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ECOLOGY OF MOOSE . • .. 1n
F ~MONT COUNTY, IDAH() .. ""
by
Brent W. Ritchit. Senior Game Research
WILDLIFE BULLETIN NO.7-1
Idaho pa ~nt of Fish and ...., ... ,,_
53'f
ECOLOGY OF MOOSE
• ID
FREMONT COUNTY, IDAHO
by
Brent W. Ritchie
Senior Game Research Biologist*
, -
1978
WILDLIFE BULLETIN NO. 7
IDAHO DEPARTMENT OF FISH AND GAME
600 South Walnut -P.O. Box 25 -Boise, Idaho 83707
Joseph C. Greenley, Director
FINAL REPORT
FEDERAL AID PROJECTS W-143-R and W-160-R, Moose Ecology Subproject
*Currently Senior Conservation Officer. Teton. 83451.
ACKNOWLEDGMENTS
I appreciate the help of numerous individuals throughout
this project. I am particularly indebted to personnel of Idaho
Department of Fish and Game and Targhee National Forest
for assistance with field work. Lynn Merrill, David Billman
and Mark Kliewer helped collect and tabulate data. Tom
Leege, Carl Nellis and Lloyd Oldenburg of the Department of
Fish and Game and Dr. Jim Peek, University of Idaho,
reviewed the manuscript and suggested improvements. Jody
Taylor, Wildlife Bureau secretary did the layout and proofing
and assembled figures.
II
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS .......................................................................... iii
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
HISTORY AND PRESENT DISTRIBUTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..................... .
STUDY AREA LOCATION AND DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..................... .
Junipers Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..................... .
Big Bend Ridge .................................................................................. .
Fall River Ridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Island Park . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Shotgun Valley ................................................................................... 2
METHODS ........................................................................................ 2
POPULATIONDYNAMICSANDMOVEMENTS ..................................................... 7
Population Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Sex and Age Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Age Structure of Harvest ........................................................................... 7
Mortality Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Hunting ....................................................................................... 9
Malnutrition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Accidents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Parasites and Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Predation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Climatic Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Present Population Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Seasonal Movements ............................................................................. 13
Fall River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Junipers-Big Bend Ridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Island Park . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Shotgun Valley ................................................................................ 15
Home Ranges ................................................................................... 15
Summer Home Ranges .......................................................................... 15
Winter Home Ranges ........................................................................... 15
Timing of Migration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
HABITAT RELATIONSHIPS ...................................................................... 17
Food Habits ..................................................................................... 17
Summer and Fall ............................................................................... 17
Winter ....................................................................................... 17
Browse Utilization and Condition Trend ............................................................. 18
Fall River . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Junipers-Big Bend Ridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Island Park and Shotgun Valley ................................................................... 21
Seasonal Use ofVegatation Types ................................................................... 23
Winter Use of Cardinal Aspects-Warm River Butte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Use of Clearcuts vs. Mature Stands-Fall River Ridge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Use of Grazed vs. U ngrazed Willow Habitat-Henry's Lake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
MANAGEMENT RECOMMENDATIONS ........................................................... 29
SUMMARY ...................................................................................... 30
LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
iii
TABLES AND FIGURES
Figure I (Distribution of Moose-Study Area) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Figure 2 (Map of Study Area). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Figure 3 (Trend Counts-Fremont County and Shotgun Valley) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 4 (Trend Counts-Big Bend Ridge and Junipers Ranges) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 5 (Trend Counts-Fall River Ridge and Island Park Ranges) ......................................... 6
Table I (Herd Composition Counts-Fremont County) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Table 2 (Age Composition of Hunter-Killed Moose-Fremont County) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 3 (Mortality Recorded on Study Area) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Table 4 (Summary of Moose Tagged in Fremont County) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Figure 6 (Winter Severity Index-Island Park Dam and Fremont County) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . II
Figure 7 (Summer Sighting for Moose Tagged-Fall River and Island Park Ranges) . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 8 (Summer Sightings for Moose Tagged -Junipers and Big Bend Ridge Winter Ranges) . . . . . . . . . . . . . . . . . 14
Figure 9 (Summer Home Ranges of 4 Radioed Moose-Fremont County) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Table 5 (Forages Eaten by Moose During Summer and Fall-Fremont County) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Table 6 (Forages Eaten by Moose During Winter-5 Fremont County Ranges) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Table 7 (Important Forage Species in Mature Forest Stands-Fall River Winter Range) . . . . . . . . . . . . . . . . . . . . . . . 20
Table 8 (Important Forage Species-Fall River Ridge Clearcuts) .......................................... 21
Table 9(Important Forage Species-Junipers Winter Range) ............................................. 21
Figure 10 (Winter Photo-Fall River Clearcuts) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 10 (Important Forage Species-Big Bend Ridge Winter Range). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Table 11 (Important Forage Species-Island Park Winter Range) .......................................... 23
Figure II (Seasonal Use of Vegetation Types-3 Fremont County Ranges) .................................. 24
Figure I2 (Photo, East Aspect-Warm River Butte) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Table I2 (Vegetal Characteristics-Warm River Butte and Fall River Range) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Table 13 (Vegetal Characteristics-Fall River Ridge) .................................................... 27
Figure I3 (Snow Depths-Warm River Butte and Fall River Ridge) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Figure I4 (Photo, Willow Habitat-Howard Creek) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Appendix Table I (Scientific Names of Plants in this Report). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Appendix Table 2 (Forage Species not Shown in Tables 5 and 6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
PHOTO CREDITS:
Front Cover ....................... Mark Kliewer
Back Cover. . . . . . . . . . . . . . . . . . . . . . . . Brent Ritchie
iv
INTRODUCTION
This report summarizes the findings from an
ecological study of Shiras moose (A/ces a/ces shirasi)
conducted in Fremont County, Idaho, from July 1969 to
December 1976. Prior information on moose movements
obtained by Nielson and Shaw (1967a, 1967b) and
population trend counts by Department of Fish and
Game personnel is included.
Trend counts made from 1949 to 1969 indicated that
populations on three of the five winter ranges in the
county had declined since the mid-1950's. This study was
conducted to identify causes of the decline and to develop
management guidelines. Seasonal movements and
aspects of winter ecology were emphasized in this study.
HISTORY AND PRESENT DISTRIBUTION
Moose may not have existed in Idaho during the
early 1800's. The earliest reference I found which may
have alluded to moose was from the Lewis and Clark
Journals in 1806. When the Lewis and Clark party was in
what is now northcentral Idaho, the Indians informed
them that there were" ... plenty of moos to the S.E. of
them on the East branch [Salmon River] of Lewis's
[Snake] river. .. " (Thwaites 1959; Vol. 5:99). It is
unclear, however, whether the "moos" and "moos deer"
recorded in the Lewis and Clark journals were moose or
other members of the deer family. Bailey ( 1935: 136) gives
the following account: "At the time of the Thunder
Mountain rush [ 1902] there were yet in the Salmon River
watershed numbers of moose. They had never been
plentiful. . . but there was a small band of these animals
which made its headquarters in Chamberlain basin."
Moose were evidently present in the upper Salmon River
drainage before 1900.
There is no evidence that moose were found in
southeastern Idaho prior to 1850. Many fur trappers,
including Osborne Russell (Haines 1955), Angus Ferris
(Auerbach 1940), Alexander Ross (Spaulding 1956),
Washington Irving (1887), Donald Mackenzie (Clements
1969), and Peter Skene Ogden (Rich 1950) traversed the
region extensively prior to 1850. They frequently noted
other big game species in their journals, but never moose.
I assume that since they were not mentioned, moose were
not seen. Houston (1968) concluded there were few, if
any, moose in the Yellowstone and Jackson Hole areas of
Wyoming prior to 1850. Moose in Montana (Curtright
1969:439, Koch 1941, Spaulding 1956:291, Stewart and
Stewart 1957:lll, Schladweiler 1974:2-4) may have
furnished the stock that dispersed into Idaho and
Wyoming during the mid-1800's.
The Hayden party collected three moose in Teton
Canyon near the Idaho-Wyoming line in July 1872
(Hayden 1873:668). Moose may have been plentiful in
southeastern Idaho by the 1890's, since hunting seasons
were established from 1893 to 1898. The season was
closed in 1899 and remained so for the next 46 years
(Nielson & Shaw l967a: I). Moose hunts were established
again in 1946 and a limited number of permits have been
issued annually since. An average of 125 permits per year
were issued statewide during the study period. In 1949,
536 moose were observed during an aerial census of the
study area and the statewide population was estimated at
1,000 (Hatter 1949:500). Present distribution of moose in
Idaho is shown in Fig. I.
STUDY AREA LOCATION AND
DESCRIPTION
The study was conducted in Fremont County in the
northeast corner of southern Idaho (Fig. 1). The climate
on the 2,000 sq. mi. (5, 180 km 2) study area is cool
temperate, with long winters and deep snow. Elevations
range from 5,000 to 10,000 ft. (1,520 to 3,050 m). Annual
precipitation at Ashton, elevation 5,220 ft. (I ,590 m), was
16.9 in. (43 em). Monthly mean temperatures for January
and July were 18° and 64° F (-8° and 18° C), respectively.
Moose wintered on five distinct areas; the Junipers,
Big Bend Ridge, Fall River Ridge, Island Park and
Shotgun Valley ranges (Fig. 2). These wintering groups
or herds represented four discrete populations which
intermingled during summer but returned to their
respective winter ranges each year. The Junipers and Big
Bend herds overlapped during both summer and winter
and were therefore considered as one population.
Junipers Range
The Junipers range, about 150 sq. mi. (390 km2) is a
complex of both stabilized and raw sand dunes in the
southwestern corner of the study area. It lies on the Snake
River Plain at 5, I 00 ft. (I ,550 m) elevation and is 20 miles
(32 km) from the nearest forested area. The name is
derived from several volcanic buttes which rise several
hundred feet above the surrounding plain and are
covered with Rocky Mountain junipers*. This area, like
most of southern Fremont County, is underlain with
basaltic lava flows. Soils are shallow with numerous lava
outcrops where not covered with sand dunes.
The Junipers range is nearly 100 percent sagebrush-
grass habitat type. Big sagebrush, bitterbrush,
rabbitbrush and chokecherry are the dominant shrubs.
Snow depths seldom exceeded 2 ft. (60 em) during the
study. The range supported greater numbers of mule deer
( Odocoileus hernia nus) and elk ( Cervus e/aphus nelsoni)
during the winter than moose. The area was described in
detail by Chadwick and Dalke (1965) and Wing (1962).
Big Bend Ridge
Big Bend Ridge occupies 80 sq. mi. (210 km2) near
the center of the study area. It has extensive south-facing
slopes that terminate on the Snake River Plain at 5,300 ft.
