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Solitary humpback whales manufacture bubble-nets as tools to increase prey intake

Szabo, Andy1; Bejder, Lars2; Warick, Hunter3; van Aswegen, Martin2; Friedlaender, Ari4; Goldbogen, Jeremy5; Kendall-Bar, Jessica6; Leunissen, Eva7; Angot, Marie1; Gough, William2

Published Aug 19, 2024 on Dryad. https://doi.org/10.5061/dryad.m0cfxppbj

Data files

Abstract

Several animal species use tools for foraging; however, very few manufacture and/or modify those tools. Humpback whales, which manufacture bubble-net tools while foraging, are among these rare species. Using animal-borne tag and unoccupied aerial system technologies, we examine bubble-nets manufactured by solitary humpback whales (Megaptera novaeangliae) in Southeast Alaska while feeding on krill. We demonstrate that the nets consist of internally- tangential rings and suggest that whales actively control the number of rings in a net, net size and depth, and the horizontal spacing between neighbouring bubbles. We argue that whales regulate these net structural elements to increase per-lunge prey intake by, on average, seven-fold. We measured breath rate and swimming and lunge kinematics to show that the resulting increase in prey density does not increase energetic expenditure. Our results provide a novel insight into how bubble-net tools manufactured by solitary foraging humpback whales act to increase foraging efficiency.