. . .. , . t. • ...

Lib rary :1

National We tlands Research Center I

U. S. Fish and Wildlife Service

700 Cajundorne Boulevard

Lafayette, La. 70506

BIOLOGICAL REPORT 82(10 .101)

AUGUST 1985

HABITAT SUITABILITY INDEX MODELS:

SNOWSHOE HARE

•

h and Wildlife Service SK

~4 ;. Department of the Interior

n o. 82-

10.101
This is one of the first reports to be published in the new "Bi ol ogi ca l

Report" series. This technical report series, published by the Rese arch

and Development branch of the U.S. Fish and Wlldlife Service, replaces

the IlFWS/OBS" series published from 1976 to September 1984 . The Biolog -

ical Report series is designed for the rapid publication of reports with

an application orientation, and it continues the focus of the FWS/OBS

series on resource management issues and fish and wlldlife needs.
MODEL EVALUATION FORM

Habitat models are designed for a wide variety of planning applications where habitat information is an important consideration in the

decision process. However, it is impossible to develop a model that

performs equally well in all situations. Assistance from users and

researchers is an important part of the model improvement process. Each

model is published individually to facilitate updating and reprinting as

new information becomes available. User feedback on model performance

will assist in improving habitat models for future applications. Please

complete this form following application or review of the model. Feel

free to include additional information that may be of use to either a

model developer or model user. We also would appreciate information on

model testing, modification, and application, as well as copies of modified

models or test results. Please return this form to:

Habitat Evaluation Procedures Group

U.S. Fish and Wildlife Service

2627 Redwing Road, Creekside One

Fort Collins, CO 80526-2899

Thank you for your ass i stance.

Species

Habitat or Cover Type(s)

Geographic

Location

Type of Application: Impact Analysis Management Action Analysis

Baseline Other -------------------------

Variables Measured or Evaluated --------------------

Was the species information useful and accurate? Yes No

If not, what corrections or improvements are needed?----------
Were the variables and curves clearly defined and useful? Yes No

If not, how were or could they be improved?

Were the techniques suggested for collection of field data:

Appropriate? Yes No

Clearly defined? Yes No

Easily applied? Yes No

If not, what other data collection techniques are needed?

Were the model equations logical? Yes No

Appropriate? Yes No

How were or could they be improved?

Other suggestions for modification or improvement (attach curves,

equations, graphs, or other appropriate information)

Additional references or information that should be included in the model:

Model Evaluator or Reviewer Date ------------

Agency _

Address --------------------------------

Telephone Number Comm:----------- FTS
Biological Report 82(10.101)

August 1985

HABITAT SUITABILITY INDEX MODELS: SNOWSHOE HARE

by

Raymond G. Carreker

Habitat Evaluation Procedures Group

Western Energy and Land Use Team

U.S. Fish and Wildlife Service

2627 Redwing Road

Fort Collins, CO 80526-2899

Western Energy and Land Use Team

Division of Biological Services

Research and Development

Fish and Wildlife Service

U.S. Department of the Interior

Washington, DC 20240
This report should be cited as:

Carreker, R. G. 1985. Habitat suitability index models: Snowshoe hare.

U.S. Fish Wildl. Servo Biol. Rep. 82(10.101). 21 pp.
PREFACE

This document is part of the Habitat Suitability Index (HSI) Model Series

[Biological Report 82(10)J which provides habitat information useful for impact

assessment and habitat management. Several types of habitat information are

provided. The Habitat Use Information Section is largely constrained to those

data that can be used to derive quantitative relationships between key environmental variables and habitat suitability. This information provides the

foundation for the HSI model and may be useful in the development of other

models more appropriate to specific assessment or evaluation needs.

The HSI Model Section documents the habitat model and includes information

pertinent to its application. The model synthesizes the habitat use information into a framework appropriate for field application and is scaled to

produce an index value between 0.0 (unsuitable habitat) and 1.0 (optimum

habitat). The HSI Model Section includes information about the geographic

range and seasona 1 app 1i cat i on of the mode1, its current veri fi cati on status,

and a list of the model variables with recommended measurement techniques for

each variable.

The model is a formalized synthesis of biological and habitat information

published in the scientific literature and may include unpublished information

reflecting the opinions of identified experts. Habitat information about

wildlife species frequently is represented by scattered data sets collected

during di fferent seasons and years and from di fferent sites throughout the

range of a species. The model presents this broad data base in a formal,

logical, and simplified manner. The assumptions necessary for organizing and

synthesizing the species-habitat information into the model are discussed.

The model should be regarded as a hypothesis of species-habitat relationships

and not as a statement of proven cause and effect relationships. The model

may have merit in planning wildlife habitat research studies about a species,

as well as in providing an estimate of the relative suitability of habitat for

that speci es. User feedback concerni ng mode1 improvements and other suggestions that may increase the utility and effectiveness of this habitat-based

approach to fish and wildlife planning are encouraged. Please send suggestions

to:

Habitat Evaluation Procedures Group

Western Energy and Land Use Team

U.S. Fish and Wildlife Service

2627 Redwing Road

Ft. Collins, CO 80526-2899

iii
iv
CONTENTS

Page

PREFACE................................................................ iii

ACKNOWLEDGMENTS vi

HABITAT USE INFORMATION 1

Genera 1 1

Food 1

Water 2

Cover 4

Reproduct ion 5

Interspersion and Composition..................................... 6

Special Considerations............................................ 8

HABITAT SUITABILITY INDEX (HSI) MODEL 9

Model Appl icabi 1ity 9

Model Description................................................. 11

Application of the Model.......................................... 15

SOURCES OF OTHER MODELS 18

REFERENCES 18

v
ACKNOWLEDGMENTS

Mr. John R. Cary and Dr. Lloyd B. Keith, University of Wisconsin;

Dr. Michael R. Vaughan, Virginia Cooperative Fish and Wildlife Research Unit;

Mr. Lamar A. Windberg, U.S. Fish and Wildlife Service; and Dr. Michael L.

Wolfe, Utah State University, have provided critiques of an earlier draft of

the snowshoe hare HSI model. The comments and suggestions of these individuals

have added to the quality of this model, and their time and contributions are

gratefully acknowledged.

Word processing was provided by Carolyn Gulzow, Dora Ibarra, and Elizabeth

Graf. Kay Lindgren assisted with the literature search and document acquisition for this project.

vi
SNOWSHOE HARE (Lepus americanus)

HABITAT USE INFORMATION

General

The snowshoe hare (Lepus americanus) is indigenous to boreal forests

throughout North America (Dolbeer and Clark 1975). Snowshoe hares consume

herbaceous vegetation during the growing season and change to a woody diet in

the fall and winter (Baker et al. 1921; Dodds 1960). Young forests with

abundant understory that provide food and cover are preferred habitat (Grange

1932). Snowshoe hares exhi bi t approximate 10-year cycl es of abundance and

scarcity throughout much of their range, which have been attributed to

hare-food interactions (Vowles 1972; Bryant 1981a) and hare-food-predator

interactions (Keith 1974; Wolff 1980, 1981).

