An evaluation of territory mapping to estimate fisher density

We evaluated winter-territory mapping as a method for estimating fisher (Ma rtes pennanti) density in a 210-km(2) survey area in north-central Massachu setts in 1994 and 1995 by comparing estimates with simultaneous camera mark -resight estimates. Assuming intrasexual territoriality and accounting for all occupied habitat, territories of resident radio-marked fishers were map ped (mean = 54% of all territories in the study area), and those of unmarke d resident fishers were identified from tracks and photographs. The total n umber indicated a population of 40 (19/100 km(2)) and 49 (23/100 km(2)) res idents for 1994 and 1995, respectively. Results from replicated automatic-c amera capture-mark-resight surveys suggested slightly higher total numbers and densities of fishers in 1994 (44.5; 21/100 km(2)) and 1995 (52.9; 25/10 0 km(2)), but these estimates likely also included nonresident juveniles. T erritory mapping and automatic-camera mark-resight methods resulted in very similar population estimates, but both require large numbers of radio-mark ed fishers to effectively detect small population changes (e.g., such as th e 20% observed in this study). Individually marking animals would enhance m ark-recapture estimates.