Bull molting season

 Fewer but bigger seals on the beach

It’s bull seals’ turn to take over the beach. They are here to rest and shed their skin in July and August, the annual molt.

Summer marks the conclusion of the short post-breeding migration. The seals on the beach are mostly pretty good size, but they will get a lot bigger during the long migration, from August to November.

Catastrophic molt

All elephant seals molt their skin once a year. Female seals and juveniles were on the beach in May and June. They have returned to the ocean, leaving the beach to the bigger males.

This group of elephant seal bulls looks ratty, but they are just molting their skin. Note the crease beginning to develop in the nose of the seal in the center, indicating that he is six to seven years old. (Christine Heinrichs photo)

Last year’s brown and tan skin, actually a layer of keratin, peels off in chunks, taking the hair with it. Beneath it is a pearly gray or silver coat. They look terrible, but it’s normal. Back in the 1960s, before locals recognized the seals, a resident who saw one called the police to report this sickly seal. An officer came out and agreed that it looked bad, and shot it to put it out of its misery. Burney LeBoeuf recounts the incident in his book, Elephant Seals: Pushing the limits on land and at sea.  “Of course, the seal was fine; it was just molting.”

Ask a blue-jacketed Friends of the Elephant Seal docent to see and touch a sample. It’s rough, not soft and silky, like otter or fur seal fur. Elephant seals rely on their blubber for warmth, not their fur.

Seals spend an average of 32 days on the beach to molt. They arrive and leave individually over the summer months. Seals are solitary at sea. Every seal for himself.

Adults and youngsters

The seals currently on the beach are mostly subadults, about six years and older, and fully adult males, eight years and older. The size of the nose is a rough indicator of age. It starts growing when the seal is about five, and continues throughout its life. A few juveniles, and even some of last year’s pups, now called young of the year, find places to rest among their much larger cousins.

Sleeping in the sand

Notice that seals sleeping on their sides breathe only through the nostril that is on the opposite side from the sand. It’s a reflex behavior, shutting the nostril close to the sand to avoid inhaling sand. This ability to close one nostril independent of the other may be related to their adaptation to deep diving under high pressure.

Navigation

Exactly how elephant seals navigate their migration, as far as 5,000 miles, isn’t known. Experiments that took seals about 40 miles from their home rookery showed they found their way back in a couple of days. Tracked during their dives, the researchers found that even as seals drifted downward on their dives, spiraling as many as 20 times, they headed in their original direction when they got back to the surface.

Since they are underwater most of the time, whatever clues beckon them on their way must be ones that they can discern underwater. That could include acoustics (sound), geomagnetism, and visual clues from the shoreline.

I wonder if they look for Davidson Seamount and Morro Rock. What does their underwater world look like to them?