Mule Deer Winter Habitat Model
Morice and Lakes Forest Districts IFPA
Prepared for:
Morice and Lakes IFPA
Prepared by:
Anne-Marie Roberts
Smithers, BC
DRAFT March 2004
Mule Deer Winter Habitat Model - Morice and Lakes Forest Districts 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 that were 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/or 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 expertise 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 mule deer winter habitat suitability model.
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Table of Contents
Executive Summary ................................................................................................................................ i
INTRODUCTION....................................................................................................................................... 5
SPECIES ACCOUNT AND WINTER HABITAT USE INFORMATION........................................... 5
DISTRIBUTION ........................................................................................................................................... 5
Provincial Range .................................................................................................................................. 5
Elevation Range .................................................................................................................................... 5
Provincial Context ................................................................................................................................ 5
ECOLOGY AND KEY WINTER HABITAT REQUIREMENTS .......................................................................... 5
General ................................................................................................................................................. 5
WINTER HABITAT USE – LIFE REQUISITES ............................................................................................... 6
Feeding Habitat .................................................................................................................................... 6
Thermal/Snow Interception Cover Habitat ........................................................................................... 7
MULE DEER MODEL .............................................................................................................................. 8
APPLICATION OF MODEL .......................................................................................................................... 8
Late Winter Habitat Model Assumptions .............................................................................................. 8
MULE DEER WINTER HABITAT MODEL DESCRIPTION ............................................................................. 8
Description of Network Nodes .............................................................................................................. 9
Mule Deer Winter Habitat Suitability ............................................................................................... 9
Thermal Cover ................................................................................................................................ 11
Accessible Forage ........................................................................................................................... 11
Thermal /Snow Interception Value ................................................................................................. 12
Late Winter Forage Abundance ...................................................................................................... 13
Effective Snow Depth ..................................................................................................................... 14
Crown Closure Class....................................................................................................................... 14
Forest Type ..................................................................................................................................... 15
Aspect ............................................................................................................................................. 15
Elevation ......................................................................................................................................... 15
Snow Depth..................................................................................................................................... 15
Litterfall .......................................................................................................................................... 15
Lichen Litterfall .............................................................................................................................. 16
Conifer Litterfall ............................................................................................................................. 17
Arboreal Lichen Abundance ........................................................................................................... 17
Forest Type ..................................................................................................................................... 17
Winter Ground Forage .................................................................................................................... 18
Leading Species and Secondary Species ........................................................................................ 18
Age Class ........................................................................................................................................ 18
ALR................................................................................................................................................. 18
Island ............................................................................................................................................... 18
COMPUTING OUTPUT FOR HABITAT VALUE ........................................................................................... 18
SENSITIVITY ANALYSIS ........................................................................................................................... 19
TESTING AND VALIDATION ..................................................................................................................... 19
RESEARCH NEEDS FOR MODEL VERIFICATION ....................................................................................... 19
IMPLICATIONS TO FOREST MANAGEMENT .............................................................................................. 19
List of Tables
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Table 1. Important mule deer winter foods. ................................................................................................. 7
Table 2. Conditional Probability table showing the mule deer winter habitat suitability rating based on the
influences of accessible forage, forested thermal cover, and whether the site is located on an island.10
Table 3. Conditional Probability Table showing the probability of late winter forage abundance for nonALR lands. ........................................................................................................................................... 13
Table 4. Conditional probabilities used within Netica to model effective snow depth from snow depth by
biogeoclimatic subzone, modified by aspect and elevation. ............................................................... 14
Table 5. Conditional Probability Table predicting total lichen and conifer litterfall. .................................... 16
List of Figures
Figure 1. Habitat variables and ecological relationships used to build the mule deer winter habitat
suitability Bayesian belief model in the Netica© program..................................................................... 9
Figure 2. Forested thermal cover habitat value based on aspect and the ability of forest cover attributes
to provide thermal cover and the interception of snow. ...................................................................... 11
Figure 3. Accessibility of forage in late winter for sites rated for moderate and high abundance forage and
modified by effective snow depth. ....................................................................................................... 12
Figure 4. Probable thermal/snow interception value based on forest type and crown closure classes. ... 13
Figure 5. Probability of lichen litterfall associated with stands of nil, low, moderate, or high arboreal lichen
abundance. ......................................................................................................................................... 16
Figure 6. Probability of conifer litterfall associated with “forest type” class poor to very good by age class
groupings 4, 5-6, and 7+. .................................................................................................................... 17
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INTRODUCTION
This report describes the mule deer winter habitat model developed for the Morice and Lakes Innovative
Forest Practices Agreement (ML-IFPA). The following document includes a species account for mule
deer (Odocoileus hemionus hemionus), outlines the logic used and assumptions made in the preparation
of the model, describes the model structure and relationships used to build the model, and outlines
testing of model sensitivity and the current level of validation.
SPECIES ACCOUNT AND WINTER HABITAT USE INFORMATION
Common Name:
Mule Deer
Scientific Name:
Odocoileus hemionus hemionus
Species Code:
M-ODHE
Status:
The mule deer is a Yellow (Ym) listed species by the Provincial Tracking Lists of the
British Columbia Conservation Data Centre and is managed for hunting purposes in
the province of British Columbia (Ministry of Environment, Lands and Parks 1994).
Distribution
Provincial Range
There are three sub-species of mule deer (Odecoileus hemionus) in British Columbia. Columbian blacktailed deer (Odocoileus hemionus columbianus) are found on the southern coast and Vancouver Island;
Sitka black-tailed deer (Odocoileus hemionus sitkensis) occur in the Queen Charlotte Islands and the
northern mainland coast; and mule deer (Odocoileus hemionus hemionus) are found in the interior
portions of the province (Bunnell 1990). Mule deer (O. h. hemionus) are found throughout the noncoastal mainland portion of the province in all biogeoclimatic zones except the Mountain Hemlock
biogeoclimatic zone (Stevens 1995).
