Durophagy bias: The effect of shell destruction by crushing predators on drilling frequency

Studies in paleoecology utilizing the record of drilling predation to draw ecological and evolutionary inferences are likely subject to durophagy bias: the inflation of observed drilling frequency due to the removal of undrilled prey via crushing predation. Although this bias was recognized nearly four decades ago, it is commonly ignored in studies of drilling predation. Here we quantify the potential magnitude of this bias and discuss multiple methods—including fragmentation frequency, Vermeij Crushing Analysis, and direct observation—that can be applied to account for its effects in paleoecological studies. Using examples from the literature, we illustrate the application of each of these approaches. The potential magnitude of the durophagy bias increases as a function of observed drilling frequency, suggesting that observations of high drilling frequencies may warrant further examination. In such cases, multiple factors may contribute to increased susceptibility of prey to the durophagy bias (e.g., geographic and temporal distributions of prey, prey shell morphology, habitat, and life mode). Although durophagy bias may not affect every study, it should be a consideration in paleoecological studies on drilling predation, particularly when observed drilling frequencies are high and multiple prey taxa, habitats, geographic regions, or time intervals are being examined.