Food

During spring and summer, snowshoe hares feed on a wide variety of herbaceous vegetation, including grasses (Gramineae), legumes (Leguminosae) (Brooks

1955), sedges (Carex spp.), ferns (Polypodiaceae) (Dodds 1960), and the leaves

of deciduous trees (Wolff 1978). Fall and winter foods consist of dead grass,

small twigs, buds, bark, conifer needles, lichens, and mosses (Lycopodiaceae)

(Severaid 1942).

Important factors determining diet composition include the density and

frequency of occurrence, nutritive value, and palatability of plant species

(Wolff 1978). Snowshoe hares can show a high degree of adaptation to the

browse available and can feed on almost all species present (Telfer 1972).

Foraging hares also can exhibit decided preferences (Criddle 1938) and the

foods eaten in an area can be largely a function of availability (Pease et al.

1979). In Eastern Canada, deVos (1964) observed that whenever conifers were

available in smaller quantities than deciduous species, the former were browsed

more heavily, whereas Telfer (1972) found that deciduous species were more

heavily browsed than the more abundant evergreen species. Preferential feeding

by snowshoe hares can change plant composition and affect the future availability of plants (Cook and Robeson 1945; deVos 1964).

Snowshoe hares selectively browse on certain parts of a plant. Vowles

(1972) noted that small twigs were the preferred food of hares in Alberta and

referred to rough bark and stem wood as "starvation foods". There is a direct

correlation between woody stem diameter and nutritional quality (Grigal and

Moody 1980; Wolff 1980). Pease et al. (1979) found that captive hares in

1
Alberta primarily ate terminal twigs that were up to 3 to 4 mm in diameter

when supplied with adequate quantities of browse. Keith (1974) believed

browse s 3 mm was essential for snowshoe hare survival. Wolff (1980) stated

that snowshoe hares normally consume browse 3 mm in diameter and that 3 mm

diameter twigs contained more nutrients than larger diameter twigs. The

author suggested that the consumption of twi gs wi th di ameters > 3 mm was a

sign of hares exceeding the habitat carrying capacity, resulting in their

feeding on low quality forage. Grigal and Moody (1980) found the maximum stem

diameter at point of browsing (dpb) to be 1 cm in Minnesota. Wolff (1980)

found that hares at high density in Alaska ate browse that exceeded 1 cm dpb.

A dpb of 1.5 cm was the maximum considered to be clipped by hares in Alberta

(Vowles 1972; Pease et a l . 1979).

The supply of high quality winter browse is one of the most crucial

factors affecting snowshoe hare survival in northern areas (Walski and Mautz

1977). Vowles (1972) and Pease et al. (1979) determined that only part of the

total standing biomass of woody browse is sufficiently digestible or nutritious to sustain snowshoe hares in Alberta. They estimated that 3,000 g (wet

weight) of browse 1.5 cm in diameter must be available to a hare each day.

A hare then can select 300 g of essential food in the form of choice terminal

twigs, buds, and bark.

The nutritive quality of browse has been shown to be directly proportional

to its palatability (Bryant 1981b). Bryant (1981a) suggested that high populations of snowshoe hares that deplete the supply of preferred foods are forced

to feed on low preference browse species, which initiates a crash in the

population even though the total supply of small diameter twigs has not yet

been exhausted. Snowshoe hares in Alaska moved when they increased beyond the

carrying capacity and temporarily depleted their food supply (Wolff 1980).

Vowles (1972) noted an inverse relationship between the abundance of browse

and snowshoe hares in Alberta. Browse abundance declined after several years

of browsing by high populations of hares. When hare populations declined,

browse abundance increased correspondingly.

Various species of, and different parts of, plants can produce resins

that are unpalatable to hares (Bryant 1981a). Some plant species found to be

unpalatable to snowshoe hares are listed in Table 1. Stephenson (1985) found

that black spruce (Picea mariana) became more palatable to snowshoe hares in

the Northwest Territories after the amount of unpalatable compounds in this

species was decreased by fire.

Water

Snowshoe hares are believed to satisfy their water needs from dew and

succulent plants in the summer and by eating snow in the winter (Hansen and

Flinders 1969).

2
Table 1. Plant species found to be unpalatable to snowshoe hares.

Species

Balsam fir (Abies balsamea)

American linden (Tilia americana)

Black cherry (Prunus serotina)

Red-osier dogwood (Cornus stolonifera)

Viburnum (Viburnum cassinoides)

Winterberry holly (Ilex verticil lata)

Black ash (Frax;nus nigra)

European red elder (Sambucus pubens)

Black spruce (Picea mariana)

Labrador tea (Ledum groenlandicum)

Viburnum (y. edule)

Honeysuckle (Lonicera glaucescens, 1. involucrata)

Snowberry (Symphoricarpos occidental is)

Green alder (Alnus crispa)

3

Location

Michigan

Alberta

Alberta

Source

Bookhout (1965a)

Keith et al. (1984)

Cary (Department of

Wildlife Ecology,

University of

Wisconsin, Madison;

pers. comm.)
Cover

The presence of adequate understory cover is the primary determinant of

snowshoe hare habitat quality (Buehler and Keith 1982; Wolfe et al. 1982).

Several authors (Bookhout 1965a,b; Buehler and Keith 1982) suggested that

cover availability is a more significant habitat factor than food availability.

In addition to supplying winter browse, low brushy coniferous and deciduous

vegetation serves as protection from predators and as shelter from inclement

weather (Buehler and Keith 1982).

Many authors suggest that habitat dominated by coniferous vegetation is

preferred. In Nova Scotia, Orr and Dodds (1982) found that snowshoe hare

pellet densities in coniferous habitats were twice as high as those recorded

in deciduous dominated cover. Coniferous lowland forests and conifer plantations were classified as optimum habitat in Wisconsin (Buehler and Keith

1982), swamp conifer was the most favorable habitat in northern Michigan

(Bookhout 1965a,b), and young softwood swamp and fir thickets were preferred

in Maine (Severaid 1942). Snowshoe hares in southern Ontario were mainly

found in poorly drained or swampy areas in which there was heavy coniferous

cover (deVos 1962).

Deciduous cover also can be an important component of snowshoe hare

habitat. Although hares are mainly restricted to areas of red spruce (Picea

rubens) in the Virginias, second growth forests of birch-beech-maple

(Betula-Fagus-Acer) were found to harbor "f'a t r" populations according to

Brooks (1955), particularly when they had a rhododendron (Rhododendron maximum)

or heavy evergreen heath understory. Alder (Alnus spp.) and willow (Salix

spp.) thickets have been described as good winter cover in Wisconsin (Bailey

1946) and Alaska (Wolff 1980). Tompkins and Woehr (1979) reported that

immature hardwood habitat, which provided abundant winter browse and cover,

was preferred in New York. They concl uded that snowshoe hares may be best

adapted to such habitat, and use small conifer stands only out of necessity,

due to the scarcity of hardwood stands since fire suppression and the prohibition of logging. Aspen (Populus tremuloides) stands with dense understories

were bel i eved to constitute margi na 1 to good snowshoe hare habitat in Utah

(Wolfe et al. 1982).

