SUBTLE CHANGES IN MATURE PREDATOR-PREY SYSTEMS - AN EXAMPLE FROM NEOGENE TURRITELLA (GASTROPODA)

Although predator-prey escalation has been well documented in mollusca n ecological systems, relatively little is known about what occurs aft er these systems have escalated. In order to assess potential changes in already-escalated systems, we examined bulk samples of Turritella s hells collected from Neogene strata of the Atlantic and Gulf Coastal P lain, U.S.A. In particular, toe examined the intensity, efficiency, an d stereotypy of naticid and muricid predation on Turritella as a means of discerning subtle changes in predatory behavior. As in previous st udies, we observe little change in the intensity and efficiency of nat icid and muricid predation on Turritella during the Neogene. Unlike pr evious studies, we note significant changes in prey size during this i nterval. Perhaps more significant is that these changes are associated with concomitant changes in predatory drilling behavior as expressed in drillhole-site selectivity and prey-size selectivity. Together, the se findings suggest that escalation was still occurring in this Neogen e system, with predators likely making behavioral changes in order to keep pace with morphologic changes occurring within prey populations.