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

Abstract

Cooperative foraging, a mutualistic resource acquisition behaviour observed across diverse taxa, can drive social network structure, as it typically involves high rates of interactions between individuals. Understanding the mechanisms and distribution of such behaviours is important to elucidate the drivers of social organisation. Bubble net feeding ( bubble netting) is a specialised foraging technique practised by certain humpback whale (Megaptera novaeangliae) populations globally. Over 20 years of study in the northern Canadian Pacific, we observed the diffusion of two morphs of this behaviour: social cooperative and independent, or solo, bubble netting. Network-based diffusion analyses - a tool developed to test for social learning - find strong evidence for the social learning of bubble netting when a static social network is used, even after accounting for individual-level traits such as site fidelity and sex (10.6 x103 to 35.4x103 times more support for social versus asocial learning; p < 0.0001). However, we could not completely exclude homophily due to the inherent sociality of this cooperative foraging behaviour. Nonetheless, it is clear that the rapid diffusion of bubble netting throughout this population has significant consequences for its social structure, which should be information considered by those planning the conservation of this threatened population.