Kings River Fisher Project:
Links between landscape condition and survival and reproduction of fishers in the Kings River Area in the Sierra National Forest
Fishers and fire in the Sierra Nevada Mountains: Historically, the Sierra Nevada was characterized by frequent, low-intensity surface fires that reduced fuel loads and created a mosaic of diverse habitat patches. However, in the interest of protecting developments or natural resources, 20th century forest management was dominated by fire suppression efforts and a gradual buildup of fuels. Now, the regional fire regime has changed; fires are larger, more intense, and outside the range of historic variability. Faced with this fact, forest managers are now searching for ways to reduce fuel loads and bring the fire regime back within historical bounds without harming native species.
In particular, there is great concern that fuel reduction efforts will harm the small, native fisher population in the southern Sierras. Isolated, reduced to less than 400 individuals, and genetically homogeneous, the population is considered to be at high risk of extinction. In 2004, the U.S. Fish and Wildlife Service found that protection for the West Coast population of fishers was warranted and a decision is expected in 2014. The California Department of Game and Fish is currently considering a petition to add the fisher to the state's endangered species list.
Fishers' preference for dense, structurally-diverse forests presents a conservation challenge: How do we balance the short-term risks associated with forest thinning and fuel reduction with the larger risk of a habitat-destroying catastrophic fire? Recently, the Conservation Biology Institute released a comprehensive modeling effort designed to help clarify this trade-off. Their conclusion was that the risk and negative impacts of a catastrophic fire overshadowed the loss of habitat associated with fuel reduction efforts. Despite this clear recommendation, managers are still faced with the daunting task of deciding how to implement fuel reduction efforts in such a way that any negative impacts on fishers and other closed canopy species are minimized.
In response to the challenges outlined above, the Pacific Southwest Research Station initiated the Kings River Fisher Project in 2007. Primary objectives included filling gaps in our current understanding of fisher ecology and habitat requirements, and addressing the uncertainty surrounding the effects of timber harvest and fuels treatments on select response variables of interest, including fishers and their habitat.
The project area is located southeast of Shaver Lake in the High Sierra Ranger District of the Sierra National Forest, at an elevation between 1,067 and 2,134 meters. The site encompasses approximately 53,200 ha of Sierran mixed conifer, ponderosa pine, and montane hardwood-conifer habitat. Dominant tree species include ponderosa pine (Pinus ponderosa), incense cedar (Libocedrus decurrens), white fir (Abies concolor), and California black oak (Quercus kellogi). Recreational activity, including camping, hunting, and off-road driving are common throughout the Sierra National Forest in the summer and fall months, and the area contains numerous logging roads and 4x4 routes. In winter, only main roads are plowed, numerous roads are gated, and recreational activity is reduced.
Fisher behavior, habitat use, and survival are monitored using several methods including live capture, radio telemetry, and scat detector dog surveys. Captured animals are anesthetized and equipped with radio collars. Biological samples collected during captures include tissue, blood, and hair samples as well as bioelectrical impedance (BIA) values. Tissue and hair samples are used for DNA analysis, allowing us to identify parental and sibling relationships as well as link individual animals to samples collected by scat detector dogs. Blood samples are used to evaluate past and current exposure rates to pathogens such as canine distemper and parvovirus. BIA measurements are a non-lethal way to calculate body fat; changes in scores can reflect changes in body condition related to fuel treatments and habitat modification. Post-release, the survival and movement of radio collared animals is monitored using a combination of remote triangulations and rest-site walk-ins.
Scat detector dog teams, provided by the University of Washington's Center for Conservation Biology, conduct fall and spring surveys of the core study area. Scats are first separated into fecal material and prey remains. Fecal material is sent to the USFS RMRS Wildlife Genetics Lab for species confirmation and individual identification. Scat samples provide not only a location for habitat use analyses, but also prey remains and hormone levels which can be used as an indicator of the stress associated with habitat change.
Habitat conditions, including forest composition and structure, are evaluated using a combination of plot-level measurements taken at resting and denning sites, as well as through the use of LiDAR data.
Mortalities collected are sent to the University of California Veterinary Pathology Lab for necropsy. Additional tests conducted include screening for disease, the presence of rodenticides or other toxins, and genetic confirmation of the predator species responsible.
Results To Date
Since 2007, over 100 fishers have been captured and radio collared. One hundred and fifty-three dens have been located, and over 500 resting structures have been identified. Forty mortalities have been collected, with predation the primary cause of death.
University of California at Berkeley, Sierra Nevada Adaptive Management Program; University of Washington Center for Conservation Biology; Rocky Mountain Research Center Wildlife Genetics Laboratory; University of California at Davis; Integral Ecology Research Center; Pacific Southwest Research Station Redwood Sciences Lab; Southern California Edison; USGS Pautexant Wildlife Research Center
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