Bird flu kills seals and sea lions in the Southern Hemisphere

For the past year and a half, Americans have watched and worried as H5N1 bird flu has decimated dairy herds and killed hundreds of millions of commercially raised chickens, turkeys and ducks.

But much less known is that the virus has devastated wildlife around the world, killing millions of wild birds and mammals.

Few animals in the Southern Hemisphere have been hit harder than elephant seals, sea lions and fur seals. In some places, thousands of dead bodies and orphaned puppies have washed ashore.

On Thursday, a research team led by Connor Bamford, a marine ecologist with the British Antarctic Survey, reported a 47% decline in breeding females between 2022 and 2024 in three large elephant seals on South Georgia Island.

Elephant seals in one of South Georgia’s largest colonies have been infected with bird flu.

(British Antarctic Survey)

The elephant seals of South Georgia Island, located in the South Atlantic between South America and Antarctica, are the largest colony of the species on the planet.

Bamford said the virus was there in 2023 and the researchers were there to see it. But it was their visit in 2024 that really drove the destruction home.

“Normally there are about 6,000 seals in St. Andrews Bay,” he said. He said, describing a two-mile strip of beach on the northeast side of the island. Usually it is difficult to make your way through the animals, it is very crowded.

But in 2024, “it was easy. There were big gaps. There were very few of them,” he said.

Other major breeding colonies, including off the coast of Argentina, have also been affected, as well as several other islands north of the Antarctic Circle. By 2023, researchers at UC Davis reported that nearly 97% of elephant seals had died in Argentina’s Peninsular Forest, the most deaths ever recorded for the species.

According to Ralph Winstrels, a marine ecologist with UC Davis who researches animals in Argentina, two-thirds of southern elephant seal colonies are now infected. Only those near New Zealand and Australia have been spared.

“We’re just holding our breath,” he said, hoping the virus doesn’t get there.

Winstrels said genetic analyzes show the strain of the virus spreading in Argentina has acquired a mutation that allows it to pass more easily between mammals. He said it is not yet clear whether the virus that has spread to other elephant seals and pinnipeds in the region has similar mutations.

Nor does anyone know whether the virus will move north to populations along the California coast — or to people.

But it remains a deadly wake.

Reports of mass die-offs of southern sea lions, fur seals and kibber seals have come in from across the region.

Wanstrels and Bamford say there is no way to know the full extent of the virus in these animals. Many of these species, such as crabeater seals, are so remote that there are few, if any human observers to witness the destruction.

Between 2022 and 2024, more than 30,000 sea lions died in Peru and Chile. In Argentina, approximately 1,300 sea lions and fur seals died.

A researcher launches a drone over South Georgia Island, home to the world’s largest southern elephant seal population.

(British Antarctic Survey)

Winstrels said researchers still don’t have a clear idea of ​​why northern elephant seals and marine mammals in the North Pacific, including those that breed off the coast of California, have survived.

He said that pressure along the Pacific coast of North America is not driving the changes seen in South America, so it might be. There may also be differences in population density or local marine ecosystems.

“We think the South American sea lion played a major role in the transmission, carrying the virus along the coast and perhaps introducing it to the elephant seal population,” he said. “Maybe the areas where the northern elephant seal lives don’t have a good vector for spreading the infection.”

Bamford and Winstrels say that the loss of many of these animals will likely affect the wider ecosystem as well.

For example, elephant seal placentas are a major food source for a variety of coastal animals such as birds and crabs. In addition, seals deep sea food brings nutrients to the surface of the ocean, where fish, kelp, shrimp and other marine life depend on their waste and refuse for sustenance.

“You take away half of their population, that’s going to have an impact,” Winstrall said.