MIXED-SEVERITY WILDFIRES HAVE A NEGATIVE EFFECT ON FISHERS AND A POSITIVE EFFECT ON GRAY FOXES

David S Green; Oregon State University; greendav@oregonstate.edu; Sean, M, Matthews, Laura, L, Finley, Roger, A, Powell

The combination of many years of fire suppression and global climate change is predicted to increase the frequency and intensity of wildfires in certain parts of the world, especially in the western United States. Large-scale wildfires have the capacity to reduce, fragment, or permanently change habitat and are a major source of conservation and management concern for forest wildlife. We used data collected from a long-term monitoring program to investigate the effects of a naturally-occurring mixed-severity wildfire on the populations of two mesopredators in northern California and southern Oregon: fishers (Pekania pennanti) and gray foxes (Urocyon cinereoargenteus). Using genetic data collected with hair snares, we applied spatial capture-recapture models to estimate fisher and fox densities the year before the fire, the year of the fire, and the two years immediately following the fire. Fisher populations declined significantly following the fire, most notably in the areas where there was more than a 50% loss of canopy cover. In contrast to this pattern, gray fox populations increased significantly following the fire and were also influenced by local fisher densities. Our findings provide further evidence that fishers may suppress gray fox populations where they persist.

Ecology and Conservation of Mammals II