FWS/OBS-82/1 0.65

JUNE 1984

HABITAT SUITABILITY INDEX MODELS:

PRONGHORN

J /

I

-Fish and Wildlife Service

SK

361

.U54

no. 82-

10.65

. Department of the Interior
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 al so 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 assistance.

Species ----_._-

Geographic

Location

Habitat or Cover Type(s)

Type of Application: ]mpact Analysis

Baseline Other

Management Action Analysis

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 Evaluater or Reviewer Date -------------

Agency

Address

Telephone Number Comm:------------ FTS ----------
FWS/OBS-82/10.65

June 1984

HABITAT SUITABILITY INDEX MODELS: PRONGHORN

by

Arthur W. Allen

Habitat Evaluatiun Procedures Group

Western Energy and land Use Team

U.S. Fish and Wildlife Service

Drake Creekside Building One

2627 Redwing Road·

Fort Collins, CO 80526-2899

John G. Cook

Department of Zoology and Physiology

University of Wyoming

Laramie, WY 82071

and

Michael J. Armbruster

Habitat Evaluation Procedures Group

Western Energy and Land Use Team

U.S. Fish and Wildlife Service

Drake Creekside Building One

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:

Allen, A. W., J. G. Cook, and M. J. Armbruster. 1984. Habitat suitability

index models: Pronghorn. U.S. Fi sh Wi 1dl. Serv. FWS/OBS-82/10. 65.

22 pp.
PREFACE

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

(FWS/OBS-82/10), 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. The habitat use information provides

the foundation for the HSI model that follows. In addition, this same information may be useful in the development of other models more appropriate to

specific assessment or evaluation needs.

The HSI Model Section documents a habitat model and 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 application information includes descriptions of the geographic ranges and seasonal

application of the model, its current verification status, and a listing of

model variables with recommended measurement techniques.

In essence, the model presented herein is a hypothesis of species-habitat

relationships and not a statement of proven cause and effect relationships.

Results of model performance tests, when available, are referenced. However,

models that have demonstrated reliability in specific situations may prove

unreliable in others. For this reason, feedback is encouraged from users of

this model concerning improvements and other suggestions that may increase the

utility and effectiveness of this habitat-based approach to fish and wildlife

planning. 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 3

Cover 3

Reproduct ion 4

I nterspersion 4

Special Considerations............................................ 5

HABITAT SUITABILITY INDEX (HSI) MODEL 6

Model Applicability.. 6

Model Description................................................. 8

Model Relationships............................................... 13

Appl ication of the Model 13

SOURCES OF OTHER MODELS 18

REFERENCES 19

v
ACKNOWLEDGMENTS

The field test (Cook et al. in press) of this HSI model would have been

impossible without the willingness of many individuals to provide assistance

and share their data. We sincerely appreciate the contributions and time

provided by the following individuals:

Bureau of Land Management, Colorado

Herb Connolly Craig

Kelly Sparks Craig

Bureau of Land Management, Idaho

Robert McCarty Idaho Fa 11 s

Bureau of Land Management, Wyoming

Bruce Baker

Harley Metz

Dave Roberts

Larry Saslaw

Andy Warren

Colorado Division of Wildlife

Mike Bauman

Charles Brown

John Ellenberger

John Gray

Thomas Pojar

Gene Schoonveld

Way ne Russe11

Department of Energy, Idaho

Tim Reynolds

Kemmerer

Kemmerer

Worland

Rawlins

Rawlins

Craig

Maybe 11

Grand Junction

Grand Junction

Fort Collins

Fort Collins

Fort Collins

Idaho Falls

vi

Idaho Fish and Game Department

Robert Autenrieth

Tracey Trent

Jerome

Idaho Falls

Montana Department of Fish, Wildlife, and Parks

Duane pyrah

University of Wvoming

Stanley Anderson

Larry Irwin

Archie Reeve

Jeffrey Yeo

U.S. Forest Service, Colorado

Steve Mighton

Lewistown

Laramie

La-ramie

Laramie

Laramie'

Greeley

Wyoming Game and Fish Department

John Emmerich

Walt Gasson

Dave Moody

Elaine Raper

Cole Thompson

Jim Yorgason

Lander

Cheyenne

Baggs

Green River

Worland

Cody

Appreciation is also expressed to Jim Yoakum, Bureau of Land Management,

who reviewed and provided comments on an earlier draft of this model. The

cover of this document was illustrated by Jennifer Shoemaker. Word processing

was provided by Carolyn Gulzow and Dora Ibarra. Barbara Cook provided computer

and secretarial assistance.

vii
PRONGHORN (Antilocapra americana)

HABITAT USE INFORMATION

General

The pronghorn (Antilocapra americana) is commonly found in association

with grasslands and sagebrush (Artemisia spp.) communities. In 1964, 62% of

North American pronghorn were associated with grasslands (41% shortgrass, 21%

mixed), 37% were on grassland-brushland [33% bunchgrass-sagebrush, 3% galleta

(Hilaria spp.)-woodland, 1% grama (Bouteloua spp.)-mesquite (Prosopis spp.)]

and 1% were associated with deserts (Yoakum 1972). The highest densities of

pronghorn occur on rangelands with an annual precipitation rate of 25.4 to

38.1 cm (10.0 to 15.0 inches) (Autenrieth 1978).

Food

Foods utilized by pronghorn vary seasonally depending upon the availability, palatability and succulence of vegetation (Hoover et al. 1959).

Vegetation consumed includes practically all available species although there

is a high preference for more succulent forage (Yoakum 1978). Pronghorn will

move from relatively dry ranges to more mesic sites in search of succulent

vegetation. When forbs are scarce, pronghorn select the most succulent

alternative browse available (Beale and Smith 1970).

The average annual diet of pronghorn in the short grass plains region of

Colorado was approximately 43% forbs, 40% browse, 11% cacti (Opuntia spp.),

and 6% grass (Hoover 1966). Cole and Wilkins (1958) presented data suggesting

simi lar annual dietary trends for pronghorn on grama-needlegrass-wheatgrass

(Bouteloua-Stipa-Agropyron) cover types in central Montana. However; Severson

et al. (1980) reported annual diets of 5% forbs, 3% graminoids, and over 90%

browse for sagebrush-grass ranges in central Wyomi ng. These data suggest

variable food habits dependent on availability throughout the range of pronghorn.

Cons i deri ng on ly food habits, ranges domi nated by approx i mate ly equal

proportions of forbs and browse, with some cacti and grasses, would provide

the highest carrying capacity for pronghorn (Hoover 1966). However, Yoakum

(1974) stated that the most important factor influencing high population

density antelope ranges in the Great Basin was that the range be in approximately 50% food production, consisting of approximately 40 to 60% grass, 10

to 30% forbs, and 5 to 10% in browse.

1
Browse was the most heavily utilized winter food by pronghorn in Alberta

even though its availability was extremely limited (Mitchell 1980). Browse

accounted for more than 90% of the winter diet of pronghorn in Utah (Beale and

Smith 1970), 93% of the winter diet in Montana (Bayless 1969) and 71.6% and

54.2% of the fall and winter diet, respectively, in Colorado (Hoover 1966).

