SHELL EXCHANGE BEHAVIOR IN THE HAWAIIAN HERMIT CRAB CALCINUS HAZLETTI (DECAPODA, DIOGENIDAE)

摘要

All animals must have behavioral mechanisms that allow them to obtain needed resources such as food, mates, and protection from predation. The latter can involve evasive behaviors or the use of shelters that make successful predation less likely. A classic example of effective shelter use is the occupation of empty gastropod shells by hermit crabs. The soft abdomen of hermit crabs makes the use of a gastropod shell extremely important thus it is not surprising that hermit crabs have a variety of waysthat shells can be obtained as crabs grow and need new shells. Crabs could find an empty shell (Scully, 1979), orient to a gastropod predation site where a new empty shell will become available (McLean, 1974), or engage in shell exchange behavior with another hermit crab. Shell exchange attempts can be either intraspecific (Hazlett, 1966) or interspecific (Hazlett, 1983). And in most species of hermit crabs, both intraspecific and interspecific exchanges follow the negotiations model (Hazlett, 1978) inwhich both crabs gain in shell fit (how close a shell is to the preferred shell volume for that size crab) from an exchange rather than the aggression model in which the initiator forces the non-initiator out (Elwood & Glass, 1981; Dowds & Elwood, 1983,1985) and the non-initiator winds up with a shell worse in shell fit than it previously occupied.