It is well established that male humpback whales are accomplished singers. Their songs, thought to be part of a breeding display in which high frequency sounds are emitted to attract females and low frequency sounds are directed towards competing males, are made up of a range of effects, including moans, cries and whoops. Research led by the Wildlife Conservation Society has now added to the playlist.
The study looked at the songs of two humpback whale populations, based on sound recordings collected from 2001 to 2005. One pod was based in the South Atlantic, off the coast of Gabon, and the other in the Indian Ocean near Madagascar. Analysis of the recordings revealed that the two groups picked up musical ideas from each other and incorporated the borrowed phrases and themes into their latest song. This suggests that males from the two pods came into contact with each other over the five years and shared songs, although different levels of song similarity suggests that this happened more in some years than in others.
To uncover this musical collaboration researchers recorded and transcribed more than 1,500 individual sounds and identified patterns, or ‘song units’. They found that the units were composed into larger phrases, which were then repeated to form ‘themes’. These themes were sung for hours at a time, or even days. In the early years of the study the whales shared five themes although one of these developed slightly differently on either side of the continent. Dubbed ‘theme one’, the researchers realised that the Gabon whales favoured a simpler pattern. By 2005, both populations were singing largely the same songs, although the researchers noted that there were exceptions, including one whale that revived two discontinued themes from the previous year.
The findings add a new dimension to accepted wisdom. Previously, it was thought harder for humpback whales to share songs in the southern hemisphere due to greater physical obstacles. If it did happen an entire song was often transferred from one population to another – known as a ‘revolution’. With the Gabon and Madagascar pods however, a more gradual, subtle sharing of songs appears to have taken place.
‘This similarity in the songs supports the genetic data, which shows that these two populations come into closer contact than other southern hemisphere populations,’ explains Dr Melinda Rekdahl, lead author of the study. As well as being an interesting phenomenon, she explains that songs can help answer wider questions related to conservation. ‘Songs provide an opportunity to look at connectivity patterns over yearly timescales as they evolve so quickly and male humpback whales appear to readily learn new songs if they have the opportunity.’
This was published in the March 2019 edition of Geographical magazine
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