ARONOWSKY, A; AGNEW, J. G.; LEIGHTON, L. R.; ANDERSON, L. C.; Louisiana State Univ.; Louisiana State Univ.; San Diego State Univ.; Louisiana State Univ.: Inferring predation intensity on heterochelous decapod crustaceans: simulation studies and the handedness metric.

Decapod crustaceans are well known as major predators in marine ecosystems but less attention is paid to their role as prey. Decapod chelae, as multi-functional appendages, record the influence of both predators and prey. Durophagous crabs have dimorphic chelae (heterochely) that are initially major right claws and minor left claws, however, non-fatal attacks that result in the removal of the right major claw will lead to a reversal in chelae dimorphism upon the next regenerative molt; a phenomenon known as reversed handedness. Since decapod chelae are common in modern and fossil assemblages, evidence of nonlethal injury from frequencies of reversed handedness may provide a proxy for predation intensity on decapods. The proportion of reversed handedness in a decapod population is used as a measure of predation intensity on the decapods. Because reversed handedness is the result of failed attacks, it is analogous to repair scar or incomplete drillholes frequencies commonly found in molluscan studies, and has been used similarly to make inferences about predation intensity on decapods. Here we test the utility of the reversed handedness metric using a probabilistic model that includes the injury rate and kill rate for each molt stage of a population of heterochelous decapods. The model simulates the proportion of reversed handedness observed in death assemblages; values that can subsequently be compared to the actual frequency of predation attempts on the population.