Apparently, a wide variety of forest types can be utilized if adequate

cover is available. Pietz and Tester (1983) believed that cover quality is

the crucial factor defining habitat preference regardless of the species

composition of the stand. Grange (1932) stated that snowshoe hares can occupy

fairly mature woodlands if beaver (Castor canadensis) were present, since hares

make use of cuttings 1eft from beaver foragi ng acti vi ties. Brushpil es were

heavily used in New York and may have been important to hare survival where

conifers were sparse or absent (Richmond and Chien 1976). Old burns containing

dense brush and fallen logs and limbs can also be used extensively as cover

(Grange 1932). Snowshoe hares are often most abundant in sapling and pole

stage forest stands (Brooks 1955; Bookhout 1965a; Richmond and Chien 1976).

4
The relationship between the amount of cover and snowshoe hare abundance

has been investigated by several workers. Adams (1959) subjectively evaluated

cover cond i t t ons in Montana. On the basis of mean pellet density, he found

that snowshoe hares preferred "h eavy" cover [dense stands of early pole-size

Douglas-fir (Pseudotsuga menziesii) with abundant ground litter of dead

saplings and tree limbs] to "light" cover (open stands with no shrub understory), such as Ponderosa pine (Pinus ponderosa) stands. Using a density

board to measure obstruction to lateral visibility in New York, Brocke (1975)

found that "base cover" (used primarily for shelter) visibility ranged from 2%

(98% obstruction) at 5 m to 0% (100% obstruction) at 20 m whereas "trave1

cover" (used for travel from base cover to foraging areas) visibility ranged

from 14.7% (85.3% obstruction) at 5 m to 2.6% (97.4% obstruction) at 20 m. He

suggested that lateral visibility is the single most important stimulus in

selecting cover to avoid predation. Wolfe et al. (1982) determined that areas

with horizontal vegetation densities of 40% (60% visibility) to 100% (0%

visibility), as read from a profile board at a distance of 15 m, can be

adequate snowshoe hare winter habitat in Utah.

Vertical foliage density also is considered an important factor in habitat

preference (Wolff 1980). Brocke (1975) concluded that tree height was the

most important factor determining base cover because it integrates the characteristics of stand density and obstruction to visibility. Heavy cover 3 m

above the surface provides concealment from avi an predators, whereas heavy

cover < 1 m provides concealment from terrestrial predators (Wolff 1980).

Pietz and Tester (1983) noted an increase in the number of snowshoe hare

pellets with an increase in shrub cover> 1 m in height in Minnesota.

The abundance of forage can vary inversely with the density of tree cover

due to shadi ng, which i nhi bi ts the growth of food speci es (i. e., herbaceous

vegetation and shrubs) (Adams 1959). In Nova Scotia, Orr and Dodds (1982)

found a trend for reduced snowshoe hare densities in areas dominated by taller

trees with dense canopies. They recorded lower hare use where trees were

ta11er than 12 m and canopy closure exceeded 60% because adequate cover and

food were not as available. Similarly, Richmond and Chien (1976) noted that

snowshoe hares did not significantly use Red pine (P. resinosa) plantations in

New York where most of the lower limbs were eitherdead or missing and the

thick canopy inhibited the growth of understory vegetation. In Utah, however,

the removal of aspen overstory in areas of dense understory resul ted ina

marked decrease in hare use, suggesting that overstory also is an important

habitat component (Wolfe et al. 1982). In Michigan, cover provided by the

understory was found to be more important in defining snowshoe hare use than

the cover provided by the overstory (Bookhout 1965a).

Reproduction

Criddle (1938) described a snowshoe hare nest as a shallow depression in

dead leaves beneath a leaning tree or among scrub, while COiY (1912) described

the nest as being composed of a mass of grass covered with fur and concealed

under a bush or weeds. However, other workers contend that no nest is constructed (Adams 1959; Keith, Department of Wildlife Ecology, University of

Wisconsin, Madison; letter dated January 1985). Adams (1959) found a small

pi 1e of evergreen sap1i ngs that was used as a "nursery".

5
Young snowshoe hares leave the location of birth within a few days and

scatter into the surroundi ng undergrowth (Cri ddl e 1938; Rongstad and Tester

1971). Young snowshoe hares in Minnesota spent days in separate hiding places

and came together once a night to nurse (Rongstad and Tester 1971). Severaid

(1942) found that captive snowshoe hares began to feed on vegetation at 10 to

12 days of age and suggested that wild hares become independent at 2 weeks.

A shortage of wi nter browse can affect the reproductive performance of

females throughout the summer despite adequate spring herbaceous growth, which

in turn affects the survival of juveniles in the summer (Vowles 1972, Vaughan

and Kei th 1981). Vowl es (1972) also suggested that 1i ght-wei ght juvenil e

hares suffer hi gh mortal i ty duri ng the transition peri od between a summer

herbaceous diet and a fall diet of browse.

Interspersion and Composition

Snowshoe hares travel via runways that are used and maintained year-round

(Grange 1932; Criddle 1938). Runways are used when crossing open areas from

one stand of dense vegetation to another (0' Farrell 1965) and allow quick

escape from predators through thick underbrush (Criddle 1938). Snowshoe hares

also are known to swim back and forth across rivers (Criddle 1938; Hunt 1950).

Travel .through more open areas is usually done only at night (Aldous 1937;

Bider 1961; Brocke 1975).

Snowshoe hares occupy fairly well-defined home ranges that can overlap

considerably. Most authorities believe snowshoe hares have an active core

area of 2 to 3 ha, and that 8 to 10 ha are the limits of home range (Wolff

1980). However, home ranges probably vary with the cover type (Severaid

1942). Criddle (1938) believed that the radius of the home range measures

only a few hundred yards in dense woods but a mile or more in areas dominated

by sparse underbrush.

Habitat i nterspersi on is an important factor determi ni ng snowshoe hare

density and activity. Tompkins and Woehr (1979) reported that hare density in

an area of numerous cover types was nearly twice that of an adjacent area of

less numerous cover types in New York. In a patchy environment, which provides

dense cover in winter and more open foraging areas in summer, snowshoe hares

are able to shift seasonally to a change in diet and to take advantage of

changi ng envi ronmenta 1 condi t ions (Wolff 1980). In Montana, however, Adams

(1959) found that as food growing in areas of dense cover was used up, hares

were attracted away from cover to feed and became more vulnerable to predation.

He concluded that snowshoe hare distribution was a result of adjustments among

the spatial relationships of food, cover, and predators.

Habitat selection can be influenced by the season of the year. Although

forage was plentiful in summer, Bider (1961) found that snowshoe hare movements

and ranges during the rest of the year were influenced by the availability of

certain plant species in Quebec. However, in Alaska, Wolff (1980) found that

snowshoe hares moved to more open areas in the summer, due to the scarcity of

summer foods in dense winter refuge areas. He also suggested that seasonal

movements were in response to forage preferences. Pi etz and Tester (1983)

6
noted that snowshoe hares in Minnesota used areas of deciduous vegetation more

often during snow-free periods, probably due to a dietary shift.

Snowshoe hares occasionally leave areas of cover to forage. Vowles

(1972) noted that hares of high population density crossed large fields to

feed at grainaries and entered farmyards to feed on hay bales and shelterbelts

in Alberta. However, open areas are apparentl~ used most often when they are

associated with cover. Wolff (1980) in Alaska and Wolfe et al. (1982) in Utah

found that snowshoe hares moved to more open areas to forage during the summer

growing season when adequate cover was available. Snowshoe hares in

Newfoundland entered open areas by traversing alder beds or broken stands of

conifers in winter (Dodds 1960). Feeding is often concentrated in vegetative

community edges that supply both food and nearby escape cover (Cook and Robeson

1945; Richmond and Chien 1976; Conroy et al. 1979).

