Similarity yet a range of differences between humpback whale songs recorded in the Philippines, Japan and Hawaii in 2006

摘要

Humpback whale Megaptera novaeangliae songs have been proposed as a means to define stocks or coherent population units, based on the assumption that if individuals sing the same complex, ever-changing song, then they must associate. Songs from the Philippines (Babuyan Islands), Japan (Ogasawara) and Hawaii in 2006 were compared to examine the relationship of these populations as determined by song composition. A total of 13 phrases (including phrase variants) were identified from the sample overall.Philippine and Japan songs were composed of the same 9 phrases, while Hawaii song had these 9 phrases, plus 4 unigue phrases. Common phrases were presented by singers in the same pattern in all 3 regions. Comparison of phrase use and proportion found ahigh correlation between the Philippines and Japan (r = 0.876, p < 0.001), and moderate correlations between Japan and Hawaii (r = 0.583, p = 0.029) and the Philippines and Hawaii (r = 0.570, p = 0.033). With the Japan and Philippines sites 2300 km apartand 6200 and 8400 km from Hawaii, respectively, this suggests a relationship between degree of separation and degree of song difference. The range of differences between songs is consistent with a 2-stage splitting of the migratory stream into separatewinter assemblies where song divergence may occur. Partial similarity of song (versus entirely same or different) suggests some components are more sensitive to change than others. The variable pace of change may complicate use of song as an index of recent association, especially between populations with different social circumstances that presumably govern song change.