1 September 2004 Effects of wildfire on black bear demographics in central Arizona
Stan C. Cunningham, Warren B. Ballard
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Little is known about the effects of wildfire on black bears (Ursus americanus). Following a wildfire in Arizona, we hypothesized that the local black bear population would decline due to direct mortality or reductions in food and cover. We also hypothesized that remaining bears would have larger home ranges than bears in unburned areas because of decreased food resources and cover. To test our hypotheses, we studied short-term effects of a wildfire on black bear demographics in the Mazatzal Mountains, central Arizona, from 1997–2000 and compared these parameters to those in an unburned area. We also compared density estimates, survival, cub production and survival, and home-range sizes in the same area prefire (1973–1978) to postfire (1997–2000). We captured 31 adult bears within the burn perimeter on Four Peaks and 15 on unburned Mt. Ord during 1997–2000. Adult sex ratio within the burn perimeter on Four Peaks was more skewed toward males (4 M:1 F) than in the unburned area on Mt. Ord (1.7 M:1 F), or the same area prefire (1.4 M: 1 F). Subadults comprised 20% of captured bears in both study areas. The largest apparent impact of the wildfire was lack of recruitment of cubs to the yearling age class. Five adult females produced 16 cubs within the burn perimeter on Four Peaks during 1997-1999, but none survived to 1 year of age. Four females in the unburned area produced 13 cubs, and 36% survived to 1 year of age; in a prefire study, 48% of cubs survived to 1 year on Four Peaks. Hunting was the greatest cause of adult mortality in both areas. Estimated black bear superpopulation size within the burn ranged from 27–36; a simultaneous density estimate of the 120-km2 area was 13.3/100 km2. Because the majority of activity occurred in the 26.2 km2 of unburned area within the burn perimeter, the density could have been as high as 73.8 bears/100 km2. Superpopulation size in the 120-km2 unburned study area ranged from 21–30; density was estimated at 12.5 bears/100 km2. Female home-range sizes were similar between pre and postburn and unburned Mt. Ord. Managers should be aware of possible negative short-term consequences of wildfire on black bear populations and manage to increase cub survival.

Stan C. Cunningham and Warren B. Ballard "Effects of wildfire on black bear demographics in central Arizona," Wildlife Society Bulletin 32(3), 928-937, (1 September 2004). https://doi.org/10.2193/0091-7648(2004)032[0928:EOWOBB]2.0.CO;2
Published: 1 September 2004

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age ratio
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