Cover continuity is an important habitat factor. Brocke (1975) found

that small, discontinuous patches of forest were used as travel cover but not

as base cover in New York. Wol fe et a1. (1982) noted that snowshoe hares in

Utah were concentrated in small i sl ands of forested habi tat due to a cl umped

distribution of young fir trees. The use of a mature forest is often dependent

primarily upon the interspersion of openings (i .e., cutover areas and areas of

young growth caused by fire) (Dodds 1960; Grange 1965). Brocke (1975)

suggested that the maximum width of continuous base and travel cover tracts

should not exceed 200 m unless interspersed with openings of browse. Conroy

et al. (1979) recommended that cover should not exceed a distance of 200 to

400 m from cutover areas.

Adequate interspersion of cover is often most critical during the winter.

Conroy et al. (1979) determined that cedar-fir (Thuja occidental is-A. balsamea)

cover in Michigan acted as "reservoirs" wheresnowshoe hare -populations

persisted during the winter. Baker et al. (1921) in Utah and Criddle (1938)

in Manitoba noted that snowshoe hares scattered in the spring and summer but

congregated in thickets after heavy winter snows. Snowshoe hares in Alaska

distributed themselves evenly throughout all suitable habitats during summer

(Wolff 1980). In winter, hares moved to an area that provided 75% vertical

foliage density (25% visibility) at all levels up to 4 m, as measured from a

distance of 3 m using a checkerboard placard. Grange (1965) noted that snowshoe hares were forced to move when deep snows covered pine trees that were

1.1 m high in Minnesota. Snowshoe hares in Quebec were more active in summer

due to the cover provided by an increase in canopy density at that time (Bider

1961). Snowshoe hare tracks were found crossing a large plain in Manitoba

when hares were leaving outlying bushes and the less dense parts of large

woods for more dense areas in the fall (Criddle 1938).

Population pressures also can affect the availability of adequate cover.

Di spersa1 movements have been observed when young snowshoe hares augment

populations in large numbers (Adams 1959; Dolbeer 1972). Due to the discontinuous nature of snowshoe hare habitat in the Western United States, juvenile

hares can be forced to disperse into less favorable (more open) habitat,

resulting in high mortality (Dolbeer 1972; Dolbeer and Clark 1975). In Alaska,

the boreal forest consists of a mosaic of spruce, deciduous, mixed coniferousdeciduous, and willow-shrub communities. This heterogeneity allows snowshoe

7
hares to disperse and become established in less favorable habitat during a

population increase (Wolff 1981). During population declines, snowshoe hares

avoid local extinction by seeking refuge in dense cover (Keith 1966; Woltf

1980). Wolff (1980) believed that the magnitude and frequency of cycles can

be controlled in part by the size and number of such areas of cover.

Snowshoe hares can be affected by barriers to normal movement. Conroy

et al. (1979) noted that areas of sparse woody cover appeared to inhibit the

movements of hares in Michigan. Brocke (1975) found that hares in New York

crossed a clearing 70 m in width only in a narrow neck dominated by sparse

conifer cover. He also found a two-lane paved highway to be a major barrier

to movements.

Special Considerations

Snowshoe hare populations exhibit 8 to l l-ye ar cycles in Alaska (Wolff

1980) and all Canadian provinces except the Maritimes (Keith 1963). Populations in the northeastern (Cook and Robeson 1945) and western (Howell 1923)

United States do not exhibit extreme fluctuations in numbers. The magnitude

of cycles generally appears to be greater northward over the snowshoe hare's

range (Adams 1959).

Predators exhibit a well-defined functional and numerical response to

changes in snowshoe hare abundance (Keith et al. 1977). Predators can move to

areas of high hare abundance and depress local hare populations. Major

predators in the North include the lynx (Lynx canadensis), goshawk (Accipiter

gentilis), great horned owl (Bubo virginianus), red fox (Vulpes fulva), redtailed hawk (Buteo jamaicensis), and pine marten (Martes americana). The red

fox, coyote (Canis latrans), bobcat (Lynx rufus), and several hawk and owl

species are important southern predator-s(Wolff 1980). Dogs (O'Farrell 1965)

and house cats (Severaid 1942) can be important predators in settled areas.

Several major factors can limit snowshoe hare population size. These

include lack of adequate cover (Cook and Robeson 1945; Bookhout 1965a, Brocke

1975), winter food (deVos 1964; Vowles 1972; Walski and Mautz 1977), and

severe winter weather (Meslow and Keith 1971; Vowles 1972). Conroy et al.

(1979) believed that winter represented the critical season for snowshoe hares

in Michigan.

Snowshoe hares can experience competition from other animals. Dodds

(1960) believed that overgrazing by domestic sheep in Newfoundland caused

summer food scarcity, thereby limiting snowshoe hare populations. Moose

(Alces alces) (Dodds 1960) and whitetail deer (Odocoileus virginianus)

(Bookhout 1965a,b) browsing can reduce the amount of food and cover available

to snowshoe hares. Cottontail rabbits (Sylvilagus spp.) and snowshoe hares

can exclude one another in areas of suitable habitat (Buehler and Keith 1982).

Modifications of habitat, such as drainage and deforestation, can

eliminate snowshoe hares from an area (deVos 1962; Windberg and Keith 1978).

8
Large numbers of snowshoe hares can be a serious decimating factor to

natural regeneration in forest stands and in tree plantations (Baker et al.

1921). Barking and browsing damage can kill, deform, and reduce the vigor of

trees and shrubs (deVos 1964). Snowshoe hares prefer the increased food and

cover associated with overstocked stands (Sullivan and Sullivan 1982,1983).

These authors found maximum hare damage with a stocking rate of about 35,000

stems/ha and a mi ni mum with 5,000 to 10,000 stems/ha on a stand of young

sapling and pole-size lodgepole pine (P. contorta) in British Columbia. To

minimize snowshoe hare damage, Cox (1938)recommended against heavy plantings

that would provide good cover while trees are still small and low enough to be

browsed. Bailey (1946) and Sullivan and Sullivan (1982) recommended planting

during periods of low snowshoe hare abundance. Sullivan and Sullivan (1982)

also suggested thinning the stands during the predicted damage period and

proviqing fallen pine foliage and slash as an alternate food source.

Browsing by snowshoe hares also can be useful by accelerating tree growth

(Cox 1938; Cook and Robeson 1945) and by thinning stands (Roe and Stoeckeler

1950), thereby reducing fire and insect damage (Cox 1938). Snowshoe hare

habitat can be enhanced by clearcutting (Conroy et al. 1979; Tompkins and

Woehr 1979; Wolfe et al. 1982). and prescribed burning (Tompkins and Woehr

1979; Wolff 1980). Grange (1965) stated that fire and other disturbances

allow hares to survive in small numbers in mature forests. Buehler and Keith

(1982) believed that unsuitable snowshoe hare habitat increases in the absence

of extensive fires and logging. Adams (1959) recommended lightly thinning

extremely dense forested areas to allow the growth of forage plants and

planting clumps of coniferous cover in areas with inadequate cover. Conroy

et al. (1979) bel ieved that cutover can be enhanced for snowshoe hares by

leaving slash on the site.

