From: russ@wpg.com (Russell Lawrence)
Subject: Re: Closure on Sport Hunting.
Organization: WP Group
Date: Fri, 21 Aug 1992 21:19:52 GMT


Russell Lawrence writes:
rl> Fat tissue is a switch, Dan.  Did you ever wonder why the average 
rl> fit male human has roughly 10% body fat, whereas a healthy woman's body 
rl> fat might run around 25%?  In the average american woman, this added fat
rl> carries an energy surplus of roughly 144,000 calories.   Now what purpose
rl> do you think this energy surplus might serve?  

From article <viking.714173927@vincent1.iastate.edu>, by viking@iastate.edu (Dan Sorenson):
ds> We've already discussed this part, and I agree with all of it.
ds> However, the switch part I disagree with because it implies a binary
ds> condition.  It won't work that way.  One deer will be fertile at 20%,
ds> another will be infertile at 30% due to individual differences.  And,
ds> one cannot hope that it works in all cases at all times.  If it did
ds> work so well, there would never be a starving fawn.  It happens.

I wholeheartedly agree that individual differences probably exist between
different members of a population.  However, I suspect that the vast
majority of starving infants stem from unstable enviromental conditions.

My local park, for example, is an official Louisiana wildlife refuge 
in spite of the fact that it's in the middle of a major city and is
surrounded by homes and businesses on all sides.   And this park is
the home of literally hundreds of ducks... far more ducks than the
terrain could naturally support.  Every day in the spring, summer, and
fall, hordes of humans show up with cornmeal and stale bread and
feed those ducks to the bursting point.  When winter rolls around and
the weather is rainy and "cold" (by Louisiana standards), the people
stay away and the ducks face the very real threat of starvation.  The
ponds and mock-marshlands in the park simply don't produce enough
food to sustain the large population.  The irony is that the weather
gets warm well in advance of the nesting season, and the ducks 
subsequently get fat from handouts and lay lots of eggs, which the 
park officials unofficially destroy. 

> ...
ds> It would lower population growth for one season, at which
ds> time the present herd population has decreased due to starvation.

rl> Why would you make such an assumption?  If lower fat content 
rl> reduces fertility, hence reducing birth rate, don't you think
rl> diminishing food supplies would _decrease_ the herd size and 
rl> thereby reduce the threat of starvation?  

ds> Yes, they will.  What sort of time frame are we talking about 
ds> here?  The lack of dampening in this process is what gives us the 
ds> growth->starve->growth->starve cycle we know so well.  Since 
ds> neither population nor food supplies are constant over a month, 
ds> let alone a year, I'd say the factors we mention don't work 
ds> incredibly well in the short term.  Over several years, they will 
ds> serve to keep the average where it should be, but the data points 
ds> will fluxuate quite a bit.  

Sure they'll fluctuate, but it's important to remember that the 
seasonal fluctuation in available food calories, in itself, wouldn't
doom animals to starvation.   Most mammals, perhaps all mammals,
can accomodate seasonal fluctuations with ease.  Humans, for example,
might enjoy an intake of 5,000 calories per day in times of "fat",
but easily endure an intake of 1,000 calories for several months
on end (ie winter) without running the risk of true starvation.

ds> In addition, there will be some young born as the time of conception
ds> may have been when food was plentiful, and caloric intake/capita
ds> need not drop in a gentle curve depending on the area the herd
ds> has to forage in. 

rl> After you expand this idea, I'll be happy to reply.

ds> I think I mentioned it once before, so how do you wish for
ds> me to proceed in expanding this idea?  The gestation period in most
ds> mammals is long enough that the available food could diminish quite a
ds> bit between conception and birth.  Thus, you could have fawns born in
ds> the midst of a famine despite the inherent switch we mention above.
ds> In addition, you could have a drought that decreases the population
ds> and then followed by some good rains and plenty of food with little
ds> remaining population.  It will work both ways, and it is not
ds> particularly responsive for the short term.

I think both of us should do some more research to get a better idea
of the food calories available in normal deer "food", and then try to 
get a better grip on caloric expenditures on a season-by-season basis.   

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