GRIZZLY BEAR INVENTORY OF THE PROPHET RIVER AREA, NORTHEASTERN BRITISH COLUMBIA Submitted to: Prophet River Indian Band Dene Tsaa First Nation Box 3250, Fort Nelson, BC V0C 1R0 Canadian Forest Products Ltd. Chetwynd Division P.O. Box 180, Chetwynd, BC V0C 1J0 B.C. Ministry of Environment, Lands and Parks Fish and Wildlife Branch, Peace Subregion Rm 400, 10003 110th Street, Fort St. John, BC V1J 6M7 Prepared by: K. G. Poole, G. Mowat, and D. A. Fear Timberland Consultants Ltd. Fish and Wildlife Division P. O. Box 171 (2620 Granite Rd.) Nelson, BC V1L 5P9 Tele.: (250) 354-3880 e-mail: [email protected] December 1999 Prophet River Wildlife Inventory Report No. 10 Prophet River grizzly bear inventory ii ABSTRACT Current harvest management of grizzly bears (Ursus arctos) in British Columbia (B.C.) is based primarily on modeling of habitat capability/suitability. No research has been conducted in the northern half of the province to verify these habitat-based estimates. In reaction to concerns from First Nation peoples, outfitters and government managers about grizzly bear population size in northeastern B.C., a DNA-based mark-recapture inventory was conducted in the Prophet River area. The study area covered 8,527 km2, and stretched from the continental divide of the northern Rocky Mountains in the west to the boreal plains in the east. The area included the Northern Boreal Mountains and Taiga Plains ecoprovinces, and the Alpine Tundra, Spruce- Willow-Birch, and Boreal White and Black Spruce biogeoclimatic zones. Fieldwork was conducted between 25 May and 1 August 1998 using a helicopter and a truck with an all terrain vehicle. The study area was divided into a grid of 103 9 x 9 km (81 km2) cells. Bait sites consisted of fish rotted to a liquid and rotten beef blood poured on a mound of sticks, branches, stumps and moss placed in the centre of a site. The site was encircled by 20-30 m of barbed wire strung at 50 cm height around 3 or more trees. Sites were left for 12 days, then moved >1 km from all previous sites to a new site within each cell. Five sites were placed sequentially in all cells, resulting in 515 capture sites. We collected 2,062 hair samples from 332 sites. After sorting to remove identifiable black bear (U. americanus) samples and samples with no roots, we ran genetic species tests on 1,139 samples. We identified 544 grizzly samples, 453 black bear samples, 1 sample with hair from both bear species, 25 wolf (Canis lupus) samples, and obtained 116 tests which failed due to insufficient DNA or because they were not bear or wolf. We detected grizzly bears at 113 sites. DNA fingerprinting of grizzly bear samples identified 104 different bears; 48 of these individuals were females, 49 were males, and the remaining 7 individuals could not be sexed. Thirty-eight grizzly bears were caught at >1 site. We used Darroch's closed mark-recapture model (Mt-Darroch) to obtain a naïve population estimate for our study area of 169 grizzly bears [95% confidence interval (CI) 140-212]. We reduced this estimate by 6% to account for closure bias, which resulted in an adjusted population estimate of 159 grizzly bears (95% CI 130-202 or ± 23% of the mean) within the study area (19 bears/1,000 km2). We also estimated population size and density within the 2 broad biophysical provinces in the study area: corrected for closure the Northern Boreal Mountains in the western one-third of the study area contained 106 grizzly bears [(95% CI 84-141), 35 bears/1,000 km2] and the Taiga Plains in the eastern two-thirds contained 56 grizzly bears [(95% CI 38-100), 10 bears/1,000 km2]. Sex cohorts of bears (single males, single females and family groups) appeared to be distributed throughout the study area, and there was no evidence of clustering of bears around the study area border. The current habitat-based capability ratings for grizzly bears in the boreal ecoprovinces of B.C. are supported by our results in the Taiga Plains, but are lower than densities we obtained in the Northern Boreal Mountains by more than half. Additional DNA-based mark-recapture studies of grizzly bears in other locations in the northern boreal portion of B.C. should be conducted to provide comparative data to this study. Capture success during this study would suggest that future users of this technique could use fewer capture sessions and still achieve adequate precision for management requirements. Timberland Consultants Ltd. Prophet River grizzly bear inventory iii TABLE OF CONTENTS ABSTRACT.................................................................................................................................... ii TABLE OF CONTENTS...............................................................................................................iii LIST OF FIGURES ....................................................................................................................... iv LIST OF TABLES......................................................................................................................... iv INTRODUCTION .......................................................................................................................... 1 STUDY AREA ............................................................................................................................... 1 METHODS ..................................................................................................................................... 3 Survey design.............................................................................................................................. 3 Field methods.............................................................................................................................. 4 DNA analysis.............................................................................................................................. 5 Data Analysis.............................................................................................................................. 6 RESULTS ....................................................................................................................................... 6 Hair collection and analysis........................................................................................................ 6 Population size............................................................................................................................ 9 Effects of habitat on population density ................................................................................... 11 Bear movements........................................................................................................................ 12 DISCUSSION............................................................................................................................... 12 MANAGEMENT RECOMMENDATIONS................................................................................ 16 ACKNOWLEDGEMENTS.......................................................................................................... 17 LITERATURE CITED ................................................................................................................. 17 APPENDIX 1. Results of Goodness of Fit tests from CAPTURE for the Prophet River grizzly bear inventory, summer 1998. ...................................................................................................... 20 Timberland Consultants Ltd. Prophet River grizzly bear inventory iv LIST OF FIGURES Figure 1. Prophet River grizzly bear DNA inventory study area, grid cells and site locations, 1998. Sites that captured grizzly bears are shown in solid circles, sites that did not are shown in open circles. Numbers refer to cell numbers.......................................................... 2 Figure 2. Location of black bear captures in the Prophet River grizzly bear DNA inventory study, 1998. Sites that captured black bears are shown in solid circles, sites that did not are shown in open circles.............................................................................................................. 8 Figure 3. The total number of grizzly bears captured per trapping session, the number of new bears captured per session, and the proportion of captured bears which were new bears in each of 5 capture sessions on the Prophet River study area, 1998. ...................................... 10 LIST OF TABLES Table 1. Grizzly bear hair capture results from the Prophet River grizzly bear DNA inventory, 1998. One hundred and three cells were sampled during each capture session. ................... 7 Table 2. Hair sorting identification checked by DNA species identification, Prophet River grizzly bear inventory, 1998. .................................................................................................. 9 Table 3. Grizzly bear population estimates from 8 closed mark-recapture models in program CAPTURE from DNA analysis of hair collected at bait sites during summer 1998 for the Prophet River area................................................................................................................. 10 Table 4. The relationship between grizzly bear detection rate and ecosystem, topographic and habitat variables, Prophet River area, 1998. ......................................................................... 11 Table 5. Distance moved (km) among recaptured grizzly bears by ecoprovince and sex class, Prophet River, 1998. ............................................................................................................