Elevation Range
Mule deer (O. h. hemionus) occur in forested habitats from sea level to sub-alpine elevations, and may
use alpine areas in summer (Stevens 1995).
Provincial Context
Mule deer occur commonly within the forested areas of the province. The provincial population of mule
deer was estimated at 170,000 in 1996 and is thought to be stable (R. Marshall, pers. comm.). A study of
mule deer (O. h. hemionus) near Williams Lake (Armleder et al. 1986) has contributed much to the
knowledge of winter habitat use in the interior of BC. The mule deer (O. h. hemionus) in the study area
are likely near the northern and western extent of their range (Cowan and Guiget 1978).
Ecology and Key Winter Habitat Requirements
The information used in this species account is based on research on both interior and coastal subspecies of Odocoileus hemionus. Information was selected from the literature that is appropriate for the
mule deer sub-species O. h. hemionus found in the Morice and Lakes Forest Districts.
General
The mule deer is a medium sized member of the family Cervidae that prefers habitat diversity including
conifer forests, mixed forests, meadows and riparian areas. Coniferous forests and riparian areas receive
the most use because these habitat types provide security and thermal cover as well as abundant forage
(Carson and Peek 1987). Distribution of deer is often along ecotones and deer make use of edge
habitats that allow them to access different habitat types for feeding and cover requirements (Kufeld et al.
1988).
Mule deer feed on various herbs, grasses, shrubs and trees and their diet varies seasonally depending on
factors such as food availability, preference and plant quality (Willms et al. 1976). Winter diets shift from
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low-lying grasses and forbs in the early portion of winter to higher shrubs as snow levels increase in late
winter (Carpenter et al. 1979, Bunnell 1990). In general, early and intermediate structural stages with low
tree canopy closure and abundant herbaceous vegetation and shrubs are preferred as forage habitats by
mule deer (Deshamp et al. 1979, Collins and Urness 1983, Loft and Menke 1984, Bunnell 1990). In the
later portions of winter, snow levels in open areas may be greater than mule deer are able to
accommodate and they are forced to forage in forested areas where trees have intercepted the snow.
Mature and old-growth forests are important winter forage areas as the low snow levels resulting from the
closed canopy allow better access to available forage species (Kirchhoff and Schoen 1987, Bunnell 1990,
Armleder et al. 1994). Thermal cover from cold temperatures and wind are also critical factors in mule
deer winter habitat selection (Bunnell 1990, Armleder and Dawson 1992). This requirement is best
obtained from forested stands that are multi-layered and have trees with large crowns (Kirchhoff and
Schoen 1987, Armleder et al. 1994).
In areas of high snowfall, mule deer will occupy separate ranges in summer and winter and are termed
migratory, while deer that remain within the same area all year round are termed resident (Ihsle Pac et al.
1988, Bunnell 1990). In some cases, transitional ranges may be present, and are usually adjacent to
winter range. Long distance movements between summer and winter ranges have been documented to
vary from 19 km (Brown 1992) to a maximum of 148 km (Zalunardo 1965). The movement by mule deer
from summer to winter ranges has been found to be a response to the effects of changing daylight
lengths rather than changes in snow levels found at higher elevations (Garrot et al. 1987). Mule deer
movement from winter to summer range has been suggested to be in response to spring increases in
temperature, insect activity and the maturation of vegetation (Loft et al. 1989). Distinct movement
corridors between seasonal use areas have also been documented, with deer using the corridors on an
annual basis (Thomas and Irby 1990).
Numerous studies have found that mule deer display a high degree of fidelity to traditional seasonal
ranges (Zalunardo 1965, Ihsle Pac et al. 1988, Kufeld et al. 1989, Loft et al. 1989). This site fidelity could
be a function of the topography and vegetation (Ihsle Pac et al. 1988) as well as the traditions of
matriarchal groups (Loft et al. 1989). Kufeld et al. (1989) working in Colorado, reported winter home
range sizes that averaged 211 ha (range = 172 to 292 ha) for five female deer and 226 ha (range = 117
to 323 ha) for 17 female deer (Kufeld et al. 1989). In Montana, Ihsle Pac et al. (1988) found that the
winter range of ten female mule deer averaged 15.9km 2. In any case, winter range must be of sufficient
forage quality so that deer can maintain their energy balance and thereby slow the rate of weight loss
during winter (Carpenter et al. 1979, Torbit et al. 1985).
Winter Habitat Use – Life Requisites
Winter is the critical season for mule deer in northern areas because deep snow results in reduced forage
availability and an increase in energy expenditure during movement. Areas with deep snow preclude use
by mule deer (Gilbert et al. 1970, Parker et al. 1984, Bunnell 1990) and can cause population declines if
alternate low-snow habitats are not available (Gilbert et al. 1970). In winter, deer move to southerly
aspects, lower elevations and exposed ridges where snow depths are lower (Gilbert et al. 1970, Wilms et
al. 1976).
Feeding Habitat
In winter forage opportunities are reduced by snowfall, which either covers forage plants or limits the
mobility of deer. Many researchers have documented the slow decrease of mule deer fat reserves and
body weight during the winter due to reduced digestibility of winter forage (Carpenter et al. 1979, Wallmo
and Schoen 1980, Torbit et al. 1985). To slow this trend, deer spend more time resting and less time
feeding in winter than in summer, to conserve energy and allow their rumen to extract the most from their
food (Kufeld et al. 1988, Bunnell 1990). During winter, a variety of shrubs are the preferred forage for
mule deer. Mule Deer also forage on conifer needles and arboreal lichens from litterfall (Willms et al.
