Investigating how leadership and social coordination operate in cetaceans helps us understand their complex social structures and ecological strategies. Using drone-based observations, this study examines potential leadership and social behaviours of three killer whale groups frequenting Hardangerfjord, in Norway. Drone footage was captured between February and April 2025, recording 45 group deep dives and multiple social interactions, which were analysed. Over 80% of these dives were initiated by adult females, while no calves were observed initiating. Statistical modelling revealed that adult females were significantly more likely to initiate dives, supporting the presence of unshared decision-making and suggesting that leadership is age-sex class related. Dive lag data showed a right-skewed distribution, indicating that most group members responded quickly to a single initiator. Group size and behaviour (travelling or resting) did not significantly influence mean dive lags or interindividual dive intervals, suggesting stable group cohesions. Social behaviours, synchronised surfacing and physical contact, were observed most in adult female – calf dyads. These interactions were context-dependent, with minimal interactions observed during foraging. This study demonstrates the leadership role of adult females and recommends including acoustic and tagging approaches in future research to further understand group decision-making and social interactions.
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