1982

EDtlWS

FILE COPY

ROBERTR.KlNDSCHY

CHARLESSUNDSTROM

JAMESD.YOAKUM

PACIFIC N~RTRWEST FOREST AND RANGE EXPERIMENT STATION

FOREST SERVICE U. S. DEPARTMENT OF AGRICULTURE i
ABSTRACT

The sagebrush steppe of the Great Basin in

southeastern Oregon is peripheral habitat for

pronghorns, but the quality of the habitat can be

improved through rangeland management. The

relationship between pronghorns and their habitat components-the availability of water, type

of forage, barriers that restrict the movement of

herds, and theeffect of grazing by livestock-are

discussed. A worksheet is provided that can be

used by range managers to rate the quality of a

range as pronghorn habitat. Methods of altering

habitat to benefit pronghorns are given.

THE AUTHORS

ROBERT R. KINDSCHY is a wildlife biologist,

U.S. Department of the Interior, Bureau of Land

Management, I?O. Box 700, Vale, Oregon 97918.

CHARLES SUNDSTROM is a wildlife biologist,

U.S. Department of Agriculture, Forest Service,

P.O. Box 1628, Juneau, Alaska 99802. JAMES D.

YOAKUM is a wildlife biologist, U.S. Depdrtment of the Interior, Bureau of Land Management, stationed at RenewableNatural Resources,

Iiniversity of Nevada, Reno, Nevada 89512.
This puh!icat ion is part of the series Wildlife

Habitats in Managed Rangelands-The

asin of Southeastern Oregon. The

urpose of the series is to provide the necessary

Iformation on xildlife and its relationship to

abitat conditions in managed rangelands in

rder that the range manager may make full!

iformed decisions.

treatment of a specific subject, when combined

in sequence, the individual parts will be ar

chapters in ;I book.

Incliviclual parts ~,ill be printed as they hecome

ax~;~ilable. In this \~a\- the information will lx

more‘ quickly at;~ilable to potential users. This

means, ho-+vcyer, that the sequence of printing

\vill not 1~ in the same order as the final

organization of the separatrs into a comprchrnsi\,e whole.
Introduction

Grazing by domestic livestock alters rangeland ecosystems in the Great Basin of southeastern Oregon more than any other humanly

controlled activity. Such alteration, coupled with

increasing human activities, produces changes

that affect pronghorns (Antilocapra americana),

sometimes called pronghorn antelope. Land managers and land use planners find it increasingly

necessary to forecast and display the consequences of management activities on pronghorns.

Primary impacts on pronghorn habitat have

resulted from livestock management that alters

structural conditions and botanical composition

of plant communities. These alterations produce

distinct habitat components of differing quality.

This chapter shows the relationship between

the pronghorn and its habitat in the sagebrushgrasslands of southeastern Oregon; the principles should also apply to other shrub-dominated

rangelands used by pronghorns. The information can be used for both short- and long-range

land use planning.

Literature review and consultation with wildlife biologists provided data that formed the framework for relating pronghorns to their habitat

requirements. Where data were lacking, the best

judgment of the authors prevailed.

ssumptions

The management tips provided are based on

the following information or assumptions:

1. The sagebrush steppe of the Great Basin is

peripheral pronghorn habitat (Yoakum 1968)

(fig. 1). From reports of early explorers, we

conclude that pronghorns were more abundant

on the midcontinent short-grass prairies than in

the Great Basin (Burroughs 1961, Fremont 1843,

Thwaites 1904). Habitat components that limit

populations, however, can be manipulated to

benefit pronghorns (Yoakum 1978a, 1978b).

2. Pronghorns evolved to be compatible grazers with other native herbivores, especially bison

(Olson hison)(Yoakum 3978b). Grazing by these

native herbivores changed the composition of

the vegetation on grassland ranges of North

America to favor pronghorns.

Figure 1.--A pronghorn herd on open sagebrush

steppe in Lake County. Oregon. (Photograph by James

Yoakum.)

3. Forage and drinking water are the primary

components of pronghorn habitat. Forage can be

improved on ranges in less-than-optimum condition for pronghorns. Water distribution can be _

improved on some pronghorn rangelands [/

(Yoakum 1978a). “;_

4 . Pronghorn ranges contain a variety of plant

communities differing in height, composition,

and forage production.

5. Pronghorn densities are influenced primari

ly by habitat conditions (Yoakum 1978a).

6. Favored habitats can be identified by comparing pronghorn densities between habitats

(Sundstrom and others 1973).

7. Rangelands with a mixture of grasses.

forbs, and shrubs of low structure provide the

best pronghorn habitat (Yoakum 1972).

8 . Agricultural crops other than alfalfa (Med.

cage sativa) are rarely eaten by pronghorns.

9. Fences, especially those of woven wire, frequently form barriers to pronghorn movement

(U.S. Department of the Interior, Bureau of Land

Management 1974).

