RELATION BETWEEN ESCAPE BEHAVIOR OF BENTHIC MARINE-INVERTEBRATES AND THE RISK OF PREDATION

Many prey species display defensive behaviours when they detect predat ors. We examine, for six benthic marine invertebrates with strong esca pe responses, the hypothesis that the intensity of escape responses in creases with the risk of mortality from various predators. Data for th e bivalves Serripes groenlandicus (Bruguiere), Clinocardium ciliatum ( Fabricius), Chlamys islandica (Muller), the gastropod Buccinum undatum L. and the holothuroid Cucumaria frondosa (Gunnerus), generally suppo rt the hypothesis. They respond strongly to their most important preda tor and weakly or not at all to unimportant ones. The strongest correl ation between the intensity of the escape response and predation risk was for Buccinum undatum. This may be related to its lack of a pelagic larval phase, as this means that the parents of individuals studied w ere from the community where predation risk was estimated. Data for th e echinoid Strongylocentrotus droebachiensis Muller contradict the hyp othesis. It responds strongly to Leptasterias polaris (Betzius), a sea star which rarely cats urchins, and does not respond significantly to its mean predator Crossasterpapposus (L.).