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

Manen, Frank T. van; Haroldson, Mark A.; Bjornlie, Daniel D.; Ebinger, Michael R.; Thompson, Daniel J.; Costello, Cecily M.; White, Gary C.

doi:10.1002/jwmg.1005

Cited by 58 publications

(36 citation statements)

References 72 publications

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“…There is now evidence that some of these southern populations are reaching carrying capacity (Schwartz et al , Sawaya et al , McLellan , Van Manen et al ) and populations will no longer consistently increase but may fluctuate because of changing food conditions (McLellan ). Although precision was low, statistical population reconstruction of grizzly bears in British Columbia suggested an increasing population in hunted PUs through the late 1980s and 1990s but then a decline beginning around 2005 (Hatter ).…”

Section: Discussionmentioning

confidence: 99%

Sustainability of the grizzly bear hunt in British Columbia, Canada

et al. 2016

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The sustainability of the grizzly bear (Ursus arctos) hunt in British Columbia, Canada has been questioned and is a high profile issue, particularly in the media. To investigate the hypothesis that the hunt is unsustainable, we examined the sustainable human‐caused mortality rate for grizzly bears using recent data on vital rates and population projection models and compare these to rates used by the management agency; examined the age and sex ratio of the kill and how the sex ratio changes with age for the entire province, each population unit, and cohorts born each year between 1977 and 1990; summarized population density estimates in hunted population units in British Columbia and compared these to unhunted areas in adjacent jurisdictions; and reviewed case studies of population units that have been highlighted as most likely to have had unsustainable kill levels. Because the natural mortality rate of adult grizzly bears is 1–2% and lower than was estimated when sustainable human‐caused mortality targets were developed, estimated sustainable kill rates are 4–10%, and generally higher than the 4–6% used in British Columbia. We estimated that males have been 3–4 times more vulnerable to being killed by hunters than females, yet males dominate the kill at all ages and the proportion of males increased with age, which is opposite of what is predicted for a heavily hunted population. The average age of female and male grizzly bears killed by hunters increased from 7.1 years and 7.4 years, respectively, in the 1980s to 7.7 years and 8.7 years, respectively, in the 2000s. An average of 107.4 females and 204.9 males per cohort born between 1977 and 1990 were eventually killed by people and recorded, suggesting that many more females than males died for unknown reasons. There have been more population inventories of grizzly bears in British Columbia than in any other jurisdiction. The average density estimate of 21 inventories in hunted areas without salmon (Oncorhynchus spp.) in British Columbia (31.2 bears/1,000 km2) was as high as or higher than nearby unhunted areas. The case studies had the highest kill densities or among the highest kill rates in the province and hunting targets were commonly exceeded and seasons closed or the hunter kill target reduced. Although population inventories in these areas found moderate or even high densities of bears, some are now in decline. Hunter kill data from declining populations had a high proportion of males and these were older, demonstrating that these indices of kill rates are sometimes unreliable. Although more population density, trend, and vital rate measurements would be beneficial, the hypothesis that the grizzly bear hunt has been unsustainable was not supported by our investigation of available information. © 2016 The Wildlife Society.

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Section: Discussionmentioning

confidence: 99%

Sustainability of the grizzly bear hunt in British Columbia, Canada

et al. 2016

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“…Parks and protected areas often serve as areas of reduced human influence to conserve and protect habitats. While many wildlife species have done well within this framework (e.g., grizzly bear [Ursus arctos] recovery in Yellowstone National Park; van Manen et al, 2016), parks and protected areas have been criticized for preserving scenic beauty rather than biodiversity or connectivity (Jenkins, Van Houtan, Pimm, & Sexton, 2015). In North America, mountainous protected areas have a high proportion of rock and ice, which for many species does not provide adequate foraging opportunities (Joppa & Pfaff, 2009).…”

