Use and prevalence of novel bubble-net foraging strategy in Western Antarctic humpback whales

Abstract

The innovation of new foraging strategies allows species to optimize their foraging in response to changing conditions. Humpback whales provide a good study species for this concept, as they utilize multiple novel foraging tactics across populations in diverse environments. Bubble-net feeding (BNF), commonly seen in the Northern Hemisphere, has emerged as a foraging innovation in the past 20 yr within the Western Antarctic Peninsula. Using sightings data from 2015-2023, we found that BNF was present in every study year, with an annual average of 30% of foraging sightings. This data was supplemented with 26 animal-born tags deployed over the same study period. Of these tags, 12 detected instances of BNF, with BNF making up an average of 19% of the foraging lunges detected. There were seasonal trends in BNF sightings, as it was observed significantly more often at the beginning of the feeding season (January) before declining. BNF group sizes (mean: 3.41) were significantly larger than non-BNF surface feeding groups (mean: 2.21). This observation is consistent with BNF in the Northern Hemisphere, which also appears to primarily be a group foraging strategy. The seasonal pattern and relatively recent emergence of BNF suggests that its use is likely tied to specific environmental conditions, which should be investigated by comparing BNF with variables such as prey density and light availability. The social transmission of novel foraging strategies across other populations further suggests that the prevalence of this strategy likely occurs through social learning.