10. The welfare of pronghorns can be enhanced by providing for their needs in range

management activities (Yoakum 1978a).

i

,

2
Habitat Requirements

Pronghorn densities in the Great Basin avere less than 0.4 per square kilometer (1.0 mi2)

)akum 1968). Variations in density are related

vegetation and water, which are, in turn,

ated to precipitation and soils (fig. 2). Yoakum

174) described the following habitat requirents for pronghorn on sagebrush-grasslands.

ABIOTIC FACTORS

wwwhy

Pronghorns are adapted to low rolling topog3hy with few slopes more than 30 percent in

lde. Within such landforms, there arecircummces to which pronghorns adjust by modify-

; their behavior. Depending on topography,

ne herds do not move in response to season;

me move relatively short distances with

ange of season and then move even longer

tances in response to climatic conditions,

:h as increasing snow depth.

tural Barriers

vatural barriers to movement include bodies

water, escarpments, mountains, canyons, and

,as of tall shrubs or forest, sometimes account-

: for isolated, unoccupied habitats that are

lerwise suitable (Einarsen 1948).

vation

‘ronghorn ranges occur from sea level to

153 meters (11,000 ft) but occurrence at sea

el in Mexico and in alpine meadows in Oregon

1 Wyoming is rare (fig. 3). The largest populaas, particularly in the Great Basin, are beZen elevations of 1 220 and 1 830 meters

IOO-6,000 ft) (Yoakum 1974).

mate

:he highest densities, which reflect the best

litats, occur where precipitation averages

38 centimeters (lo-16 in) per year. Pronghorn

other precipitation zones do reproduce, but

y maintain lower densities (Sundstrom and

ers 1973, Yoakum 1972).

Forb ground co”er

:::::::::::::::::::ws

::::::.:.:...:.:.:.:.y.j$:::: :.:.:.:.: :.:.:.:.:.: .,:,i., I I I 8 I I I I

0 10 20 30 40 50 60 70 80 90 1 00 II r ,

Shrub ground cnver

I 1 t I

0 25 51 76 102 127cm

10 20 30

Vegetative height

40 50in

..vA:...:.: .,.,.,.,.,. .__,.,.,. ..v... i.. . . .

.. ...A.. .. ....ii/...... . .. . .. . ....

‘.:.:.jjjji::~:~:~:.

. . . . . . n . . / I I I

,

0 1.6 3.2 4 0 6.4 80km

1 2 3 4 5 mi

Distance from water

Figure Z.-Components of pronghorn habitat in the

sagebrush steppe. Habitat becomes optimum when all

components occur together within the bounds marked

by bars.

V /

I r 7-

‘ I i ! /

XJTLINE OF ORIGINAL RANGE

?ANGEOCCUPlED IN 1970

Figure 3.-Distribution range of American pronghorns. the original range denotes only peripheral

boundaries because not all areas within it were

inhabited. (Adapted from Yoakum 1980).
Whenever Great Basin ranges receive a snow

accumulation over 25 to 30 centimeters (10 to

12 in), pronghorns have difficulty obtaining

forage. Prolonged periods of such snows are

detrimental when one or more of the following

occur: low quantity or quality of forage, high

winds, and barriers to movement (Bruns 1977,

Riddle and Oakley 1973, Sundstrom 1969).

Temperature is usually not a limiting factor.

Fawns may die, however, from unseasonable

snow or freezing rain (Sundstrom 1968a).

Snow accumulation determines the time and

extent of pronghorn movement. The deeper the

snow and more rapid the accumulation, the

further and faster herds travel toward lower

elevations, sometimes traveling as far as

144 kilometers (90 mi) (Mason 1952).

Soil

The best pronghorn habitats in the Great

Basin are found on Aridisols and Mollisols which

evolved under a regime of 25-38 centimeters

(lo-16 in) of precipitation per year.

Pronghorns require water throughout the

year. Springs, rivers, streams, lakes, reservoirs,

catchments, and troughs provide drinking water

much of the year; snow provides water during

winter.

Rangelands providing optimum habitat have

drinking water available at intervals less than

8 kilometers (5 mi) (Sundstrom 1968b). Some

animals may be found further than 8 kilometers

(5 mi) from water, but Sundstrom (1968b) observed that 95 percent of over 12,000 pronghorns

were within 4.8 to 6.4 kilometers (3 to 4 mi) of

water.

Water consumption by pronghorns varies inversely with the quality and succulence of available forage. When succulent forage is available,

1 liter (0.25 gal 1J.S.) of water per animal per day

is sufficient. When succulence exceeded 75 percent, animals did not drink (Beale and Smith

1970). During dry summers, 4.2-5.7 liters

(1.1-1.5 gal U.S.) per day may be needed (Beale

1966).

Drought can reduce the vitality and fertility of i

pronghorn (Hailey and others 1966, Jones 1949).

Pronghorns have killed themselves trying to get

through fences to reach water (Baker 1967).’

