Whales ‘sing’ and talk across oceans

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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.

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