Fisher– Habitat Model
Maternal and Natal Denning Habitat
Morice and Lakes Forest Districts Innovative Forest Practices Agreement
Prepared for:
ML - IFPA
Prepared by
Anne-Marie Roberts
Smithers, BC
DRAFT: MARCH 2004
Fisher Denning Habitat Suitability Model: ML-IFPA
Executive Summary
Species – Habitat models are used to evaluate the potential in the Morice and the Lakes forest districts to
provide suitable habitat for wildlife species selected by the Ecosystem group of the Morice and Lakes
Innovative Forest Practices Agreement (ML-IFPA). The models generally define habitat suitability based
on the provision of certain habitat attributes required for living and reproduction.
Unchanging environmental conditions (such as Biogeoclimatic subzone), location of infrastructure and
development, and projected forest conditions (from the rules defined in individual scenarios), supply much
of the basic information that can be used in the habitat supply models. There are other habitat attributes
that are not directly provided by the available data layers that describe forest cover in terms of species
composition and age. These habitat attributes are derived from information provided in the forest cover
dataset and from data provided in the Predictive Ecosystem Mapping (PEM) using mathematical models
and/or beliefs expressed in the Netica conditional probability tables (Habitat Modeling report #1, in prep).
Empirical relationships, scientific literature, and professional judgment are incorporated into these
equations and/or tables to describe the changes in the state (e.g. abundance, density) of these habitat
attributes through changes in forest succession and disturbance.
This report describes the development of the fisher denning habitat model.
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Title
Table of Contents
Executive Summary ................................................................................................................................ i
INTRODUCTION....................................................................................................................................... 1
FISHER........................................................................................................................................................ 1
SPECIES ACCOUNT AND HABITAT USE INFORMATION ............................................................ 1
DISTRIBUTION ........................................................................................................................................... 1
Provincial Range .................................................................................................................................. 1
Elevational Range ................................................................................................................................. 1
Provincial Context ................................................................................................................................ 1
ECOLOGY AND KEY HABITAT REQUIREMENTS ........................................................................................ 1
General ................................................................................................................................................. 1
FOOD/COVER LIFE REQUISITES AND HABITAT-USES ................................................................................ 3
Habitat Requirements Summary ........................................................................................................... 3
Seasons of Use ...................................................................................................................................... 4
Living During Winter ............................................................................................................................ 5
Feeding Habitat – Winter .................................................................................................................. 5
Security/Thermal/Denning Habitat – Winter .................................................................................... 5
Reproducing (Birthing) ......................................................................................................................... 5
FISHER WINTER HABITAT MODEL................................................................................................... 6
APPLICATION OF MODEL .......................................................................................................................... 6
ASSUMPTIONS ........................................................................................................................................... 6
FISHER DENNING MODEL DESCRIPTION ................................................................................................... 8
Description of Network Nodes .............................................................................................................. 8
Maternal Denning Habitat ................................................................................................................. 8
Cottonwood ....................................................................................................................................... 9
Ecosystem Potential .......................................................................................................................... 9
Riparian or Wetland Buffer? ........................................................................................................... 10
Ac Ecosystem Potential .................................................................................................................. 10
FISHER WINTER FORAGING HABITAT DESCRIPTION .............................................................................. 10
Description of Network Nodes ............................................................................................................ 11
Winter Foraging Habitat ................................................................................................................. 11
Accessibility.................................................................................................................................... 12
Snow Depth..................................................................................................................................... 12
Crown Closure Class....................................................................................................................... 13
Forage Forest Attributes.................................................................................................................. 13
Understory Potential ....................................................................................................................... 14
Large Coarse Woody Debris ........................................................................................................... 14
Riparian or Wetland Buffer............................................................................................................. 14
COMPUTING OUTPUT FOR HABITAT VALUE ........................................................................................... 15
SENSITIVITY ANALYSIS ........................................................................................................................... 15
TESTING AND VALIDATION ..................................................................................................................... 15
RESEARCH NEEDS FOR MODEL VERIFICATION ....................................................................................... 15
IMPLICATIONS FOR MANAGEMENT ......................................................................................................... 16
REFERENCES .......................................................................................................................................... 17
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Title
APPENDIX A: SUITABILITY RATINGS FOR SPECIES ACCOUNT MORICE AND LAKES
FOREST DISTRICT ................................................................................................................................ 19
RATINGS .................................................................................................................................................. 19
Provincial Benchmark......................................................................................................................... 19
PRELIMINARY RATINGS TABLES ............................................................................................................. 22
List of Tables
Table 1. Summary of habitat requirements for Fisher in the study area. ..................................................... 4
Table 2. Life requisites by month and season for fisher in the project area. ............................................... 4
Table 3. Conditional probabilities used within Netica© to configure the relationship between the reported
presence of black cottonwood (Ac) in the polygon and potential of the ecosystem as a cottonwood
site in describing maternal denning habitat suitability for fisher. .......................................................... 9
Table 4. Riparian and wetland buffers included in the fisher riparian file as influencing the potential
presence of black cottonwood. ........................................................................................................... 10
Table 5. Conditional probabilities used within Netica to configure the relationship between forage forest
attributes and accessibility of fisher to forage attributes. .................................................................... 11
Table 6. Conditional probabilities used within Netica© to configure the relationship between snow depth
and crown closure class in defining the ability of fisher to access a habitat. ...................................... 12
Table 7. Ratings of crown closure class on accessibility to habitats of fisher in the Morice and Lakes
forest districts. ..................................................................................................................................... 13
Table 8. Conditional probability of the value of forage forest attributes given the understory structure,
volume of large coarse woody debris and presence of riparian features. .......................................... 13
List of Figures
Figure 1. Habitat variables and ecological relationships used to build the fisher maternal denning habitat
suitability Bayesian belief model in the Netica© program..................................................................... 8
Figure 2. Conditional probabilities used within Netica to configure the relationship between riparian and
wetland buffers and the potential of the ecosystem to grow cottonwood trees. ................................... 9
Figure 3. Habitat variables and ecological relationships used to build the fisher winter foraging habitat
suitability Bayesian belief model in the Netica© program................................................................... 11
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INTRODUCTION
This report describes the fisher maternal denning habitat model developed for the Morice and Lakes
Innovative Forest Practices Agreement (ML-IFPA). The following document includes a species account
for fisher (Marten pennanti), outlines the logic used and the assumptions made in the preparation of the
model, describes the model and the relationships used to build the model, and outlines testing of model
sensitivity and the current level of validation.
FISHER
Common Name:
Fisher
Scientific Name:
Martes pennanti
Species Code:
M-MAPE
Status:
The Provincial Tracking Lists of the British Columbia Conservation Data Centre
designate Fisher as a Blue (Bl) listed species (vulnerable or at risk). Fisher are
managed as a “Class 2” furbearer ("not present on most registered traplines in
manageable numbers, and vulnerable to overharvest").
SPECIES ACCOUNT AND HABITAT USE INFORMATION
Distribution
Provincial Range
The fisher only occurs in North America (Douglas and Stickland 1987) and is a non-migratory year-round
resident of British Columbia. Fisher generally occur throughout the province but are not common and do
not occur on coastal islands, including Vancouver Island (Banci 1989). The northern limit of their
distribution in the province is located near the British Columbia and Yukon border.
Elevational Range
Fisher are generally restricted to low and middle elevation habitats in the winter due to an apparent
difficulty in mobility during deep snow conditions found at high elevations (Krohn et al. 1997). Low
elevation coastal forests are also not commonly used due to deep snow accumulations. There is not a
seasonal elevational migration and fisher do not typically use higher elevation habitats.
Provincial Context
Latest attempts to estimate the population give a range of 1113 to 2759 (based on two density scenarios),
with 1454-2236 being the most likely range (Weir, in prep.).
Ecology and Key Habitat Requirements
General
The fisher is a member of the Mustelidae Family, which includes wolverines, weasels, otters, skunks and
the American marten (Martes americana), which is closely related to the fisher. The fisher is a solitary
animal that is active both day and night, with activity peaks near sunrise and sunset (Banci 1989).
Optimal habitat for fishers can be considered to have a high degree of diversity and interspersion.
Fishers generally use areas that support a suitable and diverse prey base and the best areas are those
that are comprised of a variety of habitats.
Fishers are generalized predators and opportunistic foragers that use a diversity of prey types and have
the capacity to take advantage of alternate foods as preferred foods change in relative abundance (Banci
1989, Arthur et al. 1989, Powell et al. 1997). Food items often include snowshoe hare, porcupines,
squirrels, mice, shrews, various fruits, and carrion (Arthur et al. 1989, Martin 1994, Powell et al. 1997).
