camp ripley and arden hills minnesota army national guard training ...

Principal Investigator: Dr. John Krenz
Co-author: Lucas Wandrie
Project: Fisher Ecology
Introduction:
The Fisher:
The fisher (Martes pennanti) is a medium sized animal that belongs to the Family
Mustelidae. Fisher are an important furbearing species in Minnesota and in other areas where
harvest is still legal. In 2007 and 2008, pelts from legally harvested fisher sold for a combined
total of more than $80,000 (Abraham and Dexter 2008). The average price per pelt in 2007 and
2008 was about $72.00 (Abraham and Dexter 2008). It is important to note that these were
peak prices and fisher pelts typically sell for $25 to $30.
Fisher are sexually dimorphic with adult males being significantly heavier and longer
than adult females (Powell 1993). Males typically weigh between 3.5 and 5.5 kg and range from
90 to 120 cm in length. Females weigh between 2.0 and 2.5 kg and range from 75 to 95 cm
long (Powell 1993).
Historical Background:
Fisher populations were nearly extirpated throughout their historic range in Minnesota
and the rest the United States due to over-harvesting and habitat loss (Powell 1981). No
protective measures were in place in Minnesota before 1917, when fisher harvest was first
prohibited from the first of March to the fifteenth of October. In 1918 and 1923 trapping seasons
were shortened by two additional weeks (Balser and Longley 1966). From 1933 to 1977, the
harvest of fisher at any time was prohibited (Balser and Longley 1966, John Erb, unpublished
data). Minnesota’s fisher population is known to have increased rapidly from the 1940’s until
the early 1960’s; however, population trends after the mid-1960’s are relatively unknown.
(Balser and Longley 1966). Within the last seven years, fisher have begun to re-establish in the
historic part of their range in Minnesota (Erb 2008).
Current Survey Method:
Track surveys and radiotelemetry have both been used to estimate population density of
fisher. Until the winter of 2007, the Minnesota Department of Natural Resources (MNDNR)
used track surveys (John Erb, unpublished data). The track method requires adequate snowfall
and quality, ability to identify tracks, and access to fisher habitats (i.e., plowed roads) (Beauvais
and Buskirk 1999, John Erb, unpublished data). Track methods can have widely varied results
ranging from one fisher every 10-800 km 2 (Arthur et al, 1989). Due to the problems associated
with tracking surveys the MNDNR now uses radiotelemetry to estimate population density.
Radiotelemetry is a more accurate means to delineate home-range size, with means ranging
from 2.1-51.8 km 2 (Koen et al 2004, Arthur et al 1989, Self and Kerns 2001, Zielinski et al 2004,
Joel Sauder, personal communication). Therefore, it is suggested to use radiotelemetry to
determine home range sizes with precision. Mean home range size can be used to determine
density of fisher within a given area; this can be denoted as (number of individuals/ 100 km 2 )
(Fuller et al 2001, Koen et al 2007). As fisher are intrasexually territorial and not intersexually
territorial, adding the number of males and females per 100 km 2 can be used to calculate
density.
Habitat Use:
Fisher are known to be one of the most habitat specialized mammals in North America
(Weir and Harestad 2003). Fisher prefer an extensive canopy and will avoid open areas (Powell
2009 Conservation Program Report
Page 224