Multi-species co-operative hunting behaviour in a remote Indian Ocean reef system

Inter-specific hunting associations can occur across a range of marine species to facilitate prey capture through co-operative behaviour. Here we describe multiple transient cross-phyla associations between day octopus (Octopus cyanea) and three fish species, including peacock grouper (Cephalopholis argus), brown-marbled grouper (Epinephelus fuscoguttatus), and gold-saddle goatfish (Parupeneus cyclostomus), in the isolated reef system of the Chagos archipelago. Observations of such hunting associations are rare, and no similar observations have been recorded for this region. The remoteness of this study site may provide some explanation for these multiple sightings, allowing natural behaviours to occur undisturbed. However, given no previous sightings of such behaviour, the limitation of available food resources following two recent mass coral mortality episodes, may have necessitated the formation of these rare/novel hunting interactions. Intensified prey scarcity and increasingly degraded habitat structure following more frequent disturbance events may therefore lead to such indirect environmentally mediated behavioural responses becoming increasingly prevalent in reef-dwelling species.