Fishers are unique in that they are the only predator to consistently prey on porcupines, which can be an
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important food source. Several studies in eastern United States suggested that males may kill more
porcupines whereas females fed more on squirrel-sized prey (Arthur et al. 1989, Powell et al. 1997).
Fishers use dens for resting, thermal, security and reproducing activities. A variety of structures are used
for resting dens, including nests in branches, growths caused by broom rusts in hybrid spruce trees,
squirrel and raptor nests, ground / slash pile sites, tree cavities, under coarse woody debris and ground
burrows (Weir 1999, Arthur 1989). Natal dens where fishers raise their kits are very specific in structure
for thermal protection of the kits, protection of the kits from adult males and from predators. Natal dens
have been described as cavities in large, dead or decadent trees 7-12 m above the ground (Banci 1991).
Maternal (post-natal) dens are often used as the rearing season progresses (Powell et al. 1997, Weir
1999). The number of maternal dens used and frequency of moves is likely related to the availability of
suitable denning opportunities (Weir 1999). Weir (1995) found that large cottonwoods may be a critical
habitat component for maternal dens in south-central BC and in north-central BC (Weir 1999).
Male and females are sexually mature at one year of age; however, first litters occur in the females
second year due to delayed implantation (Banci 1989). Mating occurs in the spring just after females give
birth and implantation does not occur until the fall and is dependent on the condition of the female.
Average litter size is between 2-3 with a range of 1-4 (Douglas and Strickland 1987, Banci 1989).
Fishers occur primarily in forested landscapes and often prefer late-successional forests to younger seral
stages. In western coniferous forests, fisher may rely on the structures and ecological processes
associated with late successional stands to fulfill many of their life requirements (Weir and Harestad
1997). Studies of habitat use by fishers have occurred primarily within coniferous or mixed-wood habitats
in eastern North America (Banci 1989) and most suggest that fishers avoid open, hardwood-dominated
forests. Structure at the ground level appears to be an important component of stands, regardless of
stand age. There is a strong preference for riparian and riparian associated habitats (Cannings et al.
1999). In Maine, fishers preferred mature spruce-fir forests and used conifer-hardwood forests less than
available (Arthur et al. 1993).
Badry et al. (1997) found that fishers in the aspen parkland of Alberta used deciduous stands more than
expected based on availability. Areas with good overhead cover are thought to be good habitat,
especially in the winter by reducing the accumulation of snow, which is thought to restrict movements of
fishers (de Vos 1952 from Badry et al. 1997, Krohn et al. 1997). Forest stands (Allen 1983 from Badry et
al. 1997) with a well developed and diversified canopy and high DBH are important habitat factors.
Preferred use of deciduous dominated stands in the aspen parkland differs from the conclusions found in
the eastern United States in which deciduous dominated stands were avoided (de Vos 1952, Arthur et al.
1989, Buskirk and Powell 1994, Buck et al. 1994). Badry et al. (1997) found that the density of woody
stems in the understory is an important parameter that should not be overlooked in the identification of
fisher habitat as well as considering overstory type and density. Buskirk and Powell (1994) state that the
physical complexity near the forest floor may affect fisher habitat choices indirectly. Complex physical
structure in forests affects fisher habitat choices through the habitat choices of snowshoe hares. In the
boreal forest of Alberta, fisher prefer the older treed habitats for the higher canopy cover and for the
downed and dead logs and standing snags for resting and sites and natal cover (Lieffers and Woodard
1997). Fishers appear to benefit more in the boreal forest from highly diverse habitats or a variety of
microhabitats within older stands.
A study in north-central Idaho (Jones and Garton 1994) found that the dependence of fisher on latesuccessional forests was not as significant as was found in studies further east. Jones and Garton (1994)
found that fisher frequently used young forests in both winter and summer. In summer, younger-aged
forests were suitable for hunting but were rarely used for resting sites. More structurally complex stands
were used for both hunting and resting, but simpler stands were only used for hunting. Jones and Garton
(1994) found that although fishers preferred young forests in winter, they selected localities with higher
availability of large-diameter trees, snags, and logs. Thus, even though many sites used in winter were
classified as young forests, they contained several attributed commonly associated with older forests.
It has been widely documented that fishers will avoid open areas (Buskirk and Powell 1997, Krohn et al.
1997). Buskirk and Powell (1997) present several hypothesis as to why fishers go to such extreme
measures to avoid open areas; however none really explain this behaviour because fisher have very few
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predators, do not hunt by the pounce method used by canids and their foraging style cannot be fully
explained by an avoidance of open areas. A study by Powell and Zielinski (1994 from Powell et al. 1994),
found that fishers avoid large openings, recent clearcuts, open hardwood forests, grasslands and areas
above timberline. In south-central British Columbia, Weir (1995) found that fisher preferred lodgepole
pine forests with 21% to 60% canopy closure and avoided cultivated fields, herb seral stage stands, open
water, deciduous stands, selectively logged mixed stands and forest stands with low coarse woody
debris. In Manitoba (Leonard 1980 from Weir 1995), found that fishers avoided open bogs, but would use
them in winter once the snow surface had a supportive crust.
Arthur (1987 from prelim. Fisher species account) states that fishers can probably live in any area where
there is a sufficient diversity of forested land, including some coniferous cover, and that other factors,
such as prey abundance, climate and competition from other predators may be more important than
forest type in determining fisher distribution. Habitat use by fishers is limited to regions and elevations
that do not experience deep snow conditions, which restrict fisher movements. Due to the fisher’s diverse
diet, specific habitat selection may be more dependent upon the availability of resting and denning sites
than on forage opportunities (Powell and Zielinski 1994 from Powell et al. 1994). Limiting habitat for
fishers may be maternal denning habitat that is in close proximity to feeding habitat.
Fishers are territorial and solitary animals. In British Columbia, over the entire year, the adult male fisher
generally has a larger home range size (20-34 km2) than the female (15-19 km2) (Banci 1989). Home
ranges are exclusive within each sex, with females and males overlapping extensively (Arthur 1987;
Cannings et al. 1999). Females’ home ranges will generally vary little throughout the year in size and
location; adult males, however, will abandon their territories during the breeding season to search for
females in heat.
In north-central British Columbia, Weir (1999) found that the home range size of male fishers (sample size
one) was larger than those of the female fishers. The mean home range size of females was 49.9 km 2
whereas that of the male was 281.8 km 2. The core area of females (10.1 km 2) was smaller than the core
area of the male (60.1 km2). It was also found that the home range size of females was smaller in the
summer versus the winter, the home range size of females with kits was smaller than that of females
without kits, and reproducing females who had summer ranges that included extensive floodplain
ecosystems had smaller home ranges than the female whose summer home range did not include these
ecosystems (Weir 1999). Badry et al. (1997) found that in the aspen parkland of Alberta, that even
though the mean annual home range of females (14.9  3.5 km2) was smaller than that of males (24.3 
11.1 km2), they did not significantly differ in size. They did find that home range sizes decreased
significantly when the temperature dropped below zero degrees.
In Ontario, de Vos (1952) found that foraging fishers move in circuits that are covered in three to fifteen
days. The radius and length of the foraging circuit varied dependent on food availability and the sex of
the animal, with males completing larger circuits. In Maine (Arthur 1987 from prelim. fisher species
account), found that female home ranges were between 8.1 and 39.1 km 2 (mean 16.3km2) and male
home ranges were between 10.6 and 78.2 km 2 (mean 30.9 km2). The female home ranges were
generally stable in size and location throughout the year and minor shifts in female home range only
occurred when females avoided home ranges of other females or expanded ranges into territories left
vacant by the trapping of other females. Other areas reported home range sizes of 15 km 2 for female
fishers and 40 km2 for male fishers across multiple studies (Powell and Zielinski 1994), 6.6 to 39.6 km 2 in
New Hampshire and 15 to 19 km 2 in Michigan (Powell 1982 from Arthur 1987).
Juvenile home ranges are larger than adults and are considered temporary (Leonard 1980 in Banci 1989,
Arthur et al. 1993). Juvenile female fishers tend to establish home ranges that are in relatively close
proximity to their natal home ranges (Banci 1989).
