A crisis among California sea lions that has resulted in nearly 1,000 stranded pups and older animals arriving starved and sick on coastal shores has reached the Sonoma Coast, where six animals have been recovered in recent weeks, according to the Marine Mammal Center near Sausalito.
All of them — four pups and two adults — later perished because of their weakened physical state. The strandings included a pup that was brought in late Tuesday and died Wednesday morning, said Laura Sherr, a spokeswoman for the nonprofit rescue facility located in the Marin Headlands.
One of the adult sea lions had also been badly entangled in fishing gear, she said.
The rising death toll — thought to be caused by a band of warm water along the West Coast and the shifting availability of prey for sea lions — sheds some light on the challenges faced by center volunteers and veterinary staff working desperately to ensure that at least some of the recovered animals survive.
“It’s tough,” said Shawn Johnson, director of veterinary science for the rehabilitation facility. It has received more than 336 ailing sea lions since Jan. 1. “Basically, they’re little babies, sea lion babies, and seeing them in such poor condition, they’re heart-wrenching.”
Workers checking in on the sea lions each morning often find animals that didn’t make it through the night, Johnson said. Many sea lions have been euthanized to prevent further suffering, he said.
The overall mortality rate has been about 40 percent, which is not unusual, he said, though with such high numbers, it’s painful nonetheless.
“But it also keeps us going — that we’re going to be able to save a large number of the animals, those that have made it into the center and are getting the best care possible,” he said.
The Marine Mammal Center currently is overseeing care for 168 sea lions, Sherr said.
One sea lion found Jan. 18 on the Mendocino Coast was returned to the ocean last week, Sherr said. It was one of 15 sea lions that have recovered sufficiently to be released back to the wild.
Workers hope many of the sea lions taken in for care four to six weeks ago will be strong enough for release soon, Sherr said.
Another pup found more recently on the Mendocino Coast is under observation, she said.
But experts say it’s unclear where the crisis — already so outside the norm — is headed, with the rate of strandings remaining consistent day-to-day in February and on pace to beat modern records, said Justin Viezbicke, California Stranding Network coordinator for the National Marine Fisheries Service.
About 940 strandings had been reported statewide as of Feb. 18, the majority of them in Southern and Central California, closer to sea lion breeding colonies in the Channel Islands.
There have been reports of stranded sea lions all the way in Oregon, as well as 10 in Crescent City, Johnson said, even though animals so young should not be north of south-central California.
Sea lions, usually born in June, typically spend 11 months with their mothers, about six months nursing and then learning a little at a time to forage for food.
But it appears many mothers are unable to provide enough nourishment to their young, prompting the pups to go off on their own in search of food that they don’t yet have the skills to procure.