(1,620 m.) elevation. Highest elevation of the Ridge is
approximately 7,000 ft. (2,135 m.). About 90 percent (68
sq. mi.) was used by moose as winter range. The major
vegetation types and percentage of area occupied by each
*Scientific names of plants listed in the text are in Appendix Table I.
Page 1
Page2
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Figure 1 . Present distribution of moose in Idaho.
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JUNIPERS
RANGE
Figure 2. Map of the Study Area
'•
RANGE
FALL
RIVER
RANGE
YELLOWSTONE
NATIONAL
PARK
• w •••
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ol g'
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. . . . . . . . . . . . . . . • .
Page 3
are: Douglas fir, 27; aspen, 26, brush, 24; lodgepole pine,
20; and meadow and willow, 2. Common shrubs include
big sagebrush, bitterbrush, chokecherry, serviceberry,
upland willow, riparian willow, snowbrush, snowberry
and mountain maple. Dense stands of Bigtooth maple, a
species unique to this range, occupied 8 sq. mi. (21 km2 )
of Douglas fir-brush habitat on the lower slopes near the
center of the range. Snow depths usually ranged from 2.5
to 3 ft. (76-91 em) at the base to 6 ft. (183 em) at the top
which prevented deer and all but a few elk from wintering
there. Moose from the Junipers move across Big Bend
Ridge going to and from summer range and some of them
winter on the Ridge in mild winters.
Fall River Ridge
The Fall River range is located in the southeast part
of the study area. It covers 175 sq. mi. (450 km2) in the
lower Fall River and Warm River drainages, of which 63
percent (110 sq. mi.) is critical winter range. The terrain
consists mostly of rolling hills at elevations of 5,500 to
7,000 ft. (1,680-2, 130m). The major vegetation types and
percent of the total area occupied by each are: lodgepole
pine, 52; Douglas fir, 15; aspen, II; brush, I 0; open areas,
10; and willow meadow and aquatic, 2. About 10 percent
of this range has been clearcut logged since 1960.
Clearcuts have regenerated to pinegrass and lodgepole
pine at higher elevations, and to aspen, upland willow,
forbs, and lodgepole pine at lower elevations. The
understory in lodgepole pine stands is typically pinegrass
and huckleberry. Upland willow, chokecherry,
serviceberry, rose, snowbrush, snowberry and a variety
of forbs are present in the Douglas fir and aspen types.
Snow depths on the lower parts of this range exceeded 3.5
ft. (107 em) for at least four weeks during six of the eight
winters.
Island Park
Island Park is a large volcanic caldera in northern
Fremont County. It is an elliptical basin 18 by 23 miles
(29x37 km) in size and has been filled with rhyolite, ash
and basalt flows from the Yellowstone area (Williams
and Lindsay 1968: 163). The basin floor lies at 6,000 to
6,500 ft. ( 1,830-1,980 m) elevation and is rimmed on the
north by the peaks of the Continental Divide rising to
10,000 ft. (3,050 m), and on the south by Big Bend Ridge.
About 80 percent of the area is occupied by a lodgepole
pine forest. Riparian willow flats and streams occupy less
than 3 percent of the area but support most of this moose
population during winter months. The area is also a
popular summer home resort area which receives high
recreational use year around. Snow depths here are
similar to those at the upper elevations of the Big Bend
and Fall River ranges.
Shotgun Valley
The Shotgun Valley range consists of the south
slopes of the Centennial Mountains from McCrea's
Bridge in Island Park to West Dry Creek. It covers 70 sq.
Page 4
mi. (180 km2) at 6,300 to 9,300 ft. (1,920-2,835 m)
elevation. Percentage of the range occupied by the
various vegetation types are Douglas fir, 54; sage-grass,
19; spruce-fir, 12; lodgepole pine, 8; mountain brush, 5;
and willow, less than I. The spruce-fir type is favored by
moose during the winter. Like Island Park, Shotgun
Valley is an area of high snowfall.
METHODS
Moose sightings were obtained from vehicle,
snowmachine and fixed-wing aircraft. Aerial herd
composition counts were made prior to antler drop
whenever snow cover was adequate. Trend counts were
made during good snow cover conditions in mid-winter.
Use of vegetation types was determined by direct
observation.
Reports of moose mortality were obtained from a
variety of sources, but primarily from Department of
Fish and Game and U.S. Forest Service personnel.
Carcasses were examined whenever possible to determine
cause of death and mandibles were collected to determine
age. Those from calves and yearlings were classified
according to the tooth replacement criteria of Passmore
et al. ( 1955), and adults were aged from cementum annuli
counts in sectioned incisors (Sergeant and Pimlott 1959).
Se1sonal movements were determined from summer
sightings of moose tagged on winter ranges. Five moose
were radio-tracked to more precisely determine
movements and habitat use. Moose were captured using
snowmobiles. Adults were immobilized with
succinylcholine chloride drug (Anectine) administered by
dart gun, and calves were "dogged" using the techniques
reported by Ritchie and Barney ( 1973). The average
dosage for adults was 20 mg ±2 mg for size extremes
when the drug was used in solution, and 2 mg less when
the powdered form was delivered by factory-loaded
Pneu-darts. Adults were marked for individual
identification with 4-inch-wide vinyl-covered neck bands,
color-coded for each tagging area, and bearing painted
numbers. Calves were marked with numbered, pendant-
type ear markers.
Rumen analysis (Cole 1956:20) and feeding site
examinations (Knowlton 1969: 163) provided
information on food habits. Rumen samples were
obtained from moose killed by hunters and accidents.
Live moose were tracked between bed sites and one
instance of use was recorded for each stem browsed.
Percentages were computed and the data compiled by the
aggregate percentage method of Martin et al. ( 1946).
Browse utilization and condition trend were
estimated by the Cole (1963) method. Permanently-
marked transects were examined soon after snow melting
commenced so that available plants could be
distinguished from those which had been unavailable
under the snow. Cover types used by moose were
determined from ground and aerial observations. Pellet
group counts were made on paired .01 acre (40m2) plots.
-------FREMONT COUNTY (Total Study Area)
500
N u 400
M
B
E
R
300
0
B s
E
R v 200 E
D
100
-------SHOTGUN VALLEY RANGE
~
/ ' -· - -..._,.-.........._ -•• • • .IJo c
• • O(JIJt
50 53 56 59 62
YEAR
...... ~ .... . . • • •
65 68
····----
71 74
Figure 3. Results of moose trend counts for all Fremont County ranges combined and in
Shotgun Valley. 1949 to 1975 (3-year averages).
Page5
Page 6
N
u
M 20
B
E
R
0
B s
E
R v
E
D
.,....__-
.................. -------.-...........
50 53 56 59
'
62
YEAR
65
BIG BEND RIDGE
JUNIPERS
68 71 74
Figure 4. Results of moose trend counts on Big Bend Ridge and Junipers ranges, 1949 to
1975 (3-year averages).
N u
M
150
B
E
R
0
B
75
s
E
R
v
E
D 50 53 56 59
-------FALL RIVER
62
YEAR
---ISLAND PARK
65 68 71 74
Figure 5. Results of moose trend counts on Fall River Ridge and Island Park ranges.
1949 to 1975 (3-year averages).
A 100-foot tape was strung full length and the observer
walked each side recording groups within 4.356 ft. of the
tape. Groups lying 50 percent or more outside the plot
were excluded. The method was rapid and adaptable to
the various terrain and cover conditions encountered.
Pellet groups of the current winter were distinguishable
because older groups were at least partially covered by
litter.
Vegetal composition was measured quantitatively
on several sites important to moose. Line intercept
measurements (Canfield 1942) were used to determine
canopy coverage of shrubs 4 to 12 ft. (122-366 em) tall
(winter availability zone); canopy coverage of vegetation
below 4 ft. (122 em) was measured by the Daubenmire
(1959) method. Crown cover of trees over 3 in. (7 .6 em)
dbh was determined in the manner described by Jackson
and Petty ( 1973), except that a hand level with right angle
prism was modified to project canopy crowns to the tape
instead of using a periscope prism. Tree density was
determined by the point-centered-quarter method
(Cottam and Curtis 1956). Plant nomenclature follows
Davis (1952). Statistical procedures (chi-square and t-
test) followed Steel and Torrie (1960). Tests for
significance were made at the 5 percent probability level
unless otherwise stated.
A winter severity index was computed to compare
winter conditions during the study with previous years
using weather data from Island Park Dam, elevation
6,300 ft. (1,921 m). The index was calculated for the
period November I to April 30 in the following manner:
The monthly mean temperature was subtracted from
32° F and the difference multiplied by the average snow
depth for the month. The monthly products were then
summed for the winter. Whenever the mean temperature
was above 32° F, the difference was assigned a negative
value and this value added to the snow depth instead of
being multiplied.
POPULATION DYNAMICS AND
MOVEMENTS
Population Trends
Annual trend counts were conducted over most of
Fremont County from 1949 to 1976. Various
Department of Fish and Game personnel conducted the
surveys from 1949 to 1969 while I made most counts from
1970 to 1976. The moose population on the study area
has been declining since the mid-1950's (Fig. 3). The
apparent population recovery about 1970 was probably
due to more intensive censusing associated with this
project. The population declined further during the study
period.
The decline was more pronounced in some herds
than others (Figs. 4 and 5). The Big Bend Ridge-Junipers
population was originally the largest herd with a high
count of 400 moose recorded there in 1952. The highest
number recorded on Big Bend was 319 in 1954 and on the
Junipers the high was 168 in 1952. The Big Bend Ridge
population has shown the greater decline, but both
populations are down. The Junipers group is not clearly
distinct from the Big Bend herd and for this reason they
should be considered as a single population.
The Fall River and Shotgun Valley herds have also
declined while the Island Park population has remained
relatively stable. Possible causes of the declines will be
discussed later.
Table 1. Results of moose herd composition counts in Fremont County, Idaho, 1969 to 1975.
Number RATIO PERCENT COMPOSITION Percent
Year Classified Buii:Cow:Calf Bulls Cows Calves Twinning
1969 236 66:100:61 29 44 27 12
1970 125 96:100:65 37 38 25 10
1971 237 95:100:58 37 40 23 15
1972 138 70:100:56 31 44 25 17
1973 248 48:100:62 23 48 29 9
1974 113 61:100:85 25 41 34 15
1975 233 71:100:59 31 43 26 7
AVERAGES 190 70:100:62 30 43 27 12
Page 7
Sex and Age Composition
Sex and age composition of the moose population
was determined by aerial counts in late fall. In most years,
there was adequate snow to complete the census before
antler drop commenced in early December. The average
bull:cow:calf ratio for the entire study area from 1969 to
1975 was 70:100:62 with an observed twinning rate of 12
percent (Table 1). Calves comprised 27 percent of the fall
population. The adult sex ratio was significant!{ different
from 50:50, but no major differences in sex and age ratios
were noted among the various sub-populations.
