Cambrian: Opinion

It’s pup season at Piedras Blancas elephant seal rookery. What to look for if you go

Pup season is the loudest time at the Piedras Blancas elephant seal viewpoint.

Pups squawk their high-pitched plaints, mothers resist male advances and defend their pups from other mothers, beachmasters answer challenges from other bulls. Although these seals spend most of their lives underwater, when they are on the beach, they communicate with their voices.

Seal vocal calls

A new study published in November documents how the male elephant seal calls have changed in the past 50 years. Back in the 1960s, when Burney Le Boeuf studied the seals at Ano Nuevo, San Miguel, San Nicolas and Guadalupe Islands, he recorded distinct differences from one location to another — dialects of elephant seal bellows.

Working with Dr. Le Boeuf for the past four years, two researchers, Caroline Casey and Colleen Reichmuth, found that the calls are now diverse across all locations. The dialects have disappeared, but individual differences now identify each bull.

“These animals emit what we call vocal displays and each male has its own unique vocal signature that others within the colony come to recognize. ... They learn the rhythms,” Casey told the San Francisco Chronicle. “It’s as if a guy walked into a bar and called out, “I’m Sam,” and the other tough guy in the bar said, “Oh, that’s Sam. Sam beat me up before. I’m going to run away.”

The dominance hierarchy reduces the amount of fighting among bulls. That’s important, because they stay on the beach as long as 100 days without eating. Conserving energy helps them prevail over more females, longer.

Pups constantly being born

Pups are often born at night, but daytime births are frequent. More than 5,000 pups will be born in the rookery, so there’s lots going on. Look for seals that are urgently tossing sand on their backs. It doesn’t have much to do with the process, but seals seem to do it when they are stressed. Females will continue to arrive on the beach to give birth into February.

This year’s King Tides happened in December and over the January 20-21 weekend, but tides are still high. This year, they combine with high surf to threaten the newborn pups. The pups can swim, but lack the stamina to survive in the ocean. If washed out, skinny young pups without the buoyancy of blubber can drown.

Gaining weight

Once born, the pups need to start nursing. Pups born in December are already being weaned.

Look for rotund, fat pups. They often rest close to the edge of the bluffs. Some will learn to steal milk from other mothers, ballooning up to even more than the usual 300 pounds. Those 500-pounders are “superweaners.”

They are willing to nurse from any mother willing to tolerate them. Eighty percent of pups nurse on at least one mother other than their own. Not every pup survives, and those bereaved mothers may adopt one or more strays. Some mothers are particular and chase pups other than their own away.

Nursing more than one pup puts the nursing couple at risk. Mothers produce milk from their blubber, losing two pounds for every pound the pup gains. Stray pups are nursing from a limited source.

It appears to even out. Around 95 percent of pups at Piedras Blancas survive to be weaned.

Christine Heinrichs’ column on elephant seals is special to The Cambrian.
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