The Bison of Yellowstone National ParkYELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

THE BISON OF
YELLOWSTONENATIONAL PARK
Margaret Mary Meagher
Research Biologist
National Park Service

National Park Service
Scientific Monograph
Number One
1973
TABLE OF CONTENTS

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The Bison of Yellowstone National Park (Table of Contents)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

TABLE OF CONTENTS
COVER
LIST OF FIGURESLIST OF TABLESACKNOWLEDGMENTS
SUMMARY
Chapter 1: INTRODUCTION
Methods
Chapter 2: THE STUDY AREA
Physiography
ClimateVegetation
History
Chapter 3: THE BISON POPULATION
The historic population
Mountain bison
Numbers and distribution through 1902
The present population

   Origins

   Present composition

   Numbers and distribution
Chapter 4: GENERAL CHARACTERISTICS
Physical characteristics

   Appearance   Weight

   Life Span
Behavioral characteristics

   Grouping characteristics

   Behavior and specific circumstances

   Senses and disposition

   Visitor opportunities to see bison

The Bison of Yellowstone National Park (Table of Contents)

Chapter 5: POPULATION CHARACTERISTICS
Sexual maturity
Reproduction rate
Fetal sex ratio
Number of young at birth
Population structure
Calf percentages
Mortality

   Calf Mortality

   Subadult mortality

   Other mortality

   Population trends
Chapter 6: MORTALITY FACTORSParasites

   Internal parasites

   External parasites
Diseases
Predation
Other causes
Chapter 7: HABITS
Calving
Rut
Movements

   Migratory movements

   Summer range movements

   Winter range movements

   Movements beyond park boundaries
Mixing of population segments
Food habits
Chapter 8: HABITAT RELATIONSHIPS
Use of forage areas
Use of thermal areas
Effects on habitat
Chapter 9: SUGGESTED MECHANISMS OF POPULATION REGULATIONAPPENDICESI Common and scientific names of plants
II Summary of bison reports prior to 1903, Yellowstone National Park and vicinity
III Reports of wild bison, 1903-19, Yellowstone National Park
IV Bison population, 1902-68
V Data on fetal sizes compiled from tabulation of late January 1941 (Skinner 1941)
VI Known bison movements to and beyond Yellowstone National Park boundaries, 1942-67
VII Occurrence of grasses and grasslike plants in bison use areas
REFERENCES

The Bison of Yellowstone National Park (Table of Contents)

FIGURES
1 Map of Yellowstone National Park showing study area
2 Aerial view of a part of the forested plateau
3 Springtime view west across lower Lamar Valley
4 Upper Lamar drainage, Absaroka Mountains in background
5 Bison on the Pelican Valley winter range
6 A part of the Hayden Valley winter range
7 Lower Geyser Basin, Firehole winter range, early spring
8 Summer range on the western part of the Pitchstone Plateau
9 Cows and calves, Hayden Valley, sometime before 1894.
10 Skulls of Bison bison athabascae and B. b. bison
11 Map of bison distribution and movements in historic times
12 Bison wintering in Hayden Valley prior to 1894.
13 Buffalo Jones and Army Scout Holt with captured bison calf
14 Clipped appearance of a mature bull.
15 Bison shedding old hair, mid-summer
16 Wisps of shed bison hair on a branch of a lodgepole pine
17 Newly-born calves in a mixed herd group.
18 Calf that has lost its first red-brown pelage.
19 Head shape and size of cow compared with bull
20 Spike-horn bull, approximately 2.5 years old.
21 Spike-horn bull, yearling female, cows, and bull.
22 Horns of adult cow and spike-horn bull compared
23 Old Tex, a record Yellowstone bull
24 Bison population trends from population counts, 1936-68
25 Trench left in soft snow by traveling bison
26 Bull bison foraging in snow approximately 2.5 feet deep
27 Feeding site in snow approximately 2 feet deep
28 Calves a few days old
29 Grassy spot uprooted by bison horning during the rut
30 Map of the Lamar-Pelican area
31 Map of Hayden Valley-Firehole-Madison Plateau area
32 Bison herd groups on Alum Creek, Hayden Valley
33 Bison on the strip of sedge meadows along upper Alum Creek
34 A herd group on the east boundary near Canoe Lake
35 Map showing bison movements across park boundaries
36 Neckbanded bison in a group at Pocket Basin on the Firehole.
37 Population fluctuations in wintering areas caused by shifts
38 Snow-free bison feeding site on warm ground in Firehole
39 The same site shown in Figure 38, in early summer
40 Warm site along Alum Creek in Hayden Valley
41 The same site shown in Figure 40, in summer
42 Bison bull wintering among active geysers and hot springs
43 Aerial view of the Alum Creek winter feeding area.
44 Hot water keeps Firehole River open all winter45 Sedge growth along Firehole River provides winter forage
46 Bison in small thermal area west of Astringent Creek
47 Trees debarked by rubbing bison, Hayden Valley
48 Bison horning effects on a lodgepole pine
49 Bull bison at a wallow which is used year after year
50 A bison trail, Hayden Valley area

The Bison of Yellowstone National Park (Table of Contents)

51 Pelican Valley population numbers, 1902-68

TABLES
1 Vegetation of the study area
2 Summary, native bison information 1860-1915
3 Composition of fenced herd, 1902-15
4 Presumed age and sex composition, fenced herd, 1903-10
5 Presumed age classes of male bison on the range, 1921
6 Distribution of the present population, 1969
7 Comparative distribution of bulls wintering apart from mixed groups
8 Opportunities to see bison from present park roads
9 Number of cows and calves removed during reductions
10 Comparison of female pregnancy rates, by age classes, 1940-41 and 1964-66
11 Summary of reproductive data and fetal sex ratios, 1931-32 through 1964-66
12 Comparison of winter climatic factors in Wood Buffalo and Yellowstone National parks
13 Age classes of bison trapped, reductions of 1964-66
14 Calf percentages of mixed herd numbers in spring
15 Calf percentages of pooled mixed herd numbers throughout the year
16 Comparative summary of movements shown by the present wintering populations
17 Food habits as indicated by rumen sample analysis
18 Presence of factors which may affect suitability of habitat for wintering mixed herd groups
Richard Nixon
President of the United States
Rogers C. B. Morton, Secretary
U.S. Department of the Interior
Ronald H. Walker, Director
National Park Service
As the Nation's principal conservation agency, the Department of the Interior hasbasic responsibilities for water, fish, wildlife, mineral, land, park, andrecreational resources. Indian and Territorial affairs are other major concerns ofAmerica's "Department of Natural Resources." The Department works to assure
the wisest choice in managing all our resources so each will make its fullcontribution to a better United States—now and in the future.
This publication is one a series of research studies devoted to special topics whichhave been explored in connection with the various areas in the National Park
System. It is printed at the Government Printing Office.
Library of Congress Catalog Card Number: 73-600221

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The Bison of Yellowstone National Park (Acknowledgments)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

ACKNOWLEDGMENTS
THIS RESEARCH WAS UNDERTAKEN with the sponsorship of the National Park Service
and the Museum of Vertebrate Zoology, University of California, Berkeley. The research
report, accepted as a doctoral dissertation in 1970 by the University of California, is presented
here with minor modifications.
The project, conducted over a span of 7 years while I was employed as a Park Naturalist by
the National Park Service at Yellowstone National Park, would not have been possible
without the assistance of many people. Among the National Park Service personnel who
contributed, particular appreciation is due John Good, former Chief Park Naturalist, forencouragement and assistance in arranging work requirements to allow time for the study.
Park Rangers Peter Thompson, Dale Nuss, and Gordon Boyd assisted with some of the fieldwork. Biologist Glen Cole contributed ideas and suggestions. Aubrey Haines provided
information on historical sources.
Dave Stradley, Gallatin Flying Service, made possible the quality of the aerial observation
work. Kenneth Greer, Supervisor of the Montana State Fish and Game Department
Laboratory, provided food habits analysis assistance. W. E. Booth, Montana State University,
verified plant identifications. John Ricks, Livingston, Montana, facilitated autopsy work.
Keith Hoofnagle did the maps and graphs.
Financial support was provided by the National Park Service and the Union Foundation
Wildlife Fund, administered by the University of California. The Yellowstone Library andMuseum Association contributed to the reproduction of dissertation copies.
To these people and organizations, and the many other individuals who provided information,encouragement, and assistance—my thanks.
July 1972
MARGARET MARY MEAGHER

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The Bison of Yellowstone National Park (Summary)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

SUMMARYOBJECTIVES OF THIS STUDY were to provide basic data on the life history, habits, andecology of bison in Yellowstone National Park.
The original population of bison in historic times consisted of mountain bison, Bison bison
athabascae. In spite of poaching to near-extermination by about 1901, a remnant of thesubspecies survived and increased. Interbreeding with a population of plains bison, B. b.
bison, introduced in 1902, began by the 1920s. The present bison population consists ofhybrid descendants of the two subspecies.
The present wintering distribution within the park approximates that of the historic population,
occurring in the three subunits of Lamar, Pelican, and Mary Mountain, none of which are
geographically isolated from the others. The present summering population approximates thehistoric distribution only in the Upper Lamar-Mirror Plateau and Hayden Valley areas. A
large west-side and a large northern summering population are lacking. Present (1968)
numbers are half or less than those of probable historic numbers.
Examination of 71 females killed for population reduction purposes indicated that sexual
maturity was not reached by most until 4 years of age, later than recorded some years ago.
The observed pregnancy rate of 52% for females 2.5 years and older was also less thanformerly recorded in Yellowstone. Brucellosis was not a factor which affected reproduction.
Records and observations suggested that both calving season (in May on the winter ranges)
and the breeding season (in late July to early August on the summer ranges) were shorter thanformerly. The observed changes may reflect the shift from a semiranched population to a wildone.
Records from live-trapping operations in 1964-66 provided sex and age structure information.
The records suggested that female survival was favored during the calf year, but that malesurvival was favored the next 3 years of life, after which differential survival could not be
distinguished from the records. Adult bulls outnumbered adult cows, but this could be
attributed to earlier reductions.
Age classes of the wintering population in the Mary Mountain area in 1964-65 were: calves,16%; yearlings, 11%; 2.5-year-olds, 6%; 3.5-year-olds, 5%; and adults, 62%. These may
change somewhat after a period with no reductions.
Observed spring calf percentages of mixed herd numbers for 3 of 5 years were 19-20%.
Percentages of total population were approximately 11%. These percentages may also change
if reductions are not made.
Significant mortality of calves at birth or just before or after was suggested by limited data.
Thereafter, little mortality occurred during the first year. Nearly half the calves whichsurvived into their first winter died before 2.5 years of age. Recruitment into the population
occurred with survival to 3 years of age.

The Bison of Yellowstone National Park (Summary)

Population trends suggested that increases in the population were often very slow. Reductions
by man apparently were not the sole factor which caused population decreases nor retarded
increases. Parasites, diseases, predation, and emigration were not important. Environmental
factors culminating in usual and more-than-usual winter mortality appeared important.
Herd groups followed definite patterns of seasonal movement. Spring migrations to summer
ranges, occurring by the second week of June, appeared to be influenced by weather patterns
and temperatures rather than snow melt or vegetation changes. Temporary fall movements
occurred in conjunction with fall storms at higher elevations; final movements to winterranges occurred by mid-November. Bull movements were somewhat more irregular.
Movements and distribution on summer range areas appeared more influenced by the presenceof biting flies than by possible factors of breeding activity and vegetation changes. A species
of Symphoromyia of the Rhagionidae was implicated.
Mixing and interchange between population subunits resulted in designation of three herds
according to their use of winter range areas. These three subunits formed two breeding
populations in summer. Little contact occurred between members of these two populations at
any time.
The limited neckband information on marked adult cows suggested that they have an affinity
for a given winter range regardless of summer movements. Temporary shifts of population
segments from one winter range to another have occurred. Thus, although no population
segment is isolated from another, the three exist as fairly separate entities in terms of winterrange. This may explain the lack of population emigration to and reestablishment onunoccupied ranges either within or outside the park since historic times.
Analysis of 22 rumen samples showed that sedge was the most important forage item. Sedge,
rush, and grasses provided 96% of the diet volume throughout the year. Forage availability
did not appear to be a population-limiting factor under most conditions.
Population numbers in Pelican over a span of many years suggested that the levels wereregulated by environmental influences which resulted in low reproduction and low increment
rates. Larger increases in numbers during favorable periods have been offset periodically by
heavy mortality during more severe winters. The minimum population level in this area may
be governed by the presence of scattered thermal areas used in winter stress periods. A
combination of factors such as extensive sedge bottoms together with some sagebrushgrassland uplands, open streams, and thermal areas may allow habitation over time by mixed
herd groups of bison in this wintering valley.

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The Bison of Yellowstone National Park (Chapter 1)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 1:

INTRODUCTION
THE BISON OF YELLOWSTONE NATIONAL PARK are unique among bison herds in the
United States, being descendants, in part, of the only continuously wild herd in this country.
They are today a hybrid herd, being a mixture of the plains bison (Bison bison bison
Linnaeus), introduced into Yellowstone National Park in 1902, and mountain or wood bison(Bison bison athabascae Rhoads), which originally inhabited the Yellowstone andsurrounding country. They are a wild population, unrestricted by either internal or boundary
fences, and subject to minimal interference by man.
Although members of a species which nearly became extinct, and a species of great historicalinterest, Yellowstone's bison have not been objects of extensive research. McHugh (1958)
studied behavior of bison in Yellowstone. Rush (1932a), Tunnicliff and Marsh (1935), andLocker (1953) published information on parasites and disease. Cahalane (1944) summarized
the history of the introduced herd and management practices as of that date.
The present study was begun in 1963 to provide basic data on the life history, habits, andecology of bison in the park. This study report, based on extensive field work andsupplemented by an intensive search for historical information, provides a basis for
management and for evaluation of the importance of this particular bison population. As asource of interpretive information for the many people who visit the park, the report may
make the bison less of a myth, but a far more interesting reality.

Methods
Information on numbers, composition of groups, distribution, and habits was obtained byusing fixed-wing aircraft and helicopter flights, horse and ski travel, and limited vehicle use.
No set pattern of route and interval was established; work was scheduled according to season,
general animal location, and distances involved. Time of day was generally not a factor. A
monocular and a variable-power spotting scope were used for observation.
Age and sex information was compiled at herd-reduction operations at Lamar in the northeast
quarter (Crystal trap) and on the Firehole River nearly 35 miles southwest of Lamar (Nez
Perce trap) during the winters of 1964-65 and 1965-66. Reductions have been held in the parkat intervals since 1932, primarily to keep the bison population at numbers suggested by range
condition reports and surveys (Rush 1932b; Grimm 1939; Kittams 1947-58, 1949; Soil
Conservation Service 1963, 1964). For reductions after 1960, animals have usually been
driven into the two above-mentioned large live traps by coordinated herding efforts of two
helicopters. Squeeze chutes permitted handling of most individuals, after which the bison
were released or were trucked to a local slaughterhouse. Animals were selected for slaughteron the basis of brucellosis infection. Uninfected animals were also taken to fill removal
quotas. All animals were permanently metal eartagged during brucellosis testing, and marked

The Bison of Yellowstone National Park (Chapter 1)

with temporary backtags, which were visible even from an airplane. Most were aged by
Department of Agriculture veterinarians and weighed.
During both winters, some released animals were marked with color-coded neckbands for area
and individual recognition, and for the year of banding. Animals—preferably females,
yearlings and older—were chosen a few at a time on different trap days to distribute marked
animals among released groups as much as possible. Forty-four individuals (30 of themfemales) were neckbanded, half at each trap. Seventeen females and two males were young
adults and older. Half of the neckbands were lost during the first year. More males thanfemales lost neckbands. Attempts to neckband animals through use of field immobilization
techniques were not satisfactory.
During slaughter operations, approximately 47% of the animals removed from the park were
examined for pregnancy, abnormalities, and evidence of injury or disease other thanbrucellosis. Reproductive tracts could not be examined, nor fetal sex ratios determinedbecause approximately half of removed animals had brucellosis or were suspect. Departmentof Agriculture veterinarians advised against examination of reproductive organs, where the
Brucella organism most often localizes, to avoid contamination of slaughterhouse premises
and exposure of personnel to the disease. Lower jaws were collected for age verification using
the techniques of Fuller (1959).
Food-habit information came from analysis of 22 rumen samples collected from animals shotin the park at all seasons and in various locations. Percent composition of samples wasdetermined by volume after separation and identification of materials. The analyses were
supplemented by general field observations of animal feeding behavior.

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The Bison of Yellowstone National Park (Chapter 2)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 2:

THE STUDY AREA
THE STUDY AREA INCLUDED all parts of Yellowstone National Park regularly used by
the bison population, or frequented by them in the past 20-25 years (Fig. 1). The occupiedbison range covers nearly half of Yellowstone's 3472 square miles, extending diagonallyacross the park from the northeast quarter to the southwest quarter. Some phases of study
effort were emphasized in the northeast quarter. Lands outside the boundaries are not used toany extent by the park bison, and hence were not part of the study area, but they are discussed
where pertinent to historical populations.

Fig. 1. Map of Yellowstone National Park showing study area.

Physiography

The Bison of Yellowstone National Park (Chapter 2)

Much of the park is plateau-like, varying in elevation from about 7000 to 8000 feet, and cut bylarge and small stream valleys (Fig. 2). Mountains project above the general level on all sides,
but are less extensive in the interior. The Continental Divide traverses the park from west to
southeast, generally unmarked by abrupt changes in terrain. Most of the study area lies east of
the divide, and is drained by the headwaters of the Madison and Yellowstone rivers.
Tributaries of the Snake River drain the southwestern corner.

Fig. 2. Aerial view of a part of the forested plateau, located centrally.

Park geology is discussed by Hague (1809), whose work was followed by numerous topicalstudies. U.S. Geological Survey personnel are now completing a comprehensive research
program which will add much to present knowledge of the complex geologic history of
Yellowstone. Extensive volcanism, of which the widely distributed thermal activity is aremnant stage, has shaped many of the physiographic features. Effects of glaciers, which may
have persisted as recently as 8000 years ago, are evident throughout the park.
The study area was subdivided into nine regions. From northeast to southwest these are:
Lamar, Upper Lamar, Mirror Plateau, Pelican, Hayden Valley, Firehole, Madison Plateau,
Pitchstone Plateau, and Bechler (Fig. 1). The Lamar (Fig. 3), at approximately 6400 feet,includes lower Hellroaring and Slough creeks, the main Lamar River Valley below Soda
Butte Creek, the north-facing lower slopes of Specimen Ridge, and the Soda Butte area. The
Upper Lamar refers to the Lamar River above Soda Butte Creek, together with the ridges andtributaries rising eastward to the Absaroka Mountains, at more than 10,000 feet (Fig. 4). The
Mirror Plateau, including much of Specimen Ridge, lies between the Lamar River to the northand east, the Yellowstone River to the west, and Pelican Valley to the south. Pelican Valley(Fig. 5), at 7800 feet, refers to the main valley from the lowest portions of Raven Creek to themouth of Pelican Creek and includes Mary Bay on Yellowstone Lake. Hayden Valley,elevation 7700 feet, is centrally located in the park (Fig. 6). It extends from the Grand Canyonof the Yellowstone south to the Mud Volcano, west to Mary Mountain, and includes Beachand Dryad lakes to the south and Cygnet Lakes to the north. The Firehole, at 7200 feet, refers

The Bison of Yellowstone National Park (Chapter 2)

to all three major geyser basins along that river, together with Nez Perce, Spruce, Sentinel,and Fairy creeks (Fig. 7). West of the Firehole, the Madison Plateau rises gradually to theContinental Divide and extends to the Bechler Meadows. The Pitchstone Plateau (Fig. 8) lies
southeast of the Madison Plateau. The Bechler Meadows, at 6400 feet, are comparable to theLamar in elevation.

Fig. 3. Springtime view west across part of the bison winter use area of the lower
Lamar Valley.

Fig. 4. The upper Lamar drainage with the edge of the Mirror Plateau to the right, apart of the Absaroka Mountains in the background.

The Bison of Yellowstone National Park (Chapter 2)

Fig. 5. Bison on the Pelican Valley winter range.

Fig. 6. A part of the Hayden Valley winter range with Alum Creek in the foreground.

The Bison of Yellowstone National Park (Chapter 2)

Fig. 7. The Lower Geyser Basin area of the Firehole winter range in early spring.

Soils vary greatly. Generally, there are deep silts in the bottoms of the big valleys. Morainal
materials are especially prominent in Lamar. Lake deposits of clays and sands are found in
Pelican and Hayden valleys. Higher areas commonly have shallow, poorly developed soils
derived from volcanic parent material interspersed with alluvial sites.