HABITAT SUITABILITY INDEX (HSI) MODEL

Model Applicability

Geographic area. This model was developed for application throughout the

range of the snowshoe hare (Fi g. 1).

Season. This model was developed to evaluate the winter habitat of the

snowshoe hare.

Cover types. This model was developed to evaluate habitat in the following cover types (terminology follows that of U.S. Fish and Wildlife Service

1981): Evergreen Forest (EF); Deciduous Forest (OF); Evergreen Tree Savanna

(ETS); Deciduous Tree Savanna (DTS); Evergreen Shrubland (ES); Deciduous

Shrubland (OS); Evergreen Shrub Savanna (ESS); Deciduous Shrub Savanna (DSS);

Evergreen Forested Wetland (EFW); Deciduous Forested Wetland (DFW); Evergreen

Scrub-Shrub Wetland (ESW); and Deciduous Scrub-Shrub Wetland (DSW).

9
Figure 1. Approximate range of the snowshoe hare (modified from

Bittner and Rongstad 1982).

Minimum habitat area. Minimum habitat area is defined as the minimum

amount of contiguous habitat that is required before a species will live and

reproduce in an area. Buehler and Keith (1982) determined that sites with

> 160 ha of suitable habitat in Wisconsin were most often occupied by snowshoe

hares. However, snowshoe hares are known to inhabit woodlot habitat blocks of

1 to 5 ha when within 1.6 to 8 km of larger areas of contiguous habitat (Keith,

unpubl .).

Verification level. The first draft of this model was critiqued by John

R. Cary and Lloyd B. Keith, University of Wisconsin, Madison; Michael R.

Vaughan, Virginia Cooperative Fish and Wildlife Research Unit, Blacksburg, VA;

Lamar A. Windberg, U.S. Fish and Wildlife Service, Laredo, TX; and Michael L.

Wolfe, Utah State University, Logan. Comments from these reviewers have been

incorporated into the current model.

10
Model Description

Overview. The snowshoe hare habitat model considers the abil ity of

winter habitat to meet the food and cover needs of the species as an indication

of year-round habitat suitability. It is believed that snowshoe hares inhabit

areas during the summer that do not provide suitable winter habitat. The

ability of summer habitat to continually support populations of snowshoe hares

is determined by its interspersion with winter habitat. A major assumption of

this model is that areas that provide adequate food and cover during the

winter also will provide adequate summer food and cover. This assumption is

based on the belief that deciduous species that provide adequate winter food

also will provide adequate foliage for the summer diets of snowshoe hares. In

habitats dominated by coniferous species, it is assumed that an adequate

amount of deciduous forage and/or herbaceous vegetation will occur to support

snowshoe ha res duri ng the growi ng season. It a 1so is assumed that summer

cover will never be more l i mi t I nq than winter cover. Reproductive habitat

requirements of the snowshoe hare are assumed to be met by the same habitat

characteristics that define the species· winter habitat.

The following sections provide a written documentation of the logic and

assumptions used to interpret the habitat information for the snowshoe hare

and to explain and justify the variables and equations used in the HSI model.

Specifically, these sections cover identification of variables that will be

used in the model, definition and justification of the suitability levels of

each variable, and a description of the assumed relationship between variables.

Food component. Snowshoe hares requi re enough forage in the form of

woody browse and coniferous foliage to sustain them over the winter months.

Information on the amount of coniferous foliage snowshoe hares consume was not

found in the literature. The following discussion pertains only to the woody

portion of the snowshoe hares' diet.

Snowshoe hares clip stems up to 1.5 cm in diameter during the winter,

although stems < 1 cm are clipped far more commonly (Keith et al. 1984).

Snowshoe hares reach browse within 60 cm of the ground or snowcover. Keith

et al. (1984) emphasized the difference between available browse and available

food. They defined available food as that portion of the available browse

that was 4 mm in diameter, excluding unpalatable species. This definition

was based on evidence that snowshoe hares lose weight and die rapidly when

forced to subsist on browse with a diameter> 4 mm. In addition to diameter,

other factors including palatability, digestibility, species diversity (Keith

et al. 1984), nutritive value, and hare behavior (Sinclair et al. 1982) determine what portion of available browse is actually food. An attempt to define

and quantify these variables is beyond the scope of this model. It is assumed

that an estimate of available browse, as defined by this model, will give a

reasonable indication of food availability for snowshoe hares. Available

browse is thereby defined as woody stems and branches that are: (1) within

the height from ground level to 60 cm above the average local snow depth;

(2) s 1.5 cm in diameter; and (3) live [i.e., contain live buds and bark, and

which bend rather than break easily (Grigal and Moody 1980)J. Browse species

known to be unpalatable to snowshoe hares are not considered as available

browse (Table 1).

11
In order to support a population of snowshoe hares, a habitat must provide

a sufficient quantity of browse throughout the non-growing season. In this

model, a standard food requirement (SFR) is used to define the optimum browse

condition. The SFR can be calculated as follows:

SFR = (KHO) x (NFD)

SO (1)

where KHD = the total number of kilograms (wet weight) of available

browse required per hare per day [e.g., 3 kg reported by

Vowles (1972) and Pease et al. (1979)].

NFO = the average number of frost days per year (from local

records) .

SO = the standard density of hares used to define optimum

food conditions [e.g., 4 hares/ha based on data from

Wolff (1980)].

The value of the standard density (SO) for Equation 1 was arbitrarily

chosen as a means of defining optimum browse conditions. An optimum foraging

habitat would provide enough browse to support the metabolic requirements of

the chosen density of hares. For example, the data of Wolff (1980), whose

study area consisted of diverse, highly productive hare habitats, can be used

to define the optimum browse condition for interior Alaska. Wolff used a dpb

of > 3 mm as an indication of browse consumption in excess of carrying

capacity. He noted that a population of 1.4 hares/ha could be maintained by

twigs < 3 mm in diameter, whereas larger, less nutritious twigs (x dpb = 9.4 mm) were consumed when populations were approximately 6 hares/ha. Assuming

that the low density was below carrying capacity and the high density was

above carrying capacity, a midrange figure of 3.7 hares/ha might be a good

estimate for the SO in interior Alaska. When the field estimate of available

browse (EAB) is obtained anq compared with the SFR, the resulting ratio equals

the SI for food (Equation 2). If the ratio> 1, then SIV1 = 1.0

EAB

SFR = SIV1

12

(2)
The above method of browse estimation requires intensive sampling which

may be beyond the resources or requi rements of some users of thi s model.

Therefore, an alternate method of browse estimation is provided in the following discussion.

The literature indicates that snowshoe hares prefer stem and twig sizes

that commonly occur in young-growth forests. It is assumed that habitats that

provide abundant coniferous foliage and deciduous browse in the form of shrubs

and young trees wi 11 provi de adequate wi nter food for snowshoe hares. Forage

class vegetation is thereby defined as palatable, live vegetation in the form

of coniferous and deciduous shrubs, seedlings « 2.5 cm dbh), and saplings

(2.5 - 12.4 cm dbh) (U.S. Forest Service 1982). It is assumed that cover

types have no suitability as foraging habitat where live coniferous foliage

and the 1ive woody portions of deciduous shrubs and young trees provide 0%

visual obstruction. Cover types in which these vegetation classes provide

50% visual obstruction provide optimum foraging habitat suitability (Fig. 2).

