The influence of dolphin group coordination on cooperative foraging with humans

Social foraging is a collective solution to the challenge of catching prey. A remarkable example involving different predator species with complementary hunting skills is Lahille's bottlenose dolphins, <i>Tursiops truncatus gephyreus</i> foraging with net-casting human fishers to catch migratory mullet, <i>Mugil liza</i>. It remains unknown, however, to what extent dolphins coordinate their own actions when foraging with humans, and how intraspecific coordination impacts interspecific foraging success. Using drone-based tracking, we quantified dolphin group surfacing behaviors (diving synchrony, proximity, and heading angles between individuals) and tested the repeatability of these behavioral metrics across independent human-dolphin cooperative foraging interactions. We then quantified how the variance and consistency in these behaviors influenced the likelihood of fishers catching mullet. We found repeatable patterns in dolphin group proximity and heading angles across cooperative foraging interactions with fishers, and that fishers were more successful at catching mullet when dolphins approached them along different trajectories with consistent diving synchrony. These findings suggest that groups of dolphins can be, to some extent, coordinated when fishing with humans, thereby influencing the collective outcome of this cooperative foraging tactic. We consider hypotheses for the underlying mechanisms of synchrony and coordination within groups of dolphins and highlight solutions for overcoming the inherent challenges associated with quantifying collective foraging dynamics in natural settings.