With more than 20,000 seals, Piedras Blancas is largest elephant seal rookery on Earth
Scientists know relatively little about the Piedras Blancas Elephant Seal Rookery, the largest mainland northern elephant seal rookery in the world that’s home to more than 20,000 seals. Cal Poly researcher Heather Liwanag wants to change that.
Fresh off a nearly three-month research excursion to Antarctica, where she co-led a team studying Weddell seal pups, Liwanag is heading up a group of three grad students and 18 undergrads that is surveying and marking elephant seal pups five days a week at the beaches near Piedras Blancas.
“No one’s ever really studied this population” outside of basic counting and tagging, Liwanag said.
That’s because the vast majority of research on elephant seal populations was done at Año Nuevo State Park, north of Santa Cruz, Liwanag said. Much of that work was done by UC Santa Cruz’s Daniel Costa, who served on Liwanag’s doctorate committee and who will coordinate with her in her pilot study.
Liwanag said she hopes the study will help researchers better understand how the Piedras Blancas population interacts with rookery populations to the north and the south.
“We’re almost smack in the middle (of the major rookeries),” she said, meaning it will be easier to track the seals’ movements from Piedras Blancas.
She also said she wants to learn what effect geography, the physical landscape of Piedras Blancas, has on the development of elephant seal pups.
The Piedras Blancas rookery is relatively young; it was established in the early 1990s but has seen its population explode.
For a species that was “seriously near extinction,” Liwanag said elephant seals have managed to make a major recovery from their depleted populations of the early 20th century.
“Somehow, they managed to come back,” she said.
After spending December and early January surveying the rookery, Liwanag said her team has begun “stamping” baby seals so that they can more easily track them later on. That process involves hair dye, a 4-foot dowel and a bit of delicate “backwards mirror writing,” she said.
“Surprisingly, it is not the bulls that are aggressive toward us; the bulls are focused on other males and generally do not see our presence as a threat,” Liwanag said.
She said females at this time of year are more aggressive than usual, being protective of their pups.
“We are extremely careful to cause as little disturbance to the animals as possible,” Liwanag said.
That means not getting in between a bull chasing another animal, not marking a seal if it would cause too much disturbance or the mother is alerted to their presence, and generally sticking to marking pups if they are on the outskirts of a group “or relatively isolated from other animals,” she said. “We simply do not mark animals that are in the middle of a bunch of adults.”
Once the pups are weaned, they will begin congregating in “weaner pods,” Liwanag said. That’s when her team will move to insert flipper tags and weigh the pups. Each rookery has its own tag color, and fittingly for its name, the tag for Piedras Blancas is white. She said that work will likely continue until the end of March.
Liwanag cautioned the public that they may see researchers, wearing Cal Poly green jackets, on the beaches of Piedras Blancas.
Federal law prohibits human contact with elephant seals, but Liwanag’s team has been added to Costa’s Marine Mammal Protection Act permit to conduct their research. She said she and her team members welcome questions but urged members of the public to give both researchers and elephant seals a wide berth when they’re on the beaches.
Returning to Antarctica
As for Antarctica, she said she is returning to McMurdo Station next winter to continue her team’s research on Weddell seal pups. Liwanag said her team learned some lessons from the last trip and hopes to make their sample size more robust.
Elephant seals and Weddell seals share something in common; they are two of the deepest diving pinnipeds. Liwanag said she hopes to one day study the diving practices of Weddell seals, Antarctic elephant seals and Piedras Blancas elephant seals.
Anyone wanting to know more about Liwanag’s research can email her at firstname.lastname@example.org.