The diffusion of cooperative and solo bubble net feeding in Canadian Pacific humpback whales

Animal culture, in which information and behaviours are acquired and shared through social networks by social learning, is a form of biodiversity with intrinsic and practical value. Cooperative foraging, a mutualistic resource acquisition behaviour observed across diverse taxa, is strongly connected to social networks via behavioural states, cues, and often social learning, as it typically involves high interaction rates. Understanding the distribution, diffusion and learning mechanisms of such cooperative behaviours is an important but understudied aspect of nonhuman culture. Bubble net feeding (‘bubble netting’) is a specialised foraging technique practised by certain humpback whale (Megaptera novaeangliae) populations globally. Over 20 years in the northern Canadian Pacific, we observed the diffusion of two forms: social cooperative and independent, or ‘solo’, bubble netting. Network-based diffusion analysis – a tool to test for social learning – finds strong evidence for social learning of bubble netting when the overall social network is used, even after accounting for traits such as site fidelity and sex (10.6 x 103 to 35.4 x 103 times more support for social versus asocial learning; p < 0.0001). A homophily check using pre-acquisition association data returned ambiguous results, likely due to the inherent sociality of this cooperative foraging behaviour. Nonetheless, the rapid diffusion of bubble netting is clearly important for population viability and should inform conservation planning for this threatened population.