Outbreak of Bird Flu Affects Elephant Seals in California
A significant outbreak of a highly pathogenic strain of bird flu has resulted in the deaths of over two dozen elephant seal pups in California. This has prompted the temporary closure of viewing areas for seals at a well-known park in the Bay Area.
Año Nuevo State Park is home to an elephant seal colony that can swell to around 5,000 seals during the breeding season, which typically lasts from mid-December to March. As of Thursday, researchers reported about 30 seal deaths, most of which were weaned pups, amid the ongoing rise of avian influenza.
Researchers from the University of California at Davis and UC Santa Cruz have ramped up monitoring since the outbreak was detected last week. This marks the first confirmed cases of HPAI H5N1 in marine mammals within the state. The impact of this strain has been notably severe in Argentina, where it caused a staggering 70% mortality rate among pups born during the current breeding season.
Roxanne Beltran, a professor and head of UC Santa Cruz’s northern elephant seal research program at Año Nuevo, expressed her team’s commitment to monitoring the situation, stating that it’s emotionally challenging for everyone involved—students and young scientists alike—who have come to know these seals over time.
Beltran also mentioned that, as of Thursday, the death toll had stabilized at a relatively low level instead of escalating dramatically.
The elephant seal colony at Año Nuevo is one of the most extensively studied populations globally. For over six decades, scientists have been tracking this colony through flipper tagging and observing individual seals for insights into their survival, reproduction, and diving behavior.
Beltran noted that they’ve collected more than 380,000 observations of 55,000 seals, allowing for a deep understanding of what’s typical for the species.
This outbreak is considered “unique” in disease ecology research, as it seems to have been detected at an early stage. Thanks to the thorough documentation of individual seals since their birth, researchers can link infection outcomes to specific animals, thereby gaining a better grasp of the outbreak’s implications.
However, questions remain regarding how the seals contracted the virus and whether its spread will extend beyond California.
“We don’t know how the seals acquired the virus, nor if it was from birds or if those birds could potentially transmit the virus outside the state,” Beltran commented.
There’s also uncertainty surrounding the apparent increased susceptibility of weaned pups to this strain of the virus.
In collaboration with the National Oceanic and Atmospheric Administration fisheries, the California Department of Fish and Wildlife, and the West Coast Marine Mammal Stranding Network, researchers continue to monitor marine mammals along the coast.
Año Nuevo State Park remains open but with restrictions. Seal-viewing tours, essential during the breeding season, have been canceled through the end of March, according to spokesperson Adeline Yee from California State Parks.
“As a precautionary measure, access is momentarily paused to provide wildlife with space and allow ongoing monitoring,” stated a notification on the park’s website.
Typically, the park attracts more than 60,000 visitors annually, but over 400 tours have been canceled, including 1,547 reservations and 4,363 tickets, alongside more than 50 school tours.
