Body size data collected non-invasively from drone images indicate a morphologically distinct Chilean blue whale (Balaenoptera musculus) taxon

Ms Leslie,A Apprill,P Chanarat,Jw Durban,G Chiang,Ca Miller,P Bahamonde,Mj Moore,Cm Perkins-Taylor

doi:10.3354/esr01066

Abstract

The blue whaleBalaenoptera musculus(Linnaeus, 1758) was the target of intense commercial whaling in the 20thcentury, and current populations remain drastically below pre-whaling abundances. Reducing uncertainty in subspecific taxonomy would enable targeted conservation strategies for the recovery of unique intraspecific diversity. Currently, there are 2 named blue whale subspecies in the temperate to polar Southern Hemisphere: the Antarctic blue whaleB. m. intermediaand the pygmy blue whaleB. m. brevicauda. These subspecies have distinct morphologies, genetics, and acoustics. In 2019, the Society for Marine Mammalogy’s Committee on Taxonomy agreed that evidence supports a third (and presently unnamed) subspecies of Southern Hemisphere blue whale subspecies, the Chilean blue whale. Whaling data indicate that the Chilean blue whale is intermediate in body length between pygmy and Antarctic blue whales. We collected body size data from blue whales in the Gulfo Corcovado, Chile, during the austral summers of 2015 and 2017 using aerial photogrammetry from a remotely controlled drone to test the hypothesis that the Chilean blue whale is morphologically distinct from other Southern Hemisphere blue whale subspecies. We found the Chilean whale to be morphologically intermediate in both overall body length and relative tail length, thereby joining other diverse data in supporting the Chilean blue whale as a unique subspecific taxon. Additional photogrammetry studies of Antarctic, pygmy, and Chilean blue whales will help examine unique morphological variation within this species of conservation concern. To our knowledge, this is the first non-invasive small drone study to test a hypothesis for systematic biology.

Highlights

Overharvest in the oceans extends up the macroscopic marine food web (Hutchings & Reynolds 2004)Publisher: Inter-Research · www.int-res.comEndang Species Res 43: 291–304, 2020 scale commercial whaling
Industrial whaling began in the early 20th century and officially ended with a 1965−1966 International Whaling Commission ban on the harvest of blue whales, some illegal whaling continued through the 1970s (Branch et al 2004, Clapham & Baker 2018)
Of the Southern Hemisphere subspecies, the Antarctic blue whale B. m. intermedia (Burmeister 1871) is estimated to have been the most impacted by commercial whaling (> 340 000 killed), and their current abundance is estimated to be approximately 1% of the pre-exploitation population size (Branch et al 2004)

Summary

Introduction

Overharvest in the oceans extends up the macroscopic marine food web (Hutchings & Reynolds 2004)Publisher: Inter-Research · www.int-res.comEndang Species Res 43: 291–304, 2020 scale commercial whaling (summarized in Branch et al 2007). The global population of blue whales is listed as Endangered under the IUCN Red List (Cooke 2018). Intermedia (Burmeister 1871) is estimated to have been the most impacted by commercial whaling (> 340 000 killed), and their current abundance is estimated to be approximately 1% of the pre-exploitation population size (Branch et al 2004). This taxon is listed as Critically Endangered by the IUCN (Cooke 2018). The IUCN has not evaluated the pygmy blue whale’s conservation status since 1998 (Pollock 2019), at which time it was listed as Data Deficient (Torres-Florez et al 2014)

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