Northern Elephant Seals

 

In December, male and female adult northern elephant seals haul out their huge bodies to fight, give birth, and mate at raucous rookeries on the Farallon Islands and at the Point Reyes National Seashore. The male elephant seal is a sight to behold, up to 15 feet long, 4,500 pounds, with a huge bulbous nose that inflates with air and makes a thundering noise used to intimidate other males.

Female elephant seals are paltry and delicate in comparison, a third of the size of males at 10 feet and 1,500 pounds, a perpetual smile seeming to play upon their large faces. Bulls vocally threaten each other for access to females, sometimes rearing up their two-ton bodies to slash and bite each other, while the females are preparing to give birth and nurse their pups. On South East Farallon Island, approximately 300 pups will be born this breeding season, quadrupling their body size before being weaned.

Breeding

Northern elephant seals breed from California down to Baja California, while the non-breeding population ranges from central North Pacific and Alaska. Males defend access to a group of females by establishing dominance, mostly using vocal threats to scare off other males. These “clapthreats” are made using their elongated and fleshy nose, called the “proboscis,” which inflates with air and makes a sound like a drum that can be heard a mile away. They make vocal threats to establish dominance, only rarely engaging in battle. But in battle, the elephant seal is a sight to behold. His proboscis is huge, hanging over his lips by up to two feet, and his chest is covered in a thick, toughened, heavily scarred and calloused skin called a chest shield.

When vocal threats are not enough to chase off other males, battles ensue. They rear up, using their front flippers for balance, and slam down on each other’s chests, ripping gaping holes in their chest shields, spraying blood on the sand and in the water. These are not battles to the death, but fights to gain access to a harem of females. After establishing dominance, “alpha” or dominant bulls jealously guard their beach, quickly chasing off any interloper males who attempt to mate with the females who come into estrus. Interloper males tend to be younger males, and they either go to “Loser Beach” to spar and practice fighting for next year, or hang around at the perimeters of the harem to try and sneak in to mate when the alpha male is distracted. They are rarely successful, as females will protest loudly, and the alpha males, despite their tremendous bulk, will charge quickly down the beach to scare off other males.

Females begin to arrive in late December and January and give birth to their pups from the previous year, 3-5 days after arriving at the rookeries. The pups are born four feet long with silky black fur, weigh 60-80 pounds, and are voraciously hungry. Pups bleat plaintively when they are hungry, and these bleats mix with the threatening trumpet of the alpha male and the females’ growling threats. The sounds of the pups should be familiar to you, as they were featured in the Lord of the Rings and Jurassic Park. A sound crew visited the The Marine Mammal Center to record the cries of the rescued elephant seal pups that are recuperating in the hospital, transforming the seals’ pleas for milk into evil and otherworldly creatures’ snarls.

Female elephant seals nurse for several weeks, aggressively defending their pups and their spot of beach from other females with vocalizations and bites. They feed their young such fatty milk that pups will gain an average of 10 pounds each day.  The milk is so rich (50-60 percent fat) that the pups will triple or quadruple their birth weights in about four weeks. The females do not eat the entire time they are nursing and lose an average of two pounds for every pound their pup gains.

After nursing for close to 28 days, females abruptly wean their pup, and mate with the alpha male, and set off to the continental shelf to replenish their fat stores after losing close to 500 pounds in nursing.  By March, most of the male and female elephant seals have departed the rookeries, and the “weaners” are left on their own. Weaners clump together for warmth and safety, and after a month of fasting will venture out into the ocean for short stints on their own to develop their foraging skills. Pups are born without the ability to swim and thus must build up their swimming and hunting skills.

A life in the open ocean:

              Elephant seals make one of the longest migration of any marine mammal, with females migrating a total of 11,000 miles in semi-annual trips to the North East Pacific and the males migrating for a total of 13,000 miles for their semi-annual trips to the Aleutian Islands. They only come on land for breeding and molting. Molting takes place in several waves, with juveniles and adult females molting in April and May, the adult males in summer, and juveniles molting in fall. They undergo a “catastrophic molt” meaning they lose their hair and the upper layer of skin all at once, replacing it with new fur.

Elephant seals spend up to 90% of their lives underwater, about 5,000 miles offshore, and thus rarely seen at sea because they are constantly making deep dives for food. They can dive up to 2,500 feet, and usually spend 20-30 minutes underwater, only coming up to breathe for 3-5 minutes before making another dive. They hunt mesopelagic fish and squid, deep-water bottom dwellers, skates, rays, sharks and rockfish. They are preyed upon by White Sharks, Orcas, and before 1922, humans.

Population:

Prior to the 20th century, elephant seals were almost hunted into extinction by humans for their oil rich blubber. By 1892, there were only 50 to 100 seals left in a colony on Guadalupe Island off of Baja California. In 1922, Mexico granted them protected status, and the United States soon followed suit. The elephant seal population has bounced back to roughly 160,000, close to the estimation of their original numbers. The Sanctuary supports more than 1500 individuals in Point Reyes and 500 individuals at South East Farallon island.

Would you like to learn more about Northern Elephant Seals?

The Marine Mammal Center rescues elephant seal pups in addition to other marine mammals and has an excellent fact sheet about elephant seals. California State Parks also has an informative fact sheet on Elephant Seals.

See the elephant seals at Chimney Rock in Point Reyes National Seashore or Año Nuevo State Reserve.

 

By Mara Flores Naumann
Published: December 2005

Special thanks to Linn Johnson, Beachwatch volunteer and Año Nuevo State Reserve docent, and Jacquie Hilterman, Volunteer Supervisor/Marine Science Coordinator at The Marine Mammal Center, for sharing their excellent and extensive knowledge of elephant seals.