Snowshoe hares are known to clip down vegetation that would otherwise be out

of reach (Keith et al. 1984). It is assumed that a measurement of forage

class vegetation up to 3 m above the ground will adequately represent vegetation available to snowshoe hares when clipped, as well as vegetation available

during periods of deep snow.

1.0

N

:>

........ 0.8 V>

x

Q) 0.6 "'0

s::

>, 0.4

+-'

.0 0.2 ro

+-'

::l

V> 0.0

0 25 50 75 100

Percent visual obstruction

Figure 2. The relationship between the average visual obstruction of

live forage class vegetation and the suitability index value for

snowshoe hare winter food.

13
Cover component. Snowshoe hares require sufficient cover for protection

from predators and inclement weather. Cover for snowshoe hares can consist of

both living and dead vegetation. Measurements of lateral visibility are

assumed to be the most accurate method of assessing cover for snowshoe hares.

Cover height is also an important consideration. In order to provide security

from avian predation and shelter during periods of deep snowpack, adequate

cover for snowshoe hares must extend from the ground to some height above

ground level. It is assumed that cover types that provide < 40% visual

obstruction up to a height of 3 m above the ground have no suitabi 1ity as

cover (Fig. 3). Cover types that provide 90% visual obstruction up to 3 m

have optimum suitability (Fig. 3). As a standard, visual obstruction should

be measured from a distance of 15 m. Because this model is intended to evaluate

the winter habitat of snowshoe hares, it is essential that measurements of

cover be conducted during the period after leaf-fall or before new growth. If

measurements must be done duri ng the growi ng season, a best guess of wi nter

conditions, based on prevailing conditions, must be made in order to obtain a

reasonably accurate estimate of winter habitat parameters.

1.0 (V)

>

C/) 0.8

x

Q) 0.6 -a

c:

......

>, 0.4 +-'

..0 0.2 ro

+-'

:::l

C/) 0.0

a 25 50 75 100

Percent visual obstruction

Figure 3. The relationship between the average visual obstruction

of all living and dead vegetation and the suitability index value

for snowshoe hare winter cover.

14
HSI determination. The Habitat Suitability Index for the snowshoe hare

is determined by the quality of foraging habitat (SIVI or SIV2) and cover

habitat (SIV3). The relationship between cover and foraging habitat quality

is illustrated in the following equations:

HSI = (SIVI x SIV3)

HSI = (SIV2 x SIV3)

(3)

(4 )

Application of the model

Application procedure. When using SIV2 as an index of food suitability,

measurements of wi nter food can be taken at the same time and by the same

method as measurements of winter cover. In essence, SIV2 wi~l be represented

as a fraction of SIV3. Using this combined method, it would be possible to

simultaneously evaluate food and cover characteristjcs of the habitat and to

determine which component is limiting. For example, an old growth forest

habitat with abundant deadfall can provide adequate cover but be deficient in

size classes of plants foraged by snowshoe hares. Relatively open areas with

inadequate cover also can provide either inadequate quantities of forage or

reduced opportunities for snowshoe hares to exploit available food resources.

Optimum habitat would provide adequate cover in the form of vegetation which

also constitutes winter forage for snowshoe hares.

In habitats that display a high degree of cover type diversity (e.g., a

mature forest interspersed with islands of early successional stage vegetation), the potential value of a cover type is influenced by the mix of cover

types. The literature indicates that snowshoe hares commonly move among

different cover types to secure life requisites (i.e., food and cover). In

order to accurately assess the true potential of the total habitat, the contribution of the various cover types must be determined. The following procedure

is recommended:

1. Stratify the evaluation area into characteristic cover types. The

cover types should be defined to delineate areas that differ significantly with respect to SIVI or SIV2 and SIV3.

2. Determine the HSI values for each characteristic cover type.

3. Calculate the overall HSI using the following equation:

n

L Ai

i=1

(5)

n

L (HSIi) x (Ai)

i=1 HS I 0 = -'------'=---------

15
where HSlo = the overall HSI value for the study area.

HSli =the HSI for cover type "i".

Ai = the area of cover type "i".

Summary of model variables. The relationship between habitat variables,

life requisites, cover types, and the HSI value are summarized in Figure 4.

Figure 5 provides variable definitions and suggested measurement techniques

(Hays et al. 1981).

Figure 4. Relationships of habitat variables, life requisites, and

cover types to the HSI for snowshoe hare winter habitat.

16
Variable (dpfinition)

Biomass of Qvailable

browse [the quantity of

live, palatable woody

stems and branches 1.5 cm

(0.6 inches) in diameter

and between ground level and

60 cm (23.6 inches) above the

average snow depth].

Average visual obstruction

measurement of live forage

class vegetation [to a

height of 3 m (9.8 ft)

above the ground].

Average visual obstruction

measurement of all living

and dead vegetation [to a

height of 3 m (9.8 ft)

above the ground].

-

Cover types

EF,DF,ETS,DTS,

ES,DS,ESS,DSS,

EFW, DFW, ESW, DSW

EF,DF,ETS,DTS,

ES,DS,ESS,DSS

EFW, DFW, ESW, DSW

EF,DF,ETS,DTS,

ES,DS,ESS,DSS,

EFW,DFW,ESW,DSW

Suggested technique

Quadrat, clip-and-weigh

(Keith et al. 1984)

Profile board

Profil e board

Figure 5. Definitions of variables and suggested measurement techniques.

Model assumptions. This model was developed with information obtained

from the publications of and communications with professional biologists

familiar with the species and its habitat requirements. It attempts to identify those physical parameters assumed most important in explaining habitat

potential, and then attempts to combine those par~eters into simple algorithms

that yield an index value between 0.0 and 1.0. Major assumptions include:

1..

2.

3.

, An assessment of winter habitat quality will give a reasonable indication

of year-round habitat suitability, assuming that winter is the most

critical season for snowshoe hare survival.

This model evaluates the long-term average suitability of habitat and

does not attempt to predict or explain the cyclic behavior of some snowshoe hare populations.

If browse cannot be clipped and weighed (i.e., SIV1), an ocular estimate

of food biomass (i .e., SIV2) is a reasonable method of indexing food

suitability.

Modifications of the model can be made if the user believes that such modifications will better approximate conditions in the intended area of application.

Users should be aware that the assumptions inherent to modified models can be

different than those listed above.

17
SOURCES OF OTHER MODELS

No habitat models for the snowshoe hare were located.

REFERENCES

Adams, L. 1959. An analysis of a population of snowshoe hares in northwestern

Montana. Ecol. Monogr. 29(2):141-170.

Aldous, C. M. 1937. Notes on the life history of the snowshoe hare. J.

Mammal. 18(1):46-57.

Bailey, R. A. 1946. Reading rabbit population cycles from pines. Wisconsin

Conserv. Bull. 11(7):14-17.

Baker, F. S., C. F. Korstian, and N. J. Fetherolf. 1921. Snowshoe rabbits

and conifers in the Wasatch Mountains of Utah. Ecol.2(4):304-310.

