Bird Flu Outbreak at Año Nuevo State Park
An outbreak of a highly pathogenic strain of avian influenza has resulted in the deaths of more than two dozen elephant seal pups at California’s Año Nuevo State Park. This has prompted the temporary closure of seal-viewing areas at the popular Bay Area park.
Año Nuevo State Park hosts an elephant seal colony numbering approximately 5,000 seals during the breeding season, which extends from mid-December through March. Researchers reported that about 30 seals had died as of Thursday, with nearly all fatalities involving weaned pups amid the rise of avian influenza.
Research and Monitoring Efforts
A team of researchers from the University of California, Davis, and UC Santa Cruz has intensified monitoring since detecting the outbreak last week. This marks the first confirmed cases of the highly pathogenic avian influenza (HPAI) H5N1 strain in marine mammals in California. The same strain previously caused catastrophic effects in Argentina, where it led to a 70% mortality rate among pups born during the 2023 breeding season.
“Our team has been so dedicated working around the clock, over time, whatever it takes to continue monitoring this outbreak,” said Roxanne Beltran, a professor and leader of Beltran’s lab, UC Santa Cruz’s northern elephant seal research program at Año Nuevo. “It’s a really hard, emotional thing to go through as undergraduate, graduate students and young scientists to watch the seals that you’ve gotten to know over the years get sick.”
Beltran noted that as of Thursday, the number of deaths had remained steady and relatively low rather than increasing exponentially.
Long-Term Study of the Elephant Seal Colony
The elephant seal colony at Año Nuevo State Park is among the most intensively studied in the world. Scientists have monitored the colony for over six decades through flipper tagging and long-term tracking of individual seals’ survival, reproduction, and diving behavior.
“We’ve gathered more than 380,000 observations of 55,000 seals, so we know an extraordinary amount about what’s typical for those seals,” Beltran explained.
She described the outbreak as “unique” in disease ecology research because the team appears to have detected it at a very early stage. Due to the extensive documentation of the population, with individual seals identified and tracked since birth, researchers can correlate infection outcomes with specific animals and better understand the outbreak’s consequences.
Uncertainties and Ongoing Investigations
It remains unclear how the seals contracted the virus or whether the infection will spread beyond California.
“We don’t yet know where the seals got the virus, and we don’t know if, for example, they got it from birds, if the birds move in a way that could transmit the virus outside of California,” Beltran said.
Additionally, it is uncertain why weaned pups appear more susceptible to contracting this strain of avian influenza.
Researchers are collaborating with NOAA Fisheries, the California Department of Fish and Wildlife, and the West Coast Marine Mammal Stranding Network to monitor marine mammals along the coast.
Park Access and Tour Cancellations
Año Nuevo State Park remains open with restrictions, according to its official website. Seal-viewing tours, which are mandatory during the seals’ breeding season, have been cancelled through the end of March. This information was provided by Adeline Yee, a spokesperson for California State Parks.
“Out of an abundance of caution, access is being paused to give wildlife space and allow for ongoing monitoring,” reads a notification on the state park’s website.
The park attracts more than 60,000 visitors annually.
More than 400 tours have been cancelled, affecting 1,547 reservations and 4,363 tickets. Over 50 school tours were also cancelled as a result of the outbreak.
