From: russ@wpg.com (Russell Lawrence)
Subject: Re: Closure on Sport Hunting.
Organization: WP Group
Date: Sun, 23 Aug 1992 08:53:11 GMT


In <BtDH94.5LE@wpg.com> russ@wpg.com (Russell Lawrence) writes:
rl> These fat reserves are _not_ inconsequential.  A 200 
rl> pound animal with 15% body fat would be carrying a caloric 
rl> reserve amounting to nearly 123,000 calories!  Third, most 
rl> mammals (perhap all mammals) have the ability to lower their 
rl> metabolism to an amazing degree when food supplies are at their 
rl> lowest.  As metabolism drops, 123,000 calories can last quite a 
rl> long time. 

From article <viking.714537991@vincent1.iastate.edu>, by viking@iastate.edu (Dan Sorenson):
ds> How long is the big question.  Is it long enough to survive?

I think we'll be able to answer these questions conclusively after 
we do some additional research.  As I mentioned previously, every 
pound of fat carries roughly 4100 calories, and as caloric-intake 
drops, metabolism also drops as the body begins to conserve 
energy.  Hibernation is an extreme case, but a similar phenomenon
occurs in mammals that do not hibernate.  

Again, human dieters provide perfect examples.  They lower their 
caloric intake from, say 4,000 calories to 1,500 calories and 
they lose weight for a few days or perhaps for a few weeks.  
Before too long, however, they become lethargic and thereafter, 
weight losses no longer occur or perhaps occur more gradually.  
To continue losing weight, dieting humans have to further cut 
their energy intake or force themselves to exercise.  The 
apparent tenacity with which humans maintain fat tissue 
demonstrates how effective our energy reserves would truly be if 
we were living in primitive conditions in temperate climates, as 
animals in nature must do.  

The upshot is that 15% body fat would go a long way in 
supplementing the reduced caloric intakes that are natural in 
winter.   In view of the fact that females consistently have higher
% body fat than females, it seems likely that the fertility
"switch" probably accomodates the requirements of winter fasting
as well as pre-natal development.

I suspect, btw, that there are two "switches".  A given % body 
fat might make it possible to produce singletons whereas a higher 
% would tend to produce twin fawns.  This would account for the 
observation that the highest percentages of twin births typically 
occur in "acorn" years.  

ds> In addition, we need to be worried about the times of plenty being
ds> plentiful enough to allow building up those fat reserves.

Absolutely, but here again, it's important to remember that the 
fertility 'switch' typically occurs at % body fat levels that are 
significantly higher than the % body fat levels normally expected 
in males living under the same conditions.  What this means is 
that a female, to be fertile, must store quite a bit more fat 
than males.  If the habitat makes this difficult, the population 
will decline as a consequence of lower birthrate and old age...  
even if disease and predators were nonexistent in the area.  

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

ds> More is needed.  Not only the calories available, but how
ds> easily available (spending 600 calories to forage for 601 is what
ds> I'm after discovering here).  Plus, how much of what's available in
ds> the summer is going to actually be injested?  Lush, tall grass that
ds> is ignored by the deer should also be ignored by the research.  After
ds> all, I wouldn't count the calories at the meat counter against how
ds> much it takes you keep you healthy. ;-)

I'm not sure that I understand your point.

rl> Again, it isn't total caloric yield that matters, but unnatural
rl> fluctuations in the caloric yield.

ds> But we still have to find caloric yield, which it seems will be
ds> a problem to do with any degree of accurracy.  How many caliries a deer
ds> needs is easy, but how many he can find is hard.

Not entirely.  I can think of several methods that we could use
if we were engaged in primary research.  The stupid, simple-minded
way would be to conduct invasive studies by marking several hundred
deer and then killing them at intervals to measure declining body
fat as well as the contents of their gi tracts.  A series of concealed
observation posts in a controlled range would serve the purpose just
as well, although it would require more man-hours.  An added bonus of
such a method would be the information that such a study would provide on 
levels of activity.  

I suspect, however, that we won't need this kind of ambition.  I'm
sure we can get ample info from existing data.

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