These animals appeared to be as productive as
Shiras moose in Jackson Hole, Wyoming (Houston
1968:60) and various parts of Montana (Schladweiler
1974:65, Stevens 1970:44, Dorn 1969:29, Peek 1962:362),
with a higher twinning rate than reported for most of
those studies. Wilson (1971 :50) reported calf: cow ratios
of 65-80:100 for the Uinta Mountains, Utah.
Three earlier herd composition counts were made on
part of the study area in December 1962, December 1963
and March 1966 (Nielson and Shaw 1967a:6). The
observed bull:cow:calf ratios averaged 116:100:46. The
adult sex ratio did not differ significantly from 50:50, but
the adult and cow:calf ratios were both significantly
different from my sample. Their sample sizes were
smaller than mine (average of 145 compared to 190)
which may partially explain the difference in observed
herd composition. The male segment of the population
may have been reduced and calf survival may have
increased between the early 1960's and the early 1970's.
Table 2. Age composition of hunter-killed moose,
Fremont County, Idaho 1969 to 1975 (excluding calves).
PERCENT
Age Class Legal Illegal
(Years) Harvest Harvest
1¥2 9 15
2Y2 16 23
3¥2 15 18
4¥2 16 10
5¥2 10 5
6¥2 8 8
7¥2 4 8
8%+ 22 13
Sample Size 146 39
Mean Age (years) 5.4 4.6
Page8
Age Structure of Harvest
Moose hunting occured on most parts of the study
area, but was limited to a small number of permits
annually. Permittees were limited to taking antlered bulls
except on Fall River Ridge during 1974 and 1975.
Hunters are further limited to taking one moose per
lifetime in Idaho. A total of 146 mandibles or incisors
useable for aging were obtained from legal hunter kills
from 1969 to 1975 (Table 2).
The hunter harvest may not represent the true age
composition of the fall population due to hunter
selectivity and differential vulnerability among age
classes. Many hunters shoot the first legal moose they see,
but others select for trophy bulls. Yearlings are
considered the most vulnerable class (Pimlott 1959,
Simkin 1965), which would partially offset the bias from
hunter selectivity.
Percentage of yearlings in the legal harvest remained
relatively constant at about 9 percent (Table 2). Houston
(1968:78) in Wyoming and Schladweiler (1974:67) in
Montana reported 20 and 21 percent, respectively,
yearlings in the harvest with either-sex hunting.
Schlad weiler's data showed that the percent of yearlings
in the harvest closely approximated the estimated
yearling component of the population he studied. The
proportion of yearlings in my sample was significantly
lower than in the Wyoming and Montana studies. The
validity of the comparisons is questionable, however,
because Idaho hunting was primarily for antlered moose
and was a once-in-a-lifetime opportunity.
Mandibles were obtained from 39 moose (excluding
calves) killed illegally on the study area. Thirty-three of
these were killed incidental to elk hunting and the entire
carcass was left in the field. The remainder were poached
and only the meat was taken. Sixty-four percent were
females. There was no obvious hunter selectivity in this
sample, and the age distribution should reflect
vulnerability instead of hunter selectivity. Yearlings
comprised 15 percent of this sample (Table 2); higher
than in the legal harvest, but the difference was not
significant and the proportion was still below that
reported in the other studies.
Due to the small sample size, the results are
inconclusive, but they do not rule out the possibility that
high winter calf losses were occurring. It was impossible
to obtain enough spring-summer sightings to determine
yearling:adult cow ratios and thereby estimate winter
calf mortality. Houston ( 1968:72-74) estimated winter
calf mortality ranging from 0-59 percent during three
winters in Jackson Hole and suggested 20 percent as a
long-term average.
Mortality Factors
Known losses averaged 75 moose per year on the
study area (Table 3). The distribution of losses by cause
of death differed significantly (Pc( 0.01) among years
with the major change being in illegal kills. Comparisons
among causes of mortality should be made cautiously
since essentially all legal harvest was reported whereas
there was no way to totally enumerate other losses.
Hunting. Hunter harvest, including legal, illegal,
and Indian, accounted for 79 percent of the recorded
losses. It probably was the most important mortality
factor, although its importance was overestimated
because hunting mortality was more easily detected than
natural mortality. Moose permits issued for the study
area ranged from a low of 26 to a high of 60 during the
study. Hunter success averaged 90 percent. The most
important change in hunting regulations was made on the
Fall River area. Initial study revealed relatively high
moose densities, high browse utilization (see browse
utilization and condition section) and annual winter
losses. Permit numbers were subsequently increased, the
moose season opening was delayed until mid-November
beginning in 1973 to harvest the migratory segment from
Wyoming (see movements section), and either-sex
hunting was allowed in I 974 and I 975. The population
declined further so permit numbers were reduced in 1975
and either-sex hunting was terminated. Because of the
long-term population trend, moose hunts were closed in
Fremont County in 1977.
The extent of illegal harvest is unknown, but
potential impact is high because the area is heavily
roaded, has high human activity year-round, and the
behavior of moose makes them vulnerable. Illegal kill is
generally of two types; poaching for meat, and incidental
to other big game hunting. In the latter type, the meat is
usually wasted. The incidental kill was high during the
early phases of the study, but elk hunting seasons were
changed in 1974 which dispersed hunting pressure and
reduced the incidental kill of moose.
Shoshone-Bannock Indians residing on the Fort
Hall Reservation have treaty rights to hunt on
unoccupied Idaho lands belonging to the United States.
They may take game without restriction and are not
required to report their take. The known Indian harvest
averaged less than 5 moose per year, but these were only
the ones which conservation officers personally observed
or otherwise verified. Six Indian kills were reported by
the officers in 1976, but at least 12 moose killed on the
study area by Indians were processed by locker plants
(Brent Nyborg 1977, pers. comm.).
Table 3. Moose mortality recorded on the study area 1969 to 1975.
NUMBER KILLED
Cause of Mortality 1969 1970 1971 1972 1973 1974 1975 Total Average Percent
Legal Hunter Kills 23 25 24 26 48 53 18 217 31 41
Illegal Kills 32 40 18 23 27 19 6 165 24 31
Indian Harvest I 2 5 10 7 5 2 32 5 6
Natural I 2 9 7 I2 10 8 49 7 9
Accidents 5 9 4 6 8 9 10 51 7 10
Unknown Causes 0 2 I 0 3 3 4 I3 2 2
TOTALS 62 80 61 72 105 99 48 527 75 99
Table 4. Summary of moose tagged in Fremont County, Idaho, 1961 to 1976.
--ADULTS----CALVES--
Years Location Male Female Male Female Totals
70-75 Fall River Range 4I 61 26 3I I 59
6I-70 Junipers 50 39 0 0 89
74-76 Big Bend Ridge 14 29 7 7 57
62-67 Island Park 15 5 I I 22
66-67, 74-76 Shotgun Valley 7 9 2 6 24
TOTALS 127 143 36 45 351
Page 9
Malnutrition. Deaths attributed to malnutrition
occurred every winter. The fact that winter mortality was
detected consistently despite the low population densities
suggests the actual losses may have been substantial.
Losses regularly occurred even on the Big Bend range
where forage was relatively abundant and in good
condition (see browse utilization and conditions section).
Climatic conditions may have been more important to
moose survival than forage quantity.
Of 39 deaths attributed to malnutrition, 17 were
calves (44 percent), 18 were adults ( 46 percent) and 4 were
unclassified. Calf losses included 4 males, 7 females and 6
of unreported sex. Females outnumbered males two-to-
one in the adult sample, but this difference was not
significant from a 50:50 ratio. Adults were mainly over
eight years old. Houston (1968:71) also reported that
calves and old females were the most affected by winter
mortality in Jackson Hole. Calves comprised 65 percent
of his sample, however.
Accidents. Accidents accounted for I 0 percent of the
recorded mortality (Table 3). Collisions with motor
vehicles were the most frequently observed cause. Several
also drowned by breaking through ice and calves
occasionally became entangled in fences. Like legal
harvest, the importance of accidental deaths may be
overestimated since such losses, mostly on roads, are
more easily detected than other forms of mortality.
Parasites and Diseases. Moose ticks (Dermacentor
albipictus) were frequently found on immobilized moose
and along moose tracks during late winter. Some
individuals had numerous ticks which undoubtedly
caused some stress, but the effect of this parasite upon
moose is unknown. Ticks from five moose were
submitted for laboratory examination, but no pathogens
were found.
Five moose died during summer and fall periods
from unknown causes. Except for two blind moose, no
two animals exhibited the same symptoms and no
causative agents were identified. All were adults except
one five-month-old calf. Parasites and diseases do not
appear to have a major impact upon the moose
population.
Predation. Predators capable of consistently taking
moose are scarce in Fremont County. A grizzly bear
( Ursus arctos horribilis) evidently killed and fed on a cow
moose and her twin calves on Fall River Ridge in March
1972. A grizzly was observed feeding on a moose carcass
in Island Park the previous spring, but cause of death was
undetermined. Grizzly bears are too scarce to be of major
importance.
Alleged sightings of wolves (Canis lupus) have been
rather frequent in recent years, but I know of no instance
where the presence of this predator has been verified.
Black bears ( Ursus americanus), while relatively
abundant, are ineffective predators on moose except for
taking young calves. Natural predation appears to have
limited impact upon moose populations in Fremont
County.
Page 10
Climatic Trends. The average winter severity index
for Island Park Dam for the winters of 1939-40 to 1976-
77 was 2,376 (Fig. 6). The average for the study period
( 1969-70 to 1975-76) was II percent above the long-term
average. For comparison purposes, winters with ratings
more than 20 percent below or above the mean were
designated as mild or severe, respectively. The data were
then grouped into 4 periods based upon similar ratings.
The 6-year period from 1939-40 to 1944-45 had I
moderate, I severe, and 4 mild winters. The moose
population was presumably increasing at that time. The
next 7 years ( 1945-46 to 1951-52) were more severe, with
no mild winters. The 1951-52 winter was the most severe
on record. The population decline began during the early
1950's and the weather during that period may have
contributed to the initial population crash.
The period from 1952-53 to 1962-63 was relatively
mild with 7 mild, I moderate, and 3 severe winters. The
population should have recovered during that time if
winter severity was a major factor, particularly during the
four consecutive mild winters, 1957-58 to 1960-61. It
appears, therefore, that the continued decline was caused
by factors other than winter severity.
The 1963-64 winter began 13 years of more severe
weather conditions which included the study period.
Only I mild winter occurred during the 13 years, and the
average winter rating was 15 percent above the long-term
mean. A trend to cooler spring temperatures with delayed
snow melting and subsequent greenup was also evident.
