Density of fisher on managed timberlands in north coastal California

A mark-sight study design was used to estimate density of fisher (Martes pennanti) on two study sites on managed timberlands in north coastal California during the summers of 2002 and 2003. Sixty-three fisher captures resulted in 36 individual fishers (19 females, 17 males) being marked with uniquely colored ear tags. Fisher were photographed at camera stations during three 4-week sampling periods in summer of 2002 and four sampling periods in summer 2003. There were 43 independent photographs of 10 marked individuals in 2002 and 154 independent photographs of 19 marked individuals in 2003. There were 110 and 71 independent photographs of unmarked individuals in 2002 and 2003 respectively. I utilized radio telemetry to assess the amount of time individual animals were available on the study sites. I estimated sex-specific density for individual sampling periods and for each year using pooled data from all periods combined. All estimates were for non-juvenile fishers. Female density within sample periods ranged from 0.05-0.09 fisher/km² in 2002 and 0.06-0.11 fisher/km² in 2003 on one site and ranged from 0.11-0.22 fisher/km² in 2002 and 0.06-0.09 fisher/km² in 2003 on the other study site. Male density for individual sample periods could only be estimated on one study site and varied from 0.05-0.07 fisher/km² in 2002 and 0.07-0.09 fisher/km² in 2003. Home range was calculated for 11 female and four male fishers using 100% MCP techniques. Mean home range size was 602 ± 48 ha (x ± SE) for females and 882 ± 400 ha for males. Mean home range size was used to estimate density for comparison purposes and resulted in estimates 22-87 percent greater than those calculated using the mark-site methodology. Mark-site methods better met the assumptions associated with estimating density and produced confidence intervals which make it well suited for making comparisons over time or among studies.