It’s as if a school bell rang and called the young seals back to the beach. In the case of elephant seals, the juveniles return in September and October for four to six weeks of play and rest, the fall haul-out.
That’s the simple description of what’s going on: Seals haul themselves out onto the sand, and there they stay. They arrive one by one, drawn back to the beach, vacated by the adult bulls who were here for the summer. The last few bulls will leave soon.
The herd gradually increases until thousands are on the beach during October. Then those that arrived earliest begin returning to the sea. One by one, they slip into the surf, until only a few are left when the bulls start arriving in late November for the breeding season.
The adult bulls are off to their northern feeding grounds, along the continental shelf off Alaska. They will bulk up for the next few months, arriving in prime shape for the breeding season.
The juvenile seals range from their first year to 6 years old. The ones born in the 2016 season, last January and February, are called the young of the year when they return from their first migration. They left the beach in March and April. Without any leader to guide them, they swam away from the only home they knew.
Those that make it back, about half of them, hunted enough fish and squid to survive. They’re small, but they’ve overcome their first migration. They may not be much bigger than the 200 pounds or so that they weighed when they left. Survival is success. They can gain weight later.
Mostly they sleep on the beach, but as youngsters do, they badger one another. Males bump chests and bite at each other, on the beach and in the water.
Friends of the Elephant Seal docents, in blue jackets, stay informed about the seals. Research on them continues. Recently, Annalisa Berta, professor in the Department of Biology at San Diego State University, spoke to docents on pinniped evolution.
All seals are pinnipeds, marine mammals with flippers. They evolved from land animals, either otters or bears. Look at an elephant seal skull in the FES office, or ask to see a picture carried by the docents on the bluff. Very bearlike.
Pinnipeds appeared in the oceans about 25 million years ago. That makes them newcomers compared to whales, which have been evolving for around 50 million years. The earliest pinniped was identified in rocks from Bakersfield. It was a shallow-water animal, different from the wide-ranging elephant seals. They migrate as far as 3,000 miles from California, and hunt at 1,000 feet and deeper.
The first pinniped had well-developed flippers, but from its teeth, researchers like Berta can deduce that it hunted close to shore. It chewed its food in its mouth. Elephant seals, with their long canines, swallow squid and fish whole and digest them in their small intestines.
The evolutionary record is spotty.
“It’s difficult to find the characters on the road to being a pinniped,” she said.
Her latest book, Return to the Sea: The Life and Evolutionary Times of Marine Mammals, is now available to docents at the FES office.
Christine Heinrichs’ column is special to The Cambrian.