SYDNEY, July 8 (Xinhua) — Australian marine scientists believe they have discovered a new population of rare whales by dissecting their signature songs using underwater bomb detectors.

Researchers led by scientists from the University of New South Wales (UNSW) used high-tech underwater microphones to record the communications of elusive mammals.

“We discovered a whole new group of pygmy blue whales right in the middle of the Indian Ocean,” UNSW Professor Tracey Rogers said in a statement released on Thursday. “We don’t know how many whales there are in this group, but we suspect there are many from the sheer volume of calls we hear.”

Rogers said the species was only “dwarf” compared to other members of the blue whale family, which can grow to about 24 meters in length.

The discovery, published in Scientific Reports, was based on audio data collected by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), a group that monitors international waters for nuclear bomb tests.

Rogers said analysis of these recordings yielded a surprisingly powerful sound, a unique whale song.

After studying the structure, frequency and tempo of the song, the researchers realized that it belonged to a group of previously undiscovered pygmy blue whales.

Rogers said that if visual sightings confirm this new population, they will be the fifth population of pygmy blue whales known to inhabit the Indian Ocean.

“Without these audio recordings, we would have had no idea there was such a huge population of blue whales in the equatorial Indian Ocean,” she said.

Bioacoustician Dr Emmanuelle Leroy of UNSW said the team scanned 18 years of CTBTO data to understand that “thousands of these songs are created every year” and “form a major part of the ocean’s acoustic soundscape”.

“The songs couldn’t come from a pair of whales — they had to come from the whole population,” Leroy said.

Leroy compared the acoustic characteristics of the songs to other types of blue whale songs known in the region, but the evidence pointed to an entirely new population, which they named “Chagas” after the archipelago they discovered nearby.

“We suspect that Chagos song whales move across the Indian Ocean at different times,” Rogers said.

“We found them not only in the central Indian Ocean, but also as far north as the coast of Sri Lanka and as far east as the Kimberley coast in northern Western Australia.”

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