Food/cover Life Requisites and Habitat-uses
Habitat Requirements Summary
Exact habitat requirements of fishers in the Morice and Lakes Forest Districts and in the SBS, ESSF, MH,
and CWH biogeoclimatic zones in this area have not been extensively studied and there is insufficient
inventory and ecological information for these areas to conclusively define habitat use and population
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Fisher Winter Habitat Model DRAFT
trends. Habitat use by fisher in other parts of British Columbia, western North America and then eastern
North America can be extrapolated to supplement the available information for these areas. Table 1
outlines habitat requirements for fisher in the study area.
Table 1. Summary of habitat requirements for Fisher in the study area.
Life Requisite
Season
Specific Attributes Required
Structural
Stages
Reproducing
Winter
- cavities in large living and dead trees of minimum 51cm
diameter at 5m height
5, 6 and 7
- adjacency to maternal den sites and feeding habitat
- high levels of CWD
Living (Feeding,
Security, Thermal,
Denning)
Winter
- mature conifer dominant forests with some deciduous
present for cavity denning opportunities
5, 6 and 7
- canopy closure >30% for snow interception
- high levels of CWD for resting sites, travel and foraging
- dense understory (high value snowshoe hare habitat)
- high habitat diversity including riparian areas and edges
Living (Feeding,
Security, Thermal,
Denning)
Growing
- high levels CWD for resting sites, travel and foraging
5, 6 and 7
- large trees for denning sites
(some 3 and 4)
- high habitat diversity including riparian areas and edges
Seasons of Use
Fishers are regionally rare, year-round residents of the study area. For the fisher, ecosystem ratings are
applied individually to the growing season (spring, summer, and fall) and the non-growing season (winter)
due to seasonal variation in habitat use to fulfill fisher life requisites (See Table 2). Ratings are applied to
the life requisite of Living for both seasons.
Table 2. Life requisites by month and season for fisher in the project area.
Month
Season
Life Requisites
January
Winter
Living (Food, Security, Thermal, Denning)
February
Winter
Living (Food, Security, Thermal, Denning, Reproducing)
March
Winter
Living (Food, Security, Thermal, Denning, Reproducing)
April
Winter
Living (Food, Security, Thermal, Denning, Reproducing)
May
Growing (spring)
Living (Food, Security, Thermal, Denning)
June
Growing (spring)
Living (Food, Security, Thermal, Denning)
July
Growing (summer)
Living (Food, Security, Thermal, Denning)
August
Growing (summer)
Living (Food, Security, Thermal, Denning)
September
Growing (fall)
Living (Food, Security, Thermal, Denning)
October
Growing (fall)
Living (Food, Security, Thermal, Denning)
November
Winter
Living (Food, Security, Thermal, Denning)
December
Winter
Living (Food, Security, Thermal, Denning)
*Seasons defined for Sub-Boreal and Central Interior Ecoprovinces per the Chart of Seasons by
Ecoprovince (BC WHAS 1999).
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Living During Winter
Feeding Habitat – Winter
The composition and breadth of the fisher’s winter diet are important for understanding and predicting
effects of habitat alteration on the feeding ecology and therefore individual and population responses to
changes in habitat structure (Weir 1995). Fishers are opportunistic feeders and their principal food items
are associated with their preferred habitat (Douglas and Strickland 1987). As well as preferred food
items, fishers are known to consume carrion as well as plant materials such as fruits, nuts, and berries.
Arthur (1983, Arthur et al. 1989) found that apples were the most prevalent food item in the diet of fishers
in Maine; this was attributed to the large number of abandoned farms in Maine and the availability of
apples throughout the winter. In winter diets, snowshoe hare and sciurids generally increase whereas
moles, shrews, fruit decrease (Banci 1989); however, the relative contribution of prey items appears to
vary geographically (Martin 1994). Martin (1994) found that fisher diets in the eastern United States had
the greatest diversity (based on the Shannon diversity indices) and those in the Midwest and west had
the lowest diet diversity. Martin (1994) also summarized the type of prey regionally and found that fisher
in eastern United States typically had small food items or ungulate carrion whereas fisher in the Midwest
and western studies showed that snowshoe hare and porcupine were the more frequently found food
item.
Weir (1995) found that snowshoe hare was the most frequent diet item in the stomachs of fisher
examined from central British Columbia. The next common items in order of abundance were red
squirrels, southern red-backed voles, and porcupines. Weir (1995) found that fishers in British Columbia
consumed a wider diversity of food species than did fisher in other areas (Martin 1994). Martin (1994)
had noted that diet diversity indices decreased with increasing occurrence of snowshoe hares in fisher
diets; however, even in peak snowshoe hare years, the diversity in stomach contents in central British
Columbia did not significantly decline. Fishers in British Columbia tended to consume more moose
carrion than deer carrion (Powell et al. 1997).
The relative ‘catchability’ of potential prey (Buskirk and Powell 1994) during the winter will influence diet
composition and thus the habitats in which fishers are able to successfully hunt for prey. Snow depth and
snow consistency can significantly affect fisher activity and habitat use for feeding. The fishers large
body size, in comparison to the American marten, precludes this species from hunting during snow
conditions that are deep and soft (Weir 1995, Martin 1994). Snow conditions may be a critical factor in
explaining why martens are in locations where fishers are not (Krohn et al. 1997). The lack of fishers in
coastal habitats is likely due to winter conditions of deep, wet snow that rarely forms an upper crust on
which to travel (Banci 1989).
Security/Thermal/Denning Habitat – Winter
Fishers use similar denning structures and locations in the winter as in the growing season; however, the
function for thermal cover becomes much more important in the winter. In northern-Wisconsin (Gilbert et
al. 1997), fisher winter rest sites were all underground, under woody material or in standing trees with a
preference for standing trees.
Reproducing (Birthing)
There is limited information available regarding the reproduction of fishers in British Columbia. There are
several sources of information from captive female fishers in Maine and some information on natal and
maternal den sites in New England. There is a small amount of information regarding reproduction of
fisher in British Columbia; however, there is some information on denning habitat collected by Weir (1999)
in north-central BC and in central BC (Weir 1995).
Most females’ breed for the first time at 12 to 15 months of age (Douglas and Stickland 1987) but due to
delayed implantation, their first kits are not born until two years of age. Delayed implantation may allow
the females the option of interrupted pregnancy if the animal is in poor condition. Litter sizes are typically
small and Frost and Krohn (1997) found that a mean litter size was between two to three kits. Most
females are reproductive every year after and breed almost immediately after kits are born. During
mating, males travel extensively outside of their home ranges to mate with several females; however, it is
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unknown as to whether females will mate with more than one male. Juveniles typically stay within the
natal home range until about four or five months of age and then disperse in late summer to early fall
(Banci 1989). Arthur et al. (1993) found that juveniles did not disperse until the late fall or early winter
and typically only traveled 1-3 times the distance from the natal home range (Arthur et al. 1993).
The date of parturition varies with local conditions and can occur anytime from mid-February to mid-April
(Douglas and Strickland 1987, Frost and Krohn 1997, Powell et al. 1997). Frost and Krohn (1997) found
that parturition occurred for captive fishers in Maine between March 3 and April 1. These dates were
within the range reported for wild fishers in Maine by Paragi et al. (1996 from Frost and Krohn). In northcentral British Columbia, Weir (1999) found that females started utilizing natal dens from March 30 to April
19. It is suggested in Frost and Krohn (1997) that photoperiod may synchronize implantation within a
population and since day length varies with latitude, implantation may also vary with latitude.
Female fishers raise their young in secure den sites without male contribution. Selection of natal den
sites is important because female fishers leave their young unattended for long periods, during which time
the young are vulnerable to predators and to male fishers (Banci 1989). In New England (Powell et al.
1997), white pine and eastern hemlock were the prevalent tree species used for maternal dens. In Maine
(Paragi et al. 1996 in Powell et al. 1997) fishers mostly used hardwoods for maternal dens. Both the
study in New England and in Maine found that at least 50% of maternal den locations were in dead trees,
which may be more likely to provide large cavities for denning. In south-central British Columbia, Weir
(1995) found that most maternal dens were located in cavities of branches of black cottonwoods. Dens
occurred at a mean height of 25.9 m above the ground in cottonwood trees with 103 cm mean dbh. Den
sites were found to be in areas of forest with large diameter coarse woody debris volumes greater than
the surrounding forest.