April ratings were 262 percent higher than during the
previous 25 years. Moose, like other wild ungulates, rely
upon body fat to supplement sub-maintenance
nutritional intake levels from late fall until greenup.
Thus, prolonged winters may be physically more
devastating than brief periods of severe mid-winter
weather (Schladweiler 1974:43). Two mule deer
populations which wintered on lower Big Bend Ridge, an
area of heavy snow accumulation, were adversely
affected during this period. A group that formerly
wintered in Rattlesnake Canyon either moved or died off
completely prior to 1970. The second group, which
wintered on Snake River Butte, would likely have
disappeared by the mid-1970's had it not been for
supplemental feeding by local landowners and the
Department of Fish and Game.
Weather conditions during this study were not
favorable for recovery of the moose population, but the
continued declined uring an earlier period of mild winters
suggests other factors were controlling the population.
Most of the mortality detected during this study was
man-caused, and it may be more than coincidental that a
major decline closely followed the resumption of legal
moose hunting. I suspect that the psychological effect
upon the public of having a "huntable surplus" of moose
may have resulted in increased moose poaching and
incidental kill.
i --
w
I
N
T
E
R
I
N
D
E
X
4,000
SEVERE
3,00 -
1,500
MILD
1,000
~ I I , , I ' I ' I I I I ---,-----r---, r---r ' ,-I I I l I I I I I ' I I I I • I I • I w ~ ~ c.n c.n CJ) CJ) ....., .....,
CD ~ CD ~ CD ~ CD ~ CJ)
I 1 I I I I 1 I I ~ ~ c.n c.n CJ) CJ) ....., ....., .....,
0 c.n 0 c.n 0 c.n 0 c.n .....,
Figure 6. Winter severity index for Island Park Dam, Fremont County, Idaho, for winters 1939-40 to 1976-77.
0 5 10 15 km
0~1 --~·--~s~·--~·~1o .. ~m~i. .............. ~~~--------~ .................... ..
+ Island Park Moose
• Fall River Moose
YELLOWSTONE
NATIONAL
. ' .....
le~ c: _gi·E
ca o
"tt > -s:
. . . • . . . • .. . ·. . . . . .
PARK
Figure 7. Locations of summer sighting for moose tagged on Fall River and Island Park
(Henry's Lake) ranges.
Page 12
. . .
.. ·-'
Present Population Size
Because the proportion of animals not observed
during surveys is unknown, estimates of total population
size are of questionable value. LeResche and Rausch
(1974), working with known populations, determined
that the proportion of moose seen during aerial surveys
depended upon observer experience, snow conditions,
time of day, terrain and habitat, and that great variation
in results was possible. I found, generally, that highest
counts were obtained in mid-winter (January-February)
when made during clear weather and within 48 hours of
fresh snowfall.
Notwithstanding its weakness, a population
estimate is useful for calculating the calf crop, impact of
mortality factors, and for comparing future changes in
moose numbers. The estimated January 1976 herd levels
were as follows with actual count results shown in
parentheses: Fall River 125 (I 09); Big Bend
Ridge/Junipers 125 (74 BBR, 30 Junipers); Island Park
100 (74) and Shotgun Valley 30, giving a total of 380
moose on the study area. These estimates are based
primarily upon census results for the 1975-76 winter.
Counting conditions were good to excellent. The
Shotgun Valley estimate was made from snowmobile
surveys. The number of sites where fresh tracks but no
moose were found, as well as other general knowledge of
these ranges was also used in making the overall
estimates. The overall estimate is probably conservative,
but I doubt that the actual numbers were much higher.
Assuming an average winter herd composition of 30
percent males, 44 percent females and 26 percent calves, a
January population of 380 moose, and 20 percent late-
winter calf mortality (20 calves), with the same number of
adult deaths of which two-thirds are cows, the post-
winter population would total 108 adult males, !52 cows
and 80 (23 percent) yearlings with a projected calf crop
the following summer of 115. Total winter loss would be
40 moose, about 33 higher than the natural mortlity
recorded during the study. When that winter mortality
estimate is added to the figures in Table 3, annual losses
average 108 per year, which approximates the calculated
calf crop. At the 20 percent calf mortality level, yearlings
would comprise 27 percent of the summer bull
population and 21 percent of the cow population.
Yearlings were poorly represented in the harvest (Table
2), which suggests that calf loss between fall counts and
the following hunting season was higher than the 20
percent used in this calculation or that there was
substantial hunter selection.
Seasonal Movements
Knowledge of movement patterns and location of
seasonal ranges used by ungulates is important to making
appropriate management decisions. Nielson and Shaw
(1967a, 1967b) began a moose movement study on the
area in 1961 with investigation of the Junipers and Island
Park populations. Some follow-up observations were
made during this study and movements of the Fall River,
Big Bend Ridge and Shotgun Valley populations were
studied.
Fall River. A total of 159 moose were tagged on the
Fall River range from 1970 to 1975 (Table 4), and 282
subsequent observations of these moose were recorded.
Winter observations were 2.8 times more frequent than
summertime sightings. These moose traditionally
returned to the Fall River range where 99 percent of the
winter observations were recorded. The remaining I per-
cent of sightings were all from Big Bend Ridge 20 miles
WNW of the Fall River range.
Eighty-two summer sightings of these moose were
recorded through 1976. Twelve percent were from Island
Park, 56 percent from Wyoming, and 32 percent from the
Fall River range (Fig. 7). The mean distances moved from
winter range to the three summer areas were 34, 16 and 5
airline miles (54, 26 and 8 km), respectively.
Tags were recovered from 29 ( 18 percent) Fall River
moose. "Hunting season" kills, legal and illegal, totaled
10 in Idaho (6legal) and 13 in Wyoming (9legal). From
1970 to 1976, Idaho permittees killed 103 moose on the
Fall River range (15/year average). Based upon tag
returns, Wyoming hunters took at least an equal number
during the same period.
The data indicates that two-thirds of the Fall River
winter herd is migratory, and about half the population
moves up the drainage into Wyoming for the summer.
Wyoming moose hunting harvest comes from this seg-
ment of the population. Idaho hunts should be directed at
the resident segment. Close cooperation and coordina-
tion between Idaho and Wyoming is essential to properly
manage this herd.
Part of this herd summers in Yellowstone Park,
where it is protected from all sources of hunting mortality
from spring until late fall, and this may partly explain
why this population declined less than some of the other
herds (Figs. 3-5). The Fall River population declined dur-
ing the study, from 154 moose observed in February 1971
to 109 moose seen in January 1976. The 1976 count was
believed to be more accurate since moose were seen at 80
percent of the sites where fresh tracks were found com-
pared to only 61 percent during the 1971 census.
Junipers -Big Bend Ridge. Eighty-nine moose were
tagged on the Junipers range from 1961 to 1970, and 57
on Big Bend Ridge from 1974 to 1976 (Table 4). Tags
were recovered from 12 and 7 percent of the respective
groups. Observations showed that most of these moose
were resident to north-central Fremont County during
the summer (Fig. 8) where much of the hunter harvest
occurred. Hunter harvest, including Indian and illegal,
may have caused the population decline evident from the
mid-1950's to mid-1970's (Fig. 4).
Island Park. Twenty-two moose were tagged in the
Henry's Lake area of Island Park between 1962 and 1967
(Table 4). Most summer sightings of these moose were
also from the Island Park area (Fig. 7). Some of the
moose moved to higher elevations during summer. Mean
distance between winter range and summer sightings was
8 miles (13 km). Tags were recovered from 9 percent of
the marked moose.
Page 13
~----0 5 10 15 km. ____ _,,.,.,.----r-.,---------· of-----'----,5----'-----''-r-1 0 mi.
I
N YELLOWSTONE
I
NATIONAL
• Junipers Moose
RANGE + Big Bend Moose
PARK
........ . • . • • • ...
Figure 8. Distribution of summer sightings for moose tagged on the Junipers and Big
Bend Ridge winter ranges.
Page 14
. . • • • • • • • • : .
o I • • .... •
Shotgun Valley. Twenty-four moose were tagged in
Shotgun Valley between 1966 and 1976 (Table 4).
Limited summer sightings (7 in Idaho) suggest that the
movements of this population were confined to the Cen-
tennial Mountains. One of these moose was killed in
Montana.
Another group of moose wintered I 0 to 20 miles ( 16-
32 km) west of Shotgun Valley near Spencer, also on the
south slopes of the Centennial Mountains. Winter moose
densities were higher than in Shotgun Valley and this
population has apparently increased in recent years,
although historical records are poor. Snow accumula-
tions there are less than in Shotgun Valley. I did not
determine whether these moose were part of the Shotgun
Valley herd or a distinct population.
Home Ranges
Five adult moose (3 females, 2 males) captured on
the Big Bend range in April I976 were equipped with
transmitter collars. They were radio-tracked until
December 1976 to determine home ranges, seasonal
movements, timing of migration, and cover types used
during summer. Home range, as used here, refers to the
area utilized by an individual during the summer-fall
period.
Radioed moose were located two to four times per
week from June to August, and an average of once per
week the remainder of the period. With the exception of
two flights during spring migration, all radio-tracking
was done from the ground with hand-held equipment.
Signal range from elevated points was sometimes in
excess of 20 mi. (32 km), but signal error was propor-
tional to distance and bearings had to be taken from with-
in 0.5 mi. (0.8 km) of the animal to pinpoint locations
within ±25 yards (23 m). The many roads on the area
usually allowed this degree of accuracy, except for cow
No.8.
Summer Home Ranges. The five radioed moose
moved to the Island Park Caldera for the summer (Fig.
9). Cows had smaller home ranges than bulls. They
ranged from 6 to 10 and averaged 7.4 sq. mi. (16 to 26, 19
km 2). Cow No.8, which had the largest home range, had
two centers of activity within her range. She spent most of
the time near Moose Creek Butte, but also spent time in
another area 2.5 mi. (4 km) west on at least two different
occasiOns.
Home ranges used by the two bulls were 12 and 20
sq. mi. (31 and 52 km2), respectively. Neither bull dis-
played a rapid movement to summer range as did the
cows. One spent the month of June traveling from the
upper part of the winter range to the east side of Henry's
Fork, a distance of 7 mi. (II km). He then spent the next 2
months in a 4 sq. mi. (10 km2) area. During the rut he
returned to the area used in early June. The other bull
ranged across a 20 sq. mi. (52 km2) area throughout the
summer which included the upper extremity of Big Bend
Ridge.
These summer home ranges were substantially
larger than those reported for other studies. Most
workers have reported summer home ranges smaller than
2 sq. mi. (5 km2). (Schladweiler 1974:22, Van Ballen-
berghe and Peek 1971:69, Dorn 1969:32, Houston
1968:51, Knowlton 1960: 165). Phillips et a!. ( 1973:270)
found ranges of 6.9 and 5.6 sq. mi. (18 and 15 km2) for
cows and bulls, respectively, in northwestern Minnesota.
