Over 250 dead sea lion cubs found on California’s Año Nuevo Island

More than 250 dead California sea lion pups have been observed on Año Nuevo Island, a small island off the coast of Northern California between San Francisco and Santa Cruz.

Patrick W. Robinson, director of the Año Nuevo Reserve, said in an email to USA TODAY Thursday that he first “observed an unusual increase in the number of aborted California sea lion fetuses on Año Nuevo Island approximately two weeks ago.”

About 50 dead sea lion pups were observed on May 7, with the number rising to 288 on May 14, according to an aerial survey, said Robinson, who is also a lecturer at UC Santa Cruz.

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On May 16, UC Santa Cruz campus veterinarian Megan Moriarty and a local stranded marine mammal network, along with the California Department of Fish and Wildlife, performed necropsies on several stillborn juveniles, but “no apparent cause of death” could be determined, Robinson said.

“This is definitely an unusual event, but we don’t know the cause yet,” Robinson said, adding that other researchers working in the Channel Islands and Mexico have made similar observations, so it’s a larger event than one local event.

Puppies born in mid-May typically “don’t survive”: Robinson

Robinson said Año Nuevo Island is “on the edge of the sea lions’ breeding range” and is a relatively new colony compared to the large colonies in the Channel Islands in Southern California. The species’ peak birthing season is mid-June, Robinson said, and pups born in mid-May “typically don’t survive.”