From: russ@wpg.com (Russell Lawrence)
Newsgroups: talk.politics.animals
Subject: Re: Self Regulating Populations
Date: 29 Aug 92 20:51:29 GMT
Organization: WP Group


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?


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