Water quality-particularly total dissolved

solids, alkalinity, and pH-is important for pronghorns. The maxi.mum total dissolved solids suitable for ungulate wildlife is 4,500 ppm (McKee

and Wolf 1963). Sundstrom (1971) found little

use of water with total dissolved solids in excess

of 5,000 ppm, and limited use of a source containing 4,620 ppm. Water with pH over 9.25 was not

used. Criteria for water quality suitable for

livestock and wildlife are given in the tabulation

below; the data are interim, however, and should

be used only until more precise data are available.”

Criteria

Total dissolved solids

Free chlorine

PH

Manganese

Alkalinity (as CaCo,)

Chlorides .mfcfiTu-fl--

Hardness

Maximum allo wed

“10 000 mg/liter

200 mg/liter

7.0-9.2

10 mg/liter

50 mg/liter

1 500 mg/liter ------5--gTRere

500 mg/liter i;~~,

BIOTIC FACTORS

Vegetation

Quality and quantity of vegetation are primary influences on pronghorn density. Sagebrush steppe preferred by pronghorns is characterized by Yoakum (1974):

1. Ground cover. Ground cover averages 50 percent living vegetation.

2. Composition. Vegetation averages 40-60 percent grasses, lo-30 percent forbs, and 5-20

percent shrubs.

I Baker, Ted C., Federal Aid Coordinator, Wyoming Game and Fish Commission, Cheyenne.

Personal communication: 1967.

2 U.S. Department of Agriculture, Forest Service,

Southwestern Region. Water quality interim guidelines. 1968. tinpublished report on file at USDA

Forest Service, Albuquerque, NM.

, 3 This figure is probably excessive.
iarietv. The number of plant species varies

rom 5 to 10 grasses, 20 to 40 forbs, and 5 to 10

hrubs.

;ucculence. Succulent plants are preferred

orage (Beale and Smith 1970), especially

luring spring and in some particularly moist

ummers (fig. 4). Pronghorns move from dry

upland ranges to intermittent lake beds and

blayas to graze succulent vegetation (Good

977). They also make disproportionate use of

ecently burned rangelands for foraging, esjecially in the first growing season after fire.

;uch areas often provide succulent grass

,prouts and an abundance of forbs (Beardahl

.nd Sylvester 1976, Stelfox and Vriend 1977).

b. Open rangelands supporting several

slant communities are preferred over monoypic vegetation (Sundstrom and others 1973,

loakum 1957).

Ieight. Low vegetative structure, averaging

18-61 centimeters (15-24 in) is best. Areas

vith vegetation taller than 61 centimeters

24 in) are used less; areas with vegetation

nore than 76 centimeters (30 in) tall are

,eldom used. Such tall vegetation restricts

he pronghorn’s ability to see and run-attributes which combine to form the animal’s

jrimary defense.

mal

ronghorns historically coexisted in various

ts of their extensive range with other ungus such as bison, elk (Cervus elafihus), mule

- (Odocoileus hemionus), and bighorn sheep

is canadensis) (Einarsen 1948, Nelson 1925,

.ara 1978, Yoakum 1978b). The bison, espely, grazed dominant grasses, restricting

xth of thegrass and enhancing production of

forbs and browse favored by pronghorns

ien 1972).

Coyotes (Canis latrans), bobcats (Lynx rufus),

1 golden eagles (Aquila chrysaetos) prey on

lnghorns, especially fawns (Beale and Smith

‘0, 1973; Compton 1958; Hinman 1961; Udy

13). Bobcat predation on young pronghorns

I depress populations on some ranges under

tain circumstances (Beale and Smith 1970,

‘3). Poor nutrition magnifies the impact of

dation (Beale and Smith 1970, Hailey and

ers 1966). Generally, where habitat is adeIte, predation is not a major limiting factor.

Figure 4.-An adult doe eating succulent forbs from a

community of grasses. (Photograph byJames Yoakum.)

Human disturbance can be particularly harmful on winter ranges and during fawning. Snowmobiles, motorcycles, and low flying aircraft

may cause adverse effects.

Habitat Characteristics

Preferred ranges have shrubs with a mean

height of 38 centimeters (15 in) (Yoakum 1974).

Low sagebrush (Artemisia arbuscula) dominates

commonly used summer ranges. The best winter

ranges are dominated by shadscale saltbush

(Atriplex confertifolia), black sagebrush (Artemisia nova), and winterfat (Ceratoides lanata).

Areas dominated by big sagebrush (Artemisia

tridentata) are less used, probably becauseof tall

growth of the plant. Alteration of big sagebrush

communities by fire or by plowing and chaining

to control shrubs increases their acceptance to

pronghorns (Yoakum 1978a).

Stands of exotic crested wheatgrass (Agropyron

desertorium and A. cristatum) which include

succulent forbs such as dryland alfalfa have

become accepted habitats when located near

occupied ranges and adequately supplied with
water (Heady and Bartolome 1977). When autumn growth of crested wheatgrass and forbs

occurs, and the snow cover which follows is

light, these rangelands are wintering habitat.

