Landscape Evaluation of Grizzly Bear Habitat in Western Montana

: We present a method for evaluating the cumulative effects of human activity on grizzly bear (  Ursus arctos) habitat in the Northern Continental Divide Ecosystem of western Montana. Using logistic regression, we modeled the relative probabilities of female grizzly bear resource selection from telemetry data, TM satellite imagery (greenness), elevation, human activity points, roads, and trails. During spring, adult female grizzly bears were positively associated with low- and mid-elevation habitats. Logistic regression coefficients were negative for all road and human activity variables. Summer and fall coefficients were also negative for road, human activity, and trail variables. During summer and fall, females were positively associated with mid to high elevations. Coefficients were positive for greenness during all seasons. Extrapolations of seasonal potential and realized habitat models were made to other areas on the western side of the region where no telemetry data existed. During spring, much of the Bob Marshall Wilderness exhibited a relatively low probability of use by female grizzly bears, but the converse was observed during summer and fall. The mapping and extrapolation process highlighted areas where habitat restoration would have the greatest benefit. These areas were typically low-elevation spring habitats with high road densities and private lands where urbanization occurred. We recommend that habitat management agencies implement reductions in road densities in seasonal habitat and implement methods to maintain habitat function on private lands. Resumen: Presentamos un metodo para la evaluacion de efectos acumulativos de actividades humanas en el habtat del oso grizzly (  Ursus arctos) en el Ecosistema Norte de Montana Occidental. Modelamos las probabilidades de seleccion de recursos de hembras del oso grizzly utilizando regresion logistica con datos de telemetria, imagen de satelite TM (intensidad del verde), elevacion, puntos de actividad humana, carreteras y veredas. Durante la primavera, las hembras adultas estuvieron postivamente asociadas con habitats de elevacion baja y media. Los coeficientes de regresion logistica fueron negativos para las carreteras y las variables de actividad humana. En verano y Otono los coeficientes fueron tambien negativos para carreteras, actividades humanas y veredas. Durante el verano y el otono, las hembras estuvieron positivamente asociadas con elevacones medias y altas. Los coeficientes fueron positivos para la intensidad del verde en todas las estaciones. Extrapolaciones de modelos de potencial estacional y habitat realizado fueron construidos para otras areas de la region oeste, donde no se han generado datos de telemetria. Durante la primavera, una gran porcion de la region de vida silvestre Bob Marshal exhibio probabilidades de uso relativamente bajas, pero se observo lo contrario durante el verano y el otono. El mapeo y la extrapolacion resaltoareas donde la restauracion del habitat podria proveer los mayores beneficios. Estas areas son tipicamente habitats de arroyos con baja elevacion, con alta densidad de carreteras y tierras privadas donde ha ocurrido urbanizacion. Recomendamos que las agencias de manejo implementen reducciones en la densidad de carreteras en habitats estacionales e implementen metodos para mantener la funcion del habitat en tierras privadas.