Fishers as "old growth" species response

Fishers as "old growth" species response by Rick Sweitzer , at 9:43 p.m. on 26 July 2009,

Dear Linda,

Thanks for your question, and yes, we are aware of the extensive logging that occurred throughout the Fisher Project study area and in Yosemite NP in the late 1800s and early 1900s. The legacy of the logging that occurred here is very apparent from the many old tree stumps, rusty and partially buried cables, and grown over logging roads in the area. Importantly, however, the forest has regrown in the intervening years and large areas of the Bass Lake Ranger District include large diameter, 2nd growth timber approaching 80-100 yrs in age. Although not “old growth” forest per se, these “mature forest” habitats include many of the features that fishers require including relatively high aboveground biomass, closed canopy conditions (>50-60% canopy cover), and the presence of large trees and snags with cavities that provide both rest sites and den sites. When discussing forest conditions important for fishers in our presentations, we note that fishers prefer mature and old growth forest habitats. We will be careful to explain that the fisher habitat in our study area is not “old growth” forest.

Regarding your comment on fisher mortalities, at our most recent Fisher Integration Meeting in Fresno on July 15, 2009, we discussed the multiple different sources of mortality now documented for fishers in the Sierra National Forest. Vehicle strikes (roadkills) are an important source of mortality for fishers in the project area, but especially in southwestern Yosemite NP. The speed limit in the area of the park where fishers are being killed on the Wawona Road/Hwy 41 is currently 35 mph. The speed limit along Hwy 41 just south of the park boundary is also 35 mph. Unfortunately not all motorists obey the speed limit, and it is difficult for drivers to see these darkly colored animals on the highway at night when they are out foraging. It is possible that some combination of reduced speed limits, better enforcement, and appropriate signs like those used for bears in Yosemite NP may help mitigate the problem.

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