VARIATION IN INTERSPECIFIC NICHE OVERLAP ACROSS A LATITUDINAL AND CLIMATIC GRADIENT: MARTEN AND FISHER AT THEIR RANGE MARGINS IN THE SOUTHERN SIERRA NEVADA

Jody M Tucker; USFS, Pacific Southwest Region, Sequoia National Forest; jtucker@fs.fed.us; William,J,Zielinski, Kerry,M,Rennie

We explored species' niche relations of marten and fisher at the southern margins of their ranges in the southern Sierra Nevada (SSN) using data from 2 sources: (1) large-scale camera, track-plate, and hair-snare surveys and (2) data on overlap of marten and fisher home ranges from radio-marked individuals. These sources made it possible to examine the current distributions with high resolution and to explore how the spatial pattern of those distributions (parapatric, sympatric, allopatric) change along latitudinal, elevational and climatic gradients. We found significantly different spatial patterns across the SSN: marten and fisher were primarily allopatric in the northern and wetter portions of the study area but sympatric at intermediate latitudes with lower precipitation. In the driest and southernmost region martens were virtually absent but fishers were routinely detected at significantly higher elevations. Within the region of sympatry telemetry data demonstrated significant spatial overlap occurred at the level of the home range with 84% of marten exhibiting spatial avoidance of fisher where the species’ home ranges overlapped. Studying how the warmer and drier environment at the southern end of species' ranges affects distributions and interactions may provide insights about future distributions and spatial interactions farther north as the climate warms.

Ecology and Conservation of Mesocarnivores