FISHER WINTER HABITAT MODEL
The fisher winter habitat model was initially developed as a compostite of potential denning (natal and
maternal) sites with foraging habitat. In the preliminary external review process of the winter habitat
model, maternal or natal denning structure was identified as the critical factor for fisher in the study area
and foraging habitat as not limiting. Therefore, we opted to restrict the current model to maternal and
natal denning habitat until we had the time to incorporate a spatial evaluation of foraging habitat with
respect to the location and value of denning structure. The following section describes the fisher denning
habitat model.
Application of Model
Season:
Natal and Maternal Denning (late winter)
Habitat Areas:
All landscape units in the Morice and the Lakes forest districts in central British
Columbia.
Model Output:
The model will produce a most probable suitability value for fisher maternal and
natal denning habitat in winter.
Verification Level:
Verification of the model involved testing the belief net to ensure that the output
is consistent with our expected output. A working review of the model was done
with Doug Steventon (MoF) and Don Reid (MSRM).
Assumptions
The following section describes the logic and assumptions used to translate habitat variable information
for fisher to the variables and equations used in the maternal and denning habitat model.
1. The availability of water is not a limiting component of fisher habitat.
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2. Assume that thermal requirements will be fulfilled in good foraging and denning habitats.
3. Fishers are not affected by proximity to human settlements, roads, or other activities in this model.
4. The limiting factor to healthy fisher populations in this area is the availability of suitable maternal
denning structure.
5. Structural stage 7 (old-growth) is assumed to provide the most suitable habitat for fishers, but forests
of structural stage 5 (young forest) and 6 (mature forest) that possess similar structural attributes of
old-growth, including large dead and damaged trees, high canopy closure and abundant large
diameter CWD, are considered to be equally suitable.
6. Structural stages 1 – 3 (non-vegetated/sparse to tall shrub) are limited value to fishers for resting and
denning sites due to the lack of canopy closure and low CWD.
7. Structural stage 4 (pole sapling) is assumed to be sufficiently lacking in specific habitat attributes
required by fisher to be considered of significantly less value than stands of higher structural stages.
8. ESSFmc, ESSFmk, and CWHws2 are considered lower value than SBSmc2, SBSdk and the
SBPSmc due to deeper and in the case of the ESSF sites, a more persistent snow pack. The
ESSFmc and mk also lack many large cottonwoods which are assumed to be preferred denning tree
species.
9. The SBSmc2 is assumed to have more better quality denning opportunities than the SBSdk but is not
rated higher than the SBSdk due to less snow in the dk versus the mc2, even though the SBSmc2
has larger trees and CWD is more abundant.
10. Desirable structural attributes such as coarse woody debris, large decaying and dead trees and high
shrub cover are assumed to be somewhat correlated with high structural stage.
11. Because fisher appear to prefer large diameter cottonwood for denning, it would be plausible to use a
two-tiered system for identifying good habitats. Predictive Ecosystem Maps (PEM) could be used to
mark good habitat and within these marked polygons, sites with a forest cover label with cottonwood
of structural stage 5, 6 or 7 could be identified as best potential denning habitat.
12. ESSFmv3 comprises only a small area east of Babine Lake and is considered similar to the ESSFmc
(Banner et al. 1993).
13. SBSwk3 comprises a small area adjacent to the Prince George Forest Region and is considered
similar to the SBSmc2.
14. Non-forested areas are generally used less and only for feeding opportunities.
15. Non-vegetated areas and alpine tundra are not used due to lack of food resources and forest cover.
16. Avalanche tracks are generally not used due to lack of forest cover.
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Fisher Denning Model Description
Fisher maternal and natal denning habitat is assumed to be a critical habitat type for fisher in the study
area. The following section details this model.
Riparian or Wetland Buffer?
Yes
50.0
No
50.0
0.5 ± 0.5
Ac Ecosystem Potential
Nil
25.0
Low
25.0
Moderate
25.0
High
25.0
Cottonwood
Present
50.0
Absent
50.0
Ecosystem Potential
Nil
25.0
Low
31.3
Moderate
18.8
High
25.0
B
Maternal Denning Habitat
Nil
25.0
Poor
38.1
Moderate
17.3
Good
19.5
Figure 1. Habitat variables and ecological relationships used to build the fisher maternal denning habitat
suitability Bayesian belief model in the Netica© program.
A
Description of Network Nodes
Maternal Denning Habitat
The value of a particular habitat to fisher for providing maternal or natal denning structure is evaluated in
this node (See Table 3). It was assumed that the value of maternal or natal denning habitat is closely tied
to the presence of large black cottonwood trees in the canopy. The presence of cottonwood in the stand
and not the abundance of the cottonwood was used as an indicator of suitability for denning.
Example Relationship:
Conditional Probability Table
Variables:
Den = Maternal denning habitat rating
Ac = Presence or absence of cottonwood in the forest cover tree species
Potential = Ecosystem potential as a cottonwood site
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Table 3. Conditional probabilities used within Netica© to configure the relationship between the reported
presence of black cottonwood (Ac) in the polygon and potential of the ecosystem as a
cottonwood site in describing maternal denning habitat suitability for fisher.
Maternal Denning Habitat Value
Cottonwood?
Ecosystem Potential
Nil
Poor
Moderate
Good
Present
Nil
100
0
0
0
Present
Low
0
50
50
0
Present
Moderate
0
0
25
75
Present
High
0
0
0
100
Absent
Nil
100
0
0
0
Absent
Low
0
100
0
0
Absent
Moderate
0
90
10
0
Absent
High
0
50
50
0
Cottonwood
This node reports the presence or absence of cottonwood in the forest cover database (species 1 through
to species 5).
Variable:
Ac = Presence or absence of cottonwood in the forest cover tree species
Ecosystem Potential
The potential of an ecosystem to support cottonwood trees is evaluated in this node. The factors that
influence this potential are the type of ecosystem (based on PEM-site series), the age of the
(structural stage) and if the ecosystem is located in a riparian influenced location on the
landscape (See
Figure 2).
Example Relationship:
Conditional Probability Table
Variables:
Potential = Ecosystem potential as a cottonwood site
Ac_ECO_Pot = Cottonwood ecosystem potential
R_Buffer = Located in a riparian or wetland buffer?
Ecosytem Potential for Riparian or
Wetland Habitats
100%
100%
75%
75%
Probability
Probability
Ecosytem Potential for Non-riparian or
Wetland Habitats
50%
25%
0%
50%
25%
0%
Nil
Low
Moderate
High
Potential for Cottonw ood in the Habitat
Nil
Low
Moderate
High
Nil
Low
Moderate
High
Potential for Cottonw ood in the Habitat
Nil
Low
Moderate
High
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Figure 2. Conditional probabilities used within Netica to configure the relationship between riparian and
wetland buffers and the potential of the ecosystem to grow cottonwood trees.
Riparian or Wetland Buffer?
The riparian or wetland buffer node is a yes/no node that is a lookup from a layer created from the
resultant file. This node influences site conditions and sites in these buffers are predicted to increase the
probability of the presence of black cottonwood. Table 4 lists the riparian and wetland types that were
buffered to create this layer and the buffer size for each feature included.
Variable:
R_Buffer = Located in a riparian or wetland buffer?
Table 4. Riparian and wetland buffers included in the fisher riparian file as influencing the potential
presence of black cottonwood.
Lake, River, Wetland Code
Description
Buffer Size
L1
Lake greater than 5ha
10m
L3
All other lakes in study area
30m
S1
Fish stream, > 20m stream width
50m
S2
Fish stream, > 5-20m stream width
50m
W1
Wetland greater than 5ha
50m
W5
Wetland Complex
50m
W3
All other wetlands in study area
30m
Ac Ecosystem Potential
The Ac ecosystem potential node is input from a lookup table listing the ratings of site series by structural
stage as potential cottonwood bearing sites. In general, sites that are mature to old structural stage and
typically support Ac are the best potential sites. These include a few upland site series and several of the
floodplain site series. Herb_shrub sites have no potential. Forested floodplain site series within the
SBSdk at the pole/sapling stage have a moderate potential to grow black cottonwood large enough to
influence fisher maternal denning habitat value.
Variable:
Ac_ECO_Pot = Cottonwood ecosystem potential
Fisher Winter Foraging Habitat Description
Winter foraging habitat for fisher was originally developed for the Morice and Lakes forest districts to be
used in an overall late winter model including both denning and foraging habitat. The following section
describes how the foraging portion of the model (See Figure 3) was developed and the structure of this
portion of the model. Currently, foraging is not included in the evaluation of fisher habitat due to time
constraints, as this would require a spatial analysis of foraging habitat andmaternal denning habitat.