Management Relationships

The pronghorn population in Canada and the

United States increased 1,500 percent from 1924

to 1976 (Yoakum 1978b). Control of hunting and

large scale transplanting activities reestablished

herds on many historic ranges.

Rangeland management (including vegetation

alteration, fence construction, water development, and manipulation of livestock use) influences pronghorn habitat. Management planning

that considers pronghorn requirements can minimize adverse effects on pronghorn habitat; some

habitat improvement may result. If pronghorn’s

requirements are ignored, however, severe habitat damage can occur (Wagner 1978).

Nearly all rangelands inhabited by pronghorns

are also used by domestic livestock-primarily

cattle, sheep, and horses. Iitilization of forage in

1975 on the Bureau of Land Management’s Vale

district in southeastern Oregon is shown in the

tabulation below (Heady and Bartolome 1977).

Pronghorns consumed less than 1 percent of

forage, whereas domestic livestock consumed

83 percent:.

Domestic species Percent forage use

Cattle and horses 82.3

Sheep 0.7

Feral horses 5.8

Total

Wild species

Pronghorns

Mule deer

Bighorn sheep

Rocky Mountain elk

88.8

0.9

10.1

0.1

0.1

Total 11.2

Insufficient forage for current herbivore populationscreatescompetition for that which is available. Studies of food habits of horses, cattle,

domestic sheep, and pronghorns on sagebrush{

grasslands have shown that horses, cattle, and

sheep on sagebrush-grasslands have similar food

habits (Olsen and Hansen 1977). Pronghorns do

not compete with either horses or cattle when

forage and water are abundant. Competition

between domestic sheep and pronghorns, however, is more pronounced (Buechner 1950,

Hoover and others 1959, Severson and May

1967).

The effect of feral horses on pronghorn habitat

is largely conjecture. Meeker (1979) studied interactions between pronghorns and feral horses for

one summer in northeastern Nevada and observed no competition at watering sites or interspecific acts of aggression, but evidence of a

symbiotic relationship, and a dietary overlap of

12.8 percent.

There have been no analyses of the effects of

livestock grazing systems on pronghorns for the

Great Basin. Most rangelands in southeastern

Oregon no longer support yearlong livestock

grazing (Heady and Bartolome 1977). Grazing

systems are now based on seasonal needs of

livestock while satisfying the physiological requirements of the preferred plant species.

Pronghorns thrive best on ranges with sub- %“,

climax vegetative composition. These structural

and vegetal conditions are created by fire and by

the foraging of wild and domestic herbivores.

The variety of forbs, grasses, and shrubs is often

higher when the species composition and structural conditions of a plant community are typical

of midsuccession.

The quality of rangeland for pronghorns in

southeastern Oregon is described by combinations of habitat components identified in fig. 5.

An example of how to use the form for rating

pronghorn habitat as summer and winter range

is shown in fig. 6. Where optimum or near optimum vegetative conditions exist, it is best to

maintain the plant structure and composition”

(Yoakum 1980).

’ Kindschy, Robert R. The Vale project and wildlife

ecology. 1971. Unpublished report on file at the

I.J.S. Department of the interior, Bureau of Land

Management. District Office, Vale, OR.
WORK SHEET FOR RATING PRONGHORN HABITAT

(sagebrush steppe)

Step 1. Circle the m”st appropriate response in side A of each column (complete ~01s. 1-7 for rating summer range, cols. 2.4 and 6-7 for winter range).

Fill in at bottom correswnding percent of optimum from side B.

cd. I*

Availability of water

Distance

between

water I ” Percent (

kilometers optimun

(miles)

A

1 . 3.2 or less

(2 or less)

2 . 3.3-6.4

(2.1-4.0)

3 . 6.5.9.7

(4.1.6.0)

4 . 9.8.12.9

(6.1-8.0)

5 . 13.0.16.0

(8.1-10.0)

6 . 16.1+

(IO+)

Percent of

optimum

SCOWi:

-

Cal. 1

B

IW

8 5

-I Cd. 2 Cal. 3 Cd. 4 Cd. 5’ Cd. 6

Vegetative ground cover Vegetative height Vegetative succuIence FW??S

,f

1

4

:

6

Percent Percent < Percent Percent

shrubs optimun forbs optimur

A B

I . 5.20 100

2. 20.30 5 3

I . 30.40 2 7

1. 40.50 1 5

t . 50.70 5

I . 70+ 3

cot. 2 Cal. 3 Cd. 4 Cal. 5 Cal. 6 Cal. 7

A

1 . o-10

2 . IO.30

3 . 30-50

4 . 50.70

5 . 70-90

6 . 90.100

B

3 2

100

3 3

1 7

1 0

5

Height, in Percent of

centimeters optimum

(mches)

Forbs Percent

green optimum

A B A B

1. 25 or less 9 0 I . All summer 100

(10 or less)

2. 25.50 ToJuly 15 75

(10.20)

3. 50-76 ToJuly 1 5 0

(21.30)

4. 76.102 ToJune 15 25

(31.40)

5. 102.127 ToJun? 1 1 0

(41.50)

6. 127+ 0

(51+)

* f

Type

Percent ”

optimua

A B

NO% 100

:%-strand 9 0

barbed wtre

4-strand

barbed

8 0

wire

with 41+ cm

(16+ m.)

clearance

Woven.

