Cambrian: Opinion

Piedras Blancas elephant seal rookery births up 4 percent to about 4,800

The beaches at the Piedras Blancas elephant seal viewing area look much different from the wall-to-wall population of seals a month ago.

Now most of the seals on the beach and in the water are “weaners,” the pups born from December to February, abruptly weaned by their mothers and left behind to teach themselves to swim and, eventually, to eat. The mothers, having fasted for over a month while birthing and nursing, have mated and headed to sea to forage again.

As the action of the birthing and breeding season dies down, it’s time to figure out what just happened. Brian Hatfield, the marine biologist who keeps track of it all, reports that a count of live weaners, pups and orphans at the end of the season indicates that about 4,800 pups were born in the rookery this year, up about 4 percent from last year.

There was no expansion of the breeding range — except for one pup that was born in a small cove just north of the old Piedras Blancas Motel. Because of the mild winter, mortality was low, at about 7 percent. This is much different from the wicked winter surfs and tides of a couple of years ago, when 25 percent of the pups were lost.

The count isn’t over, however, as Hatfield counted about 140 small weaners that may not have stored enough weight to survive long enough to learn to swim after their mothers left. The mother nurses her pup for about a month, and it can gain as much as 10 pounds a day on the rich milk — while the mother can lose 20 pounds a day.

The weaned pup will live on the stored fat until it learns to swim and can embark on its first seaward foraging migration. The weaners on the beach now have lost weight, shed their black birthday suits and turned silvery gray.

They play in the pools among the near-shore rocks, practicing swimming and diving skills, safe from white sharks or other dangers.

Although the number of pups born may seem large, only one in six will survive to age four. While small growth is reported at the Piedras Blancas rookery, there has been a decrease in the population at Año Nuevo, near Santa Cruz. The numbers here may not mean the general population is growing, but reflect a shift in where the seals are going.

We are learning more and more about these statistics as the seals are tagged with sophisticated equipment that monitors their comings and goings, as well as their activities in the sea. A recent statistic reported by time depth recorders is an elephant seal dive to 5,750 feet. These are amazing creatures.

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