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Large CWD Volume
Nil
25.0
Low
25.0
Moderate 25.0
High
25.0
Understory Potential
Nil
25.0
Low
25.0
Moderate 25.0
High
25.0
Snow Depth
Shallow
33.3
Moderate 33.3
Deep
33.3
0.417 ± 0.42
Riparian or Wetland Buffer?
Yes
50.0
No
50.0
0.5 ± 0.5
Crown Closure Class
0 to 3 33.3
3 to 7 33.3
>= 7
33.3
A
Accessibility
Low
43.3
Moderate 27.8
High
28.9
Forage Forest Attributes
Nil
43.8
Poor
22.2
Moderate 20.0
Good
14.1
Winter Forage Habitat
Nil
43.8
Poor
39.7
Moderate 12.5
Good
4.06
Figure 3. Habitat variables and ecological relationships used to build the fisher winter foraging habitat
B
suitability Bayesian belief model in the Netica©
program.
Description of Network Nodes
Winter Foraging Habitat
The winter foraging habitat node evaluates the value of the habitat attributes for supporting suitable prey
(forage forest attributes) and the ability of fisher to access the habitat and to successfully hunt in the
habitat (accessibility). Table 5 outlines the value of the habitat based on forage (as predicted by forest
attributes) and access to forage.
Example Relationship:
Conditional Probability Table
Variables:
WFH = Winter forage habitat
SF = Forage forest attributes
ACCESS = Accessibility (to forage forest attributes)
Table 5. Conditional probabilities used within Netica to configure the relationship between forage forest
attributes and accessibility of fisher to forage attributes.
Winter Forage Habitat
Forage Forest
Attributes
Accessibility to
Forage
Nil
Low
Moderate
High
Nil
Low
100
0
0
0
Nil
Moderate
100
0
0
0
Nil
High
100
0
0
0
Low
Low
0
100
0
0
Low
Moderate
0
100
0
0
Low
High
0
100
0
0
Moderate
Low
0
100
0
0
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Moderate
Moderate
0
50
50
0
Moderate
High
0
0
100
0
High
Low
0
100
0
0
High
Moderate
0
0
100
0
High
High
0
0
0
100
Accessibility
The accessibility node describes the ability of fisher to access a habitat in winter. This node is defined by
the relationship between snow depth and crown closure. A deep and persistent snow pack will hinder
access to a site in winter, even with the moderating effects that a closed canopy forest can have on the
underlying snow conditions. Shallow snow conditions will not discernably hinder fisher movement,
whereas moderate snow levels will impede fisher movements; however, the level of affect will depend on
other factors such as forested canopy cover.
Example Relationship:
Conditional Probability Table
Variables:
ACCESS = Accessibility (to forage forest attributes)
CRNCL_CL = Crown closure class
SD = Snow depth (rating)
Table 6. Conditional probabilities used within Netica© to configure the relationship between snow depth
and crown closure class in defining the ability of fisher to access a habitat.
Snow Depth
Accessibility
Crown Closure
Class
Low
Moderate
High
Shallow
0–3
0
50
50
Shallow
3–7
0
0
100
Shallow
>7
0
0
100
Moderate
0–3
90
10
0
Moderate
3–7
0
100
0
Moderate
>7
0
90
10
Deep
0–3
100
0
0
Deep
3–7
100
0
0
Deep
>7
100
0
0
Snow Depth
The snow depth node is a parent node whose value has been summarized from snow station data and
BEC guidebook data into mean late winter snow depth by subzone. This node has the potential values of
shallow (0 – 50cm), moderate (50 – 150cm), and deep (150+cm).
Variables:
SNOW = Snow depth rating by BEC subzone
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Crown Closure Class
The coverage of the canopy can affect the quality and depth of snow under that canopy. An interlocking
crown intercepts snow and therefore reduces the depth of snow on the ground. A second effect of snow
being intercepted is that when the snow falls from the canopy in clumps, it can often compress and be
more hard packed than if it had fallen directly on the ground. Both of these effects will facillitate the ability
of fisher to move about in closed canopy forests – at low to moderate snow levels. Both of these effects
are related to older forests with high crown closure and are not as effective in young, dense stands.
Variables:
CRNCL_CL = Crown closure class (forest cover attribute)
Table 7. Ratings of crown closure class on accessibility to habitats of fisher in the Morice and Lakes
forest districts.
Crown Closure Class
% Cover
Fisher Model Rating
0–3
0 – 25%
Low
3-7
26 – 65%
Moderate
>7
66%+
High
Forage Forest Attributes
The forage forest attributes is a rating of the ability of the habitat type to support prey populations
important for fisher in winter and during denning. This node evaluates the structure in a habitat type and
whether it has riparian features. Structure at the ground level appears to be an important feature for
fisher. In this node, the ecosystem and structural stage (understory potential) rating and volume of large
coarse woody debris represent ground level structure. If the habitat type is within an identified riparian
buffer zone then the potential productivity of the site increases. See Table 8 for a summary of forage
forest attributes value. Note that for sites with Nil for either understory potential or large coarse woody
debris volume, the forage forest value is Nil.
Example Relationship:
Conditional Probability Table
Variables:
SF = Forage forest attributes
LG_CWD = Large coarse woody debris
F_F_POT = Understory Potential (Ratings Lookup table)
R_Buffer = Riparian or wetland buffer?
Table 8. Conditional probability of the value of forage forest attributes given the understory structure,
volume of large coarse woody debris and presence of riparian features.
Riparian or
Wetland?
Understory
Potential
Large CWD
Volume
No
Low
No
Forage Forest
Poor
Moderate
Good
Low
100
0
0
Low
Moderate
100
0
0
No
Low
High
100
0
0
No
Moderate
Low
70
30
0
No
Moderate
Moderate
30
70
0
No
Moderate
High
0
100
0
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No
High
Low
0
70
30
No
High
Moderate
0
20
80
No
High
High
0
10
90
Yes
Low
Low
100
0
0
Yes
Low
Moderate
90
10
0
Yes
Low
High
70
30
0
Yes
Moderate
Low
50
50
0
Yes
Moderate
Moderate
0
100
0
Yes
Moderate
High
0
90
10
Yes
High
Low
0
50
50
Yes
High
Moderate
0
10
90
Yes
High
High
0
0
100
Understory Potential
Fisher requires structure at the ground level, not only for hunting prey but to support prey populations.
The understory potential node is a parent node that is read in from a ratings lookup table. The ratings are
based on the ecosystem type (biogeoclimatic subzone and site series) and the structural stage. The
rating is based on an interpretation of the level of vegetative structure in each combination of site series
and structural stage. Most of this information was obtained from “A Guide to Site Interpretation and
Identification of the Prince Rupert Forest Region” (Banner et al. 1993). Vegetation lists and relative
abundance tables were used to predict vegetation structure for mature stands; while vegetation potential
and complexes under silviculture were used to to predict vegetation structure for the herb and shrub
stages.
Variables:
F_F_POT = Understory potential (Ratings Lookup table)
Large Coarse Woody Debris
Large coarse woody debris (>20cm DBH) adds structure to the ground level and supports small mammal
populations.
Variables:
LG_CWD = Large CWD volume
Riparian or Wetland Buffer
This variable is the same as in the fisher maternal denning model; however, it is interpreted differently
when used as a foraging habitat variable. Riparian habitats tend to support richer and/or more productive
understories; therefore, sites that are adjacent to streams, lakes and wetlands are rated as potentially
better foraging sites. Each habitat is either yes riparian or wetland buffer or no. This buffer identifies
smaller foraging habitat features that cannot be inferred from the PEM because they are either smaller
then the PEM polygons, and/or, are not the dominant site series within a PEM polygon.
Variables:
R_Buffer = Riparian or wetland buffer?
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Computing Output for Habitat Value
Non-spatial fisher denning (maternal and natal) habitat will be the output from the model for each grid cell.
An assessment of the spatial pattern, or configuration, of the habitat on the landscape needs to be
completed to be able to appropriately interpret habitat value for female fisher during denning. The
response of fisher to the configuration of habitat types in the Morice and Lakes forest districts is not well
understood; therefore, the exploration of the influence of the spatial affect of denning and foraging habitat
on fisher would be preliminary until this was better understood for the study area.
