shark feeding, orca mating, dolphin naming.

From: Orca Network (howard@orcanetwork.org)
Date: Thu May 15 2003 - 17:39:33 EDT

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    Dear Mr.Garrett,
    I'm a 10th grader and I am very interested in the marine mammalogy field.
    I'm taking Oceanography next year but i would like a little more
    information. I was just wondering about a couple of things and i was
    wondering if you can help me with a few questions depending on if my
    information is correct..

    1)Why do sharks circle their prey?
    2)Can they(sharks) smell the difference in species blood?
    3)If Orca's dont leave their pods, how do they find mates?
    4)why are bottlenose dolphin's named that if its their beak that is shaped
    like that because their nose is their blowhole?
    5)how come their is no record of Orca's having multple births? Is it
    genetically possible?
    Thak you for your time and coopreration.

    Vicki

    Thank you for your interesting questions.

    1) I don't know much about sharks, but my guess is they circle their prey
    find the best angle of attack and to prevent escape. They may also be
    making sure it is suitable prey. I understand they sometimes rub their
    sandpaper skin on the prey to test if it's edible, or perhaps to make it
    bleed to determine what it is.

    2) Sharks have a very acute sense of smell, so I suppose they can tell the
    species by the smell, along with visual cues.

    3) I assume you understand that mating within the close family is not a
    good idea due to the likelihood of a genetic bottleneck that might cause
    double recessive genes to cause abnormalities. Recent genetic testing has
    shown that while mating is indeed accomplished within the large extended
    clan, it is done across pods, in other words, with the most distantly
    related males and females in the community. Orca mating systems may be much
    more complicated than that, and we may learn more in years to come, but
    that's what is known so far.

    4) You've certainly found an error in the naming system. That's why the
    scientific names, in Latin or Greek, are generally more accurate than
    popular names. Bottlenose dolphins are called Tursiops truncatus, which is
    derived from the Latin and Greek words for 'porpoise' and 'face'. That
    contains an error as well, however, because dolphins and porpoises are from
    completely different lineages. Thus it is clear that history, with all its
    misunderstandings, is still evident even in scientific naming systems.

    5) There are conflicting reports about whether there are any reliable
    reports of orca twins. I have heard such reports, but they have not been
    well documented to make sure they are true. It is genetically possible,
    however.

    Howard Garrett
    Orca Network
    Greenbank WA
    (360) 678-3451
    www.orcanetwork.org
    howard@orcanetwork.org



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