From: russ@wpg.com (Russell Lawrence)
Subject: Re: Self Regulating Populations
Organization: WP Group
Date: Tue, 1 Sep 1992 20:40:03 GMT


Tim Rigg writes:
tr> Ask Rose Frisch.  She specifically states that "poor couples in
tr> developing countries" are not infertile.  They only had 6 or 7 living
tr> births which is well below the human capacity.  6 or 7 children is
tr> hardly infertile.

Russell Lawrence writes:
rl> Were you assuming that poor people necessarily have low-calorie 
rl> diets?

From article <RIGG.92Sep1133600@osnome.che.wisc.edu>, by rigg@osnome.che.wisc.edu (Tim Rigg):
tr> No, I was reading the article (perhaps you should give it a try).  A
tr> few lines above my quote, it says 
tr> 
tr> "For instance, data on growth and reproduction of women in Great
tr> Britain in the mid-1800's show that poorly nourished females, who grew
tr> to maturity relatively slowly (a patern that results in less fat per
tr> unit of lean mass), differed from well-nourished females in each event
tr> of reproductive span. ...[lists events] In that British population, as
tr> in many other populations, poor couples still living together at the
tr> end of their reproductive lives had only six or seven living births.
tr> Most poor people in developing countries have about that number..."

You're still assuming that poor people necessarily have low calorie
diets.  Let me explain it to you:  The fact that low calorie diets
reduce the fertility of poor people doesn't mean that poor people
necessarily have low calorie diets.  Think about it.  

rl> The ability to survive through winter would depend on the differential
rl> between the available caloric intake and the energy stored in surplus 
rl> fat.  It seems to me that this will vary from region to region, but
rl> it would clearly be amenable to game management policies.

tr> This our point of disagreement.  Please read that again.  We agree
tr> that lower fat content will lower fertility, even shut it off if it
tr> gets low enough.  We disagree that a stable population of wild game
tr> could be maintained by such a mechanism.

Fair enough.  I propose that we table the discussion until my list of 
citations is more complete.  [I'll continue to address claims made
by other posters that fertility and fat are unrelated]

rl> I don't see why you think that research is necessary to answer 
rl> this question.  If a given habitat produces sufficient calories 
rl> to meet the caloric requirements for 1N animals plus an offset 
rl> that's barely sufficient to assure fertility, how/why could the 
rl> population continue to "explode" as it progresses to 2N or 4N?  

tr> In the base case, the deer consume 5000N calories.  How many calories
tr> will be consumed by xN deer?

rl> Why are you avoiding my question?

tr> Because natural food supplies are much more complicated that a 
tr> trough of 5000N calories.  You would have realized that if you 
tr> wouldn't have avoided _my_ question.  

I learned that calories aren't found in "troughs" years ago while 
doing survival stints.  That's why I reject the notion that 
surplus calories suddenly disappear when the brush line is six 
feet high.  The fact remains that fertility will decline as 
surplus calories decline.  Moreover, the best sources of surplus 
calories are the ones that either disappear the quickest, or 
conversely, tend to remain available in winter (seeds and nuts).  
The poorest sources of surplus calories (leaves, twigs, etc) are
the ones that last the longest and are far more abundant ---
provided, of course, that the deer don't have access to human
crops.

-- 
Russell Lawrence, WP Group, New Orleans (504) 443-5000
russ@wpg.com   uunet!wpg!russ
Newsgroups: talk.politics.animals