Minimal similarity in songs suggests limited exchange between humpback whales (Megaptera novaeangliae) in the southern Indian Ocean

Abstract

Comparing humpback whale song from different breeding assemblages can reveal similarities in song due to acoustically interacting males, and therefore indirectly test whether males from different breeding sites are mixing. Northern Hemisphere song comparisons illustrated that whales within ocean basins share similar songs and are subpopulations within a larger population, whereas whales in different ocean basins are isolated populations and therefore do not share songs. During the 2006 breeding season, recordings were collected in Madagascar and Western Australia, and were compared visually plus aurally. Both regions shared one theme, whereas each region had four and six private themes, respectively. This study had a substantially low number of shared themes. The co-occurrence of one theme was interpreted as an indication of limited exchange between these breeding assemblages, and we speculate that limited song similarity is due to inter-oceanic interactions. Male(s) from an Indian Ocean breeding group could be exposed to novel song when they geographically overlap, and acoustically interact, with males from a different ocean basin. Novel song could induce rapid temporal changes as new song content is incorporated, thereby minimizing song similarities between that breeding group and other Indian Ocean breeding groups that were not exposed to the novel song.

Humpback whale, <i>Megaptera novaeangliae</i>, song during the breeding season in the Gulf of Tribugá, Colombian Pacific

“…Accordingly, duration was variable across themes in the current study, as has been reported in other populations (Payne et al 1983, Darling and Sousa-Lima 2005, Darling et al 2014. Theme 1 was the dominant, or most frequently sung, theme in the 2013 recordings, consistent with previous descriptions of certain themes or phrases as consistently more frequent in production than others (Mercado et al 2003, Darling and Sousa-Lima 2005, Murray et al 2012.…”

“…However, their structure will likely change in subsequent years as the stability of the song changes (Payne et al 1983). Phrases 1-2 and 3-1 were used consistently throughout each song session, which is consistent with what has been cited as transitional in other studies (e.g., Murray et al 2012). Interestingly, a transitional phrase was never noted between themes 2 and 3.…”

“…Many studies within the song literature compare the song of different populations (Cerchio et al 2001, Darling and Sousa-Lima 2005, Murray et al 2012, Garland et al 2011, 2015. Future studies should seek to expand the current report on Colombia's stock G song via collaborative global comparisons with whale stocks in other locations.…”

“…While the data presented here come from a single breeding season and five individual whales, the re-sighting history and physical description of the study site provided in the methods suggest that each song session analyzed was from a distinct individual, which is critical to the analysis of song structure (Cerchio et al 2001, Murray et al 2012). Continued longitudinal analyses will elucidate the changing nature of the song, which may have been limited during the 2013 season of data collection by occasional weather or fuel-related interruptions to recordings.…”

“…One such behavior is the singing of reproductive male humpback whales (Winn and Winn 1978). Humpback whale song has been documented in many breeding areas (Payne et al 1983, Payne and Payne 1985, Cerchio et al 2001, Darling and Sousa-Lima 2005, Eriksen et al 2005, Murray et al 2012, Oviedo et al 2008. Additionally, song has been recorded during migration (Norris et al 1999, Noad et al 2000 and on a few feeding grounds (Clark and Clapham 2004, Stimpert et al 2012, Garland et al 2013.…”