Hundreds of Sick, Dying Sea Lion Pups Are Washing Up on California’s Shores

Dr. Andrew Trites has been studying marine mammals in the North Pacific for 30 years, and he’s never seen anything like what’s happening in California.
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More than 1,450 baby sea lions have washed up on California beaches this year, a huge number that’s been putting animal rescue centers in a frenzy.  The phenomenon has been reported widely, but was particularly magnified in a Thursday New York Times story that delved into specifics about the animals’ plight.

“Many are sick with pneumonia, their throaty barks muted to rasping coughs,” the story, written by Times correspondent Jack Healy, reads.  “Parasites have swarmed their digestive systems. Some are so tired that they cannot scamper away when rescuers approach them with nets and towels and heft them into large pet carriers.”

Why is this happening?  The Times story cites a rapidly changing environment driven by “unusually warm waters,” which are driving away food sources for sea lion moms. Because the moms can’t find food, they’re either abandoning the pups, or not getting back to them in time to feed them.

Trites, for the most part, agrees with that assessment.

“When you get warm ocean surface waters that replace cool nutrient rich waters, animals do starve,” said Trites, the director of the Marine Mammal Unit at the University of British Columbia’s Fisheries Centre.  That’s because the fish sea lions like to eat — anchovies and sardines, to name a few — tend to prefer cool, nutrient-rich water.  If the surface waters are warm, the anchovies swim deeper, making it harder for sea lions to dive and find them.

“Unfortunately, the young animals pay the price,” Trites said.  “If the food is short, mothers can prove enough to keep themselves going, but can’t eat enough to produce the extra energy to make milk.”

It is certainly true that sea surface temperatures have been on the rise in the last hundred years.  In fact, more than 90 percent of human-caused warming goes into the oceans, while only 2 percent goes into the atmosphere. ...

The rising sea surface temperatures themselves aren’t the only side effect of human-caused climate change that could be contributing to these unusual sea lion strandings. Increased extreme weather events driven by a weaker jet stream could also be increasing the likelihood of warm ocean waters, Trites said.  That’s because during storms, wind drags on the ocean surface, pulling together and concentrating large bodies of warm water together.

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