ClimateThroughout the area winters are long and cold, with short cool summers. The U.S. Departmentof Commerce Weather Bureau (1930-59) summary for Yellowstone National Park indicatedfor the headquarters' station at Mammoth, near the north boundary, a mean annual
temperature of 39.8°F. January, the coldest month, averaged 18.0°F; July, with a mean of
62.8°F, was the warmest. Temperatures at this station average about 5°F higher than those formost of the park.
The same summary indicated that average annual precipitation in the study area varied from13.73 inches at Lamar to 38.26 inches at Bechler. Near Pelican, the annual average was 19.00
inches. Most precipitation occurred as snow. For most of the park, between the 7000- and
8500-foot levels, the average snowfall was about 150 inches, with Lamar averaging 85-95
inches, and Lake, near Pelican, averaging 146 inches. For a 50-year period at Lake, a range insnowfall of 81-270 inches is recorded. Actual depth on the ground at Lake, as recorded bysnow survey measurements (U.S. Department of Agriculture—Soil Conservation Service,
1919-67), averaged about 19 inches for 1 January and about 35 inches by 1 April. Lamarwould usually have somewhat less; Bechler, somewhat more. Crusting conditions, for which
no record is available, varied considerably.
Seasons of the year vary with location and altitude. Warm sites near thermal activity are snowfree earlier and have a longer growing season than surrounding areas. Winter extended frommid-November to mid-April in all areas of the study. Spring began in mid-April in Lamar, in
mid-May in the higher valleys, and on 1 July at the highest elevations. Summer began 1 Julyin the valleys, late July in the mountains. Killing frosts are usual in most locations before theend of August, so fall extended from 1 September to mid-November in all areas. At higher
elevations, snow depth was often considerable by early November.

The Bison of Yellowstone National Park (Chapter 2)

Vegetation
Vegetation types were not mapped for purposes of this study. Figure 1 indicates the extent of
the larger meadows within the forested parts of the study area. More detail is apparent in Figs.
30 and 31, which show subunits of the study area. Major species of plants, according to site,
are listed in Table 1. General descriptions of park vegetation are provided by Bailey (1930),
Bailey and Bailey (1949), and McDougall and Baggley (1956). Common and scientific names
used are listed in Appendix I. These follow Booth (1950) or Booth and Wright (1959).

Fig. 8. Summer range on the western part of the Pitchstone Plateau.

The large, open valleys of Lamar, Pelican, Hayden, and Firehole have dense sedge growthbordering the streams and extending across the flat bottoms. The slightly higher slopes andlevels support bunchgrasses, forbs, and sagebrush, with scattered marshy swale areas. Shrubs,
except sagebrush, are of limited extent generally in these valleys. In Lamar, willow was
grubbed out in some places to increase the area of pasture and hay land during early Buffalo
Ranch operations. Extensive grassland and sagebrush areas on high slopes and ridges are
particularly common in the northeast quarter, although patches of more lush herbaceous
vegetation are frequent.
Much of the study area is forested, predominantly by lodgepole pine, which varies from dense,even-age growth with little understory to open stands with considerable sedge and grass.
Dense shrubby undergrowth is usually not extensive. Down timber is common. At higher
elevations, Engelmann spruce and alpine fir replace the lodgepole. Whitebark pine is found insome locations. Meadows are scattered throughout the forest on moist sites along streams andaround ponds, and appear as small openings in drier locations. Particularly on the Mirror
Plateau, boggy side hills with dense sedge growth are numerous.
On the upper plateau levels and mountain slopes, subalpine meadows are found. Above these,at the highest elevations, alpine vegetation occurs to a limited extent.

History
Yellowstone National Park was established in 1872, before the surrounding area became thestates of Idaho, Montana, and Wyoming. Boundary changes, made twice, added small areas toThe Bison of Yellowstone National Park (Chapter 2)

the original rectangle and altered the east boundary in 1929 to conform for most of its length
to the drainage divide formed by the Absaroka Mountains. Most of the land adjacent to theboundary is administered by the U.S. Forest Service.
Haines (1963) summarizes the history of man's occupation of the Yellowstone Plateau.
Prehistoric hunters and gatherers used the area extensively. Members of several tribes ofmodern Indians were primarily summer hunters, although a few sheep-eaters lived a marginalexistence throughout the year. Hostile Indians did not travel the park after the Bannock War
of 1878, but hunting parties from reservations were known at the park fringes as late as 1893
(Hough 1894). Although few left written accounts, trappers, beginning with John Colter in
1807, visited the area many times before the end of the fur trade in 1840. Miners andexplorers followed.
TABLE I. Vegetation of the study area.

Vegetation
General distribution
type

Characteristic Associatedvegetation
plantsMarsh

TuftedHairgrassSedge
SedgeBluegrass

Alluvial soils along watercourses, swale areas

Sagebrush- Glacial outwash areas, alluvial fans, lacustrine
Grassland
deposits

Rush
ShrubbyCinquefoil

Wheatgrass
LupineIdaho
FescueBig Sagebrush
Eriogonum
Balsamroot
DrylandSedgesUplandVarious substrates and exposures up to 10,000 ft. Lodgepole
Dwarf
ForestPine
Huckleberry
Engelmann
SpruceArnica
Subalpine Fir
LupineWhitebarkPinegrass
Pine
Forest Park Alluvial soils along watercourses, old ponds, small Sedge-Tufted
openings on drier slopes
HairgrassRush
Idaho FescueDandelion
Wheatgrass
LupineMountainCinquefoil
BromeBluegrass
Slender
Wheatgrass
LupineHerblandFine-textured residual soils of Mountain mountain
Cinquefoil
slopes from about 8000 to 9500 ft.
Mountain
Geranium
BromeBluegrass
Slender

The Bison of Yellowstone National Park (Chapter 2)

Wheatgrass
Subalpine
Meadow

Mountain slopes and ridgetops, mainly above 8500
Tuftedft.
HairgrassSedge

Needlegrass
Rush
Rush
Bluegrass
Wild
BarleyThe park was not subject to settlement, and there were few people for some years after its
establishment. With the exception of a few early squatters, developments were foradministrative use or concessioner operation. In conjunction with these, horses and cattle
were grazed in some places, and wild hay was cut. Disturbance was generally minimal except
in the Lamar area. Skinner and Alcorn (1942-51) summarize the Buffalo Ranch-Lamar
Ranger Station operations of Lamar and Slough Creek valleys from 1907 through 1951.
Seeding and irrigation practices were part of the haying program, as well as construction ofbuildings, fences, and other necessities of a ranch.
During the early years of the park, wildlife had little protection. The Act establishing
Yellowstone National Park provided only that wildlife should not be "wantonly destroyed"
nor subject to "capture and destruction for the purposes of merchandise or profit." Until 1887
official regulations permitted hunting while traveling in the park. Legal means for enforcing
regulations were lacking, although the Army troops stationed in the park after 1886 did what
they could. Attempts at protection had limited effect until passage of the Lacey Act in 1894
provided legal machinery and jurisdictional authority for dealing with violators. Outside thepark, ineffective laws contributed to poaching within the boundaries.
Not until 1901 did the Superintendent of the park believe the laws of all three surrounding
states were such that the wild bison left in Yellowstone might be effectively protected, but
their numbers were so few that survival seemed doubtful. Intensive management of an
introduced herd began in 1902 to ensure survival of some bison in Yellowstone. For a time
the animals lived in semidomestication, and were fed hay and tended almost like a herd ofcattle. Management policy gradually changed to one of minimal interference by man, which
continues in spite of the impact of steadily increasing numbers of tourists. The present (1970)
bison population is completely wild and unfettered by fencing or artificial management.

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The Bison of Yellowstone National Park (Chapter 3)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 3:

THE BISON POPULATIONThe Historic Population
THE GENUS Bison PROBABLY INVADED North America during the later part of the early Pleistocene.
The bison occupying the continent in historic times were descendants of a second migration of Bison from
Eurasia, which crossed the Bering Straits at the start of the late Pleistocene according to Skinner and Kaisen(1947). Of the invading species, only one persisted to give rise to B. occidentalis, the ancestor of B. bison, themodern form. Two subspecies, B. b. bison and B. b. athabascae, are recognized by cranial evidence, although
historical accounts suggest there may have been others (Roe 1951). The form athabascae is apparently themore primitive of the two subspecies (Skinner and Kaisen 1947).
Just when bison first reached the Yellowstone plateau is not known, but modern bison inhabited the area
before historic times, perhaps before the most recent period of intermountain glaciation. Bone fragments frombulls, cows, and calves (B. bison) were found near the edge of a glacier northeast o Yellowstone National
Park (Pattie and Verbeek 1967). In 1964 a fossil cranium (B. b. athabascae) was found embedded in a natural
oil seep on the Mirror Plateau in the park.
The Yellowstone bison of historic times were a remnant of a once much more extensive bison population,
known to trappers and Indians, which inhabited the mountain ranges and the intermountain valleys of theRockies and extended on west into Washington and Oregon. Most of these bison were gone by the 1840s(Aubrey Haines 1968 pers. comm.). According to the distribution map of Skinner and Kaisen (1947), thesewere mountain bison. Considerable numbers of bison once lived close to the park. Many skulls have beenfound in the Red Rock Lakes area, approximately 35 miles west of Yellowstone (Owen Vivion 1968 pers.
comm.) Frank Childs, former Yellowstone ranger who worked on Red Rocks land acquisition matters during
the mid-1930s, heard that 300 bison died there during a bad winter many years earlier (1965 pers. comm.).
Many skulls have also been taken from the Mud Lake area of Idaho, approximately 55 miles southwest of
Yellowstone (Richard Wilson 1968 pers. comm.). Osborne Russell, writing in 1835, mentions the large
numbers of buffalo (bison) seen in both the Red Rock and Mud Lake areas (Haines 1955). Doane (1876)
comments that "buffalo skulls are strewn by thousands —" in the Yellowstone valley about 40 miles north ofthe park. Accounts of wild bison adjacent to and within the park, dating from 1860 through 1902 (Appendix
II), leave no doubt that substantial numbers of bison inhabited the Yellowstone Plateau at all seasons, andlong before the killing of the northern herd of Great Plains bison in the early 1880s.
A misconception of some writers — that Yellowstone's bison of historic times were displaced survivors fromthe Great Plains slaughter — probably stems from: (1) the lack of recognition of two subspecies of Bisonbison; and (2) the impression that early explorers found little "game" in the Rocky Mountains. Three factors
contribute to the idea that bison were sparse in the mountains. Compared to the abundance of certain large
mammals on the plains, the mountains probably seemed almost uninhabited. Secondly, travel routes followed
river valleys and drainages, crossing small areas of high summer range at few locations, often at a season
when biting insects may have driven the game from the lower elevations of passes to adjacent higher slopes
and ridges. Finally, the few early travelers who wrote of their journeys, including official government parties,

The Bison of Yellowstone National Park (Chapter 3)

often commented only on wildlife which was actually sought out or shot for food.

Mountain Bison
The existence of mountain bison, different in appearance and behavior from the plains type and gone frommuch of their range by the 1840s, has generally been little known. Christman (1971) reviews historicalevidence for the subspecies, their distribution to the west of the plains type, and reasons for their early
disappearance. He believes the Indians' acquisition of the horse was the factor underlying the extermination ofmountain bison from extensive areas of original range, particularly in Washington, Oregon, and Idaho.
Many early references to Yellowstone bison use the term "wood" or more commonly "mountain" bison or
buffalo (Fig. 9); some of the characteristics of the race were recognized by a number of early travelers andobservers. Historical accounts generally agree that, compared with the plains bison, these mountain animals
were more hardy, fleet, and wary, and had darker, finer, curlier hair. Sex and age differences among animals
seen may account for discrepancies in description of size. The geologist Arnold Hague (1893) provides thefollowing:

Fig. 9. Cows and calves photographed in a remote part of Hayden Valley sometime
before 1894. These bison were frequently called mountain bison by early observers.
Photo by John Folsom, a winterkeeper at Canyon.

The Park buffalo may all be classed under the head of mountain buffalo and even in this elevatedregion they live for the greater part of the year in the timber. . . .most unusual, save in midwinter,to find them in open valley or on the treeless mountain slope. They haunt the most inaccessible
and out-of-the-way places, . . . living in open glades and pastures, the oases of the dense forest, . .
. the rapidity of their disappearance on being alarmed. It is surprising how few buffalo have been
seen in midsummer, even by those most familiar with their haunts and habits. They wander about
in small bands. . . .
Blackmore (1872) was informed that the mountain buffalo congregated usually in bands of 5-30, rarely more.
Other observers agree that the bands were small, and the animals quite wary. Superintendent Norris described
them as "most keen of scent and difficult of approach of all mountain animals" (Superintendent of the
Yellowstone National Park 1880).
Altitudinal migrations were another characteristic of mountain bison (Christman 1971). Historical accounts

The Bison of Yellowstone National Park (Chapter 3)

from Yellowstone also suggest this habit. Superintendent Norris, in his annual report of 1880, describes
summer and winter distributions of bison in the park, stating clearly:. . . summer in the valleys of the Crevice, Hellroaring, and Slough Creeks, and the mountain spurs
between them, descending with the increasing snows, to winter . . . East Fork [Lamar]. . . . and as
the snows melt . . . returning to their old haunts.
The historical accounts of dates and locations of bison (Appendix II) collectively also show a repetitive patternof seasonal bison distribution which reflects altitudinal movements.
Historical accounts recognizing a mountain buffalo are supported by limited cranial evidence. Skinner andKaisen (1947) show an overlap in general distribution between mountain and plains bison along the east
slopes of the Rockies, including Yellowstone, but state that ranges for historic times must be based on earlyaccounts plus occasional bones or crania. Seven skulls from Yellowstone's original wild herd were picked up
on the ground along the Gardner River and at Mammoth in 1902. All had weathered surfaces. These wereconsidered as most likely representing athabascae. The 1964 skull (Fig. 10) found on the Mirror Plateau was
identified by Skinner (1965) as "an exceptionally long horned, apparently young Mountain bison = B. (B) b.
athabascae No Yellowstone skulls which predate the 1902 introduction have been identified as plains type.

Fig. 10. Skulls of Bison bison athabascae (left) and B. b. bison from the Mirror
Plateau, Yellowstone National Park. Photo by David Love, U.S. Geological Survey.

Numbers and Distribution through 1902
Numbers and distributions from the historical accounts of Appendix II are shown in Table 2. Norris(Superintendent of the Yellowstone National Park 1880) estimated a total of 600, dividing the population into
three herds according to area. By this date, poaching had certainly begun inside the park, along withincreasing pressure on an ever-shrinking mountain bison population outside. Numbers in a given areafluctuated then as now. After consideration of all the listed reports of numbers and distribution, the historical
population, ranging in part beyond the park boundaries, is estimated to have been perhaps 1000 animals. This
seems reasonable when bison habits and behavior and difficulties of making counts are all considered.
Subestimates by area and season are at the bottom of Table 2. They are made to provide a reference point andmust be considered educated guesses.

The Bison of Yellowstone National Park (Chapter 3)

Table 2 also shows the decline of the population to an actual count of 23 in 1902. Again—considering habits,
behavior, and census difficulties—the population probably was higher; perhaps 40-50 mountain bison
survived. The near-extinction in about 25 years was the result, initially, of sport and table hunting on bothsides of the park boundary, plus market hunting, particularly in the Lamar, by both the park hotel construction
crews and the Cooke City miners. The capture of calves by local ranchers interested in starting private herds
was probably most prevalent in Lamar and the west-side wintering areas. Finally, as bison everywhere vergedon extinction, the price paid for heads, plus the minor penalties if caught, attracted poachers who killed allages and both sexes in the wintering areas. Known losses as listed do not reflect the extent of the kill.
Although the Howell poaching case resulted in passage of the Lacey Act in 1894, the population declined
further as poaching, primarily from the west side, continued. Natural losses, coupled with scattering of the
few remaining animals, left a minimal breeding population in the most remote places of the Pelican-MirrorUpper Lamar country.
The distribution, to the extent known, of the original population was similar to the present distribution, butlarger numbers used certain areas more extensively and ranged beyond the park boundaries part of the time.
Figure 11 shows the probable general distribution and population movements of mixed herd groups. The term
"mixed group," as in Fuller (1960), is used here also for groups which usually contain some mature bulls aswell as cows and young. Four areas of summer range and five of winter range are indicated. In two locations
the population probably moved across present boundary lines in numbers.
TABLE 2. Summary, native bison information, 1860-1915.

Year

MirrorNorthWest ofHayden Pelican Upper LamarofaFirehole Firehole Valley Valley Lamar Valley Lamar

1860

one bandb

1863

many trails

186-

Location
Official
notKnown estimate
Other statedlosses(total)

herd

1870

numerous
sign

1871

trackssome

1872

thousands

herdgroups7 calves
captured1875

abundant

1877

scoreshunted300-400

1878

signs

1880

300

1881

100
small
band

1883

small
band

200
some
400; oneband

presumed

1884

180

1885
90 estim.

600

40

markethunting
7 tourist
hunting

200

markethuntingpoaching
20 tourist
hunting

200-300

The Bison of Yellowstone National Park (Chapter 3)

1886

decrease inmarkethunting

54
1887

much
scattered

1888

40-80

9-10

20-30

100

200

increasing
100

1889
some

abundant
fresh
sign

1890

1891

small
band,
largergroups—winter60 + 12 15 calves,sing. &
othersmallgroups

1892
300
1893

50-60 inc.
13 calves

1894
1895

some

6+7

30

1896
presumed
1897

poaching
implied 2
calvescaptured400; 20%
calvessign 51+5

sign 3;sign 2;
1+5
sign 5-6
sign 4; 1
sign 21
+2

200
150

3 calves
3 + 4 + 10 west sidepoaching

200

sign 2

24-50

some

1899
5+1

a few inc. 24
calves45-50

10 est. west
3 + 12 + 3
side
25-50
sign 9poaching

presumed

sign 201898

increasing
200-400

seen often 12 poached 400
103100(rumor)poaching

20

2+4+3
+ 15

1900

50
1Thorofare
2-SnakeR.
29

1 calf50 +poaching
implied

39

1901
1902

25
1

22

1903
16 adults
3 calves
19 adults—winter
1904

25
2 malecalvescapturedfor
introduced
herd
1 femaleThe Bison of Yellowstone National Park (Chapter 3)

2

1905
1907

sign 6

4

1908

calf
capturedfor
introduced
her, 4 Ad. 1
Yrlg.

11 (5
12
female 6(summer)male)

2 adults
male

30

30

sign 15

25

20
maximumincreasing

1909
sign

1910
1911
1912

8

23 + signspring,summer

29 max.

5 + sign

1 male calf
capturedfor
introduced
herd

27 inc. 2
sign 1calves48 inc. 10
calves1 male1913

49
thriving

53

increasing

1914

considerable
increasing
numbers

1915

Estimate ofHistoric
Population,
WinterEstimate ofHistoric
300
Population,
Summer31 (5males, 6yrlg., 4calves
inc.)
some

300

200

200

aPrimarily Madison-Pitchstone Plateaus.
bJust outside the West boundary.

200-300

300-400

400

The Bison of Yellowstone National Park (Chapter 3)

Fig. 11. Map of general distribution and movements of bison mixed herd groups inhistoric times.

From northeast to southwest, the four areas of historic summer range were: north of Lamar, Upper LamarMirror Plateau, Hayden Valley, and Madison-Pitchstone plateaus. Large numbers of bison apparently ranged
at least three of the four areas. North of Lamar, the summering herds of the northern part of the Absaroka
Range split south to the Lamar Valley and north beyond the park to other valleys to winter. On the west side,
the greater part of the summering herds of the Madison-Pitchstone plateaus probably moved southwest
beyond the park toward the east end of the Snake River plains (Mud Lake area) as Norris presumed(Superintendent of the Yellowstone National Park 1880). Historically, as now, the Upper Lamar-Mirror
Plateau was used extensively. The importance of Hayden Valley as historic summer range is less clear. Someof the bison which wintered in Hayden Valley apparently moved west to the Madison Plateau in summer.
People, traveling perhaps when the bands were south of the main valley in the forested areas, may rarely haveseen a group. Hague's (1893) reference to the borders of Elephant Back (south of Hayden Valley) as summer
range suggests that bison did regularly summer in the area. Perhaps it was the least important summer range.

The Bison of Yellowstone National Park (Chapter 3)

Large numbers of bison regularly wintered in Lamar, Pelican, and Hayden valleys (Fig. 12). The Fireholeseems to have been less important. Snow conditions common in the Bechler Meadows make it unlikely thatlarge numbers habitually wintered there, but certainly small groups must have since calves were captured
there in early spring (Murri 1968).

Fig. 12. Bison wintering in Hayden Valley prior to 1894. Photo probably by John
Folsom, early Canyon winterkeeper.

