‘Hugely exciting’: Blue whales returning to South Georgia after near extinction

Before the arrival of industrial whaling to the sub-Antarctic island of South Georgia in the early 20th century, populations of blue whales in the region stretched into the tens of thousands.

Just six decades later - in the 1960s - the whaling stations were forced to close because almost no whales were left, and until now, almost none had returned to this part of the ocean.

But exciting new research led by UK scientists has revealed the return of the critically endangered blue whale to the sub-Antarctic island of South Georgia, 50 years after whaling all but wiped them out.

The discovery is based on analysis of 30 years’ worth of sightings, photographs and underwater sound recordings, and is described as “crucial evidence” in learning how the species is recovering following a ban on commercial whaling in the 1960s, the team said.

Between 1904 and 1971 whalers killed 42,698 blue whales in the region, with most of these killed before the mid-1930s.

The species was almost entirely erased from the region - dedicated whale surveys from ships off South Georgia resulted in just a single blue whale sighting between 1998 and 2018 - but more recent surveys suggest blue whales are making a comeback.

A 2020 survey in February resulted in 58 blue whale sightings, as well as numerous acoustic detections.

Lead author Susannah Calderan of the Scottish Association for Marine Science (SAMS), Oban, told The Independent: “It’s hugely exciting. South Georgia was a major area for industrial whaling at the beginning of the 20th century. And they whaled so hard that though it ended by the 60s, really it was by the mid-30s that they’d taken blue whale numbers down so low that there was really no commercial whaling for blue whales any more.

“It seemed for many decades afterwards that local populations wouldn’t recover, and was seen as an example for how you can exploit a local population so hard that it can’t recover.

“So the fact that we’re starting to see the animals coming back there is hugely encouraging. It’s the start of the recovery rather than an end. As a feeding area South Georgia has remained extremely productive - it hasn’t become any less good as a feeding area.”

She said the record number of sightings only marked the beginning of a recovery for the species which was once thought might never repopulate the area.

“This year we saw 58 and we were absolutely delighted. In an average whaling year, in the 1920s, they killed 3,000 blue whales a year. They took out over 40,000 blue whales, from just South Georgia, so the population is hugely diminished - both the local population in south Georgia and across the wider Antarctic.”

She added: “The last estimate was that they are at 1 per cent of their pre-exploitation numbers.”

“We don’t quite know why it has taken the blue whales so long to come back. It may be that so many of them were killed at South Georgia that there was a loss of cultural memory in the population that the area was a foraging ground, and that it is only now being rediscovered.”

As well as looking for whales, the researchers used listening devices, which can detect the loud, low frequency calls of whales over long distances and can also work in rough weather. The team also had records of whale sightings reported to the South Georgia Museum by mariners and tourist ship passengers, and photographs of blue whales, which enable individual animals to be identified.

There are limited opportunities for dedicated whale surveys in the remote region, known for its harsh weather and inaccessibility, but such surveys are crucial to the future management of South Georgia's seas.

Co-author and whale ecologist Dr Jennifer Jackson of British Antarctic Survey, who led the 2020 whale expedition, said: “This is an exciting discovery and a really positive step forward for conservation of the Antarctic blue whale.

“With South Georgia waters designated as a Marine Protected Area by the government of South Georgia and the South Sandwich Islands, we hope that these increased numbers of blue whales are a sign of things to come and that our research can continue to contribute to effective management of the area.”

The return of the species to the area is also expected to have a positive impact on the environment. Whale excrement also helps support biodiversity and ocean ecosystems through the iron fertilisation cycle, Ms Calderan said.

“Whales fertilise the oceans, and enable the growth of more phytoplankton, which makes more abundant food for the next level up, which is zooplankton - things like krill, which everything eats - so they are very good fertilisers.

“They enable the growth of the whole ecosystem and allow the oceans to become much more productive.”

The study is published in the journal Endangered Species Research.