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Marine Mammals
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 Northern Elephant Seal

Image Credit: NOAA

 Northern Elephant Seal
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 National Marine Sanctuaries Where Northern Elephant Seals Can Be Found:
  Olympic Coast
Cordell Bank
Gulf of the Farallones
Monterey Bay
Channel Islands

 Related Environmental Issues:
  Point Source - Oil Spills
Non-Point Source - Runoff
Climate Change

 Activities Related to Northern Elephant Seals:
  Predators Among Us
147 KB, pdf
This lesson will focus on human beings as predators, specifically in coral reef ecosystems.

 Other Resources Related to Northern Elephant Seals:

Scientific Name: Mirounga angustirostris

Category: Pinnipeds

Northern elephant seals, the second largest seal after the Southern seals, live in the eastern Pacific Ocean along the west coast of North America, from Baja, California to Alaska. Mature adult males have a very long flexible snout called a proboscis and because of their large size they are called "elephant seals." Males, known as bulls may weigh 2,000kg (2.25 tons) and are over 5m (14.5 feet) in length. This is about as long as a car! The females, known as cows are much smaller at 600kg (3/4 ton) and measure only 3m (10 feet) in length. On land, they crawl on their bellies, but elephant seals spend most of their life at sea and come ashore to breed, molt, and give birth. At sea, they dive frequently and are rarely at the surface for more than four minutes at a time. Although thousands live in a small space on the beaches, at sea they live a solitary existence. They molt once a year and in this molt they shed hair, as well as the upper layer of skin. This is called a catastrophic molt and usually lasts a month. During this time they stay on the beaches, where the temperature is warmer as they grow their new skin. They have only ear holes, no ear flaps. They are tan to brown to grey in color and their hind flippers are small and not flexible. Males have a life expectancy of 14 years, while the females have a life expectancy of 20 years.

In December elephant seals return to breed at the same sandy beaches on islands off the coast of California. The males arrive first and fight violently for dominance on the beach. In these fights, they will inflate their noses and make noises that sound like drums to warn away the other males. During the time of breeding the males fast and live on their stored blubber. The females arrive and after several days give birth to the pups they have been carrying for a year. Pups weigh 35kg (75 pounds) at birth and are 1.25m (4 feet) in length. (Big babies!) When the pups are born they have black fur, but this gradually changes to silver-gray. After a year, their fur turns to silver-brown. For about 28 days the pups nurse and rapidly gain weight rapidly, about 4.5kg (10 pounds) per day. These pups continue to live on the beach and are called weaners. Little by little, they go into the water and learn to swim and feed. At the time of weaning, the females will mate again with the males and then return to the ocean. One dominant male can breed with as many as 100 cows, but some males may never breed in their entire life. Some rejected males, instead of returning to the ocean, move inland over the coastal highways and come in conflict with humans. One was even hit by a truck!

Elephant seals feed at night and eat squid, eels, sharks, skates, spiny dogfish, and many other marine animals that live in the deep water. They are also powerful swimmers. Females can dive to 800m and males to 1500m. The only marine mammal that dives deeper in the ocean is the sperm whale. Some scientists think that the elephant seal actually sleeps while diving down to the depths of the ocean. While at sea, they eat huge quantities of food that are stored in the form of blubber. This blubber is their source of food on land, as they fast during the breeding period. The predators of the elephant seal are orca whales and great white sharks. Elephant seals are the only marine mammals known to migrate from land to ocean twice in one year first to land for breeding and later for molting. Scientists estimate that they travel more than 20,000 miles in these two migrations. This is like swimming from Boston to Los Angeles roundtrip, twice a year and never sleeping more than 3-5 minutes at a time.

Elephant seals are protected by the Marine Mammal Protection Act of 1972. Before then, starting in the 1700s they were hunted commercially for their blubber which was converted into lamp oil. By the turn of the twentieth century they were almost extinct estimates were from 100 to 1,000 animals. The elephant seal found a new refuge for a rookery in the 1960s at Ano Nuevo State Park, 50 miles south of San Francisco. Many tourists come here to watch them during molting and breeding seasons. Since the Protection Act went into effect, the seal populations have generally recovered and now are estimated to be over 150,000. This is close to the size of the population observed in the early 1700s. Elephant seals can suffer from pneumonia, parasites and a skin disease. They are the only animal that can collapse their lungs as they dive and this ability is being studied by scientists at the Scripps Institute in San Diego. This research could help human babies born with lungs that are not fully developed. Some scientists suggest the elephant seals could be used to map the deep ocean, as they are capable of diving so very deep.

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