Dead sea lion pups along California coastal islands alarm researchers

On May 7, Patrick Robinson took a boat to Año Nuevo Island to observe the sea lions that hatch on this rocky outcrop in northern Monterey Bay.

The shoreline was littered with dead babies – babies who appeared to have been delivered too soon and were therefore too weak and small to nurse, or who had died at birth.

Similar sightings have been made further down the coast, on San Miguel Island, in the Channel Islands – where huge colonies of sea lions congregate each year – and as far south as Mexico.

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Robinson, director of UC Santa Cruz’s Año Nuevo Reserve, said it’s not uncommon to see dead puppies this time of year. He explained that sick or malnourished females sometimes stop en route south to abort. But the numbers he saw were alarming. And since the peak of the birthing season is still a few weeks away, this bodes a potentially serious and worrying situation.

Stranding coordinators and biologists up and down the California coast say something is clearly going on, but they still don’t know what.

Testing for avian flu – which has wiped out populations of sea lions and elephant seals in South America – is underway. The same goes for testing for domoic acid, which has poisoned large numbers of sea lions in the past, as well as other common pathogens.

“In a typical year, you can expect to see 5 to 10” dead puppies, said Megan Moriarty, a veterinarian at UC Santa Cruz. “But we have now counted between 250 and 300 dead sea lion pups” on the island of Año Nuevo.

She said sightings included dead or stillborn puppies, aborted fetuses, malnourished puppies and adult females with dystocia – difficult births – who are also thin.

“Unfortunately, many prematurely dying pups have also been reported in the Channel Islands (San Miguel), which is a crucial breeding area for California sea lions,” she said. “The cause and impact of these mortalities remain unknown.”

She and Sharon Melin, a research biologist at the National Oceanic and Atmospheric Administration’s Alaska Fisheries Science Center, said there are many potential reasons for the widespread mortality of sea lion pups, including environmental factors, such as malnutrition, lack of available food linked to El Niño, infectious causes (bacteria, viruses such as leptospirosis, influenza, brucella, coxiella and others) and toxins (such as domoic acid).

And while they both believe testing for avian flu is warranted – given that it is a multi-species global outbreak – “we have not observed neurological or respiratory signs in the Año Nuevo sea lions,” Moriarty said.

“Reproductive failures and stillborn animals are not common in influenza A infections in marine mammals worldwide,” she said.

Melin said about 25,000 puppies are born in the Channel Islands each year.

“In some years, especially El Niño years, or sometimes heatwave years or other oddities that happen in the environment, we will have about 20 to 30 percent premature babies,” she said.

She said puppies born this time of year are often not “fully cooked.”

“They might just stay a little bit longer…and probably if you could put them in an incubator and take care of them, they might survive,” she said.

And when autopsies are performed on these little puppies, “you’ll see that the very last thing to fully develop is their lungs.” …So they’re just not developed enough to breathe on their own and be successful. At this stage, they sometimes live a few days, but cannot breastfeed and do not have the motor skills to hold their head up or suckle effectively.

She added that mothers usually struggle to get their puppies to nurse: “They don’t know what’s going on and they’re trying to figure out why they’re not nursing.” So there’s a lot of interactions that happen there, but usually the puppy ends up dying after a short period of time.

Michael Milstein, a spokesman for the National Oceanic and Atmospheric Administration, said the most recent fisheries survey found “a dramatic decline in anchovy stocks off the southern half of the state, where find most of the strandings.

He said sightings of predators and seabirds were more dispersed, “suggesting they are tracking more dispersed prey.” He said studies further north were not yet complete.

But the high number of brown pelican deaths and significant declines in California’s chinook salmon populations have many people concerned about broader problems in the ecosystem.

This year, fisheries managers decided to ban salmon fishing along the coast and in rivers for the second year in a row, in an effort to help chinook stocks recover.

Stranding coordinators and biologists say the good news is that the California sea lion population is healthy and robust; however, rescue centers fill up with sick and malnourished puppies.