From: achenbac@epcot.spdc.ti.com (Jeff Achenbach)
Subject: Re: Self Regulating Populations
Organization: TI Semiconductor Process and Design Center
Date: Mon, 31 Aug 1992 18:57:42 GMT

In article <BtrJ9w.L0@wpg.com> russ@wpg.com (Russell Lawrence) writes:
>
>Jeff Achenbach writes:
>ja> Just a guess, but it would seem more likely that population density, not 
>ja> population per se, is the important variable. Diseases with only human 
>ja> vectors for transmission will obviously spread faster when interactions
>ja> are more frequent.
>
>Russell Lawrence writes:
>rl> I don't doubt that deer are social animals, and that they either seek 
>rl> out contact with one another or avoid contact with one another in 
>rl> accordance with their needs.  Is there any evidence to suggest 
>rl> that the number of contacts/capita is diminished when the 
>rl> population is indiscriminantly culled?   If not, why would we 
>rl> believe the claim that indiscriminant and discriminant culling
>rl> are both equally effective in reducing disease?
>
>From article <1992Aug28.155635.8819@spdc.ti.com>, by achenbac@epcot.spdc.ti.com (Jeff Achenbach):
>ja> If contacts/capita remain constant, then you are saying population 
>ja> density is unchanged, are you not?
>
>Nope.  I'm saying that deer don't simply bump into one another the
>way mindless billiard balls bump into one another on pool tables.  
>The assumption that reducing population is going to magically reduce
>the social contacts that transmit disease ignores the fact that deer
>are social animals that seek out their own contacts.   Again, the
>notion that indiscriminant and discriminant culling serve the same
>purpose just doesn't make much sense.
>
>rl> As a long-distance, television observer, how can you tell whether the
>rl> prey animals you're observing are sick or healthy?   
>
>ja> Through many first hand observations in the wild.  A sick rabbit 
>ja> can't run as long and fast as a healthy one.  I have seen both, 
>ja> but admittedly few sick ones.  I presume you have seen many of 
>ja> the same type of wildlife shows as I.  Are you seriously saying 
>ja> you can't tell a starving, sick animal from a healthy one in a 
>ja> good quality TV image?  
>
>I'm sure that we can identify extremely ill animals from the 
>comfort of our living rooms, especially if they're falling over 
>or staggering around, but the fact that an animal may look 
>healthy and fit to long-distance human eyes doesn't mean that it 
>is, indeed, healthy and fit.  
>
>ja> Most prey species reproduce at a higher rate than predators. When prey 
>ja> animal populations drop, a drop in predator density 
>ja> follows.  Whether adipose tissue or starvation is responsible, 
>ja> I don't know, but if prey population density (including but 
>ja> not exclusively deer) gets sufficiently low that caloric 
>ja> expenditures to capture it exceed the caloric benefit of 
>ja> eating it, predators must relocate, alter their diet, or die.  
>
>rl> How many fawns does a doe typically produce (at most)?  How many
>rl> pups does a female wolf produce at most?   [End of theory]
>
>ja> Deer are only one prey species.  How many rabbits to the litter?  
>ja> How many pheasants, ducks, quail, grouse, woodcock, to the 
>ja> clutch.  How many litters of rodents and of what size are born in 
>ja> a year?  Sorry I didn't make myself more clear.  The species 
>ja> under discussion has been deer, but the predator with the lead 
>ja> role in said discussion has been predominantly canines.  By prey 
>ja> species, I meant prey in aggregate.  
>
>Personally, I try to avoid absolutist theories whenever possible.  Did
>the comparison between wolf reproduction and deer reproduction prompt
>you to rethink your theory, at least so far as deer and wolves are
>concerned?
>

I don't think so. I'm not sure how these two got tied so closely together. 
Although they certainly do interact, there are far more complexities in the
wild to ever hope to cover all possibilities in this medium, even if we knew
them. I don't think anyone ever stated that a wolf's only source of food was
deer, but it was brought up as the main wild predator using deer. I agree with
trying to avoid absolutist theories. Most of them are absolutely wrong.
However, simplistic ones in a complex relationship can be just as bad. In a 
forum such as this, where I for instance get to read and answer questions in 
between performing functions for which I am paid, it is not easy to cover all
bases. I try to be as clear as possible in my statements and arguments, but
some assumptions are always made in human discourse. For instance, I assumed 
anyone who would argue the relationship between wolves and deer would have at
least some basic knowledge of wolves and would realize that wolves do not 
live by deer alone. I'll keep trying to make myself clear and clarify as 
requested when I fail, but I will assume I don't have to state every known fact
to make a point.

Jeff Achenbach
achenbac@epcot.spdc.ti.com