The Cambrian

Young elephant seals reign at Piedras Blancas in fall

An elephant seal mugs for the camera. During the fall, the beach belongs to younger seals; adult male bulls will arrive in December.
An elephant seal mugs for the camera. During the fall, the beach belongs to younger seals; adult male bulls will arrive in December. Special to The Cambrian

Lots of seals to see at Piedras Blancas in October. They’re big, but not as big as the adult bulls who will take over the beach in December. In the fall, it’s all rest and rough-and-tumble play among the youngsters.

Juvenile seals, both males and females, come to the beach in the fall for four to six weeks of rest, called the Fall Haul-Out. That’s four to six weeks for each seal. Since they are solitary during their migration, they arrive one by one, from late summer through November. The crowd builds to the most seals on the beach in late October and early November. They gradually leave, one by one, to spend the next six months foraging. The mature adults will occupy the beach during the winter breeding season.

Young males are the ones sparring with each other, in the water or on the sand. Females don’t chest bump each other. They might snarl and snap at another seal that’s climbing over them.

The seals clump together on the beach, flopping right over one another if the mood strikes. Mostly, the others take no notice, or shift a bit to accommodate.

The smallest seals on the beach are the young of the year, the pups born in January. Only about half survive the first migration and come back for their first haul-out. They may not have gained much weight, but any seal on the beach is a survivor.

Foraging for fish and squid to eat is the center of seal life. Bigger is better for males, and digital technology has revealed details of where they go to hunt.

Tracking devices have shown that males, and some females, avoid the shallower continental shelf area, around 200 feet, and head out beyond its edges. Along North America’s West Coast, the continental shelf, the edge of the continental land mass, is narrow. Then it drops off deeper, into the continental slope.

Females generally roam the ocean, feeding as they go in deep waters. They appear not to favor hunting along the bottom for their favorites, lanternfish and squid. That shallow shelf is good hunting territory for sharks. Young seals, favorite prey for great white sharks, dive into the depths of the slope, away from sharks and into richer feeding territory for themselves.

Elephant seals typically hunt at 1,000 feet and deeper. How they catch their prey hasn’t yet been observed, but they probably rely on their eyes to some extent. Those large dark eyes see well under low light conditions. Even though it’s completely black dark at those depths, prey such as Humboldt squid and lanternfish flash bioluminescent light. Elephant seal whiskers are very well supplied with nerves, making them sensitive to moving critters in the water that might make a meal.

When seals return to the sea from Piedras Blancas, they swim past that shallow area and its sharks into their more familiar depths.

The shark monitor acoustic buoy is riding the tides just beyond the Piedras Blancas rocks. Check the Tagging of Pelagic Predators website, www.topp.org for updates on tagged sharks, or install the free IOS SharkNet app on your iPad or iPhone.

Christine Heinrichs’ column appears monthly and is special to The Cambrian.

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