Cambrian: Opinion

Female elephant seals are molting on the beach at Piedras Blancas this spring

Seals crowd the beach

Spring is the most crowded season at Piedras Blancas. More seals are on the beach than even during breeding season, when over 5,000 pups are born.

In April and May, adult females and the juveniles of both sexes return to molt their skin. That’s all 5,600 females who had pups on the seven or so miles of beaches that are considered the Piedras Blancas rookery, and the females who — for one reason or another — didn’t have a pup this year.

The seals look ratty, with sections of the old brown skin peeling off. The seals are fine. It’s normal, a process that is called a “catastrophic molt.”

Other seals molt, but more gradually, a few cells and hairs at a time, so it isn’t so noticeable. It’s the way they get new skin once a year. It takes about six weeks.

They arrive on the beach one by one. The new skin is already forming beneath the old skin. Within a few days, the old skin begins to peel off — first around body openings such as eyes and nose, and around scars. Bits and pieces float across the beach, but it doesn’t usually make its way up to the bluff.

Friends of the Elephant Seals docents in their blue jackets have samples of skin to show visitors. Children especially enjoy handling it. Some adults recoil from it. Some say it feels more like Astroturf than the soft fur they anticipated.

The old hair is tan and brown. The new skin being exposed is pearly gray. The new hairs that are just beginning to grow are transparent at first. As the new coat grows, the seals look smooth and sleek, except for any old scars. Those are permanent.

Adult males are not on the beach, but some sub-adults 5 and 6 years old are bellowing and sparring. Their noses are not fully grown, but different from the females, whose noses never develop that way. Adult bulls are off on their spring migration to the north, gaining weight lost during the 100-day fast of the breeding season.

They will return in July and August, when they molt their skin. Seals do not eat while they are on the beach. The females have been out in the ocean feeding for two or three months since they weaned their pups. They’ve regained some of the weight they lost and are ready to start on next year’s pup.

Females can gain 2 pounds a day when they are foraging at sea. The females’ bodies begin to make the changes needed to have a pup next season. The egg fertilized at the end of the breeding season will now start developing into an embryo.

After she’s finished molting and returns to the ocean, that embryo will implant in the uterine wall and begin normal development. When they leave the beach after molting, they will remain at sea until they return to give birth next January.

Christine Heinrichs is a certified California Naturalist who writes about wildlife.
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