Killer Whales, Feeding Habits

From: Dagmar Fertl (dfertl@geo-marine.com)
Date: Fri Nov 21 2003 - 10:51:14 EST

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    Hi Dagmar,

    Can you tell me why transient killer whale pods seek out sea lions/whale
    calves and other mammals while resident killer whale pods eat mainly fish?

    Thanks for your help!
    Nancy Krantz
    **********************************
    Nancy,

    Both populations maintain social isolation from one another, and also differ
    in genetic structure, morphology, behavior, distribution patterns, and
    ecology. The 'residents' are fish specialists, while the 'transients' are
    primarily mammal hunters.

    Basically, the two different populations of killer whales - residents and
    transients - have over time, become specialized for feeding on these
    particular types of food. It is likely that poulations with dietary
    specializations exist wherever sufficiently abundant and reliable prey
    resources are available to sustain them year-round. The reason is basically
    that the residents happen to occur in the areas where fish, such as chinook
    and coho salmon occur. Even though mammals are around 'residents', they do
    not eat them (this doesn't mean that the other marine mammals aren't
    harrassed or on occasion, killed sometimes). Transients, depending on which
    part of the country they live, eat different types of marine mammals and
    even seabirds.

    Just to complicate matters even more, besides residents and transients, a
    third population occurs 'offshore'. No one knows the feeding habits of those
    whales.

    Hope this answers your question.
    Dagmar Fertl



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