81 cm or

less

(32 1”. or

less) high

Woven.

al+ cm

%ii”’

7 0

3 0

Step 2. Calculate habitat rating. Summer range: (a) Sum of the percents of optimum (step 2. cols. l-7)+7 = summer habitat rating.

(b) The column with the lowest percent of optimum shows the habltat component m”st limiting

the quality of pronghorn habitat. The lowest percent = primary habitat limiting factor.

Winter range: (a) Sum of the percents of optimum (step 2, cols. 2.4.6.7)+5 = winter habitat rating.

(b) The column with the lowest percent of optimum shows the habitat c”mpOnent most limiting

the quality of pronghorn habitat. The lowest percent = primary habttat limiting factor.

l Do not complete when rating winter range.

Figure 5.-Worksheet for rating pronghorn habitat

(sagebrush steppe).

cd. 7

Slope

Percent Percent of

grade “ptlmum

A B

1 . o-5 100

2 . 5.10 7 5

3 . 10.30 5 0

4. 30+ 2 5
WORK SHEET FOR RATING PRONGHORN HABITAT

(sagebrush steppe)

Step 1. Circle the most appropriate response in side A of each column (complete cols. 1.7 for rating summer range, co/s. 2-4 and 6.7 for winter range).

Fill in at bottom corresponding percent of optimum from side B.

Cd. 1 8

Avadabihty of water

DistaIXe

between

water I” Percent

kilometers opttmua

hles)

-

A B

I. 32or less 100

(2 or less)

2. 3.3-6.4 85

12.1-4 0)

3 6.5.9 7 57

(4.1.60)

4. 

0

a12.9 30

(6.1-E 0)

5. 13 0.16.0 12

(8 I-10.0)

6 l&l+ 0

(IO’)

-.-

Percenl of

Cd. I

-I Cd. 2 Cd. 3

Vegetativeground cover

Percent Percent (If Percent Percent

shrubs optimun1 forhs optmlur

A B

1 . 5.20 100

3 30.40 27

4 40.50 IS

5. 50.70 5

6 70+ 3

53

-~__

Cal. 2

A 0

I. O-IO 3 2

?

Cl

10.30 100

I 30-50 33

1 50.70 17

7090 IO

90-100 5

100

.~ ----

Cal 3

cd. 4

Vegetative haght

-

Herght, in Percent

cenwneters optimu

(mches)

A B

1 . 25 or less 9 0

(IO or less)

2 25.50 100

(10.20)

3 

0

O-76 50

(21.30)

1 . 76.102

(31 40)

i 102.127

(41.50)

i 127+

(51+)

10

5

0

*

50

Cd 4

of

m

-

I.

2.

3.

4 .

5

Cd. 5’

~~

Vegetative succulenct

Forbs P.%i?flt

green optlm”’

A B A B

All summer 100 None 100

ToJuly 15 75

50

ToJune 15

To June J

25

10

_.

l

50

-

__.--

Cd 5

Cd. 6

FenCeS

Type

Percent 0

optimum

‘. 3-strand 90

barbed wire

80

81 cm or

less

(32 ,n. or

less) high

80

Cal. 6

f

-

4

2

3

4

Cd. 7

-.

SlOpe

Percent Percent of

grade optimum

A B

a

O-S 100

5.10 75

IO-30 50

30+ 25

IO0

Cal. 7

Step 2. Calculate hablrat rarrng Summer ranger (a) Sum of the percents of @unum(st~p2, ~01s. l-7)+7 = swmner habitat ratmg.

(b) The column wth the lowest wrcent of optimum shows the habitat component most bmlting

the quality of pronghorn habltat. The lowest percent = primary habltatlimiting factor.

Winter range: (a) Sum of the percents of optmum (step 2, cols. 2 4.6.7)S5 = winter habitat rating.

(b) The column wth the lowest percent of optimum shows the habitat component most limiting

the quality of pronghorn habitat. The lowest percent = primary habitat limiting factor.

. Do not complete when ratingwmter range.

Figure G.---Example of completed worksheet.

8
?angeland Manipulation VEGETATIVE CHANGES

)ulating vegetation to increase livestock

; intensifying in some areas of the Great

\n associated activity is modifying the

:o enhance livestock management and to

more complete rangeland use; fencing

er developments (fig. 7) are examples.

Manipulating vegetation can be either beneficial or detrimental to pronghorns, depending

on how it is accomplished (Yoakum 1978b, also

see footnote 4). Two basic precautions must be

taken: other habitat requirements of pronghorns

must be met, and all work should follow the

.-Construction of ear-t hern reservoirs proiter for pronghorns in water deficient rangesoutheastern Oregon. (Photograph by James
principles of range restoration described by Plummer and others (1968):

1 .

2 .

3 .

