whale sounds

From: Greg Early (gearly1@earthlink.net)
Date: Fri Oct 17 2003 - 11:16:18 EDT

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    Sophie,

    Interesting question (s).

    How do plankton eating whales detect their food, and why do they appear to
    be prey quality or type selective ?

    The easy part first. Whales do appear to be prey selective. Even to the point of selecting certain size (or age) prey of the same species (at least in fish eating species). They also appear to be selective about the density of the prey as well(NA Right whales appear to start feeding only at certain prey densities).

    The hard part. How do they detect their food? We do not really know for sure. Some scientists thing some of it is done by sense of touch, but otherwise we are sure of only one thing ??? it is not smell, as whales do not have the ability to smell.

    Large whales do not appear (for the most part) to be able to produce high frequency sounds (at least nothing like the sounds produced by echolocating dolphins). They even lack the anatomy that these dolphins use to make those sounds.

    Are we listening for those sounds. Yes indeed. The equipment used to hear in the ocean should detect high frequencies as well the low so it is probably not for want of looking. You are correct, however that low frequencies will travel farther than high (if they have the same amount of energy).

    You may also know that there is a relationship between frequency and ???resolution??? of information that can be detected. In other words, the higher the frequency the smaller the target (or the greater the resolution) that could be detected. For low frequency sounds to be of much use for echolocation the target would have to be very large. So the sounds of an animal like a Bowhead whale would only be good for detecting objects about the size of a large house. Turns out that Bowheads live in an area where being able to detect things the size of a house ??? like ice flows???can come in very handy. Some scientists think that this is exactly what Bowheads do to navigate there way through ice fields.

    ge
    -----Original Message-----
    From: Sophie Fielding <sof@soc.soton.ac.uk>
    Sent: Oct 17, 2003 5:44 AM
    To: gearly1@earthlink.net, pita@whale.wheelock.edu
    Subject: whale sounds

    Dear Greg,

             I am interested in the frequency of sound that plankton eating
    whales can produce. From looking at databases, many of these whales, such
    as the baleen whale, communicate at low frequency. I have several questions
    that I have not been able to find answers for.

    How do plankton eating whales detect their food, and why do they appear to
    be prey quality or type selective (Fiedler et al., 1998, DSR)?

    Can these whales produce high-frequency sound (i.e. >150 kHz)?

    If their are no data on whales producing such sounds is it because we are
    unable to "listen" for those frequencies as a result of sound attenuation
    and getting close to feeding whales?

    Thank you in advance

    Sophie



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