Paleoecological significance of coupling metrics of successful and unsuccessful shell-breaking predation: Examples using Neogene bivalve prey

Temporal patterns in successful and unsuccessful shell-breaking predatory attack strategies on Varicorbula in the Plio-Pleistocene of Florida

“…For the present study, bulk samples collected from the uppermost Pliocene to lowest Pleistocene Pinecrest Beds (upper Tamiami Formation (three bulks with 246 individuals), lower Pleistocene Caloosahatchee (one bulk with 698 individuals), middle-upper Pleistocene Bermont (two bulks with 576 individuals), and uppermost Pleistocene Ft. Thompson (three bulks with 322 individuals) formations exposed at three different localities in Florida were used (see Mondal et al, 2014a for details). A previous study by Mondal et al (2014a) has shown that these samples had limited evidence of taphonomic processes. Furthermore, an additional correction has been performed to remove taphonomic overprinting on the frequency of reported shell breaks (see below).…”

“…Although this manner of counting can potentially inflate both the total number of scars/breaks as well as the overall frequency of break/scar on the studied specimens, this approach is helpful in comparing relative proportion of breaks/scars within the three sectors. It should be noted, however, that the focus of this study was not on documentation of the overall repair or successful break frequencies, that information can be found in Mondal et al (2014a).…”

“…However, for the calculation of breaks, we have only used the undrilled shells from the samples as drilled shells represent successful predation by drilling gastropods. Given the likelihood that these individuals were killed by the predators that penetrated the shells, any breaks found on these were considered abiotic in origin and unrelated to the lethal predation-induced breaks examined here (Vermeij, 1982;Stafford and Leighton, 2011;Mondal et al, 2014a). Therefore, these drilled shells were excluded from the shell-break calculations.…”

“…Whereas successful attacks -those which lead to a prey's demise and consumption -leave no evidence of repair, unsuccessful (i.e., non-/sub-lethal) attacks often lead to skeletal damage in various prey types, including molluscs, that may be repaired and then preserved as scars on the shell/skeleton. Quantification of these successful and unsuccessful attacks using various approaches, such as estimated crushing mortality (ECM; Vermeij, 1982;Stafford and Leighton, 2011;Mondal et al, 2014a) and repair frequency (RF; Dietl, 2001, 2003), in tandem, can effectively identify temporal changes in predation pressure (Mondal et al, 2014a). However, as they are typically used individually, these metrics offer relatively limited and often biased insights into aspects of predatory behavior, including site selectivity and magnitude of attacks.…”

“…When successful and unsuccessful predatory attacks are examined together, in contrast to the use of these parameters in isolation, the interpretations are more reliable and meaningful (Mondal et al, 2014a). Furthermore, this methodology can identify potential lethal and non-lethal attack strategies by examining the proportion of breaks and scars preserved on a given prey species, which might be useful to better understand extinct predators and their attack strategies.…”