4 .

5 .

6 .

7 .

8 .

9 .

10.

Changes in plant cover must be justified as

biologically desirable.

Terrain and soils must be suited to

the changes.

Precipitation must be adequate to assure

establishment and survival of seeded plants

(Bleak and others 1965).

Competition should not prevent establishment of desired species.

Only species and strains of adapted plants

should be seeded.

Mixtures, rather than single species, should

be planted.

Sufficiently pure and viable seeds should be

planted to increase the probability of success.

Seed should be sufficiently covered to enhance sprouting (Basile and Holmgren 1957,

Plummer 1943).

Planting should be done in the correct season

to ensure establishment.

The planted area should be adequately protected from livestock, insects, fire, off-road

vehicles, etc.

Extensive areas dominated by big sagebrush

(where big sagebrush comprises more than 30

percent of the vegetative cover) are marginal

pronghorn habitat, especially if the shrubs are

taller than 76 centimeters (30 in). Such areas can

be treated to decrease the density and height of

sagebrush (fig. 8) (Yoakum and others 1980).

Figure 8.-Results of manipulating vegetation b

plowing and seeding: A, vegetation before treatmer:

(photographed July 1963); B, after seeding (photc

graphed June 1969). The vegetative structure show

in B is more favorable to pronghorns. (Photographs b

Robert Kindschy.)

10
If an area is to be treated, it should probably be

no larger than 405 hectares (1,000 acres). The

size is based on the assumption that (1) the

winter range of pronghorn herds residing in the

Great Basin averages 1 215 to 3 025 hectares

(3,000 to 5,000 acres) and (2) the treated area

should encompass no more than one-third of this

winter range. About 5- to 20-percent shrub cover

should be retained in the treated area. Because

sagebrush and native forbs are important food

items (Beale and Smith 1970, Mason 1952, Salwasser 1980, Yoakum 1980), the majority of the

natural vegetative communities needed for seasonal use, primarily sagebrush-grasslands,

should be retained.

Shrubs are often controlled by mechanical

means. Plowing and seeding has been done in

many areas of the Great Basin. A brushland

plow is often used (fig. 9); this is a disk-type plow

developed especially for this purpose. Chaining

is another technique widely used. A heavy link

ship anchor chain is dragged between two

crawler tractors. Chaining does not kill many

nonwoody plants or the younger, more flexible

shrubs.

Aerial application of herbicide has been a

common practice for sagebrush control (Heady

and Bartolome 1977). Some applications of 2,4-D

have killed nearly all shrubs and perennial forbs.

This treatment results in standing dead shrubs

that retain their tall structure. Pronghorns

usually avoid areas containing such structures

for several years (fig. 10).

Historically, fire has been an important influence on the structure of plant communities. Controlled or prescribed fire can control shrubs and

is used, on a small scale, as a technique for

enhancing habitat. Prescribed burning, properly

done, can decrease sagebrush density and enhance opportunities for native grasses and forbs

(Beardahl and Sylvester 1976, Lovaas 1976, Page

1975). Fire triggers a series of secondary responses, many of which enhance the habitat for

pronghorns. Soil fertility is usually increased.

With the canopy removed, soils are warmed by

solar heating, promoting earlier vegetative

growth in the spring. Plant vigor is increased by

removal of senescent shoots and foliage. More

forage may become available because some plants

become more palatable after burning. Long-term

Figure Y.-A brushland plow converts dominated

shrublands to communities with comparatively low

structure. (Photograph by Robert Kindschy.)

Figure IO.-Big sagebrush killed by chemical application. The skeletons of the sagebrush persist for years

and create an unfavorable habitat for pronghorns.

(Photograph by Robert Kindschy.)

11
increases in vegetative growth may be stimulated by timing the burn to favor species with

highest yields, by removing competing plants,

and by preparing seedbeds for vegetative pro

duction.

If a site treated for shrub control has insufficient plants to ensure reproduction, it can be

artificially seeded. Such ventures have usually

resulted in monocultures of exotic grasses, however, which have limited value to pronghorns

other than reducing the height and number of

shrubs. Conversely, seeding mixtures have been

beneficial to pronghorns, especially when legumes such as dryland alfalfa were included”

(fig. 11). A useful rule of thumb is to include

a minimum of six palatable species each of grasses,

forbs, and shrubs (Plummer and others 1968).

s Kindschy, Robert R. Preliminary report on nomad

alfalfa seedings. 1974. Unpublished report on file

at the U.S. Department of the Interior, Bureau of

Land Management, District Office, Vale, OR.

Pronghorns have used some areas seeded with

crested wheatgrass (see footnote 4). Winter use

occurs where autumn growth is stimulated by

fall rains. Fecal analysis showed that cheatgrass

(Bromus tectorum), sagebrush, and scarlet globemallow (Sphaeralcea sp.) dominated the diet of

pronghorns wintering on such areas, crested

wheatgrass represented approximately 2 percent.”

