Blue whale reproduction

From: Phil Clapham (
Date: Tue Mar 04 2003 - 13:40:36 EST

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    Hi Lee:

    Let's see... there's not a huge amount on this, but here's what I know.

    Gestation is assumed to be 11 months. Average length at birth is around
    7 m, and calves nurse for about 6-8 months before separating. Age at
    attainment of sexual maturity is believed to be 5 years, but this is not
    entirely clear. Females reproduce every two to three years and produce
    a single calf. The calving season (and therefore mating season also) is
    in winter, though whether there is any activity outside this time is not

    No one knows the duration of oestrus for any baleen whale. In other
    mammals, it varies from as little as 45 minutes (e.g. deer) to as long
    as eight days (some canids). There are zero data on oestrus in baleen
    whales, though in some species (e.g. humpback whales) females are known
    to cycle more than once a season; it isn't clear whether this is true
    for blue whales.

    The general female cycle is the same as for other mammals. Testicular
    activity in males - in terms of production of sperm - is seasonal,
    peaking during the winter breeding season. Blue whales have
    comparatively small testes for their body size: the average adult male
    has testes that weigh 70kg. if you think that's a lot, compare that
    figure to male right whales, which despite a smaller body size have
    testes that weigh one ton! this of course relates to the mating system
    - right whales clearly practise sperm competition. The mating system of
    blue whales in unknown.

    Its worth noting that the foetal growth of blue (and fin) whales is the
    fastest in the animal kingdom, some 20 times that of primates. Blue
    whale foetal growth accelerates rapidly in the last few months of
    gestation and the foetus grows at an astonishing rate.

    The bible on this stuff remains Whales, by E.J. Slijper. Out of print
    but still gettable (try It's out of date in some
    respects but is the best book ever written on whale anatomy, function etc.

    Other info is buried in various scientific papers, notably a review by
    Christina Lockyer on Baleen whale reproduction (Reports of the Intl
    Whaling Commission, Special Issue 6: 27-48, 1984).

    hope this helps!

    Phil Clapham

    Lee Hollingsworth wrote:
    > Hi - i'm currently studying animal management at Hadlow college, Kent
    > and am working on a presentation on the reproductive system of the blue
    > whale - no mean feat! I am also hoping to tavel to Tenerife to help
    > their whale & dolphin conservation project in the summer. can you tell
    > me how they physically reproduce, including oestrous cycle, ovarian and
    > testicular function. i already have a lot of info on gestation, calf
    > weight/size etc but would be very grateful for any help or
    > info/websites/books i could be looking at.
    > thanks very much in advance for your help
    > kind regards
    > Lee Hollingsworth


    Phillip J. Clapham, Ph.D. Large Whale Biology Program Northeast Fisheries Science Center 166 Water Street Woods Hole, MA 02543, U.S.A.

    tel. 508 495-2316 fax 508 495-2066 email:

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