The devastating impact of avian influenza has led to the decimation of half the breeding elephant seal population on South Georgia, a recent study reveals, highlighting potentially dire consequences for the species’ survival.

This isolated island, located in the South Atlantic Ocean, hosts the largest congregation of southern elephant seals worldwide. Researchers have estimated that approximately 53,000 female seals perished following a bird flu outbreak in 2023.

The findings indicate a staggering 47% decrease in the population, a figure that took many by surprise. “The number was quite shocking,” commented Connor Bamford, the lead researcher from the British Antarctic Survey in Cambridge. “I never expected the reduction to be this substantial.”

In 2024, cruise ship travelers reported that access to the famed grave of explorer Ernest Shackleton was obstructed due to deceased seals. However, Bamford noted that numerous carcasses likely went unnoticed, as the animals often returned to the ocean when ill, seeking cooler waters.

Additionally, the direct fatalities from bird flu may have been worsened by the stress experienced by female seals, potentially leading them to abandon their young.

“We were aware there was a high level of mortality – way above normal levels – but it wasn’t until we got this before-and-after comparison that we could see how extensive it was,” said Bamford. In the long term, he said, it would have a “dramatic impact on the population”.

The island in the South Atlantic is home to 54% of the global breeding population of elephant seals. The team used aerial imagery from three beaches to compare the breeding population from 2022 relative to 2024, according to the paper, published in the journal Communications Biology.

There was a particularly high level of mortality among pups, and females take three to eight years to start breeding.

“One of my colleagues is down there on a ship at the moment, and this year the count is lower than it was last year. That suggests the virus is circulating in the population,” said Bamford. “I wouldn’t say it’s over at all.”

Research suggests bird flu is continuing to spread across bird and mammal species in the Antarctic.

“The apparent loss of nearly half the breeding female population has serious implications for … the future stability of the population,” researchers said in the paper. “These findings highlight the urgent need for continued, intensive monitoring.”

The current, highly pathogenic H5N1 strain of bird flu was initially detected in Europe, before spreading across the Americas. It reached South Georgia in 2023, but its impact took time to calculate because the islands are so remote.

“The results of this study are heartbreaking,” said Prof Ed Hutchinson, a virologist at the University of Glasgow, who was not involved in the study.

“It is unclear how severe the impact of this virus will be on the other mammal and bird species in the Antarctic and sub-Antarctic,” he said. “All we can do is to wait and watch.

“H5N1 has already had devastating impacts on ecosystems across the world, from seabird colonies in the UK to sea lions in South America. We will soon find out what it will mean for the Antarctic.”

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