Cambrian: Opinion

Weaners cluster to avoid conflict at Piedras Blancas

This pod of weaned seal pups shows the differences in color among youngsters. Some still have their black birth coat, while others have already molted that into silver gray.
This pod of weaned seal pups shows the differences in color among youngsters. Some still have their black birth coat, while others have already molted that into silver gray. Special to The Cambrian

Piles of fat, comfy weaned seal pups sleep at the protected edges closest to the boardwalk. Mothers conclude caring for their pups. They turn back to the sea, beginning the next stage of life.

Before they leave, they mate with bulls. This is when being the most dominant bull on the beach pays off. Less dominant bulls weigh the risks of challenging the beachmaster’s dominance. They can avoid him by chasing the escaping female into the waves.

Weaned pups sleep away their days, close to the edge of the bluff, out of harm’s way. They are fat now. They nursed up to about 300 pounds in their first month, filling out the skin that was wrinkled when they were born.

The mothers lose about a third of their body weight nursing their pups, so they are thin and depleted now.

Mating fertilizes the female’s egg, which makes only the first few cell divisions and then stops developing. In a process called delayed implantation, the fertilized egg stops there and waits about three months before continuing to develop. Females spend those three months foraging at sea, gaining weight, before the new embryo starts making demands.

There are 11 months between mating and birth, but actual gestation is only eight months. Typically, every female has one pup every year.

Adult bulls guard their harems vigilantly. Watch as a bull arrives on the beach. The bulls already there will either move toward him, threatening and chasing him away, or move away from him. A bull that appears to be sleeping will take notice of the intruder. Watch him open an eye and raise his head if another bull moves toward him. No rest for the weary beachmaster.

Most dominance interactions consist of a threat, followed by retreat, either by the threatening bull or the one being challenged. When one bull moves away from another, it’s called displacement. The relationship is clearly apparent, to bulls as well as observers.

Weaners have moved up the beach, close to the boardwalk. High tides, as well as conflict between bulls, put pressure on them to clear out. One got so close to the fence that visitors were reaching though the fence to pet her. The Marine Mammal Center sent a team to rescue her. Team members checked her out, found she was in good enough shape, and relocated her to a more remote beach.

They named her Black Beauty, for her black birth coat. All pups are black when they are born. They shed that black coat around the time they wean. Black Beauty’s hair was falling out, leaving her with the silver-gray of her next stage in life.

Adults will continue mating on the beach into March. When no more females are left to keep the males on the beach, they will leave to forage in the open sea as well. A few usually stay for a few weeks, apparently sleeping and resting up after a busy breeding season.

Then the beach becomes the province of all those weaned pups, as they prepare for their first migration.

Christine Heinrichs’ column appears the fourth Thursday of each month and is special to The Cambrian.

FES update

Check out the updated webcam at www.elephantseal.org, the Friends of the Elephant Seal web site. It now has sound! So you can listen to the music of the seals.

Friends of the Elephant Seal is interviewing prospective volunteer guides for a training class March 11. Apply for this interesting, exciting and rewarding position online at www.elephantseal.org, Become a docent. Please feel free to contact FES via email fes@elephantseal.org or phone (805) 924-1628.

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