Further Aspects Of The Predation By Rats On Various Mollusc Species

Abstract

The predation by the rat, Raiius nomegicus, on different terrestrial and aquatic Molluscs lias been investigated in some localities of the Po River Valley. 1. Although not casily assessed, it is possible to infer predation by rats because of the frequent habit of collecting and eating prey in particular feeding places, through the breakage patterns of the shells, and by the occurrence around the shell remains area of tracks and scats. 2. For each of the 15 stations in both the inner and coastal waters of the Po River Valley, prey species arc listed as well as the characteristics of predation with respect to conditions in each environment. 3. Mollusc defense mechanisms displayed against predators are discussed. These mechanisms, usually passive (shape and size of shells, criptic colourations) do not seem efficient enough to reduce predation by rats. Even active mechanisms, like the possibility for Gastropods to discharge irritating substances or the ability by Bivalves to bury themselves, are nullified by the high degree of specialization achieved by rats in this kind of predation. 4. Predation and the several problems to be solved in this concern by rats are studied separately for Gastropods and Bivalves. The authors briefly refer to the Crustaccan Carcinus rnediierraneus whose rcmains arc often found associated to the remains of Molluscs nt the feeding places in estuarine stations. © 1974, Taylor & Francis Group, LLC.