Technical Report

Fisher Diet in the Klamath / North Coast Bioregion

We characterized the diet of fisher in the Klamath/North Coast Bioregion of northern California by collecting 388 fecal remains at four distinct study areas within the Klamath Bioregion and analyzing differences between the warmer and drier interior sites and the marine influenced coastal sites. Mammals, especially Sciuridae, were the most frequent food items (98.0% and 26.8% frequency of occurrence, respectively), which differed from previous reports of fisher diet studies, both within California and elsewhere in their continental range. Interior areas had more use of lizards, members of the family Talpidae, and deer (probably from carrion). On coaastal sites, tree squirrels were used less, but woodrats (Neotoma sp.) were used more. Foodstuffs varied with season at interior sites, which was coincidental with more extreme weather change between seasons. Coastal areas had the greatest overall diversity. Fisher in the Klamath/North Coast Bioregion, and probably elsewher in California, did not extensivley use porcupines or members of the Leporidae family as reported elsewhere in their continental range. Fishers in the Klamath/North Coast Bioregion appeared to forage opportunistically, but mostly used prey within an optimal body-size range (woodrats and tree-squirrels). This body-size selection probably resulted from the inability to make prolonged use of larger prey items and the inefficient energetic acquisition associated with smaller prey. Dietary issues may influence wildlife management decisions. Consideration of fisher reintroductions into regions where they have been extirpated may have an affect on other medium to small body-sized carnivores. Further, forest management practices, such as wildfire and fuels reduction, or vegetative changes at stand or landscape scales may impact prey populations, and consequently produce changes in fisher populations.