Storms imperil elephant seal pups on Bay Area beaches

Ocean surges from early January storms flooded Bay Area beaches at a vulnerable time for elephant seals: the start of pupping season.

Storm waves overtook entire beaches, including critical birthing areas on the Point Reyes National Seashore and at Año Nuevo State Park in San Mateo County. Elephant seals spend most of the year at sea, but pregnant females have begun returning to shore to give birth to pups, who cannot swim for the first month.

“This storm was particularly bad because it happened at arrival time for the females,” said Roxanne Beltran, assistant professor of ecology and evolutionary biology at UC Santa Cruz. “It’s time for them to get naps, give birth. The pups weren’t ready to be battered around.”

Researchers have just begun documenting survival rates. They are also studying whether these anomalous storms provide a window into future threats to seal habitat as sea levels rise, compounding the strength and reach of both high tides and waves, according to Beltran.

Northern elephant seals range from the coastal waters of Alaska and the Aleutian Islands south to Baja California. They come to shore in waves starting in December, and the last adults head back to sea in March. Males head north while females head west to feed in deep open water. The pups stay ashore for several months, teaching themselves to swim. They are off on their first foraging migrations no later than June.

The timing of January storms could have been worse. Sarah Codde, marine ecologist with Point Reyes National Seashore, said although they expect that a high number of existing pups didn’t survive, most of the pregnant females hadn’t yet come to shore after their long journeys feeding at sea.

Last week researchers counted about 430 adult females across the national seashore, compared with 550 at the same time last year. The population peaks at about 1,500 adult females.

Elephant seals on ocean-facing beaches were hemmed in by tall cliffs and had nowhere to retreat. Those ocean sites “just got slammed,” Codde said. They expect to find that no pups survived.

But even in protected Drakes Bay, another elephant seal stronghold, storm waters inundated the inland beaches. The threat of mudslides has kept researchers away from close observation, but they suspect many pups there also died, Codde said.

Codde said they will learn more as the season progresses. One question is whether females delayed coming to shore because of the storm. And they do not yet know whether females observed without pups lost them or are still pregnant.

“The bulk of our females aren’t even here yet,” Codde said. “If the storms were happening right now and into next week, that would be really bad.”

At Año Nuevo State Park, the elephant seal population averages between 2,000 and 4,000 during pupping season but can climb above 5,000 animals, Beltran said. UC Santa Cruz biologists survey elephant seals every day to track behavior, the environment and certain individuals.

Beltran’s colleague, Professor Dan Costa, described his observations Jan. 1 after the less severe New Year’s Eve storm combined with the aftermath of a king tide in late December. Some mother-pup pairs appeared trapped in shallow water at the base of sand embankments, unable to get up and over onto dry ground. One mother barked at her pup as the waves washed over them, unable to climb a small sand berm in their way.

“They were in the wash zone, and the mother and pup were getting knocked around — that’s not good,” Costa said.

The researchers have special state parks permits allowing them to traverse in protected areas to observe and document elephant seal behavior, but they do not intervene.

Much of the 2-mile beach was subsumed with water at points during the storm series. Beaches are now littered with not only trees and vegetation debris but also buoys, buckets, plastic bottles and milk crates.

Researchers have been surprised to find most seals at Año Nuevo State Park were able to move inland, onto dunes or into gullies with their pups, Beltran said. They expect only a small percentage of pups died during early January storms.

“We’re always nervous about how these big climate events will impact the seals,” she said.

More than a century ago, elephant seals were hunted to near extinction for their blubber, which like whale blubber was used to make oil. They were believed to be totally wiped off the planet, but around the turn of the century, about two dozen seals were found on Guadalupe Island off the Mexican coast. Mexico implemented official protections for the species, followed by the United States. The species came back, albeit with far less genetic diversity.

Today the population is estimated to be near 200,000.

The species is built to withstand bad years. Females might live nearly 20 years and give birth to pups every winter. Costa said that if even just two of those survive into adulthood, the population will continue on.

Still, sea level rise puts elephant seals at risk. They depend on mostly narrow island beaches and some mainland beaches to birth their young — areas under threat by rising waters. Their pups need safe beaches for about one month before they learn to swim.

“As sea level rises, what regions of (elephant seal) colonies will go away?” Costa said.