• Many animals migrate or travel seasonally from one location to another. Monarch butterflies, salmon, geese, and buffalo are just a few of the animals well-known for their migrations. Although northern elephant seals (Mirounga angustirostris) may not be the first thing you think of when you hear the word migration, their journey is truly unique.

    Northern elephant seals migrate farther than any other mammal. Each year, females travel between 18,000 kilometers (11,200 miles) and males travel 21,000 kilometers (13,000 miles). They range from their breeding grounds on off-shore islands and some mainland coastal areas in Southern California and Mexico to their feeding grounds off the coast of Alaska and the Northern Pacific. For a marine mammal, such a long migration means a lot of time at sea, and northern elephant seals spend six-eight months there each year. Most of their time at sea is spent deep under the surface. Their dives typically last from 20−30 minutes, with only minutes at the surface between each dive, though they have been known to stay underwater for almost two hours.

    One reason the annual distance the northern elephant seals travel and the time they spend at sea is so high is because they are the only mammal to make two complete migrations each year. While ashore for breeding in Southern California and Mexico, northern elephant seals do not feed. After breeding, they migrate north to their feeding grounds in the North Pacific. They return to their breeding colonies to molt before traveling north again to feed.

    Male and female northern elephant seals do not travel together during migration. In fact, they travel completely different migration routes and feed in different locations and on different prey. Males feed primarily on fish closer to shore, while females stay farther out at sea and feed primarily on squid.

    The distance they travel over their two annual trips and the different paths taken by males and females make the migration of the northern elephant seal unique.

    1. Northern elephant seals are marine mammals. How have they adapted for spending large amounts of time at sea?

      Marine mammals have adapted to the deeper pressure of the ocean by developing lungs and ribs that collapse and a higher tolerance for nitrogen. They also use oxygen more efficiently, allowing them to stay longer underwater without breathing. Their bodies have adapted to be more hydrodynamic, with appendages that serve to propel them through the water. Additionally, they have adapted a layer of blubber to stay warm at the cold temperatures deeper in the ocean. Finally, they have developed adaptations to sense things and communicate in the darkness of the deep ocean.

    2. Scientists have had difficulty identifying the complete diet of the northern elephant seal. Why might this be difficult?

      The northern elephant seal spends large amounts of time at sea and has a large range. 

    3. The northern elephant seal is a success story for conservation. Since being hunted almost to extinction in the 1800s, the population has grown significantly. What are some other conservation success stories? What actions have helped preserve these species?

      Answers will vary. Some commonly known success stories include bald eagles, grizzly bears, Indian rhinos, lion tamarins, and Przewalski’s horses. Successful conservation efforts often include a combination of legislation and education. Sometimes captive breeding can also aid success.

  • Term Part of Speech Definition Encyclopedic Entry
    breeding colony Noun

    group of animals gathered together for the purpose of mating and/or raising young.

    mammal Noun

    animal with hair that gives birth to live offspring. Female mammals produce milk to feed their offspring.

    mammal Noun

    animal with hair that gives birth to live offspring. Female mammals produce milk to feed their offspring.

    migration Noun

    movement of a group of people or animals from one place to another.

    migration route Noun

    path followed by birds or other animals that migrate regularly.

    molt Verb

    to shed fur, skin, feathers, or other body covering.

    prey Noun

    animal that is hunted and eaten by other animals.