Predator Recognition and Escape Responses of Some Intertidal Gastropods in Presence of Starfish

A series of common species of limpets, snails and abalone are shown to have a specific pattern of reaction to any of a series of common carnivorous asteroid species. The pattern of reaction may be regarded as an escape response and is significant as an example of a little studied aspect of invertebrate behavior, specific predator recognition by prey species. 2. The reaction is markedly different from any elicited by other forms of stimuli, including other common animals, plants, inanimate objects, echinoids, holothuroids and even certain other species of starfish which are chiefly herbivorous. 3. Certain species of gastropods do not react although of the same genus as others which do. The significant common denominator of the former appears to be that they are characteristic of ecologic situations where starfish predation must be rare. 4. The tube feet are the only very effective parts of the starfish. A single tube foot torn from a starfish is an adequate stimulus. 5. Although actual contact, as of tube feet to mantle edge, is usually necessary to ensure a response, many instances of the reaction beginning before contact have been observed. Distances of a few mm. up to some cm. are involved. The evidence suggests a chemical signal specific to predatory starfish and effective only on certain-adaptively susceptible-gastropods. 6. The groups concerned are abundant and motile, the number of contacts between them must be great. They are characteristically not found close together even in the situations where both are common. These facts are judged to be a measure of the general ecologic importance of the described specific behavior pattern.