The reason for the larger home ranges in this study is
unknown. The most obvious difference between this
study and the others was the cover types used. All five
moose made extensive use of lodgepole pine forest, and
four of them used it almost exclusively.
No unusual movements by the cows were detected
during the rut in late September and October. The influ-
ence of the rut upon bull movements was not accurately
determined. The transmitter on one bull had weak power
output, making tracking difficult. He was located only
four times between September 15 and October 10. These
locations were spread over 3 sq. mi. (8 km2) and were 6 mi.
( 16 km) west of where he spent July and August, but were
in the same area he used during June. He could not be
located on several occasions during the period. He was
killed October 10 by a hunter.
The other bull stayed within his home range and
showed only "normal" movement during the early part of
the rut. He was last located September 29 and was either
killed soon thereafter or his transmitter quit functioning.
Increased movement by bulls during the rutting season
has been reported in other studies (Sch1adweiler 1974:20,
Phillips eta/. (I973:273, Houston 1968:53).
Winter Home Ranges. There was no opportunity to
track individual moose for the entire winter period, but
observations of marked individuals for varying periods
indicated many winter home ranges were as described by
Van Ballenberghe and Peek ( 1971 :69): " ... a series of
high-use areas connected by wanderings of various dis-
tances." In several instances, wintering moose confined
their movements within 10 acres (4 ha) for several weeks
before moving to another area.
The home ranges of the five radioed moose from
early April until migration to summer ranges varied from
2 to 6 sq. mi. (5 to 16 km2). Their movements during this
period of snow melt and greenup were probably greater
than during the deep-snow period.
Timing of Migration. Two of the radioed cows (Nos.
6 and II) raised calves during the I976 summer. The third
had a calf at her side when tagged, but did not rear
another in 1976. Nos. 6 and II both moved to summer
range between May 5 and 12 while there was still con-
siderable snow at higher elevations, however, the weather
had warmed and snow melt was progressing rapidly.
Their summer ranges were 6 and 23 mi. (10 and 37 km),
respectively, from the tagging sites. Most calves are born
in late May and early June and impending parturition
might have been a factor in their early movement. Cow
No.8 stayed on winter range until May 29 before moving
15 mi. (24 km) to summer range.
Page 15
~ -0')
.
0 1 2 3
Bishop
~·..!.
/f'
Mtn.
Mi.
~
.Last
Chance
PARK
CALDERA
8 <j# 8 Q \ \ ~ c ~ c
~~~<>
8 Tagging Sites RIDGE
Figure 9. Summer home ranges of 4 radioed moose, Fremont County, Idaho 1976.
Eccles
..,J ,,
-;,~
Butte
I
N
,.,
Warm R. -:: f. Butte "'
The two bulls left winter range later than the cows.
They both left Big Bend Ridge about June 9 and took
several days to move to the areas where they spent most
of the summer. Their summer ranges were centered 5 to 7
mi. (8 to II km) from winter range.
The fall migration in 1976 was later than normal due
to lack of snow. In other years of the study moose were
usually concentrated on winter ranges by late November.
The 1976-77 winter was the driest on record, and the
radioed cows stayed on summer range until January. By
the end of December there was less than I ft. (30 em) of
snow on top of Big Bend Ridge. A major storm January
l-3 brought snow depths on top of the Ridge to 2.5 ft. (76
em) and to I ft. (30 em) at the bottom. On January 5, two
radioed cows were back on winter range while the third
remained on summer range. This cow had returned to
winter range when checked again February 14. One
radioed bull was killed by a hunter, and the other dis-
appeared prior to the fall migration.
Whether the two cows found on winter range Jan-
uary 5 moved just prior to, during, or after the storm of
January 1-3 is unknown, but tracks showed that moose
movement from Island Park Caldera to Big Bend Ridge
occurred daily during the week following the storm. I
conclude that snow depth is a vital factor regulating the
fall migration, and that depths in excess of l ft. (30 em)
are required to trigger movement.
HABITAT RELATIONSHIPS
Food Habits
Food habits were determined from analysis of 94
rumen samples and 290 feeding sites. Plant species con-
stituting 5 percent or more of the diet during summer and
fall periods are listed in Table 5 and those for winter in
Table 6. Species receiving under 5 percent of the total use
are shown in Appendix Table 2. Browse was the most
important forage class used throughout the year. Non-
woody plants received their highest use during summer
except in Island Park where they were used most during
winter (Tables 5 and 6).
Summer and Fall. Summer data are from 8 rumen
samples and 6 feeding sites (Table 5). Most of these sam-
ples were obtained from the willow and lodgepole pine
vegetation types. While the sample is small, it reveals
important food species and seasonal trends. Willow and
fireweed were eaten in the greatest amounts, and non-
woody forage formed 44 percent of the diet (Table 5).
Other studies have shown much variation in the summer
diets of Shiras moose (Peek l974b:20l). In Jackson Hole,
the summer diet ranged from 100 percent browse in
floodplain forest to nearly 100 percent herbaceous mate-
rial on agricultural and aquatic types and averaged about
75 percent browse and 25 percent non-woody vegetation
(Houston 1968). In three Montana studies, browse
formed 29 (Knowlton 1960:166), 45 (Schladweiler
1974:31), and 98 percent (Dorn 1970:562) of the summer
diets. Willow was a key forage in all these studies. Fire-
wood was utilized in Jackson Hole (Houston 1968:27), in
the upper Madison, Montana (Schladweiler l974:30)and
in this study.
Fall rumen samples came from the entire study area,
but could not be broken down by specific vegetation
types. Browse formed 87 percent of the fall diet. Other
workers have reported similar proportions for this season
(Dorn 1970, Houston 1968, Knowlton 1960, Schlawei-
ler 1974). Betterbrush, willow and snowbush were eaten
in the largest amounts. Lupine was the only forb eaten
regularly. It occurred in 60 percent of the samples and
comprised 3 percent of the consumed forage.
Winter. Foods eaten by moose during winter were
recorded at 284 feeding sites on the five winter ranges
(Table 6). Sites were selected throughout the respective
ranges and in all vegetation types receiving use.
The Junipers range was unique moose habitat and
the winter diet of these moose differed from other popu-
lations on the study area and those reported in the litera-
ture. These moose had the least varied winter diet with
bitterbrush and chokecherry forming 98 percent of the
forage consumed (Table 6).
The Fall River and Big Bend ranges were vegeta-
tionally similar, with interspersed lodgepole pine, Doug-
las fir, aspen, and brush. These similarities were reflected
in the winter foods consumed. Upland willow, aspen,
chokecherry and serviceberry were eaten in greatest
quantities on both ranges (Table 6). Browse formed
nearly 100 percent of the diet. Riparian willows were
more important in the overall diet on the Big Bend range
than the data shows because this type was not sampled
proportional to the percent of the population that win-
tered in it. The importance of bigtooth maple was also
underestimated. It occurred only on 12 percent of the Big
Bend range, but was an important forage item and was
considered a key species where available.
The Shotgun Valley winter range consists primarily
of interspersed conifer species. There were few shrubs in
the understory tall enough to provide winter forage.
Riparian willows and alpine fir were the primary foods
eaten (Table 6). The distribution pattern of Shotgun
Valley moose was similar to the Type 5 winter range des-
cribed by Peek (l974a: 134) where moose used willow
bottoms in early winter and then moved to adjacent tim-
bered slopes. Willow and aspen together formed 60, 42, 7
and I percent of the monthly diets from December
through March while alpine fir comprised 24, 48, 71 and
85 percent for the same months, reflecting the shift from
willow bottoms to the spruce-fir types.
Moose wintering in Island Park utilized two vegeta-
tion types; riparian willows on Henry's Lake Flat and
lodgepole pine forest adjacent to streams. The streams
were spring-fed and contained available aquatic vegeta-
tion year around. Moose utilized aquatics extensively
during winter (Table 6). The amount and species com-
Page 17
Table 5. Forages eaten by moose during summer and fall in Fremont County, Idaho, 1969 to 1976. Species listed formed
at least 5 percent of the total for one season. Aggregate percent with percent frequency in ( ).
Species or Forage Class SUMMERa FALLb
BROWSE 56 (100) 87 (100)
Bitterbrush 4 (36) 26 (56)
Willow 42 (71) 21 (67)
Snow brush tr (l4)c 18 (63)
Aspen 5 (36) 6 (50)
Other browse 5 17
NON-WOODY 44 (77) 18 (73)
Fire weed 29 (50) tr (2)
Aquatics 6 (14) tr (3)
Other forbs l 5
Grass & grass-like 8 (43) 8 (70)
a 8 rumen samples and 6 feeding sites, (1,598 instances of use)
b 86 rumen samples
c tr=trace < 0.5 percent.
position of aquatics used were quantified in only a few
instances when moose were observed feeding in water.
The amount of aquatic vegetation eaten at other sites was
estimated as follows: the average number of instances of
use was computed for sites with no aquatic feeding (461/
site) and for sites with partial aquatic feeding (339/site).
The difference ( 122/ site) was added to each of the latter
as an estimate of aquatic feeding. Although crude, I
believe it is a conservative estimate of the importance of
aquatics.
Willow, lodgepole pine, and aquatics together
formed 86 percent of the forage consumed in Island Park
(Table 6). Lodgepole pine and aquatics were used spar-
ingly in other reported studies of Shiras moose (Peek
l974b:l97-20l). Craighead et al. (1973:38) reported that
elk wintering in Yellowstone Park thermal basins also
consumed large quantities of lodgepole pine along with
mistletoe, sedges and aquatics. Lodgepole pine normally
receives only minor use, but was important to Island
Park moose where large quantities of aquatic vegetation
were also consumed during winter. Island Park moose
showed no apparent preference for the parasitic dwarf
mistletoe as did the elk in Yellowstone. The aquatics
eaten most frequently were green algae and watercress.
Four different winter diets were evident on the study
area, demonstrating the adaptability of Shiras moose to
various habitat types and forage species. Composition of
the diet on a given winter range was directly related to the
presence of preferred browse species. All major species in
the diet were readily eaten wherever they occurred except
lodgepole pine which was a prominent item only in Island
Park.
Page 18
Forage species eaten by moose, but too sparsely dis-
tributed to contribute greatly to the diet, were mountain
maple, mountain ash, red osier dogwood, huckleberry
and currant. Species seldom browsed were hawthorn,
snowberry, rose, juniper and Engelmann spruce.
Browse Utilization and Condition Trend
Winter is a critical stress period for ungulates on
mountainous ranges due to adverse weather conditions,
restricted forage availability and reduced nutrition levels.
