Ski areas affect Pacific marten movement, habitat use, and density

Abstract

ABSTRACTAlpine ski recreation is one of the most popular outdoor winter sports globally but often involves habitat modification and dense human activity, both of which can harm wildlife. We investigated the effects of ski area development and winter recreation activities on movement, occupancy, and density of Pacific martens (Martes caurina) in the Lake Tahoe region of California and Nevada, USA by comparing 3 ski and 3 control study areas. We systematically surveyed martens using live traps and hair snares during spring–summer and winter seasons from 2009 through 2011 to identify how martens responded to the year‐round effects of habitat fragmentation from ski area development and the seasonal effects of winter recreation activities. Martens selectively moved between remnant forest patches with the shortest crossing distances across open, non‐forested ski runs in both seasons, with the effect more pronounced in females. Overall, habitat connectivity was reduced by 41% in ski areas compared to habitat not fragmented by ski runs. During spring–summer, occupancy rates were not different between habitat within or outside of ski operations areas. During winter, however, occupancy was significantly lower inside (52%) ski area boundaries than outside (88%) them. Reduced detection probability in ski areas indicated martens also reduced the frequency of use of operations areas in winter. Using spatially explicit capture‐recapture models, we found that marten density did not differ between ski areas and controls during spring, but during winter female density declined at ski areas by 63% compared to spring–summer and was <50% of female density compared to controls. This suggests that females seasonally avoid habitat in ski areas by shifting their habitat use to areas outside ski operations boundaries during winter. Although male marten density did not differ, the lack of resident males >3 years old coupled with higher annual turnover rates suggests male densities at ski areas may be reliant on annual male immigration. In winter, martens avoided using habitat in ski operations areas when recreation activity was greatest. Winter ski recreation may not be incompatible with marten use of habitat in ski areas, but habitat fragmentation from ski areas affects marten movement and recreation activities affect seasonal habitat occupancy and female density. Maintaining functional habitat connectivity, via networks of short ski run crossings that link habitat in and out of ski areas, will be important for maintaining or improving marten use of remnant habitat in developed ski areas. © 2017 The Wildlife Society