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Ecologists Discover Presence of The Nearly Extinct Pygmy Blue Whales in The Indian Ocean

by Sushree Mohanty

Ecologists Discover Presence of The Nearly Extinct Pygmy Blue Whales in The Indian Ocean

June 10, 2021

Blue whales, the majestic marine mammals, are the largest animals known to have existed in the world. Yes! They're even bigger than dinosaurs. You can easily spot dolphins hopping out of the water, but it's rare to witness a whale. If you do manage to see one, it would probably be a humpback or a sperm whale. Blue whales are rare beauties!

"We've found a whole new group of pygmy blue whales right in the middle of the Indian Ocean. And I think it's pretty cool that the system that keeps the world safe from nuclear bombs allows us to find new whale populations, which long-term can help us study the health of the marine environment,"

- Tracey Rogers, UNSW Professor and marine ecologist.
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A pygmy blue whale (Balaenoptera musculus brevicauda) breaks the surface in the waters 250 miles west of Maputo, Mozambique.

Discovering Rare Beauties

Blue whales are scarce. They lead a remarkable solitary underwater life and cover a significant area of the ocean waters. Though whaling is illegal in some countries, it’s estimated that approximately 0.10 per cent of blue whales survived whaling in the Southern Hemisphere.

Scientists led by The University of New South Wales (UNSW) Sydney are confident that they have discovered a new population of endangered blue whales in the Indian Ocean. This finding was possible with the help of recordings from hydrophones or nuclear bomb detectors that were supposed to detect bomb tests under the ocean. They have discovered pygmy blue, the smallest subspecies of blue whales.

Pygmy blue whales are known to be tropical subspecies of the blue whale family that are a little smaller but not for any human. Their average size can reach up to 24 meters long, almost the length of two buses. They are also approximately half of the overall weight of a blue whale found in the Antarctic.

However, they wish to seek visual sightings to confirm the new population of whales in the Indian Ocean. If the results are favorable, the world will house the fifth population: pygmy blue whales discovered so far.

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Pygmy Blue Wale's average size can reach up to 24 meters long, almost the length of two buses.

How were they discovered?

Sound travels several times faster underwater than in the air, so many aquatic creatures communicate by producing sounds. Blue whales are often known to be melodious underwater creatures. They sing or just make a noise to communicate, seduce their opposite partners, locate food or just find each other. 

The credit of being the loudest animal in the world goes to the blue whale. Yes! It’s true. Vocalizations of a blue whale can be up to 188 decibels that can be heard from 160 Kms away. This principle helped the scientists of UNSW as the blue whales’ powerful sound wave, or singing, was recorded by underwater bomb detectors.

The UNSW team of scientists was studying the data when they came across an unusually robust signal. Curious about the frequency composition until they discovered that it belonged to a group of pygmy whales. The recordings made by the bomb detectors have led the world to welcome the new population of blue whales that were on the verge of extinction.

The Discovery of these whales was made possible because of the data provided by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO). While monitoring the international nuclear bomb testing, they use advanced hydrophones to detect soundwaves or any suspicious noise from potential atomic bomb tests. These ocean sounds are then tested, analyzed and are helpful in marine science research.

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The Discovery of these whales was made possible because of the data provided by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO).

"Discovering a new population is the first step to protecting it," says Dr. Leroy.

A great bio-acoustician, Dr Emmanuelle Leroy, is the lead author of the study. She was the former postdoctoral researcher at UNSW Science. She has led her whole life studying how animals create and receive sounds. She was examining the CTBTO data when she noticed a peculiar pattern emerging in the bomb detector recordings.

She first noticed horizontal lines on the spectrogram at particular frequencies reflecting a solid signal. Curious about the signal that was not so random, they knew the ocean had something more to offer. She with her team scanned approximately 18 years of data. While analyzing the pattern, they found the signal wasn’t just a random occurrence under the ocean.

Blue whales are hauntingly melodious and powerful singers. Their songs or usual whale vocalization, as scientists estimate, can travel anywhere up to 500 kilometers. Their songs are very low in frequency and are like fingerprints for humans to track. 

Further Studies and Research

In a previous study, Dr Leroy found that the changing pitch in the sound waves produced by the blue whales could reflect their response to the noise of cracking icebergs.

Prof. Tracey Rogers is leading a team of scientists using the CTBTO data. The focus is to study the Chagos population, where they came, where they were born, and how they adapted to the warm ocean temperature.

The team of scientists named the newly-found blue whale population “Chagos,” after the Chagos archipelago where they were located. The scientists are confident with their findings. However, it’s impossible to confirm the existence of these majestic species without visual data or observation. 

This is a significant finding for marine ecologists as these rare beauties were on the edge of extinction after extensive whaling. The acoustic information hidden in the sound waves of the new population of blue whales can also help scientists discover more about the Animal Kingdom. We could learn about their migration patterns, aging mysteries, spatial distribution on the Earth, and population numbers.

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