WATER DEVELOPMENT

Pronghorns drink from many sources of water,

including springs, creeks, rivers, lakes and reservoirs, stock water developments, troughs, and

devices for catching precipitation or “guzzlers.”

Numerous small reservoirs have been constructed in southeastern Oregon to trap and

store precipitation for use by livestock and

ungulate wildlife (see fig. 7). Many of these have

been constructed on public lands through cooperative funding by State wildlife organizations and

Federal land management agencies. In Malheur

County, Oregon, 1,037 such reservoirs have been

built (Heady and Bartolome 1977).

Another water development valuable to pronghorns is the charco pit or dugout (fig. 12). These

earthen pits entrap and store precipitation primarily for livestock and wildlife, but they are

readily used by pronghorns, especially during

hot late summer months when vegetation is

desiccated, and the animals’ requirement for

water increases.

Wildlife use water from natural springs and

seeps. These sources of water are often developed for other uses, such as for livestock, fire

suppression, and humans. With minor modifications, such as placing troughs low on theground,

these developments can benefit pronghorns

(fig. 13).

Guzzlers can provide water on ranges otherwise lacking in potential sources (June and Higby

1965, Sundstrom 1968b, U.S. Department of the

Interior, Bureau of Land Management 1964).

Figure I I.-Using mixtures of forbs and grasses

greatly enhances seeded areas as pronghorn habitat.

Nomad variety alfalfa and crested wheatgrass were

planted in this seeding. (Photograph by Robert Kindschy.)

6 Spalinger, Don. Notes on the food habits of

pronghorn antelope on the Rome seeding, Oregon,

during late winter, 1977, with special reference to

crested wheatgrass use. 1979. Unpublished report

on file at the U.S. Department of the Interior,

Bureau of Land Management, Reno, NV

1 2
DESILTING AREA

Y

eelz.-c~arcoPit. (Adapted from Y’akum 1980.)

L
They require little maintenance, are relatively

inexpensive, and serve a variety of wildlife. A

three-strand barbed wire fence 81 centimeters

(32 in) high with a smooth bottom wire at least

41 centimeters (16 in) above the ground can be

constructed to exclude cattle and horses. Such

construction still allows pronghorns to use the

water, but restricts livestock.

LIVESTOCK FENCING

Fences can restrict the movement of pronghorns, causing changes in herd distribution,

deaths, and losses in carrying capacity due to

isolation of ranges (Bruns 1977, Hailey and

others 1966, Martinka 1967, Oakley 1973, SundStrom 1970).

The following specifications, resulting from

intensive studies, are recommended for fence

construction in areas used by pronghorns (Mapston 1972; Spillet and others 1967; U.S. Department of the Interior, Bureau of Land Management 1974,1975; Zobelll968):

The use of woven or net-wire fences should be

minimized.

Areas encircled by the types of fences that

hinder pronghorn movement should be large

enough to include their yearlong habitat

needs.

Pathways and migration routes of pronghorns should have low fences, lay-down

panels, pass structures, or adjustable spacing

of the wire (Yoakum 1980).

4. Barbed wire fences with no more than three,<

strands can be negotiated by pronghorns. The{

bottom wire should be smooth (no barbs) and

be at least 41 centimeters (16 in) above the

ground. Remaining wires shoud be spaced at

25-centimeter (lo-inch) intervals. The total

height of the fence should not exceed 91 centimeters (36 in), and there should be no stays

between posts (fig. 14).

New fences should have white rag flagging

tied to the top wire between each post. Pronghorns will, to some extent, adapt to the fence by

the time the flagging deteriorates.

Although pronghorns normally pass under or

through fences, some learn to jump fences up to

81 centimeters (32 in) high. Woven wire fences

are sometimes considered necessary to control

domestic sheep. Of the designs tested, the least

detrimental to pronghorn passage were (1) a

span of net or woven wire 81 centimeters (32 in)

high without single strand(s) of wire above, or (2)

a span 66 centimeters (26 in) high with one

barbed wire 10 centimeters (4 in) above the net

wire (Spillet 1965).

Management Tips c

Where pronghorns are selected as a featured\*

species for management and their welfare is an

objective of management, the limiting factor(s)

for each range should be identified and appropriately altered if habitat is to be improved (see figs.

4 and 5). Following are suggestions, including

guidelines from the 1978 pronghorn antelope

workshop (Autenrieth 1978):

Figure 14.~Specifications for livestock fences constructed of barbed wire on pronghorn ranges (U.S.

Department of the Interior, Bureau of Land Management 1975).
HABITAT

1. Where precipitation is less than 15 centileters (6 in) per year, the vegetation should not

e manipulated.

2. The best ranges have at least 50-percent

round cover and the vegetative structure is no

aller than 38-61 centimeters (15-N in).

3. A vegetative composition that averages

O-60 percent grasses, lo-30 percent forbs, and

-20 percent shrubs is best.

4. High diversity in vegetation is preferable:

-10 grass species, 20-40 forb species, and 5-10

hrubs.

