reproduction

From: Pieter Folkens (animalbytes@earthlink.net)
Date: Mon Nov 03 2003 - 11:13:24 EST

  • Next message: Pieter Folkens: "more whale questions"

    Yours is a complicated question because it covers some 80 species of
    Cetaceans which range in nominal life spans from around 15 years (some
    porpoises) to over 200 years (bowhead whale).

    Your question's implied complication is double when one considers the
    sex involved . . . male or female? In some species, the males are not
    constrained by competition for females . . . they just go for it as
    soon as they can (less than eight years of age). In others, dominant
    males battle other challengers for the opportunity to mate. In this
    case, a breeding male is not likely to have a successful engagement
    until a later age once they are bigger and stronger to fight for the
    females (older than 12 years old).

    In some whales the female's reproduction years might last from age four
    to fifteen and they can become pregnant every year. In others, the
    female's breeding period might be six to thirty five, buy they may
    carry a calf only every third year. In another species, the female's
    first breeding might come later, say ten years old, and produce a calf
    only every fifth year.

    Another factor is the condition of the species and the environment. If
    a species is greatly reduced by whaling or other impact, reproduction
    tends to accelerate. If the environment is out of whack, say in an El
    Niņo year, they may put off mating until there enough proper food
    readily available.

    So, it is very difficult to come to an 'average' because of all the
    variables. It is easier to determine an average if one specifies which
    species.

    Cheers,

    Pieter Folkens

    On Nov 2, 2003, at 12:57 PM, SpAzEt619@aol.com wrote:

    > Dear Pieter Folkens,
    >
    > On average how many times does a whale reproduce during its
    > lifetime?
    >
    > Amy Bessette
    >



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