Since forage availability is a key factor regulating the
number of moose a range will support, measurements of
browse utilization and condition trend indicate whether
carrying capacity has been exceeded. Permanent tran-
sects for measuring these factors (Cole 1963) were estab-
lished on the Fall River, Junipers, Big Bend and Island
Park ranges.
Fall River. Twenty-three browse transects were
established on the Fall River range in 1970 and 24 more in
1971. All were established on sites supporting relatively
high winter densities of moose. Some transects were
abandoned after 1972 when the study was expanded to
other ranges, but others were read annually through
1976. Because utilization and plant condition differed
substantially between mature forest stands and clearcuts,
the two types will be discussed separately.
In mature forest stands, upland willow and aspen
plants were browsed heavier and were in poorer condi-
tion than were serviceberry and chokecherry plants
(Table 7). Mortality of the first two species made it diffi-
cult to find an adequate sample along some transects by
the mid-1970's. In 1974, 26 and 17 percent, respectively,
of the available willow and aspen plants were dead, com-
pared to 2 and 5 percent of serviceberry and chokecherry,
respectively. Densities of palatable shrubs normally
decrease in advanced stages of forest succession (Cowan
eta/. 1950), and in this instance attrition of upland willow
and aspen was accelerated by heavy browsing. Service-
berry and chokecherry plants appeared to be decreasing
at a slower rate.
Utilization levels of the various species remained
relatively constant throughout the study period even
though the moose population declined. This may have
resulted from sampling only heavily used habitat. Moose
concentrated on sites with the best food and cover and if
any major changes in utilization and condition occurred,
they were on more marginal sites. For example, the area
south of Fall River supported low densities of moose
from 1972 to 1975 (average of 22 observed on aerial
flights}, but in 1971 and 1976 this area wintered higher
numbers (average of 55 observed on aerial flights). This
suggests the area had the capacity to support more moose
than normally wintered there. Rising Butte had a similar
pattern of use.
The effect of variation in annual snowfall upon plant
condition ratings should also be noted. Only available
forage plants were sampled along browse transects and
availability was directly related to snow depth; the deeper
the snow, the fewer available plants. The 1975-76 winter
had below average snow cover, making many plants
Table 6. Forages eaten by moose during winter (Dec.-Apr.) on 5 Fremont County, Idaho, ranges 1969 to 1976.
Species listed formed at least 5 percent of the total for one range. Aggregate percent with percent frequency of occurence
in ( ).
Range JUNIPERS FALL RIVER BIGBENDRIDGE SHOTGUNVALLEY ISLAND PARK
Years 1970-71 1970-73 1973-76 1973-76 1973-76
No. Feeding Sites 18 49 87 62 68
Instances of Use 8,431 20,004 46,766 27,522 32,308
Species or Forage Class
BROWSE 99.9 (100) 99.9 (100) 99.9 (100) 95 (100) 74 (94)
Bitterbrush 82 (94) I (6) tr (6)a
Upland willow -22 (69) 23 (57)
Unident. willow -I (6) 4 (8) 21 (44) 35 (69)
Aspen -32 (96) 13 (76) 8 (45) 9 (47)
Chokecherry 16 (78) 12 (55) 27 (79) tr ( 10) tr (4)
Serviceberry -17 (61) 13 (60) tr (1 0) tr (7)
Douglas fir 5 (33) 6 (48) 5 (45) tr (6)
Lodgepole pine 5 (31) tr (8) 3 (31) 24 (65)
Bigtooth maple -5 (10)
Alpine fir --tr (2) 55 (89) 4 (14)
Other browse 2 5 7 3 2
NON-WOODY
Aquatics tr (2) 5 (19) 27 (68)
a
tr = trace <0.5 percent.
Page 19
available which were previously unavailable. Naturally
these were less hedged and decadent, giving the false
impression of improved plant condition. This is only one
of several factors which make it difficult to precisely
assess carrying capacity and range trends.
Approximately 10 percent of the Fall River winter
range was clearcut logged during the 1960's and early
1970's. Shrub growth on the oldest clearcuts was tall
enough to provide winter forage during the study (Fig.
10). Aspen regeneration dominated the clearcuts with
moderate amounts of willow and lodgepole pine. A few
serviceberry and chokecherry plants were also present by
1975. Aspen utilization levels in clearcuts were signifi-
cantly lower than those in a mature forest, and plant
condition ratings were correspondingly better (Tables 7
and 8). Moose sought out the willows in the clearcuts,
however, and browsed them as heavily as in the mature
stands (Tables 7 and 8). Willow plants in the clearcuts
were more vigorous than those under the forest canopy,
with significantly less hedging and decadence.
Junipers -Big Bend Ridge. The Junipers and Big
Bend winter ranges supported low moose densities and
overall browse utilization levels were about half those on
the Fall River range (Tables 7, 9, and 10). Utilization
levels were well below the maximum permissible. Both
ranges had supported higher moose numbers during the
1950's and 1960's and there was no visible evidence that
browse plants had been damaged by browsing.
Dead moose, both calves and adults, were found on
Big Bend range during most winters despite the good for-
age conditions. Necropsy indicated malnutrition was the
Table 7. Utilization and condition of important forage species in mature forest stands, Fall River
winter range, 1970 to 1976.
Percent Percent
Number Leaders Severely Percent
Species Year Transects Browsed Hedged Decadent
Upland Willow 1970 10 85 67 23
1971 16 85 81 51
1972 16 78 92 54
1973 15 69 82 47
1974 7 79 58 41
1975 8 82 78 48
1976 13 77 46 31
Average 79 72 42
Aspen 1971 13 74 43 34
1972 13 65 59 33
1973 II 68 67 43
1974 12 70 39 42
1975 5 72 35 34
1976 7 69 20 22
Average 70 44 35
Serviceberry 1970 4 75 22 4
1971 10 55 32 6
1972 10 70 43 14
1973 II 36 38 14
1974 10 58 24 4
1975 6 71 19 8
1976 6 61 24 4
Average 61 29 8
Chokecherry 1970 9 62 27 5
1971 8 54 36 25
1972 7 53 43 32
1973 7 30 23 23
1974 6 47 15 20
1975 3 34 10 31
1976 7 43 5 13
Average 46 23 21
Page 20
Table 8. Utilization and condition of important forage species on the Fall River Ridge clearcuts, 1971 to 1976.
Percent Percent
Number Leaders Severely Percent
Species Year Transects Browsed Hedged Decadent
Upland willow 1971
1972
1973
1974
1975
1976
Average
Aspen 1971
1972
1973
1974
1975
1976
Average
cause of death. However, only 2 deaths, both old-age
adults, were documented on the Junipers range where
snow depths were minimal. It appears that winter losses
were greater on Big Bend Ridge where conditions were
more severe, and this may be a reason this population had
declined faster than the Junipers group.
Island Park and Shotgun Valley. Browse utilization
was moderate in Island Park and forage plants were
generally in good condition (Table II). A few dead moose
were found each winter in Island Park, although mortal-
ity was more observable there because moose and human
activity were both concentrated along streams.
Browse transects were not established on the Shot-
gun Valley range. That population was at a low level and
2 81 10 0
2 78 60 6
3 47 80 JQ
4 75 30 II
3 84 50 10
3 78 40 5
74 45 8
4 31 2 2
2 15 I 0
4 16 10 8
6 9 4 I
5 33 I 3
3 41 5 2
~ 24 4 3
was exerting little pressure on the available forage.
Riparian willows received negligible use. A few alpine fir
trees received heavy use, but many trees were not
browsed at all.
Winter length and severity may have been the pri-
mary causes of winter mortality observed during the
study since forage availability appeared adequate on
most ranges, particularly Big Bend Ridge. The winters
were above average in severity (Fig. 6), and some losses
are expected under these conditions. It was not deter-
mined that winter mortality was abnormally high for the
conditions. It is also possible the problem was qualitative
rather than quantitative. Forage samples were collected
from the Junipers, Big Bend and Fall River ranges for
mineral analysis, but the results are not yet available.
Table 9. Utilization and condition of important forage species on the Junipers winter range, 1970 to 1973.
Percent Percent
Number Leaders Severely Percent
Species Year Transects Browsed Hedged Decadent
Bitterbrush I970 I8 I9 0 I7
I97I 9 39 6 IS
I972 9 43 IS 20
I973 9 36 I8 14
Average 34 IO I6
Chokecherry I970 I4 39 22 II
I97I 7 34 37 IS
I972 7 25 I4 23
I973 7 30 I2 2I
Average 32 2I I8
Page 21
,//('"
' ,j ;
' ·~
Figure 10. Winter photo of Fall River clearcuts.
Table 10. Utilization and condition of important fo rage species on the Big Bend Ridge winter range , 1974 to 1976.
Percent Percent
Number Leaders Severely Percent
Species Year Transects Browsed Hedged Decadent
Upland willow 1974 7 48 32 II
1975 7 53 44 31
1976 6 52 16 15
Average 51 31 19
Riparian willow 1975 2 54 37 4
1976 4 67 12 4
Average 60 24 4
Aspen 1974 8 44 20 15
1975 8 35 25 21
1976 7 34 13 12
Average 38 19 16
Serviceberry 1974 8 32 6 3
1975 9 27 10 3
1976 6 33 I 0
Average 31 6 2
Chokecherry 1974 9 25 6 4
1975 8 21 6 10
1976 7 25 I 5
Average 24 4 6
Bigtooth maple 1974 2 35 10 4
1975 3 16 2 4
1976 3 13 I
Average 21 4 3
Page 22
Table 11. Utilization and condition of important forage species on the Island Park winter range, 1974 to 1976.
Percent Percent
Number Leaders Severely Percent
Species Year Transects Browsed Hedged Decadent
Riparian willow 1974
1975
1976
Average
Aspen 1974
1975
1976
Average
Lodgepole pine 1974
1975
1976
Average
Alpine fir 1974
1975
1976
Average
Seasonal Use of Vegetation Types
Seasonal use of vegetation types was determined
from I ,674, 662 and 956 moose observations on the Fall
River, Big Bend, and Island Park areas, respectively (Fig.
II). The sample from Shotgun Valley was inadequate to
show seasonal trends and nearly I 00 percent of the moose
sightings on the Junipers range were from the sagebrush-
grass type.
The lodgepole pine vegetation type received the
highest use during summer on the Fall River, Big Bend
and Island Park ranges when observed use was nearly
proportional to its relative abundance (Fig. II). Five
moose tagged on Big Bend Ridge were radio-located 183
times during the 1976 summer with 91 percent of these
locations being in lodgepole pine. This indicates the
lodgepole pine type may receive even higher use than the
visual observations indicate. There are at least two fac-
tors which contribute to the high use of lodgepole pine
type during the summer. One, it is the predominant cover
type on those summer ranges. The second is that most of
the willow and aquatic sites are scattered throughout the
lodgepole pine type. My observations and the food habits
information both indicate moose were attracted to
willow areas for feeding. However, moose spent most of
their non-feeding time in adjacent lodgepole pine cover.
