Elephant seals began coming to the Piedras Blancas Rookery in 1990. Now about 25,000 elephant seals will use the seven miles of beaches.
Elephant seals began coming to the Piedras Blancas Rookery in 1990. Now about 25,000 elephant seals will use the seven miles of beaches.
Elephant seals began coming to the Piedras Blancas Rookery in 1990. Now about 25,000 elephant seals will use the seven miles of beaches.
Elephant seals began coming to the Piedras Blancas Rookery in 1990. Now about 25,000 elephant seals will use the seven miles of beaches.
Elephant seals began coming to the Piedras Blancas Rookery in 1990. Now about 25,000 elephant seals will use the seven miles of beaches.
We know this story is about a subject outside our county, but it’s still very interesting and something that is worth a day trip to the coast.
Piedras Blancas is four miles north of Hearst Castle along Highway 1. You could visit in one long day but better if you could make it a weekend visit by going to Hearst Castle or some of the other attractions in the area.
Elephant seals began coming to the Piedras Blancas Rookery in 1990. Now about 25,000 elephant seals will use the seven miles of beaches. The rookery is where the seals breed and give birth. Elephant seals spend most of their life at sea; however, each seal hauls out (comes ashore) twice a year. They are never all here at the same time. The seal calendar is divided into three seasons: birthing and breeding, molting and the fall haul-out. We are bringing this up now because December is one of the prime times to visit.
The adult males begin arriving in late November and will continue to arrive through much of December for the birthing and breeding season. Elephant seals give birth and mate in harems. The adult males weigh 3,500 to 5,000 pounds and only the strongest and most aggressive will reach the rank of alpha, referred to as beach-master. Harems commonly have 20 to 50 females, the size of the harem depends on the beach-master’s ability to defend his territory. The males have a loud, guttural-sounding resonant call that is unique to each male and helps them to identify rivals.
As the pregnant females arrive in December and try to choose a safe place on the beach to give birth and raise their pups. The beach-master will help protect the pups from other males that will try to sneak in and disrupt the mother and pups.
January is the month with most births and the mother will usually give birth in a few days after arrival. The mom will immediately turn and bond with the newborn. Once the young pup finds one of the two nipples it will nurse on milk that is 12 percent fat and will increase to 60 percent fat.
Something that is amazing to us is that the mother only nurses the pup for four to five weeks but in that time the pup will grow from about 70 pounds at birth to 300 pounds. During this period of nursing the mother loses about 40 percent of her body weight. In her last week of nursing the mom comes into estrus and will mate with the alpha male and return to sea to forage and gain some of the lost weight back. The pup is now on its own, ashore. The weaned pup will live on its blubber for two to three months until it learns to swim, dive and feed on its first trips to sea. During this time the pups will lose about 25 to 30 percent of their weight. The pups suffer a high mortality rate at sea during these early foraging trips mainly caused by predation and poor foraging. They have about a 50 percent mortality rate mainly from killer whales and great white sharks.
One research group showed that only 1 percent of the seals live to be 20 years old.
The females foraging trip lasts for about 2 1/2 months until she returns to shore to molt for about one month. Though pregnant when she leaves the beach in February the fertilized egg does not start to develop until after she molts in May, that is when the egg will implant to the uterine wall. After molting the female will return to sea for the entire gestation period to forage until giving birth mainly in January and early February. When diving for food the seals can hold their breath for 100+ minutes and can dive up to a depth of 5,000 feet but usually about 1,000 to 2,000 foot depth. The dives average about 23 minutes with only 2-3 minutes on the surface between dives. The females tend to go north and west from Piedras Blancas for as much as 3,000 miles and feed mostly on small fish and squid. The males feed mainly from coastal Oregon to the Aleutian Islands and are mainly shallow feeders along the sloping ocean floor where the continental shelf drops off.
In March, the adult males will leave the beach after losing as much as 30 percent of their body weight. The weanlings are going to “swim school,” learning swimming, holding their breath, and developing their underwater vision. Their vision is 10 times as sensitive as ours and can see much better in the dark waters of feeding depth. Females will also start arriving to molt. April-May is the big molting time where they grow a new layer of skin and hair cells as the old layer falls off in patches.
June-September is a time for the older males to molt and with their first sign of puberty — the growth of the nose (proboscis). The nose growth and the change of the thickness of the neck area are marks of the advancement of adulthood. A few females will live up to 20 years old almost no males will reach the age of 14. In September-November, the juveniles return from their post-molt migration. After six months at sea the seals are social again. The elephant seal year begins anew with the arrival of the first adult males in late November.
If you have the opportunity the months of December and January are wonderful times to visit Piedras Blancas Northern Elephant Seal Rookery.
Jim Cunningham and Flip Hassett are both retired, but they remain active in Merced County as community advocates, local history buffs and photographers.