Meeting Abstract
The global distribution of dwarf minke whales (Balaenoptera acutorostra subspecies) is poorly understood, but it appears they tend to occupy low latitude waters off the coasts of Brazil, South Africa, and Australia, and occasionally in the South Indian Ocean. In March 2019, we encountered dwarf minke whales (n = 5) along the South Shetland Islands (SSI), identified post-encounter through unoccupied aerial system (UAS) photogrammetry and resulting morphological and phenotypical comparison between Antarctic minke whales around the Western Antarctic Peninsula (WAP) (n = 40). The only published study documenting dwarf minke whales along the WAP and SSI includes 11 sightings from 2007-2010, suggesting they are rare and only recently encountered in this region. One possible explanation for the paucity of sightings in this region is a southward range expansion concurrent with regional warming and ecosystem forcing that has facilitated southward range expansions of other sub-Antarctic species. This hypothesis is supported by ongoing changes in the distribution and abundance of myctophid fishes, an important prey item of dwarf minke whales. Alternatively, they may have always been present along the WAP and SSI, but have been misidentified as Antarctic minke whales, as these two species are difficult to distinguish from one another, especially from boat-based surveys. UAS photogrammetry provides opportunity to view these animals in high-resolution to distinguish subtle differences in morphology and phenotype. This study quantifies phenotypic differences between dwarf and Antarctic minke whales, and compares them to other Southern Hemisphere populations, setting a foundation to effectively test these two competing hypotheses related to southward range expansions or historic misidentification.