Thus the data likely exaggerated the importance of the
lodgepole pine type and underestimated the importance
6
6
6
4
3
2
2
2
0
I
I
I
55 24 15
58 37 17
35 6
49 22 II
59 28 27
41 25 18
38 5 16
46 19 20
4 7 2
4 2 0
4 4
4 28 5
0 27 3
5 5 0
3 20 3
of small willow patches and other types interspersed with
the lodgepole pine stands.
Moose made an obvious shift to other cover types
during winter. A general scarcity of tall shrubs in lodge-
pole pine stands appeared to be the primary factor limit-
ing winter use of this habitat type. Aspen and mixed
aspen-conifer stands received the highest use from fall
through spring on the Fall River and Big Bend ranges
(Fig. II). Winter sightings in these stands were signifi-
cantly more frequent than would be expected if distribu-
tion were random. These stands provided good cover and
abundant forage. During late winter (March), moose
shifted into heavy conifer cover and the use of aspen
cover declined. Figure ll does not illustrate this, how-
ever, since the data were averaged for the entire season.
Observed use of the aspen and aspen-conifer types during
summer was significantly lower than the availability of
those types. One reason is that most moose moved to
higher elevations during summer where aspen was scarce.
Small sample sizes and observation error due to luxuri-
ant undergrowth were also potential biases.
Willow habitat, though very limited, was important
to moose. It received higher use than expected in all sea-
sons except during fall on Fall River and Big Bend Ridge.
Aquatic habitat was used extensively in Island Park year
around and it received the highest observed use during
winter (Fig. II).
Page 23
Page 24
p
E
R c
E
100
80
60
40
20 Lodgepole Pine
0~-L--r---------,---------~----------r-~-L~
Apr.-Jun
(209)
Jui-Sept
(87)
Oct-Nov
(448)
Dec-Mar
(930)
N 100
T
0
F
0
8 s
E
R v
A
T
I
0
N s
80
60
40
20
100
80
60
40
20
Apr-Jun
(114)
Jui-Sept
(40)
Oct-Nov
(1 07)
Lodgepole Pine
Dec-Mar
(401)
0-L-L--~--------,----------.----------r-~_.--J
Apr-Jun
(164)
Jui-Sept
(217)
Oct-Nov
(141)
Dec-Mar
(434)
FALL
RIVER
RANGE
BIG
BEND
RIDGE
ISLAND
PARK
Figure 11 . Seasonal use of vegetation types by moose on 3 Fremont County ranges,
1969 to 1976. Sample size is listed under each season and bar graphs show percent of area
occupied by respective cover types.
Winter Use of Cardinal Aspects, Warm River Butte
Warm River Butte (WRB), in the northwest corner
of Fall River range (FRR), was studied to determine the
influence of aspect upon snow depth , temperature, and
moose distribution . This elliptical butte is I x 2 miles ( 1.6
x 3.2 km) at the base , it rises 600 feet (183m) above the
surrounding terrain and is of volcanic origin (Fig. 12).
Highest elevation is 6,600 feet (2,0 13m). WRB supported
winter moose densitie s equaling or exceeding other parts
of FRR despite steeper s lope s and greater snow accumu-
lations . It was surro unded by lodgepole pine habitat
which supported low moose densities. WRB had conifer
cover on the north side and a mixture of aspen, conifers
and brush on the other aspects. Data were collected from
1971 to 1974 . Parameters measured included snow
depths , maximum-minimum temperatures , pellet group
densitie s and various vegetal characteristics.
Extreme variation in moose use, as estimated from
pellet counts, was found on the 2-square-mile (5.2 km2)
area. Pellet group densities ranged from 3 per acre on the
north aspect to 169 per acre (I to 68 I ha) on the east
(Table 12 ). Winter forage availability, which was
assumed to be roughly proportional to the line intercept
of browse 4 to 12 ft. ( 1.2 to 3. 7 m) tall , was more impor-
tant than snow depth in regulating moose distribution on
WRB. The south aspect had significantly less snow
throughout the winter than the east aspect, but the east
s ide had significantly more browse intercept and pellet
groups (Fig . 12, Table 12). The same pattern was evident
when data for the south, east, and west aspects of WRB
were compared with those for FRR (Tables 12 and 13 ,
Fig. 12), indicating forage availability was also the pri-
mary factor determining winter moose densities on other
parts of FRR. Leege and Hickey ( 1977: 18) reported that
snow depth and forage availability were the critical
factors affecting winter elk distribution in north-
central Idaho, but snow became the overridi ng factor
when depths exceeded 2 ft. (61 err.). Forage availa bility
was more important than snow depth in regulating
moose densities on WRB and other parts of FRR, except
in clearcuts which will be discussed later. Because of their
adaptation to deep snow and their solitary habits , moose
are able to occupy winter habitat in Fremont County
unsuitable for other ungulates .
Snow morphology, as well as depth , influences
ungulate movements (Kelsall and Prescott 1971). I did
not measure s now morphology, but snow density was
adequate to partially support moose during late winter. I
observed that heavy accumulations of low-density snow
which frequently occurred during December and early
January caused moose to leave the steep slopes of WRB,
but they returned after the snow became compacted.
Franzmann et a/. ( 1976) reported defecation rates
for adult moose in Alaska ranging from 10 to 25 groups
per day. Using their combined mean deposit rate of 17 .6
groups per day and a 200 day winter use period , the calcu-
lated winter stocking rate for WRB was 14 .7 moose per
sq. mi . (5 . 7 I km2). The highest aerial count recorded on
Figure 12. East aspect of Warm River Butte.
Page 25
Table 12. Vegetal characteristics, pellet groups and temperatures on the cardinal aspects of Warm River Butte, Fall
River range, 1971 to 1974.
ASPECT
Characteristics North South West East
Number of macroplots 2 4 2 2
Cover type(s) LP Pine/ Aspen & Aspen/D. F. Aspen/D. F.
Douglas Fir Aspen/D. F.
Slope
Canopy Cover a
Grass
Forbs
Shrubs
Trees
Litter
Pellet groups per acre (3 year average)
Line intercept of key forage species 4-12 ft. tall
(ft. of intercept/ IOO ft. line)b
Mean temperature, °F., ll/6/72 to 5/9/73,
17 measurements
Maximum
Minimum
Average Snow Depth, Dec. to Apr., in.
47%
38%
4%
48%
57%
91%
3
2.8
35.1
2.8
59
24%
65%
67%
97%
62%
88%
72
10.2
39.2
3.8
43
36%
15%
105%
98%
57%
93%
79
6.7
37.1
3.6
52
32%
60%
105%
102%
24%
84%
169
36.3
38.6
3.7
49
a Canopy cover was originally recorded for individual species. When species totals were combined, cover for the entire
class sometimes exceeded I 00%.
b Key forage species were aspen, upland willow, serviceberry, chokecherry, and mountain ash.
WRB was 9 moose per sq. mi., and I estimated the aver-
age winter density was between 5 and lO per sq. mi. ( 1.9 to
3.9 per km2). The daily defecation rate may be higher on
WRB than that observed in Alaska.
Use of Clearcuts vs. Mature Stands
Winter use of 10-to 15-year-old clearcut areas on Fall
River Ridge by moose was lower than adjacent uncut
stands, particularly during late winter. Study plots were
established to compare vegetal characteristics, browse
utilization, and pellet group densities on the two types,
and to monitor use patterns as the clearcuts matured.
Tree and shrub regrowth was slow following logging. The
tallest trees were only 20ft. (6 m). Regeneration consisted
primarily of aspen, upland willow and lodgepole pine.
As already noted, overall browse utilization was
lower in the clearcuts than in uncut stands (Tables 7 and
8). Pellet groups were significantly (P < .0 l) more a bun-
Page 26
dant in the latter type (Table 13). Intercept of preferred
browse was 14 percent greater in the mature stands but
was not significant. Aspen and willow dominated the
clearcuts, while serviceberry and chokecherry were found
only in trace amounts (Table 13). Densities of the latter
species apparently increase as succession advances.
The presence of tall conifers, which provided escape
and I or thermal cover and pockets of shallow snow under
canopies, made mature stands more attractive to winter-
ing moose than clearcuts. Aspen and willow production
was stimulated by logging of mixed aspen-conifer stands,
but regrowth was slow. Winter forage was unavailable
for 5 to 10 years following logging, and winter use was
still below that in uncut stands after 15 years. Clearcut
logging of aspen-conifer stands on Fall River Ridge
causes reduced winter use for an undetermined period,
and logging of critical winter ranges in this type in Fre-
mont County should be on a sustained-yield system to
prevent wide fluctuations in carrying capacity.
Use of Grazed vs. Ungrazed Willow -Habitat, Henry's
Lake
A pellet group survey of willow habitat near the
mouth of Howard Creek, a tributary to Henry's Lake,
was conducted in May 1972. The site was a moose winter-
ing area and the stream was a spawning area for cutthroat
(Salmo c/arkii) and brook (Salvelinus fontinalis) trout.
The Department of Fish and Game was considering pur-
chase of the land to enhance wildlife values. The survey
was made to evaluate moose use on the willow habitat.
The willows occupied moist meadow lands near the
edge of Henry's Lake. Two willow forms (species unde-
termined) were recognized; a short form less than 8 ft.
(2.4 m) and a tall form over 12ft. (3.7 m) in height. Pellet
counts were made on seven 400 x 500 ft. (366 x 457 m)
macroplots with 16 random 1/50 acre (81 m2) plots per
macroplot. Four macroplots were sampled on pasture
which had been heavily grazed by livestock during
summer and fall (693 droppings/ a.; 280/ ha) and three
were inside a fenced area which had been lightly grazed
(37 droppings/a.; 15/ha). This pattern of grazing had
evidently persisted for several years.
Twenty-six moose pellet groups per acre {11/ ha)
were found on the heavily grazed pasture and 70 per acre
(28/ha) on the fenced area, nearly the same as for the
clearcut and mature timber types, respectively, on FRR
(Table 13). The difference was significant (P<: .001 ). No
data were collected on relative willow densities and
crown cover between the two types, but it was visually
apparent that intensive livestock grazing had reduced
willow cover and vigor (Fig. 14). The root crowns of short
willows were pedestaled and most of the clumps had been
reduced to a few sprigs seldom exceeding 3 feet in height.
Willow communities on Henry's Lake Flat are
important to the Island Park moose herd. Most willows
were on private land and they appeared relatively stable
during this study. However, widespread changes in graz-
ing practices, spraying, burning, or housing development
would adversely affect the willows and would be detri-
mental to the moose. Moose wintering on Henry's Lake
Flat are also extremely vulnerable to harrassment by
snowmobilers due to the level terrain and limited escape
cover.
