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Atomic guard on the trail of the whales

2021-06-19T19:19:54.057Z

Through a network of eavesdropping sensors that actually track down nuclear weapon tests, researchers have discovered previously unknown blue whales. But the analysis of the chants harbors uncertainties.



Enlarge image

Minke blue whale in the Indian Ocean: "Difficult to research because they live far off the coast"

Photo: Franco Banfi / Nature Picture Library / imago images

Actually, the CTBTO doesn't really exist yet.

It is true that there is already a seat in Vienna for the "Organization of the Treaty on the Comprehensive Ban on Nuclear Tests".

But because not all states have formally confirmed a corresponding treaty, the status of the organization is still pending.

Nevertheless, the CTBTO - or rather the Preparatory Commission - is already doing valuable work. It manages a whole network of measuring stations that are supposed to monitor whether somebody is not tinkering with nuclear programs somewhere in the world. For this purpose, data from seismometers, infrasound and partly also radionuclide sensors have been evaluated regularly since 1996.

These data are also of interest to naturalists, as we now see. In a study, scientists evaluated the sounds that had been recorded from the sea since 2002. A team led by Emmanuelle Leroy from the University of New South Wales in Sydney found evidence of previously unknown populations of blue whales through whale songs. The study, published in the journal »Scientific Reports«, shows how little is known about the heaviest known animals in the history of the earth - and that, despite their size, they are not easy to observe.

The scientists have now discovered another population of a somewhat smaller subspecies, the minke blue whale (Balaenoptera musculus brevicauda).

They do not quite reach the length of around 30 meters of normal blue whales, but they are still well over 20 meters long and occur in the Indian Ocean and the southern Pacific.

Few groups were known there.

The researchers tracked down the animals through their characteristic chants, which were repeatedly recorded by six detectors at different locations.

The chants of the now identified group could be traced back over about 20 years.

From the point of view of the scientists, this suggests that this is a fixed group

acts who have lived together for a long time.

It is possibly the fifth animal population ever discovered in the Indian Ocean.

Meeting point Chagos Archipelago

"I think it's pretty cool that the same system that protects the world from atomic bombs allows us to find new whale populations," says Tracey Rogers, one of the scientists involved.

In the long term, the data could help to better study the marine environment.

The region around the Chagos Archipelago seems to be particularly popular with minke blue whales.

The archipelago is hundreds of kilometers south of Sri Lanka in the middle of the open sea.

According to observations by the scientists, several groups met here.

This leads them to the assumption that the animals split up the marine regions on their migrations and that the archipelago, basically in the central ocean, overlaps the territories.

However, the study cannot make any statements about how large the newly discovered group of animals is.

In addition, it is controversial whether the evaluation of whale songs can actually serve to distinguish individual whale species.

Some scientists note that the recorded data could also be from Omura whales.

The species was first described around 20 years ago.

Only genetic analyzes or more precise observations would bring clarity.

But they are not easy to obtain.

“Blue whales are difficult to study in the southern hemisphere because they live far offshore and don't jump around like humpback whales,” says Rogers.

For the time being, the researchers will therefore have no choice but to prick up their ears and continue to listen to the animals very carefully.

joe

Source: spiegel

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