1976, Armleder et al.1986, Armleder and Dawson 1992). Although shrubs are abundant in open areas,
burial by snow and the increased energy cost of travel in deep snow reduces their true availability
(Armleder and Dawson 1992). Subalpine fir (Abies lasicarpa), huckleberry (Vaccinium Spp.), bunchberry
(Cornus canadensis), five-leaved bramble (Rubus pedatus) and arboreal lichens (Alectoria, Bryoria and
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Usnea spp.) are all important winter foods (Willms et al. 1976, Nyberg et al. 1989, Bunnell 1990). Foods
offering a minimum of protein content in summer are almost valueless in mid-winter (Einarsen 1946).
Use of mature forests by mule deer in winter has been documented by a number of authors, especially in
coastal areas where snow accumulations can be high (Harestad 1979, Wallmo and Shoen 1980,
Harestad et al. 1982, Armleder et al. 1986, Kirchhoff and Shoen 1987). Use of patchy forests has been
documented, with the mosaic of open and closed canopies providing a mixture of forage shrubs and snow
interception (Bloom 1978). Carson and Peek (1987) found that coniferous and riparian forest types
provided the best conditions of high forage availability and quality combined with thermal cover. It has
also been suggested that uneven-aged mature and old-growth forests provide higher quality forage than
that found in openings and even-aged second growth, as they have a greater abundance and diversity of
understory species (Shoen et al. 1985). Although in summer mule deer may use the cover and forage
offered simultaneously by edge habitats, high snow accumulation may negate their use in winter (Kirchoff
and Shoen 1983).
A summary of foods used by mule deer in winter is provided in Table 1 (Willms et al. 1976, Blower, 1982,
Nyberg et al. 1989, Bunnell 1990).
Table 1. Important mule deer winter foods.
Type of food
Plant Species
Trees
Pseudotsuga menziesii
Pinus contorta
Abies lasiocarpa
Thuja plicata
Tsuga heterophylla
Shrubs
Vaccinium spp.
Arctostaphylos uva-ursi
Ribes spp.
Betula glandulosa
Menziesia ferruginea
Prunus pensylvanica
Rosa spp.
Rubus pedatus
Amelanchier alnifolia
Cornus stolonifera
Sorbus spp.
Paxistima myrsinites
Linnaea borealis
Salix spp.
Acer glabrum
Lonicera involucrate
Rubus spectabilis
Gaultheria shallon
Herbs
grass
Rubus pedatus
Cornus Canadensis
Carex spp.
Arboreal Lichens
Alectoria spp.
Cetraria spp.
Bryoria spp.
Usnea spp.
Thermal/Snow Interception Cover Habitat
Snow interception cover is likely the most important cover requirement for deer in winter, as deer
movement through 5 cm of snow increases energy expenditures by 10% while snow depths of 50 cm
increase energy expenditure by up to 400% (Parker et al. 1984). Snow depth is so critical that Bunnell
(1990) suggested that there are no suitable habitats for mule deer in areas experiencing snow depths
greater than 60 cm that persist for more than two to three weeks. Gilbert et al. (1970) concluded that
snow depths greater than 46 cm preclude the use of an area by deer. Predicting good snow interception
cover is related to canopy closure, but net timber volume can be used as a more reliable indicator of
reduced snow accumulation (Kirchhoff and Shoen 1987). Snow interception cover is best obtained from
forest stands that are multi-layered and have trees with large crowns (Kirchhoff and Schoen 1987,
Armleder et al. 1994). Armleder et al. (1994) found that mule deer preferred the low snow conditions of
old-growth coniferous stands, which displayed conditions of high crown closure (65%) and that the use of
these habitats increased with increasing snow depth.
Mule deer use a great deal of energy to maintain their body temperature under conditions of cold
temperatures. The energy cost of maintaining a constant body temperature is compounded by exposure
to wind (Armleder and Dawson 1992). Thermal cover is best provided by multi-layered stands that
reduce air movement at ground level and minimize radiation of heat to the open sky (Kirchhoff and
Schoen 1987, Armleder et al. 1994). Topographic features can also provide a windbreak and reduce the
energy costs of thermoregulation (Nyberg et al. 1989).
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MULE DEER MODEL
Application of Model
Season:
Winter (thermal and foraging)
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 mule deer winter
habitat.
Verification Level:
Verification of the model involved testing the belief net to ensure that the output
is consistent with our expected output.
Late Winter Habitat Model Assumptions
The following section describes the logic and assumptions used to translate habitat element information
for mule deer to the variables and equations used in the models.
1. Suitable winter range is critical to mule deer, and is largely a function of accessible forage and
thermal/snow cover.
2. Relatively low canopy closures are assumed to support greater amounts of shrubs and herbaceous
vegetation and hence forage for mule deer, but availability and accessibility will be reduced due to
higher snow levels.
3. High canopy closures are assumed to result in greater snow interception and snow load retention
than lower canopy closures, thereby enhancing mule deer habitat cover values (thermal, security, and
snow interception). It is assumed that mule deer do not winter in areas of deep and persistent snow
packs.
4. Desirable structural attributes required for thermal cover and snow interception , such as a multilayered forest canopy and large trees, are assumed to be correlated with higher structural stage.
5. The ESSFmc, ESSFmcp and AT biogeoclimatic subzones and/or elevations above 1000 m are
assumed to have no value to mule deer as winter habitat in the project area due to deep (>60 cm)
and persistent (for more than two weeks) snow.
6. Mule deer forage on arboreal lichens as litterfall on the forest floor. It is assumed that the more
abundant the arboreal lichens, the more litterfall there will be. A similar assumption is made for
conifer litterfall.
7. Late winter forage abundance is a function of winter ground forage, which is derived from the PEM,
and both arboreal lichen and conifer litterfall, which are derived from forest cover attribute data.
