colour perception in whales (fwd)

From: Pita Admininstrator (pita@whale.wheelock.edu)
Date: Wed Feb 16 2005 - 01:09:11 EST

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    Subject: colour perception in whales

    > Do Whales see in black and white or in color?

    Dear Merryl ( and 2nd graders):

    The order of whales (Cetacea) contains more than 80
    species. This diversity includes animals that live and
    forage near the surface, and others that dive
    regularly into the dark depths. The requirements for
    sight differ in these extremely different environs.

    It appears that whales and dolphins that keep near the
    surface have the most accute eyesight. while the deep
    divers rely less on eyesight.

    Eye sight relies on receptors which are modified nerve
    cells called rods and cones. Seeing in dim light
    relies mainly on the rods. Cetaceans have a greater
    number of rods as well as larger rods than those of
    terrestrial mammals. Deeper diving mysticetes (baleen
    whales) have the longest rods of all.

    Cones are the receptors associated most with colour
    perception. The retina of most whales do have cones.
    Therefore we can say that most whales can perceive
    colour. However, colour becomes meaningless as one
    dives more than a few meters below the surface where
    most of the light at the red end of the spectrum has
    been absorbed by the water above.

    The reason I say "most" can perceive colour is that
    some species of cetaceans have very small, much less
    functional eyes. For these few species, seeing dark
    and light is about all they can hope for.

    Cheers,

    Pieter Folkens
    Alaska Whale Foundation



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