Saturday, September 27, 2014

Juveniles crowd the beach

This week's column in The Cambrian:

The unusual anchovy bloom that attracted hundreds of humpback whales to our coast went unnoticed by the Piedras Blancas elephant seals. Pelicans, gulls, cormorants and sooty shearwaters fed wildly on the feast. Sea lions and bottlenose dolphins swept through the mass of small fish, so thick they appeared on fishing boats’ depth sounders.

The breaching whales and plunging pelicans attracted hundreds of human visitors all along the coast. But to the elephant seals, it was just another sunny day. They aren’t interested in food while they are on the beach anyway.

They fast, not eating at all, for the four to six weeks they spend at Piedras Blancas bluff. They live off their blubber. In that way, they are like desert animals. Elephant seals fasting on the beach are like camels that metabolize the fat in their humps when they don‘t have access to fresh water.

Elephant seals have physiological adaptations that conserve water, such as efficient kidneys and convoluted nasal passages that recapture moisture in their breath before they breathe it out. By conserving water, they conserve fat that would otherwise be metabolized.

“They are so different from other animals that we called them Martians in the lab,” said Susanna Blackwell, who earned her doctorate for her study of elephant seals.

In September, juvenile seals arrive for their fall haul-out. That’s the simple description of what’s going on: Seals haul themselves out on to the sand, and there they stay. They arrive one by one, some unknown signal drawing them back to the beach.

The herd gradually increases until thousands are on the beach during October. Then those who arrived earliest begin their return to the sea. One by one, they slip into the surf, until only a few are left when the adult males start arriving in late November for the breeding season.

The juvenile seals range from their first year to 6 years old. The ones that were born earlier this year are returning from their first migration. They left the beach in March and April. No adult seal guided them. How they find their way is one of their mysteries. They entered the ocean, swam away, and hunted enough fish and squid to survive.

That first migration may be only as far as Vancouver Island, although some make it all the way to Alaska. All the ones on the beach have gone north and found their way back to the Central Coast. The smallest seals on the beach have overcome their first ocean challenge.

Mostly they sleep on the beach, but as youngsters do, they cavort with each other. Males tussle, on the beach and in the water. Older seals are generally bigger, but since females never get as big as males, that’s only one indicator of age. Among adolescent males, that distinctive nose starts to grow at age 5. The seals on the beach in September with bigger noses are older.

Compare the noses you see to distinguish a 5-year-old from a 6-year-old. A docent in a blue jacket can show you a drawing that illustrates how the nose develops. They can also let you handle a piece of skin that molted off earlier this year. They are always happy to answer questions and help you appreciate the seals.

Read more here: