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Daniel D Bjornlie

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The Randomized Shortest Path (RSP) raster delineates potential dispersal paths for male-mediated gene flow between grizzly bear (Ursus arctos) populations in the Greater Yellowstone Ecosystem (GYE) and the Northern Continental Divide Ecosystem (NCDE). A RSP algorithm was used to estimate the average number of net passages for all grid cells at a spatial resolution of 300 m in the study region which spans parts of Montana, Idaho, and Wyoming. RSP rasters identify potential movement paths for 3 levels of random deviation determined by the parameter Θ (i.e., Θ = 0.01, 0.001, and 0.0001) for bears moving from an origin to a destination node. Lower values of Θ result in greater exploration and more random deviation around...
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Potential movement paths for male grizzly bear (Ursus arctos) dispersal between the Northern Continental Divide and Greater Yellowstone Ecosystems, 2000-2015
For several decades, grizzly bear (Ursus arctos) populations in the Greater Yellowstone Ecosystem (GYE) and the Northern Continental Divide Ecosystem (NCDE) have increased in numbers and range extent. Whereas the NCDE population is contiguous with grizzly bear populations in the Canadian Rocky Mountains, genetic evidence suggests the GYE population remains isolated. Recent analyses indicate the effective population size of GYE grizzly bears has increased and is approaching levels needed for long-term viability. With only ~110 km distance separating current estimates of occupied range for these populations, the potential for immigration into the GYE from an NCDE migrant, or vice versa, is likely greater now than...
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The grizzly bear distribution boundary represents the estimated geographic extent of occupied range of the Yellowstone grizzly bear population for the period 2006-2020. The distribution boundary was delineated to provide reliable estimations of grizzly bear occupancy throughout time and for use as a monitoring tool in grizzly bear management and conservation.The boundary was delineated by the Interagency Grizzly Bear Study Team (IGBST) using an interpolation method based on grizzly bear VHF telemetry and GPS locations as well as verified observations and signs of grizzly bears inside the Greater Yellowstone Ecosystem during 2006 to 2020.
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Grizzly bear (Ursus arctos) habitat use maps delineate predicted habitat use for grizzly bears around federally designated recovery zones in and near western Montana. These raster data are the official data release for Sells et al. (2022), “Grizzly Bear Habitat Selection Across the Northern Continental Divide Ecosystem” and Sells et al. (2023), “Grizzly bear movement models predict habitat use for nearby populations.” In summary, to better understand habitat selection by grizzly bears, Sells et al. (2022) developed and validated individual-based integrated step-selection functions (iSSFs) for 65 grizzly bears monitored in the Northern Continental Divide Ecosystem (NCDE; including 19 males and 46 females). Step-selection...
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Understanding evolutionary processes that drive population dynamics is critical in ecology. Measuring the performance-density relationship in long-lived mammalian species demands long-term data, limiting the ability to observe such mechanisms. We tested density-dependent (intrinsic) and density-independent (extrinsic) drivers of body composition of grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem over two decades.
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