Female-centred decision making and social interactions in killer whales revealed by drone-based observations

This is the authors' abstract. We don't add key points for this paper.

Understanding how group decisions are made and how individuals coordinate their behaviour is key to interpreting the social dynamics of cetaceans. Using drone-based observations, we quantified leadership during group deep dives and examined two forms of social interactions, synchronized surfacing and physical contact, in killer whales, Orcinus orca , in Hardangerfjord, Norway. Adult females initiated the majority of the dives, significantly more than males or juveniles. This female bias supports the presence of unshared decision making and suggests that leadership is linked to age–sex class. Dive initiators typically occupied peripheral positions but were not necessarily at the front. A right-skewed distribution of dive lags indicates rapid follower responses by group members to a single initiator. Group size and behaviour context (travelling versus resting) did not affect mean dive lags or interindividual dive intervals, suggesting stable group cohesion. Social interactions, in the form of synchronized surfacing and physical contact, were most common in adult female–calf dyads. These interactions were context dependent, rarely occurring during foraging. Despite the limited number of killer whale groups covered, our findings demonstrate the value of drone-based observations for uncovering fine-scale social behaviour and highlight the central role of adult females in structuring collective behaviour and maintaining social bonds in killer whales.