Historical reports do not indicate groups along the Madison and Gallatin rivers to the northwest, within thepark, but Raynolds (1867), while crossing from Henry's Lake to the Madison River, just west of the park, in1860 reported bison "among the hills, . . ." Small groups of bison, also unreported, may have used the large
grasslands just north of the Madison River (south of Cougar Creek) as they did in the 1950s.
Knowledge of travel routes used by people during the early days of the park, which probably followed main
game trails, suggests relative game population numbers, locations, and movements (Fig. 11).
Hague (1893) mentions the lack of buffalo trails, but he was comparing Yellowstone to the plains. Definite
buffalo trails did exist (DeLacy 1876). Norris' (Superintendent of the Yellowstone National Park 1880) map
shows a trail northeast across the Mirror Plateau which follows the route of present buffalo trails. The usual
Pelican-Upper Lamar route (in part an elk trail) once crossed Lovely Pass between Raven and Mist creeks(Superintendent of the Yellowstone National Park 1897). Movement of bison across the Mary Mountain route
between Hayden Valley and the Firehole, commonly used by people prior to construction of a road along
Yellowstone Lake, was implied by earlier writers, and stated as fact by Hough in 1894. Routes in use bypatrols on the Madison Plateau further support early reports of size and distribution of a large west-side
summering population which may have extended north across the Madison River.
Finally, scattered individuals, probably bulls, must occasionally, then as now, have been found in peripheral
areas. Although early reports of live bison are lacking, some animals must surely have inhabited places in thenorthwest quarter of the park outside the known or presumed distribution of herd groups. In the southeast,
Holt (1899) recorded a buffalo in the Thorofare area. A skull from Two Ocean Pass (Fryxell 1926) just southof the boundary, found before 1925, presumably belonged to another such individual.

chap3.htm
Last Updated: 24-Jan-2005

The Bison of Yellowstone National Park (Chapter 3)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 3:

THE BISON POPULATION (continued)
The Present Population
Origins
As stated previously, the Yellowstone bison of the present derive from two subspecies: plainsbison from Montana (Pablo-Allard herd) and Texas (Goodnight herd), introduced in 1902,
and a remnant of the original wild population of mountain bison. Skinner and Alcorn (194251) summarize the introduction, numbers, and subsequent management practices pertaining to
the introduced herd at the Buffalo Ranch in Lamar. Population numbers are from that source
and other official reports. Skinner also provides a resumé of official information concerning
the wild bison, but does not attempt to evaluate the question of their survival. Information
scattered in the diaries, reports, and correspondence of park personnel (Yellowstone National
Park Archives) provides the basis for the following.
Before 1915, introduced bison of plains stock could not have escaped to form a wild group.
The introduced herd was in a small fenced pasture at Mammoth from 1902 until moved to the
Buffalo Ranch at Lamar in 1907. From 1907 until at least 1915, these animals were closely
day-herded, and apparently put in a fenced pasture at night. Although one plains bull from thefenced herd was turned out in 1903, and one or two stray bulls were mentioned later in scout
reports, these apparently never joined the wild bison. Twenty bulls from the Buffalo Ranch
were driven 14 miles up the Lamar River in 1914; these all returned.
Members of two other small groups of semidomestic bison, those of the Yellowstone Lake
Boat Co. and some from Henry's Lake west of the park, never mixed with the wild herd
(Appendix III).
In spite of very low numbers and a pessimistic outlook, the original wild herd did persist, andgradually increased once protection from poaching was assured. The critical survival period
extended from 1902 until about 1920; thereafter, groups of bison which did not frequent the
Buffalo Ranch were more common. These probably contained escapees from the introduced
herd as well as native animals. Table 2, from sources listed in Appendix III, shows dates,
locations, and numbers for the wild herd from 1903-15. Later official estimates of wild herd
numbers are not used, since there was some possibility of wild and introduced animals
intermingling after 1915. The table shows clearly the presence of a remnant wild herd in
Pelican Valley in winter, and on the Mirror Plateau in summer, as well as a few individuals
elsewhere. There was a steady increase, indicated both by calves and by total bison seen. The
known population more than doubled between 1903 and 1912. An actual count was difficult,as Nowlin (1912) of the Biological Survey found: "I have never seen buffaloes on the range
so wary and difficult to locate as the wild ones in the Yellowstone Park."

The Bison of Yellowstone National Park (Chapter 3)

Official population estimates of the time did not allow for more animals than were actuallyseen; they were undoubtedly conservative. By 1912, as Nowlin's classification of 35 animals
shows, the survival of calves (8) and yearlings (7) was encouraging, and the potential forincrease (13 females) was apparent. By 1915, the population may have been nearing 100.
Known mortality is shown only in 1904. While winter loss probably occurred during otheryears, the death of many animals would surely have been observed and reported by Army
patrols or scouts.
Present composition
An estimate of the contribution of the two subspecies to the present population gene pool is, atbest, rough but is preferable to having none. Table 3 shows the sex and adult-calf compositionof the fenced herd from 1902 through 1915. The addition to this herd of four calves captured
by Army scouts (Fig. 13) from the wild herd for the purpose of adding a second bloodline isalso shown. From these numbers, Table 4 was compiled to show the age classes according tosex. The bulls 4 years and older were assumed to have done the breeding in this fenced
situation, although younger bulls may have been physically capable. Females were assumed
to breed as 2-year-olds and to calve at 3. From these assumptions and the tables, the wild
strain in the fenced group was estimated at a maximum of 10% by 1910. Further dilution of
the wild strain in the fenced herd was assumed until perhaps 1917.

Fig. 13. Buffalo Jones and Army Scout Holt with a captured bison calf on a sled.
Photo from Yellowstone National Park files.

TABLE 3. Composition of fenced herd, 1902-15

Year

Males
yrlg &
other

Femalesyrlg &
over Total

1902 31903 21904 61905 12a

18
18
20

21
20
26

27a

1906 15aMale
calvesFemalecalvesTotal
calves

Herd
total

39a

2 + 2 wild 3
6
6 + 1 wild
2
3a

7
13
5

21
27
39
44

29a

44a

9a

4a

13

57

1907 22a

32a

54a

3a

2a

5

59

a

a

a

a

Show
herdb

The Bison of Yellowstone National Park (Chapter 3)

1908 2534

59

1909 30a42a

72a1910 4151

92a

1911 56a

56a
61

112a

1912 58
1913 66a1914 7766a
82

1915 94a96

7
13 + 1
wild
19

14

73

9

23

96

14

9

28

120

16

29

141

15

119a 14132a 15

10

24

143

yes

15

30

162

yes

159a 20190a 28

15

35

194

16 + 20

21

49

239

yes

aCalculated.
bShow herd is included in herd total.

Sometime between 1915 and 1920, intermingling of the introduced and wild animals began.
At first this was probably gradual. Park records do not show the specific year, but after 1915
the close herding practices in use with the introduced herd were abandoned, and the animals
were kept on open range all summer. Close account was kept of most of them for several
more years, but there were some escapees. After 1921, with construction of a log drift fence
across the Lamar Valley above Soda Butte Creek, deliberate efforts were made to keep the
introduced herd on the higher summer ranges, where intermingling with the wild bison musthave quickly increased.
After intermingling of wild and introduced animals began, several factors tended to increase
the wild strain in the total population, although the plains type outnumbered the wild roughly
3:1 about 1917, and perhaps 4:1 in 1921. The number of males in the introduced herd was
reduced by the yearly segregation of a show herd of bulls beginning in 1909. Additional bulls
were removed by live shipment and slaughter. To further reduce the male surplus (from aranch operation viewpoint), castration of bull calves averaged slightly over 50% from 1916
through 1931. As a result, the number of aggressive, dominant plains-type bulls with theintermingled groups would have been considerably decreased.
Table 5 shows the presumed numbers of freeranging males in various age classes for both wild
and introduced herds in 1921. An estimated 40% of the bulls older than 5 years were of themountain bison strain. Their contribution to the breeding activity may have been larger, as
discussed above, than their numbers indicate.
The trend toward increased mountain bison strain would have continued during the 1920s. On
this basis, a reasonable estimate of wild strain in the present bison population would seem tobe 30-40%.
Numbers and distribution
Management practices for many years made little attempt to re-create a natural, wild bison
population in the park. Efforts concentrated on ensuring bison in numbers sufficient toguarantee perpetuation. Through 1938, horseback riders rounded up as many bison as
possible in late fall and drove them into the Lamar Valley for feeding and reductions. To cut
population numbers to desired levels during these reductions (and in most later ones),
cripples, aged animals, and those infected with brucellosis or otherwise considered
undesirable were removed to improve the herd, in keeping with the ranching viewpoint (W.S.
Chapman 1969 pers. comm.). In 1939, a hay-baiting operation was substituted for theThe Bison of Yellowstone National Park (Chapter 3)

roundup. Hay was fed to some extent every winter through 1952. Before 1936, most animals
wintered in Lamar, with some in Pelican. During summer, bison concentrated on the Mirror
Plateau and Upper Lamar, with scattered bulls and a few small groups to the north. In spite ofvery large populations wintering in Lamar, natural reestablishment of the population west
beyond the Pelican area into Hayden Valley and the Firehole did not occur, although a 1946
file report contains a penciled notation of some bison in Hayden Valley in 1930-31.
TABLE 4. Presumed age and sex composition, fenced herd, 1903-10.

Males
Year Age: Adult 7
1903
2-P

1904

2-P

1905

2-P

1906

2-P

1907

1908

1909

1910a

6

5

4

3

Females2

Yrlg Calf Adult 7 6
2-P 18-P
2W
2-W 6-P 17-P
2-P

5

4

3

2

Yrlg Calf
3-P

3-P 1W
6-P
3-P 1-W 2-P
6-P

2- 6-P 3-P 17-PW
2-P
2- 6-P 3-P 9-P 17-P
3-P 1- 2-P
W
W
2-P
6-P
2- 6-P 3-P 9-P 3
16-P
3-P 1- 2-9 4-P
W
W
2-P
6-P
2- 6-P 3-P 9-P 3
7
16-P
3-P 1- 2-P 4-P 2
W
W
2-P
6-P
2- 6-P 3-P 9-P 3 7
13 16-P
3- 1- 2-P 4-P 2 7
W
1P W
2W
6-P
P
2- 5- 2-P 7-P 3 6 13 19 15-P 3- 1- 2-P 4-P 2 7 9
W P
1-W
P W
26P
P

4-P

2

7

9

9

P — plains type; W — wild type.
aFor 1910, the number of females, yearlings and older, does not agree with table 3 because of
discrepancies in available records.

TABLE 5. Presumed age classes of male bison on the range, 1921.

Age classes

Wild herd

Introduced herd

The Bison of Yellowstone National Park (Chapter 3)

1
7
21
2
5
47
3
4
30
4
3
30
5
2
23
6+
30
47
Total males 1 year and older 51
198a
Total population
125 estimated 526
An equal sex ratio is assumed.
aNumber includes 96 steers among the 1-5 year olds.

In 1936, animals were trucked to the Firehole and Hayden valleys for release. They were
thought to have formed separate herds, but as numbers increased, some movement between
the two valleys became obvious, and they were called the Mary Mountain herd. Two otherherds were distinguished, on the basis of wintering areas, as the Lamar and Pelican. None ofthese herds is geographically isolated at all seasons of the year, but the names are still used todesignate the wintering populations.
Population counts, estimates, and known losses (mainly reductions) are listed in Appendix IVby the three wintering populations and as park totals. Aerial counts were started for the fourmain wintering valleys (Lamar, Pelican, Hayden Valley, Firehole) in 1949. These counts were
not made every year, nor were all main areas checked each time. Usually no attempt wasmade to count scattered animals in fringe areas, nor to check the Bechler Meadows before
1965 (Jim Stradley 1968 pers. comm.). When aerial counts were not available, winter groundcounts were made. Estimates based on previous counts, reduction figures, and presumed
increases were made by park personnel when counts were not available. Because of possible
population shifts, these may be unreliable. Population numbers are for winter seasons, after
reductions, but before calving.
Bison increased steadily after 1902 until, with a gradual change in policy about 1930 from oneof ranching to one of preservation of bison in a natural state, the National Park Service
decided to cut the numbers wintering in Lamar. The decision was based on the gradualelimination of artificial management practices and supported by information derived from a
range-condition and carrying-capacity study (Rush 1932b). Lamar-wintering bison numberedover 1000 from 1929 through 1932, before Rush recommended a maximum of 1000. Later
decisions lowered the maximum number until frequent reductions had cut Lamar herd
numbers to a count of 143 in 1952. After an aerial count for all main wintering valleys totaled
1477 in January 1954, reductions were made on all population segments. An aerial count for
the entire park of 397, made in March 1967, was considered very accurate. Thus, the park
population of bison for most of the study period was lower than at any time since the earlyyears of the introduced herd.
Winter and summer distributions for mixed herd groups and separate bulls at population levelsof the study period are shown in Table 6. Divisions between major areas indicate geographic
separation but do not imply population isolation. Bulls were found in all areas of herd use andalso were scattered in places where herd groups were seldom or never seen. Past records
indicate that mixed herd groups used some of these areas when population numbers werehigher. In effect, places most frequented by mixed herd groups probably represent core areasor population centers from which bulls and mixed herd groups move into less-favoredlocations as the population increases.

The Bison of Yellowstone National Park (Chapter 3)

Although Firehole and Hayden valleys are combined as the Mary Mountain area, winterdistribution of total numbers and mixed herd groups favored Hayden Valley, according toavailable counts since the 1950s. During the reductions of 1964-65 and 1965-66, animals
were herded from Hayden Valley to the Nez Perce trap on the Firehole side with helicopters,
but a prereduction count in December 1964 showed 436 bison in Hayden Valley, and only 54
on the Firehole. Prereduction counts of 1965-66 also located most animals in Hayden Valley.
Groups released from the trap usually remained on the west side the rest of the winter, but
movements by them between the two wintering valleys were known for all seasons. Groups
were seen only in the two main valleys and the intervening Nez Perce Creek drainage during
the study period, but a group of 20-23 was seen at Beach or Dryad lakes, 5 miles south of
Hayden Valley, the winter of 1955-56 (Jim Stradley 1968 pers. comm.).
The majority of the wintering mixed herd groups of the Mary Mountain area summered in
Hayden Valley and to the south of it as far as Beach and Dryad lakes, although some animals
from the same population summered to the west of the Firehole. Ranger reports indicate that
infrequent mixed herd use of the Madison Plateau began in 1939, 3 years after the bison werereleased on the Firehole. By the early 1950s, use had become common, but apparently almost
ceased after the 1955 reduction. But in 1963 as many as 50 ranged from the Little Firehole
Meadows to the Pitchstone Plateau. In spite of more reductions, small mixed herd groups
were seen during the summers of 1965, 1966, and 1967.
After the early 1900s, animals were not again reported wintering in the Bechler Meadowssouthwest of the Madison Plateau until February 1955, when three bulls were seen justoutside the park. An occasional bull may have wintered in the meadows earlier, since a few
animals again began to summer on the Madison Plateau in 1939. Observations and reports
indicate a few animals in that area nearly every winter since the mid-1950s, in spite ofconsiderable decrease in the Mary Mountain herd, from which these animals probably came.
No mixed herd groups were reported wintering in the Bechler Meadows until 1962-63, but thearea is seldom visited in winter. Periodic plane flights begun in March 1965 showed a small
group there in 1964-65 and 1965-66.
Lamar and Pelican populations are isolated from each other during most of the winter except
for occasional movements of a few hardy bulls. Table 6 shows the valleys as distinct
wintering areas. Groups in Lamar ranged the valley from Soda Butte west to the Hellroaring
Slopes. In Pelican, group use extended from the Mushpots-Mudkettles of Pelican Creek
downstream to Vermilion Hot Springs and included the lower parts of Astringent Creek andadjacent hot-spring areas to the west. Although no groups frequented Ponuntpa Hot Springs(6 miles north of Pelican Valley) during the study, both historic records and reports of themid-1950s (Jim Stradley 1969 pers. comm.) indicated some previous mixed herd use.
TABLE 6. Distribution of the present population, 1969.

Summer

Winter
Bulls
Mixed groupareas
Round Prairie
Cache Cr.
Slough Cr.

Mixed herd
Mixed herd groups
groupsSoda Butte aMt. Norris
area
Cache-Calfee ridge
aupper main Miller Cr. ridge
Lamar
Canoe Lake-Hoodoos
aSaddlle Mt.
Valley

Bulls

Upper
Lamar

mixed groupareas
widely scatterednorth of Lamar
Valley and on

The Bison of Yellowstone National Park (Chapter 3)

Hellroaring- Lamar
Tower Jct. area

andlower main aLittle Saddle Mt.
MirrorLamarhead of Flint Cr. to heads Plateau
Valleyof Pelican, Timothy,
aHellroaring
Raven Cr.
Slope area

the Mirror
PlateauCache Cr.
Miller Cr.
along the upper
Lamar R.

aMushpots- ahead of Opal Cr.
Mixed groupareas
Mudkettles ahead of Buffalo Fork of
Ponuntpa Hot
main valley Timothy Cr.
Sp.
fromHeads of Opal
Pelican Sp.
and Flint Cr.
toWhite Lake
Vermilion
Astringent Cr.
Sp.
Upper Pelican
aTurbid
PelicanValleyLake area
Mouth Pelican
athermalCr.
areas west
Lakeshoreoffrom
Astringent
Steamboat Pt.
Cr.
to theYellowstoneR.
Mixed group
mixed groupwest ofwest and southwest part
areas
areas
Yellowstone inc. Highland Hot Sp.
East side of
Cygnet Lakes
River:
upper Alum Cr.
Yellowstone
Haydenlower Sour Cr.
southwest aupper Trout Cr.
HaydenR.
ValleyArnica Cr.
corneracentral valley
ValleyMud Volcano
Areanortheast to aupper Nez Perce Cr.
Entire mainjunction
upper Spruce Cr. tovalleyAlumBeach Lake and area
Beach Lake
Violet Cr.
aupper Nez from Little Firehole
Mixed groupwidely scatteredareas
Mdws. south across
Perce Cr.
Entirelower Nez Summit lake area to west
Firehole area
end of Pitchstone Plateau
Perce Cr.
afrom Old
upper Boundary Cr.
entireFaithful
Lower
Madisonthrough theGeyserandFirehole Basin
Lower
Pitchstone
Firehole
aMidway
Plateaus
Geyser Basin
GeyserMadison Jct.
Basin
area
aBiscuit
Smokejumper
GeyserHot Sp.
Basin
Bechler Ford
BechlerDunanda Hot Bechler FordSp.
aLess used.

The Bison of Yellowstone National Park (Chapter 3)

Bison from both Pelican and Lamar Valley wintering populations ranged widely during
summers on the Mirror Plateau and the Upper Lamar. Neckband observations and aerial
counts showed that the two populations, except scattered bulls, combined on the eastboundary for several weeks in 1967. Main use areas in the Upper Lamar region during thestudy period were the Cache-Calfee and the Miller Creek ridges from the east boundary
down, and the series of meadows and parks on the east rim of the Mirror plateau extending
from the head of Flint Creek to the heads of Pelican-Timothy-Raven creeks. At higher
population numbers, as reports of the 1930s and 1950s indicate, herd-group use included mostof Specimen Ridge north and west of Flint Creek as well.
To the north of Lamar Valley, where at present only bulls summer, past reports indicate small
mixed herd groups on the upper Slough Creek meadows and the Buffalo Plateau (Jim
Stradley, Dave Pierson 1968 pers. comm.). In August 1943, a report was received of an
estimated 150 bison near Lake Abundance, just outside the northeast corner of the park.
Two small areas, separated by distance and topography from the four main valleys, have hadsmall wintering mixed herd groups before the study period, according to recent records.
Approximately 4050 bison wintered north of the Madison River on the flats just southwest of
the Cougar Creek patrol cabin in 1955-56. Some were also seen in 1959. In the Antelope
Creek basin on the northeast flank of Mount Washburn (no date), 45-70 wintered one year
(Jim Stradley 1968 pers. comm.). There were no summer reports of groups north of theMadison River, although the bison wintering there in the 1950s may also have summered
there.
Bulls were not distributed proportionately among the four main wintering valleys, as shown in
Table 7. Most of the Mary Mountain area bulls wintered in Hayden Valley. Lamar Valley had
more bulls than did the Pelican area. In summer, bull distribution was widespread. Animals
were so scattered that preference for certain general areas by a large percent of the bulls was
not observed.
Recent and present population distributions generally resemble those described by historicalsources (Fig. 11). Winter distributions within the park approximate those of early times, as dosummer distributions on the Mirror-Upper Lamar. Other summer distributions have changed
most. The herd which summered north of the Lamar-Yellowstone rivers in historic times is
now gone. The large numbers which once ranged the west side (Madison-Pitchstone plateaus)in summer are reduced to comparatively few. The segments of these two historical summer
herds which wintered beyond the park boundaries are also gone. The recent Hayden Valley
summering population seems larger than the historic population. Bison use of the valley may
actually have increased, compared to former times, as the population became reestablished.
Or the increase may not be real, but may result from incomplete historical information.
TABLE 7. Comparative distribution of bulls wintering apart from mixed groups.

