CONTEXT-SENSITIVITY IN CRAB FORAGING STUDIES

Initial work examining crab foraging from optimality premises explored fundamental foraging scope (the capacity of animals to graze), often within an abstract experimental context. An emergent theme involves explicit consideration of biological constraints (e.g., predation risk) and environmental factors (e.g., substrate type) which, by modulating grazing capacity, determine the realized foraging pattern seen in nature. We briefly review two studies that illustrate the contemporary focus on realized foraging pattern. One defines field grow-out techniques for bivalves (raised in mariculture and resource enhancement programs) that minimize losses from predators such as the portunid crab, Ovalipes ocellatus. By focusing on marginal regions of predator: prey interaction (in this case, foraging on low densities of clams planted in heterogenous substrates), the study yielded novel insight into limits on portunid crab foraging on infaunal clams. The second study analyses the foraging performance of a deposit feeding ocypodid crab, Scopimera inflata, over different temporal and spatial scales. We demonstrate that whereas S. inflata performs suboptimally at micro-scales (seconds to minutes; mm to cm), the crabs nearly optimize performance over macro-scales (days to years; cm to m). Continued research on the fundamental foraging scope of crabs is warranted, but should be explicitly referenced to natural historical context and, in particular, to the forager's ontogenetic stage. We also perceive a need for collaborative research incorporating behavioral, physiological, and biochemical facets in an integrated experimental setting. This would ensure that context does not bias information, as can occur in studies that emphasise a particular research perspective, methodological approach, or scale at which foraging is analysed.