Morphological differences in skulls and feeding apparatuses between Antarctic (Balaenoptera bonaerensis) and common (Balaenoptera acutorostrata) minke whales, and the implication for their feeding ecology

Abstract

The differences in rorqual feeding ecology have been linked to the presence of different morphological markers. The Antarctic minke whale (Balaenoptera bonaerensis Burmeister, 1867) and common minke whale (Balaenoptera acutorostrata Lacépède, 1804) are closely related species, but their morphological differences have not been fully investigated. In this study, we compared 21 skull and 11 feeding apparatuses (baleen and mouth-related parts) measurement points between these two species using hundreds of individuals covering a wide range of body lengths in both sexes. Their engulfment capacities were estimated using these measurements. Our results show that Antarctic minke whales have (1) proportionally larger skulls to the body length, (2) more dorsoventrally and laterally curved rostra, (3) proportionally larger feeding apparatuses to the condylobasal length, and (4) significantly larger engulfment capacity than common minke whales. These differences could indicate that Antarctic minke whales have developed a feeding strategy suitable for feeding on krill, which forms large schools. In contrast, common minke whales have adapted to prey on small pelagic fishes that are agile and form small schools.

Downsized: gray whales using an alternative foraging ground have smaller morphology

“…The smaller morphology of PCFG may also be related to foraging tactics employed on different prey and habitat types. Differences in skull and fluke morphology are associated with differences in habitat, feeding strategies, prey types, and hydrodynamics among baleen whales [77][78][79][80][81]. Gray whales are considered 'slow manoeuvrers' compared to other baleen whales, enabling them to employ flexible foraging tactics on various prey types [77,[82][83][84].…”

Yasunaga et al. (2022) meets the ethics code of Marine Mammal Science, and the journal's decision to publish the paper is correct

“…Importantly, these data and samples are now considered "historical" and must be used to learn more about the biology of whales and contribute to the conservation and management of the whale species involved. Indeed, several studies using these data and samples have been published recently in international journals (Nishimura et al, 2021;Taguchi et al, 2023;Ten et al, 2022;Uchida et al, 2021). Perhaps most importantly, these data and sample sets have also been used to calibrate nonlethal methodologies (e.g., Goto et al, 2020;Inoue et al, 2019).…”