PelicanHayden Valley
Firehole
Lamar
No. Total % No. Total % No. Total % No. Total %Yearbulls pop. Bulls bulls pop. Bulls bulls pop. Bulls bulls pop. Bulls
1965-66 36 66 55 29 100 29
1966-67 48 82 56 28 124 23 89 135 66 15 54 26
1967-68 44 89 54 33 160 19 73 131 56 11 57 19

The Bison of Yellowstone National Park (Chapter 3)

Although present winter distributions seem little altered (except in total numbers) compared tohistoric times, the Firehole population may be larger now. Changes in the summering
distributions of Hayden Valley to the east and the Madison-Pitchstone plateaus to the west
may have caused changes on the Firehole, or unrecorded poaching in that wintering valley
may have resulted in apparent early low numbers.

chap3a.htm
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The Bison of Yellowstone National Park (Chapter 4)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 4:

GENERAL CHARACTERISTICS
Physical Characteristics
Appearance
BISON ARE GENERALLY dark brown in color, almost black when a new coat is growing induring summer. The head, forelegs, hump, and shoulders are covered with longer hair (about
6 inches on shoulders and hump), but the hair on the flanks and hindquarters is much shorter(about 1 inch), so that some bison look as though they had been clipped (Fig. 14). As the coatages, the longer hair over the hump and shoulders may lighten considerably, becoming almost
tan on some animals, particularly older bulls. Shedding of old hair begins in spring, but manybison still have ragged patches of lighter-colored, old hair in mid-summer, particularly on theshoulders (Fig. 15). Wisps of this crinkly, shedding hair are commonly seen on trees andbushes (Fig. 16).

Fig. 14. Clipped appearance of a mature bull. Photo by M.D. Beal, Yellowstone
National Park.

The Bison of Yellowstone National Park (Chapter 4)

Fig. 15. Bison shedding old hair, mid-summer.

Fig. 16. Wisps of shed bison hair on a branch of a lodgepole pine.

Calves are reddish tan at birth (Fig. 17) but begin to lose this first coat and change to brownblack at about 3 months (Fig. 18). By about 5-6 months of age calves are completely dark. The
occasional red one seen in the fall is a late-born calf.

The Bison of Yellowstone National Park (Chapter 4)

Fig. 17. Newly-born calves in a mixed herd group. Photo by Verde Watson,
Yellowstone National Park.

Fig. 18. The calf (5-6 months old) to the left of the cow has lost its first red-brownpelage. Photo by David Condon, Yellowstone National Park.

Males and females generally resemble each other in color, shape, and presence of permanenthorns. Both sexes have the shoulder hump (calves do not) which, together with the longer hairon the foreparts and head, give a massive appearance to the front of the body compared withthe hindquarters. Bison are, however, sexually dimorphic (different in appearance); older
animals can be differentiated by an observer (Figs. 19-22). Horn size and shape ischaracteristic; additionally, bulls are larger and the head shape is broader and generally more
massive. The contrast between areas of long and short hair on bulls is more marked.

The Bison of Yellowstone National Park (Chapter 4)

Fig. 19. Note head shape and relative size of the cow, left center, compared with thebull at right. Photo by David Condon, Yellowstone National Park.

Fig. 20. Spike-horn bull, approximately 2.5 years old. Photo by David Condon,
Yellowstone National Park.

The Bison of Yellowstone National Park (Chapter 4)

Fig. 21. Standing animals, from left; spike-horn bull, yearling female (approximately
1.5 years old), cow, cow, cow, bull. Photo by David Condon, Yellowstone National
Park.

Fig. 22. The horns of the adult cow (at right) are relatively slender compared withthose of bulls. The spike-horn bull at left is approximately 3.5 years old. Photo by
David Condon, Yellowstone National Park.

WeightWeight differences are greatest between male and female adult bison. Weights (except adultbulls) were recorded in Yellowstone during the winters of 1964-65 and 1965-66, when adults
weighed less (indicated by sequential winter weight records) than they would in the fall.
Estimates of maximum bull weights of 2000 pounds were made by experienced observers.
Most adult cows weighed between 800 and 1100 pounds. Yearlings of both sexes usuallyweighed between 500 and 700 pounds, calves (8-9 months old), between 300 and 400 pounds.
Weights at birth have not been recorded here; Park (1969) gives a range of 30-70 pounds.
No record was made of the weight of the Yellowstone bull (Fig. 23) whose skull is still thelargest listed in the records of the Boone and Crockett Club (1964). This animal, a member ofthe Buffalo Ranch herd (see History) was shot in 1925 after he became too dangerous for theThe Bison of Yellowstone National Park (Chapter 4)

semi-ranching operation of the time. Old park files indicate he was the off-spring of one ofthe plains bison cows which was pregnant when brought to Yellowstone in 1902. Hence thisbull was of plains bison stock, rather than a hybrid off-spring of plains and mountain bison.

Fig. 23. Old Tex, the Yellowstone bull whose head is still first among record bisonheads listed by the Boone and Crockett Club (1964). Photo by James Kimberlin,
Yellowstone National Park.

Life spanLongevity in a wild bison population is usually less than that of animals in zoos and otherprotected circumstances. Longevity may also vary among wild populations. In Yellowstone,
relatively few members of the population attain old age, which probably begins at 12-15 yearsof age (Fuller 1959). An occasional one of these aged bison is probably more than 20 years
old (from Yellowstone trap records of 1964-65 and 1965-66).

Behavior Characteristics

The Bison of Yellowstone National Park (Chapter 4)Grouping characteristics
Bison are gregarious animals usually found in groups of various sizes, although there arescattered solitary bulls at all season. The vast herds (of plains bison) commonly mentioned byhistorians are not seen in Yellowstone. Small bands, typical of the original mountain bison
population (as described by early travelers), are also characteristic at present. During thehigher population levels of the 1950s, McHugh (1958) found that cow (mixed) group size
ranged from 10 to 50 in Lamar during the winter, with a mean of 20. During the rut in Hayden
Valley, he observed a range of 19-480, with a mean of 175.
At population levels of the present study, small winter groups were also characteristic; during
summer, groups of more than 100 were rare. The occasional melding of smaller herd units
into a much larger group usually resulted from disturbance by people or aircraft. Typically,
even when 100 or more animals were in sight at once in Hayden Valley during the summer,
they were in two or more subunits which were often close together, but did not actually form
one large herd. However, during the rut, the subunits sometimes melded although they were
not disturbed.
Although mature bulls were commonly seen in the mixed groups at all seasons, many bulls
were separate from these groups. Some bulls (not always old animals) were solitary, but pairs
and small groups up to four and five were common, particularly in winter. Occasionally a cow
was seen with a bull group. Such cows were without calves at the time, but were not always
old or barren as McHugh observed. Younger cows were seen in bull groups several times; one(a crippled cow) was seen with a calf after wintering with a bull group.
Small bands appear to be the basic population unit, but the nature of these bands is not clear.
Fuller (1960) considered the observations of various writers and concluded that there was abasic unit of some sort, centering around 11-20 individuals. McHugh (1958) concluded that
subgroup and group formation was flexible, with little dependence on blood relationship(except the cow with calf).
Behavior in specific circumstances
Historical references often mention that bison face into the wind during snowstorms. This may
have been very common among plains bison when no shelter was available. Conditions whichprevail during severe snowstorms in Yellowstone permitted few observations during thisstudy, but bison, when visible at all, were not seen standing head into the wind. Rather, they
were bedded in the snow, usually in whatever protection small variations in terrain offered. At
times they were seen moving with the wind, sometimes into the trees at the edges of thewintering valleys. Dave Pierson (1971 pers. comm.) states that during the Buffalo Ranch
operation in Lamar he often saw bison on the open feedgrounds facing into the most severe
winter storms.
During the breeding season (rut), bulls engaged in considerable head shoving, but actual
battles were never witnessed. Fuller (1960) witnessed shoving matches between bulls, but
most encounters were decided by threats. McHugh (1958) described battles but did not statethat these were between unfenced bison bulls. The bulls do a great deal of bellowing, alongwith horning of trees and ground, and more wallowing than is observed at other times. Bulls
do not dominate groups of cows as a harem unit, as do elk (Cervus canadensis), but areusually part of a mixed herd group along with other bulls of various ages. There was noevidence from this study that solitary bulls were forced away from mixed groups.
Bison are very agile, being able and willing to traverse fallen trees and steep slopes withspeed. They are capable of a top speed of 30-35 mph (Fuller 1960) and, are strong swimmers.
Although large, they readily disappear in the forest, blending with the darkness of lodgepole

The Bison of Yellowstone National Park (Chapter 4)pines.
Senses and disposition
Bison use the senses of smell, hearing, and sight. The sense of smell is well developed, andbison reaction to the odor of an observer is often more marked than reaction to sight or sound.
Bison are typically alert and are wary of an observer whether seen or heard, but a carefulapproach to a viewpoint is often possible if the wind has not carried the scent to them. Afteran observer is scented, flight is usually immediate for at least a short distance.
Sight more frequently causes flight than does sound, and an observer sighted on foot is moredisturbing than one on horseback. In winter a skier is usually detected as soon as in view of aherd, although the skier may be a mile or more away. However, if the skier uses whiteclothing, approach to less than 100 yards is sometimes possible unless scent disturbs thebison.
TABLE 8. Opportunities to see bison from present park roads.

Location and frequency
Bulls
Herd groups

Time of year

Winter, spring (thru
May)

daily
Lamar: west of Lamar
Canyon and Soda ButteaFirehole Geyser Basins

daily

aHayden Valley

daily

aMary Bay

daily

June

Hayden Valley

July, early August

Hayden Valley

Lamar:
frequently
especiallywest of
Lamar
CanyonaLowerfrequently
Geyser Basinoccasionally Same asabove inearly June
only
Firehole, particularly the frequently
Lower Geyser Basin andnear Old Faithful
Mary Bayearly June
only

Mid-August to mid- Lower Geyser Basin
September
Hayden Valley
Lamar
Same as above

After midSeptember
Late fall (roads still Lower Geyser Basin
open tofrequently

not
seen

frequently
frequently
frequently
occasionallyfrequently

not seenLoweroccasionally
Geyser Basin
Lower
frequently
Geyser Basin

The Bison of Yellowstone National Park (Chapter 4)

conventional
vehicles)Hayden Valley
Mary Bay

frequently
frequently

Lamar
HaydenValleyoccasionallyrarelyaVia oversnow vehicle until the roads are plowed in the spring.

Note: In the Lower Geyser Basin, two side roads—Fountain Flat and Firehole Lake—inaddition to the main road all provide opportunities to see bison.
One exception to the usual wariness of bison is common. Solitary bulls are probably as awareof an observer in a given set of circumstances as is a group of bison. However, these bulls aremuch more inclined to stand their ground, particularly near roads, where they are moreaccustomed to people. Their tolerance of approach is misleading; they are not aggressive, butwhen approach is beyond tolerance, they will depart. The line of departure may be through orover unwary people who sometimes nearly surround one of these bulls.
Observations made during this study concur with those of Fuller (1960), who reported thatbison were neither aggressive nor unpredictable. He characterized the mixed herds as usually
shy and timid and used the term "stolid indifference" for the bull groups. All bison should beviewed from a respectful distance.
Visitor opportunities to see bison
Bison behavior and habits (see Movements) influence opportunity to see them from park roads(Table 8). Such viewing is best done from a vehicle, to minimize disturbing the animals anddestroying the opportunity for others to watch.
The visitor who is able and willing to penetrate the wilderness of Yellowstone on foot orhorseback may, with luck, see the herd groups on their summer ranges. The herd groups in
Yellowstone can be characterized as very elusive and very mobile, and a sight of them is notalways possible even for the experienced observer. But the opportunity to watch a group of
truly wild bison, living as they have for generations in this high mountain wilderness, is anexperience to be remembered and cherished.

chap4.htm
Last Updated: 24-Jan-2005

The Bison of Yellowstone National Park (Chapter 5)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 5:

POPULATION CHARACTERISTICS
THIS CHAPTER DISCUSSES THE REPRODUCTION and population structure and dynamics
of Yellowstone bison during the period 1964-68. A series of bison reductions from 1961 through1965 consistently removed a large number of breeding-age females. Records indicate that the
reductions by field shooting of the mid-1950s also did this, as did some of the earlier removals at
the Buffalo Ranch in Lamar (Table 9). Some population characteristics may change after a period
without reductions. Data for all categories were not obtainable each year; hence, selected figures
are used in some instances to suggest population conditions.
TABLE 9. Number of cows and calves removed during reductions.

Year

Location

Cows
CalvesPercent ofPercent of bTotal
Percent of
No. total classified No. total classified no. classified reduction

1931-32 Lamar
184
1932-33 Lamar
90
1933-34 Lamar
59
1938-39 Lamar
9
1940-41 Lamar
110
1941-42 Lamar
78
1943-44 Lamar
219
1945-46 Lamar
94
1949-50 Lamar
129
1953-54 Lamar
34
Lamar
15
a
1955-56 Mary Mountain 123
bPelican
53
Lamar
29
1956-57 a
Mary Mountain 93
1961-62 Lamar
74
1962-63 Mary Mountain 187
Lamar42
1964-65 Mary Mountain 119
aPelican
14

90
45
85
13
54
39
55
47
57
45

1
0
0
0
0
41
90
20
39
13

21
22
10
17
17

205
199
69
67
205
200
400
200
228
75

92
96
39
100
100
100
99
100
100
100

62 2
53 59
45 32

8
26
27

24
231
118

100
100
100

49 13
44 43
52 33
52 101
51 6
50 39
41 8

22
20
23
28
7
12
24

59
212
143
357
82
238
34

100
100
100
100
100
100
100

The Bison of Yellowstone National Park (Chapter 5)

1965-66 Mary Mountain

18

36

9

18

50

100

aField shooting.
bTotal classified (bulls, steers, calves) not necessarily total reduction number.

Sexual Maturity
Incidence of pregnancy by age class for two Yellowstone studies 25 years apart are compared inTable 10 as an indication of sexual maturity in the female population. The 1940-41 study
sampled the semiranched population of Lamar; the 1964-66 study sampled the entire free-ranging
population. The rates of pregnancy in the younger age classes are suggestive only, due to limited
sampling. The 1940-41 study of the semidomestic herd indicated that an occasional female bred
as a yearling. None (of 15 sampled) was found to be pregnant in the later study of wild bison.
The 1964-66 study indicated that a few more bred as 2-year-olds and that approximately a fourthof the 3-year-olds were breeding. Both studies showed that the majority of females attained
sexual maturity when 4 years old.
TABLE 10. Comparison of female pregnancy rates, by age classes, 1940-41 and 1954-66.

No. sampled
Age class
2.5
3.5
4.5
Young adult
Adult
Aged
Entire sample

1940-41a

Percent pregnant
1964-66
1940-41a

1964-66
2
4
13
10
49
8
86

7
11
7
6
23
17
71

0
50
92
100
86
100
86

14
27
71
50
57
75
52

aFrom Skinner, Curtis K. 1941. Special report on Yellowstone National Park bison. Yell. Natl.

Park Bio. Files, 715-03. Buffalo (General). Typed.
Sexual maturity for the female population as a whole may be occurring somewhat later now. The
1964-66 study of wild bison showed fewer females pregnant in the 3.5 and 4.5 age classes (27and 71%, respectively) compared with 1940-41 study of the semidomesticated bison (50 and 929,
respectively).
Sexual maturation also may be later in the Yellowstone population of this study compared withherds elsewhere. At Wood Buffalo National Park, 36% (160 sampled) of the Hay Camp and 59%(17 sampled) of the Lake Claire 2-year-olds were pregnant. Rates were 52% at both locations (92and 31 sampled, respectively) for 3-year-olds (Fuller 1962). At Wichita, 74% (35 sampled) of the
3-year-old cows had calves (Halloran 1968).
Sexual maturity of males was not studied in Yellowstone. However, Fuller (1962) found thatexamination for spermatogenesis showed the age for males to be comparable to that for females:a few mature as yearlings, a third as 2-year-olds, and probably all others by 3 years of age.

The Bison of Yellowstone National Park (Chapter 5)

Halloran (1968) found that two experimental bulls were effective sires as 2-year-olds. According
to observations made by McHugh (1958) in Hayden Valley in Yellowstone, males 8 years andolder were the most active sexually, as indicated by "tending bonds"—the term he used for the
relationship between a bull and a particular cow during the rut. Fuller (1960) also observed that
only fully mature males tended cows. Apparently, sexual maturity in males occurs well before
they are a part of the active breeding population.

Reproduction Rate
The present wild population showed a lower pregnancy rate in all age classes over 2.5 years
compared with the semidomesticated herd of 1940-41 (Table 10). Females 3.5 years of age andolder averaged 56 and 90%, respectively. Females 4.5 years and older averaged 62 and 90%,
respectively.
Table 11 compares reproductive data recorded at Lamar by Rush (1932a), several later
unpublished compilations also made at Lamar, and this study of the entire population. The
pregnancy rate of 52% for females 2.5 years of age and older determined in this study was thelowest recorded in Yellowstone. The reason for this was not clear, because the age classes
represented in all previous compilations (except 1940-41) were not recorded. The rate of 65% in
1931-32, which was lower than others prior to this study, may reflect a high percentage of aged
females in that sample, as few cows were removed from the semidomestic herd before 1930. The
influence of ranching practices such as winter feeding and culling of aged animals for many years
may account for subsequent high pregnancy rates.
TABLE 11. Summary of reproductive data and fetal sex rations, 1931-32 through 1964-66.

Pregnant
Total
and Pregnant Lactating
Fetal sex
Number pregnant lactating only
only Number
ratio
Percent
Year Source sampled percent percent percent percent sampled male/female unclassified
1931- Rush,
32
1932a
1940- Skinner,
41
1941
Yell.
1943- Natl.
44
Park
files
Yell.
1945- Natl.
46
Park
files
Yell.
1949- Natl.
50
Park
files
1964- Present
66
Studyb

184

65

52

12

24

54

108/100

-

86

86

-

-

5

74

163/100

1

219

75

-

-

-

-

-

-

82a

79

-

-

-

62

112/100

5

115

94

-

-

-

104

138/100

1

71

52

3

50

1

-

-

-

The Bison of Yellowstone National Park (Chapter 5)

aSample included only females 4 years of age and older. Other samples included some females inthe younger age classes.
bThis study sampled the entire population. Previous studies sampled only Lamar.

Yellowstone's present wild bison population showed a reproductive rate equal to the 52% reported
by Halloran (1968), and lower than the rate among all populations compared by Fuller (1962).
Halloran attributed the low rate at Wichita Mountains Wildlife Refuge to high calf survival.
Calves were known to nurse into their second year of life, thus prolonging the physical drain on
the cows (and perhaps influencing the possibility of conception). Fuller considered brucellosis
infection and severe climate as possible adverse influences on reproductive rates in Wood
Buffalo National Park.
Calf survival apparently was not an important influence on the reproductive rate determined by
the present study. Although survival appeared high (see Calf Mortality), no yearlings wereobserved nursing during the study. Only 4% of the cows (Table 11) examined during the midwinter reductions were still lactating.
Brucellosis in Yellowstone animals did not appear to be a factor in the low incidence ofpregnancy. Rate of infection according to tests from 1964-66 averaged about 54% for Lamar,
42% for Pelican, and 26% at Nez Perce Creek in the Firehole area (Barmore 1968). These rates
were all lower than the 62% at Lamar in 1941 when the pregnancy rate, at 86%, was much higher
than now. Although Rush (1932a) mentions that a number of abortions were known to haveoccurred, abortions were apparently rare except in the crowded corral at the Buffalo Ranch (DavePierson 1968 pers. comm.). Quortrup (1945) stated that brucellosis had little or no effect on theherds, as did Tunnicliff and Marsh (1935) and McKenney (Skinner 1941).
Differences in population age structure, as reflected in the samples, partly explain differences in
reproductive rates between the wild bison populations of Wood Buffalo and Yellowstone
National parks. Subadults and young adults formed a much larger part of the Wood Buffalo
National Park samples (Fuller 1962); aged animals formed more of the Yellowstone sample.
However, all age classes (except the aged) in Yellowstone showed a lower reproductive rate.
The low reproductive rate in Yellowstone may result from a complex of environmental factors, inpart related to severity of the winters. Both Yellowstone and Wood Buffalo National parks havesevere winter conditions, but the details differ (Table 12). Fuller (1962) believed extreme cold,
per se, had little effect on bison, but was important when there was wind. Wood Buffalo National
Park, compared with Yellowstone, is colder, but has less snow and fewer periods of crusting
conditions during the winter. Trees provide protection from the wind. Differences in amount ofwind were not as apparent. Yellowstone apparently has a more severe winter environment, forbison, than does Wood Buffalo National Park.
TABLE 12. Comparison of winter climatic factors in Wood Buffalo and Yellowstone National
Parks.

