Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!purdue!decwrl!shelby!neon!Gang-of-Four!barbara
From: barbara@Gang-of-Four.Stanford.EDU (Barbara Chapman)
Newsgroups: sci.bio
Subject: Re: War and Peace and Chimpanzees
Summary: Different reproductive strategies
Message-ID: <1990Jan30.023731.26199@Neon.Stanford.EDU>
Date: 30 Jan 90 02:37:31 GMT
References: <12900@cbnewsd.ATT.COM> <1283@oravax.UUCP> <31315@shemp.CS.UCLA.EDU>
Sender: barbara@gang-of-four.stanford.edu
Organization: Computer Science Department, Stanford University
Lines: 52

In article <31315@shemp.CS.UCLA.EDU> frazier@oahu.UUCP (Greg Frazier) writes:
>In article <1283@oravax.UUCP> ian@oravax.odyssey.UUCP (Ian Sutherland) writes:
>+In article <12900@cbnewsd.ATT.COM> kja@cbnewsd.ATT.COM (krista.j.anderson) writes:
>+I believe (correct me if anyone knows I'm wrong) that there are species
>+(not mammals, but species) which have no such "instinct".  If so, what
>+permits such species to get along without such instincts?
>
>There are many species of fish and reptile which prey upon
>their own young.  A prime example of this is the American
>alligator.  This is a positive trait in the alligator, because
>it is at the top of the food chain in its biosphere.  Not that
>this has any direct bearing upon mammals in general, or chimps
>in particular, but it does show how aggression/predation
>against an animal's own species can be a postitive trait.  On
>the other hand, it raises questions such as why don't mammilian
>carnivores such as bears exhibit this behavior?  I realize that
>bears are omnivores and actually get most of their calories from
>vegetation, but since they were at the top of the food chain,
>did they really rely upon disease and starvation to limit their
>population?  Or have there always been enough human beings around
>to limit their numbers sufficiently?
>
>Greg Frazier
>...........................................................
>"They thought to use and shame me but I win out by nature, because a true
>freak cannot be made.  A true freak must be born." - Geek Love
>
>Greg Frazier	frazier@CS.UCLA.EDU	!{ucbvax,rutgers}!ucla-cs!frazier

Reptiles, amphibians and fishes tend to have a very different reproductive
strategy from that of birds and mammals.

The lower vertebrates generally expend a great deal of energy producing
young, and little or no energy ensuring the survival of the babies.
That is, reptiles, amphibians and fishes produce huge numbers of eggs
(at sometimes severe metabolic detriment to the mother) and are often
not even around when the eggs hatch.

Higher vertebrates, on the other hand concentrate their energies on 
ensuring the survival of the few offspring they produce, spending weeks
to years (or even decades in the case of some humans :) feeding and
protecting their progeny.

Hence it may be reproductively efficient for an alligator to eat some
of her tens to hundreds of children under some circumstances, whereas
it is unlikely for it to be efficient for a mother bear to eat one of
her one or two cubs unless there is a very good reason why she will not
be able to raise the cubs to adulthood (in such a case, for example
a birth defect in the cub, or a season of famine for the mother, the
mother is likely to eat the babies.)

Barbara Chapman               barbara@gang-of-four.stanford.edu