Sagebrush, rabbitbrush (Chrysothamnus spp. ), and bitterbrush (Purshi a

tridentata) were identified as particularly important pronghorn forage in the

Great Basin (Yoakum 1982). Big sagebrush (A. tridentata), bitterbrush, and

saltbush (Atriplex spp.) were important pronghorn winter forage plants in

Montana (Bayl ess 1969). Bl ac k sagebrush (A. nova) was the most important

source of browse on pronghorn winter range- in---otah (Beale and Smith 1970).

Other important species were winterfat (Ceratoides lanata), brickellia

(Brickelli~ spp.), and Douglas rabbitbrush (f. VTSC,dTfTOrus).

Habitats domi nated by sagebrush have often been reported to be a key

component of northern pronghorn ranges (Dirschl 1963; Martinka 1967; Bayless

1969; Beale and Smith 1970; Barrett 1980). Pronghorn populations in Alberta

with access to winter ranges containing concentrations of sagebrush were more

stable than herds which inhabited ranges supporting lesser amounts of sagebrush

(Barrett and Vriend 1980). Dirschl (1963) indicated that abundance of shrubs

was a prime factor determining carrying capacity of winter ranges.

Spring is the only time of year when grasses appear to comprise a significant portion of the pronghorn's diet (Hoover 1966; Beale and Smith 1970).

The high protein content of early spring growth in grasses (Cook and Harris

1952; Fierro 1977) may be particularly beneficial to pronghorn at a time when

other forage species are of poor quality (Wallmo et al. 1977). Grass is also

consumed during green-up periods in warm weather (Bayless 1969). Grasses

other than wheat (Triticum aestivum) were found to be a relatively unimportant

component of the pronqhor n ' s diet in Kansas (Sexton et al. 1981). Pronghorn

in Utah were not observed to use dry, mature grass at any time (Beale and

Smith 1970).

Wheat was a major constant (74~~) of the November through April diet of

pronghorn living in the vicinity of green wheat fields in Colorado (Hoover

1966). At least 60% of the pronghorn diet in Kansas from October through

March was wheat (Sexton et al. 1981). The proportion of wheat in the diet

decreased to 1.7% by April. Pronghorn concentrated where they had access to

cropland and native vegetation during severe winter weather in Alberta

(Mitchell 1980), but did not consistently winter in areas which contained more

than 25% of the land area in cultivation (Barrett 1980). Sexton et al. (1981)

reported that pronghorn in Kansas inhabited areas consi sti ng of up to 30%

agricultural land. The amount of use of grain fields is dependent on their

proximity to native rangelands (Cole and Wilkins 1958). Grain fields in

Montana less than 0.8 km (0.5 mi) from native rangelands received greater use

by antelope, during all seasons of the year, than did fields more than 0.8 km

from rangelands.

2
Water

Water is a critical component of pronghorn ranges during summer and fall.

Pronghorn will drink water daily if it is available (Einarsen 1948). Ranges

which produce and maintain high pronghorn densities have water available every

1.6 to 8.0 km (1.0 to 5.0 mi) (Yoakum 1974). Sundstrom (1968) observed 95% of

over 12,000 pronghorn in Wyoming within a 4.8 to 6.4 km (3.0 to 4.0 mi) radius

from water. The maximum distance from pronghorn kidding sites in Alberta to

open water was less than 4.0 km (2.5 mi) (Barrett 1981), but the mean distance

was only 586 ± 31 m (641 ± 34 yd).

Water consumption by pronghorn has been reported to be inversely related

to the succulence of available forage (Beale and Smith 1970). Pronghorn were

not observed drinking water when forbs with a high moisture content were

abundant.

Pronghorn in Colorado were reluctant to drink from stock tanks; however,

they did drink overflow water (Hoover et al. 1959). Autenrieth (1978) reported

that pronghorn will utilize most facilities designed for livestock watering

and that such facilities should remain useable throughout the summer and fall

on northern ranges and year-round on southern ranges. Where natural water is

limited or absent, development of water sources may encourage better distribution of pronghorn.

Winter water requirements are often assumed to be provided by snow, but

unfrozen water sources may be important on ranges when snow is absent. Guenzel

et al. (1982) found that pronghorn distributions were strongly affected by an

unfrozen water source during a relatively snow-free winter in south-central

Wyomi ng. Wyomi ng Game and Fi sh Department emp 1oyees noted water stress in

pronghorns in areas with frequently long, snow-free periods in winter (Cook

1984). These areas received only about 0.7 cm (0.3 inches) of precipitation

per month in the winter.

Cover

Pronghorn typically inhabit land forms characterized by low rolling,

expansive terrain (Autenrieth 1978). Pronghorn were never observed for more

than a few minutes at a time where their view was restricted by terrain or

other natural features (Prenzlow et al. 1968). Kindschy et al. (1982) felt

that areas with less than 5% slope were optimum for pronghorn.

Microhabitats provided by topographic relief apparently increase habitat

qual ity during winter. Montana pronghorn selected microhabitats with more

favorable conditions during winter (e.g., lower wind velocities, less snow,

less dense snow), than the average for the whole area (Bruns 1977). During

the fall and winter pronghorn spent more time in basins 1.6 km (l mi) in

diameter than at other times of the year in Colorado (Prenzlow et al. 1968).

Amstrup (1978) occasionally observed pronghorn on slopes of 50% or more, but

only 7% of all observations were on slopes exceeding 20%. However, pronghorn

in Colorado did not move to sheltered environments such as groves of trees,

haystacks or large rocks, or into canyons during storms (Prenzlow et al.

1968) .

3
Topographic variation may also increase the probability that snow-free

foraging areas exist during winter. Pronghorn often frequent areas of reduced

snow accumulations (e.g., edges of ditches, creek beds, the lee side of thick

stands of sagebrush) for foraging during winter (Bruns 1977). When normal

winter feeding areas become snow-covered, pronghorn move to steeper windswept

areas where vegetation is more exposed (Einarsen 1948). Martinka (1967)

reported pronghorn dying of malnutrition during a severe winter when excessive

snow depths prohibited the use of coulees and restricted the animals to a

grassland type. Only minor losses occurred on winter ranges where big sagebrush and silver sagebrush (A. cana) were available on southern exposures and

windblown ridges. Winter concentrations of pronghorn in Alberta were often

observed in, and adjacent to, breaks and coulees which provided protection

from the wind, and increased availability of shrubs (Mitchell 1980). These

herds were sedentary for weeks at a time where microhabitats provided food and

shelter. Most pronghorn winter ranges. in Alberta were associated with drainage

systems containing abundant sagebrush (Barrett and Vriend 1980). High winds,

in areas of high topographic diversity, 'act to maintain snow-free feeding

sites, even in relatively severe winters (Ryder 1983).