Wood
BuffaloNational
Parka

Cold
Snowfall Crusting
January mean
53"
apparently
daily maximum
rare-7.8°F

Yellowstone January mean

approxmost

Wind
Wind protection
rarely over 15 woods everywhere
mph ininterspersed with grazing
extreme cold areas
a winterno interspersed woods

The Bison of Yellowstone National Park (Chapter 5)

National
Parkbdaily maximum
approx. 22°F

150"

winters,
one ormore
periods

average ofmore than
8.5 mph(except the Firehole),
winter vallyes large andopen

aInformation from Fuller, W. A., 1962. The biology and management of the Bison of Wood

Buffalo National Park. Can. Wildl. Serv. Wildl. Manage. Bull. Ser. 1, No. 16, 52 p.
bInformation from U.S. Dep. Commer. Climatological Summary for Yellowstone National Park

(1930-59). Temperatures and snowfall are for the park interior.
The effects of the Yellowstone winters on subadults is suggested by the mortality among them, as
discussed later. Winter conditions, perhaps through nutritional influences, may delay sexual
maturity among subadults. Houston (1968) suggested that animal nutrition during winter periods
might control yearling moose (Alces alces) ovulation rates. Robinette et al. (1955) attributed
reproductive rates among yearling mule deer (Odocoileus hemionus) to the type of winterpreceding that during which the pregnancy rates were determined. Possible variation in effects
between mild and severe Yellowstone winters was not obtained during this study.
The influence of Yellowstone winters on reproductive rates among adult bison was unknown.
Pregnancy rates among adult moose in Jackson Hole, south of Yellowstone, approximated thosefrom other ranges (Houston 1968). Other environmental factors which were not apparent fromthis comparison of Yellowstone and Wood Buffalo National parks may be important in affecting
adult reproductive rates.

Fetal Sex Ratio
The fetal sex ratio was not estimated during this study. However, records kept by Rush (1932a)and during four later reductions in Lamar (Table 11) showed more males among fetuses, ranging
from 108 to 163 males/100 females and averaging 127 males/100 females (294 fetuses). This was
slightly higher than the 112 males/100 females reported by Fuller (1962).

Number of Young at Birth
No twin fetuses were noted in any of the above records. One instance of twins in the Lamar herd
was reported (McHugh 958). Other workers (Fuller 1962; Halloran 1968) and historical accounts
agree that twins are rare.

Population Structure
Sex and age structure was suggested mainly by trap records made during live-trapping operations
from late December to late February in the winter of 1964-65, and from mid-January to midMarch 1966. Efforts were made to trap as many of the Lamar (Crystal trap) and Mary Mountain(Nez Perce trap) animals as possible. More were trapped during the severe winter of 1964-65
than in 1966. Trapping success for calves of the previous spring was nearly 100%, as indicatedby comparison of 1964-65 Mary Mountain early inter-aerial count records (72 calves) and Nez
Perce trap records (77 calves). Most yearlings were probably trapped. Success (indicated by the
temporary backtags and the number of retrapped animals) was high in the 2.5- and 3.5-year-oldclasses, but a few undoubtedly were not taken. Most adult females were trapped; trap success
was lowest for males of age classes above 3.5 years, particularly in 1966. That year only 7% of
all captures older than 3.5 years were males, compared with 37% in 1964-65 (Nez Perce trap). In

The Bison of Yellowstone National Park (Chapter 5)

addition to the influence of snow depth on trap success, animals trapped the previous year
seemed harder to herd.
Age classes for all females trapped (Table 13) provided population sex-ratio information foranimals less than 4.5 years of age. The records for all traps suggest that a slightly higher
percentage of female calves survive their first year than do males, but the pooled data for
yearlings and 2.5-year-olds suggest no further differential loss for this period. The variability,
when individual trap records are compared, among the percentages of females in the 2.5- and 3.5year-old classes may reflect the removal of calves in reductions of 1961-62 (Lamar) and 1962-63(Mary Mountain). Although this may explain the very low percent of 3.5-year-old females taken
at the Lamar trap, all trap records suggest that fewer females survive in this age group. Thus,
female survival may be favored the first year, but male survival may be favored the next 3 yearsof life. Fuller (1960) also noted more males than females in the spikehorn, or 2.5- to 3.5-year-old
group, but believed the identifications were biased. By 4.5 years of age and older, differential
survival cannot be distinguished from differential trap success.
TABLE 13. Age classes of bison trapped, reductions of 1964-66.

Lamar 1965-65
FemalesClass

Nez Perce 1964-65 Nez Perce 1965-66
FemalesClass

FemalesClass

Totals for both traps
1965-66
Females
Class

%
%
%
% TrapNo. % No. Trap No. % No. Trap No. % No. Trap No. % No.
Total
Total
Total
Total
Calf
13 52 25
19 45 58 77
24 13 59 22
22 71 57 124
22
Yearling 10 53 19
14 26 50 52
16 11 44 25
25 47 51 96
17
2.5
4 40 106 17 68 25
8
3 27 11
11 24 52 46
8
3.5
3 21 1411
8 42 1965 45 11
11 16 37 44
8Adult
34 53 64
49 97 63 154
47 28 93 30
30 159 64 248
44
Totals64 49 132 100a 193 59 327 100a 60 60 99 100a 317 57 558
100a
Age
Class

aApparent errors in totals are due to rounding.

Trap records, together with the early-winter aerial count of 480 animals, indicated that adult bulls
outnumbered adult cows in the Mary Mountain population of 1964-65. The actual ratio could not
be determined, but a minimum bull population of 150 was estimated from the number of trappedbulls removed (48), the scattered bulls in Hayden Valley which could not be driven toward thetrap (53), and the number of bulls among the remaining 100 animals never trapped (50 bulls
estimated). Because there were probably adult cows as well as some subadults of both sexes
among the other 50 animals (of the 100 never trapped), bulls probably totaled less than 60% of
the adult population. More bulls than cows could be expected in both the Lamar and Mary
Mountain populations after the reductions of the early 1960s removed large numbers of adultcows. The normal proportion may be the reverse; adult cows may outnumber adult bulls. Fuller(1960) believed this to be the situation among the wild bison of Wood Buffalo National Park.
Adult male bison may be "biologically expendable" according to Etkin (1964), who states thatsexual dimorphism (termed aggressive potential in bison) interferes with male survival.
Age classes were calculated for the Mary Mountain population, using the Nez Perce trap records

The Bison of Yellowstone National Park (Chapter 5)of 1964-65 and the prereduction count of 480 bison. Mary Mountain herd records were used,rather than pooled data, because trapping success was high (68%), the sample was largest, andtrapping operations were preceded by a careful aerial census for the entire Firehole-Hayden
Valley area. The calculations suggested a winter population consisting of: calves, 16%; yearlings,
11%; 2.5-year-olds, 6%; 3.5-year-olds, 5%; and adults, 62%. The extent to which thesepercentages differ from those of a Yellowstone population not influenced by reductions is notknown.

Calf Percentages
Spring calf numbers, calculated as percentages of mixed herds (Table 14) from aerial surveys
made in late May and early June 1964 through 1968 after most calves were born, showed
considerable variation because of reduction programs. The lowest percentages recorded during
the study for Lamar, Pelican, and Mary Mountain were 7, 14, and 7%, respectively, during thespring of 1965 after reductions in all three areas removed large numbers of cows. Thereafter, allpercentages increased. By 1968 the Pelican population, where the fewest cows were removed
showed what may be a nearly "normal" (uninfluenced by reductions) 18% calves. The higher
percentages in Lamar (27%) and Mary Mountain (25%) for 1968 probably reflect the higher
pregnancy rate of an increased proportion of younger females. Although the number of animals
sampled was not large, the 1968 samples represented 95, 75, and 40% of the Pelican, Lamar, andMary Mountain mixed herd groups.
TABLE 14. Calf percentages of mixed herd numbers in spring.

Lamar
PelicanMary Mountain
All herds
No.
No.
No.
No.
%
%
%
%
a
a
a
a
Year sampled Calves sampled Calves sampled Calves sampled Calves
1964 43
1965b 43

19
7

69

14

67

7

43
179

19
10

1966c 40 est.
1967 311968 34

15 est.
19
27

133
111

15
18

109
177
48

12
24
25

149
341
262

13
20
19

aNumber sampled does not correspond with the actual population.
bReductions in all areas.
cReduction in Mary Mountain herd.

Pooled percentages for the three herds in 1967 (20%) and 1968 (19%) suggest a leveling in calf
production for the population as a whole. If so, then the usual proportion of newly born calves inmixed herds of Yellowstone bison may be 18-20%. Additional data, free from possible reduction
influences, are needed to verify this.
Spring calves as a percentage of the total population (mixed herd groups, bull groups, andscattered animals) were calculated only in 1967 from a very accurate (397 count, 400 estimate)census of the entire park just before calving season. Calves formed only 11% of the 1967 spring
total population, compared with 20% of the mixed herd groups. Although, as previously
discussed, 20% calves in mixed herd groups may be nearly normal, 11% calves among the total

The Bison of Yellowstone National Park (Chapter 5)

population may be low. Reductions have removed a larger proportion of mixed herd animals thanof bull groups and scattered animals. As a result, the total of mixed herd groups may form asmaller part of the 1967 population than it would of a population uninfluenced by recent
reductions.

Mortality
Calf mortality
The expected number of calves from the 28 females of bleeding age released from the traps
during the reduction of 1964-65, using the observed pregnancy rate of 52%, was 15. The actual
number seen in those groups in the spring of 1965 was eight. The difference probably represented
loss of embryos or neonates. A realistic percentage of such loss for the entire population could
not be judged from the limited information.
Field observations of the relatively small bison population of the study period suggested that little
additional calf mortality took place before late the following winter (March and early April).
Throughout 1966 and 1967, during and after calving season in Lamar and Pelican, periodic
ground and aerial checks were made. The agreement on total number of calves seen was quiteconsistent. Size and color of calves helped to confirm that loss, balanced by addition of some latecalves, was not occurring. Calf percentages of herd numbers throughout the year (Table 15) wereinconclusive, showing increases in 1965 and 1966, and slight decreases in 1964, 1967, and 1968.
Size of some of the samples, skill of the observers, and variable conditions of weather andanimal, visibility may have affected the quality of the counts. The percentages did suggest that
there was no appreciable calf loss. Trap records for 1964-65 from Nez Perce showed a ratio of 61
calves per 100 cows (2.5 years of age and older) in winter, although among cows removed fromthe same population that winter the pregnancy rate was 51%. The sampling may have beenbiased, the previous year's pregnancy rate may have been higher (unlikely because of a large
reduction in 1962-63), or mortality may have occurred in older age classes, but calf mortality was
not indicated. In contrast, Fuller (1962) found a steady decline in calf percentages from a peak of
23% of herd numbers in July to less than 10% by the end of the calendar year.
TABLE 15. Calf percentages of pooled mixed herd numbers throughout the year.

Pop.
yearb

SpringNo.
%b
CalvessampledSummerNo.
%b
Calvessampled

1963
1964
1965
1966
1967
1968

43
179
149
341
262

908
660
591
1533
1724
1003

19
10
13
20
19

17
18
13
19
19
18

Fall
No.
sampledb%
Calves

427
242
121
78
-

17
17
20
18
-

WinterNo.
%b
Calvessampled165
40-

aPopulation year includes spring, summer, and fall of the year shown, and winter of thefollowing calendar year.
bNumber sampled does not correspond with the actual population.

21
18
-

The Bison of Yellowstone National Park (Chapter 5)

Subadult mortality
Trap records (Table 13) suggested considerable mortality among subadults. The records show thata progressive decline in numbers occurred between calf and yearling, and between yearling and2.5-year-old age classes. One exception, an increase in percentage of yearlings compared withcalves at the Nez Perce trap in 1965-66, may have been caused by a shift of a mixed herd groupfrom one winter range to another. Previous reductions (1961-62 in Lamar; 1962-63 at Nez Perce)
may have affected the size of some age classes, but do not explain the similar pattern ofpercentages among subadult age classes recorded at both traps in 1964-65.
The calculated age classes of the 1964-65 Mary Mountain winter population (16% calves, 11%yearlings, 6% 2.5-year-olds, 67% older) suggested that half the calves which survive into theirfirst winter die before 2.5 years of age. Calf numbers indicated a potential 16% increase.
Realized percentages for yearlings and 2.5-year-olds were 13% (11/84) and 8% (6/73),
respectively. These indicate a 19% loss between the first and second winters, and a 31% loss
between the second and third winters. This mortality most likely occurs in late winter (March andearly April) at the end of the first and second years of life, rather than early in winter during thesecond and third years of life (see Other Mortality).
Variation in subadult mortality rates probably occurs, but cannot be judged from the limited data.
Previous reductions, as discussed above, probably had less influence on subadult mortality than
did environmental factors. Because this population had not been subject to an unusually severe
winter for several years, these percentages may approximate usual mortality among these agegroups.
Other mortality
Natural mortality recorded during the study period totaled 49 animals. All but one occurred
during the winter after considerable snow had accumulated, usually after January. The number ofrecorded deaths were 38, 4, 3, and 3 for the winters of 1964-65 (a severe winter, 1965-66, 196667, and 1967-68, respectively. With the exception of a small mixed herd group (18 animals), alldead animals were found scattered on the winter ranges. Of the other 30 recorded deaths, there
were 22 aged bulls, 2 cows, 3 yearlings, 1 calf, and 2 unknown. More bulls may have been foundbecause of larger carcass size. Reductions, by removal of mixed herd animals, may havesubstituted for proportionately more natural mortality among cows and younger animals thanamong bulls.
Natural mortality recorded annually over mild and average winters of the study period averaged
less than 1% of the winter herd numbers. One or two animals, usually bulls, were the most founddead in any one of the main wintering valleys. This was also the usual number found before thestudy period, according to earlier ranger reports, although population numbers varied
considerably (Appendix IV). The amount of natural mortality associated with a severe wintersuch as 1964-65 was obscured by concurrent reduction programs, but the number of deadanimals found indicated greatly increased mortality.

Population Trends
Figure 24 shows population trends based on actual counts (post-reduction, precalving) from 1936
through 1968 for the entire park, as well as for the wintering subunits of Lamar, Pelican, andMary Mountain. Known losses, mainly reductions, are also shown. The reductions, held only inLamar prior to 1954, accounted for the general downward trend in that area, although at the sametime the population as a whole increased, influenced mainly by the steady increase of the Mary
Mountain herd as it repopulated an area uninhabited by bison for more than 40 years. The peakThe Bison of Yellowstone National Park (Chapter 5)

population in the latter herd and for the total bison population in 1954 apparently coincided withincreased use of the Madison Plateau-Pitchstone Plateau summer range, as mixed herd groups
were small and infrequently reported from this area for nearly 15 years after the 1936
reintroduction on the Firehole. During the early 1950s, ranger reports indicate yearly use by
mixed herds, sometimes large in size. In June 1952, 124 adults and 11 calves were seen.

Fig. 24. Bison population trends from population counts, 1936-68.

Since the 1954 peak, all population segments have decreased. The 1955 reduction in the Mary
Mountain area may have started the downward trend shown between the counts of 1954 and1956. The marked decrease in population numbers in the Mary Mountain and Pelican herds, andthe smaller decrease in Lamar cannot be entirely due to the reductions of 1956; there was none in
Pelican. The decrease coincided with the severe winter of 1955-56, when snows were
exceptionally heavy in January, and severe cold was prolonged in February. A large winter loss
that year was indicated by sightings of 20-30 dead animals in Pelican during an aerial census oflate January 1956 (Jim Stradley 1968 pers. comm.). The following June, 32 dead animals werecounted in the main valley (Larry Brown 1969 pers. comm.). Reduction only added impetus,
apparently, to a natural occurrence.
Immediate increase in the Lamar numbers followed reductions when population levels remained
well over 200 animals, before 1952, by which time the last vestiges of the Buffalo Ranch
operation (feeding of hay) ceased. Since then, Lamar has shown only very slow increase,although reductions have been few and comparatively small. Reported natural mortality (anoccasional animal) indicated that no more bison than usual died most years. Slight increases
which showed in counts of 1956 and 1961 were followed by reductions each time. At least 50%of the 1962 reduction consisted of females (yearlings and older). After the 1965 reduction, only
nine females (yearlings and older) and 10 female calves were released. The temporary effect ofeven small reductions on low population levels was apparent, but some increase (withrecruitment of more breeding females into the population) expected by 1968 did not occur. Thissuggests that some factor, other than reductions, may have retarded increase in this population atlevels below 200 animals. The factor may be related to the change to a truly wild population,subject to natural environmental influences.
The Pelican population increased from near extinction about 1900 to an estimated more than 100

The Bison of Yellowstone National Park (Chapter 5)

animals in the early 1920s. It was subject to reductions only twice, in 1956 and again in 1965.
From the early 1920s through 1941, it fluctuated between counts of 100 and 200; for the next 10
years fluctuations were generally between 200 and 300 animals. After the peak count of 461 in
1954, followed by the drop to fewer than 100 in 1957, the population again remained between
100 and 200 animals. The lack of increase over fairly long periods of time suggests some balance
exists with environmental factors, in which factors favoring increase are usually offset bymortality factors such as winterkill. The 1954 peak may have occurred with exceptionallyfavorable influences, which existed only briefly.
The park-wide population counts do not suggest that periodic emigration from Pelican to Lamar
or Hayden Valley could account for the long-term stability, although apparently temporary
population shifts have occurred (see Mixing of Population Segments). No herd groups werereported in Hayden Valley after 1895 until animals from Lamar were trucked there in 1936.
Ranger reports made prior to the study period indicate that reproduction by herd groups in Lamar
and Hayden Valley probably accounted for the usual population increases in those areas.
Population estimates for the entire park of 400 and 440 animals in 1967 and 1968, respectively,
showed a 10% increment for that period. Reduction effects and insufficient population dataprecluded calculation of annual increment over a longer period. Between 1965 and 1968, when
the study ended, the bison population for the park as a whole showed only slight increase. Three
years had elapsed since a major reduction, and 2 years since a small reduction. The apparent
increase in the Mary Mountain herd (Fig. 24) between 1966 and 1967 resulted from use of a low
actual count in 1966 rather than the more accurate estimate. In all bison population segments,
there is the suggestion of some factor or combination of factors retarding increase, aside from theinfluence of reductions.
Environmental conditions have continued to exert major influence on the bison populations inconjunction with the activities of man. Population trends (since the near extinction of the original
wild population about 1902) apparently reflect, initially, reestablishment of populations on
historic ranges which had been uninhabited by any bison for some years (Lamar, Mary
Mountain), or where the numbers were very low (Pelican). Increase was rapid under conditionsof semidomestication (Lamar), and when favorable environmental conditions combined withavailability of an extensive, uninhabited area (Mary Mountain). Later increases were apparently
offset by reductions (Lamar), or by reductions in combination with periodically severe
environmental conditions (Pelican, Mary Mountain). At lower population numbers, less severe
environmental conditions appear adequate to have offset increases and to have resulted in periodsof near stability or very slow increase in all population segments.
Presumably, the original wild bison population which inhabited the Yellowstone area throughout
the year lived in some balance with the prevailing environmental conditions of that time.
Fluctuations in numbers undoubtedly occurred as favorable conditions alternated withperiodically severe winters. The present environment of the bison ranges of the park appears little
altered by man's influence (with the possible exception of Lamar Valley), although the numbersof some of the predatory and grazing mammals have decreased. The bison population may be
expected to increase in the future (since population numbers of the study period are the lowest in
many years after the reductions of the 1960s), but may then establish a state of equilibrium withnatural environmental conditions.

chap5.htm

The Bison of Yellowstone National Park (Chapter 5)
Last Updated: 24-Jan-2005

The Bison of Yellowstone National Park (Chapter 6)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 6:

MORTALITY FACTORSParasites
Internal parasites
YELLOWSTONE BISON appear comparatively free from internal parasitism. During thepresent study, parasite investigation centered on the occurrence of lungworm (Dictyocaulussp.), as reported by Meagher (1966). Rate of infection for 185 animals examined was 11.4%.
Aged animals, with an incidence of 35%, showed the highest rate of infection, contrary to thesituation in cattle, where calves show both higher incidence and intensity of infections.
Dictyocaulus sp. has been reported from a few animals in Wood Buffalo National Park (Fuller
1961), from the National Bison Range (Locker 1953), from Elk Island National Park (Conner
and Cornell 1958), and from a fenced herd in Kansas (Frick 1951).
No other internal parasites were found in the brief examinations made of bison during thepresent study. Locker (1953) recorded only tapeworms (Moniezia benedeni) in Yellowstonebison, occurring randomly among all age groups, at an apparently low intensity of infection.
A variety of internal parasites which have been recorded from other bison herds have not beenfound here.
External parasites
External parasites were not collected from animals during the study period. Burger (1967a,
1967b, 1969 pers. comm.), who studied biting insects in Yellowstone during 1966 and 1967,
reported that mosquitoes (Aedes sp.), blackflies (or buffalo gnats), particularly Simulium
venustum, horse and deer flies (Tabanidae), snipe flies (Rhagionidae), and members of theMuscidae may all have had some association with bison. The last two families were mostimportant.
The genus Symphoromyia of the Rhagionidae apparently influenced bison distribution during
the summer months (see Summer Range Movements). These small gray flies cling
tenaciously, inflict a painful bite, and locally may be very abundant. During the summer,
bison are nearly naked, as the newly growing hair is very short, resembling fine, black plush.
They are particularly vulnerable to biting insects.
Three genera of Muscidae were associated with bison in Yellowstone. The stable fly(Stomoxys calcitrans) and the horn fly (Haematobia irritans) were observed feeding on bisonwith no noticeable effect. The face fly (Musca autumnalis) was first collected by Burger in
1967. He suggested that this exotic species, if it becomes established in Yellowstone, could
cause eye disorders in bison. He noted evidence of severe conjunctivitis associated with thepresence of this fly among bison at the National Bison Range.