8. Islands are assumed to have no habitat value for mule deer.
9. ALR lands are assumed to have a habitat values of “Low” rather than “Nil” as indicated for other PEM
polygons identified as “development”.
12. Edges or ecotones between areas that provide high habitat cover values and high forage values are
recognized to be highly favoured by mule deer because they minimize energy expenditures between
accessing high forage sites and good thermal/snow interception habitat.
Mule Deer Winter Habitat Model Description
Suitable winter range is assumed to be critical to mule deer. Winter range is highly defined by snow
depth at both the landscape and the stand scale. Mule deer will often use edges or ecotones between
areas that provide high cover values (thermal, security, and snow interception) and high forage values.
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The mule deer winter habitat suitability model is developed as a Bayesian belief influence network using
the Netica© program (See Figure 1). The model is made up of a series of network nodes, some of which
require data manipulation to generate a useful value. The data from these nodes is applied to the model
in a logical sequence in order arrive at a predictive value for winter habitat suitability. The relevance and
logic of each node is explained in the following section.
The output of the mule deer winter habitat model predicts habitat suitability based on cover (thermal and
snow interception) value and foraging value.
Forest Type
Coniferous
25.0
Mixed
25.0
Deciduous
25.0
Non forested 25.0
0.438 ± 0.43
Crown Closure
0 to 1 25.0
1 to 3 25.0
3 to 6 25.0
>= 6
25.0
Aspect
Cool
33.3
Warm 33.3
None
33.3
0.533 ± 0.37
Snow Depth
Shallow
33.3
Moderate 33.3
Deep
33.3
Elevation
< 1000
50.0
>= 1000 50.0
Thermal/Snow Interception Value
Nil
36.3
Poor
31.3
Moderate
19.4
Good
13.1
Snow
Very Shallow
Shallow
Moderate
Deep
Forested Thermal Cover
Nil
18.1
Low
39.5
Moderate 26.5
High
15.9
0.328 ± 0.29
Yes
No
Depth
8.33
26.7
31.7
33.3
Island?
50.0
50.0
Accessible Forage
Nil
25.0
Low
46.1
Moderate 20.9
High
7.96
Arboreal Lichen Abundance
Nil
25.0
Low
25.0
Moderate
25.0
High
25.0
Leading Species
Fd
16.7
S
16.7
B
16.7
P
16.7
H
16.7
Other 16.7
Lichen Litterfall
Nil
25.0
Low
37.5
Moderate 25.0
High
12.5
Forest Type
Poor
18.1
Moderate
44.4
Good
24.3
Very Good 13.2
Litterfall
Nil
9.78
Low
45.1
Moderate 33.9
High
11.3
Conifer Litterfall
Nil
20.0
Low
46.4
Moderate 22.9
High
10.7
Late Winter Forage Abundance
Nil
25.0
Low
11.7
Moderate
39.8
High
23.5
Mule Deer Winter Habitat Value
Nil
66.2
Low
23.2
Moderate
7.54
High
3.12
Secondary Species
Fd
16.7
S
16.7
B
16.7
P
16.7
H
16.7
Other 16.7
0 to 1
1 to 4
4 to 5
5 to 7
>= 7
Age Class
20.0
20.0
20.0
20.0
20.0
Winter Ground Forage
Nil
25.0
Low
25.0
Moderate 25.0
High
25.0
ALR
Non
ALR?
50.0
50.0
Figure 1. Habitat variables and ecological relationships used to build the mule deer winter habitat
suitability Bayesian belief model in the
Netica© program.
C
Description of Network Nodes
Mule Deer Winter Habitat Suitability
The mule deer winter habitat suitability node is the final output node of the network model The value of a
particular habitat to mule deer is a measure of the thermal cover value (including snow interception cover
in winter) and the forage value of that habitat, which is modified by its proximity to other habitat types
(See Table 2). For example, an open wetland or meadow may have high forage value, but no cover
value. However, the value of such a habitat is increased if it is within 100 m of cover habitat (i.e. high
canopy closure, mature coniferous forest). Note that if the polygon is located on an island the resulting
winter habitat value is reduced to nil.
Example Relationship:
Conditional Probability Table
Where:
MDWHV = Mule deer winter habitat value
MDTCV = Mule deer forested thermal cover value
MDFAV = Mule deer accessible forage value
ISL = Island habitat
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B
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Table 2. Conditional Probability table showing the mule deer winter habitat suitability rating based on the
influences of accessible forage, forested thermal cover, and whether the site is located on an
island.
Mule Deer Winter Habitat Suitability
Island?
Forested Thermal Cover
Accessible Forage
Nil
Low
Moderate
High
No
Nil
Nil
100
0
0
0
No
Nil
Low
100
0
0
0
No
Nil
Moderate
100
0
0
0
No
Nil
High
100
0
0
0
No
Low
Nil
100
0
0
0
No
Low
Low
0
100
0
0
No
Low
Moderate
0
60
40
0
No
Low
High
0
35
50
15
No
Moderate
Nil
100
0
0
0
No
Moderate
Low
0
90
10
0
No
Moderate
Moderate
0
0
100
0
No
Moderate
High
0
0
20
80
No
High
Nil
100
0
0
0
No
High
Low
0
70
30
0
No
High
Moderate
0
0
20
80
No
High
High
0
0
0
100
Yes
Nil
Nil
100
0
0
0
Yes
Nil
Low
100
0
0
0
Yes
Nil
Moderate
100
0
0
0
Yes
Nil
High
100
0
0
0
Yes
Low
Nil
100
0
0
0
Yes
Low
Low
100
0
0
0
Yes
Low
Moderate
100
0
0
0
Yes
Low
High
85
15
0
0
Yes
Moderate
Nil
100
0
0
0
Yes
Moderate
Low
100
0
0
0
Yes
Moderate
Moderate
100
0
0
0
Yes
Moderate
High
20
80
0
0
Yes
High
Nil
100
0
0
0
Yes
High
Low
100
0
0
0
Yes
High
Moderate
20
80
0
0
Yes
High
High
0
100
0
0
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Thermal Cover
The thermal cover value of a habitat is a function of forest cover and aspect, as well as snow interception
cover. Habitats with good thermal/snow interception cover consist mainly of closed canopy mature
forests that are multi-layered and have large trees with deep spreading crowns for optimal snow loading.
