About 5,300 elephant seal pups were born in the rookery at Piedras Blancas this year, up 2.5 percent from last year, but the survival rate was lower than last year. Brian Hatfield, the marine biologist who counts them, bases the number of pups born on the number of adult females on the beach, assuming that each one will have one pup. (No one has ever observed twins being born.)
When the birthing is over, he counts live pups, including those that have been weaned, and orphaned pups. That number was about 4,500, a loss of 15.5 percent of those born. Last year, births were up 4 percent from the year before, and the mortality rate was only 7 percent.
Survival depends on a number of factors. On the crowded beach, pups can become separated from their mothers in many ways. Weather is also a consideration. The newborn pups are not very mobile, and they don’t know how to swim, so high tides and high surf can cause trouble.
The mother nurses her pup for one month, then mates and goes to sea. The pup must learn to swim on its own after that, and if it doesn’t get enough milk to develop a reserve of fat to get it through the learning process, it won’t survive.
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This year’s pups have headed to sea on their first journey and the beaches here are now filled with other survivors, juveniles up to about 6 years old who have come in to begin the molting season. They are joined by females that headed to sea in February to forage after fasting, birthing, and mating and have returned to molt.
The molters look pretty scruffy and visitors often ask if they are sick. Some look like their sunburn is peeling, others appear to be wearing shabby sweaters or tattered blankets. The annual process, which takes three to four weeks, is called a catastrophic molt, when they shed a layer of skin and tan or brown hair to reveal a smooth new gray coat beneath. The molt is a thin layer, with soft hairs on the outside, rougher root hairs that resemble Velcro on the inside.
It’s not easy to tell males and females apart until they reach about 4 years old, when the males can be identified by their pointed noses, which grow longer each year until they become the trunk-like proboscis that gives elephant seals their name. They can also be identified by the way they play, sparring and bumping chests together, practicing for more serious encounters when they become mature contenders for breeding rights. The molting season will continue through the summer, with different age groups coming in at different times, somehow knowing when it’s their turn to molt and where to go to do it.