title: Whitebark pine, population density, and home-range size of grizzly bears in the greater yellowstone ecosystem.
abstract: Changes in life history traits of species can be an important indicator of potential factors influencing populations. For grizzly bears (Ursus arctos) in the Greater Yellowstone Ecosystem (GYE), recent decline of whitebark pine (WBP; Pinus albicaulis), an important fall food resource, has been paired with a slowing of population growth following two decades of robust population increase. These observations have raised questions whether resource decline or density-dependent processes may be associated with changes in population growth. Distinguishing these effects based on changes in demographic rates can be difficult. However, unlike the parallel demographic responses expected from both decreasing food availability and increasing population density, we hypothesized opposing behavioral responses of grizzly bears with regard to changes in home-range size. We used the dynamic changes in food resources and population density of grizzly bears as a natural experiment to examine hypotheses regarding these potentially competing influences on grizzly bear home-range size. We found that home-range size did not increase during the period of whitebark pine decline and was not related to proportion of whitebark pine in home ranges. However, female home-range size was negatively associated with an index of population density. Our data indicate that home-range size of grizzly bears in the GYE is not associated with availability of WBP, and, for female grizzly bears, increasing population density may constrain home-range size.
authors: Large Carnivore Section, Wyoming Game and Fish Department, Lander, Wyoming, United States of America.
authors: Daniel D
authors: DD
authors: Bjornlie
authors: U.S. Geological Survey, Northern Rocky Mountain Science Center, Interagency Grizzly Bear Study Team, Bozeman, Montana, United States of America.
authors: Frank T
authors: FT
authors: Van Manen
authors: University of Montana, College of Forestry and Conservation, Missoula, Montana, United States of America.
authors: Michael R
authors: MR
authors: Ebinger
authors: U.S. Geological Survey, Northern Rocky Mountain Science Center, Interagency Grizzly Bear Study Team, Bozeman, Montana, United States of America.
authors: Mark A
authors: MA
authors: Haroldson
authors: Large Carnivore Section, Wyoming Game and Fish Department, Lander, Wyoming, United States of America.
authors: Daniel J
authors: DJ
authors: Thompson
authors: University of Montana, College of Forestry and Conservation, Missoula, Montana, United States of America.
authors: Cecily M
authors: CM
authors: Costello
mesh_terms: D000818:Animals; D017753:Ecosystem; D005260:Female; D006702:Homing Behavior / Q000502:physiology*; D016014:Linear Models; D008297:Male; D028223:Pinus / Q000502:physiology*; D011156:Population Density; D001503:Ursidae / Q000502:physiology*