Bird Flu Wiped Out Nearly Half of the Females in the World’s Largest Elephant Seal Population, Drone Images Suggest

Scientists recorded a 47 percent drop in breeding females in South Georgia’s three largest elephant seal colonies after bird flu hit. Scaled to the whole island, that’s a potential loss of more than 50,000 of the animals

Sara Hashemi | Daily Correspondent

November 18, 2025

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In 2023, bird flu reached a remote island in the southern Atlantic Ocean. Now, South Georgia—home to the world’s largest southern elephant seal population—has been transformed.

Drone images of the island’s three biggest seal colonies suggest the population of breeding females has dropped by 47 percent since the introduction of the H5N1 virus in 2023. The findings, which compared the seals’ numbers in 2022 with those in 2024, were published in the journal Communications Biology on November 13.

“It painted a starker picture than I was expecting,” says lead author Connor Bamford, a marine ecologist at the British Antarctic Survey, to Emily Anthes at the New York Times.

The three colonies make up an estimated 16 percent of the island’s elephant seal population. By scaling up the trend seen in those groups, the researchers estimate that about 53,000 females across all of South Georgia might have missed the 2024 breeding season.

“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,” Bamford tells Phoebe Weston at the Guardian. In the long run, the loss will likely have a “dramatic impact on the population,” he adds.

Since H5N1 bird flu was first detected in domestic waterfowl in 1996, the virus has mutated in ways that make it more infectious in wild birds and mammals. It’s now ravaging pinnipeds and other wildlife across the globe.

In 2023, more than 11,000 sea lions, penguins, dolphins and other animals died from bird flu in Chile. In Argentina’s Valdés Peninsula, an estimated 17,400 seal pups—representing nearly 97 percent of the site’s pup population—died from the virus in 2023. Antarctic animals have even suffered from H5N1. During a recent expedition, researchers found evidence of the virus in nine bird and four seal species on the Antarctic Peninsula.

H5N1 may have affected even more animals than researchers have accounted for, experts say.

“While mass mortality events are highly visible, they may not represent the full spectrum of the virus’s effects on pinnipeds,” Elizabeth Ashley, a veterinarian pathologist at the University of California, Davis, who was not involved in the new study, tells Sofia Moutinho at the BBC. “Many pinnipeds are not easy to observe or access, so it is plausible that clustered or sporadic mortalities may have gone undetected in some locations.”

Unfortunately, the South Georgia island population of elephant seals doesn’t seem to have stabilized. “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,” Bamford says to the Guardian. “I wouldn’t say it’s over at all.”

Researchers remain unsure how the virus may affect other mammal and bird species in Antarctica and islands just beyond the continent, like South Georgia, Ed Hutchinson, a virologist at the University of Glasgow who was not involved in the work, says to the outlet. “All we can do is to wait and watch.”

Scientists also don’t know how the huge losses on the island and elsewhere may impact other wildlife. “When you remove such a big mass, you completely upset the balance of the ecosystem,” says Marcela Uhart, a wildlife veterinarian at the University of California, Davis, who has conducted separate avian flu research in South America, to the BBC.

Elephant seals are top ocean predators, and they serve as an important “ocean fertilizer,” Uhart adds, spreading nutrients from their feces as they swim across the water. “No other species can replace elephant seals in the ocean."

Sara Hashemi | Read More

Sara Hashemi is a science writer and fact-checker currently based in New York City. Her work has appeared in Sierra, The Body, Maisonneuve magazine and more.