Hangin’ out on the beach

Over the long holiday weekend a little over a week ago we drove up the coast from Morro Bay back to Santa Cruz and stopped at Piedras Blancas to visit the elephant seals. At this time of year the breeding season is over and most of the seals have returned to sea. The adult females gave birth in late December or early January, were mated soon after, fasted for a month while they nursed a growing pup, and then abandoned said pup on the beach to resume the aquatic phase of their life. Same for the adult males, minus the birth and nursing part, of course. Oh, and most of the males didn’t get to breed, either. Suffice it to say that the adult elephant seals have more or less abandoned the beach for now.

Elephant seals (Mirounga angustirostris) at Piedras Blancas
2019-02-17
© Allison J. Gong

Although there were still a lot of seals on the beach, much of the real estate was unoccupied. Contrast this to the same beach in November 2015, as the seals were starting to arrive for that breeding season:

Elephant seals (Mirounga angustirostris) at Piedras Blancas
2015-11-27
© Allison J. Gong

Elephant seal pups have a tough life. They are born in the dead of winter, on exposed coasts. While they are very young, one of the pups’ greatest mortality risks is being run over and trampled to death by the adult males that are fighting for seniority and the right to mate with a harem of females. The moms do their best to fend off rampaging males, but the alphas are so much larger that they just run over anybody in their way. At this point in their life an elephant seal pup’s main priority is to eat. They nurse almost constantly on milk that is about 50% fat. Pups are born wrinkled, with a lot of loose skin, but they soon fill out and take on the stereotypical look of fat sausages.

After four weeks of intensive nursing, a pup’s life changes drastically. Its mother abandons it on the beach and returns to the sea to begin feeding again and restoring its much-depleted body stores. Remember, she has been nursing a pup and fasting for about a month and a half! Her pup is thus forcibly weaned, because she just leaves and doesn’t come back. Researchers refer to these abandoned pups as weaners.

Pair of elephant seal (Mirounga angustirostris) weaners at Piedras Blancas
2019-02-17
© Allison J. Gong

Most of the seals on the beach in late February are weaners. They will stay on the beach for another two months or so. They have to wait until they molt from their soft baby coat into a more adult coat that will better insulate them in the cold water. And after they molt they have to learn how to swim. They’ll make short forays into the surf and paddle around for a bit, learning how to maneuver their bodies in the water, and then return to land to rest. In the meantime they’re not feeding. This is why it is crucial for them to pack on as much weight during the four weeks that they get to nurse. Attaining that ‘sausage’ look is directly related to a weaner’s probability of a success launch into the ocean.

Pile of elephant seal (Mirounga angusirostris) weaners at Piedras Blancas
2019-02-17
© Allison J. Gong

But not everybody is a weaner. There are also some subadults on the beach. They, of course, swim perfectly well and can head back out to sea whenever they want. The subadults will also need to molt, but that doesn’t happen until the early summer.

Subadult male elephant seal (Mirounga angustirostris) at Piedras Blancas
2019-02-17
© Allison J. Gong

Don’t they have the dopiest faces?

Subadult male elephant seal (Mirounga angustirostris) at Piedras Blancas
2019-02-17
© Allison J. Gong

With the breeding season over, things will be quiet at the seal rookeries at Piedras Blancas and Año Nuevo. Both sites will get frantic again in December, when the adults return to land and the next reproductive cycle begins.

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