

Article Excerpt
Abstract. -- Atlantic Ghost crab (Ocypode quadrata) activity was investigated along two sections of beach on the Bolivar Peninsula, Texas. One study site was in an area of high human activity in which significant alterations to the beach has occurred, and the other site was in a protected bird sanctuary with very low human activity and little beach alteration. Using line transects as a sampling technique, measurements of burrow characteristics were conducted. These included the total number and density of burrows; the diameter and compass orientation of burrow openings; the distance of burrow openings to the high water line, and the proximity of neighboring burrows. A sample of captured crabs was measured along with their burrows to determine the strength of the relationship between the size of a crab and its burrow opening. Burrow opening size and compass orientation did not differ between the two study sites, but burrow density was higher in the low-impact area, and the location of the burrow openings was further from the water on this protected beach. The ecological ramifications of these findings are discussed.

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Ghost crabs (Decapoda: Ocypode) (Fabricius 1798) are found on sandy beaches throughout the world's tropical and subtropical zones (Brown & McLachlan 1990), and act as scavengers and predators on other littoral macroinvertebrates (Wolcott 1978). Ghost crabs construct burrows of varying size and depth where they spend most of their daylight hours (Hill 1981; Chan et al. 2006). The location and orientation of these burrows in relation to the beach may be dictated by both natural conditions (Hill 1981; Turra 2005) and human activities (Steiner & Leatherman 1981; Peterson et al. 2000). The correlation between ghost crab activity and anthropogenic alterations to beaches has been considered strong enough to allow a count of burrow openings to be used as a quick measure of human impacts on such beaches (Barros 2001).

The widely distributed Atlantic Ghost Crab Ocypode quadrata (Fabricius) ranges from Rhode Island to Brazil, and is the species found throughout the Gulf Coast, including the Bolivar Peninsula (Amos & Amos 1985). The beachfront property on much of this peninsula is extensively developed with homes, motels, and commercial establishments, and much of the beach itself is open to human and vehicular traffic. Most such human impacts are absent in the Bolivar Flats Shorebird Sanctuary, located...

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