Humpback whale song presence in the Atlantic sector of the Southern Ocean

Humpback whale song most likely fulfills a multi-purpose role in the humpback whale mating system including both inter- and intrasexual interactions. Humpback whale males produce most of their songs on the low-latitude breeding grounds, but evidences increase, showing that songs are also 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) to investigate humpback whale song in a Southern Ocean feeding area comparing song presence, structure and complexity over spatial and temporal scales. Humpback whale song was detected at nine recording positions within the Atlantic sector of the Southern Ocean (ASSO) in five years. Most songs were recorded in May coinciding with the rapid increase in sea ice concentration at most recording positions. The spatio-temporal pattern in humpback whale singing activity on a Southern Ocean feeding ground is most likely shaped by the 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 spatial extent of the ASSO. This new finding suggests a common feeding ground occupation in the ASSO by multiple humpback whale populations, providing important baseline information for ecosystem and stock management.