Vegetat ion provi des cover for many 1arge ungul ates, but ta 11, dense

vegetation is of minimal value to pronghorn because of both limited visibility

and mobility. Rangelands with an average vegetation height of 61 cm

(24 inches) were less preferred than ranges averaging 38 cm (15 inches) (Yoakum

1978). Ranges supporting vegetation averaging 76 cm (30 inches) in height

were rarely used by pronghorn.

Reproduction

Einarsen (1948) described traditional pronghorn fawning areas in terms of

terrain characteristics and vegetation height. Optimal fawning grounds were

characterized as being situated in a basin, surrounded by a low ridge of

hills, where standing vegetation averaged 22.8 to 45.7 cm (9.0 to 18.0 inches)

in height. Although certain topographical and plant features appeared to

contribute to preferred parturition sites in Alberta, Barrett (1981) reported

no evidence indicating the existence of traditional fawning areas. Habitat

diversity provided by silver sagebrush, small depressions, and stands of forbs

and grasses 25.0 cm (9.8 inches) or taller, contributed to above average fawn

survival. Eighty-eight percent of the pronghorn fawns captured in the shortgrass prairie region of Colorado were located in the vicinity of washouts,

taller grass, or rocks (Prenzlow et al. 1968). Vegetation at daytime sites,

where pronghorn fawns less than 4 weeks of age were observed, was taller than

the vegetation in the surrounding area (Tucker and Garner 1980). No significant differences were noted between fawn-site vegetation and the height of

vegetation in the surrounding area for fawns older than 4 weeks.

Interspersion

Pronghorn home range size is dependent upon topography, the presence of

physical barriers, and the amount of forage available in the area (Bayless

1969). The area required depends upon the range having all of the habitat

requirements in sufficient qual ity and quantity for all seasons of the year

4
(Yoakum 1974). The geographic location and size of home ranges change throughout the year in a rhythmic pattern (Buechner 1950). The winter range may

include an area as large as 6.4 by 9.6 km (4.0 by 6.0 mi). Pronghorn in

Wyoming remained on an area of 2.6 to 5.2 km 2 (1.0 to 2.0 mi ") during the

summer and early fall, although dai ly movements covered from 0.2 to 0.6 km 2

(0.07 to 0.23 mi ") (Gregg 1955 cited by Q'Gara 1978). Pronghorn in Albe rta

remained relatively sedentary on their summer range and exhibited strong

fidelity for their natal range (Mitchell 1980).

The t imi ng and 1ength of movements of pronghorn vary with altitude,

latitude, weather and range conditions (Yoakum 1978). Movements are directly

related to seeking the basic habitat requirements of water and forage.

Differentiation of summer and winter ranges has been reported to be determined

by snow depth (Autenrieth 1978; Yoakum 1978). Pronghorn in Saskatchewan

regularly avoided areas where snow exceeded 18 cm (7 inches) in depth (Pyle

1972 cited by Mitchell 1980). Bruns (1977) stated that pronghorn may be

"opportunistic migrants" because herds may not migrate to definite wintering

areas each year. Pronghorn are believed to undertake migration only if forced

to do so as a result of extreme weather or habitat conditions. Such movements

would cease when more favorable habitat was reached, or a change occurred in

climatic conditions. The arrival and persistence of inclement weather during

the late fall prompted pronghorn in Alberta to move from the more open summer

and fall ranges to topographically diverse areas adjacent to water courses

(Mitchell 1980). Fall migration of Idaho pronghorn to winter ranges may not be

initiated by snow depth or storms, but rather by a decreased moisture content

of forage on higher elevation ranges (Hoskinson and Tester 1980). However,

snow depth was reported to influence the geographic location of winter ranges,

and the initiation and rate of movement back to the summer range. Bayless

(1969) reported that 50% of the antelope for which home ranges were calculated

were observed to " shiftll home ranges. Such movements were defined as movement

from the original area of activity to another area with no subsequent return

to the original area. The size of pronghorn home and seasonal ranges is a

result of habitat conditions and the influences of weather, thus, home range

data for the species seldom has application to other areas, or even to the

same range from year to year (O'Gara 1978).

Special Considerations

Compati bi 1i ty of ante lope and 1i vestock is re 1ated to the number of

animals using the same range, season of use, and forage condition (Autenrieth

1978). Based on dietary overlaps during the year, horses, cattle, and sheep

in Wyoming's Red Desert were similar in their food preferences, whereas

antelope food habits were dissimilar to those of domestic livestock (Olsen and

Hansen 1977).

Because the diets of cattle and pronghorn are sufficiently different

during the fall and winter there is little competition for forage (Salwasser

1980). Competition for spring grasses and forbs may result if heavy cattle

grazing occurs on pronghorn ranges prior to mid-May. Cattle also may compete

with pronghorn if heavy grazing is allowed on meadows within the summer range.

Cattle can have a positive impact on pronghorn habitats if their early summer

5
use of grasses favors the maintenance of annual forbs on spring and summer

ranges. Pronghorn in Texas do well on overgrazed cattle ranges because forbs

increase under such grazing conditions; however, sheep competed directly with

pronghorn by removing many palatable forbs (O'Gara 1978).

Sheep have the highest potential for dietary overlap and competition with

pronghorn (Severson et al. 1968; Salwasser 1980). Pronghorn abandoned a

Montana range used by sheep (Campbell 1970 cited by 0 1Gara 1978). Salwasser

(1980) recommended: 1) pronghorn winter ranges should not be grazed by sheep

to the extent that significant use of browse occurs; 2) sheep should be

excl uded from spri ng ranges until pronghorn have moved onto thei r summer

range; and 3) sheep should not be turned out on summer range until pronghorn

fawning is completed.

Fences on pronghorn ranges may restri ct movements and can be a di rect

cause of injury or mortality (Rouse 1962; Yoakum 1978; Salwasser 1980).

Fences may have significant impacts when constructed in migration routes or

where they interfere with daily movements to and from water or feeding areas

(Salwasser 1980; Yoakum 1980). Pronghorn exhibit some adaptabil ity to crawl

under, go through, or jump fences as the type of construction permits (Rouse

1962). There is a general concensus among pronghorn biologists that the

species usually will not jump over fences (Salwasser 1980). Citing BLM Manual

1737 (Bureau of Land Management 1975), Salwasser (1980) made the following

recommendations concerning fence construction: (1) fences on cattle ranges

should be constructed of three strands, with the top strand no higher than

97 cm (38 inches); the bottom wire should be barbless, and at least 41 em

(16 inches) above the ground; and (2) fences on sheep ranges should be

constructed of four strands with the hi ghest strand not exceedi ng 81 em

(32 inches) in height; the bottom wire should be barbless and at least 25 em

(10 inches) above the ground.

HABITAT SUITABILITY INDEX (HSI) MODEL

Model Applicability

Geographic area. This model has been developed chiefly for application

from the Great Basin to and including the Great Plains. Model assumptions

will be most realistic in regions where severe winter weather influences

pronghorn population characteristics. However, the model is probably applicable for habitat evaluation throughout the historic range of A. a. americana

(range: Great Plains of the United States and Canada, and the Great Basin).

