From: russ@wpg.com (Russell Lawrence)
Subject: Re: Self Regulating Populations
Organization: WP Group
Date: Sun, 30 Aug 1992 01:57:02 GMT


In article <BtoAAv.Cpq@wpg.com> russ@wpg.com (Russell Lawrence) writes:
rl> Please take the time to read Frisch, Rose.  "Fatness and Fertility",
rl> _Scientific American_, March, 1988.  I'm looking forward to your
rl> comments.

From article <RIGG.92Aug28122441@osnome.che.wisc.edu>, by rigg@osnome.che.wisc.edu (Tim Rigg):
tr> I read this article and was quite disappointed by what it said and
tr> didn't say.  I was expecting it to explain how the mechanism would
tr> allow populations to control their own population, regardless of
tr> predation.  However, it said nothing of the sort.  ALL it said is that
tr> lower body fat lowers fertility.  That's all...  

Did you miss the part where the author pointed out that lower levels of
adipose tissue will obliterate fertility altogether?

tr> That is a point almost
tr> all have conceded quite a while ago.  What it does NOT say is that the
tr> decrease means a heck of a lot.  In fact, it directly contradicts your
tr> claims.  Please note the following quote:
tr> 
tr> "If undernourished women have fewer children than well-nourished ones
tr> who do not practice contraceptions, why is there such a rapid
tr> population growth in the developing countries?  The paradox is
tr> explained by the fact that the death rate in these countries has been
tr> reduced by mondern public health measures while the birthrate has
tr> remained the same"
tr>
tr> This is exactly the case with deer.  In areas without "handouts and
tr> crops", the fat content will lower the fertility of the herd.
tr> However, by removing predators, we have altered the "death rate".  The
tr> population will explode.

You're grasping at straws.

When you say the population will "explode", are you referring to 
a two-fold increase?  a four-fold increase?  an eight-fold 
increase?  If the fertility has been lowered when the population 
is at 1N, thanks to the impact of diminished caloric intake on 
adipose tissue, it seems to me that it would be pretty tough for 
the deer population to continue to "explode" to 2N, or 4N, or 8N.  
If you disagree, please explain.  

As for human populations in countries with rapidly expanding
populations, would you care to name a locale where you think
population has continued to increase in spite of diminishing
food supplies?  In response, we can explore the mechanisms at
work to see how they do or don't relate to the fatness/fertility
relationship.

On the whole, it's important to remember that the availability 
and distribution of human food supplies is determined by factors 
that are vastly inconsistent among different members of the 
population.  The upshot is that one family may, indeed, be 
starving while another family, sheltered by special legal and 
economic status, may have more than enough food.  Or for that 
matter, a family may have ample food one year, but find 
themselves starving twelve months later when jobs are lost or 
fertilizers are hard to come by or whatever.  

tr> I am disappointed in you Russell.  I think you just kept providing the
tr> source and hoping no one would actually read it.  I read it and I
tr> don't think it supports your claim that populations can regulate
tr> themselves without predation.  Please provides more documentation or
tr> an example to support your assertations, or retract your statements.

Would you be willing to abandon your hunting practices if/when we 
can thoroughly prove that the cessation of hunting would not 
culminate in starvation?  If not, then the issue at stake isn't 
really an argument as far as you're concerned but an "excuse" or
"rationale".  As such, your displays of indignation seem rather 
transparent to me.  

In any case, we disagree.  I think the Frisch article does 
support the notion that populations can regulate without 
predation...  provided, of course, that we're dealing with 
non-migratory animals living in habitats that aren't subjected
to ongoing, destabilizing influences, such as forest management
practices that increase the calories available in summer without 
increasing the calories available in winter.  

I'll be happy to post additional evidence later on to more firmly 
establish the relationship between fat and fertility.   In addition,
I'd like to answer the following questions:

What sort of foods do non-migratory deer typically consume in virgin 
forests during:

   - fall months?
   - winter months?
   - spring months?
   - summer months?

What's the trigger point (%fat tissue) below which any offspring are
likely to be singletons?

What's the trigger point (%fat tissue) below which offspring are unlikely
altogether?

What caloric deficits would non-migratory deer typically encounter
in virgin forests during times of famine (ie winter)?  

What caloric reserves are represented by the differential between
no-body-fat and the body-fat contained at the trigger point determined 
above?

What forest management practices would pro-hunting managers adopt
in order to increase caloric-intake in summer, thereby enhancing 
fertility?   [Partial answers to this question are available in at 
least pro-hunting sources that I've consulted].

What forest management practices would managers opposed to hunting
adopt in order to reduce caloric intake (ie fat-buildup) in the 
pre-mating season without increasing caloric deficits in the winter 
months?  

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