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RE: NFC: Re: Fishy Behaviour

chris at yonderway_com wrote: 

>>       > Very few land dwelling species eat their own 
>>      >  young and I am not aware of any that do it to 
>>      >  the degree that fish do.
>>   Lions do.  At least the males of the species anyway.  
>>  You think HUMAN males think with their genitals... male 
>>  lions will eat the young lions to cause the female to 
>>  come into heat again.

>>Doug Dame wrote:

>>That's a partial story as I understand it. When new males move in and take
over an existing pride by driving off the males of "the >>former regime,"
they have been then observed killing off the existing cubs ... which aren't
theirs, of course. This has the effect of >>eliminating the genes that
aren't directly theirs and also (as you say) brings the females back into
heat faster than they would have >>otherwise, which is presumably the
Darwinian double-bonus that makes such behavior advantageous to the genes of
the perps. 
>>I don't recall having heard they "eat" the young as we'd commonly
understand that, nor that it happens under any circumstances >>over than new
regime of bullies deposes former of regime of aging bullies.

Male lions do not typically feed upon the young after they kill them which
seems to prove that they are not killing for sustenance and from my
knowledge of lions (gained primarily from several years as an education
curator in the zoo world) it is accepted that cubs are killed simply to
bring the lioness back into estrous.  Also, and I am not sure how someone
might want to fit this into the discussion, don't forget that many mammals
have the ability to "manage" their pregnancies.  Embryos are often
reabsorbed in times of environmental stress, i.e. food shortages, droughts,
and even overpopulation in some cases.  Some mammals, primarily mustelids
(weasel family) if my mammalogy memories serve me, also practice delayed
implantation and frequently delay the fertilized egg's implantation
indefinitely when times are tough.  Delayed implantation explains many
"miracle births" that occur when a female has not been exposed to a male for
a period of time longer than the gestation period.  Assuming that fish do
not have the ability to manage their reproduction in these ways and simply
are at the mercy of an instinct to produce young whenever and wherever
possible would (could?) explain why many fish take advantage of the
nutritional value of their own spawn.

Someone also mentioned that birds don't typically eat their own young and
while this may be true, fratricide, where one or more members of a clutch
kill and sometimes eat their siblings, is relatively common in the avian
world. This could also be considered a form of Darwinian selection or a
simple population control measure if not utilization of available food

Rob Denkhaus
Fort Worth Nature Center & Refuge