Friday, August 28, 2015

Sleeping giants

Summer vacation draws crowds of visitors to Piedras Blancas to see the elephant seals. In August, adult and subadult male seals are on the beach.

Seals are on the beach year round, but as migratory animals with an annual cycle, they are always coming and going. There are fewer seals on the beach in summer than other times of the year.

The seals come and go individually. They don’t live in a group in the ocean, so they make their way back to Piedras Blancas on their own schedules. A large male may lift his head out to announce himself, perhaps inviting a sparring match. Fighting isn’t serious at this time of year, with no females around. Male seals are usually willing to take on a challenger.

These are the biggest, the grand bull seals, weighing as much as two and a half tons. This is a seal worth seeing. Their pendulous trunk-like noses, technically proboscis, give them their name.

They come to the beach to molt their skin at this time of year. Circulation to the hair follicles of the old skin stops, and it simply peels off. Blood flows to the new skin underneath. Research on harbor seals using thermal images show that the new skin gets much warmer as blood flows to it to help it grow.

The seals’ short, stubbly fur looks nearly black when it’s wet. As the sun dries it, it takes on a lighter brown color. Elephant seals weren’t hunted for their fur, the way otters and fur seals were. They were hunted for their blubber, used for lighting oil and machinery lubricant. The invention of electric lighting and lubrication alternatives from petroleum helped save them.

Sea otters, whose fur has as many as a million strands per square inch, rely on their fur for warmth. Those long, waterproof hairs and soft underfur trap air, keeping their skin dry and insulating them against the cold water. Sea otters are creatures of the surface, diving down to the bottom in shallow waters, as far as they can go in one to four minutes. Elephant seals are creatures of the deep. At 1,000 feet and deeper, the pressure would squeeze any trapped air out of their fur. As in so many other ways, elephant seals are adapted to their environment and the niche they occupy.

Males being naturally competitive, they may spar with each other, on the beach or in the water. Mostly, they sleep. Awake or asleep, they may hold their breath for ten or fifteen minutes, apnea. That’s normal for them. As deep divers, they are accustomed to holding their breath. Typical dives are 20 to 30 minutes, but dives of an hour are typical, and dives over two hours long have been reported. When they are on land, each breath expends moisture and energy. Taking fewer breaths, called sleep apnea, is a problem in humans but for elephant seals on land, it conserves energy.

Watch one or two individual seals to see how long they go between breaths. Ask a blue-jacketed docent to show you a sample of shed skin. They are on duty every day.

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