Section: Introductionmentioning

confidence: 99%

Land tenure shapes black bear density and abundance on a multi‐use landscape

Loosen

Morehouse

Boyce

2018

Ecology and Evolution

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Global biodiversity is decreasing rapidly. Parks and protected lands, while designed to conserve wildlife, often cannot provide the habitat protection needed for wide‐ranging animals such as the American black bear (Ursus americanus). Conversely, private lands are often working landscapes (e.g., farming) that have high human footprints relative to protected lands. In southwestern Alberta, road densities are highest on private lands and black bears can be hunted year‐round. On protected lands, road densities are lowest, and hunting is prohibited. On public lands under the jurisdiction of the provincial government (Crown lands), seasonal hunting is permitted. Population estimates are needed to calculate sustainable harvest levels and to monitor population trends. In our study area, there has never been a robust estimate of black bear density and spatial drivers of black bear density are poorly understood. We used non‐invasive genetic sampling and indices of habitat productivity and human disturbance to estimate density and abundance for male and female black bears in 2013 and 2014 using two methods: spatially explicit capture–recapture (SECR) and resource‐selection functions (RSF). Land tenure best explained spatial variation in black bear density. Black bear densities for females and males were highest on parkland and lowest on Crown lands. Sex ratios were female‐biased on private lands, likely a result of lower harvests and movement of females out of areas with high male density. Synthesis and application: Both SECR and RSF methods clearly indicate spatial structuring of black bear density, with a strong influence based on how lands are managed. Land tenure influences the distribution of available foods and risk from humans. We emphasize the need for improved harvest reporting, particularly for non‐licensed hunting on private land, to estimate the extent of black bear harvest mortality.

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“…The summer season is short and most of the 51 cm of average annual precipitation falls as snow. Vegetation generally consists of grasslands at low elevations, conifer forests at mid‐elevations, and alpine tundra at elevations exceeding 2,900 m (van Manen et al ). We defined the study area by the grizzly bear Demographic Monitoring Area (DMA; 49,930 km 2 ), which is deemed suitable grizzly bear habitat (Fig.…”

Section: Study Areamentioning

confidence: 99%

Grizzly bear depredation on grazing allotments in the Yellowstone Ecosystem

et al. 2018

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Grizzly bear (Ursus arctos) conflicts with humans, including livestock depredation on public land grazing allotments, have increased during the last several decades within the Greater Yellowstone Ecosystem (GYE) in the western United States as the grizzly bear population has grown in number and occupied range. Minimizing conflicts and improving conservation efficacy requires information on the relationships between livestock depredations, allotment management, grizzly bear habitat conditions, and their interactions. We used generalized linear mixed models to evaluate spatio‐temporal relationships between grizzly bear depredation of livestock and the characteristics of 316 United States Department of Agriculture Forest Service and National Park Service grazing allotments in the GYE during 1992–2014. We evaluated relationships at 2 spatial extents, representing daily and annual grizzly bear activity areas. During the study period, more grazing allotments became occupied by grizzly bears and most livestock depredations were associated with these areas of population expansion. Number of livestock (β = 1.15 ± 0.19 [SE]) and grizzly bear density index (β = 1.13 ± 0.10) had the greatest effects on the number of livestock depredation events relative to other allotment attributes. Estimated number of depredation events increased by approximately 20% when cow‐calf pairs increased by 100 pairs and grizzly bear density index increased by 1 bear/196 km2 (the average annual home‐range size of a female grizzly bear in the GYE). Additionally, grazing allotment size was positively related to the number of depredation events (β = 0.56 ± 0.16), whereas the presence of bull cattle or horses was associated with an approximately 50% reduction in depredations (β = −0.71 ± 0.37). Livestock depredation events were greater for allotments with lower road density (β = −0.89 ± 0.28), less rugged terrain (β = −0.57 ± 0.25), higher vegetative primary productivity (β = 0.33 ± 0.16), and more whitebark pine coverage (β = 0.30 ± 0.15). Relationships between depredations and grizzly bear habitat conditions varied across spatial extents. As the grizzly bear population continues to expand, natural resource managers and livestock producers could focus efforts on allotments with a higher density of grizzly bears, fewer roads, and quality grizzly bear habitat, including higher vegetative productivity, when developing cooperative management plans and preventative measures to reduce the likelihood of depredation. The perspectives gained from our analysis provide context for long‐term, landscape‐level planning to accommodate livestock production on public lands while meeting conservation goals for grizzly bears. © 2018 The Wildlife Society.

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

Cited by 58 publications

References 72 publications

Sustainability of the grizzly bear hunt in British Columbia, Canada

Sustainability of the grizzly bear hunt in British Columbia, Canada

Land tenure shapes black bear density and abundance on a multi‐use landscape

Grizzly bear depredation on grazing allotments in the Yellowstone Ecosystem

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