Food Quality and Cannibalism in the Red Land Crab, Gecarcinus lateralis

Nitrogen (N) is a scarce and perhaps limiting nutrient for many herbivores. Herbivore populations that are able to adjust density rapidly in response to changes in ambient N levels would be able to optimize growth, survival, and reproduction during periods when N is more available and to avoid habitat depletion and mass starvation should N availability decline. We report here that the natural plant diet is growth limiting for the red land crab Gecarcinus lateralis (Freminville) on Bermuda, and that supplementation of the diet with high-nutrient food (soybeans) results in markedly reduced cannibalism of adults on conspecific juveniles. This predicts that populations in habitats where food quality is high will have greater survival of recruits than those in nutrient-deficient habitats. Nutritionally modulated cannibalism would allow population size to expand and contract with nutrient availability while minimizing mortality in reproductively active age classes.