The Bison of Yellowstone National Park (Chapter 6)

Diseases
Disease-caused mortality was not identified in the present wild bison population, althoughoutbreaks of hemorrhagic septicemia in 1912, 1919, and 1922 caused considerable mortality
in the introduced herd in Lamar Valley. In two instances during the study, young animals diedfrom causes which were not apparent when ample food was available. One was a yearling
female, observed by park personnel for some time, unable to keep up with the herd animals,
moving very little, and becoming gradually weaker. The other was a young cow, seen forseveral days at Old Faithful before she died. Both carcasses were nearly consumed byscavengers before examination was possible, but the fat-depleted bone marrow in both cases
indicated very malnourished animals. Neither tuberculosis nor anthrax, which have been
important causes of mortality in Wood Buffalo National Park (Fuller 1961; Choquette et al.,1966), have ever been detected in Yellowstone.
Brucellosis (Bang's disease, undulant fever in humans), caused by the bacterium Brucellaabortus, occurs in the present bison population. Whether the organism was introduced or wasendemic among North American bovids is not known; it was first tested for and reported in
Yellowstone in 1917. The rate of infection has varied considerably among tests made indifferent years during reduction operations, and also among the wintering populations of agiven year. In 1964-65, 129 animals tested in Lamar, 33 tested in Pelican, and 302 tested at
the Nez Perce Creek trap showed rates of 59, 42, and 28%, respectively (Barmore 1968).
Evidence suggests that brucellosis has little effect on the Yellowstone bison. Limited
examination of reactors slaughtered during the study period indicated normal pregnancies.
Rate of pregnancy was apparently not influenced, as discussed previously. Veterinarians who
investigated brucellosis in Yellowstone before the study period agreed that there were noapparent effects on the population (Tunnicliff and Marsh 1935; Skinner 1941; Quortrup
1945). Quortrup mentioned that few abortions were observed and gross lesions were rarely
seen at postmortem examinations. Dave Pierson, Buffalo Herder and Animal Keeper over a
period of 30 years, believed that observed abortions occurred as a result of the handling ofpregnant females in chutes, and their confinement in pens during the reductions held at the
Buffalo Ranch (1968 pers. comm.). Quortrup believed that brucellosis had probably existed in
the Yellowstone bison for a long time, and that they had acquired a natural immunity.
Investigations among bison have apparently concentrated on the incidence of brucellosis
rather than its effects. Most bison herds in the United States are maintained in a brucellosisfree condition as part of the U.S. Department of Agriculture brucellosis control program. In
Wood Buffalo National Park in Canada, where the presence of brucellosis was confirmed in
1956, Fuller (1962) considered it a possible influence on conception rate. Choquette et a!.
(1966) also assumed that brucellosis influenced productivity. Among cattle, effects include
abortion of calves, temporary sterility, and lowered milk production (Gilman and McAuliff1956).
Further studies of brucellosis in bison may indicate that mutual adaptation or equilibrium
exists, as between parasites and hosts that have long lived together (Allee et al. 1949).
Physiological effects of brucellosis, if any, may contribute to maintenance of the bison
population within levels which the habitat can support.
Brucellosis is of economic concern to cattlemen, and of health importance to the generalpublic. It is presumed that bison can transmit brucellosis to cattle, because the causative
organism is apparently the same in both species of bovids. Transmission tests have not been
made to verify this, but on the basis of the assumption, the National Park Service has
cooperated with the Department of Agriculture in brucellosis control among bison. In

The Bison of Yellowstone National Park (Chapter 6)

Yellowstone, cooperation has consisted of vaccination of calves and removal of reactors
during reductions (held primarily to cut herd numbers). This cooperation resulted in reductionof animal numbers below the park's management objective at Lamar in 1964-65. No
reductions have been held specifically for brucellosis control in Yellowstone.
Participation in brucellosis control in Yellowstone National Park has recently been reevaluatedby the National Park Service (Barmore 1968). Present bison management objectives are to
maintain a wild population under natural conditions. By order of the Superintendent of
Yellowstone National Park, future reductions will be held only when research clearly
indicates that compensation for a lack in natural controls is necessary. As an alternative to
brucellosis control within the park, the objectives of the Department of Agriculture control
program can be met by preventing contact between park bison and domestic livestock beyond
the park boundaries (see Movements Beyond Park Boundaries).

Predation
There was no direct evidence for predation on the present herd. Circumstances suggested agrizzly kill of an apparently healthy, mature bull in mid-summer of 1967. Remains of boneand hair indicated the bull died at the edge of a small group of trees in a meadow, south of
Hayden Valley. The lack of broken bones, the relatively young age of the animal, and the siteof death all suggested a grizzly (Ursus horribiis) might have killed the bull. McHugh (1958)
also mentioned indirect evidence of grizzly predation. Dave Pierson (1968 pers. comm.)
believed both black (Ursus americanus) and grizzly bears would take calves in the spring, butcalf counts during the study do not indicate much loss. However, such loss might haveoccurred at or immediately after birth, before the calves were observed with the cows.
Wolves (Canis lupus), which are known to prey on bison in Wood Buffalo National Park
according to Fuller (1961), are the only other likely predators of bison in Yellowstone.
Studies such as that made by Mech (1966) have indicated that effective wolf predation onlarge mammals results from the cooperative efforts of a pack. During the study period wolves
were rare in Yellowstone, with no pack activity.
The observed survival, for a long time, of handicapped or weakened bison provided additional
evidence that almost no predation was occurring. In one instance, a cow survived at least 2
years with a useless right foreleg. Although her mobility was impaired, she was usually withother bison, at times a mixed herd, more often with one or more bulls. Only once was she
seen unaccompanied, except for her calf of that spring. Solitary animals were also usually freefrom predation. Old bulls, obviously weak, were often observed for several winter months innearly the same location along the road in Lamar, until finally they died.
Historical information suggests that even during the early years of the park, when predators,
particularly wolves, were more numerous, healthy bison of all ages were relatively safe fromattack. Although predation becomes more difficult as the prey species decreases (MacArthur
and Connell 1966), the predators in this case had alternate prey (elk) to sustain their numbers
as bison decreased (from poaching). If bison had been easy or preferred prey, their increase,once they were protected from poaching, might have been prevented.

Other Causes
Winterkill, probably from the combined effects ofclimatic stress, forage availability, andphysiological condition of individual animals, wasThe Bison of Yellowstone National Park (Chapter 6)

the main cause of observed mortality (see Other
Mortality). Death usually occurred after prolonged
weakening, often in late winter (March and early
April). A few animals died annually, but the
number increased greatly with severe winters. Thissuggested that climatic influences (long winters,
periods of prolonged cold, deep and sometimes
crusted snow) acting directly and indirectly on thebison were the most important mortality factors.
The most apparent direct effect of the winterenvironment, above the energy levels required tomaintain body temperature, was the effort required
to travel between foraging areas. In deep snow themixed herd groups usually traveled in line,
plunging to create trenches several feet deep (Fig.
25), frequently for more than a mile. Variations in
topography crossed added to their efforts.

Fig. 25. Trench left in soft snow by travelingbison.

Observations during the mild and average winters of the study period indicated that snow
depth did not limit forage availability. Bison commonly cleared fairly deep snow (byswinging the head in a sideways motion) with apparent ease (Figs. 26, 27). McHugh (1958)
observed bison feeding in snow up to 4 feet deep. At higher population levels, snow depth
may limit access to forage. However, the size and location of the most used foraging areas
suggested that this might happen only under the most extreme conditions (see Use of Forage
Areas).
Susceptibility to winterkill varied according to physical condition, as would be expected. Agedanimals found dead in mild and average winters indicated that they were most susceptible.
Crippled and otherwise handicapped animals, and those weaker because of size, would also
be affected more quickly. Differential and total mortality among subadults, as discussed
previously, suggested that among otherwise healthy bison of all ages they were mostvulnerable. Size, together with social standing in the population (see Suggested Mechanismsof Population Regulation), may explain this.

Fig. 26 Bull bison foraging in snow
approximately 2.5 feet deep.

Fig. 27. Feeding site in snow
approximately 2 feet deep.

A quick-acting type of winterkill occurred once during the study period, but old bison bones
indicated similar occurrences in the past. During the severe winter of 1964-65, a group of 18
bison (including 3 calves, 2 mature and 1 spike bull, 7 cows of various ages, and 5
unidentified animals) died before the end of January at a small warm-slough area in theThe Bison of Yellowstone National Park (Chapter 6)

Bechler Meadows. The snow there, west of the Continental Divide, was too deep that winterto allow the animals to move away from the slough area, and presumably they starved todeath when the small amount of feed was gone. The slough area apparently becomes a uniquetrap in severe winters, since 13 other bison survived in Bechler that year, near the slough but
along the river banks where movement was possible in the open water.
Accidents accounted for the deaths of a few individuals of all ages nearly every year, as
indicated by ranger reports. Most commonly animals drowned in bog holes or fell into hotpools. The accidental death of whole groups while crossing thin river ice has been reported
twice. At Slough Creek in 1941, seven yearlings and 2-year-olds died. In 1946, near the Mud
Volcano, in the Yellowstone River, 39 died (including 5 calves, 9 yearlings, 6 two-year-olds,
2 mature bulls, 16 mature cows, and 1 unidentified animal).

chap6.htm
Last Updated: 24-Jan-2005

The Bison of Yellowstone National Park (Chapter 7)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 7:

HABITS
Calving
COMPARISON OF RECORDS kept during the study period with earlier informationsuggested that the onset of the calving season is later than formerly. From 1937 to about
1950, the first calves were regularly reported in Lamar before mid-April. Since 1950, firstcalves have all been reported later. McHugh (1958) reported that calving season extended
from 15 April to 31 May, with more births the first 2 weeks of May. During the study period
most births occurred during the first half of May, and calving season was over by the end of
May. There were always a few late births; occasionally a new calf was seen in late summer.
(Subsequent to this study, calving season has extended into June as the population has
increased.)
Fetal size information compiled before the study period also suggested that a large part of thecalving extended over a longer period of time. Rush (1932a) reported only that there wasconsiderable variation. E. R. Quortrup's unpublished data (Skinner 1941) indicated a size
range from a 2-inch embryo to a 23-pound, 22-inch fetus; 80% of them weighed between 5
and 20 pounds when examined in late January (Appendix V).
In all Yellowstone herds during the study period, most calves were born at about the sametime (early May). Observations of the earliest calves were rarely possible except in Lamar(because of limited access before 1 May), but the few records made by rangers for theFirehole suggested that first calves are usually born there perhaps a week later than in Lamar.
Calves were born on the wintering areas (Fig. 28), except for the occasional late one. In Lamar
during this study, most calving took place in the lower Lamar Valley (west of Lamar Canyon
in the area called the Horseshoe or Little America). Ranger reports predating the study
indicated that this same area was the usual place of calving. In Pelican, most calving occurredin the eastern half of the main valley from Astringent Creek to Raven Creek. Mary Mountainanimals calved in both Hayden and Firehole valleys. On the Firehole, most calves were bornin the Lower Geyser Basin areas of Sentinel Creek, Fairy Meadows, Pocket Basin, lower Nez
Perce Creek, and the Firehole Loop. Most Hayden Valley calving occurred in the western halfof the big valley, near Alum Creek.

The Bison of Yellowstone National Park (Chapter 7)

Fig. 28. Calves (a few days old) born about 1, May 1970, when snow was on the
ground later than usual. This cow was observed deliberately pushing these calves onto
their feet—an action not seen other years. Photo by Mike Sample.

Rut
Most breeding activity occurred from mid-July to mid-August. Field observations throughout
the study indicated that every year, for at least a part of that time, most of the herd groups
which wintered in Lamar and Pelican intermixed in the Upper Lamar area. At the start of therut in 1967, all of the animals were at the crest of the Absaroka Mountains on the eastboundary, between the Hoodoos and Canoe Lake. In other years the groups were more
scattered, some on the boundary and the adjacent ridges between Cache and Miller creeks,
and some on Saddle Mountain. By the last week of July or the first week of August, some ofthese animals crossed the Lamar River to the Mirror Plateau, where breeding activity
occurred from the meadows south of Amethyst Mountain south to the meadows at the
headwaters of Pelican-Timothy-Raven creeks. Most of the breeding activity in the Mary
Mountain herd occurred in the southwest corner of Hayden Valley and adjacent forest andmeadow areas. In all of these areas there were small uprooted conifers and many rubbed trees.
Small wallow-sized patches of grass (Fig. 29), apparently uprooted by morning but not muchused for wallowing, were another common sign of rutting activity.

The Bison of Yellowstone National Park (Chapter 7)

Fig. 29. Grassy spot uprooted by bison horning during the rut.

The period of breeding activity observed during this study (1963-68) was shorter than thatgiven by McHugh (1958). He observed in the much larger Hayden Valley population of thattime that the season extended from 15 June to 30 September, with less activity during the firstand last 2 weeks.

Movements
Migratory movements
Most of the bison in Yellowstone are migratory, moving in spring from the lower winteringvalleys to higher summer ranges, and reversing this altitudinal migration in the fall. The
migratory pattern was most apparent in the mixed herd groups which wintered in the Lamar,
Firehole, and Pelican valleys. Although all groups of a particular wintering area did not moveat once in spring, they all moved within a few days' time. Records kept during the study
showed that mixed herd groups wintering in Lamar moved 12-15 miles to higher areas of
Mount Norris and the Cache-Calfee Ridge during the first week of June, 3 of 5 years, and by
the last week of May twice. Firehole animals moved to Hayden Valley or the Little Firehole
Meadows area of the Madison Plateau during the first week of June, 3 of 4 springs. Winteringgroups began to move from lower to upper Pelican Valley at the same time. Some years,
further movement across the Mirror Plateau to the Upper Lamar area was delayed until midJune. Observations suggested that nearly every year the entire Pelican population, except somebulls, crossed to the Upper Lamar, returning to the Mirror later in the summer. Most
movements took place along definite travel routes, as shown in Figs. 30 and 31.

The Bison of Yellowstone National Park (Chapter 7)

Fig. 30. Map of the Lamar-Pelican area of Yellowstone National Park. (click on image
for an enlargement in a new window)

The Bison of Yellowstone National Park (Chapter 7)

Fig. 31. Map of Hayden Valley-Firehole-Madison Plateau area of Yellowstone
National Park. (click on image for an enlargement in a new window)

The bulls that wintered as solitary animals, or in bull groups, left the wintering areas graduallyduring the spring. The last of them disappeared several weeks after the mixed herd groups
moved. A few bulls were usually seen from the main roads in the Firehole, Hayden Valley, atMary Bay, and in Lamar Valley almost to the end of June. The bulls followed not only theroutes used by the mixed groups but moved upcountry along the various stream drainages toscatter widely on the summer ranges.
The cause of the spring movement was not clear. In 1966, an earlier spring than others of thestudy, the mixed herd groups moved from all three valleys by 24 May. In 1967, the Pelican
animals were observed sequentially from the air. They moved, in 2 days, the 15 miles fromthe new spring growth of the upper Pelican Valley, across high meadows, which were mostly
covered with snow or standing water, to the Lamar River. By the third day they were on thegreening slopes of Little Saddle Mountain. They did not follow any discernible vegetation orsnow melt sequence. Spring weather patterns and temperatures presumably influenced themigration. Dave Pierson (1968 pers. comm.), after years of observation, believed that warm
spring days were the main factor.
In the late fall the movement of mixed herd groups was reversed, but occurred less abruptly
than in the spring. Lamar animals appeared in the main valley (to stay) by late November.

The Bison of Yellowstone National Park (Chapter 7)

Some groups were reported in the Lower Geyser Basin about the middle of September mostyears, although the majority arrived in late October or early November. Pelican animals
moved down sometime in the first 2 weeks of November, although groups commonly
appeared earlier for a few days at a time when fall snowstorms occurred. This intermittent
shifting from summer to winter ranges during stormy periods in the fall was also seen in
Lamar.
Bulls commonly began to appear on winter ranges before herd groups were reported. The
movement was gradual, continuing for some time after herd groups moved in for the winter.
Most winters, a few solitary bulls stayed at sites high on the summer range, such as the heads
of Opal and Flint creeks.
Cold temperatures alone did not cause shifts from summer to winter ranges; immediately after
a fall storm, in temperatures often near 0°F, herd groups which had moved down returned tohigh elevations. Snow depth and exposure to storm conditions at the higher elevations
apparently caused both the temporary and the final fall movements to winter ranges.
Summer range movements
During the summer, there were extensive shifts of all mixed herd groups on the various
ranges. Animals which moved west onto the Madison Plateau from the Firehole, although few
in number during the study, commonly used the Buffalo and Little Firehole meadows in earlysummer. From there, they moved south along the Continental Divide onto upper Boundary
Creek and the western end of the Pitchstone Plateau, remaining in these latter areas un til thefall move to winter ranges.
Hayden Valley herd groups commonly stayed within the main valley much of the summer(Fig. 32). Other years, by July, they ranged the small meadows and parks scattered in theextensive lodgepole forest (Fig. 33) south to Dryad and Beach lakes, west to the upper
reaches of Spruce Creek, and across Mary Mountain to upper Nez Perce Creek. Bulls from
Hayden Valley occasionally moved south down Arnica Creek to West Thumb and on toward
South Entrance.

Fig. 32. Bison herd groups on Alum Creek in the western part of Hayden Valley.

The Bison of Yellowstone National Park (Chapter 7)

Fig. 33. Bison on the strip of sedge meadows along upper Alum Creek south of
Hayden Valley.

Pelican and Lamar wintering herds were seen in early summer on the lower ridges of theUpper Lamar (Mount Norris, the western ends of the Cache-Calfee and Miller Creek ridges,
and Little Saddle Mountain). By the end of June to mid-July, they moved higher, to the eastboundary (Fig. 34), ranging from the Hoodoos to Canoe Lake and Saddle Mountain. By late
July to early August, groups usually moved west down the ridges, and some crossed theLamar River to the Mirror Plateau, where they ranged the northeast rim from Flint creek toupper Raven Creek until the shift to winter range. At higher population numbers than thoseoccurring during this study, groups also commonly moved the length of Specimen Ridge on
the north edge of the Mirror Plateau (Dave Pierson 1968 pers. comm.).

Fig. 34. A herd group on the east boundary near Canoe Lake in early August. Photo by
John Good, Yellowstone National Park.

Apparent influences for movement of groups over large areas during summer were the rut,seasonal vegetation changes (see Use of Forage Areas), and, most obviously, biting insect
populations. Small, gray, biting flies were particularly noticed on the Mirror and the Upper
Lamar in 1965. In 1967, the flies were numerous in those areas, and in Hayden Valley also.
From mid-June to mid-August 1965, neither aerial flights nor ground checks showed mixed
herds on the Mirror Plateau, although in 1966 groups were seen there by 24 July. From midJune to early August 1967, herd groups were observed only once in Hayden Valley, but wereseen, from the air, to the south. Every year herd groups were seldom observed in Hayden
Valley during much of July when biting insects were at their worst.