5. Where plants are seeded, it is important to

elect species that will ensure succulence into

ate summer. Dryland alfalfa is an example.

daintenance, improvement, or creation of wet

meadows is likewise important.

6. Livestock grazing systems designed to en-

.n-e sufficient seasonal forage can also benefit

ronghorn. For example, the number of livestock

n spring pronghorn ranges can be adjusted to

ssure growth of vernal forbs, and sheep can be

?stricted from pronghorn fawning areas for

5 days before and after the peak fawning season

vlay 15 to June 15). Adequate forage on winter

anges is particularly important; inadequate

Irage frequently limits the size of pronghorn

erds.

7. Pronghorns require 0.9 kilogram (2 lbs) of

ir-dried, preferred forage per animal per day

ieverson and others 1968). This should be

onsciously provided through management.

IIATER

1. Water sourceson pronghorn summer ranges

re most beneficial when no more than 4.8 kiloleters (3 mi) apart and when they are designed

nd managed for pronghorns, even when livetockaremovedtootherpastures.Inaddition,on

vestock summer ranges that serve as critical

‘ronghorn winter ranges, some water sources

an be restricted from livestock use. The restricion can help prevent overuse of surrounding

egetation by livestock.

2. Availability of water is particularly important on summer ranges from June through

October, when each adult pronghorn requires

1 .O liter (l/4 gal U.S.) per day.

3. Water is most palatable to pronghorn when

the pH is less than 9.25 and the total dissolved

solids are less then 5,000 ppm.

FENCING

1. Pronghorns fare best when fences for controlling livestock movement have no woven wire

and are built in such a way to allow pronghorns to

pass.

2. Barbed wire fences with smooth bottom

wires at least 41-46 centimeters (16-18 in) above

the ground, no stays, and a top wire no higher

than 81 centimeters (32 in) allow pronghorns to

pass.

3. White-topped steel fenceposts will increase

the visibility of the fence.

4. White cloth strips tied to the top wire

betweenpostsofanewfencewillalsoincreasethe

visibility of thefenceand willallow pronghorns to

become used to its location.

5. Lay-down panels or “antelope passes” can

be constructed at strategic points to allow pronghorns to move between areas. In addition, gates

can be left open when livestock are removed from

fenced pastures.

HARASSMENT

Humanactivitiesdisturbpronghorns.Controlling the use of motor vehicles, particularly offroad vehicles, on summer ranges during fawning

season (May 15 to June 15) and on winter ranges

when herds are concentrated (December 1 to

March 15) will minimize disturbance.

GRAZING

Domesticsheeparegenerallymorecompetitive

with pronghorns for preferred forage than are

cattle and horses. In addition, the net wire fences

commonly used to contain sheep often limit the

movement of pronghorns. Pronghorns usually

fare better when grazing with horses and cattle

than when grazing with sheep.
Summary

The old adage that “good” range management

is “good” for wildlife was probably never true

and is no longer acceptable (Thomas 1979)

certainly not for pronghorns. Improvements in

pronghorn habitat, to date, have largely been a

byproduct of management activities to improve

conditions for livestock. But pressure for increased livestock production is accompanied by a

growing public concern for wildlife. Pronghorns

can benefit from range management activities

only if their welfare is planned in advance and

their habitat requirements are no longer left to

chance.

Acknowledgments

Wildlife biologists Cecil Langdon and Ellis

Mason, Oregon Department of Fish and Wildlife,

served as consultants.

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16
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c
WILDLIFE HABITATS IN MANAGED RANGELANDS -THE

GREAT BASIN OF SOUTHEASTERN OREGON

Technical Editors

JACK WARD THOMAS, U.S. Department of Agriculture,

Forest Service

CHRIS MASER, U.S. Department of the Interior,

Bureau of Land Management

Title

Introduction

Plant Communities and Their

Importance to Wildlife

The Relationship of Terrestrial

Vertebrates to the Plant Communities

Native Trout

Ferruginous Hawk

Sage Grouse

Pronghorn

Mule Deer

Bighorn Sheep

Riparia;l Zones

Edges

Geomorphic and Edaphic Habitats

Manmade Habitats

Management Pratt ices and Opt ions

Now available

Gen. Tech. Rep. PNW-120

Gen. Tech. Rep. PNW-84

Gen. Tech. Rep. PNW-145

Gen. Tech. Rep. PNW-139

Gen. Tech. Rep. PNW-80

Gen. Tech. Rep. PNW-85

Gen. Tech. Rep. PNW-99

Gen. Tech. Rep. PNW-86
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Agriculture is dedicated to the principle of multiple

use management of the Nation’s forest resources

for sustained yields of wood, water, forage, wildlife,

and recreation. Through forestry research,

cooperation with the States and private forest

owners, and management of the National Forests

and National Grasslands, it strives - as directed by

Congress - to provide increasingly greater service

to a growing Nation.

The U.S. Department of Agriculture is an Equal

Opportunity Employer. Applicants for all Department

programs will be given equal consideration without

regard to age, race, color, sex, religion, or national

origin.

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