Figure 2 describes the probable forested thermal cover value as a function of aspect and the ability of
forest cover attributes to provide both thermal cover and the interception of snow.
One further qualifier to this node is required for Agricultural Land Reserve (ALR) lands. PEM requires
forest cover data to predict a site series. ALR Lands often do not have forest cover mapping, so the PEM
includes these lands under the broad heading of “development”. The “development” type also includes
municipalities and roads, but is clearly not the same type of habitat for mule deer in the winter as are
agricultural lands. To accommodate this mapping artefact in the habitat model, an ALR layer was used to
identify lands under the development label that are agricultural. In the model “development” site types
result in a “Nil” value for thermal cover ;except where they intercept with ALR lands, where they are
assigned a “low” value. The ALR lands may have even greater habitat value (than “low”), but at least this
permeation in the habitat model enables these site types to be considered as potentially contributing to
mule deer winter range.
Example Relationship:
Conditional Probability Table
Where:
MDTCV = Mule deer forested thermal cover value
CCV = Thermal/snow interception value
ALR = Land in the agricultural land reserve
ASPECT = Aspect: Warm, cool and none (for slope<10)
Forested Therm al Cover for Cool or Flat
Aspect, Non-ALR areas
100%
Forested Therm al Cover for Warm Aspect,
Non-ALR areas
100%
Moderate
50%
oo
d
G
M
od
er
at
e
G
N
oo
d
0%
M
od
er
at
e
0%
Po
or
25%
Po
or
Nil
25%
Therm al/Snow Interception
Low
il
Nil
High
75%
N
Low
50%
Probability
Moderate
il
Probability
High
75%
Therm al/Snow Interception
Figure 2. Forested thermal cover habitat value based on aspect and the ability of forest cover attributes
to provide thermal cover and the interception of snow.
Accessible Forage
In winter mule deer eat a variety of shrubs, some herbs and litterfall of arboreal lichens and conifer
needles; the proportions of which depend on forage accessibility. Forage accessibility is dependent on
both forage abundance and snow depth. Forage abundance is based on litterfall estimates and on winter
forage vegetation cover by PEM derived site series and structural stage. Snow depth is evaluated using
biogeoclimatic subzones, elevation, and aspect.
Page 11
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Mule Deer Habitat Model - Morice and Lakes Forest Districts IFPA
For sites with “Nil” forage abundance, the accessible forage is “Nil” and for “Low” forage abundance,
accessible forage is “Low” for all snow depths. Accessible forage for “moderate” and “good” late winter
forage abundance sites is dependent on effective snow depth (See Figure 3).
Example Relationship:
Conditional Probability Table
Where:
MDFAV = Accessible forage by mule deer in winter
FH = Late winter forage abundance
Accessible Forage for Site w ith Moderate
Forage Abundance
100%
High
75%
Moderate
Low
50%
Nil
25%
100%
High
75%
Moderate
Low
50%
Nil
25%
Snow Depth
ee
p
D
M
od
er
at
e
Ve
ry
Sh
al
lo
w
Sh
al
lo
w
ee
p
D
Sh
al
lo
w
0%
M
od
er
at
e
Ve
ry
Sh
al
lo
w
0%
Accessible Forage for Site w ith High
Forage Abundance
Probability
Probability
SD = Snow depth (as defined by BEC, aspect, and elevation)
Snow Depth
Figure 3. Accessibility of forage in late winter for sites rated for moderate and high abundance forage and
modified by effective snow depth.
Thermal /Snow Interception Value
In winter, habitat that is non-forested or has an open canopy is generally poor habitat for mule deer due to
reduced mobility in the accumulated snow. By contrast, closed or multi-strata forests provide thermal
cover by acting as a break to the winter and creating a microclimate under the forest canopy; and, they
provide snow interception cover by collecting snow in the forest canopy rather than on the forest floor
Thermal/snow interception values are predicted based on forest type and crown closure attributes of the
forest cover mapping as illustrated in
Good
Moderate
Poor
Nil
Figure 4.
Example Relationship:
Conditional Probability Table
Where:
CCV = Thermal/snow interception value
CRNCL_CL= Crown closure class
FT1 = Forest Type
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Therm al/Snow Interception For
Forest Types w ith Crow n Closure
Class 3 to 5
100%
25%
25%
Forest Type
C
N
Forest Type
Good
Moderate
s
on
_f
or
es
te
d
on
i fe
ro
us
s
on
_f
or
es
te
d
ec
id
uo
u
D
N
N
C
M
ix
ed
0%
on
i fe
ro
us
s
on
_f
or
es
te
d
ec
id
uo
u
D
on
i fe
ro
us
M
ix
ed
0%
50%
ec
id
uo
u
0%
50%
75%
D
25%
75%
M
ix
ed
50%
Therm al/Snow Interception For
Forest Types w ith Crow n Closure
Class 6+
100%
Probability
Probability
75%
C
Probability
Therm al/Snow Interception For
Forest Types w ith Crow n Closure
Class 1 and 2
100%
Poor
Forest Type
Nil
Figure 4. Probable thermal/snow interception value based on forest type and crown closure classes.
Late Winter Forage Abundance
The late winter forage abundance node evaluates the total abundance of forage from all sources
(arboreal and conifer litterfall and ground vascular vegetation). Note that ALR lands are automatically
assigned a late winter forage value of “low” (rather than “nil” as other “development” polygon are).
