Assessing intra-individual consistency in humpback whale song production using animal-borne acoustic recorders

Abstract

Studying individual variation in vocal behavior can provide insight into its functions, stability, and mechanisms. Collecting such data at the scale of the individual can be facilitated using animal-borne tags. Here, we use archival suction-cup acoustic recording tags to investigate intra-individual variation in male humpback whale song production. Humpback whale song is a complex and hierarchically structured vocal sequence of 4-7 repeated phrases that are comprised of different units. Repeated songs are termed song sessions. To investigate how consistent song production is within the song session of an individual whale, we deployed suction cup-attached acoustic recording tags on humpback whales in the Hawaiian Islands Humpback Whale National Marine Sanctuary during the 2018–2022 breeding seasons. We analyzed tag data from nine whales to assess intra-individual variation in song structure and syntax as well as differences in the acoustic properties of song units across each song iteration. Each tag contained between 4 and 24 song iterations, and song session recordings varied between 45 minutes and 5 hours. Across individuals, the most variable song iterations occurred at the beginning of a song session. All individuals showed variation in syntax and unit production throughout a session; however, some singers were more consistent than others.