Methods to estimate distribution and range extent of grizzly bears in the Greater Yellowstone Ecosystem

Bjornlie, Daniel D.; Thompson, Daniel J.; Haroldson, Mark A.; Schwartz, Charles C.; Gunther, Kerry A.; Cain, Steven L.; Tyers, Daniel B.; Frey, Kevin; Aber, Bryan C.

doi:10.1002/wsb.368

Cited by 18 publications

(21 citation statements)

References 21 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our study area comprised occupied grizzly bear range in the GYE (50,280 km 2 by 2010; Bjornlie et al ) and included Yellowstone National Park, Grand Teton National Park, portions of 5 adjacent national forests, and state and private lands in Montana, Wyoming, and Idaho. The GYE consists of a high‐elevation plateau surrounded by 14 mountain ranges with elevations >2,130 m, and contains the headwaters of 3 continental‐scale rivers.…”

Section: Study Areamentioning

confidence: 99%

Density dependence, whitebark pine, and vital rates of grizzly bears

et al. 2015

Self Cite

View full text Add to dashboard Cite

Understanding factors influencing changes in population trajectory is important for effective wildlife management, particularly for populations of conservation concern. Annual population growth of the grizzly bear (Ursus arctos) population in the Greater Yellowstone Ecosystem, USA has slowed from 4.2–7.6% during 1983–2001 to 0.3–2.2% during 2002–2011. Substantial changes in availability of a key food source and bear population density have occurred. Whitebark pine (Pinus albicaulis), the seeds of which are a valuable but variable fall food for grizzly bears, has experienced substantial mortality primarily due to a mountain pine beetle (Dendroctonus ponderosae) outbreak that started in the early 2000s. Positive growth rates of grizzly bears have resulted in populations reaching high densities in some areas and have contributed to continued range expansion. We tested research hypotheses to examine if changes in vital rates detected during the past decade were more associated with whitebark pine decline or, alternatively, increasing grizzly bear density. We focused our assessment on known‐fate data to estimate survival of cubs‐of‐the‐year (cubs), yearlings, and independent bears (≥2 yrs), and reproductive transition of females from having no offspring to having cubs. We used spatially and temporally explicit indices for grizzly bear density and whitebark pine mortality as individual covariates. Models indicated moderate support for an increase in survival of independent male bears over 1983–2012, whereas independent female survival did not change. Cub survival, yearling survival, and reproductive transition from no offspring to cubs all changed during the 30‐year study period, with lower rates evident during the last 10–15 years. Cub survival and reproductive transition were negatively associated with an index of grizzly bear density, indicating greater declines where bear densities were higher. Our analyses did not support a similar relationship for the index of whitebark pine mortality. The results of our study support the interpretation that slowing of population growth during the last decade was associated more with increasing grizzly bear density than the decline in whitebark pine. Grizzly bear density and its potential effect on vital rates and population trajectory warrant consideration for management of the grizzly bear population in the Greater Yellowstone Ecosystem. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

show abstract

Section: Study Areamentioning

confidence: 99%

Density dependence, whitebark pine, and vital rates of grizzly bears

et al. 2015

Self Cite

View full text Add to dashboard Cite

show abstract

“…Examples of rebounding species include Pteronura brasiliensis Gmelin (Giant River Otter; dos Santos Lima 2014), Canis lupus L. (Wolf; Pletscher et al 1997), Gulo gulo L. (Wolverine; Flagstad et al 2004), Puma concolor L. (Cougar; Larue et al 2012), Ursus arctos L. (Brown Bear; Bjornlie et al 2014, Hagen et al 2015, Swenson et al 1998, and Ursus americanus Pallas (American Black Bear; Bales et al 2005, Frary et al 2011, Onorato et al 2004, Unger et al 2013. The theory of ideal free-distribution assumes that animals colonizing new areas will distribute themselves among the best-quality habitat available (Fretwell 1972).…”

Section: Introductionmentioning

confidence: 99%

Home Ranges and Habitat Selection by Black Bears in a Newly Colonized Population in Florida

Karelus

McCown

Scheick

et al. 2016

Southeastern Naturalist

View full text Add to dashboard Cite

“…It allowed us to explore the trade-off between Fig. Occupied range based on data through 2014 (Bjornlie et al 2014, Costello et al 2016 optimal, short paths (likely important for successful immigration given the current distance between populations) vs. more exploratory paths (characteristic of a dispersing bear traversing unfamiliar landscapes). Study area for delineating potential paths for male-mediated gene flow between the Northern Continental Divide Ecosystem (NCDE) and Greater Yellowstone Ecosystem (GYE) grizzly bear populations.…”

Section: Introductionmentioning

confidence: 99%

“…Occupied range based on data through 2014(Bjornlie et al 2014, Costello et al 2016. Color gradient is based on cumulative values of RSPs for 100 pairs of origin-destination nodes, representing the average number of net passages for each grid cell.…”

mentioning

confidence: 99%

Potential paths for male‐mediated gene flow to and from an isolated grizzly bear population

et al. 2017

Self Cite

View full text Add to dashboard Cite

For several decades, grizzly bear populations in the Greater Yellowstone Ecosystem (GYE) and the Northern Continental Divide Ecosystem (NCDE) have increased in numbers and range extent. The GYE population remains isolated and although effective population size has increased since the early 1980s, genetic connectivity between these populations remains a long-term management goal. With onlỹ 110 km distance separating current estimates of occupied range for these populations, the potential for gene flow is likely greater now than it has been for many decades. We sought to delineate potential paths that would provide the opportunity for male-mediated gene flow between the two populations. We first developed step-selection functions to generate conductance layers using ecological, physical, and anthropogenic landscape features associated with non-stationary GPS locations of 124 male grizzly bears (199 bear-years). We then used a randomized shortest path (RSP) algorithm to estimate the average number of net passages for all grid cells in the study region, when moving from an origin to a destination node. Given habitat characteristics that were the basis for the conductance layer, movements follow certain grid cell sequences more than others and the resulting RSP values thus provide a measure of movement potential. Repeating this process for 100 pairs of random origin and destination nodes, we identified paths for three levels of random deviation (h) from the least-cost path. We observed broad-scale concordance between model predictions for paths originating in the NCDE and those originating in the GYE for all three levels of movement exploration. Model predictions indicated that male grizzly bear movement between the ecosystems could involve a variety of routes, and verified observations of grizzly bears outside occupied range supported this finding. Where landscape features concentrated paths into corridors (e.g., because of anthropogenic influence), they typically followed neighboring mountain ranges, of which several could serve as pivotal stepping stones. The RSP layers provide detailed, spatially explicit information for land managers and organizations working with land owners to identify and prioritize conservation measures that maintain or enhance the integrity of potential areas conducive to male grizzly bear dispersal.

show abstract

Methods to estimate distribution and range extent of grizzly bears in the Greater Yellowstone Ecosystem

Cited by 18 publications

References 21 publications

Density dependence, whitebark pine, and vital rates of grizzly bears

Density dependence, whitebark pine, and vital rates of grizzly bears

Home Ranges and Habitat Selection by Black Bears in a Newly Colonized Population in Florida

Potential paths for male‐mediated gene flow to and from an isolated grizzly bear population

Contact Info

Product

Resources

About