Into the Deep with Elephant Seals (updated)

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If you’re a resident of the Bay Area, chances are you’ve walked or biked across the Golden Gate Bridge, attended a San Francisco Giants game, marveled at the towering redwoods in Muir Woods, or savored a glass of Pinot Noir from the legendary vineyards of Napa or Sonoma.

But there’s another riveting attraction – coming up soon – that’s also a unique part of our Bay Area bucket list: the return every year of thousands of massive northern elephant seals to the beaches of Año Nuevo State Reserve, a jagged stretch of coastline 60 miles south of San Francisco.

Northern elephant seals on the beach at Año Nuevo State Reserve on the San Mateo Coast. Photo by Amy Miller for KQED Science
Northern elephant seals on the beach at Año Nuevo on the San Mateo Coast. Photo by Amy Miller 

Fifty thousand tourists from around the world flock to this state park every winter to see these one-of-a-kind marine mammals during their breeding season, which lasts from December through March.

Elephant seals are the largest seals in the world. Males can weigh up to 4,500 pounds – more than a mid-size car – and measure 16 feet from snout to tail flipper.

State parks docents take visitors on a two-and-a-half-hour, three-and-a-half-mile-long hike along sandy dunes and coastal brush to view the seals mate, give birth to jet-black pups and catch the occasional bloody fight between massive males competing for breeding territory.


But to see the action, reservations ahead of time are a must, and can be had by purchasing tickets through the California State Parks web site. The fee is $7 per adult for the guided walks, which take place until March 20. Children ages three and under get in for free.

Marine biologists also descend on Año Nuevo year after year to study the returning elephant seals, making it a critical site for the study of this remarkable, resilient animal that was nearly hunted to extinction for its oily blubber a hundred years ago.

“Elephant seals are really animal Olympians,” said Dan Costa, a professor of biology at UC Santa Cruz.  “They’re diving routinely between 1,500 and 2,000 feet of water, and occasionally, they’ll dive for almost two hours.”

A student in Dan Costa's lab at UC Santa Cruz prepares to remove a satellite tag from a female elephant seal. Photo by Amy Miller for KQED Science
A student in Dan Costa's lab at UC Santa Cruz prepares to remove a satellite tag from a female elephant seal. Photo by Amy Miller

Costa has spent four decades studying elephant seals. He and his students have placed high-tech satellite tags and other instruments on more than 500 elephant seals at Año Nuevo to track the location and foraging strategies of the animals, which spend most of their lives at sea.

The sandy laboratory of Año Nuevo continues to offer new discoveries.

Caroline Casey is a biology graduate student at UC Santa Cruz who studies the dominance hierarchy of male elephant seals at Año Nuevo.  Recently, she found that the bellowing calls made by male seals are unique and differ in acoustic features such as frequency, tempo and duration.

“Each call distinguishes one male from another male, like an acoustic fingerprint,” she said.

Using professional-grade microphones, Casey recorded thousands of interactions between male seals at Año Nuevo.

She then placed a speaker near a male elephant seal lying on the beach and played back a recording of another male seal.  If the male on the beach had previously fought with the male and won, it moved toward the speaker, ready for another fight. If it had lost the previous encounter, it scampered away.

“They’re trying to defend females from other males, which is energetically demanding, so they have this system of calling to each other to avoid conflict most of the time,” Casey said.

Still, when they do fight, the encounters can be bloody, and serve as a visible reminder of just how wild much of the California coastline still is.

This video was originally produced and updated by Sheraz Sadiq. The original video can be found here