Federal marine wildlife officials said that a mass stranding of malnourished sea lion pups along the Southern California coast since January has intensified in recent weeks and researchers remain unsure of the cause.
Officials declared an "unusual mortality event" for the California sea lion, a designation that prompts immediate federal response after a significant die-off of a marine mammal population.
The declaration comes as sea lion pups have been found stranded on Southern California beaches -- from Santa Barbara to San Diego -- at rates exponentially higher than in years past.
In Los Angeles, for instance, nearly 400 pups have been stranded since the beginning of the year. Last year, just 36 were reported stranded.