Northern Elephant Seals wintering in California

The Elephant seals are large oceangoing mammals. The are two species: the Southern elephant seal and the Northern elephant seal. Southern species are much larger in size and are found in Southern Hemisphere; while Northern species live along the pacific coast of the United States, Canada and Mexico.

Elephant seals derive their name from their great size and from the male’s large nose, which serves to intimidate other males both through its size and its effect on their loud challenge call in the competition for females.

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The Northern elephant seals breed annually and usually return to the established breeding areas (aka “rookeries”). This particular colony is wintering in Año Nuevo national park, California, and comes all the way down from Alaska. They are believed to be able to travel approximately 60 miles a day, so it takes them about 3 months to get to California to breed.

The Northern elephant seals come to the rookery twice a year – once in the late spring and summer for approximately one month to molt and once in the fall or winter to rest if they are young, or to give birth and breed if they are mature. The rest of the year, ten months of the year for most of the animals, they are at sea. It is worth to mention that the north elephant seals are loners and the time they spend on a beach breeding is the only time they socialise.

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Mating occurs about three weeks after females give birth. They will mate with the male who has defended their harem from attack by other males during the nursing period. The mating is often very loud as the females bark when the male bites their neck and pins them down.

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While at sea they spend 90% of their time deep under water. They dive routinely 300 to 900 meters staying down an average of twenty-five minutes before returning to the surface to breathe for two to three minutes. This behavior continues 24 hours a day for periods of several months uninterrupted by visits to land or longer periods on the surface.

The average lifespan of a Northern elephant seal is 9 years, (Southern elephant Seal live up to 22 years). Males reach maturity at five to six years, but generally do not achieve alpha status until the age of eight. Females begin breeding at age 3–6, and give birth to only one pup. Once a pup is born, it feeds on the mother’s milk for a month and then is being left on its own. There is no evidence that that mother-child relationship plays any future role in the life of either.

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The pups gain up to 10 kilos a day thanks to the milk produced by elephant seals which is remarkably high in milkfat compared to other mammals. After an initially lower state, it rises to over 50% milkfat.

The pup remains on the beach, fasting, for an additional 8 to 10 weeks. As the beach becomes less populated due to the departure of females, the pups begin to learn how to get food in the nearshore waters. Most of the pups depart after they are able to swim well.

The males depart the beach as the last of the females leave.

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Some more facts about about elephant seals:

  1. by 1982 the Northern elephant seal was at slaughtered nearly to extinction for their oil-producing blubber and competing for fish;
  2. elephant seals have a squid-based diet; less often they also eat fish and crustaceans;
  3. rivals can recognise each other: when they return to the breeding area they react to the voice of the alpha;
  4. on dry land, elephant seals often go without drinking for extended periods. To avoid dehydration, their kidneys can produce concentrated urine that contains more waste and less actual water in every drop.

 

 

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