Shell Selection and Invasion Rates of Some Pacific Hermit Crabs

Abstract

Three species of littoral hermit crabs from Horseshoe Cove, Bodega Head, Sonoma County, California, and three sublittoral pagurids from Chinimi Island, Eniwetok Atoll, Marshall Islands, have been examined with respect to their shell selection and invasion rates. Periodic removal of crabs from marked areas resulted in immigrations of surprising magnitude. By comparison of actual collection patterns with those predictable from the alternates of density dependence and density independence, there is an indication that the observed immigration rates result from density dependent dispersal. While our data are not conclusive, the method presented is of interest and of possible utility for examining problems of this nature. Shell selection is discussed from the bases of both laboratory and field observations. Each of the species is shown to utilize the shells of different gastropods with different frequencies. Finally, behavioral aspects are examined as they relate to the distribution of the California hermit crabs.