The Bison of Yellowstone National Park (Chapter 7)

Burger (1967a) compared biting insect populations and animal distribution in 1966 and 1967.
He noted that the distribution and abundance of species of Symphoromyia, a small gray biting
fly, particularly at elevations below 8500 feet, was much greater in 1967. He suggested that
this influenced the concentration of the entire Upper Lamar population of bison groups highon the east boundary, at elevations of 9500-10,000 feet, for more than 2 weeks in late Julyand early August 1967. Other summers, although the same boundary area was used by bison,
they did not remain as long and were more broadly distributed.
Apparently, the insect populations influenced bison distribution and concentration morestrongly than did breeding activity. In 1966, with fewer biting flies, mixed herd, groups split
and moved from the Upper Lamar to the Mirror while the rut was at peak. In 1967, a similar
move did not occur until both the insect populations and the rutting activity began todiminish.
The spring and fall migratory habits of the Yellowstone bison did not prevent animals fromoccasionally visiting areas of winter range during the summer. Observations made during thestudy period and earlier ranger reports indicated that scattered bulls sometimes appeared on
all winter ranges. When population levels were higher, mixed herd groups also occasionallyvisited winter ranges for brief periods, according to ranger reports. Such groups weresometimes seen in the main Lamar Valley in mid-July, or more commonly, in August. Midsummer movements of groups rarely occurred to areas near roads in the Firehole. No groups
were reported near the main road through Hayden Valley in mid-summer, nor in the main
Pelican Valley. No reason for these mid-summer movements was apparent.
Winter range movements
During the winter, all bison (mixed herd groups, bull groups, and solitary bulls) moved shorter
distances and less frequently than in the summer. Movement was usually confined to thelimits of the wintering valleys (see Numbers and Distribution), with egress difficult if not
impossible after considerable snow had fallen. Mixed herd groups moved most frequently andfor greater distances, but sometimes stayed in one locality for days or even weeks. Bullgroups occupied smaller areas for longer periods. Solitary bulls sometimes spent the entire
winter at one site. Presumably, the amount of movement was usually related to group foodrequirements. Winter conditions hindered but did not prevent occasional extensive
movements by groups and single bulls between main wintering valleys. Reasons for suchmoves were not apparent, but forage requirements did not appear to be a factor. No
movements to areas of high summer range during the winter are known; the solitary bulls
wintering in these areas arrived in fall.
Mixed herd groups moved most frequently between Hayden Valley and the Firehole. In
January 1965, after attempts to drive animals from Hayden Valley to the Nez Perce Creek
trap with helicopters failed because of the above-average snow depths, most of the herd
animals crossed of their own volition a few days later. The following winter, during the 196566 reduction, neckbanded animals released from the trap were seen a few days later in Hayden
Valley. Before the present study, in March 1945, 54 bison traveled 6 miles across Mary
Mountain in 42 inches of snow, according to McHugh (1958). The frequency of suchcrossings, uninfluenced by reduction operations, was unknown.
Mid-winter movements between Lamar and Pelican valleys apparently involved only bulls.
Sometime between early December 1965 and mid-January 1966, a marked young bull crossed
from Lamar, presumably by way of the Mist Creek divide. Rangers reported movement on
this same route by bulls in February 1932 and January 1949. Jim Stradley (1968 pers.
Comm.) saw a few mixed herd groups crossing from Pelican into Lamar in early winter about
1955-56.

The Bison of Yellowstone National Park (Chapter 7)

Movements between Pelican and Hayden valleys apparently occurred in the fall and early
winter, but sightings were rare. The trails of solitary bulls were followed from the air in
January 1968. Mixed herd groups were reported only once during the study period east of the
Yellowstone River near the Mud Volcano, but earlier reports indicated an occasional group inlate fall. Jim Stradley (1968 pers. Comm.) observed from the air about two dozen cows andcalves moving between the two areas about 1956-57.
Movements beyond park boundaries
Since the early years of the park, few bison have moved beyond the boundaries (Appendix
VI). Figure 35 shows the locations of reported movements, which usually involved one ormore bulls. Most years some bulls summered beyond the north boundary. Since 1951, a few
bulls have been reported almost every year beyond the southwest boundary in Idaho. Thesemovements have occurred regardless of fluctuations in population numbers.

Fig. 35. Map showing known locations of bison movements across the boundaries of
Yellowstone National Park.

Mixed herd groups have only been reported beyond the north boundary of the park. Lateduring the winters of 1943 and 1948, groups briefly left the park near Gardiner, Montana.
Severe weather conditions partly influenced these moves. In summer 1943, nearly 150 bison
were seen just outside the northeast corner. In the fall of 1947, 31 were 8 miles north of theboundary on Elk Creek in the Hellroaring area (R. Murphy 1970 pers. comm.). All thesemixed-group movements occurred when larger numbers of bison wintered in Lamar.

The Bison of Yellowstone National Park (Chapter 7)

Mixing of Population Segments
Census records, aerial observations, and the limited records of neckbanded bison (Fig. 36)
indicated that movements of population groups affected numbers inhabiting the winter ranges
from one year to the next (population shifts), and resulted in interbreeding between
populations of wintering areas during the summer. Movement occurred during the fall andwinter between the valleys of the Firehole, Hayden, Pelican, and Lamar, as previously
discussed. Observations confirmed the assumption made by, park personnel some years agothat the extent and frequency of mixing between the Firehole and Hayden Valley animals
during most of the year, including the breeding season, justified considering them as one
population, called the Mary Mountain herd, distinct but not isolated from the other two herds.

Fig. 36. Neckbanded bison in a group at Pocket Basin on the Firehole. Photo by John
Douglass, Yellowstone National Park.

Shifts of other population groups were indicated by some fluctuations in actual winter counts
from 1935 to 1950 (Fig. 37). Decreases in Lamar winter numbers coincided with increases in
Pelican in 1937, 1941, and 1942; decreases in Pelican winter numbers coincided withincreases in Lamar in 1940, 1943, and 1949. Reductions, made only in Lamar during thisperiod, probably added to the amount of decrease there in 1941 and 1942, but could not haveinfluenced the 1937 decrease nor any Pelican decreases. Bias in Pelican population counts
made by rangers on winter ski trips might account for some variation, but not the coincidenceof changes in population numbers in the two valleys. Mixed herd groups which moved
between Lamar and Pelican in late fall and early winter probably remained on the winterrange that was in use when weather conditions worsened.
Shifts between Pelican and Hayden Valley
were infrequent and less obvious. Suchshifts did occur in 1941 and 1946 (Fig.
37). Other shifts have occurred since, but
the less frequent population counts madeafter 1950 gave no indication. During thestudy period, aerial observations andreduction records suggested two shifts
occurred. Mary Mountain population
counts after the 1964-65 reduction totaled
fewer than the expected number ofThe Bison of Yellowstone National Park (Chapter 7)

animals, based on numbers seen before
trapping began (480), numbers removed(238), and possible natural mortality. A
move of animals to Pelican after the early
December count would explain thediscrepancy. The next winter, in the
reduction of 1965-66, 47% of the animals(yearlings and older) trapped at Nez Perce
had no metal eartags, showing they had notbeen trapped the previous year. A
movement into Hayden Valley from
Pelican was the probable explanation.
Apparently, the shifts indicated in Fig. 37
were temporary, usually for the one winter.
The presence of a mixed herd group (34animals) wintering in Bechler Meadows in
1962-63 also indicated this. No herd group Fig. 37. Population fluctuations in wintering areas causedby shifts of mixed herd groups.
was reported there in 1961-62 or 1963-64.
Over a span of time, the wintering
numbers of the Mary Mountain, Pelican, and Lamar population segments would be unaffectedby such shifts.
Observations of both total numbers of animals and individuals neckbanded in Lamar showed
that, during the breeding season, intermingling of the Lamar and Pelican wintering groups
was extensive most years. In 1967, all of them mixed together in several large, flexible groups
at the crest of the Absarokas for more than 2 weeks. The amount of interbreeding which
presumably would occur in such circumstances suggested that these bison also be considered
one population segment. However, because winter season movements were so few, theseparate designations were retained.
Separation was most complete between the Mary Mountain population and the Pelican-Lamar
animals. The infrequent movements between Pelican and Hayden Valley at any time, coupledwith the separation of the population segments during breeding season, resulted in almost nointermixing.
Historically, when there were large summering populations (parts of which wintered beyond
the park area) north of the Lamar and west of the Firehole, interbreeding between thewintering populations of the Lamar and Pelican valleys, and of the Firehole and Hayden
valleys, was probably less extensive because of geographic separation of some groups during
the summer. Then as now, however, the groups which shared summer ranges undoubtedlyinterbred. Before intensive poaching greatly reduced numbers and probably altered oreliminated habitual patterns of movement, there may have been more contact between Pelicanand Hayden Valley animals, but the amount of intermingling and interbreeding was probably

The Bison of Yellowstone National Park (Chapter 7)

least, even then, of the population segments.
Geographic separation during the breeding period through seasonal migration to higher
summer ranges, seen in the present park bison on a local scale, could explain the existence of
two recognized subspecies of bison in historic times whose distribution presumably
overlapped in the Rocky Mountains (Skinner and Kaisen 1947). Possibly the mountain andplains types jointly used some wintering places along the east side of the Rockies, but
breeding isolation kept the populations distinct.
The apparent temporary nature of group population shifts between main areas of winter range,
discussed previously, and neckband records both suggest that animals have affinities forparticular winter ranges. Neckband records for the Mary Mountain herd showed that someindividuals preferred one winter valley to the other, regardless of movement between the twovalleys at all seasons. The entire population (except for the many scattered bulls) had crossed
to the Firehole side during the winter of 1964-65 when helicopters drove them toward the trapon Nez Perce Creek. Most summered (1965) in Hayden Valley. Those in Hayden Valley
when trapping operations again began during the winter of 1965-66 were driven across to theFirehole side to the trap on Nez Perce Creek. Aerial observations after the trapping showedthat several bison, neckbanded and released, recrossed the divide to Hayden Valley
immediately. During the winter of 1966-67, when there was no trapping, five marked animals(neckbanded in 1965-66) wintered in Hayden Valley: an adult cow, a 4-year-old cow, a 2year-old cow, and two young bulls. Three marked adult cows wintered on the Firehole in both
1966-67 and 1967-68 although they were identified in Hayden Valley during summers. Less
complete records on other marked cows also suggest affinity for a particular winter range
although most mixed herd groups summered in Hayden Valley.
Records for the animals marked in Lamar further suggest that the tendency to winterhabitually in the same valleys was stronger among mature females. Marked animals of allages were seen on various parts of the summer range, including Raven Creek on the Mirror
Plateau (close to Pelican Valley), but only three immature bulls and two immature females
spent at least one winter in Pelican Valley. Cows marked as adults (five marked) wereidentified in winter only in the Lamar Valley, two of them for three successive winters.
A tendency for animals, particularly mature females, to prefer a given winter range might
explain the lack of any lasting interchange or permanent shifts by groups from one winterrange to another. The lack of emigration to new territory, such as from Pelican to Hayden
Valley before the reintroduction of 1936, might also be explained. Possibly, except for young
animals or old bulls, interchange between wintering valleys involved only groups. Although
the basis of such groups is not known, observers generally agree that a group structure exists.
Fuller (1960) believed there was a unit of some sort. McHugh (1958) believed the groups
were flexible and depended little on blood relation. He did observe that cow (mixed herd)
groups were usually led by mature females. These cows would then govern the movements
made by the groups.
Bison have shown willingness to move considerable distances in rough topography or deepsnow, according to the time of year, but they do not all intermix freely. Their movements
follow repetitive patterns which indicate habit as well as physical need. The movements ofboth individuals and groups result in a varying amount of separation among population
segments which winter in the valleys of the Firehole, Hayden, Pelican, and Lamar (Table 16).
The Yellowstone bison of the present (and recent past) remain almost entirely within the park
boundaries throughout the year. Those that range to the northeast (Lamar and Pelican) arealmost separate from those designated the Mary Mountain herd. Affinities for given winterranges are responsible for much of the separation, which is reinforced by migratory habits
which maintain a breeding season isolation. Occasional movements by bulls and mixed herd

The Bison of Yellowstone National Park (Chapter 7)

groups prevent total separation of any one part of the population.
TABLE 16. Comparative summary of movements shown by the present wintering
populations.

Firehole-Hayden
Valley Populations

Pelican-Lamar
Populations

WinterPartialAlmostAlmost complete
separation
completeGroup
Frequent - year around Least frequent - Infrequent - fall and early wintermovement
fall and early
between valleys
winteraSeasonal
migrations
Summerinterbreeding
Amount ofmovement onsummer range
Amount ofmovement on
winter range
Movement
beyondboundaries
Summary:
Population
separation

Less marked

Quite marked

Complete

Complete

Range less widely(except Madison
Plateau)
Varies among herd
groups, bull groups,
and solitary bulls
A few bulls, SW corner

Range widely

One population: Mary
Mountain

Varies among herd groups, bullgroups, and solitary bulls
A few bulls, N&E boundaries,
summer; herd groups, N
boundary, winter
Almostseparate

One breeding population, withwinter range designations as
Lamar and PelicanaApplies to relationship between Hayden and Pelican valleys.

Food Habits
Results of analysis of 22 rumen samples, half of them collected in the winter and halfthroughout the rest of the year, are shown in Table 17. The 1-quart sample taken represented
approximately 1% of the rumen-reticulum volume of 91 quarts averaged from eight adultmales. Approximately two-thirds of the samples were taken from adult males. Because ofsome uncertainties in distinguishing between sedges and some grasses, doubtful material wasplaced in the grass category. Sedge may thus be underrepresented in the analysis.
TABLE 17. Food habits as indicated by rumen sample analysis.

Winter Spring
11
4

Fall
3

Total
22

The Bison of Yellowstone National Park (Chapter 7)

Species
Grasses and grasslike plants
  Sedge  Grasses
  Wire rush  Spike-sedge
Forbs  Phlox  Northwest
cinquefoil
  Sulfureriogonum
  Dandelion
  Pussytoes
  Groundsel
  Shrubby
cinquefoil
  Clover  Onion  Blue-eyed Mary  Unidentified
Browse  Big sagebrush  Red dogwood
  Raspberry  Dwarf
huckleberry
  Serviceberry
  Fringed
sagebrush  Unidentified
Lodgepole pine
Horsetail
Moss
LichenUnidentified

samples samples samples samples
Comp.
Comp. Freq. Comp. Freq. Comp. Freq. Comp.
Freq. %
Freq. %
%
%
%
%
%
%
%
%
100

99

100

96 10091 10099 100

96

100
100
100
-45
18

56
34
9
-trace
trace

100
100
100
-100
75

49
46
1
-3
2

50 10032 100
8 100
1
-6 67
trace
--

37 10030 10032 91-9trace 68
-- 27

51
35
10
trace
2
1

--

--

25

trace 100

6

--

--

23

1

9

trace

100

trace

75

trace

33

trace

36

trace

73
---

trace
---

-75
--

-trace
--

75
-75

trace
-trace

33
---

trace
---

32
14
14

trace
trace
trace

18

trace

--

--

--

--

--

--

9

trace

----82
36
45
9

----1
1
trace
trace

---25
75
50
---

---trace
trace
trace
---

50
25
-75
50
--25

trace
trace
-trace2--trace

--33
33
67
----

--trace
trace
trace
----

9
5
5
23
73
27
23
9

trace
trace
trace
trace
1
1
trace
trace

--

--

--

--

25

2

--

--

5

trace

--

--

--

--

--

--

25

trace

5

trace

9

trace

--

--

--

--

--

--

5

trace

45
18
18
9
-36

trace
trace
trace
trace
-trace

25
75
25
-25
75

trace
trace
trace
-trace
trace

-50
25
25
-50

-tracetrace
trace-trace

67
33
-33
-33

trace
trace
-trace-trace

36
36
18
14
5
46

trace
trace
trace
trace
trace
trace

100
100
100
50
100
25

Trace indicates less than 1% composition.
Material is ranked according to composition by volume, in the total diet.
Composition totals of less than 100% are the result of rounding to the nearest percent.
Grasses and grasslike plants formed most of the diet throughout the year. Totals were 99, 96,

The Bison of Yellowstone National Park (Chapter 7)

91, and 99% for winter, spring, summer, and fall, respectively. Sedge was the main source of
forage at all seasons, averaging more than half the diet. Its value in winter (56%) reflects theanimals' frequent concentration during this season on sites where nearly all the plant growth issedge. Grass, second in quantity during all seasons except fall, averaged more than one-thirdof the diet for the entire year. Its highest value (46%) in spring probably reflects both greater
palatability and increased availability of new spring growth. Wire rush was taken yearlong,
but averaged approximately one-third of the fall diet.
Both forbs and browse were represented throughout the year in the bison diet, usually as trace
items. Forbs (mostly phlox) averaged 3% of the spring diet; northwest cinquefoil averaged
6% of the summer diet. Although forbs did not total a large percentage of the forage utilized,
they may be an important part of the diet nutritionally.
Browse was of least importance quantitatively, forming only 1% of the year's diet. Six species
were identified—four as trace values. Dwarf huckleberry represented 2% of the summer dietbut occurred in only one of the four samples. Its presence may be incidental to the summer
use of forested areas where it is common on the forest floor. Other browse plants shown in theanalysis may also be incidental to feeding at a particular site. Their possible importancenutritionally is unknown.
Forage composition data for the bison use areas represented by the food-habits analysis arelimited. Descriptions of species composition for the Lamar Valley are contained in Rush
(1932b). The Soil Conservation Service (1963) and Bergstrom (1964) provide somequantitative data. Descriptions of species composition and abundance at higher elevations of
the Lamar area were made by Oldemeyer (1966) and Woolf (1968). Hayden Valley species
are mentioned by Kittams (1949) and the Soil Conservation Service (1964). From thesesources and information obtained during this study, a list of grasses and grasslike plants wascompiled according to site (Appendix VII). Forage composition information for the thermalsites used by bison during critical winter periods (see Use of Thermal Areas) has not been
determined.
Wet bottomlands, creek banks, and pond edges support dense sedge growth (mainly Carex
aquatilis, beaked sedge, and Nebraska sedge). Slightly less wet sites support a greater variety
of sedges, horsetail, wire rush, and grasses such as sweetgrass, timothy (particularly inLamar), and tufted hairgrass.
Moist meadows of the wintering valleys have some of the same sedges (Carex acuta, C.
platylepsis, C. raynoldsii) found in the less wet sites such as swales. Smallwing sedge was themost commonly observed additional species. Horsetail, rushes, and additional grasses,
particularly bluegrass, are found. Giant wild rye is prominent in Lamar.
Moist and dry upland sites both support bluegrass species, Idaho fescue, and needlegrass. On
the drier sites, junegrass and various wheatgrasses occur in most areas; the sedge Carex
xerantica is common in Lamar.
At higher elevations on mountain herbland sites, sedges such as Carex raynoldsii andsmallwing sedge are prominent. Rushes, bluegrasses, Idaho fescue, mountain brome,needlegrass, wheatgrass, alpine timothy, and tufted hairgrass are all common. Subalpine
meadows have fewer sedges (mainly Carex raynoldsii and Hepburn sedge). Grasses are
predominantly bluegrasses and tufted hairgrass.

The Bison of Yellowstone National Park (Chapter 7)

chap7.htm
Last Updated: 24-Jan-2005

The Bison of Yellowstone National Park (Chapter 8)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 8:

HABITAT RELATIONSHIPS
Use of Forage Areas
OBSERVATIONS OF BISON use of forage areas indicated preferred locations and vegetation
types and suggested resulting influences on the populations. These were most apparent in
winter. Forage availability did not appear to be a population-limiting factor most of the time.
Conditions under which forage might be a limiting factor were suggested but not establishedby this study. Bison, in turn, influenced their foraging areas (see Effects on Habitat). Grasses
and grasslike species which commonly occur in some forage areas are listed in Appendix VII.
During the winter, most bison concentrated on sedge sites for their forage. At Soda Butte in
Lamar, 30 or more bison concentrated at times, and a few to a dozen bulls stayed all winterlong. Elsewhere in Lamar, mixed herd use concentrated along Slough Creek sedge bottoms
and in the many sedge swales west of the Lamar Canyon. Within the main or lower Pelican
Valley, study records showed that herd use was constant, much of every year, along thePelican Creek bottoms where snow depths permitted. In Hayden Valley, some years, themixed herds were seen almost all of the time along Alum Creek in the vicinity of Violet
Creek. In the Lower Geyser Basin, the extensive sedge meadows of Sentinel Creek, Fairy
Creek, and Fountain Flats were used most of the time by most of the animals. Use of thesesedge areas was facilitated by the ability of bison to forage in deep snow (previously
mentioned), and the influence of thermal activity on some of the sites (see Use of Thermal
Areas).
Use of specific upland sagebrush-bunchgrass areas on the winter ranges apparently varied
more from year to year. In 1965-66, on aerial observation flights, animals were observed mostfrequently on the north side of Pelican Creek, at the lower end of Astringent Creek, and to thewest for 2 miles. The next year they were usually observed on the slopes of the southeast edgeof the valley, in the vicinity of the old bridge over Pelican Creek. A third year they were in
the east end of the valley. Only three times during 30 years of ranger ski patrols and once
during the present study were mixed herds seen at the Mushpots-Mudkettles area of the upper
valley in winter, although they crossed this area in spring. In Hayden Valley one year, theherd groups, when not on Alum Creek, ranged the north-facing slopes of the hills on the southbank of Alum Creek. Another year they were located more frequently another mile or more
south, on the slopes and knobs in the southwest corner. Such differences in use of specificsites also existed on the Firehole and in Lamar. Presumably, varying patterns of snow drifting,crusting, and melting which affected forage availability influenced these shifts of use on
upland sites.
During spring, summer, and fall, bison use of forage areas concentrated less on any one placeor type. Use of sagebrush-bunchgrass sites increased particularly in the spring, but during all
three seasons bison were more commonly seen on swales and lusher meadows where sedge

The Bison of Yellowstone National Park (Chapter 8)

species composed much of the vegetation, even at high elevations. Use of forested sites forfeeding was usually limited to the more open growth and seemed incidental to otherinfluences (rutting activity, shade needs, escape cover, travel, escape from insects). At notime did forage appear limited during these seasons, either for the present populations or forthe higher populations of the past.
Observations indicated that although bison migrations between winter and summer ranges
were not caused by forage conditions, less extensive movements were influenced by changes
in plant growth. During the summer, with the additional influence of biting insect
populations, bison moved on upward on the summer ranges as the spring season reachedhigher elevations. Movement among the main use areas of swales and lush spots wasconsiderable, probably because these places were usually small in extent and widely
scattered, although numerous. Local movements at all seasons appeared influenced byinterspersion and size of foraging sites.
Information obtained during the present study did not indicate population levels at which
severe winter conditions might limit the forage available from the complex of sedge andupland sites. Present observations were limited to relatively low population numbers and weremade during mild and average winters. Observations and information from the present study
and earlier did suggest that bison numbers were related to use of specific thermal sites during
extreme winter conditions. Bison use of these sites may result from a combination of
temporary forage limitations on the preferred sedge and upland sites, the ability of bison toreach these sites, and the direct physical influences of prolonged cold or storm conditions.
Forage in these sites appeared quite limited; thus these sites may be a population regulation
mechanism influencing mortality according to the numbers of bison forced to use them andthe length of time they stay.

