Gray wolves (Canis lupus) in upper Michigan, USA, have been monitored since 1991 when breeding activity in mainland Michigan was documented for the first time since 1954. Based on winter track counts, the mean annual rate of increase in abundance was 19% from 1995 to 2002, with the population reaching an estimated 278 animals in 2002. Our objectives were to (1) increase the efficiency of wolf management in Michigan by evaluating alternative and less extensive sampling approaches for population estimation, and (2) evaluate habitat for wolves based on occupancy after a decade of recovery. For the first analysis, we created 22 discrete sampling units that cover upper Michigan, and we evaluated abundance estimates based on various sampling plans using known distribution and populations from the 2000–2002 winter track surveys. We evaluated each plan based on the precision, bias, and confidence interval coverage. A random sampling plan with regression estimator returned the most precise estimates, but a stratified sampling plan, using low, medium, and high wolf density strata had the greatest precision at lowest effort. For the habitat evaluation, we compared white-tailed (Odocoileus virginianus) deer density and road density between wolf pack locations from 1995 to 2001 to random locations outside of the current wolf range. We estimated white-tailed deer density by a spatial interpolation of pellet group counts. Our resource selection function indicated that probability of wolf occupation of an area was positively correlated with deer density, and it was relatively constant for road densities <0.4 km/km2 but declined sharply at higher road densities. For areas habitable by wolves in upper Michigan, we predict a road density threshold of 0.7 km/km2 and a deer density threshold of approximately 2.3–5.8 deer/km2. We believe that these results will aid managers who need to estimate wolf abundance and predict wolf distribution.
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Vol. 69 • No. 4