Tool use involving a different prey type, microhabitat and location, and long-term anvil use, by the graphic tuskfish Choerodon graphicus (De Vis 1885)

Tool use is a remarkable animal behaviour, and the investigation of this phenomenon in fishes is a relatively new and growing field. The graphic tuskfish Choerodon graphicus (De Vis 1885) has previously been documented using anvils but the extent and variability of this tool-use behaviour remains poorly understood. In this study, we investigated whether C. graphicus breaks open crustaceans and/or sea urchins on anvils in different microhabitats and/or locations. We also inspected two previously identified anvils for evidence of long-term anvil use. Three individual C. graphicus were observed breaking open sea urchins on dead coral anvils in a coral rubble microhabitat at Île aux Canards, New Caledonia. They produced visual and auditory cues while carrying out tool-use behaviour and these cues often attracted attendant fishes. Notably, two anvils appeared to have been used by one or more tool-using C. graphicus for years at Îlot Maître, New Caledonia. These findings suggest that tool-use behaviour is both innate and learned and is a prey-handling method of choice used by individuals that learn to specialise in large prey items from a few underutilised hard-shelled prey species. Furthermore, the findings show that specific anvils can be used long-term and also suggest that individual wrasses may carry out tool-use behaviour long-term. The study provides new insights into the feeding ecology and social behaviour of C. graphicus and underscores the need to further investigate the extent and variability of tool use in fishes.