Fall Haul-Out

 

Fat seals rest, safe on the beach

In the fall, young seals get the beach to themselves. Away from the bellicose bulls and the touchy adult females, they rest on the beach. It’s Juvenile Haul-Out.

It’s the interregnum between the bull dominance, on the beach to molt during the summer, and returning for the winter breeding season. Juveniles left the beach in the spring, after they joined the adult females on the beach to molt their skin. The young seals have been at sea since May, feeding and adding blubber. They are fat now, their smooth skins filled out.

They will fill the beach until late November, when the bulls start arriving for the breeding season. Not all the seals are on the beach the entire time. They come and go. It’s a good time to see seals of various sizes and levels of development. They are too young to have a full trunk-like nose, but some have the beginnings of one. They are all elephant seals, on their way to maturity.

This young bull is about six years old, judging from the size of his proboscis (nose).

Survival Success

Every seal on the beach is winning the survival marathon. Elephant seals are in constant danger of being eaten by white sharks and orcas.

The smallest are the Young of the Year, last year’s pups returning from their first migration. Of the 90-95 percent that survive to be weaned and enter the ocean for their first four- to six-month migration, less than half survive to return to the beach in the fall. They may be no fatter than when they left, and may have even lost weight, although they may have grown a little longer.

The challenges are great. Each seal must learn, on its own, to hunt food in the dark, cold ocean at 1,000 feet and deeper. Starting out, they have so much blubber that they are buoyant. It takes energy to swim down to find the fish and squid that are their prey. As they swim, they develop more muscle.

Although they practiced holding their breath and diving before they left the beach, out in the ocean they have to hold their breath longer and dive deeper. As they migrate, they get better at it. By the time they are two years old and have made four migrations, they are as good as mature seals.

Evading predators

They have evaded their predators, swimming back to the surface only briefly, through the “lightscape of fear,” to catch a short breath and then dive down again. Rising to the surface though the range of their white shark and orca predators is the most dangerous time for them.

Young seals stay longer at the surface than adult seals. They may need to take time to process the food they caught while they were diving. Longer time at the surface may have accounted for the batteries running out on Monarch, the Cal Poly seal who swam all the way to the Aleutians last year on her first migration. The research team is adjusting the batteries they use for the coming year to account for the greater time the young tagged seals spend at the surface.

Arriving on the beach is triumph enough. Those survivors include seals that will someday breed successfully.

Larger seals are relatively older. I saw some six-year-old males this week, estimating by the size of the nose. Bulls are fully mature at eight years old, so these have some growing and maturing to do before they join the breeding population.

More of the seals on the beach are male than female. Females mature earlier than males, with most having their first pup by the time they are four years old.  

Migration

Seals probably rely on a suite of senses to find their way from California north to Alaska and back again, which UC Santa Cruz researcher Roxanne Beltran describes as “astonishing navigational feats.”  They have some sense of direction, even when they are under water. They likely use some combination of geomagnetic, celestial, acoustic, or olfactory cues to find their way.

Young seals are adjusting their migratory schedule. As they mature, instead of returning in the fall, they will return to the beach in December and January, for the breeding season. As juveniles, they avoid the hectic threats of that season by hauling out in the autumn months.

Sharks

These fat young elephant seals attract white sharks. White Sharks migrate toward the California coast from as far away as Hawaii. The Farallon Islands, Tomales Bay and Monterey Bay are more active feeding sites, but shark-bitten elephant seals are often on the beach at Piedras Blancas.

Scars show severe wounds that the seals somehow survive. Blubber doesn’t have a rich blood supply, and I like to think that it doesn’t have many nerves, either.

This seal survived a devastating attack. 

The sharks store up oil in their livers as they feed on the elephant seals. Sharks will take an elephant seal any time throughout the seals’ range, but juveniles are especially preyed upon in the fall in the Farallon Islands. Sharks attack full-grown bulls around Año Nuevo in December and January.

A good blubber meal gets the sharks through the long winter migration, to the White Shark Café halfway between California and Hawaii. Scientists still aren’t sure why the sharks converge there.

Follow elephant seal and shark migrations at https://gtopp.org/ . Or buy a shark or elephant seal tracking bracelet at the Friends of the Elephant Seal Visitor Center in San Simeon. For $20, you can follow an individual shark or seal on a phone or computer. A docent reported that a 14-foot shark nicknamed Battle Axe was swimming offshore this week.

Digital technology has changed wildlife research. Without it, we would not know where the seals and sharks migrate and how deep they dive.