From: robinson@ac.dal.ca
Newsgroups: talk.politics.animals
Subject: Re: New Subscriber and a look on hunting
Date: 8 Apr 92 19:17:18 GMT
Organization: Dalhousie University, Halifax, Nova Scotia, Canada

In article <=!1thfd@rpi.edu>, schwae@marcus.its.rpi.edu (Eric A. Schwartz) writes:
> In article <72729@netnews.upenn.edu> barkdoll@cattell.psych.upenn.edu (Edwin Barkdoll) writes:
>>In article <1992Mar31.154717.4678@ac.dal.ca> robinson@ac.dal.ca writes:
>>>Pop quiz:  how many deer, expressed as a percentage of total 
>>>population, need to die in a given year for the population to remain about 
>>>the same?
>>
>>	The question has little relevance to reality: The proportion
>>of population wich must die to maintain a constant popoulation depends
>>on many things not the least of which is what population level is
>>desired, what the growth rate is...!  Are you saying that there is one
>>and only one percentage which if removed from any deer population will
>>result in a constant population?
>>
> Sorry I forgot to answer this one.  The total rate of death must
> equal the total rate of birth.  Given 50% does, and 2 fawns per doe,
> and guessing that 10% die of old age yearly, that gives the rate of
> unnatural death at about 40%.  How much of that should be by hunting
> would require more info than you have given.  What is the rate of
> injury resulting in inability to survive the winter, the rate of
> death due to disease or starvation, or numerous other things I can't
> even think of?  I'm not a population biologist.   

40%, yes.  I didn't say how many had to die as a result of hunting, just 
how many had to die.  That number gets more critical as the herd approaches 
the carrying capacity of its range, as the N.S. herd did a few years ago.  
One year we were allowed to take up to two deer of either sex.  The 
population has since declined somewhat, in part because not enough people 
(including yours truly) took a second deer.

Factors that are considered, in no particular order are:

Auto deaths - often quite high.  Police reports usually provide good data 
on the number of such deaths and therefore this is a fairly solid number.

Winter kill - includes starvation, disease etc as this is when adults tend 
to be most vulnerable.  Usually estimated by a pre-winter and post winter 
census of certain areas.  If done properly it can be surprisingly accurate.

Fawn mortality - can be as high as 50% of births in a bad year.  Done by 
same technique as above, but probably somewhat less accurate as fawns hide 
very well. (most such census' are done from the air here I belive)

Deaths by non human predators - coyotes, lions etc.  Very difficult to 
estimate with any great accuracy.  Depends on many factors, not the least 
of which is predator population.

Poaching - Illegal hunting activities are generally believed to account for 
a large number of fatalities.  Obviously, it is impossible to estimate 
exactly how many animals are taken this way.  

Hunting - The above factors usually provide an estimate of the number of 
deer that need to be eliminated prior to winter to minimize the winter 
kill.  As I understand it, the number of licenses issued somewhat exceeds 
this depending on the historical data wrt the success ratio.  Mandatory 
kill registration programs (like that here in this province) allow 
biologists to get hard data on the actual number killed vs. the number of 
tags issued and therefore they can more accurately regulate numbers.


Notice that the total from the above should ideally comprise roughly 40% of 
the population.  Old age is not included here because it was taken into 
account as per Eric's statements above.

Also, you should be aware of the fact that hunting generally makes up a 
relatively small fraction of the total mortality.  Its key importance lies 
in its timing (i.e. just before winter, when food will be scarce and 
overpopulation can mean a serious long term reduction in the carrying 
capacity of the range), and its relative precision (i.e. based on 
historical data it is often possible to estimate the kill quite closely).

I'm not a wildlife biologist.  Just a hunter with an enquiring mind.

> 
> E.S.
-- 
John Robinson                  Only criminals, tyrants, and cowards have
robinson@ac.dal.ca                 reason to fear the armed, honest citizen.
DOD #0069
Newsgroups: talk.politics.animals