From: russ@wpg.com (Russell Lawrence)
Subject: Re: Closure on Sport Hunting.
Organization: WP Group
Date: Tue, 18 Aug 1992 06:47:01 GMT


Robert Black (I think) wrote:
rb> If wildlife populations could be maintained either naturally without
rb> excessive suffering or with intervention through non-hunting techniques,
rb> what percentage of hunters would voluntarily and willingly forego
rb> hunting entirely?

Jeff Achenbach writes:
ja> Populations maintained naturally without excessive suffering?  
ja> Dream on!  Have you been watching Bambi again?  Mother Nature is 
ja> a cruel, harsh mistress.  The only animal that gives a damn about 
ja> another species suffering is man.  Kill or be killed, eat or be 
ja> eaten, is nature's way.  

Russell Lawrence writes:
rl> Would you mind explaining the role that adipose tissue plays in 
rl> regulating mammalian fertility?  What's the minimum level of body 
rl> fat that a female deer must have in order to ovulate?  
rl>
rl> When the population of a herd reaches the maximum sustainable 
rl> population level, what happens to adipose tissue in females as 
rl> the caloric intake/capita begins to drop, and, what effect would 
rl> this have on additional population growth?  

From article <viking.714108443@vincent1.iastate.edu>, by viking@iastate.edu (Dan Sorenson):
ds> I don't know.  Do you?  If you don't, why didn't you ask
ds> a local zoologist (my girlfriend is a zoologist, and she doesn't
ds> know right off-hand either) or the local DNR agent?  I know that
ds> low bodyfat reduces the chance of fertility in a mammal, but
ds> I've never heard it referred to as a "switch" or anything.

Thanks for admitting that you don't know the answers.  I hope you 
won't mind if I continue asking questions of other readers...  in 
spite of the fact that you're on record as not having any 
pertinent facts available.  :-) 

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

It takes roughly 50,000 to 80,000 calories to bring a fetus to term, 
and roughly 500 to 1,000 calories per day to produce milk.  
Studies show that fertility does, indeed, decline in accordance 
with a decrease in %body fat, and delayed menarche or amenorrhea 
is the likely outcome when % body fat falls below 17 or 
thereabouts, thus inhibiting reproduction altogether.  Above a 
certain point, increases or decreases in 
caloric-intake/fat-content also bring about a corresponding 
increase or decrease in the birth rate of twins.  

[For starters, see Frisch, Rose.  "Fatness and Fertility", 
_Scientific American_, March, 1988.] 

The precise set of mechanisms that allow fat tissue to serve as a 
"switch" doesn't matter for the purpose of our discussion, but 
the fact remains that this mechanism inhibits reproduction when 
food supplies are scarce.  Hence, the argument that mammalian
populations are limited primarily by death [either from starvation or 
predation] appears to be unfounded.   

rl> When the population of a herd reaches the maximum sustainable 
rl> population level, what happens to adipose tissue in females as 
rl> the caloric intake/capita begins to drop, and, what effect would 
rl> this have on additional population growth?  

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

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

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

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