Among the many creatures of the oceans and seas, whales are perhaps the most fascinating. They are huge and have a language of their own, which, as it turns out, is much more complex than previously thought by scientists. The sounds produced by the life underwater were being researched for a long time, and what the researchers recorded last year puzzled them until finally they could trace it to a species of baleen whales. Here is more about the mysterious metallic sound that came from the Mariana Trench.

Between the fall of 2014 and the spring of 2015 scientists have recorded a mysterious sound like a metallic twang, 3.5 seconds long, in Mariana Trench, Pacific Ocean east of Guam. Nicknamed the Western Pacific Biotwang, the scientists believe that the call could belong to a minke whale.

The call was recorded using autonomous seafaring robots known as passive acoustic ocean gliders which can dive up to 3,800 feet and are used by scientists to collect acoustic data from the whales. After much speculation, the researchers published in the Journal of the Acoustical Society of America that they suspect a minke whale to be the source of the sound. Minke whales are the second smallest of the 15 species of baleen whales which can grow up to 10.7 m (female) and 9.8 m (male) in length and weigh 10 tons maximum.

The span of the recorded frequencies was as low as 38 hertz and as high as 8,000 hertz, while human hearing range is between 20 and 20,000 hertz.

The scientists were unable to attribute the frequencies to any anthropogenic sounds such as those from ships or seismic airguns or geophysical sounds produced by earthquakes, ice, wind or rain. This led them to hypothesize that they had a biological source and more specifically a whale.

The recording is a five part call with different sounds ranging from metallic to biological and is a new type of baleen whale call that was never heard before. The low-frequency moaning part that could be heard in it is typical of baleen whales. 

According to Sharon Nieukirk, the sound is very distinct and its the twang-y sound that makes it very unique. The complex nature of the call, the frequencies and the metallic sounds, has led the researchers to believe that it is similar to calls produced by a dwarf minke whales in the northeast coast of Australia, which actually sound like sound effects from Star Wars movies and “boings”.

This isn’t the first time the scientists were after strange noises from the whales. In 2014, they discovered that Antarctic minke whales were responsible for a mysterious duck-like sound, “bio-duck”, that they have been recording since 1960 in the Southern Ocean.

What’s mysterious is that unlike mating calls that only occur during breeding season this call was heard throughout the year. Scientists believe that it could mean the call could have a more complex function than being a mating call.

The distribution of minke whales is unknown at low latitudes as they don’t spend much time at the water surface and they often live in areas where high seas make sighting difficult. Though their blows are inconspicuous, they call frequently, which makes them perfect for studying acoustics. If more can be found through these studies and the calls are translated, then it would be a better alternative to the controversial practice of scientific whaling in Japan.
[source: livescience]