Grizzly bear depredation on grazing allotments in the Yellowstone Ecosystem

• Published in: The Journal of Wildlife Management
• Main Authors: Wells, Smith L., McNew, Lance B., Tyers, Daniel B., Van Manen, Frank T., Thompson, Daniel J.
• Other Authors: U.S. Forest Service, Montana Agricultural Experiment Station
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: Ursus arctos
• Online Access: http://dx.doi.org/10.1002/jwmg.21618; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fjwmg.21618; https://onlinelibrary.wiley.com/doi/pdf/10.1002/jwmg.21618; https://onlinelibrary.wiley.com/doi/full-xml/10.1002/jwmg.21618; https://wildlife.onlinelibrary.wiley.com/doi/am-pdf/10.1002/jwmg.21618

ABSTRACT 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 km 2 (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 ± ...