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Re: Rearing to Rear (Was "3 reasons to visit the Field Museum")
T. Michael Keesey writes:
On 6/24/07, Dann Pigdon <firstname.lastname@example.org> wrote:
Male humpbacks are really a sight to behold in the mating season. Often a
female will reject their advances and roll onto her back at the surface,
with her vent in the air. A really large male can still mate with her
though, by getting alongside and rolling onto his own back, then sending
weirdly mobile penis off to explore by itself.
Interesting, since that would provide strong selective pressure for
(Or were you not referring to body size?...)
Well - the larger the male, the 'larger' the male, so to speak. Amongst
cetaceans in general, mating is not always a mutual agreement. An insistent
male has to be larger than the object of his unwanted desire to get close
enough to begin with (especially if the female still has a calf with her).
The appendage in question then has to curve up and over the bulk of her
body, and still have enough length left to do the job (should it
successfully find 'ground zero').
So in whales where forced mating is common, there will be selective pressure
for males to evolve larger body size to not only fend off rival males, but
to physically overpower the females. If more than one male is harassing an
up-turned female (and they *will* gang up at times), then the 'larger' male
is more likely to be able to reach, despite the female's attempt to put
things out of reach by rolling onto her back at the surface.
GIS / Archaeologist http://www.geocities.com/dannsdinosaurs
Melbourne, Australia http://heretichides.soffiles.com