Whales ‘sing’ and talk across oceans
AUTHORS of the study examined humpback whale song recordings from both sides of the African continent — from animals off the coasts of Gabon and Madagascar respectively — and transcribed more than 1,500 individual sounds that were recorded between 2001 and 2005. Song similarity was quantified using statistical methods.
Some song learning can occur between populations that are in close proximity and may be able to hear the other population's song. Over time, the researchers detected shared phrases and themes in both populations, with some years exhibiting more similarities than others.
In the beginning of the study, whale populations in both locations shared five ‘themes.’ One of the shared themes, however, had differences.
Gabon’s version of Theme 1, the researchers found, consisted of a descending ‘cry-woop’, whereas the Madagascar singers split Theme 1 into two parts: a descending cry followed by a separate woop or ‘trumpet.’
Other differences soon emerged over time. By 2003, the song sung by whales in Gabon became more elaborate than their counterparts in Madagascar.
In 2004, both population song types shared the same themes, with the whales in Gabon’s waters singing three additional themes. Interestingly, both whale groups had dropped the same two themes from the previous year’s song types. By 2005, songs being sung on both sides of Africa were largely similar, with individuals in both locations singing songs with the same themes and order. However, there were exceptions, including one whale that revived two discontinued themes from the previous year.
In this instance, the gradual changes and degrees of similarity shared by humpbacks on both sides of Africa was more gradual and subtle.
“Studies such as this one are an important means of understanding connectivity between different whale populations and how they move between different seascapes,” said Dr. Howard Rosenbaum, Director of WCS’ Ocean Giants Program and one of the co-authors of the new paper.
“Insights on how different populations interact with one another and the factors that drive the movements of these animals can lead to more effective plans for conservation.”
Researchers transcribed more than 1,500 individual humpwhale sounds
As part of the study, researchers examined humpback whale song recordings off the coasts of Gabon and Madagascar, respectively, between 2001 and 2005.