Blue whale song is getting deeper
The haunting song of the world's biggest animal, the blue whale, is getting deeper, researchers have discovered.
Underwater recordings of the giant endangered mammals have revealed that the tone of their rhythmic pulses and moans has become steadily lower as their population have slowly recovered after nearly being wiped out by whaling.
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Marine biologists believe the changes offer a new insight into blue whale culture as entire populations alter the tone of their songs as they grow in numbers.
Professor John Hildebrand, a blue whale expert at Scripps Institution of Oceanography at the University of California in San Diego, has used recordings of blue whales since the 1960s to track the changes in their songs.
He found that in 1962 blue whale calls were at a frequency of around 22Hz, well below the range of human hearing, but last year had decreased even further in frequency to around 15Hz.
He said: "This is giving us an insight into the culture of blue whales as they are clearly listening to each other's songs and changing them.
It takes a conscious decision to make the calls deeper, so it is a reflection of what is going on in the population.
"These animals have a finite lung capacity, so their songs are a trade off between frequency and volume.
"They can either make the song really loud or really deep.
"As their numbers have slowly increased after the devastation caused by whaling, they are having to communicate over smaller distances so their songs don't need to be as loud and they can make them deeper."
The findings are the latest to offer a glimpse into the mysterious world of these majestic creatures.
Blue whales, which can grow up to 110 feet in length, are notoriously shy and difficult to study.
Before large-scale hunting, the global blue whale population was thought to have been around 200,000 animals, but numbers fell to just a few hundred by the 1960s when a hunting ban was introduced.
The population has since recovered to around 4,500 animals.
Professor Hildebrand has also discovered that blue whales in different parts of the world use different "dialects" in their songs.
Only the males sing and it is thought they are attempting to attract mates or to communicate to other males during the mating season.
But other researchers believe whale song is a more complicated form of communication than simply trying to attract a female.
Professor David Rothernberg, a musician and philosopher at the New Jersey Institute of Technology, has spent the past three years attempting to communicate with whales through his own musical instruments.
Using hydrophones linked to microphones he has played his clarinet and saxophone to a range of whale species, including the most vocal of all sea mammals the humpback whale.
He claims the whales responded to his music and interacted with him in an underwater "jam" session.
In a new book, Thousand Mile Song, he details his journey to play music with the whales and includes some recordings of the interactions.
He said: "For me, I felt like they could recognise the music I was making and were responding to that.
"There was a very special interaction with a humpback and he seemed to change his song so that by the end it was hard to tell which was the clarinet and which was the whale.
"These are incredibly social animals and they seem to change their songs regularly. When one of them innovates, this gets picked up by the rest of the population and they all start singing in the same way."
Original Source : http://www.telegraph.co.uk/earth/main.jhtml?xml=/earth/2008/06/21/eawhales121.xml
