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Do Wolves Affect White-Tailed Buck Harvest
In Northeastern Minnesota?

Results


From 1975 through 1997, we counted 4-6 wolf packs that were dependent on deer in our census area, and their numbers ranged from 2 to 14 per pack each winter (Mech 1986, and L. D. Mech, U.S. Geological Survey, unpublished data). Annual buck harvest varied from 28 to 97 for the Isabella kill block, and 5 to 111 for the Ely kill block (Table 1). Total buck harvest for the zones west of our wolf census area varied from 200 to 930 each year (Table 1).

We found no significant relationship between any of our individual wolf pack sizes and either the Isabella or Ely buck harvest over the entire 23-year period, even though some of the wolf packs inhabited those kill blocks. The total number of wolves from all packs showed a marginally significant (P = 0.08) inverse relationship (r2 = 0.14) with the Isabella buck harvest (Table 2).

Upon inspecting the scatter plots of the regressions, we noticed an apparent outlier in one of the plots. Although we knew of no reason to remove the outlier from the analysis, we did so arbitrarily to see how much this maneuver would force the data to fit our hypothesis. The result was an increase to an r2 of 0.22 for the total of the wolf packs on a deer economy versus the Isabella buck kill (Table 2).

Plotting annual total wolf numbers against Isabella buck harvest from 1975 to 1997 showed no lag effect (Fig. 2). In fact, from 1975 through 1984, the wolf population tracked the decreasing deer harvest but continued downward through 1991 after deer harvest increased. Wolf numbers then increased again.

Annual decreases or increases of ≥5 each of wolves and deer were inversely related in only 9 (41%) of the 22 years. Inverse relationships occurred in 7 other years but in those years the increase or decrease for one species was < 5 animals. In the remaining 6 years, wolves and deer increased or decreased similarly in 5 years, and in one year the largest decrease (n = 25) in the wolf population (from 1989 to 1990) was followed by no change in the buck harvest. Among all years, the greatest decrease in the buck harvest (from 1992 to 1993) was preceded by only a small wolf increase, and large increases in buck harvest (from 1979 to 1980 and 1984 to 1985) were preceded by wolf increases.

From 1988 to 1995 when hunting pressure was deemed relatively constant, we found inverse relationships (r2 = 0.36-0.48) between size of individual wolf packs and buck harvest, and between the Ely buck kill and the wolves in the Ely-buck-kill area (r2 = 0.66; Table 3). The strongest relationship was between the total population of wolves in all our deer-killing packs and the harvest of bucks in the Ely area (r2 = 0.84, P = 0.001). Nevertheless, we found no relationships between total population of deer-killing wolves and either the combination of Ely and Isabella buck harvest or size of buck harvest from adjacent areas (Table 3).


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