The Southern Ocean Exchange: porous boundaries between humpback whale breeding populations in southern polar waters

Milton Cézar Calzavara Marcondes ,A Boyle,Ted Cheeseman ,Leonardo Liberali Wedekin ,Fábio G Daura‐Jorge ,Annette Bombosch ,Ari S Friedlaender ,Jennifer A Jackson ,Daniel M Palacios ,Оksana Savenko ,M Fátima Araújo ,Marilia Olio ,Roberto C Fortes ,Joana Santos ,Kristin Rasmussen ,Amy S Kennedy ,Logan Pallin ,Isabel Cristina Ávila ,Christopher W Clark ,Manuela Bassoi ,V Beaver ,Judith Denkinger ,Júlio Cardoso ,Renata S Sousa‐Lima

doi:10.1038/s41598-021-02612-5

Abstract

Humpback whales (Megaptera novaeangliae) are a cosmopolitan species and perform long annual migrations between low-latitude breeding areas and high-latitude feeding areas. Their breeding populations appear to be spatially and genetically segregated due to long-term, maternally inherited fidelity to natal breeding areas. In the Southern Hemisphere, some humpback whale breeding populations mix in Southern Ocean waters in summer, but very little movement between Pacific and Atlantic waters has been identified to date, suggesting these waters constituted an oceanic boundary between genetically distinct populations. Here, we present new evidence of summer co-occurrence in the West Antarctic Peninsula feeding area of two recovering humpback whale breeding populations from the Atlantic (Brazil) and Pacific (Central and South America). As humpback whale populations recover, observations like this point to the need to revise our perceptions of boundaries between stocks, particularly on high latitude feeding grounds. We suggest that this “Southern Ocean Exchange” may become more frequent as populations recover from commercial whaling and climate change modifies environmental dynamics and humpback whale prey availability.

Highlights

Humpback whale migration patterns and breeding stocks
The breeding area of humpback whales from the breeding stock ‘G’ (BSG) is situated in the tropical and subtropical waters along the Pacific coast of Central and South America from where they seasonally migrate to the Western Antarctic Peninsula (WAP) to feed 2,3,19,20
We present evidence from fourteen individuals from Brazil (BSA, n = 12) and Pacific Central and South America (BSG, n = 2) matched to putative feeding areas (Table 1, Figs. 1, 2) of BSG (Fig. 1c, showed in a shade of orange) and breeding stock ‘A’ (BSA) (Fig. 1c showed in a shade of green)

Summary

Introduction

Humpback whale migration patterns and breeding stocks. Humpback whales (Megaptera novaeangliae) are a cosmopolitan species[1] which can migrate up to 8500 km between seasonal breeding and feeding. The breeding area of humpback whales from the breeding stock ‘G’ (BSG) is situated in the tropical and subtropical waters along the Pacific coast of Central and South America from where they seasonally migrate to the Western Antarctic Peninsula (WAP) to feed 2,3,19,20. Some individuals from this population do not reach the Antarctic and instead feed around the Fueguian Archipelago of Southern Chile[21]. The feeding area for BSA extends west, at least to Shag Rocks (42o W; Fig. 1c) 240 km west of South Georgia[31], and has been suggested to extend as far east as 10–20° W 28, where stocks from West Africa (BSB) and BSA are believed to co-occur in space and time during summer feeding[32]

Methods

Results

Conclusion