Decades after being exterminated by Soviet hunters, blue whales are returning to the crystal clear waters of the Seychelles.
Researchers spent a year recording beneath the waves to discover the whales, after filmmakers spotted them in 2021 and discovered they may be breeding in the area.
Blue whales are the largest animal to ever live on Earth; They can grow up to 30 meters long and weigh up to 150 tons. Hunting, once widespread in the Indian Ocean and beyond, resulted in the deaths of more than 340,000 animals in the 20th century.
The species is now classified as endangered by the International Union for the Conservation of Nature.
However, whale numbers are rising following a near-global ban on whaling, and their return to the Seychelles was described as a ‘conservation victory’ by the team, who published their findings in the journal Endangered Species Research.
“It turns out that if you stop killing animals en masse and give them a chance to recover, they can recover,” says Dr. Kate Stafford, one of the lead researchers.
Speaking to the BBC, she added: “We want to know where they come back and knowing there is a population around the Seychelles is incredibly exciting.”
In the first decades of the last century, the populations around the tropical islands were mainly attacked by Soviet whalers on their way to and from Antarctica.
To determine whether the beautiful species had returned to the region, Dr. Stafford and the team spent a month studying the waters and listening to an underwater microphone to detect signals from them.
Unfortunately there were none.
“We heard remarkable things: the thumping of sperm whales from thousands of meters deep and dolphins locating and communicating their echoes, but unfortunately no blue whales,” nature sound recordist Chris Watson told BBC News.
However, the team also installed a sound trap that recorded every 15 minutes for a year. The mass of audio data included the loud and quiet sounds of blue whales, mainly in March and April.
“This means that the Seychelles could be very important for blue whales,” says Dr. Stafford. “They sing during the breeding season and we think it’s probably the males singing, based on what we know about other whales.”
“So there is also potential for the Seychelles as a breeding or nursery area.”
Although the blue whale’s song is naturally the loudest, it is inaudible to humans.
Although they can reach up to 188 decibels, the same volume as a jet engine, the frequency is so low that it is beyond the range of human hearing.
What people can hear are the ‘harmonics’, higher frequency sounds that the whales emit when they sing.
“It’s this very deep, steady heartbeat,” Watson said.
“When I was recording blue whales in Mexico, it was echoing in my headphones.”
From the recordings, the team was even able to identify which population group visited the Seychelles, identifying them as a group normally found in the northern Indian Ocean.
The Seychelles are just one area where blue whales are returning. In recent years they have returned to the waters around South Georgia and in 2021 they were spotted off Spain’s Atlantic coast for the first time in more than 40 years.
Source: Metro
Source: Metro
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