This model is not applicable for habitat evaluation for A. a. mexicana (range:

isolated areas of southern Arizona, New Mexico, Texas;- and Mexico), A. a.

peninsularis (range: Baja California, Mexico), or ~. ~. sonorienses (range:

extreme southern Arizona to west-central Mexico). Figure 1 illustrates the

approximate geographic area for which this model is applicable.

Season. This model is applicable for the evaluation of pronghorn winter

range.

6
Figure 1. Approximate geographic area of applicability for the

pronghorn HSI model.

Cover types. This model was developed to evaluate habitat quality in the

fo 11 owi ng cover types (termi nology fo 11 ows that of U.S. Fi sh and Wi 1dl ife

Service 1981): Evergreen Shrubland (ES); Deciduous Shrubland (OS); Evergreen

Shrub Savanna (ESS); Deciduous Shrub Savanna (DSS); Grassland (G); Forbland

(F); and Cropland (C).

Minimum habitat area. Minimum habitat area is defined as the rm rn mum

amount of contiguous habitat that is required before an area will be utilized

by a species. The majority of pronghorn in North America now exist on ranges

which vary from 8 to 16 km (5 to 10 mi) in diameter (Yoakum 1978). However,

the minimum winter range area for pronghorn was not reported in the literature.

Several winter ranges used to evaluate the performance of this model (Cook

1984) were less than 30 km 2 (11.8 mi 2 ) in area. Based on this information it

is assumed that an area must provide a minimum of 30.0 km 2 (11.8 mt") of

contiguous habitat before it will be suitable as pronghorn winter range. A

30.0 km 2 (11.8 mi ") circle has a radius of 3.1 km (1.2 mi).

Verification level. A draft of this model was evaluated against pronghorn

population densities on 29 winter ranges in Colorado, Idaho, Montana, and

Wyoming (Cook et al. in press). After minor modifications in variable relationships, data analysis indicated that the model addressed important habitat

variables and explained 70% (P < 0.0001) of the variation in pronghorn

7
densities on the winter ranges evaluated. The current model contains the

modifications and improvements in variable relationships suggested during

ana lysis of the dra ft mode 1 .

Model Description

Overview. This model assumes that winter habitat characteristics are the

most limiting conditions affecting pronghorn distribution and abundance. We

have developed this model based on the assumptions that pronghorn survival and

reproduct i ve success are functions of wi nter food ava i 1abi 1i ty. Snow depth

and duration directly affect food availability on northern winter ranges. The

model attempts to characterize vegetation and topographic features favoring

food availability under mild to normal snow conditions. The model assumed

that snow will be available to meet pronghorn winter water requirements (see

Special consideration component).

The following sections provide documentation of the logic and assumptions

used to translate information on pronghorn habitat use to the variables and

equations used in the HSI model. Specifically, these sections cover:

(1) identification of habitat related variables; (2) definition and justification of the suitability levels of each variable; and (3) descriptions of the

assumed relationships between variables.

Winter food component. Pronghorn food habits vary on a regional and

local basis. The availability of adequate food is a critical winter life

requi site for the pronghorn in many areas of its geographi c range. Forbs

commonly comprise the major portion of the pronghorn's diet when evaluated on

an annual basis. Utilization of browse typically exceeds that of forbs during

the winter months. It is assumed that adequate spring/summer food will never

be more limiting to a pronghorn population than the quality and quantity of a

winter food source. This model has been developed chiefly for areas where

winter snow storms may have a major influence on habitat use and pronghorn

survival. Pronghorn populations inhabiting the southerly portions of the

continent may not be as dependent upon browse as a winter food source as are

northern populations.

Winter food characteristics of pronghorn habitat are assumed to be a

function of: (1) percent shrub crown closure; (2) the average height of the

shrub canopy; (3) the number of shrub species present; (4) percent herbaceous

canopy cover; and (4) to a limited degree the amount of available habitat in

winter wheat. The assumed relationships between shrub crown closure, shrub

height, shrub species diversity, and suitability index values for pronghorn

winter food quality are presented in Figure 2.

8
Fig. 2a Fig. 2b

1.0 1.0 .........

r- N

> > ....... ....... 0.8 V) Variable 2 0.8 V)

-

>< >< Q) 0.6 Q)

"'0 "'0 0.6 C C ....... .......

.j.J

» 0.4 .j.J

» 0.4 ...... ......

...... ...... ..Cl 0.2 ro ..Cl 0.2 ro .j.J .j.J ...... ...... ::::l ::::l V) 0.0 V) 0.0

a 25 50 75 100 a 6 12 18 24(in)

Percent shrub crown cover a 15.2 30.4 45.7 60.9(cm)

Average height of shrub

canopy

Fig. 2c

1.0

('V")

>.......

V) 0.8

><

Q)

"'0 0.6 c

.......

» 0.4

.j.J

......

......

..Cl 0.2 ro

+..l

......

::::l

V) 0.0

1 2 3 4 5

Number of shrub species

present per cover type

Figure 2. The relationships between shrub habitat variables and

suitability index (S1) values for pronghorn winter food quality.

9
An optimum wi nter food value for pronghorn is, in part, represented when

the percent shrub crown closure ranges from 15 to 30% (Fi g. 2a), and the

average height of the shrub canopy ranges from 20 to 46 em (8 to 18 inches)

(Fig. 2b). A shrub density and average shrub height exceeding 30% and 46 cm

(18 inches), respectively, are assumed to indicate less desirable habitat

quality due to interference with pronghorn mobility. Shrub cover 75% is

assumed to reflect unsuitable habitat conditions, regardless of average canopy

height. Average shrub height < 20 cm (8 inches) is assumed to represent less

desirable habitat quality due to decreased accessibility when snow is present

(Cook 1984).

The number of shrub species present (Fig. 2c) is also assumed to influence

an area's potential to provide a high quality winter food source. Cover types

containing four or more shrub species are assumed to represe~t optimum conditions. Homogeneous stands composed of only one species are assumed to have

lower potential in providing an adequate winter food source.

The abundance of herbaceous vegetation and availability of winter wheat

also are assumed to have an influence on the quality of a winter food source

for the pronghorn. Figure 3 displays the assumed relationships between herbaceous canopy cover and the availability of winter wheat, and suitability index

values for pronghorn winter food quality.

The presence of forbs and graminoids, in addition to shrubs, will often

provide maximum forage diversity. Figure 3a displays the assumed relationship

between the amount of herbaceous vegetation (graminoids plus forbs) present

and a suitability index for winter food. Optimum conditions are assumed to

exist when the herbaceous canopy coverage ranges from 10 to 40%. Herbaceous

vegetative density above and below the assumed optimum conditions will result

in lower SI values. Determination of a winter food value for pronghorn is

chiefly a function of shrub density, therefore the complete absence of

herbaceous vegetation will result in a lower food index value but will not

totally limit an area's winter food potential. Sites dominated completely by

herbaceous vegetation, 100% canopy closure, are assumed to have relatively low

potential for providing adequate pronghorn winter food.