Example Relationship:
Conditional Probability Table
Where:
CCV = Thermal/snow interception value
Litterfall = Litterfall
MD_W_FOR = Winter ground forage
ALR = ALR (Agricultural Land Reserve)
Table 3. Conditional Probability Table showing the probability of late winter forage abundance for nonALR lands.
Late Winter Forage Abundance
Winter Ground
Forage
Litterfall
Nil
Low
Moderate
High
Nil
Nil
100
0
0
0
Nil
Low
100
0
0
0
Nil
Moderate
100
0
0
0
Nil
High
100
0
0
0
Low
Nil
0
30
70
0
Low
Low
0
0
100
0
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Low
Moderate
0
40
60
0
Low
High
0
5
35
60
Moderate
Nil
0
20
80
0
Moderate
Low
0
0
100
0
Moderate
Moderate
0
0
100
0
Moderate
High
0
0
20
80
High
Nil
0
10
40
50
High
Low
0
0
30
70
High
Moderate
0
0
10
90
High
High
0
0
0
100
Effective Snow Depth
Effective snow depth is predicted based on biogeoclimatic subzone and modified by elevation and aspect.
Warm aspects and lower elevation habitats (< 1000 m) tend to have lower snow accumulation than other
sites (see Table 4). There are no subzones on in the study area that are considered “Moderate” snow
depth for mule deer.
Example Relationship:
Conditional Probability Table
Where:
ESD = Effective snow depth
ASPECT= Aspect
SNOW = Snow depth by biogeoclimatic subzone
ELE = Elevation (<1000m or >=1000m)
Table 4. Conditional probabilities used within Netica to model effective snow depth from snow depth by
biogeoclimatic subzone, modified by aspect and elevation.
Effective Snow Depth
Snow Depth
Elevation
Aspect
Very Shallow
Shallow
Moderate
Deep
Shallow
<1000
Cool
0
100
0
0
Shallow
<1000
Warm
100
0
0
0
Shallow
<1000
None
0
100
0
0
Shallow
>=1000
Cool
0
100
0
0
Shallow
>=1000
Warm
50
50
0
0
Shallow
>=1000
None
0
100
0
0
Deep
<1000
Cool
0
0
0
100
Deep
<1000
Warm
0
0
0
100
Deep
<1000
None
0
0
0
100
Deep
>=1000
Cool
0
0
0
100
Deep
>=1000
Warm
0
0
0
100
Deep
>=1000
None
0
0
0
100
Page 14
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Mule Deer Habitat Model - Morice and Lakes Forest Districts IFPA
Crown Closure Class
Crown closure affects thermal cover value in winter by reducing wind chill by minimizing air movement,
and by reducing radiation to the open sky during low temperatures. High crown closure can be provided
by mature and old growth forests that have large trees with deep, spreading crowns and a multi-layered
canopy and by dense stands of pole/sapling stage forest. The crown closure also affects how much snow
interception there is. The higher the crown closure, the better the snow interception. Better snow
interception results in reduced snow depth under the canopy. As well, when snow accumulates on the
canopy and then falls to the ground, the snow tends to pack, which can make travel relatively easier than
in open areas. Crown closure classes are summarized in this node as: class 0 (no canopy), class 1 and 2
(low canopy), class 3 to 5 (moderate canopy), and class 6+ (high canopy).
Variables:
CRNCL_CL = Crown Closure Class
Forest Type
The forest type node is summarized from the forest cover data into four types: coniferous (>=80%
coniferous species), mixed (20%> coniferous species <80%), deciduous (>=80% deciduous species),
non-forested (no tree species).
Variables:
FT1 = Forest Type
Aspect
Aspect is simplified into three states: warm (136° to 270°), cool (271° to 135°), and “none” (sites that have
slope less than 10°). One assumption is that snow depth or condition is not affected by aspect on sites
with slopes less than 10°. Another assumption is that cool aspects tend to maintain a relatively higher
snow depth than do warm aspects. Warm aspects are assumed to be favourable to mule deer because of
higher snowmelt due to insolation.
Variables:
ASPECT = Aspect classes
Elevation
Elevations greater than or equal to 1000m are considered to have too great a snow load for mule deer in
winter. In the study area, this elevation band tends to be located near the upper boundary of the SBSmc2
or the SBSwk3 subzones.
Variables:
ELE = Elevation
Snow Depth
Snow depth is derived from the biogeoclimatic subzone line mapping. Three categories of snow depth
are used: shallow, moderate, and deep. These categories were delineated based on mule deer
response to snow loads. The SBPSmc and SBSdk subzones are considered to have shallow snow
depths, less than 60 cm. All other subzones are considered to have deep snow depths, greater than
60cm persisting for more than 2 weeks, and are considered to be unsuitable.
Variables:
SNOW = Snow Depth by biogeoclimatic zone
Litterfall
Litterfall provides a measure of the total potential of the stand to provide litterfall forage from either
arboreal lichens or from conifer tree species. The respective litterfall ratings are effectively submodels.
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Table 5 describes how the values for arboreal lichen and conifer literfall are combined to predict total
litterfall.
Example Relationship:
Conditional Probability Table
Where:
Litterfall = Litterfall (total forage)
LL = Lichen litterfall
CL = Conifer litterfall
Table 5. Conditional Probability Table predicting total lichen and conifer litterfall.
