Grizzly bear population vital rates and trend in the Northern Continental Divide Ecosystem,Montana |
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| Authors: | Richard D. Mace Daniel W. Carney Tonya Chilton-Radandt Stacy A. Courville Mark A. Haroldson Richard B. Harris James Jonkel Bruce Mclellan Michael Madel Timothy L. Manley Charles C. Schwartz Christopher Servheen Gordon Stenhouse John S. Waller Erik Wenum |
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| Affiliation: | 1. Montana Fish, Wildlife and Parks, 490 North Meridian Road, Kalispell, MT 59901, USA;2. Blackfeet Tribe, Blackfeet Fish & Wildlife Department, Box 850, Browning, MT 59417, USA;3. Confederated Salish and Kootenai Tribe, 408, 6th Avenue East, Polson, MT 59860, USA;4. U.S. Geological Survey, Northern Rocky Mountain Science Center, Interagency Grizzly Bear Study Team, Forestry Sciences Lab, Montana State University, Bozeman, MT 59717, USA;5. Department of Ecosystem and Conservation Science, College of Forestry and Conservation, University of Montana, Missoula, MT 59801, USA;6. Montana Fish, Wildlife and Parks, 3201 Spurgin Road, Missoula, MT 59804, USA;7. British Columbia Ministry of Forests Research Branch, PO Box 1732, D'Arcy, BC, Canada V0N 1L0;8. Montana Fish, Wildlife and Parks, Rocky Mountain Front Field Office, Rural Route 2, Box 225, Choteau, MT 59422, USA;9. U.S. Fish and Wildlife Service, University of Montana, Missoula, MT 59812, USA;10. Foothills Research Institute, Box 6330, Hinton, Alberta, Canada T7V 1X7;11. National Park Service, Glacier National Park, PO Box 128, West Glacier, MT 59936, USA |
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| Abstract: | We estimated grizzly bear (Ursus arctos) population vital rates and trend for the Northern Continental Divide Ecosystem (NCDE), Montana, between 2004 and 2009 by following radio-collared females and observing their fate and reproductive performance. Our estimates of dependent cub and yearling survival were 0.612 (95% CI = 0.300–0.818) and 0.682 (95% CI = 0.258–0.898). Our estimates of subadult and adult female survival were 0.852 (95% CI = 0.628–0.951) and 0.952 (95% CI = 0.892–0.980). From visual observations, we estimated a mean litter size of 2.00 cubs/litter. Accounting for cub mortality prior to the first observations of litters in spring, our adjusted mean litter size was 2.27 cubs/litter. We estimated the probabilities of females transitioning from one reproductive state to another between years. Using the stable state probability of 0.322 (95% CI = 0.262–0.382) for females with cub litters, our adjusted fecundity estimate (mx) was 0.367 (95% CI = 0.273–0.461). Using our derived rates, we estimated that the population grew at a mean annual rate of approximately 3% (λ = 1.0306, 95% CI = 0.928–1.102), and 71.5% of 10,000 Monte Carlo simulations produced estimates of λ > 1.0. Our results indicate an increasing population trend of grizzly bears in the NCDE. Coupled with concurrent studies of population size, we estimate that over 1,000 grizzly bears reside in and adjacent to this recovery area. We suggest that monitoring of population trend and other vital rates using radioed females be continued. © 2011 The Wildlife Society. |
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| Keywords: | grizzly bear lambda Montana mortality population trend reproduction survival Ursus arctos |
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