The New York Times: Racing to Save California’s Elephant Seals From Bird Flu

Published by The New York Times: June 3, 2025

In late 2023, bird flu arrived on the rocky shores of the Valdés Peninsula in Argentina, ripping through the local colony of southern elephant seals. More than 17,000 seal pups died. It could take decades for the population to recover, experts announced in April.

“It really hit a whole generation on that colony pretty hard,” said Sarah Codde, a marine ecologist at the U.S. National Park Service.

Now, a team of ecologists, epidemiologists and veterinarians is scrambling to keep the same thing from happening to northern elephant seals. The seals, which live along the Pacific Coast of North America, were hunted almost to extinction in the 19th century. Since then, they have staged a remarkable comeback.

But the animals face several serious threats, including coastal erosion, extreme weather and warming temperatures. And their low genetic diversity makes them especially vulnerable to an outbreak. “The concern is that any disease could wipe them out,” Ms. Codde said.

Today, the Point Reyes National Seashore in California is home to roughly 4,000 of the marine behemoths. During the breeding season, the beaches become bona fide petri dishes, bringing large numbers of susceptible seals into close contact with one other as well as shorebirds that could be harboring the bird flu virus, known as H5N1.

While Ms. Codde monitors the population at large, the Marine Mammal Center is keeping a close eye on individual seals that are sick. The center’s main hospital, in Sausalito, rescues and rehabilitates sick and injured seals, sea lions and sea otters; last year, it treated more than 1,000 animals.

“We get a sample size out of the ocean. But those things show up to us for a reason, right? They’re an unhealthy sample.”

“Our clinic is a little thimble,” said Dr. Dominic Travis, a wildlife veterinary epidemiologist and the chief programs officer at the Marine Mammal Center. “We get a sample size out of the ocean. But those things show up to us for a reason, right? They’re an unhealthy sample.”

During the breeding season, the center sees a lot of underweight, malnourished elephant seal pups, many of which are still too young to fend for themselves or even swim. Sometimes, they also see elephant seals with parasites or traumatic injuries, such as dog bites or blunt force trauma from boat propellers.

For the last few years, the Marine Mammal Center has been testing any patients with bird-flu-like symptoms, which include respiratory and neurological problems, for the virus.

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