Humpback whale song variations in La Reunion Island from 2016 to 2018 and in Madagascar in 2018

Male Megaptera novaeangliae produce complex and structured songs which are shared at the population level. Song patterns are culturally transmitted and evolve progressively through time, both over the breeding season and among years. The songs also undergo periods of relatively rapid change, termed “revolutions.” Acoustic monitoring was conducted from 2016 to 2018 in Reunion and throughout 2018 in Madagascar to assess spatiotemporal variation in song structures and population connectivity. A total of 46 high-quality song samples were selected, representing 2,760 min of recordings in Reunion. In Madagascar, 12 samples representing 240 min of recordings were analyzed. Analysis of songs revealed 11 phrases and their variants. Low levels of temporal variations were observed over the breeding season. Songs recorded in June were very similar to those recorded in September. Greater variation was observed between years, and some phrases identified in 2018 may have evolved from phrases recorded in 2017. More variants were described for each phrase type in 2018 compared to 2016. All themes recorded in Reunion were shared with Madagascar, suggesting a high degree of population connectivity during the breeding season.