Point Reyes National Seashore--Northern Elephant Seals

Northern Elephant Seals (Mirounga  angustirotris) are marine mammals with a life story that reads like a bizarre collection of extremes.

Above you see a bull seal bellowing and displaying his "shield", the cornified or thickly calloused skin that develops on the male's chest as he matures.  He is trumpeting with the aid of his probiscus, his elongated snout and its unique resonating chamber.  Two weaned pups lie on the beach in front of him.

In February, arrival at the Elephant Seal Overlook at Chimney Rock in the Point Reyes Seashore places you right in the middle of birthing and breeding season, one of the two times during the year that elephant seals come ashore.  In the winter they arrive for pupping and mating, and in the summer females and juveniles come ashore for a complete molt of their fur.

The males arrive first, establishing their breeding territory on the beach and defending it against the challenges of other arriving males. The pregnant females arrive after the territories have been established, become part of the "beach master's" harem, and give birth to their pups.  The females fast and sleep while they are nursing their pups and survive on the fat they have stored while foraging in the ocean for the previous six to eight months. The males also fast once their harems are established, and spend their time defending territories and mating.  Other males are permitted on the beach if they remain flattened and still.

Because the female body is capable of delayed implantation, the season's births are timed for this period in the winter and many of the pups are born on the same day. The female nurses the pup for about 30 days and the baby gains weight quickly on her rich, pudding-like milk. Even though the pup is weaned after only a month, they have enough fat stored to sustain them for the next thirty days when they are ready to swim and forage for themselves.

Here's where the story gets rough.  Adult males measure from 12 to 18 feet in length and weigh 4400 to 6000 pounds.  A bull rearing up to bellow can measure eight feet in height.  Adult females range from 9 to 10 feet in length and weigh from 1300 to 1900 pounds, making them approximately one-third the size of males. Mating begins about three weeks after the females give birth, and the male lumbers through the harem of females and newborns to breed, sometimes trampling pups in the process.

In the image above, a weaned juvenile comes very close to being trampled.  In the image below, you can see that he managed to wiggle out of the way while the male reared up.

Soon after mating the females return to the ocean and feed continuously. "Continuously" is meant literally. Scientist believe that elephant seals don't sleep while they are feeding, at ocean depths of over a mile, but take "cat naps" instead.

Elephant seals can spend 90 minutes at a time underwater, coming back to the surface for only a few minutes before diving again.  One of their many unique adaptations is the ability to compress their lungs and carry sufficient oxygen in their blood stream to remain under water for long perods.  This compression also reduces their bouyancy and aids in their deep dives.      

Hunted to near extinction in the 19th Century, the come-back of the Elephant Seals attests to the importance of the 1972 Marine Mammal Protection Act.  Many other factors continue to impact their survival today, including climate change, over fishing and consumption of plastics.

Links and Resources:

Visit all my posts on Stinson Beach and Point Reyes National Seashore
Point Reyes Elephant Seals
The Northern Elephant Seal Newsletter full of interesting facts about their lives and amazing adaptations.