Fisher Occupancy Twenty-Five Years After Translocation in The Rocky Mountains of Montana

Abstract

The historical distribution of fisher throughout Montana and the northern Rocky Mountains of the United States is uncertain, and most fishers in Montana appear to be descendants from translocated animals originating from the midwestern United States and British Columbia; however, a genotype that is unique and native to the Northern Rockies of Idaho and Montana exists in west-central Montana. Predictions based on Idaho models depict potential suitable habitat for fishers throughout the Cabinet Mountains of northwest Montana, yet distribution, occupancy and population status is currently unknown for these fishers. We conducted the first comprehensive monitoring of fishers in the Cabinet Mountains of Montana using baited camera/DNA stations. We detected fishers at 7 out of 21 cells, which resulted in a 0.43 probability that fishers occupied a grid cell. Detection probability was low, but increased slightly throughout the sampling periods. Genetic analysis revealed a minimum population count of 4-6 individual fishers in the study area, but all individuals successfully identified were males and of midwestern genetic origin. The low number of fisher detections may indeed reflect low abundance of fisher, yet these results also raise questions about our study design and sampling regime. We recommend future monitoring to increase precision of the occupancy estimate and determine the reason for a lack of female detections. We also recommend maintaining a closed trapping season on fisher, until data exists to indicate a population large enough to sustain harvest