Sensitivity Analysis
The fisher maternal and natal denning habitat suitability belief model was examined to assess the
sensitivity of findings of dependent nodes on input (parent) nodes. This test of sensitivity is conducted
within Netica© and is a relative indication of the influence of parent nodes on the findings in the child or
output node. The results of this testing allow us to evaluate whether the BBN is working how we expect it
to, and/or gives insight into relative weighting of variables. Depending on the type of nodes that are
involved in each test, the sensitivity is either given as the value ‘mutual info’ or as ‘variance reduction’. In
both cases, the node with the largest value affects the output node that is being tested to the greatest
extent. The sensitivity values for the input nodes can be directly compared to assess the magnitude of
their effect on the output node in comparison to the tested parent (input) nodes.
It was expected that the presence of cottonwood in mature, low elevation habitat types would be the best
habitat for fisher denning. The prediction of maternal denning suitability was highly influenced by the
combination of structural stage and ecosystem type. Sites with high potential to contain cottonwood in a
mature stand were rated high potential. These sites had the best potential to supply suitable denning
structure.
Testing and Validation
The models should be viewed as hypotheses of species-habitat relationships rather than statements of
proven cause and effect relationships. Their value is to serve as a basis for improved decision making
and increased understanding of habitat relationships because they specify hypotheses of habitat
relationships that can be tested and improved. There are several levels at which the models should be
validated. The first is an ongoing process during model development during which we have tested the
model to ensure that it is acting in a manner that we want it to. The second level is to test the model
assumptions and output through field-testing or verification.
Testing of the models relationships and output is an ongoing iterative process concurrent with the
development of the BBNs. Development of the fisher denning and foraging habitat suitability models
occurred within Ardea – with several working reviews. These reviews entailed testing the model for
various scenarios, evaluating the relationships and ratings, testing the sensitivity of the model to habitat
variables, and adjusting the equations and tables to reflect fine-tuning. A working review of the model
and the model document was done in the summer of 2003 and suggested changes were incorporated
into the model.
Research Needs for Model Verification
The performance of a model should be tested against population data, preferably estimates of density or
reproductive success, to translate the perception of habitat quality or suitability into differential use of
habitat (Brooks 1997). The spatial configuration of habitat will affect the spatial spread and use of a
population in a heterogeneous environment (Söndgerath and Schröeder 2002). The output of this model
provides a denning habitat suitability value; however, the pattern and amount of the habitat with respect
to fisher use is not evaluated. The importance of the landscape structure varies according to the
demographic characteristics of the population (Söndgerath and Schröeder 2002, With and King 1999).
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The following are proposed initiatives and research needs to verify portions of the fisher denning habitat
model. Various levels of verification can occur to strengthen our confidence in the model output. The
input data, ratings lookup tables, relationships, and output can all be improved. Model output would be
most strengthened by verification of the following:

Coarse filter validation by site series and structural stage of:
o

Cottonwood presence/absence and characteristics (dbh, height etc)
Evaluation of moderate and high value habitats predicted in the model
 Tracking studies as an information gathering method to explore use in high and moderate value
habitats

Evaluation of denning habitat and surrounding landscape and stand features. This information could
then be used to evaluate effectiveness of habitats based on surrounding forage habitat, roads, and
disturbances (i.e. forest harvesting).
Development of habitat effectiveness and spatial evaluation of these output values to reflect habitat value
for fisher should be the next step. Layers and relationships that would be incorporated in this section are
partially developed and would need extensive review. Because there is limited information regarding
detailed habitat use, predation levels and demographic response to factors such as roads, recreational
use, and habitat fragmentation, we would rely on what information there is as well as information from
other areas that are more thoroughly studied.
Implications for Management
Some potential management implications to forest management are outlined in this section based on the
requirements for denning in the model. Fishers require mature forests that are spatially located in low
elevation stands, most often with riparian features. These types of forest on the landscape typically
experience development pressure from many sources such as forest harvesting, road building,
development (community, agricultural, etc), and recreation disturbance. Not only do fisher require mature
forests, but they require structure that is typical of unmanaged stands, namely large trees and snags.
Under short-rotation, even aged management, the forest matrix is unlikely to support fisher populations
without specific steps to maintain or create large logs and snags (Lewis and Stinson 1998). This could
potentially impact forest management by requiring longer rotation harvesting with a limited impact on the
stands with these characteristics on the landscape.
As well, Lyon et al. (1994:132), wrote that a landscape of mostly early successional stands and small
patches of mature forest is unlikely to provide suitable habitat for fishers. The spatial configuration of
habitat is likely to constrain the pattern of forest harvesting, especially with respect to the need for
denning habitat.
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REFERENCES
Allen, A.W. 1983. Habitat suitability index models: fisher. U.S. Fish Wildl. Sev., Biol. Services Prog.
FWS/OBS 82/10.45. 19pp.
Arthur, S.M., W.B. Krohn, and J.R. Gilbert. 1989. Home range characteristics of adult fishers. J. Wildl.
Manage. 53:674-679.
Arthur, S.M., T. Paragi, and W.B. Krohn. 1993. Dispersal of juvenile fishers in Maine. J. Wildl. Manage.
57:868-874.
Badry, M.J., G. Proulx, and P.M. Woodard. 1997. Home-range and habitat use by fishers translocated to
the aspen parkland of Alberta. Pages 233-251 in Martes: taxonomy, ecology, techniques, and
management. G. Proulx, H.N. Bryant, and P.M. Woodard, eds. Provincial Museum of Alberta,
Edmonton, Alta, Canada.
Banci, V. 1989. A fisher management strategy for British Columbia. BC Ministry of Environment. Wildlife
Bulletin No. B-63. Victoria, BC 117p.
Banner, A., W. Mackenzie, S. Haeussler, S. Thomson. J. Pojar and R. Trowbridge. 1993. A Field Guide
to Site Identification and Interpretation for the Prince Rupert Forest Region. Land Management
Handbook #26. BC Ministry of Forests.
Buck, S.G., C. Mullis, A.S. Mossman, I.Show, and C. Coolahan. 1994. Habitat use by fishers in adjoining
heavily and lightly harvested forest. Pages 368-376 in S.W. Buskirk, A.S. Harestad, M.G. Raphael,
and R.A. Powell, eds. Martens, sables, and fishers: biology and conservation. Cornell University
Press, Ithaca, N.Y.
Buskirk, S.W., and R.A. Powell. 1994. Habitat ecology of fishers and American martens. Pages 283296 in S.W. Buskirk, A.S. Harestad, M.G. Raphael, and R.A. Powell, eds. Martens, sables, and
fishers: biology and conservation. Cornell University Press, Ithaca, N.Y.
Cannings, S.G., L.R. Ramsay, D.F. Fraser, and M.A. Fraker. 1999. Rare amphibians, reptiles, and
mammals of British Columbia. Wildl. Branch and Resour. Inv. Branch, BC Minist. Environ., Lands,
and Parks, Vicotira, BC. 198pp.
de Vos, A. 1952. The ecology and management of fisher and marten in Ontario. Ontario Department of
Lands and Forests. 53p.
Douglas, C.W. and M.A. Strickland. 1987. Fisher. Pages 511-529 In: M. Novak, J.A. Baker, M.E. Obbard
and B. Malloch (eds). Wild furbearer management and conservation in North America. Min. of Nat.
Res., Toronto, Ont.
Frost, H.C., and W.B. Krohn. 1997. Factors affecting the reproductive success of captive female fishers.
Pages 100-109 in Martes: taxonomy, ecology, techniques, and management. G. Proulx, H.N. Bryant,
and P.M. Woodard, eds. Provincial Museum of Alberta, Edmonton, Alta, Canada.
Gilbert, J. H., J.L. Wright, D.J. Lauten, and J.R. Probst. 1997. Den and rest-site characteristics of
American marten and fisher in northern Wisconsin. Pages 135-145 in Martes: taxonomy, ecology,
techniques, and management. G. Proulx, H.N. Bryant, and P.M. Woodard, eds. Provincial Museum
of Alberta, Edmonton, Alta, Canada.
Jones, J.L., and E.O. Garton. 1994. Selection of successional stages by fishers in north-central Idaho.
Pages 377-387 in S.W. Buskirk, A.S. Harestad, M.G. Raphael, and R.A. Powell, eds. Martens,
sables, and fishers: biology and conservation. Cornell University Press, Ithaca, N.Y.
Krohn, W.B., W.J. Zielinski, and R.B. Boone. 1997. Relations among fishers, snow, and martens in
California: results from small-scale spatial comparisons. Pages 211-232 in Martes: taxonomy,
ecology, techniques, and management. G. Proulx, H.N. Bryant, and P.M. Woodard, eds. Provincial
Museum of Alberta, Edmonton, Alta, Canada.
