A hidden population of endangered whales has just been discovered - by nuclear bomb detectors

Pygmy blue whales might be the smallest members of the blue whale family, but at 24 metres long they are still some of the largest creatures in the ocean. Now a previously unknown population of pygmy blue whales has been detected in the Indian Ocean.

The whales’ distinctive singing was first detected by sophisticated underwater microphones (hydrophones), which are used to listen for disturbances in the ocean, such as nuclear bomb detonation.

The hydrophones are used by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) to detect sound waves in the ocean. The CTBTO's job is to monitor possible signs of nuclear testing. But it also makes its recordings available for marine scientists who are eager to hear what else its devices have picked up.

Scientists from Australia’s University of New South Wales (UNSW) were working with CTBTO data when they came across what they described as “an unusually strong signal”.

That signal wasn’t new. It has been part of the Central Equatorial Indian Ocean’s soundscape for almost 20 years, according to UNSW professor Tracey Rogers, a marine ecologist and senior author of the study.

After they analyzed the sound, the researchers concluded it must have been generated by pygmy blue whales. There are four pygmy blue whale populations in the Indian Ocean. This particular singing didn’t sound like any of the known groups, leading the scientists to one unavoidable realization – there was a fifth population out there that hadn’t been previously identified.

“I think it’s pretty cool that the same 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,” Rogers told UNSW Newsroom.

Whales are among some of the most endangered species on the planet. There may be fewer than 400 individual North Atlantic right whales left.

Despite a ban on the international trading of whale products, commercial whaling still occurs in parts of the world, according to the WWF. And there are other hazards. Vessel strikes are a leading cause of North Atlantic right whale mortality, as is getting entangled in fishing gear. Noise levels in the ocean, caused by human activity, may be responsible for increasing the animals’ stress levels.

One of the next steps for the researchers will be to carry out visual sightings of the pygmy whales to confirm what they have learned from the audio data.

That might not be as easy as it sounds, though. “Blue whales in the Southern Hemisphere are difficult to study because they live offshore and don’t jump around,” Rogers said.

In the meantime, the audio data could help the scientists establish how the whales adapted to a warming ocean – and therefore how they might fare as the oceans continue to heat up.

The whales aren’t the only recently discovered animals found south of the equator. In 2017, millions more penguins were found in Antarctica than prior estimates had accounted for.

Past estimates of the total number of Adélie penguins in East Antarctica were based predominantly on counting the number of breeding pairs. The number was thought to be around 2.3 million.

A revised count, with more accurate data on non-breeding birds, put that number at 5.9 million.

Protecting the ocean and everything that lives in it, is one of the United Nations’ Sustainable Development Goals (SDG).

Around 30% of atmospheric CO2 is absorbed by the ocean. The amount of CO2 in the atmosphere has increased since the advent of the industrial revolution. This increases the concentration of CO2 in the ocean, too, which leads to changes in the chemistry of the seawater, such as falling pH levels and increasing acidity.

Fighting pollution and tackling the wider challenges of the climate crisis will help relieve some of these pressures on the ocean, making life there more sustainable.