Table 13. Vegetal characteristics and pellet group densities in mature timber stands and 15-year-old clearcuts on
Fall River Ridge, 1972 to 1975.
Characteristic
Number of macroplots
Trees per acre (over 3 in. dbh)
Percent canopy cover of trees over 20 ft. height
Percent composition of:
Aspen
Lodgepole Pine
Douglas Fir
Line intercept of browse 4-12 ft. tall
(ft. of intercept/100ft.)
Aspen
Upland Willow
Serviceberry
Chokecherry
Other
Total
Pellet groups per acre (4 year average)
Mature Timber
6
289
46
60
27
13
0.2
1.1
5.2
1.2
2.1
9.8
64
Clearcuts
9
0
0
93
7
0
4.9
1.6
tr
tr
tr
6.5
28
Page 27
s
N
0 w
D
E
p
T
H
Page 28
in. em
70
175
60
5
40
30 75
/
20 50
10 25
/
/
DEC
,.,...,....._ __
/ ......... _-r ...... r ........
I '\
I \
I \
J \\
/
JAN FEB MAR
N
\
\
\
\
\
\w
\
\
\ E \
\
\
\
\
\
\
\s
\FRR
APR
Figure 13. Snow depths, cardinal aspects of Warm River Butte and on Fall River Ridge
(FRR), 1971-72 and 1972-73 (2 year averages).
Figure 14. View of willow habitat near mouth of Howard Creek showing heavily-grazed area on left and
lightly-grazed area on right (May, 1972). Henry's lake is in background.
MANAGEMENT RECOMMENDATIONS
A primary management objective should be to pre-
serve the moose in the fauna of Fremont County. This is
desirable because the habitat is suitable and the animal is
esthetically valuable to northern Fremont County where
tourism is vital to the local economy. Hunting and mal-
nutrition caused most of the mortality observed during
this study. Legal hunting, although not the main cause of
mortality, should be terminated and efforts made to
reduce the Indian and illegal harvest to allow the popula-
tion to recover. Ideally , the moose population should be
managed to allow hunter removal of surplus animals , but
it has not been demonstrated that the population will sus-
tain legal hunting when added to other mortality . The
Fall River herd was the only one which appeared close to
range carrying capacity, and limited hunting could be
allowed again if that population increases above present
levels. Any hunting of Fall River moose should be corre-
lated with Wyoming, since hunters in both states hunt
that population .
Options available to the Department of Fish and
Game for managing moose in Fremont County will be
limited b y Indian and illegal harvest levels. The potential
impact of both factors upon the moose population is
large, and effective control over either one will require
voluntary cooperation by the parties involved . Hunting
activity by Indians in Fremont County increased sub-
stantially about 1971. Other human activity and access
have also increased , with a likely increase in poaching.
Jealousy over Indian rights by non-Indians seems to have
fostered the attitude that "moose are being eliminated
anyway and I want my share." I recommend that the
Idaho Department of Fish and Game negotiate with the
Shoshone-Bannock Tribal Council to establish harvest
quotas for moose . Quotas should be established for speci-
fic hunting units and be based upon current moose num-
bers and population status. The Tribal Council could
then allocate hunting opportunity to tribal members and
enforce the quotas . Recovery of the Fremont County
moose population would benefit Indians and non-
Indians alike, and allotment of harvest opportunity to
each group would regulate the harvest and promote a
feeling of cooperative management.
Stiffer penalties are needed to deal with poachers.
The Department should stress the seriousness of the
poaching problem and solicit better public compliance.
The Department has monitored population trends
of Fremont County moose since 1949. I recommend that
trend surveys be continued and also that browse utiliza-
tion and condition trends be monitored . I believe expe-
rienced observers could obtain satisfactory trend data by
censusing at 2 or 3 year intervals under carefully se lected
counting conditions , i.e . during fair weather and within
48 hours of fresh snowfall. This would reduce costs sub-
stantially. Occasional herd composition surveys should
also be made, preferably prior to antler drop . Occasional
Page 29
visual appraisals of forage plant conditions are probably
adequate when moose population densities are as low as
they were on most ranges. When heavy browsing of some
plant species becomes apparent, such as on willow and
aspen on Fall River range, annual browse surveys should
be conducted.
Moose should receive top priority management con-
sideration on mountainous ranges of Fremont County
where heavy snow accumulations virtually eliminate
competition from deer and elk. Clearcut logging of key
forested wintering areas should be on a sustained-yield
basis and roads should be closed following logging. Key
wintering areas should be closed to snowmobile use.
The effect of elk hunting regulations upon the illegal
harvest of moose should be considered when establishing
elk seasons. The number of moose kills incidental to elk
hunting during the study was related to hunter densities.
Moose kills by elk hunters declined substantially after
changes were made in 1974 which dispersed elk hunters
•
•
•
SUMMARY
An ecological study of Shiras moose was conducted
in Fremont County, Idaho, from 1969 to 1976. Moose
may not have been present in southeastern Idaho prior to
1850. Large populations occurred in Fremont County by
1945 and legal hunting was initiated in 1946. The moose
population declined from the early 1950's through mid-
1970's. Observed production averaged 62 calves per 100
cows during this study. Hunting, including legal, illegal
and Indian, caused 79 percent of the observed mortality
and was considered the primary mortality factor. Winters
were above average severity and malnutrition losses
occurred regularly, but the magnitude and impact of
these deaths were not determined. Decline of the popula-
tion during a mild period extending from the mid-1950's
through early 1960's suggests climatic factors were of
secondary importance.
Seasonal movements of five moose populations
were studied. Four were resident to Fremont County, but
moose from the Fall River herd moved into Wyoming
during summer. Moose concentrated in areas providing
good cover and forage during winter and dispersed
widely during summer. Summer home range size of
radioed moose averaged 7.4 and 16 square miles (19.2
and 41.4 km2) for cows and bulls, respectively. Timing of
the fall migration was influenced by snow depths and
usually occurred during November and December.
Foods eaten by moose were determined from analy-
sis of 94 rumen samples and 290 feeding sites. Browse was
the most important forage class used throughout the year.
Page 30
that formerly concentrated in two Fremont County hunt-
ing units. The changes included opening a large block of
units to general bulls-only elk hunting and moving open-
ing day from Saturday to Wednesday. Controlled hunts
or other means of limiting hunter numbers should be uti-
lized where incidental harvest of moose is excessive.
Information about other Idaho moose populations
is limited although the species is widely distributed. If
moose are to be managed as a trophy species, as the one-
per-lifetime harvest restriction implies, data-gathering
effort should be equivalent to that for other trophy
species. Regional Game Managers should have some feel
for moose numbers, key areas, range conditions and mor-
tality causes for populations within their jurisdictions,
particularly where moose hunting is allowed. Poaching
and incidental kill by big game hunters appears to be
higher for moose than other species. I do not know the
solution to the problem, but these factors should be con-
sidered when setting moose harvest quotas.
•
•
Non-woody forage was important during summer and
also during winter in Island Park. Winter diets differed
among winter ranges. Atypical winter diets were
observed on the Junipers and Island Park ranges. The
Junipers moose subsisted on bitterbrush and choke-
cherry and the Island Park moose consumed large quan-
tities of lodgepole pine and aquatic vegetation in addition
to willow.
Utilization and conditions of key forage species were
surveyed on four winter ranges. On timbered sites on the
Fall River range, upland willow and aspen were heavily
browsed and in poor vigor. Serviceberry and choke-
cherry were browsed moderately. Browse utilization was
light to moderate on the other ranges and plants were
generally in good condition.
Seasonal use of vegetation types on the Fall River,
Big Bend and Island Park ranges was determined from
3,292 observations. Lodgepole pine received the highest
use during summer, but moose preferred mixed aspen-
conifer, willow and aquatic habitat during winter.
Forage availability was more important than snow
depth in determining winter moose densities on Fall
River range. Warm River Butte, an area of high snowfall,
had the highest pellet group densities of three areas sur-
veyed. Clearcuts received less use during winter than
adjacent timbered areas even though forage was plenti-
ful. Heavy livestock grazing on willow plants at Henry's
Lake had reduced willow cover and caused reduced use
by wintering moose. Management recommendations
were made from findings of the study.
LITERATURE CITED
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Page 31
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Page 32
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Appendix Table 1. Scientific names of plants listed in this report.
Common Name Scientific Name Common Name Scientific Name
Alpine fir Abies lasiocarpa Mistletoe Arceuthobium spp.
Aspen Populus tremuloides Mountain ash Sorbus scopulina
Big sagebrush Artemesia tridentata Mountain maple Acer glabrum
Bigtooth maple Acer grandidentatum Oregon grape Mahonia repens
Birch Betula spp. Pinegrass Calamagrostis rubescens
Bitter brush Purshia tridentata Rabbitbrush Chrysothamnus nauseosus
Chokecherry Prunus virginiana & C. viscidiflorus
Cinquefoil Potentilla gracilis Red osier dogwood Comus stolonifera
Currant Ribes spp. Riparian willow Salix spp.
Douglas fir Psuedotsuga menzesii Rocky Mountain Juniper Juniperus scopulorum
Engelmann spruce Picea engelmanni Rose Rosa spp.
Fire weed Epilobium angustifolium Sedge Carex spp.
Geranium Geranium spp. Serviceberry Amelanchier alnifolia
Goat's beard Tragopogon spp. Snow berry Symphoricarpos rivularis
Hawthorn Crataegus spp. Snow brush Ceanothus velutinus
Huckleberry Vaccinium spp. Upland willow Salix scouleriana
Juniper Juniperus spp. Watercress Rorippa nasturtium-
Lodgepole pine Pinus contorta aquaticum
Lupine Lupinus spp. Willow Salix spp.
Appendix Table 2. Forage species not shown in Tables 5 and 6 because they comprised less than 5 percent of the diet for
one season or area.
SUMMER
Birch
Chokecherry
Cinquefoil
Currant
Geranium
Goat's beard
Lodgepole pine
Lupine
FALL
Alpine fir
Douglas fir
Huckleberry
Lodgepole pine
Lupine
Oregon Grape
Red osier dogwood
Rose
Serviceberry
Snow berry
WINTER
--------Junipers Herd ---------
Big sagebrush
Rose
Currant
-------Fall River Herd --------
Mountain ash
Snow berry
Mountain maple
------Big Bend Ridge Herd-------
Juniper
Mountain maple
Snow brush
Mountain ash
Rose
------Shotgun Valley Herd-------
Currant
Red osier dogwood
Snow berry
Mountain ash
Rose
-------Island Park Herd--------
Currant Sedge
Page 33
A1