‘Demonic’ Sea Lions Return as Mysterious Toxin Spreads Along California Coast

Something strange is unfolding along the California coast, where sick sea lions are washing ashore by the dozens, doing the unthinkable: seizing, twitching and behaving so erratically that wildlife officials are warning beachgoers to keep their distance.

More than 100 cases of domoic acid poisoning have already been reported in California sea lions this year, according to the Daily Mail, surpassing the 70 to 90 cases typically seen annually. The latest surge has been concentrated around the Monterey Peninsula and Central California coast, including Monterey and Santa Cruz counties.

And it’s the same neurotoxin connected to the bizarre sea lion behavior and attacks that made headlines in 2025 — behavior that was described at the time as “demonic.”

This year, however, officials have not reported attacks by poisoned sea lions on beachgoers.

The culprit isn’t some mysterious new pathogen. It’s domoic acid, a potent neurotoxin produced during certain harmful algal blooms. Small fish such as sardines and anchovies consume the toxin before sea lions eat them. Once ingested, the toxin can wreak havoc on the animals’ neurological systems, affecting memory and behavior and potentially triggering seizures, confusion, heart failure and death.

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Michael Milstein, a spokesperson for the National Oceanic and Atmospheric Administration, described it to the Daily Mail as a “very insidious and brutal disease.”

Perhaps even more troubling to experts is the timing of the latest surge.

Marine Mammal Center spokesperson Giancarlo Rulli told SFGATE that cases first emerged earlier this summer, then subsided and suddenly climbed again as August came to a close.

“The fact that we are about to turn the page on August into September,” while these flare-ups continue to disappear and return, “is a real concern,” Rulli said.

The Daily Mail reported that unusually warm Pacific waters associated with El Niño could be one factor. Combined with nutrient-rich water brought toward the surface through coastal upwelling, conditions can encourage rapid growth of toxin-producing algae such as Pseudo-nitzschia.

For beachgoers, the warning is simple: Don’t get close.

The Marine Mammal Center urges people to stay at least 150 feet from stranded sea lions, noting that sick wildlife can be especially unpredictable.

“All wildlife can be unpredictable, but sick animals are particularly stressed and disoriented,” the organization said.

The center’s dispatch operation can receive more than 350 calls on its busiest days, according to the Daily Mail.

But the danger doesn’t stop with marine mammals.

Humans can also suffer domoic acid poisoning, primarily by consuming contaminated seafood. The condition, known as amnesic shellfish poisoning, can result from eating contaminated mussels, clams, oysters, scallops and certain other seafood. Cooking or freezing contaminated food does not eliminate the toxin, according to the Daily Mail.

That doesn’t mean people are “catching” the illness from sea lions. Simply touching an animal doesn’t transmit domoic acid, and a sea lion bite isn’t a typical route of toxin exposure.

The Marine Mammal Center says the toxin will eventually leave an animal’s system, but repeated exposure can bring more severe and lasting consequences.

For now, California’s coastline is presenting an unsettling picture: wildlife neurologically altered by a toxin moving through the food chain, an outbreak behaving in ways experts say are increasingly unpredictable and more than 100 affected animals already reported this year.

What is happening beneath the waters of the Pacific is now coming to light for everyone to see.

Abby Trivett is a writer and editor for Charisma Media and has a passion for sharing the gospel through the written word. She holds two degrees from Regent University, a B.A. in Communication with a concentration in Journalism and a Master of Arts in Journalism. She is the author of the newly released book, The Power of Suddenly: Discover How God Can Change Everything in a Moment. For interviews and media inquiries, please contact media@.