Winter wheat in the vicinity of, or interspersed with, rangeland is

assumed to improve the winter food value for pronghorn if shrubs are present

at a density of 75% crown cover or less. Figure 3b displays the relationship

between the proportion of available habitat in winter wheat and a winter food

suitability index for the species. Optimum winter food may be obtained if

winter wheat is totally absent when shrub density and height are within optimum

ranges. It is assumed that optimum amount of winter wheat will range between

5 and 25% of the evaluation area. As the percent of the evaluation area in

winter wheat (including fallow) increases above 25%, habitat quality for

pronghorn is assumed to decrease. Evaluation areas consisting of 50% winter

wheat are assumed to provide no increased potential as winter food due to

decreased availability of shrub food sources.

10
Fig. 3a Fig. 3b

1.0 1.0

o:::T L(')

:> :> ...... 0.8 ...... V1 V1 0.8

X X OJ 0.6 OJ "0 0.6 Variable 4 "0

......

s:: s:: Variable 5 ......

>, 0.4 >,

+-> ..... 0.4 ...... ......

...... ...... .0 0.2 .0 ttl ttl 0.2 ..... ..... ...... ...... ::::l ::::l

V1 0.0 V1 0.0

0 25 50 75 lOa 0 25 50 75 100

Percent herbaceous canopy Percent of available habi ta t

cover in winter wheat

Figure 3. The relationships between herbaceous canopy cover and the

amount of available habitat in winter wheat to suitability index (SI)

values for pronghorn winter food quality.

The relationships between index values calculated using the curves

presented in Figures 2 and 3 are illustrated in Equation 1. Guidance for use

of the model in study areas that consist of more than one cover type is

provided in the Application of the Model section.

1/3 WF1 = [VI x (V z X V3 x V4 ) ] + Vs (1)

The density of shrubs, mean height of the shrub canopy, number of shrub

species present, percent herbaceous canopy cover and the percent of the evaluat i on area in wi nter wheat all function to defi ne a wi nter food value for the

pronghorn. Percent shrub crown cover (SIVI) has the greatest i nfl uence in

determination of a winter food value in the above equation. The values

calculated for average shrub canopy height (SIVz ) , number of shrub species

present (SIV3 ) , and percent herbaceous canopy closure (SIV4 ) are assumed to be

equa 1 in thei r value for the determi nat i on of a wi nter food va1ue. The

geometric mean of these three SI values has a direct influence on the SI value

calculated for SIV I, percent shrub crown cover. The percent of available

pronghorn habitat in winter wheat (SIVs ) may serve to slightly increase the SI

va1ue ca 1cul ated for naturally occurri ng vegetation. However, the structure

of equation 1 permits an optimum value to be obtained in the complete absence

of wi nter wheat.

11
Cover component. Pronghorns typically inhabit ranges which are characterized as being expansive and low rolling. Ridges, rims, and depressions are

used as thermal and escape cover and may contribute to greater diversity in

food resources and foraging areas. Figure 4 displays the assumed relationships

between mean topographic diversity and a cover index (Cl) for the pronghorn.

Flat terrain is assumed to have a relatively low value for providing

suitable winter cover conditions. Diverse terrain comprised of rolling topography, or ridges and rims, is assumed to provide high qual i ty winter cover.

Steep, broken, or mountainous terrain is assumed to have minimum potential as

suitable winter cover for the species.

I

- ..

.

-

1.0

-\.0

::>

......

(/) 0.8

x

OJ

"'0 0.6 I::

......

>,

-l-' 0.4 'rr-

'r-

..Cl

to 0.2 -l-'

'r-

::s

(/) 0.0

A B C o

A)

B)

C)

D)

0-2% slope; flat or

nearly so

3-8% slope; gently rolling

9-25% slope; substantial

drainages, ridges, and/or

rims present

> 25% slope; mountainous

Mean topographic diversity

Figure 4. The relationship between mean topographic diversity and

cover index value for pronghorn winter range.

Application of this model requires that a winter food/cover value be

determined by combining the cover and winter food index values. Equation 2 is

used to calculate the combined winter food/cover index (WFC1) for the

pronghorn.

WFCl (2)

The winter food index and cover index are assumed to have equal value in

determining the overall winter food/cover index value for the pronghorn.

12
Model Relationships

HSI determination. The calculation of a Habitat Suitability Index for

the pronghorn considers the life requisite values obtained for winter food/

cover (equation 2). The HSI is equal to the winter food/cover value.

Summary of model variables. Six habitat variables are used in this model

to determine winter food/cover life requisite values for the pronghorn. The

relationships between habitat variables, the winter food/cover index, cover

types, and an HSI value are summarized in Figure 5.

Application of the Mod~

We recommend determining canopy cover of vegetation classes using the

line intercept method. This method is relatively accurate, especially for

shrubs (Pieper 1978). Model variables are calibrated based partially on data

collected using this method. Other sampl ing techniques may produce markedly

different cover estimates.

Cook (1984) separated ha1f shrubs and true shrubs, and combi ned the

former class with estimates of herbaceous canopy closure, during field testing

of the model. Half shrubs are defined as species generally less than 15 cm

(6 inches) in height, and which die back to a woody base each year. Examples

of half shrubs include fringed sagewort (~. frigida) and saltsage (Atriplex

nuttallii) (Table 1). Half shrubs were treated in this manner because it is

assumed that their growth form and dormancy pattern more closely simulates the

availability of forbs and graminoids in winter, than that of true shrubs.

Figure 6 provides variable definitions and suggested measurement

techniques (Hays et al. 1981).

This model may be used to determine HSI values for evaluation areas

comprised of one cover type or for areas comprised of several cover types. In

situations where two or more noncropland cover types are present within the

evaluation area an overall weighted HSI (weighted by area) can be determined

by performing the following steps:

1. Stratify the evaluation area into cover types.

2. Determine the area of each cover type and the total area of the

evaluation area.

3. Determine SI values for all variables except Vs , percent of available

habitat in winter wheat, for each noncropland cover type in the

evaluation area. If present, determine the proportion of the evaluation area comprised of fallow and planted winter wheat fields

(V s ) . Variables other than Vs and V6 do not require measurement in

cropland cover types.

13
4. Determine a WF1 value for each noncropland cover type using the 51

values derived in step 3 and equation 1, excluding Vs .

5. Multiply the area of each cover type by its respective WFI value,

sum these products, and divide the sum by the total area of all

cover types including areas planted to winter wheat. Then add t he

51 value for Vs (percent of available habitat planted to winter

wheat) to determine the weighted WF1.

6. Determine a cover index (Cl) value for each cover type, including

croplands using Figure 4.

7. Multiply the area of each cover type by its respective C1 value, sum

these products, and divide the sum by the total area of all cover

types to obtain the weighted C1 value.

