Humpback whale song recordings suggest common feeding ground occupation by multiple populations

Elena Schall,Irene T Roca,Olaf Boebel,Karolin Thomisch,Gabriele Gerlach,Sari Mangia Woods,Ilse Van Opzeeland

doi:10.1038/s41598-021-98295-z

Abstract

Humpback whale males are known to sing on their low-latitude breeding grounds, but it is well established that songs are also commonly produced ‘off-season’ on the feeding grounds or during migration. This opens exciting opportunities to investigate migratory aggregations, study humpback whale behavioral plasticity and potentially even assign individual singers to specific breeding grounds. In this study, we analyzed passive acoustic data from 13 recording positions and multiple years (2011–2018) within the Atlantic sector of the Southern Ocean (ASSO). Humpback whale song was detected at nine recording positions in five years. Most songs were recorded in May, austral fall, coinciding with the rapid increase in sea ice concentration at most recording positions. The spatio-temporal pattern in humpback whale singing activity on Southern Ocean feeding grounds is most likely shaped by local prey availability and humpback whale migratory strategies. Furthermore, the comparative analyses of song structures clearly show a differentiation of two song groups, of which one was solely recorded at the western edge of the ASSO and the other song group was recorded throughout the ASSO. This new finding suggests a common feeding ground occupation by multiple humpback whale populations in the ASSO, allowing for cultural and potentially even genetic exchange among populations.

Highlights

Humpback whale males are known to sing on their low-latitude breeding grounds, but it is well established that songs are commonly produced ‘off-season’ on the feeding grounds or during migration
By assessing humpback whale song structure, we explore the comparability of feeding ground song with songs on the breeding grounds, the role of the Atlantic sector of the Southern Ocean (ASSO) as an alternative mating ground, and the potential mixing of multiple breeding populations in the ASSO feeding area
Songs were divided in two categories: the complex song (HWS1; songs organized in at least two different themes), which was found in 1127 h, and the preliminary song (HWS2; vocalization bouts which did not conform to the rule of the complex song category, but still formed at least three repeated phrases of the same phrase type) which was found in 430 h

Summary

Introduction

Humpback whale males are known to sing on their low-latitude breeding grounds, but it is well established that songs are commonly produced ‘off-season’ on the feeding grounds or during migration. This opens exciting opportunities to investigate migratory aggregations, study humpback whale behavioral plasticity and potentially even assign individual singers to specific breeding grounds. One further study collected acoustic data near a humpback whale ‘super-group’ off western South Africa and describes the song that was recorded there[32] These studies showed that the identification and structural analysis of humpback whale song from austral feeding grounds can provide valuable information on humpback whale behavioural ecology and potentially even offer insight into the breeding stock origin of humpback whale males present in the feeding areas

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