Bider, J. R. 1961. An ecological study of the hare (Lepus americanus). Can.

J. Zool. 39(1):81-103.

Bittner, S. L., and O. J. Rong stad.

146-163 JB J. A. Chapman and G.

America: Biology, management,

Press, Baltimore, MD.

1982. Snowshoe hare and all i es. Pages

A. Feldhamer, eds. Wild mammals of North

and economics. John Hopkins University

Bookhout, T. A. 1965a. The snowshoe hare in upper Michigan - its biology and

feeding coactions with white-tailed deer. Michigan Dept. Conserv.,

Resour. Dev. Rep. 38. 191 pp.

1965b. Feeding coactions between snowshoe hares and whitetailed deer in northern Michigan. Trans. N. Am. Wildl. Nat. Resour

Conf. 30:321-335.

Brocke, ~. H. 1975. Preliminary guidelines for managing snowshoe hare habitat

in the Adirondack.s. Trans. Northeast Sec., The Wildl. Soc., Fish Wildl.

Conf. 32: 46-66.

Brooks, M. 1955. An isolated population of the Virginia varying hare. J.

Wildl. Manage. 19(1):54-61.

Bryant, J. P. 1981a. The regulation of snowshoe hare feeding behaviour

during winter by plant antiherbivore chemistry. Pages 720-731 in World

Lagomorph Conf. Proc. Univ. Guelph.

. 1981b. Phytochemi ca1 deterrence of snowshoe hare browsi ng by -------a~d-ve-n~t~i-tious shoots of four Alaskan trees. Science 213(4510):889-890.

Buehler, D. A., and L. B. Keith. 1982. Snowshoe hare distribution and habitat

use in Wisconsin. Can. Field-Nat. 96(1):19-29.

18
Conroy, M. J., L. W. Gysel, and G. R. Dudderar. 1979. Habitat components of

clear-cut areas for snowshoe hares in Michigan. J. Wildl. Manage.

43(3):680-690.

Cook, D. B., and S. B. Robeson. 1945. Varying hare and forest succession.

Ecol.26(4):406-410.

Cory, C. B. 1912. Mammals of Illinois and Wisconsin. Field Mus. Nat. Hist.

Publ.153. 505 pp .

Cox, W. T. 1936. Snowshoe rabbit migration, tick infestation, and weather

cycles. J. Mammal. 17(3):216-221 .

. 1938. Snowshoe hare useful in thinning forest stands. J. ------=Fo-r-.~3~6~(II):1107-1109.

Criddle, S. 1938. A study of the snowshoe rabbit.

52(3):31-40.

Can. Field-Nat.

deVos, A. 1962. Changes in the distribution of the snowshoe hare in southern

Ontario. Can. Field-Nat. 76(4):183-189 .

. 1964. Food utilization of snowshoe hares on Manitoulin Island, ----=---- Ontario. J. For. 62(4):238-244.

Dodds, D. G. 1960. Food competition and range relationships of moose and

snowshoe hare in Newfoundland. J. Wildl. Manage. 24(1):52-60.

Dolbeer, R. A. 1972. Population dynamics of the snowshoe hare in Colorado.

Ph.D. Diss. Colorado State Univ., Fort Collins. 193 pp.

Dolbeer, R. A., and W. R. Clark. 1975. Population ecology of snowshoe hares

in the central Rocky Mountains. J. Wildl. Manage. 39(3):535-549.

Grange, W. B. 1932. Observations on the snowshoe hare, Lepus americanus

phaeonotus Allen. J. Mammal. 13(1):1-19.

1965. Fire and tree growth relationships to snowshoe rabbits.

Proc. Ann. Tall Timbers Fire Ecol. Conf. 4:110-125.

Grigal, D. F., and N. R. Moody. 1980. Estimation of browse by size classes

for snowshoe hares. J. Wildl. Manage. 44(1):34-40.

Hansen, R. M., and J. T. Flinders. 1969. Food habits of North American

hares. Colorado State Univ. Range Sci. Dept. Sci. Ser. 1. 18 pp.

Hays, R. L., C. S. Summers, and W. Seitz. 1981. Estimating wildlife habitat

variables. U.S. Fish Wildl. Servo FWS/OBS-81/47. 111 pp.

Howell. A. B. 1923. Periodic fluctuations in the numbers of small mammals.

J. Mammal. 4(3):149-155.

19
Hunt, G. S. 1950. Aquatic activity of a snowshoe hare. J. Mammal.

31(2):193-194.

Keith, L. B. 1963. Wildlife's ten-year cycle. Univ. Wisconsin Press,

Madison. 201 pp.

1966. Habitat vacancy during a snowshoe hare decline. J.

Wildl. Manage. 30(4):828-832.

1974. Some features of population dynamics in mammals. Proc.

Int. Congr. of Game Biologists 13:17-58.

Keith, L. B., J. R. Cary, O. J. Rongstad, and M. C. Brittingham. 1984.

Demography and ecology of a' declining snowshoe hare population. Wildl.

Monogr. 90. 43 pp.

Keith, L. B., A. W. Todd, C. J. Brand, R. S. Adamcik, and D. H. Rusch. 1977.

An analysis of predation during a cyclic fluctuation of snowshoe hares.

Proc. Int. Congr. of Game Biologists 13:151-175.

Meslow, E. C., and L. B. Keith. 1971. A correlation analysis of weather

versus snowshoe hare population parameters. J. Wildl. Manage. 35(1):1-15.

O'Farrell, T. P. 1965. Home range and ecology of snowshoe hares in interior

Alaska. J. Mammal. 46(3):406-418.

Orr, C. D., and D. G. Dodds. 1982. Snowshoe hare habitat preferences in Nova

Scotia spruce-fir forests. Wildl. Soc. Bull. 10(2):147-150.

Pease, J. L., R. H. Vowles, and L. B. Keith. 1979. Interactions of snowshoe

hares and woody vegetation. J. Wildl. Manage. 43(1):43-60.

Pietz, P. J., and J. R. Tester. 1983. Habitat selection by snowshoe hares in

northcentral Minnesota. J. Wildl. Manage. 47(3):686-696.

Richmond, M. E., and C. Chien. 1976. Status of the snowshoe hare on the

Connecticut Hill Wildlife Management Area. New York Fish Game J.

23(1):1-12.

Roe, E.!., and J. H. Stoeckeler. 1950. Thinning over-dense jack pine

seedling stands in the Lake States. J. For. 48:861-865.

Rongstad, O. J., and J. R. Tester. 1971. Behavior and maternal relations of

young snowshoe hares. J. Wildl. Manage. 35(2):338-346.

Severaid, J. H. 1942. The snowshoe hare, its life history and artificial

propogation. Maine Dept. Inland Fish Game. 95 pp.

Sinclair, A. R. E., C. J. Krebs, and J. N. M. Smith. 1982. Diet quality and

food limitation in herbivores: the case of the snowshoe hare. Can. J.

Zool. 60(5):889-897.

20
Stephenson, D. E. 1985. The use of charred black spruce bark by snowshoe

hare. J. Wildl. Manage. 49(2):296-300.

