From: viking@iastate.edu (Dan Sorenson)
Subject: Re: Hunting-Fat-Fertility. Was: Letter to John Robinson
Organization: Iowa State University, Ames IA
Date: Tue, 28 Jul 1992 06:29:32 GMT

In <Bs1CA4.nI@wpg.com> russ@wpg.com (Russell Lawrence) writes:

>From article <dwxx8vc@rpi.edu>, by vanetten@unix.cie.rpi.edu (John S. Van Etten):
>jve> However, I would say that in general, *today* hunting is only 
>jve> allowed in those areas and on those species where populations 
>jve> require it. 

>Proof?

	Self-interest.  If it's a game population, the hunters are foolish
to hunt it to extinction.  If it's not, it usually has some sort of relation-
ship to game species, and hence the ecological-types and the DNR have little
reason to advocate extermination over existence.  The passenger pigeon will
not happen today thanks to these people, and to hunters willing to spend a
season without hunting if necessary.  It's selfishness, Russ, that most
primal of human reasons.

>jve> Animals have a habit of increasing their populations to over the 
>jve> maximum that can be supported by the food supply and then going 
>jve> over and over through the viscious starvation cycle.  We've 
>jve> discussed that before.  

>How much do you know about the hormonal mechanisms that control 
>mammalian reproductive cycles?  Specifically, what effect does 
>adipose tissue have on the onset of estrus?  And, what percentage
>of body fat must a female deer have in order to ovulate?   Perhaps
>you don't know the precise figures, but I'm sure you'll agree that
>they're well-above the starvation point.  This would lead me to 
>believe that mammalian populations are self-limiting in stable, 
>natural environments, and therefore, it may not be entirely 
>accurate to say that non-human mammals would inevitably starve
>without human intervention.

	I'm a enginerd, not a zoologist or biologist, but I'll take a
stab at this: Let's say a female deer needs 20% body fat to ovulate.
Fine.  Hogs can lose 7% weight in a half hour, from 120lbs to 110lbs,
during a single ride in a truck.  This is due simply to stress.  They
can put that weight back on in a single afternoon.  Humans have a hard
time with weight fluxuations like that.  Let's assume it's mostly body
fat that is being lost and gained.  If ovulation happens at >20% body
fat, then it only takes two days of poor feed to negate this effect.
Let's get crazy and assume the deer are hardy enough to take a week of
no food to go from >20% to <20%; let's also assume that there is an
entire herd at work.  What you will have is several deer in estrus over
a month or so, and during that time the food supply can change rather
drastically without outside intervention.  Thus, let's say half the deer
ovulate and bear fawns.  That's still only half of the 100% rate, due
only to a few weeks of poor feed.

	Nature does indeed tend to keep populations in check this way,
but corn fields and hay bales are not to be found in nature.  Deer have
a food supply created by human awareness of the future and hence human
stockpiling, and this, coupled with reduced predators, leads to a
breakdown of the system you illustrate above.  I'm not saying it won't
work, mind you, but that it's effects are moderated by the quick
transition from plenty to scarcity of natural foods, and the moderating
effects of man-made food supplies.  In short, we've messed it up, and are
unwilling to live with a 20-deer herd that will become 1000 in five years
because we prefer 4000 constant animals.  We control their populations
through hunting, not food supply as nature does.  While I think it might
be more humane for the deer, I also think that our leaving this loop
would result in some serious die-off's in the herd.  We're a moderating
influence, both for the good and the bad.  It is an individual judgement
if the good outweighs the bad in this case.

	So, Russ, how'd I do?

<Dan Sorenson, DoD #1066 |"There'll be angels on Ariels in leather>
<z1dan@exnet.iastate.edu | and chrome, Ridin' down from heaven    >
<viking@iastate.edu      | just to carry me home." -- R. Thompson >
< ISU thinks I need more education, which they provide for a fee. >

Newsgroups: talk.politics.animals