8. The H51 value is determined by averaging the WF1 and C1 values. The

steps outlined above are expressed by the following equations:

weighted WF1 =

n

L WFI;A i i=l

n

L A.

i =1 1

+ 51 value of Vs

where n = number of cover types

WF1. = winter food index value of individual noncropland cover type 1

A. = area of cover type ; 1

C1.A.

1 1

weighted C1 =

n

L

i=l

n

L

i=l

A.

1

where n = number of cover types

C1. = cover index value derived from Figure 4 for each cover type 1

A. = area of cover type i

1

14
Va r iab Ies Cover types Life requisites

% shrub crown closure ,

Winter

food/cover HSI

Number of shrub species =:;) All ""'-- present per cover type

Average height of shrub canopy~

% herbaceous canopy cover /

% of available habitat I

in winter wheat

I-'

U1

Topog ra ph i c dive rs i ty AI I /

Figure 5. Relationships of habitat variables, life requisites, and cover types

to the HSI for pronghorn winter range.
Table 1. Shrubs and half-shrubs encountered on 29 pronghorn

winter ranges used to evaluate HSI model performance (Cook

1984).

Scientific name

Shrubs:

Artemisia arbuscula

Artemisia cana

Artemi s i a fiTIfo 1'ia

Artemisia longiloba

Artemisia nova

Artemisia tridentata tridentata

Artemisia tridentata vaseyana

Artemisia tridentata wyomingensis

Atriplex confertifolia

Chrysothamnus nauseosus

Chrysothamnus viscidiflorus

Grayia spinosa

Purshia tridentata

Rhus trilobata

5arCobatus vermiculatus

Symphoricarpos spp.

Tetradymia canescens

Tetradymia spinosa

Half-shrubs: a

Artemisia frigida

Artemisia pedatifida

Artemisia spinescens

Atriplex nuttallii

Ceratoides lanata

Chrysothamnus greenei

Gutierrezia sarothrae

Kochia americana

Tanacetum nuttallii

Common name

Low sagebrush

Silver sagebrush

Sand sagebrush

Alkali sagebrush

Black sagebrush

Basin big sagebrush

Mountain big sagebrush

Wyoming big sagebrush

Shadscale

Rubber rabbitbrush

Douglas rabbitbrush

Spiny hopsage

Antelope bitterbrush

Skunkbush

Black greasewood

Snowberry

Gray horsebrush

Catclaw horsebrush

Fringed sagewort

Birdfoot sagebrush

Bud sagebrush

Saltsage

Wi nterfat

Rabbitbrush

Broom snakeweed

Red sage

Chicken sage

aAl l half-shrubs listed were classified as either subshrubs or woody-based

perennials by either Dorn (1977), or Hitchcock and Cronquist (1976), except

C. greenei which was not specifically classified.

16
Variable (definition)

Percent shrub crown

closure [the percent

of the ground that is

shaded by a vertical

projection of the

canopies of woody

vegetation 5 m

(16.5 ft) in height].

Average height of shrub

canopy [the average

vertical distance from

the ground to the highest

point of all woody plants

5 m (16.5 ft) tall].

Number of shrub species

present per cover type

[a tally of individual

shrub species that are

present at 1% canopy

closure, (woody vegetation 5 m (16.5 ft)

in height) encountered

within each specific

cover type sampled].

Cover type~

ES,DS,ESS,DSS,

G,F

ES,DS,ESS,DSS,

G, F

ES,DS,ESS,DSS,

G,F

Suggested technique

Line intercept

Line intercept,

graduated rod

Line intercept

V.. Percent herbaceous

canopy cover [the

percent of the ground

surface that is shaded

by a vertical projection

of all nonwoody vegetation (grass, forbs,

sedge, etc.)].

Percent of available

habitat in winter wheat

(the proportion of the

evaluation area considered to be potential

pronghorn habitat that

is devoted to the production of winter wheat).

Topographic diversity

[an appraisal of land

surface structure

(see variable for

category descriptions)].

ES,DS,ESS,DSS,

G,F

C

ES,DS,ESS,DSS,

G,F,C

Line intercept

Remote sensing,

on-site inspection

Remote sensing,

topographic maps

Figure 6. Definitions of variables and suggested measurement techniques.

17
Special consideration component. Fences on pronghorn ranges may restrict

movements and may have significant impacts if they obstruct migration routes.

It is assumed that fences constructed of woven wire, or four or more strands

of barbed wire, with bottom strand less than 25.4 cm (10.0 inches) above the

ground will have the most impact on pronghorn movements. It is also assumed

that if the study area is fenced into allotments 2.59 km 2 (1.0 mi 2 ) pronghorn

movements will be hindered. If either of the above situations exist within

the study area, then the Suitability Index for winter food/cover life requisite

value should be decreased by one-half. If fences occur infrequently, or meet

the quality described in the Special Considerations portion of the Habitat Use

Information section of this model, little to no detrimental impact is assumed

to occur.

Available water is a mandatory requirement for ranges to be of optimum

value. Pronghorn will utilize naturally occurring water sources, stockponds,

or 1i vestock wateri ng devi ces if unfrozen. Wi nter water requi rements are

norma lly met by snowfa 11; however, the avail abi 1i ty of water duri ng snow-free

periods may influence pronghorn distribution and habitat use on some ranges.

Insufficient data exist to develop a variable reflecting habitat suitability

as a function of the interaction of unfrozen water sources and winter precipitation. However, unfrozen water sources may be crucial in areas receiving

less than 1.0 cm (0.4 inches) of precipitation per winter month (Cook et al.

in press). Model ratings of habitat quality may be suspect (i.e., too high)

in low precipitation areas which lack available, free water in winter. We

assume that three evenly-spaced open water sources per 100 km 2 (39 mi ") are

requi red by pronghorn on ranges routine l y experi enci ng extended snow-free

periods.

Snow distribution and accumulation are assumed to also influence forage

ava i 1abi 1i ty on northern wi nter ranges. However, we do not fully understand

the causal relationships involved. This model was evaluated using field data

from wintering areas known to be consistently used by pronghorn in mild to

normal snowfall winters, and population estimates obtained in mild to normal

winters. Therefore, technically speaking, the model's ability to rate the

va 1ue of pronghorn wi nter ranges duri ng severe snow condi t ions has not been

evaluated. We have attempted to partially address the issue of severe snow

conditions through a treatment of topographic diversity. Areas which support

a combination of windblown ridges with short shrubs, and drainages with dense,

tall shrubs evidently provide a variety of foraging opportunities for pronghorn

regardless of weather conditions (King 1979 in Cook 1984; Ryder 1983). Other

factors, such as southern aspects also may be important during severe snow

conditions (Martinka 1967). Users should be aware that there may be other

factors, not addressed in this model, which affect the value of winter ranges

for pronghorn use during severe snow conditions.

SOURCES OF OTHER MODELS

Kindschy et al. (1982) provide evaluation criteria and a work sheet for

rating pronghorn habitat potential in the Great Basin.

