September 29, 2008

Illusive Beak Whales Target Of Sonar Study

Illusive mammals such as the beaked whale are hardly seen, mysterious, and obscure, and yet they have become the focus of new studies due to the harm that military sonar systems seem to cause them.

"There's not much known about these creatures - where they live, their lifestyle," says Ted Cranford from San Diego State University. "In fact, they might be the least understood group of large mammals on Earth."

This summer, the research yacht Song of the Whale, operated by the International Fund for Animal Welfare (Ifaw), is on a mission to acquire more information about the mammals as it sails around the Canary Islands, habitat to numerous beaked whale species.
The yacht's key research tools are called hydrophones. They are underwater microphones that listen to, track and record the whales' high-frequency clicks.

"Some species have never been seen alive, and these are animals as big as an elephant," says a whale biologist, Vassili Papastavrou, who is on board Song of the Whale.

How many beaked whales are currently alive and productive? Unfortunately, we do not know. How many different species of beaked whales are there? Again, the answer is currently unknown.

The 2002 reference work Sea Mammals of the World book names 21.
However, it notes that Arnoux's beaked whale could in fact be the exact same as Baird's, another species of the beaked whale.

The International Union for the Conservation of Nature (IUCN) lists 17 different species in its Red List of Threatened Species. More importantly, the list notes that for 15 of those species, there is simply not enough information about them to identify if they are inclined to extinction or not.
For most beaked whale varieties, a lot more facts have come down by the inspection of dead animals. For many of the rarer species, the cadavers are the only known source of the mammal, since they have never been seen alive.

From a fresh corpse scientists can conclude on the animal's general size, learn about the diet and collect DNA samples for further analysis.
They can also observe how the species have modified to the environment they reside in.

"This kind of work led to the beginning of our understanding of social structures, such as with the sperm whale," says Papastavrou.
"But then, sperm whales are incredibly loud. Beaked whales use such high frequencies that you can't even hear them without specialized equipment."

Last year Ted Cranford had a exceptional opportunity to get a closer view of the illusive whales. A Cuvier's beaked whale washed up in Oregon. The people who discovered it quickly froze the head to scan it. The scan demonstrated that the conventional kind of sound production in other whales was about right for this species.

The sound reception of the whales seems to be very complex, connecting portly bodies that focus the sound created and air sacs that reflect it back.

"Air sacs are perfect acoustic mirrors," says Ted Cranford.
"The whales need to be able to isolate their ears from each other in order to maintain their directional sense, and one of the best ways to do that is through air sacs."

Even though what we currently know about beaked whales is perhaps fascinating it is diminished by our lack of knowledge.

Ifaw thinks that its line of research will address questions about the behavior of the mammals that autopsies cannot answer.


Image Caption: A cuvier's beaked whale breaches east of Italy, in the Ligurian Sea. Photo: Aguilar de Soto, University of La Laguna, Spain, and WHOI


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