Lichen Litterfall
Conifer Litterfall
Litterfall Total
Nil
Low
Moderate
High
Nil
Nil
100
0
0
0
Nil
Low
25
75
0
0
Nil
Moderate
0
50
50
0
Nil
High
0
25
50
25
Low
Nil
25
75
0
0
Low
Low
0
100
0
0
Low
Moderate
0
40
60
0
Low
High
0
0
40
60
Moderate
Nil
0
40
60
0
Moderate
Low
0
25
75
0
Moderate
Moderate
0
0
100
0
Moderate
High
0
0
25
75
High
Nil
0
0
50
50
High
Low
0
25
50
25
High
Moderate
0
0
25
75
High
High
0
0
0
100
Lichen Litterfall
Lichen litterfall is estimated based on the results of the arboreal lichen abundance model which is derived
from forest cover. The assumption is that the greater the arboreal lichen abundance the greater the
probability that there will be lichen litterfall (See Figure 5).
Example Relationship:
Conditional Probability Table
Where:
LL = Lichen litterfall
ARB = Arboreal lichen abundance
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Lichen Litterfall
Probability
100%
High
75%
Moderate
50%
Low
25%
Nil
0%
Nil
Low
Moderate
High
Arboreal Lichen Abundance
Figure 5. Probability of lichen litterfall associated with stands of nil, low, moderate, or high arboreal lichen
abundance.
Conifer Litterfall
The probability of conifer litterfall is based on the “forest type” and the age class of the stand. Note that in
this model “forest type” is a measure of the leading and secondary tree species’ ability to produce conifer
forage, from “poor” to “very good”. For age class 0, the conifer litterfall is “nil” and for age classes 1, 2,
and 3, the conifer litterfall is low, regardless of “forest type”. Only once a stand reaches age class 4 and
older, is there conifer
litterfall (See
High
Moderate
Low
Nil
Figure 6).
Example Relationship:
Conditional Probability Table
Where:
CL = Conifer litterfall
AGE_CLS = Age Class
FT = forest type
Conifer Litterfall for Age Class 4
Stands
Conifer Litterfall for Age Class 5
and 6 Stands
Conifer Litterfall for Age Class 7+
Stands
75%
75%
75%
50%
50%
25%
25%
0%
0%
Poor
Moderate
Good
Forest Type
Very
Good
High
Probability
100%
Probability
100%
Probability
100%
50%
25%
0%
Poor
Moderate
Good
Forest Type
Moderate
Low
Very
Good
Poor
Moderate
Good
Forest Type
Nil
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Very
Good
Mule Deer Habitat Model - Morice and Lakes Forest Districts IFPA
Figure 6. Probability of conifer litterfall associated with “forest type” class poor to very good by age class
groupings 4, 5-6, and 7+.
Arboreal Lichen Abundance
The arboreal lichen abundance node is a parent node whose values are predicted in the arboreal lichen
Netica model. This node has the values of high, moderate, low, and nil potential for arboreal lichen
abundance.
Variables:
ARB = Arboreal lichen abundance
Forest Type
“Forest type” looks at leading and secondary tree species and provides a rating of their combined value
as preferable conifer forage species for mule deer. The classes are: poor, moderate, good, and very
good. For example, Douglas-fir stands are highly preferable, with other conifers such as spruce,
subalpine fir, and hemlock less preferable.
Example Relationship:
Conditional Probability Table
Where:
FT = Forest type
SPC_1 = Leading species
SPC_2 = Secondary species
Winter Ground Forage
Winter ground forage is derived from the PEM. This is a parent node that is read in from a lookup table
where site series and structural stage groupings are rated for their abundance of preferred ground forage.
A preferred winter vascular forage vegetation list was compiled from the literature. Vegetation on this list
was summarized for presence and abundance by site series. These presence and abundance values
were then summarized into ratings of Nil, Low, Moderate, or High abundance.
Variables:
MD_W_FOR = Winter Ground Forage
Leading Species and Secondary Species
The leading and secondary species nodes are read in from the forest cover data. This information is
used to describe the “forest type” rating of conifer forage species, which combined with age class will give
an indication of conifer litterfall.
Variables:
SPC_1 = Leading species
SPC_2 = Secondary species
Age Class
Age class is from the projected age class in the forest cover data. This is a parent node and is grouped
into 5 class categories: 0, 1 to 3, 4, 5 to 6, and 7+.
Variables:
AGE_CLS = Age Class
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ALR
Agricultural land reserve (ALR) is a parent node that modifies late winter forage abundance and thermal
cover values. ALR Lands often do not have forest cover mapping, so the PEM includes these lands under
the broad heading of “development”. The “development” type also includes municipalities and roads, but
is clearly not the same type of habitat for mule deer in winter as are agricultural lands. To accommodate
this mapping artefact in the habitat model, an ALR layer was used to identify lands under the
development label that are agricultural. Instead of receiving a “nil” values for late winter forage
abundance and thermal cover as for other polygons with the “development” site type, ALR lands are
assigned values of “low” for these model nodes.
Variables:
ALR = ALR (Agricultural Land Reserve)
Island
Islands are not used by mule deer in winter. So, while other habitat features may point to a higher habitat
suitability rating for a particular polygon, location on an island r5esults in a downgrade to “nil” value in the
final winter habitat suitability node.
Variables:
ISL = Island
Computing Output for Habitat Value
Non-spatial mule deer foraging habitat suitability will be the output from the model for each polygon.
Sensitivity Analysis
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.
The mule deer winter model has been tested within Ardea. A working review of the data and mapped
output was done with MWLAP representatives from Smithers, BC.
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 habitat suitability value; however, the pattern and amount of the habitat with respect to caribou
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).
Implications to Forest Management
Management levers exist within the mule deer model. In winter, mule deer are highly associated with low
elevation warm aspect sites that support forage vegetation and are either in close proximity to forested
Page 19
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cover or have forested cover. Forest age, canopy closure, tree species, abundance of forage species
(such as shrub species) and configuration of forested habitats adjacent to open south facing slopes are
all attributes that can be managed to some extend within mule deer winter range.
