Movements and habitat-use of grizzly bears along U.S. Highway 2 in northwestern Montana, 1998--2001

Highways and railroads are suspected agents of population and habitat fragmentation worldwide. Animal movement and habitat selection studies are evolving rapidly thanks to collar-borne global positioning system (GPS) receivers and advances in statistics. I used these new technologies to investigate how U.S. Highway 2 (US-2) affects movements and habitat use of grizzly bears ( Ursus arctos), examine fine-scale movement patterns, and compare habitat selection and home range estimation based on GPS telemetry and aerial very high frequency (VHF) telemetry. I discuss my findings relative to grizzly bear management.; I found that bears crossed highways, but that crossing frequency was negatively related to traffic volume; most crossings occurred at night when highway traffic was least and railroad traffic highest, and that grizzly bears avoided areas near highways. I projected that US-2 could become a barrier to bear movement in ∼30 years.; Using GPS telemetry, I found that adult females moved most and adult males least. Habitat use was not related to residence time, path tortuosity, and directional persistence, and was not unequivocally related to human development. Habitat selection rankings stabilized at 8 telemetry locations/day. Habitat selection rankings and home ranges based on VHF telemetry were different than those based on GPS telemetry for some bears. Although VHF telemetry evenly sampled kernel home range isopleths constructed from GPS data, home ranges based on VHF data missed areas with concentrations of GPS telemetry points. Kernel home range size declined as GPS sampling intensity increased. All individuals showed selection among habitats and high concordance among sampling intensities within habitats. Selection strength declined as sampling intensity increased, but strongly selected habitats remained so across most GPS sampling intensities. I found no relationship between grizzly bear GPS telemetry points or movement paths and scored human impact categories within a model of predicted linkage areas. The shape of the distribution of habitat selection values among grizzly bear GPS telemetry points, as predicted by a previously constructed model, closely matched the distributional shape of values across our study area, although the mean value of GPS points was higher than the study area average.