Contextual drivers of breaching behaviour in the ocellated eagle ray (Aetobatus ocellatus)

Context Breaching behaviour, characterised by the temporary propulsion of an aquatic organism out of the water, is widely observed across taxa, including sharks and rays. Yet, because of its spontaneous and infrequent nature, its triggers and adaptive significance remain largely unresolved. Aims To investigate the contexts preceding breaching behaviour in the ocellated eagle ray (Aetobatus ocellatus) and infer potential functions. Methods We documented breaching events and preceding contexts by using aerial drone observations supplemented by opportunistic citizen-science footage. Key results Fifteen breaches were recorded, each being preceded by a distinct external stimulus, including interactions with associative fish (e.g. remora, family Echeneidae) or predatory encounters (e.g. approaches by great hammerhead sharks, Sphyrna mokarran). In fish-associated cases, rays often exhibited substrate chafing and pectoral-fin curling before breaching, consistent with escalating irritation or hydrodynamic interference; breaching resulted in separation from the associating fish in all but one case. Predator-associated breaches occurred amid rapid evasive swimming manoeuvres. Conclusions Breaching in A. ocellatus is a flexible, context-dependent behaviour that serves multiple adaptive functions related to associate removal and predator avoidance. Implications Drone observations can resolve rare behavioural events, and further standardised reporting of triggers, breach characteristics and outcomes is needed to determine the full range of functions and drivers of breaching.