Sullivan, T. P., and D. S. Sullivan. 1982. Barking damage by snowshoe hares

and red squirrels in lodgepole pine stands in central British Columbia.

Can. J. For. Res. 12(2):443-448.

1983. Use of index lines and damage assessments to estimate

population densities of snowshoe hares. Can. J. Zool. 61(1):163-167.

Telfer, E. S. 1972. Browse selection by deer and hares. J. Wildl. Manage.

36(4) : 1344-1349.

Tompkins, D. B., and J. R. Woehr. 1979. Influences of habitat on movements

and densities of snowshoe hares. Trans. Northeast Sec., Wildl. Soc.,

Fish Wildl. Conf. 36:169-175.

U. S. Fi sh and Wi 1dl i fe Servi ce. 1981. Standards for the development of

habitat suitability index models. ESM 103. U.S. Fish Wildl. Serv., Div.

Ecol. Servo n.p.

U. S. Forest Servi ce. 1982. Si 1vi cul tura 1 exami nat i on and prescri pt i on handbook. U.S. For. Servo Reg. 2. Lakewood, CO. V.p.

Vaughan, M. R., and L. B. Keith. 1981. Demographic response of experimental

snowshoe hare populations to overwinter food shortage. J. Wildl. Manage.

45(2):354-380.

Vowles, R. H. 1972. Snowshoe hare-vegetation interactions at Rochester,

Alberta. M.S. Thesis, Univ. Wisconsin, Madison. 70 pp.

Walski, T. W., and W. W. Mautz. 1977. Nutritional evaluation of three winter

browse species of snowshoe hares. J. Wildl. Manage. 41(1):144-147.

Windberg, L. A., and L. B. Keith. 1978. Snowshoe hare populations in woodlot

habitat. Can. J. Zool. 56(5):1071-1080.

Wolfe, M. L., N. V. Debyle, C. S. Winchell, and T. R. McCabe. 1982.

hare cover relationships in northern Utah. J. Wildl.

46(3):662-670.

Snowshoe

Manage.

Wolff, J. O. 1978. Food habits of snowshoe hares in interior Alaska. J.

Wildl. Manage. 42(1):148-153.

. 1980. The role of habitat patchiness in the population -----d~y-n-am-l~·c--S of snowshoe hares. Ecol. Monogr. 50(1):111-130.

1981. Refugia, dispersal, predation, and geographic variation

in snowshoe hare cycles. Pages 441-449 ..i!! World Lagomorph Conf. Proc.

Univ. Guelph.

21
Habitat Suitability Index models: Snowshoe Hare

8.

3. Recipient's Accession No.

5. Report Date

August 1985

I. REPORT NO. 2.

Biological Report 82(10.101) ----'--'----------+-

REPORT DOCUMENTATION

PAGE

4. Title and Subtitle

50272 -I 1

~--------~---- - --~-----------~----- ---------------- --------------

7. Author(s)

Raymond G. Carreker 9.P;.1~;;;:,I~.r-O..anjz-.--tlon Na';'-.-and· Add.-;~s weStern Energy and Land Use Team

U.S. Fish and Wildlife Service

2627 Redwing Road

Fort Collins, CO 80526-2899

8. Performlna Ora.nlzatlon R.pt. No.

10. Project/Task/Work Unit No.

II. Contr.ct(C) or Gr.nt(G) No.

(C)

(G)

12. SponsorlnaOr.anlzatlon Name and Addre.. \'Jestern Energy and Land Use Team 13. Type of Report & Period Covered

Division of Biological Services

Research and Development Fish and vJildl ife Service 14-.--------------~~----

______________________Jepar.!mel2..t. ..Q.f the I_~terior. Washi ngtor!_D__C__2_0_24__0 _

15. Supplement.ry Notes The Biological Report series was initiated in October 1984 to replace the

FvJS/OBS series published since 1976. The report number assigned to this model follows

consecutively from the Habitat Suitability Index models published as FWS/OBS-82/10. , now

numbered as Bi 0 1ogjca.L-,~_ejJ9rL_ii?llQ.-).u . _ us. Abstract (Limit: 200 words)

f-------------- -~~ ---

A review and synthesis of existing information were used to develop a Habitat

Suitability Index (HSI) model for the Snowshoe hare (Lepus americanus). The model

consolidates habitat use information into a framework appropriate for field

application, and is scaled to produce an index between 0.0 (unsuitable habitat) and

1.0 (optimum habitat). HSI models are designed to be used with Habitat Evaluation

Procedures previously developed by the U.S. Fish and Wildlife Service.

17. Docum.nt Analysis a. Descriptors

Lagamo rpha

VJil dl ife

Habitabi 1ity

Mathematical models

b. Identifiers/Open-Ended Terms

Snowshoe hare

Lepus americanus

Habitat suitability

c. COSATI field/Group

I" Availability Stateme,,: 21. No. of Paaes

----------------~----------------------,------------------,----------

Ill. Security Class (This Report)

Release unlimited Unclassified 21 ----------------- ------.--

20. Security Class (This P.Re) 22. Price

Unclassified

See ANSI-Z39_18) Se. In.truct/on. on R.ve..e

*U.S. GUVr-:BNM~:N'r PBfNTIN(; OFFiCI':: 1911',--'iiJO-l?O / ;")J?'J

OPTIONAL FORM 272 (4-77)

(formerly NTlS-35)

Department of Commerce
.. ....,-. .. ..

""

*Headquarters, 0lvI5 10n Of Biolog ical

services. Wasn,ngton. DC

)( Eastern Energy and Land Use Team

Leerown. WV

* Naloonal Coastal Ecosystems Team

Slide ll LA

• Western Energy aM LaM Use Team

FI ccu.ns. CO

• Locat ions of RegIonal Ollices

UGION 1

Rqiunlll Director

O.S. Fish lind Wildlife Service

Uoyd Five Hundred Building, Suite 1692

500N.E. Multnomah Street

Portland, Oregon 97232

REGION 4

Regional Director

U.S. Fish and Wildlife Service

Richard B. Russell Building

75 Spring Street, S.W.

Atlanta, Georgia 30303

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REGION 2

Regional Director

U.S. Fish and Wildlife Service

P.O. Box 1306

Albuquerque, New Mexico 87103

REGION S

Regional Director

U.S. Fish and Wildlife Service

One Gateway Center

Newton Comer, Massachusetts 02158

REGION 7

Regional Director

U.S. Fish and Wildlife Service

10II E. Tudor Road

Anchorage, Alaska 99503

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REGION 3

Regional Director

U.S. Fish and Wildlife Service

Federal Building, Fort Snelling

Twin Cities, Minnesota 5SIII

REGION 6

Regional Director

U.S. Fish and Wildlife Service

P.O. Box 25486

Denver Federal Center

Denver, Colorado 80225
DEPARTMENT OF THE INTERIOR

u.s. FISH AND WILDLIFE SERVICE

As the Nation's principal conservation asency, the Department of the Interior has responsibility for most of our .nationally owned public lands and natural resources. This includes

fosterins the wisest use of our land and water resources, protecting our fish and wildlife,

preserving th.environmental and cultural'values of our national parks and historical places,

and providing for the enjoyment of life throulh outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in

the best interests of all our people. The Department also has a major responsibility for

American Indian reservation communities and for people who live in island territories under

U.S. administration.