18
REFERENCES

Amstrup, S. 1978. Activities and habitat use of pronghorn on Montana-Wyoming

coal lands. Pages 270-306 in R. Autenrieth, ed. Proc. Eight Biennial

Pronghorn Antelope Workshop,lMay 2-4, 1978, Jasper, Alberta, Canada.

Autenrieth, R. 1978. Guidel ines for the management of pronghorn antelope.

Pages 473-526 in R. Autenrieth, ed. Proc. Eight Biennial Pronghorn

Antelope Workshop, May 2-4, 1978, Jasper, Alberta, Canada.

Barrett, M. W. 1980. Seasonal habitat associations of pronghorn in Alberta.

Pages 174-195 in J. S. Phelps, chairman. Proc. Ninth Biennial Pronghorn

Antelope Workshop, April 7-10, 1980, Rio Rico, AZ.

1981. Environmental characteristics and functional significance of pronghorn fawn kidding sites in Alberta. J. Wildl. Manage.

45( 1): 120-131.

Barrett, M. W., and H. G. Vriend. 1980. Management implications of the

seasonal distribution of pronghorn and land use practices in Alberta.

Pages 196-214 in J. S. Phelps, chairman. Proc. Ninth Biennial Pronghorn

Antelope Workshop, April 7-10, 1980, Rio Rico, AZ.

Bayl ess, S. R. 1969. Wi nter food habi tats, range use, and home range of

antelope in Montana. J. Wildl. Manage. 33(3):538-551.

Beale, D. M., and A. D. Smith. 1970. Forage use, water consumption, and

producti vi ty of pronghorn antelope in we stern Utah. J. Wildl. Manage.

34(3):570-582.

Bruns, E. H. 1977. Winter behavior of pronghorn in relation to habitat. J.

Wildl. Manage. 41(3):560-571.

Buechner, H. K. 1950. Range ecology of the pronghorn on the Wichita Mountains

Wildlife Refuge. Trans. N. Am. Wildl. Conf. 15:627-643.

Bureau of Land Management.

Manage., Washington, DC.

1975. Manual 1737 - fencing.

17 pp.

U.S. Bur. Land

Campbell, R. B. 1970. Pronghorn, sheep and cattle range relationships in

Carter County, Montana. M.S. Thesis. Montana State Univ., Bozeman.

87 pp. Cited by OlGara 1978.

Cole, G. F., and B. T. Wnkins. 1958. The pronghorn antelope, its range use

and food habits in central Montana with special reference to wheat.

Montana Fish Game Dept. Tec~. Bull. 2. 39 pp.

Cook, C. W., and L. E. Harris. 1952. Nutritive

crested wheatgrass on spring ranges of

5(5):331-337.

19

value

Utah.

of cheatgrass and

J. Range Manage.
Cook, J. G. 1984. Pronghorn winter ranges: Habitat characteristics and a

field test of a habitat suitability model. M.S. Thesis. Univ. Wyoming,

Laramie. 91 pp.

Cook, J. G., L. L. Irwin, A. W. Allen, and M. J. Armbruster. In press. A

field test of a winter pr-cnchorn habitat suitability index model. In

C. K. Winkler (chairman), Pr oc , Eleventh Biennial Pronghorn Antelope

Workshop, April 10-12, 1984, Corpus Christi, Texas.

Dirschl, H. F. 1963. Food habits of the pronghorn in Saskatchewan. J.

Wildl. Manage. 27(1):81-93.

Darn, R. D. 1977. Manual of the vascular plants of Wyoming. Vol. I and II.

Garland Publ., Inc., New York. 1,498 pp.

Einarsen, A. S. 1948. The pronghorn antelope and its management. Wildl.

Manage. Inst., Washington, DC. 235 pp.

Fierro, L. C. 1977. Influence of livestock grazing on the regrowth of crested

wheatgrass for winter use by mule deer. Utah Div. Wildl. Resour. Publ.

77-14.

Gregg, H. A. 1955. Summer habits of Wyoming antelope. Ph.D. Diss. Cornell

Univ., Ithaca, NY. 185 pp. Cited by OIGara 1978.

Guenzel, R. J., L. L. Irwin, and T. J. Ryder. 1982. A comparison of pronghorn

movements and distribution during a normal and a mild winter in the Red

Rim Area, Wyoming. Pages 156-173 in J. V. McKenzie, chairman. Proc.

Tenth Biennial Pronghorn Antelope Workshop, April 5-7, 1982, Dickinson,

ND.

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

variables. U.S. Fish Wildl. Servo FWS/OBS-81/47. 173 pp.

Hitchcock, C. L., and A. Cronquist.

Univ. Washington Press, Seattle.

1976. Flora of the Pacific Northwest.

730 pp.

Hoover, R. L. 1966. Antelope food habits and range relationships in Colorado.

Proc. Antelope States Workshop 2:75-85.

Hoover, R. L., C. E. Till, and S. Ogilvie.

Colorado Dept. Fish Game Tech. Bull. 4.

1959. The antelope of Colorado.

110 pp.

Hoskinson, R. L., and J. R. Tester. 1980. Migration behavior of pronghorn in

southeastern Idaho. J. Wildl. Manage. 44(1):132-144.

Kindschy, R. R., C. Sundstrom, and J. D. Yoakum. 1982. Wildlife habitats in

managed rangelands--the Great Basin of southeastern Oregon. U.S. For.

Servo Pacific Northwest For. and Range Exp. Sta., Gen. Tech. Rep.145.

18 pp.

20
King, C. 1979. Annual big game herd unit reports. District II, Cody,

Wyomi ng. On fil e with the Wyomi ng Game and Fi sh Dept., Cheyenne, WY.

Cited by Cook 1984.

Martinka, C. J. 1967. Mortality of northern Montana pronghorn in a severe

winter. J. Wildl. Manage. 31(1):159-164.

Mitchell, G. J. 1980. The pronghorn antelope in Alberta. Univ. Regina,

Regina Saskatchewan, Canada. 165 pp.

OIGara, B. W. 1978. Antilocapra americana. Mammal. Spec. 90:1-7.

Olsen, F. W., and R. M. Hansen. 1977. Food relations of wild free roaming

horses to 1i vestock and bi g game, Red Desert, Wyomi ng. J. Range Manage.

30(1): 17-20.

Pieper, R. D. 1978. Measurement techniques for herbaceous and shrubby vegetation. Dept. Animal, Range Sci., New Mexico State Univ., Las Cruces.

148 pp.

Prenzlow, E. J., D. L. Gilbert, and F. A. Glover. 1968. Some behavior

patterns of the pronghorn. Colorado Dept. Game Fish and Parks, Spec.

Rep.. 17. 16 pp.

Pyle, W. H. E. 1972. Range vegetation characteristics, fall and winter

habi tat uti 1i zation, food habi ts and behavi or of pronghorn antelope on

the Peapot Winter Range, Peapot, Saskatchewan. M.S. Thesis. Univ.

