THE mystery surrounding the songs of humpback whales (Megaptera novaeangliae) has gotten deeper thanks to findings from researchers in the USA, Madagascar and Western Australia.
Published in the January 2012 edition of Marine Mammal Science, the study by Murray et al is the first to document whales within the same ocean basin singing almost completely different songs.
“This is an exception to what is usually found when comparing song from breeding sites within the same ocean during a breeding season,” says researcher Anita Murray, currently at University of Queensland’s Cetacean Ecology and Acoustics Laboratory.
“Males from breeding sites within the same ocean basin usually sing the same song—meaning they sing the same themes in the same thematic order.”
In fact, the whales monitored off the coasts of Madagascar and off Perth, Exmouth and Pender Bay only had one theme in common out of 11 recorded.
“Our study indicates the cultural transmission of song between whales from different breeding assemblages is not as clear as once believed,” says Ms Murray.
She speculates the difference in song could be due to interactions between breeding grounds in Madagascar and Gabon, noting 2003 research that found the whales sharing the same song despite being in different basins.
A similar outcome was found in Australian waters in 2000 when Western Australian song replaced eastern Australian song over a two-year span.
Ms Murray believes some geographical overlap occurs in which members 0f separate basins interact. Unlike in the Northern Hemisphere, there are no land masses to block this type of mixing in the Southern Hemisphere.
Different whale assemblages could come into contact with one another during migration to Antarctic feeding grounds, or during the feeding season itself.
“This study is just the tip of the iceberg in terms of what we have left to discover about the complicated and dynamic cultural transmission of song in the Southern Hemisphere,” says Ms Murray.
Unravelling this mystery will be a challenge, involving studying song comparisons from Gabon, Madagascar, WA and eastern Australia over multiple years to understand the patterns and directions of transmission.
Of course, knowing how songs are transmitted still doesn’t answer the mystery of whale song itself.
Humpback whale song is a male acoustic display used on winter breeding grounds, migration routes and summer feeding grounds.