Evidence of sociality and group foraging in Antarctic minke whales (Balaenoptera bonaerensis)

Abstract

Top krill predators such as the Antarctic minke whale (AMW) serve a vital role within the fragile Antarctic sea-ice ecosystem. They are an abundant krill specialist, but their ecological role in the Antarctic remains poorly understood due to their cryptic behavior and remote habitat. It is therefore crucial to develop a baseline understanding of their basic social and foraging ecology. This study uses animal-borne camera tags to quantitatively explore these critical ecological aspects. Twenty-eight tags were deployed on AMW between 2018 and 2019 in Andvord and Paradise Bays around the Western Antarctic Peninsula. Tag data were analyzed with respect to diving, foraging, and social behavior. Results suggest the presence of loose fission-fusion sociality, with individuals forming short-term associations in 60.6% of cases including both foraging and non-foraging contexts. Socializing was significantly more common for larger individuals and resulted in a significant decrease in foraging rates for both shallow (< 30 m) and deep (> 30 m) dives. There were 12 instances of simultaneously tagged individuals that associated with one another in pairs or trios, displaying synchronized spatial movement and diving behavior. These data illustrated the use of group foraging strategies, with high incidence of synchronized foraging dives (67.5% of associated dives) and lunges (64% of associated lunges). Our results provide clear baseline information on AMW sociality and group foraging, which will help direct future studies for more targeted work. This study will improve our ability to understand the relationship between Antarctic species and their environment as climate change continues to alter the ecosystem landscape.