Cause of Southern California Sea Lion Pup Strandings to Be Investigated

Scientists believe pups aren't getting the food they need due to "environmental factors"

With nearly 1,100 sea lions found ill and stranded on Southern California beaches this year, rehabilitation facilities are full, and newly sick marine mammals must be treated on the sand, a federal scientist said Thursday.

The stranding epidemic — mostly affecting sea lion pups born last year — began in January and has not ceased since, said Sarah Wilkin of the National Oceanic and Atmospheric Administration on a conference call with reporters Thursday.

The pups, which are part of a broader "robust and healthy" sea lion population in California, are being found underweight, suffering from starvation and dehydration, she said.

"You can see bones through their skin," Wilkin said.

Wilkin, who is the coordinator for NOAA's stranding program in California, said an initial hypothesis is that the high number of sick young sea lions is due to "environmental factors that would limit prey availability for the pups."

Pups are being likely disproportionately affected because they're not as experienced in foraging for alternate prey, and they can't swim as deep or as far as older animals, Wilkin said.

Last week, after a review of the evidence by an international scientific panel, NOAA declared the stranding epidemic an "unusual mortality event." The title comes even though most of the animals stranded are still alive when found, Wilkin noted.

About 20 to 30 percent of those sea lions that have entered facilities have died – a figure that's fairly low for wildlife rehab work, Wilkin said.

With the "unusual mortality event" designation, NOAA is forming a team of scientists to investigate the causes of the illnesses. In addition to looking at prey-related causes, researchers will also consider infectious diseases, parasites, and toxins and pollution in the water as causes of the strandings.


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The 1,100 figure is for sea lion standings from Santa Barbara County south to San Diego County, she said.

In Northern California, 83 strandings have been reported. The numbers correspond to animals that have entered rehab facilities, she said.

Those figures will likely go down as facilities are unable to accept new sea lions, she said.

Those pups being found going forwarded will be triaged at the beach, sometimes being moved away from the public, and left under observation, Wilkin said. Lifeguards began helping out last month.

Rescuers will try to find rehab spots for the worst cases, she said.

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