Regina, Regina, Saskatchewan. 200 pp. Cited by Mitchell 1980.

Rouse, C. H. 1959. Antelope range relationships. Trans. Int. Antelope Conf.

10:4-9.

1962. Antelope and sheep fences. Trans. Int. Antelope Conf.

13: 45-47 .

Ryder, T. J.

Wyoming.

1983. Winter habitat selection of pronghorn in south-central

M.S. Thesis. Univ. Wyoming, Laramie. 65 pp.

Sa lwasser, H. 1980. Pronghorn ante lope popul at i on and habi tat management in

the Northwestern Great Basin environments. U.S. For. Serv., Pacific

Southwest Region. 63 pp.

Severson, K., M. May, and W. Hepworth. 1968. Food preferences, carryi ng

capacities, and forage competition between antelope and domestic sheep in

Wyoming's Red Desert. Sci. Monogr. Agric. Exp. Sta., Univ. Wyoming,

10:1-51.

Sexton, M. L., J. R. Choate, and R. A. Nicholson. 1981. Diet of pronghorn in

western Kansas. J. Range Manage. 34(6):489-493.

21
Sundstrom, C. 1968. Water consumption by pronghorn antelope and distribution

related to water in Wyoming's Red Desert. Proc. Antelope States Workshop

3:39-46.

Tucker, R. D., and G. W. Garner. 1980. Species composition and physical

characteristics of pronghorn antelope fawn daytime bedsites. Soc. Range

Manage. Annu. Meeting 33:45. Abstract only.

U.S. Fish and Wildlife Service. 1981. Standards for the development of

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

Ecol. Servo n.p.

Wallmo, O. C., L. H. Carpenter, W. L. Regelin, R. B. Gill, and D. L. Baker.

1977. Evaluation of deer habitat on a nutritional basis. J. Range

Manage. 30(1):122-127.

Yoakum, J. 1972. Antelope - vegetative relationships. Proc. Antelope States

Workshop 5:171-177.

1974. Pronghorn habitat requirements for sagebrush-grasslands.

Proc. Antelope States Workshop 6:16-25.

1978. Pronghorn. Pages 103-121 in J. L. Schmidt and D. L.

Gilbert, eds. Big game of North America, ecology and management.

Stackpole Books, Harrisburg, PA. 494 pp.

1980. Habitat management guides for the American pronghorn

antelope. U.S. Bur. Land Manage. Tech. Note 347. 77 pp.

1982. Managing vegetation for pronghorns in the Great Basin.

In S. B. Monsen and N. Shaw, compilers. Managing intermountain

rangelands-improvements of range and wildlife habitats. Symp. Proc.,

Sept. 15-17, 1982, Twin Falls, Idaho, June 22-24, 1984, Elko, Nevada.

22
50272 -, 01

REPORT DOCUMENTATION

PAGE

1 REPORT NO.

FHS/OBS-82/l0.65

, 2. IJ. Recipient's ",cces.ion No.

I

!

4. Title and Subtitle

Habitat Suitability Index Models: Pronghorn

5. Report Date

June 1984 6.

7. ",ut\'lor(s)

Arthur W. Allen, John G. Cook and Michael J. Armbruster

8. l'el1orming Organization Rept. No.

(Gl

«»

10. I'roieet/Task/Work UnIt No.

11. ContractlCl or GrantlGl No.

1

9. l'el1orming Organization Name and ",ddress

Western Energy and Land Use Team Dept. of Zoology and Physiology

! U.S. Fish and Wildl ife Service Universi'ty of Hyoming ~------------f

Drake Creekside Building One Laramie, WY 82071

2627 Redwing Road

Fort Collins, CO 80526-2899

12. SlIonsorinc Organization Name and ",ddre.s

Western Energy and Land Use Team

Division of Biological Services

Research and Development

13. Type of Report & Period Covered

Fish and Wildlife Service

U.S. Dept. of the Interior

Washington, D.C. 20240 1~

115. Supplementary Notes

I

·115. ",bstraet lLlmit: 200 words)

This is one of a series of publications that provide information on the habitat

requirements of selected fish and wildlife species. Literature describing the

relationship between habitat variables related to life requisites and habitat

suitability for the pronghorn (Antilocapra americana) are synthesized. These

data are subsequently used to develop Habitat Suitability Index (HSI) models.

The HSI models are designed to provide information that can be used in impact

assessment and habitat management.

17. Document Anelysis a. Descriptors

Ungalata

~ri 1dl ife

Habitabi 1ity

Mathematical models

b. Identlfiers/Open·Ended Terms

Pronghorn

Antilocapra americana

Habitat suitability

Instream Flow Incremental Methodology c. COSATI ;:;ald/Group

I

I 18. ",veilabillty Statement

Release Unlimited \

19. S.curity Ctass (This Reportl

Unclassified

ZO. SecUrity Class (This Pege)

Unclassified

21. No. of Page.

22 I 22. Price

I

(S.. ANSI-l39.18l S.e InstructIon. on Rever•• OPTIONAL FORM 272 (4-71)

(Formerly NTI~35l

Department of Commerce

:., US. GOVERNMENT I'RINTING OFFICE: 1984-781-2023/9491 REGION NO.8
.... ,.... ...

1:l Hea<JQuarter,. DIVIStOn ot BiologIcal

Semces Washington, DC

)( Eastern Energy and Land Use Team

Leetown WV

.. NatIonal Coastal Ecosystems Team

Slidell LA

• Weslern Energy and Land Use Team

Fl Collins CO

• Locations 01 RegIonal Olhces

Habitat sUItability index lIodels : 24959

Allen, Art..r r11 .11IIIIIIIIIII\llf'I ,U51no, i2

,

I

I __r----

61

,----- L, J_

I : 1----

I I

I

Puerto RICO and

CJ~ ·:

Virgin 'slands

...,..

REGION 1

Regional Director

U.S. Fish and Wildlife Service

lloyd Five Hundred Building, Sufie 1692

500 N.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

REGION 2

Regional Director

U.S. Fish and WildlifeService

P.O. Box 1306

Albuquerque, New Mexico 87103

REGION S

Regional Director

U.S. Fish and Wildlife Service

One Gateway Center

Newton Comer, Massachusctts 02158

REGION 7

R~ODaJ Diftetor

us. Fillh and Wildlife Service

1011 l-:. Tudor Road

Anchora., Alaska 99503

REGION 3

Regional Director

U.S. Fish and Wildlife Service

Federal Building. Fort Snelling

Twin Cities, Minnesota 5$ III

REGION 6

Regional Director

U.S. Fish lII'IQ Wildlife Service

P.O. Box 25486

Denver Federal Center

Denver, Colorado 80225
DEPARTMENT OF THE INTERIOR

u.s. FISH AND WILDLIFE SERVICE

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

fostering the wisest use of our land and water resourcn. protecting our fish and wildlife,

preservinl th..environmental and cultural values of our national par~ and historical places.

and providing for the enjoyment of life throulh outdoor recreation. The Department as·

sesses 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.