I used data on the Minnesota wolf population and its increase rate (Fuller et al. 1992; Berg and Benson 1999), statistics on wolf depredations on livestock and dogs, costs of the U.S. Department of Agriculture Wolf Depredation Control Program, and of the Minnesota Department of Agriculture compensation payments (Table 1, Table 2) to calculate annual per-wolf costs of these programs for 3 periods: 1979-1989, 1989-1998, and 2001-2005. Costs that I considered included monetary outlays as well as social costs in terms of numbers of farms affected, number of dogs killed by wolves, and number of wolves destroyed. Dog losses were considered because pet loss is especially disturbing to humans (Fritts and Paul 1989), and wolves destroyed were considered because they are important to animal rights advocates.
For the first 2 periods, I calculated the mean number of wolves in Minnesota per year assuming a mean annual increase of 5% (Berg and Benson 1999). I also calculated annual averages for the number of depredations and the depredation costs. For the first period, I divided the annual costs by the average number of wolves. For the second period, I subtracted the mean annual number of wolves during 1979-1989 from the mean number during 1990-1998 to yield the mean annual number of wolves over that of the first period. I referred to these wolves as "extra" because they were the number above that recommended by the Recovery Team.
I also subtracted the annual means of depredation control and compensation costs for the first period from those for the second period. Dividing the results by the mean difference in number of wolves for the 2 periods yielded a mean cost per wolf for the extra wolves.
Because wolves had saturated the wilderness and semi-wilderness areas and had begun to spread into agricultural land by 1989 (Fuller et al. 1992), I assumed that the depredation-control cost data from 1990 to 1998 would constitute a reasonable basis for projecting the future costs of wolves colonizing additional agricultural regions. Similarly, I assumed that the number of farms where wolf depredations were verified, the number of dogs killed by wolves, the amount of compensation, and the number of wolves killed by controllers would also continue to increase at the same rate.
Thus I used simple linear regression of 1990-1998 data to determine trends for these factors and projected these trends (95% CL) for the third period, 2001-2005. I chose the years 2001-2005 because that is the best estimate of the period when Minnesota will have regained management responsibility while continuing to allow the wolf population to expand. I then averaged the projected costs per year for 2001-2005.
I also projected that the wolf population trend would continue to increase at an average annual rate of 5% per year, the rate of increase for both the previous periods. I then calculated the mean number of wolves per year during 2001-2005.
I subtracted the mean annual number of wolves for the first period from this number to yield the mean annual number of extra wolves for 2001-2005. I subtracted the mean annual costs for the first period from the projected mean annual costs. I then divided the difference in mean annual costs by the mean annual extra wolves to derive a mean annual cost per extra wolf.
Because the Minnesota State Legislature increased the maximum compensation payment per animal killed by wolves from $400 to $750, an increase of 87.5%, I multiplied all compensation figures for the third period by 1.875 (although this approach does not yield a completely accurate measure of the total increase in compensation payments, it is the best approximation that can be made without knowing precisely how many of each kind of livestock will be killed). I similarly adjusted the mean annual cost for the first period before subtracting from the projected costs, because this cost represents the cost for maintaining the basic number of wolves in the wilderness and semi-wilderness and thus would also increase. I did not consider inflation in any calculation because it is not considered in the payments except as the legislature changes the payment rate.
To estimate the number of wolves it would be necessary to kill annually for depredation control at various population levels, I performed a regression analysis using the 1990-1998 depredation-control take as the dependent variable and the estimated annual populations, assuming a mean annual increase of 5% (Benson and Berg 1999) as the independent variable. Then, I projected the regression line.
Table 2. Number of wolves and overall costs of maintaining the wolf population in Minnesota for 3 periods during 1979-2005.
Factors
examined
Periods
1979-1989
(annual 
)1998
Projected
2005
Wolf population
1,438a
2,520b
3,546b
Farms affected
27
99
94-171c
Wolves killed
36
161
109-438d
Dogs killed by wolves
3
25
8-52e
Compensation payments ($)
25,209
50,000
75,002-182,074f
Control costs ($)
77,000
255,000
245,060-512,610g
Total costs ($)
102,209
301,413
320,062-694,684
a
Based on 3% mean annual increase (Fuller et al.
1992).
b
Based on 5% mean annual increase, 1989-1997 (Berg and
Benson 1999).
c
Projection of linear regression of 1990-1998 data (r2=0.48;
P=0.04).
d
Projection of linear regression of 1990-1998 data (r2=0.77;
P< 0.01).
e
Projection of linear regression of 1990-1998 data,
with 1990 removed as outlier; (r2=0.053;
P=0.04).
f
Projection of linear regression of 1990-1997 data
with 1990 removed as outlier (r2=0.70;
P= 0.02).
g
Projection of linear regression of 1990-1998 data (r2=0.72;
P< 0.01)
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