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Leonard, R.D. 1980. The Winter Activity and Movements, Winter diet, and Breeding Biology of the Fisher
(Martes pennanti) in Southeastern Manitoba. M.Sc. Thesis, University of Manitoba. 181 pp.
Lewis, J.C. and D.W. Stinson. 1998. Washington State Status Report for the Fisher, pp. 1-64.
Washington Department of Fish and Wildlife, Olympia, WA.
Lieffers, V.J., and P.M. Woodard. 1997. Silvicultural systems for maintaining marten and fisher in the
boreal forest. Pages 407-418 in Martes: taxonomy, ecology, techniques, and management. G.
Proulx, H.N. Bryant, and P.M. Woodard, eds. Provincial Museum of Alberta, Edmonton, Alta,
Canada.
Martin, S.K. 1994. Feeding ecology of American marten and fishers. Pages 297-315 in S.W. Buskirk,
A.S. Harestad, M.G. Raphael, and R.A. Powell, eds. Martens, sables, and fishers: biology and
conservation. Cornell University Press, Ithaca, N.Y.
Powell, S.M., J.J. Scanlon, and T.K. Fuller. 1997. Fisher maternal den sites in central New England.
Pages 265-278 232 in Martes: taxonomy, ecology, techniques, and management. G. Proulx, H.N.
Bryant, and P.M. Woodard, eds. Provincial Museum of Alberta, Edmonton, Alta, Canada.
Powell, S.M., E.C. York, and T.K. Fuller. 1997b. Seasonal food habits of fishers in central New England.
Pages 279-305 in Martes: taxonomy, ecology, techniques, and management. G. Proulx, H.N. Bryant,
and P.M. Woodard, eds. Provincial Museum of Alberta, Edmonton, Alta, Canada.
Powell, R.A. and W.J. Zielinski. 1994. Fisher. In The scientific basis for conserving
forest carnivores: American marten, fisher, lynx and wolverine in the western United States. L.F.
Ruggiero, K.B. Aubry, S.W. Buskirk, L.J. Lyon and W.J. Zielinski (eds.). USDA For. Serv., Ft. Collins,
CO. Gen. Tech. Rep. RM-254. pp. 38-73
Weir, R.D. 1995. Diet, spatial organization and habitat relationships of fishers in south-central British
Columbia. M.Sc. thesis. Simon Fraser University. Burnaby, BC.
Weir, R.D., and A.S. Harestad. 1997. Landscape selectivity by fishers in south-central British Columbia.
Pages 252-264 in Martes: taxonomy, ecology, techniques, and management. G. Proulx, H.N. Bryant,
and P.M. Woodard, eds. Provincial Museum of Alberta, Edmonton, Alta, Canada.
Weir, R.D. 1999. Ecology of fishers in the sub-boreal forests of north-central British Columbia: Year III
(1998-1999) progress report: radiotelemetry monitoring. Peace/Williston Fish and Wildlife
Compensation Program Report No. 206. 39pp plus appendices.
Weir, R.D., in prep. Status of Fishers in British Columbia. Prepared for the Minist. of Water, Land and Air
Protection and the Minist. of Sustainable Resource Management, Victoria, BC.
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Fisher Winter Habitat Model DRAFT
APPENDIX A: SUITABILITY RATINGS FOR SPECIES ACCOUNT
MORICE AND LAKES FOREST DISTRICT
Ratings
An intermediate knowledge level of the habitat requirements of Fisher in British Columbia is available;
therefore a 4-class rating scheme (Resource Inventory Committee 1999) was applied to the ecosystems:
High (H), Moderate (M), Low (L), and Nil (N).
Provincial Benchmark
Ecosection:
Caribou Plateau (CAP), Nazko Upland (NAU)
Biogeoclimatic Zone:
SBS and ESSF (CAP and NAU)
Habitats:
Mature stands of coniferous and mixed coniferous-deciduous forest
Provincial benchmarks at the ecosection and the ecosystem level are not established; however, Banci
(1989) states that the most productive fisher regions in the province are in the Nass Basin and Nass
Ranges. Highest densities of fisher will be associated with conifer-dominated forests with high canopy
closure and CWD interspersed by riparian areas and forested ridge lines.
Based on trapper harvest returns for the province, the coniferous forests in the Caribou Plateau (CAP)
and Nazko Upland (NAU) ecosections produce the greatest number of harvested fishers (ave. 1.44
fisher/10years/100km 2). Interpretation of harvest returns should be cautioned because there is a lack of
information on trapper effort or number of trappers and the results may indicate relative effort. The
Bulkley Ranges (BUR), within the study area, produces approximately 0.17 fisher/10years/100 km 2 and
the Nechako Uplands (NEU) ecosection produces approximately 0.38 fisher/10years/100 km 2, which are
both much lower than the provincial best areas.
Table 3. General habitat ratings for habitat types for fisher within the study area.
General Habitat Type
Assumptions
Various non-forested ecosystems
- non-forested areas are generally used less and only for feeding
opportunities
Various non-vegetated
ecosystems
- non-vegetated areas are not used due to lack of food sources and
forest cover
Various AT ecosystems
- alpine tundra not used due to lack of food sources and forest
cover
Avalanche tracks
- avalanche tracks generally not used due to lack of forest cover
Various forested ecosystems
(See following table)
Table 4. Assumptions made for SBSdk, SBSmc2, ESSFmc, ESSFmcp, ESSFmk, ESSFmkp, CWHws3, and AT
ecosystem ratings.
Ecosystem
Unit (Site
Series)
Winter Season
Growing Season
- low value habitat due to low snow interception, but
lower elevation sites with lower snow loads
- low value habitat due to low productivity sites with
few resting/denning opportunities, low canopy
closure and poorly developed herb layer
SBSdk
LJ
(02)
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Fisher Winter Habitat Model DRAFT
LC
(03)
BS, SS
(09, 10)
SP, SF
(01, 05)
DS
(04)
ST, SH
- low value habitat due to low snow interception, but
lower elevation sites with lower snow loads and
potential for some resting opportunities and thermal
cover
- low value habitat due to low productivity sites with
few resting/denning opportunities, low canopy
closure and poorly developed herb layer
- low to moderate for young to old-growth structural
stages due to low potential for resting/ denning sites,
low canopy closure but typically lower snow loads
and feeding opportunities
- low to moderate value for young to old-growth
structural stages due to feeding opportunities but low
canopy closure but few resting and thermal sites and
no denning opportunities
- moderate value for young to old-growth structural
stages due to moderately good canopy closure and
CWD, typically lower snow loads and potential for
feeding, thermal, resting and some denning
opportunities
- moderate value for young to old-growth structural
stages due to moderately developed herb layer for
snowshoe hare and some resting opportunities
-low value for young to old-growth structural stages
- low value habitat due to low productivity sites with
due to open canopy with low snow interception,
few resting/denning opportunities, low canopy
relatively unproductive forest but with relatively lower closure and poorly developed herb layer
winter snow load
- moderate to high value for young to old-growth
structural stages due to good potential for
resting/denning sites, typically lower snow loads and
higher canopy closure
- moderate to high value for young to old-growth
structural stages due to well developed herb layer for
snowshoe hare and resting/denning opportunities in
cottonwood
- moderate to high value for young to old-growth
structural stages due to good resting/denning
opportunities in productive mixed forest dominated
by black cottonwood and due to typically lower snow
load in subzone
- moderate to high value habitat due to good cavity
denning opportunities in large cottonwood and
spruce, moderate feeding opportunities and riparian
location
(31, 32)
- low value habitat due to lack of resting/ denning
opportunities, no snow interception but relatively low
snow load in subzone and feeding opportunities
especially along edges
- low value habitat due to lack of canopy closure,
resting/denning opportunities and thermal cover but
feeding opportunities
(81, 82)
- low value habitat due to lack of resting/ denning
- low value habitat due to lack of canopy closure,
opportunities, no snow interception but relatively low resting/denning opportunities and thermal cover but
snow load in subzone and south facing positions and some feeding opportunities
some feeding opportunities
(06, 07)
CD
(08)
SBPSmc
LC, BF, LF,
SB (02, 03,
01, 04)
-low value for young to old-growth structural stages
due to lower productive coniferous forest with few
