Echolocation and Migration

From: Kim Marshall (kimm@oceanalliance.org)
Date: Mon Sep 22 2003 - 15:46:12 EDT

  • Next message: Kim Marshall: "Hair"

    Question:
    Hello Ms. Marshall,
    My daughter is in first grade and is starting to look up stuff on the
    computer, she has a sheet of questions about whales and we are having
    trouble answering two questions :How do whales find their way? And What
    causes them to leave where they migrate?

    Reply:
    Dear Melanie,
    Whales use a mechanism called echolocation to 'see' with their ears. They
    direct a beam of click-like sounds and listen to the echoes that return from
    objects in the path of the sound. If you direct a flashlight at something
    in the dark, you illuminate the object with light and you can see it.
    Whales can 'illuminate' a silent fish with sound in order to 'see' it. From
    the returning sound, the whale learns the size, shape, speed, and direction
    of the subject. Dolphins can even beam their sound waves into mud to find
    hiding fish! (Seawater and flesh have approximately the same density, so the
    sounds whales emit penetrate the flesh of submerged animals. It has been
    suggested that whales can actually see the inside of their companions and
    their prey. The resulting image might look like an ultrasound picture).
    Fish can't hear the high pitched sounds, so they don't realize they are
    being looked over. It has been postulated that some cetaceans, such as the
    sperm whale, may even use strong pulses of sound to stun their prey!

    ³Toothed whales generally spend most of their time in shallow, coastal areas
    and use sharp, high frequency sounds that don't travel very far through the
    water before being converted into heat. Short, high-pitched, rapid sounds
    used on objects in close proximity allow whales to hear the finer details.
    Some types of baleen whales (like blue and fin whales) spend a lot of time
    in deep, dark waters and use loud low frequency, long-ranging sounds to
    communicate and navigate the seas. Low frequency sound can travel for long
    distances, but only gives broader details. The distance traveled depends
    largely on the depth and temperature of the ocean the sound is sent from
    (temperature and pressure change the conductive properties of water).

    Migration:
    Humpback whales on the east coast of the US travel from southern areas of
    waters of the Dominican Republic where they give birth and mate up to their
    feeding areas in the gulf of Maine and off the eastern coast of Canada.
    Humpback whales of the Pacific migrate from the warmer waters of Mexico and
    Hawaii to the rich feeding area off Alaska. It is believed that these
    ancient paths are taught to the young via songs and memory and we have
    noticed that calves that come to certain feeding areas with their mothers
    will return the the same area the next year even if their mother doesn't.

    Right whales in the northern hemisphere off the east coast travel from
    southern Georgia and Florida to the feeding area in the Bay of Fundy. There
    are less than 500 left of the Northern right whale.

    Gray whales of the Pacific have the longest migration route where they
    travel from Mexico to the Bering Sea (over 3000 miles). They are known at
    times to take a short cut across deeper waters. They also migrate a shorter
    distance via the Sea of Japan. (Evans, Peter., The Natural History of Whales
    and Dolphins)

    If you want to learn more about these subjects please visit WhaleNet¹s
    search page http://whale.wheelock.edu/Search.html.

    Thank you, I hope this information helps your daughter with her project.

    Kim

    Kim Marshall
    Executive Director
    Ocean Alliance (Whale Conservation Inst. & the Voyage of the Odyssey)
    191 Weston Road, Lincoln, MA 01773
    781.259.0423 ext. 14 fax 259.0288
    www.oceanalliance.org www.pbs.org/odyssey
    Please support our efforts to conserve whales and their ocean environment
    through research and education :)



    This archive was generated by hypermail 2b30 : Thu Sep 25 2003 - 11:08:06 EDT