A case for cannibalism: Confamilial and conspecific predation by naticid gastropods, Cretaceous through Pleistocene of the United States Coastal Plain

Abstract

Cannibalism is a common phenomenon in animals, but some previous authors have concluded that cannibalism by shell-drilling naticid gastropods was caused by predator ineptitude, especially early in the evolution of naticids. The suggestion that naticids were less efficient predators earlier in their history may be considered consistent with the hypothesis of escalation. According to the hypothesis of escalation, biological hazards, such as predation, have increased through geologic time. If naticids were less efficient early in their history, and if cannibalism is an indicator of predator ineptitude, then the incidence of cannibalism should be greatest early in the history of the naticid predator-prey system. Based on this hypothesis, we predicted a temporal decrease in the frequency of cannibalism. We tested this hypothesis by determining the incidence of predation by naticid gastropods on naticid gastropods, including intraspecific cannibalism, from the Cretaceous through the Pleistocene. Drilling frequencies (percent of naticid specimens with complete naticid drillholes) were determined for samples of naticids from twenty-three stratigraphic levels in the U.S. Atlantic and Gulf Coastal Plain (∼3,400 naticid specimens).