Linking Landscape Characteristics to Local Grizzly Bear Abundance Around Glacier National Park

Scientific Disciplines
Biological Sciences - Terrestrial
grizzly bear
road density
glacier national park
Road density influences
Spatial autocorrelation
Local Grizzly Bear Abundance Around Glacier National Park Tabitha A. Graves,* Northern Arizona University
University of Montana CESU
Katherine C Kendall Geological Survey Northern Rocky Mountain Science Center West Glacier Montana
bear abundance
bear hair
mesic habitat
grizzly bear abundance
bear abundance spatial autocorrelation
grizzly bear abundance spatial
Volume 16, No. 4

Linking landscape characteristics to local grizzly bear 
abundance around glacier national park

Tabitha A. Graves,* Northern Arizona University, School of Forestry, Flagstaff, Arizona 86001
Katherine C. Kendall, U.S. Geological Survey Northern Rocky Mountain Science Center, West 
Glacier, Montana 59936 
J. Andrew Royle, U.S. Geological Survey Patuxent Wildlife Research Center, Laurel, Maryland 
Jeffrey B. Stetz and Amy C. MacLeod, University of Montana CESU, West Glacier, Montana 
Grizzly bear (Ursus arctos) habitat use has been extensively studied, but habitat has 
rarely been linked to demographic parameters and habitat models have not accounted for 
variation in detection or spatial autocorrelation. We collected bear hair from bear hair traps 
and rub trees in and around Glacier National Park (GNP) in northwestern Montana and 
genotyped the samples to identify individuals. We developed a hierarchical model with 1) 
explicit landscape and habitat variables that we theorized might influence abundance, 2) 
separate sub-models of detection probability for each sampling type, 3) covariates to explain 
variation in detection, 4) a conditional autoregressive (CAR) term to account for spatial 
autocorrelation, and 5) weights to identify most important variables. Road density and percent 
mesic habitat best explained variation in female grizzly bear abundance and the spatial 
autocorrelation term was not supported. Female abundance was higher where road density 
was lower and where more mesic habitat exists.  Detection of females increased with rub tree 
sampling effort. Road density best explained variation in male grizzly bear abundance and the 
spatial autocorrelation term was supported. More male bears occurred in areas of low road 
density. Detection of males increased with rub tree and hair trap sampling effort and decreased 
with time.  Our finding that road density influences abundance concurs with conclusions of 
earlier studies that road density influences habitat use.