Arabian Sea humpbacks' singing put to test
An isolated population of Arabian Sea humpback whales may be less sophisticated "singers" than humpbacks elsewhere.
The whales' calls could be a simplified version of humpback song, scientists' preliminary findings suggest.
Arabian Sea humpbacks (Megaptera novaeangliae) are believed to have been isolated from other whale populations for around 60,000 years.
The humpback subpopulation has been filmed for BBC Two's Wild Arabia.
Arabian Sea humpback whales are genetically distinct and behave differently to other humpbacks.
The subpopulation comprises the only humpbacks not to migrate, instead remaining in a part of the Northern Indian ocean, off the coast of Oman.
The research team's initial findings "[beg] the question as to whether the evolution of song in the Arabian Sea population did not progress to the apparently more complex song of other populations," said Robert Baldwin, scientist at the Environment Society of Oman's Whale and Dolphin Research Group.
"What's fascinating about this is that it fits with the understanding we have about the isolation of these whales."
Researchers used hydrophones (underwater microphones) to record the whales' songs and compare them with recordings from other humpback populations, such as neighbouring whales in the Southern Indian Ocean.
They found that Arabian Sea humpbacks produced phrases, formed of sequences of notes, "which they then might be joining into regular and repeatable patterns", explained Mr Baldwin.
"This would be like song, except that everywhere else in the world, song is composed of themes, which are repeated phrases."
Mr Baldwin and colleagues are uncertain as to why the whales' song may be more simple, but speculate that it could be a result of their isolation from other populations and their small numbers, meaning the whales could be exposed to less variation in song.
The team will analyse more recordings to verify the theory.Mysterious song
Humpback whales' singing has attracted scientific interest for years, but still little is known about its function.
It is thought only males perform the mysterious songs, and that all the males in a population vocalise the same song.
These songs continually evolve over time, and differ between populations.
With only around 100 Arabian Sea humpback whales in existence, the subpopulation is listed as "Endangered" by the International Union for Conservation of Nature.
Through genetic analysis, Mr Baldwin and his team "discovered" the genetically distinct Arabian Sea humpback population in 2007, after several years of study. Previously, it had been assumed that whales near Oman had simply strayed from their usual waters.
Wild Arabia, a BBC / Animal Planet co-production, airs on BBC Two on Friday 1 March at 21:00 GMT.