Environmental and anthropogenic influences on fisher (Pekania pennanti) den attendance patterns in California

The fisher (Pekania [formerly Martes] pennanti) is a house-cat-sized forest carnivore in the family Mustelidae, and populations on the west coast of North America are of conservation concern. Adult female survival and reproduction has been suggested as a key element for maintaining and recovering these populations. Although many research efforts have focused on den ecology of fishers, few have focused on the behavior of denning fishers. Understanding patterns in fisher den attendance and how anthropogenic activities may influence those patterns could inform forest management practices and research methodologies for conservation benefit. I documented fisher den attendance patterns, as wells as the biological, environmental, and research-related disturbance factors that influenced fisher den attendance by monitoring radio-collared female fishers in 3 isolated populations in California, United States. I found that fisher den attendance patterns were similar across the 3 populations in California, with minor differences in the environmental factors that influenced den attendance. Fishers were present at their dens greater than 50% of the time during the first 4 weeks following parturition. Proportions of time fishers were present at the den, as a function of kit age, did not vary regionally. Fishers were also generally present at the den throughout crepuscular morning hours regardless of kit age, though den attendance during daytime and nighttime hours varied regionally. I also found that the presence of a researcher at the den while the mother was present caused fishers to spend 35-125 minutes longer at the den than they otherwise would. Following from my results, I recommend that researchers minimize events in which they approach radio-collared fishers at dens. I also recommend that future studies examine the effects of anthropogenic disturbances on denning fisher behavior, and that they link behavioral changes, reproductive success, and kit survival rates to quantify how disturbances may impact fisher populations.