denning opportunities, sparse herb and shrub layer
but moderate snow interception and drier subzone
- low value for young to old-growth structural stages
due to sparse herb/shrub layer and submesic to
xeric coniferous forest
BB, --
- low value habitat due to lack of resting/denning
opportunities, low snow interception but relatively
low snow load in subzone and some feeding
opportunities especially along edges
- low value habitat due to lack of canopy closure,
resting/denning opportunities and thermal cover but
feeding opportunities
- moderate value for mature to old-growth structural
stages due to good canopy closure, relatively low
snow load, cavity denning opportunities in spruce
and resting, thermal and feeding opportunities
- moderate value for young to old-growth structural
stages due to good canopy closure, well developed
herb layer and good resting sites
- low value for young to old-growth structural stages
due to relatively open canopy, few denning
opportunities but some snowshoe hare habitat
- low to moderate value for young to old-growth
structural stages due to moderate canopy closure,
partially developed herb layer but good resting sites
(07, 31)
SO
(05)
SH
(06)
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Fisher Winter Habitat Model DRAFT
(32)
- low value habitat due to lack of resting/ denning
opportunities, no snow interception but relatively low
snow load in subzone and some feeding
opportunities along edges
- low value habitat due to lack of canopy closure,
resting/denning opportunities and thermal cover but
feeding opportunities
- low value habitat for young to old growth stages
due to low snow interception and canopy closure
and low thermal/denning opportunities
- low value habitat for young to old growth stages
due to lower canopy closure and scarce herb layer
- moderate value habitat for young to old-growth
structural stages due to good feeding opportunities
and good snow interception
- moderate value for young to old-growth structural
stages due to well developed herb layer for feeding
opportunities, high canopy closure, and abundant
resting sites
- moderate value for young to old-growth structural
stages due to high CWD and a relatively dense
shrub layer, which provides both thermal habitat at
resting/den sites and good snowshoe hare habitat
- moderate value for young to old-growth structural
stages due to high canopy closure mixed stands with
large diameter trees resulting in abundant
resting/den and feeding opportunities
- moderate value for young to old-growth structural
stages due to low snow interception but good cavity
denning opportunities
- moderate value for young to old-growth structural
stages due to lower canopy closure and high value
herb layer for snowshoe hare
-low value from young to old-growth structural stages
due to lack of canopy for snow interception and
limited resting/denning opportunities with poor
thermal value
-low value for young to old-growth structural stages
due to low canopy closure in clumps of spruce
interspersed with shrubs. Some feeding
opportunities in open shrubby areas
SBSmc2
PH
(02)
SB, SD, SH
(01, 09, 10)
TC
(05)
SO
(06)
SS
(12)
BS, SF, WW, - no value due to lack of snow interception, no
WM
resting/denning sites and no thermal cover
-low value due to lack of tree cover resulting in few
resting sites, but some feeding opportunities in shrub
layer
ESSFmc
LC, FC
(02, 03)
HH
(04)
FB
(01)
FT
(05)
FO, FD
(06, 07)
FV
(08)
HG
(09)
low value due to relatively high snow pack, low snow
interception because low canopy closure and lack of
cavity denning opportunities because no
cottonwoods and very few large trees
- low value for young to old-growth structural stages
due to an open canopy of small pine and fir and
poorly developed herb/shrub layer for few feeding
opportunities and lack of snowshoe hare habitat
- low value for young to old-growth structural stages - low value for young to old-growth structural stages
due to relatively high snow load, relatively poor snow due to lower canopy closure and low prey
interception and lack of cavity denning opportunities abundance
- low value for young to old-growth structural stages - moderate value for young to old-growth structural
due to relatively high snow load, relatively poor snow stages due to a moderately open canopy but a fairly
interception and lack of cavity denning opportunities well developed shrub layer and CWD
- low value for young to old-growth structural stages - moderate value for young to old-growth due to very
due to relatively high snow load, relatively poor snow productive, moist sites with large diameter fir and
interception and lack of cavity denning opportunities spruce, abundant, large CWD and a diverse
herb/shrub layer
- low value for young to old-growth due to high snow
load, a moderately open canopy resulting in poor
snow interception
- moderate value for young to old-growth structural
stages due to better than average productive sites
with a well developed herb/ shrub layer and potential
resting/denning and feeding opportunities
- low value at all structural stages due to deep snow
load, low snow interception, low CWD, and harsh
climate
- low to moderate value for young to old-growth
structural stages in less productive sites due to
shorter snow free season and a harsher climate but
a well developed herb layer for snowshoe hare
- low value for young to old-growth structural stages
due to open forests resulting in poor snow
interception and few thermal/resting opportunities
- low value for young to old-growth structural stages
due to open forests resulting in poor snow
interception and few thermal/resting opportunities
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Fisher Winter Habitat Model DRAFT
FH
(10)
SP
- low value for young to old-growth structural stages
due to open forests resulting in poor snow
interception and few thermal/resting opportunities
-low to moderate value at young to old-growth
structural stages due to open, wet forests, but a well
developed herb and shrub layer for snowshoe hare
- no value due to low snow interception, few
resting/denning sites and little thermal cover
- low value due to low canopy closure, but some
feeding opportunities
BS, SF, WW, - no value due to lack of snow interception, no
WM
resting/denning opportunities and no thermal cover
- low value due to lack of tree cover, resulting in few
resting sites, but some feeding opportunities along
edges
ESSFmcp
-low value habitat due to lack of large diameter trees
providing no resting/denning opportunities and poor
snowshoe hare habitat.
-low value habitat due to deep snow, low canopy
closure and lack of large diameter trees.
ESSFmkp
AT
Preliminary Ratings Tables
The preliminary habitat ratings for caribou in the Morice and Lakes Forest Districts are listed in Table 5.
Table 5. Preliminary ecosystem and site series ratings for fisher habitat.
Ecosystem TEM Map
Unit
Code
Living – Winter Season
Living – Growing Season
Reproducing (birthing)
Structural Stages
Structural Stages
Structural Stages
1
2,3
4
5,6,7
1
2,3
4
5,6,7 1
2,3
4
5,6,7
SBSdk
02
LJ
N
N
L
L
N
N
L
L
N
N
N
N
03
LC
N
N
L
L
N
N
L
L
N
N
N
N
09, 10
BS, SS
N
L
L
M
N
L
L
L
N
N
N
L
01, 05
SP, SF
N
L
M
M
N
L
L-M
M
N
N
N
M
04
DS
N
N
L
L
N
L
L
L
N
N
N
N
06, 07
ST, SH
N
L
M
M
N
M
M
M-H
N
N
N
M-H
08
CD
N
L
L
M
N
L
M
M-H
N
N
N
M-H
N
L
L
L
N
L
L
M
N
N
N
N
SW, BW
N
N
N
N
N
L
L
L
N
N
N
N
02, 03, 01,
04
LC, BF, LF,
SB
N
N
N
L
N
L
L
L
N
N
N
L
07, 31
BB, --
N
N
L
L
N
L
L
L
N
N
N
N
05, 06
SO, SH
N
L
L
L
N
L
L
M
N
N
N
L
N
N
L
L
N
L
L
L
N
N
N
N
31, 32
81, 82
SBPSmc
32
SBSmc2
02
PH
N
N
L
L
N
L
L
L
N
N
N
N
01, 09, 10
SB, SD, SH
N
L
M
M
N
L
M
M
N
N
N
M
05
TC
N
L
M
M
N
L
M
M
N
N
N
M
06
SO
N
L
L
M
N
L
L
M
N
N
N
M
12
SS
N
N
L
L
N
L
L
L
N
N
N
N
Page 22
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Fisher Winter Habitat Model DRAFT
BS, SF, WW, N
WM
All others
N
-
-
N
L
-
-
N
N
-
-
N
-
-
-
N
-
-
-
N
-
-
-
ESSFmc
02, 03
LC, FC
N
N
L
L
N
L
L
L
N
N
N
N
04
HH
N
N
L
L
N
L
L
L
N
N
N
L
01
FB
N
N
L
L
N
L
L
M
N
N
N
L
06, 05
FO, FT
N
N
L
L
N
L
L
M
N
N
N
L
08, 09, 10
FV, HG, FH
N
N
L
L
N
L
L
M
N
N
N
L
SP
N
N
L
L
N
L
L
L
N
N
N
N
BS, SF, WW, N
WM
N
-
-
N
L
-
-
N
N
-
-
All others
N
-
-
-
N
-
-
-
N
-
-
-
ESSFmcp, ESSFmkp, AT
N
-
-
-
N
-
-
-
N
-
-
-
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