Spatial and predation ecology of whelks in a shallow embayment in the Rachel Carson Reserve, Beaufort, North Carolina
Movement and predation by 56 individuals of two species of whelks, Busycon contrarium (n = 22) and B. carica (n = 34), were studied in a 300 by 600 m high salinity embayment surveyed on a 10 m grid. These large predatory snails were hypothesized to feed and move similarly. Snails were individually tagged and their movements tracked from late August until November 2002. Snails were divided into 3 experimental groups. A group of 13 B. contrarium and 19 B. carica were released where they were found and followed. A second group of 5 B. contrarium and 8 B. carica were released in a specific microhabitat in the embayment and followed for 3 weeks. This group was then re-released in a new microhabitat and followed for another 3 weeks. Movements of the final group of 4 B. contrarium and 7 B. carica were followed for 3 weeks and then each snail was surrounded by eight evenly spaced clams, Merceneria merceneria, at a distance of 14 cm while buried at known compass points. Movements and predation were quantified. Snails that moved were returned to the original location and clams that were eaten were replaced. Although usually found buried, most snails moved daily and movement was microhabitat dependent. Relatively few movements were related to predation. B. contrarium moves more and occupies a larger active space. We reject our hypothesis that B. contraium and B. carica use habitat similarly.
