From: russ@wpg.com (Russell Lawrence)
Subject: Re: Closure on Sport Hunting.
Organization: WP Group
Date: Sat, 22 Aug 1992 06:41:27 GMT

ds> [loads deleted -- we agree on the large scope, and you've read it before]

From article <viking.714445675@vincent1.iastate.edu>, by viking@iastate.edu (Dan Sorenson):
ds> Still, those seasonal fluxuations may still prove to allow only a 
ds> bit above "enough" in the summer and not enough for everybody in 
ds> the winter.  I'd say the habitat is the biggest factor here, and 
ds> I also claim that starvation is one method nature uses to control 
ds> the population depending on that habitat, which will show up in 
ds> those data points that fluxuate all over the graph.  

We seem to be nearing agreement.  I'm going to make a few more 
points, and then I'm going to once again suggest that we make an 
effort to find real data that would enable us to plot some 
meaningful curves.  Otherwise, we'll just end up spewing hot air 
instead of raising our level of understanding.  

As far as habitat goes, the question that we must ask is whether or
not it's stable.   It doesn't matter whether the area typically has
lots of food or very little food, since the concept of over-population 
is measured by calories/capita and not by the abstract measurement of
animals/hectare.  If the area is a desert, the population may be small
indeed; if it's a lush jungle, it may be loaded with animals.  In 
both cases, the level of body fat will determine fertility, and hence,
stabilize the population to suit the available food.

If we were plotting calories/capita on a one year graph with 365 
ticks, it would be tempting to assume that winter is a time of 
radical instability.  Yet, "nature" anticipates this particular
kind of instability in a big way, and has endowed us with a 
number of compensating features and abilities.

First, there's some food available...  even in winter.  An animal 
might need to dig through snow or reach into branches, and it may 
not be as tasty or abundant as the stuff one might find in 
summer, but it's there nonetheless.  Caloric intake doesn't 
simply drop to zero.  Second, nature has endowed both mammals and 
birds with reserves (aka fat) to carry them through hard times;  
this fat can supply, not only energy, but fat-soluble nutrients 
as well.  [It also carries fat-soluble toxins, but that's another 
story].  These fat reserves are _not_ inconsequential.  A 200 
pound animal with 15% body fat would be carrying a caloric 
reserve amounting to nearly 123,000 calories!  Third, most 
mammals (perhap all mammals) have the ability to lower their 
metabolism to an amazing degree when food supplies are at their 
lowest.  As metabolism drops, 123,000 calories can last quite a 
long time. 

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> I am rather busy at the moment (I've gotta get a faster modem --
ds> I refuse to break my addiction to Usenet), but I don't see where the
ds> caloric expenditures are relevant unless one knows exactly how many
ds> calories the habitat can provide per critter.  Since this cannot be
ds> known with any degree of accurracy outside of a small field or where
ds> crops are grown, I'd say we've got a problem.  

Again, it isn't total caloric yield that matters, but unnatural
fluctuations in the caloric yield.  You can see this clearly in
human habitats.  Bedouin, for example, used to live in areas that
were relatively barren compared with the kikuyu, who lived in
areas that were quite lush.  Yet both people would fare quite nicely
in the absence of such cataclysms as war.

ds> A far easier method
ds> of ascertaining the caliroc intake/capita is to put a certain number
ds> of critters in an exclosed area and then observe their bodyfat and/or
ds> possibly weigh them occassionally.  This data I have on bovines,
ds> and I've posted it before.  In brief, everybody is happy and fat for
ds> a few weeks, then the next week we see shrinkage of the animal, and
ds> within the next two weeks there's nothing edible left.  This was with
ds> about 50 cows on roughly 300 acres of corn stalks (with some corn
ds> unharvested due to a seriously wet fall, but this was less than half
ds> an acre in size and disappeared really quickly).  After week number
ds> three we started supplimenting their feed with silage and stacks of
ds> corn stalks, and finally hay.  Still, as time went on we had to
ds> switch to higher-calorie foods and more of it to keep the herd at
ds> the same (or similar) bodyfat.  I'd say the extrapolation of this
ds> data just shows that unless the habitat is incapable of providing
ds> less than what the herd needs, it will have its limits pushed, and
ds> that pushing may result in fewer births or starvation depending
ds> upon the number of other deaths in the herd and the time frame
ds> during which the habitat is depleted.

I don't think you can extrapolate from captive cows for several reasons:

1) their diets are far, far higher in protein and fat than the diets
   of wild deer.  
2) they're largely sedentary which increases their ability to store
   fat while decreasing their ability to effectively use the fat in
   time of famine.
3) it seems unreasonable to measure the level of "starvation" 
   in an animal by the palatability of its flesh.

I'm going to go ahead and make plans to carry out this research.  If
you want to participate, that's fine.  If not, that's fine too.


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