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MULE DEER MODEL REFERENCES
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approach. Forestry Chron. 68(1):132-137.
Armleder, H.M., R.J. Dawson and R.N. Thomson. 1986. Handbook for timber and mule deer management
coordination on winter ranges in the Cariboo Forest Region. Min. of For., Victoria, BC. Land
Management Handbook No. 13. 98pp.
Armleder, H.M., M.J. Waterhouse, D.G. Keisker and R.J. Dawson. 1994. Winter habitat use by mule deer
in the central interior of British Columbia. Can. J. Zool. 72:1721-1725.
Bloom, A. 1978. Sitka black-tailed deer winter range in the Kadashan Bay area, southeast Alaska. J.
Wildl. Manage. 42(1):108-112.
Blower, D. 1982. Memorandum on key winter forage plants for BC ungulates. Min. Env., Lands and
Parks. 1 pp.
Brown, C.G. 1992. Movement and migration patterns of mule deer in southeastern Idaho. J. Wildl.
Manage. 56(2):246-253.
Bunnell, F.L. 1990. Ecology of black-tailed deer. Pages 31-63 in. J.B. Nyberg and D.W. Janz, eds. Deer
and elk habitats in coastal forests of southern British Columbia. Min. of For. Victoria, BC. Special
Report Series No.5. 310pp.
Carpenter, L.H, O.C. Wallmo and R.B. Gill. 1979. Forage diversity and dietary selection by winter mule
deer. J. Range Manage. 32(3):226-229.
Carson, R.G. and J.M. Peek. 1987. Mule deer habitat selection patterns in northcentral Washington. J.
Wildl. Manage. 51(1):46-51.
Collins, W.B. and P.J. Urness. 1983. Feeding behaviour and habitat selection of mule deer and elk on
northern Utah summer range. J. Wildl. Manage 47(3): 646-663.
Cowan, I.McT. and C.G. Guiget. 1978. The mammals of British Columbia. BC. Prov. Mus., Victoria, BC.
Handb. No. 11. 7th printing. 414pp.
Deschamp, J.A., P.J. Urness and D.D. Austin. 1979. Summer diets of mule deer from lodgepole pine
habitats. J. Wildl. Manage. 43(1):154-161.
Einarsen, A.S. 1946. Management of black-tailed deer. J. Wildl. Manage. 10(1):54-59.
Garrot, R.A., G.C. White, R.M. Bartmann, L.H. Carpenter, and A.W. Alldredge. 1987. Movements of
female mule deer in northwest Colorado. J. Wildl. Manage. 51(3):634-643.
Gilbert, P.F., O.C. Wallmo and R.B. Gill. 1970. Effect of snow depth on mule deer in Middle Park,
Colorado. J. Wildl. Manage. 34(1):15-23
Harestad, A.S. 1979. Seasonal movements of black-tailed deer on northern Vancouver Island. Min. of
Env. Fish and Wildl. Rep. No. R-3. 99pp.
Harestad, A.S., J.A. Rochelle and FL. Bunnell. 1982. Old-growth forests and black-tailed deer on
Vancouver Island. Trans. N. Amer. Wildl. Nat. Res. Conf. 47:343-352.
Ihsle Pac, I.H., W.F. Kasworm, L.R. Irby and R.J. Mackie. 1988. Ecology of the mule deer, Odocoileus
hemionus, along the east front of the Rocky Mountains, Montana. Can. Field. Nat. 102:227-236.
Kirchhoff, M.D. and J. W. Schoen. 1983. Black-tailed deer use in relation to forest clear-cut edges in
southeastern Alaska. J. Wildl. Manage. 47(2):497-501.
Kirchhoff, M.D. and J. W. Schoen. 1987. Forest cover and snow: Implications for deer habitat in southeast
Alaska. J. Wildl. Manage. 51(1):28-33.
Kufeld, R.C., D.C. Bowden and D.L. Schrupp. 1988. Habitat selection and activity patterns of female mule
deer in the Front Range, Colorado. J. Range. Manage. 41(6):515-522.
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Mule Deer Habitat Model - Morice and Lakes Forest Districts IFPA
Kufeld, R.C., D.C. Bowden and D.L. Schrupp. 1989. Distribution and movements of female mule deer in
the Rocky Mountain foothills. J. Wildl. Manage. 53(4):871-877.
Loft, E.R. and J.W. Menke. 1984. Deer use and habitat characteristics of transmission-line corridors in a
Douglas-fir forest. J. Wildl. Manage. 48(4) 1311-1315.
Loft, E.R., R.C. Bertram and D.L. Bowman. 1989. Migration patterns of mule deer in the central Sierra
Nevada. Calif. Fish and Game 75(1):11-19.
Ministry of Environment, Lands and Parks. 1994. Birds, mammals, reptiles and amphibians not at risk in
British Columbia: the revised yellow list, 1994. Habitat Protection Branch. Wildlife Working Rep. No.
WR-66. Victoria, BC. 72pp.
Nyberg, B.J, S.R. McNay, M.D. Kirchoff, R.D. Forbes, F.L. Bunnell and E.L. Richardson. 1989. Integrated
management of timber and deer: coastal forests of British Columbia and Alaska. US Dept. of
Agriculture. PNW-GTR-226. 21 pp + append.
Parker, K.L., C.T. Robbins and T.A. Hanley. 1984. Energy expenditures for locomotion by mule deer and
elk. J. Wildl. Manage. 48(2):474-488.
Schoen, J.W., M.D. Kirchhoff and M.H. Thomas. 1985. Seasonal distribution and habitat use by Sitka
black-tailed deer in southeastern Alaska. Final report, Federal Aid in Wildlife Restoration Projects.
Juneau, Alaska. 44pp.
Stevens, V. 1995. Wildlife diversity in British Columbia: Distribution and habitat use of amphibians,
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