Coping with catastrophe: foraging plasticity enables a benthic predator to survive in rapidly degrading coral reefs

Human-induced rapid environmental change (HIREC) disproportionately affects species with specialisttraits and long generation times. By circumventing prolonged evolutionary processes, behaviouralplasticity is critical in allowing species to cope with rapid environmental changes within their lifetimes.Coral reefs have faced multiple mass mortality events of corals related to climate change in the last twodecades. The consequent loss of structural complexity adversely impacts long-lived, structure-dependentfish predators. We attempted to determine how well a guild of groupers (Pisces: Epinephelidae) copeswith rapid structural change in the lightly fished Lakshadweep Archipelago, Indian Ocean. Of the 15species, territorial and site-attached groupers declined exponentially with decreasing structuralcomplexity, while widely ranging species showed no change. However, one site-attached species, thepeacock grouper, Cephalopholis argus, maintained high densities across the structural gradient. Weexplored the mechanisms this species employs to cope with declining habitat structure. Our observationsindicate that both a potential release from specialist competitors and plasticity in foraging behaviour(foraging territory size, diet and foraging mode) appeared to favour the peacock grouper's survival insites of high and low structure. While specialist competitors dropped out of the assemblage, the foragingterritory size of peacock groupers increased exponentially with structural decline, but remained constantand compact (50 m²) above a threshold of structural complexity (corresponding to a canopy height of60 cm). Interestingly, despite significant differences in prey density in sites of high and low structure, gutcontent and stable isotope analyses indicated that peacock groupers maintained a specialized dietaryniche. In-water behavioural observations suggested that diet specialization was maintained by switchingforaging modes from a structure-dependent ‘ambush’ to a structure-independent ‘widely foraging’mode. The remarkable foraging plasticity of species such as the peacock grouper will become increasingly critical in separating winners from losers and may help preserve specialist ecosystem functions ashabitats collapse as a result of climate change.