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 www.bookfinder.com). It's out of date in some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!
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: firstname.lastname@example.org
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