Use of Thermal Areas
Bison utilized wintering sites which were influenced by the widespread thermal activity in thepark. The amount of use varied with the size of the bison group (solitary bulls, bull groups,
mixed herd groups) and the kind of thermal influence. Thermal activity refers to sites where
thermal features (geysers, hot springs, fumaroles) are located. The ground at these sites isusually snow-free to some extent, and streams into which the features discharge hot water
may remain as ice-free travel routes for some distance from the activity. Additionally, there
are places where there may be no thermal features but warm ground results in small snow-freeareas or larger areas where snow does not accumulate as deeply as it would without thethermal influence (Figs. 38-41).

The Bison of Yellowstone National Park (Chapter 8)

Fig. 38. Snow-free bison feeding site on warm ground at the edge of Fairy Meadowsin the Firehole.

Fig. 39. The same site shown in Fig. 38, in early summer.

Fig. 40. Site along Alum Creek in Hayden Valley where warm ground causes snow tomelt early.

The Bison of Yellowstone National Park (Chapter 8)

Fig. 41. The same site shown in Fig. 40, in summer.

One to several bulls used sites of thermal activity(Fig. 42) more than larger bull groups and mixed
herd groups did, but these sites were not used by amajority of such bulls. Scattered bulls were
habitually found at various places in the Firehole,at the Mud Volcano in Hayden Valley, at Soda
Butte in Lamar, and at satellite areas such as
Ponuntpa Hot Springs, Violet Springs, and Mary
Bay in the Pelican country. But more than half ofthe bulls which wintered apart from the mixed
herd groups were located where there was neither
thermal activity nor the influence of warm ground.
Fig. 42. Bison bull wintering among active
geysers and hot springs.
Both Lamar and Hayden Valley had
proportionately more of the total number of thewintering bulls, as discussed previously. In both valleys, most of the solitary bulls and bullgroups were observed apart from any site of thermal influence.
Herd groups were seldom seen at sites of thermal activity but often used areas of thermal
influence, particularly sedge bottoms where snow depths were less (junction of Alum andViolet creeks in Hayden Valley (Fig. 43), Pelican Springs area of Pelican Valley, Lower
Geyser Basin areas on the Firehole). They used open streams such as the Firehole River,
Alum Creek, and parts of Astringent Creek (Pelican) for travel (Fig. 44), and fed on the sedge
growth of the banks while in the water (Fig. 45). Only in Lamar, of the four main winteringvalleys, were thermally influenced places little used by mixed herd groups; thermal activity isleast there (except Soda Butte).

The Bison of Yellowstone National Park (Chapter 8)

Fig. 43. Aerial view of the Alum Creek winter feeding area. Snow depths are less inthe darker places along the creek because of warmer ground.

Fig. 44. The Firehole River is open all winter because of an influx of hot water fromgeysers and hot springs along the banks. Photo by Karl Bittler.

The Bison of Yellowstone National Park (Chapter 8)

Fig. 45. Sedge growth along the banks of the Firehole River provides forage for bisonand elk moving in the open water.

Total use by all bison of areas where thermal influence alleviated otherwise more severe
winter conditions involved was more than the use of thermally active sites. In the Hayden,
Pelican, and Firehole valleys, the amount of use of sedge bottoms with lessened snow depths,
and of ice-free streams, indicated that thermal influence was important in maintaining
wintering populations. In Lamar, where winters are comparatively less severe, the lack ofthermal influences may not affect numbers of bison which can winter there.
Observations both before and during the study
period indicated that specific sites of thermal
influence where small, warm, snow-free patches
occurred, sometimes in conjunction with theactivity of a few hot springs or fumaroles, were ofgreat importance to the bison population during
brief but critical periods. During the prolonged
very cold spells of the severe winter of 1955-56,
Jim Stradley (1968 pers. comm.) observed mixed
herd groups in the scattered small, warm areas
west of Astringent Creek in the Pelican area, in the
Mud Volcano area of Hayden Valley, and just eastof the Firehole River (Pocket Basin) in the Lower
Geyser Basin (Firehole). During the study, herd
groups were seen in these same Astringent Creek
areas of Pelican (Fig. 46) late one winter (1968)
after a stormy period and presumably were there
the few other times they could not be located in theFig. 46. Bison in one of the scattered smallusual places. Winters (except 1964-65) were notthermal areas west of Astringent Creek in thesevere during the study period, and mixed herd
Pelican country.
groups were not observed at Mud Volcano nor in
Pocket Basin. The areas were not preferred by theherd groups, since use apparently was restricted to periods of severe conditions or late winter.
Forage appeared very limited in these areas and the period of use was usually very brief—a
few days or perhaps a week. In spite of very limited use, these areas probably represent themargin for survival of the herd groups in Firehole, Hayden, and Pelican valleys during theThe Bison of Yellowstone National Park (Chapter 8)

most extreme winter conditions.

Effects on Habitat
Effects on habitat as observed throughout the study period were considered from two points ofview: those which seemed to occur even under low population densities of bison, and thosewhich might have resulted from an ecological imbalance and overpopulation by bison. Bison
caused or contributed to five kinds of impact on their habitat: debarking of trees, formationand maintenance of trails and wallows, trampling of sinter rock deposits in areas of thermal
activity, and alteration of plant cover.

Fig. 47. Nearly every tree in this part of the lodgepole forest at the south edge ofHayden Valley has been debarked to some extent by rubbing bison.

Trees which were debarked and even girdled by therubbing and horning of bison in summer were notscattered throughout the bison use areas, but occurred incertain localities, apparently favored by both the mixed
herds and the scattered bulls. In extensive areas oflodgepole pine forest on the south side of Hayden Valley(Fig. 47), in groves on the lower end of the Cache-Calfee
ridge, and at a few sites on the Mirror Plateau, nearly
every tree had been rubbed to some degree. Elsewhere,
very small groves of trees located far from the normal
summer range of the mixed herds also showed hard use,apparently by one or more of the separated bulls. Rubbing
occurred during the period of shedding and regrowth of
hair, when biting insects were sometimes numerous, andextended on through the rut. Horning of trees by bulls,
more specifically associated with rutting activity, had even

The Bison of Yellowstone National Park (Chapter 8)more effect than rubbing (Fig. 48). Although many trees
survived years of this use, isolated trees and those near theedges of the forest were often killed. McHugh (1958)
found that in rare cases in Hayden Valley the tree line wasactually forced back, but that overall effects on
reproduction were minor. Patten (1963) concluded that elk
contributed to maintenance of an abrupt ecotone between
forest and meadows in the Madison Range (just west of
the park) but that forest areas were increasing slowly.
Similarly, the bison might impede, but not stop, theinvasion of the meadow areas by the forest, which appears
to be occurring.

Fig. 48. Bison horning effects on alodgepole pine.

Wallows, particularly those located in places where summering bulls commonly stayed or
traveled, were used year after year. Wallows were as much a feature of these areas as were thebison themselves (Fig. 49). Even after areas such as Blacktail Deer Creek were uninhabitedby bison for a number of years, the depressions left by the wallows could still be discerned,
although no differences between the vegetation within and around the depressions wereapparent. When situated on slopes, wallows sometimes formed focal points of erosion,
particularly in the shallow sandy soils of the hills in the southwest part of Hayden Valley. The
presence and continued use of such sites did not appear to be related to population levels;
some of these places were used before the present study (Kittams 1949) and show no change
in spite of greatly reduced bison numbers. Bulls were commonly seen every year and at allseasons on some of these sites, which suggested that as long as any bison inhabited Hayden
Valley these favored places received heavy use. Revegetation of favored wallows might occur
only without a bison population.
Trails used by bison, such as the network within Hayden Valley (Fig. 50) and thoseconnecting main use areas such as the Mirror Plateau and Upper Lamar, were also features
which appeared only indirectly related to population numbers. These routes were usedhistorically, as now, because of habits and distribution patterns.

The Bison of Yellowstone National Park (Chapter 8)

Fig. 49. Bull bison at a wallow which is used year after year.

Areas of thermal activity used by bison, where hot pools
and geysers are located, sometimes show breakage ofsinter deposits by trampling. Because the rock deposits
form slowly, the effects may be apparent for years. Mixed
herd groups used such areas infrequently and for brief
periods, according to the severity of wintering conditions,as discussed previously. Some wintering bulls used certain
thermal areas throughout the winter every year regardlessof changes in bison numbers.
Locations where debarked trees, wallows, trails, andtrampling of thermal areas were most noticeable were in
the Firehole-Hayden Valley part of the park. Before thepresent study, during the much higher bison populations of
the mid-1950s, these effects caused considerable concern.
The impact of the presence of bison was obvious, and may
have seemed especially striking because bison (except
perhaps a few strays) had been absent from that area for atleast 35 years and had not been present in any numbers forat least 50 years. Then, over a span of about 15 years, themarks of bison habitation became suddenly apparent, andincreased rapidly as the population expanded into thisuninhabited section. The resulting concern wasunderstandable, but perhaps exaggerated.
Observations made during the study period indicated thatdebarked trees, wallows, trails, and trampled thermal areas
were all effects which occurred at locations favored bybison for specific activities. The amount and distribution Fig. 50. A bison trail, one in a networkof such effects might increase somewhat at higher connecting the most-used parts of the
Hayden Valley area.
population levels, but not to the same extent as thenumerical increase. An assessment of such effects would
not provide an indication of what a desirable bison population should be in Yellowstone.
Bison effects on plant cover were apparent on foraging areas of the winter ranges where
habitat use is restricted by winter conditions. Observations indicated that effects on summer
range from use by the wide-ranging bison appeared less important than influences fromclimatic factors (late melting snow patches, late springs, short growing seasons) and edaphic

The Bison of Yellowstone National Park (Chapter 8)

influences (slope, soil, exposure).
During the present study, evaluations made of range conditions in Lamar, Pelican, and Hayden
valleys by the Soil Conservation Service (1963, 1964) indicated large areas of upland (usuallysteeper slopes and southwest exposures) in the poor and fair condition classes, producing lessthan 25% and 26-50%, respectively, of potential or climax vegetation. Soil erosion anddisturbance (particularly in Pelican and Hayden valleys) by animal trampling and rodent
activity was noted. Wetlands and subirrigated (a range classification term for some naturally
occurring moist sites) lands were in good to excellent condition. The condition of thesewintering valleys was attributed to use by elk and, particularly in Pelican and Hayden valleys,
to winter use by bison. An evaluation of the Firehole was not made by Soil Conservation
personnel, but general observations indicated that essentially the same conditions prevailed.
The effects which bison had on the vegetative cover of the winter ranges they inhabited, as theabove surveys showed, were mostly confined to upland sagebrush-bunchgrass sites. Both thesurveys and the present study indicated that the sedge-producing wet bottomlands and swales
showed little effect. Observations made during the study indicated that bison use, particularly
by mixed herd groups, occurred most frequently and for longer periods on these wet sites,
which were the main source of forage. The condition of the less-used upland areas suggested
that these sites were particularly vulnerable to impact and might remain in such condition inspite of varying patterns of use. Cole (1969) suggested that free-ranging elk would maintainupland areas in similar condition, which he termed biotic disclimaxes.
Information on the quantity and composition of the forage resources of the thermal sites usedby mixed herd groups under extreme winter conditions has not been obtained. Use of theseareas in stress circumstances (which occurred infrequently) rather than by preference suggeststhat although the forage resources appear very limited, the duration and intensity of use do not
permit destruction of the vegetation.
Several considerations suggest that the effects of bison use on winter ranges, clearly apparent
on upland sites, may not be greater than those which prevailed at the time the park was
established. First, the habitat of the main wintering valleys (except Lamar) has been little
altered by the activities of man, although animal numbers and distributions have beenchanged. Second, although the actual numbers of bison which originally inhabited the park
area throughout the year are not known, information from this study indicated that present
numbers, and those for much of the park's history, have been less than the original
populations which apparently centered on the various winter ranges.
Pelican Valley may indicate the extent to which present conditions represent the past. A bison
population has wintered there annually since the park was established (and probably long
before), it has been least disturbed by man (reductions), and historical sources provide limited
information on early habitat conditions. Jones (1875) wrote:
This prairie is the home of great numbers of field mice and moles [pocket
gophers], which have burrowed up the ground to such an extent that it is traveledover with difficulty.
The same comment could be made today, which suggests that the appearance of Pelican
Valley has changed little, regardless of the cause of that appearance. If the cause (bison use)
has not changed appreciably, present conditions in Pelican Valley may approximate thosewhich prevailed at the time the park was established.
The extent to which conditions resulting from bison use of the other wintering valleys may yet
resemble those of early times is less clear. In Hayden Valley, range surveys (Kittams 1949;
Soil Conservation Service 1964) attributed retrogressive changes in plant cover on upland

The Bison of Yellowstone National Park (Chapter 8)sites primarily to the effects of bison use. The absence of many bison for nearly 50 years
apparently permitted a trend toward climax vegetation; subsequent repopulation caused
marked retrogression which may represent reestablishment of conditions which wereprevalent with use by the original bison population. Conditions resulting from use by bison in
the Firehole may be comparable.
In Lamar, present effects of bison use probably represent more of a departure from early
conditions. Habitat disturbance by man has been greater, bison populations were maintained
in semidomestication for many years, and the area provides winter range for a morediversified ungulate population (elk; bighorn, Ovis canadensis; moose). The extent to whichbison use and resulting effects may overlap with that of other ungulates on this range ispresently being studied (William Barmore 1969 pers. comm.). Present low bison numbers
contribute minimal effects on vegetative cover compared with other influences, and havemuch less impact than in historic times.

chap8.htm
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The Bison of Yellowstone National Park (Chapter 9)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

CHAPTER 9:

SUGGESTED MECHANISMS OF POPULATIONREGULATIONBISON POPULATION NUMBERS have been regulated by both natural and artificial means
since the park was established. Regulation of the original bison population must have resulted
entirely from environmental and populational mechanisms. Regulation, to a varying degree,
has been imposed by man since near-extermination of the original bison. Limited knowledgeof original bison population characteristics, habits, and distribution, together with applicationof ranching methods to the plains bison introduced in 1902, has influenced subsequent
management practices. After 1952, all vestiges of artificial management, except reductions tocontrol population numbers, were eliminated. Reductions were continued at irregular intervals
to compensate for the alterations in natural conditions which were the accepted result of theestablishment and use of the park, and settlement of the surrounding country.
Information from the present study indicates that compensatory reductions are not necessaryon all population segments; the need for future reductions on any population segment is lessclear. Figure 51, which shows the known Pelican Valley wintering bison population from1902 through 1968, suggests that at least this part of the bison population has been regulated
for many years without interference by man. Since the time of intensive poaching in the
1890s, reductions have been made there only twice: 118 bison in 1956, 34 bison in 1965.
Following the near-extermination before 1902, the population increased gradually for nearly
20 years. Counts as shown are probably somewhat low, but suggest that a fairly stable
population existed for another decade. A general slow upward trend is evident from the early
1930s to the early 1950s, but the population remained near or below 300 animals until after
1952. Between then and 1954, when 461 bison were counted, there was a marked increase.
Subsequent low numbers by 1957 and thereafter seem inadequately explained by either
reductions or group shifts.

Fig. 51. Pelican Valley population numbers, 1902-68.

A complex of environmental influences probably is involved in what appears to be a naturally
regulated population. Emigration from the Pelican area has not been an important factor (seeThe Bison of Yellowstone National Park (Chapter 9)

Population Trends) in spite of the occasional temporary group shifts. Predation and disease,previously discussed, have been only minor influences. Environmentally influenced factors of
low reproduction rates compared with those of other bison herds, low increment rates in spiteof some increase in new-calf percentages following recent reductions, and heavy mortality
during exceptionally severe winters appeared most important in Yellowstone as a whole.
Presumably, the same factors apply to Pelican as a subunit.
Environmental effects, particularly the combination of low temperature conditions and snow
depths sufficient to require considerable efforts for survival, were not measured and weredifficult to observe, but were suggested by the differential mortality among sex and age
classes indicated by trap records. Survival rates of calves during the first year, compared withthe decreased rates among yearlings and 2-year-olds, suggested that calves, perhaps becauseof closer association with the cows, were not as stressed by environmental conditions.
Yearlings and 2-year-olds—less closely associated with a particular adult, and of smaller size
(particularly females) and less social standing compared with 3-year-olds—might be at a
disadvantage, less able to forage effectively and less able to travel in deep snow. McHugh(1958) observed a dominance hierarchy based on sex and age. He noted that calves derived
dominance from their cows, and that dominance was displayed in feeding situations and deepsnow travel. The stress on subordinate animals, as well as aged or otherwise weakened adults,
would increase with increasingly severe weather regardless of forage availability for theentire population. The relationship between numbers of animals, available forage, andmortality did not appear to be direct; forage quantity, although affected by snow depth anddistribution, exerted effects in combination with the physical stress imposed by snow depth
and storm conditions at low temperatures.
Figure 51 also shows a level below which the Pelican population has not dropped since therecovery (about 1935) from the low of 1902. Although only 88 were counted in 1957, noattempt was made to locate all animals (Jim Stradley 1968 pers. comm.). Thus, approximately
100 animals may represent the maximum population which could survive the most severe
winter, but perhaps a figure of 100-200 bison better represents a level around which thispopulation has fluctuated since 1935. That bison have survived, and at this population level,
in a valley such as Pelican in spite of severe winters suggests that a margin for survival might
be represented in parts of the Yellowstone environment which does not occur elsewhere.
The survival factor for bison in parts of Yellowstone may be the existence of thermal areas. As
previously discussed, thermally active areas do not attract large numbers of bison for the
winter, but the use of certain areas for brief periods—particularly at times of prolonged cold
combined with deep snow as observed by Jim Stradley, or in late winter as seen during thestudy period—may determine the lower limits to which the population numbers drop.
A comparison of the larger Yellowstone valleys (Table 18) gives further evidence on which
factors make habitation by bison possible. In addition to the previously discussed winteringvalleys, there are other large valleys in Yellowstone where bison herd groups apparently were
never known, historically or more recently. Extensive sedge bottoms are a feature of thevalleys used by bison; additionally, where winter conditions are consistently less severe, as inLamar, there are extensive open side hills of sagebrush-grassland which allow both movement
and feeding. Where winters are more severe, those valleys which have bison have either
extensive thermal or warm areas, or else many small ones among which movement ispossible. Some streams which remain unfrozen because of an influx of warm water are an
additional feature of most wintering areas, as are some river benches or valley side slopes andsmall hills (sagebrush-bunchgrass upland sites) which aid both foraging and movement.
Where too few of these factors occur together the valleys do not now, and probably never did,support mixed herd groups of bison.

The Bison of Yellowstone National Park (Chapter 9)

TABLE 18. Presence of factors which may affect suitability of habitat for wintering mixed
herd groups.

ValleySageMore
Bison
Warm Less
Sedge Grass
Warm
than Extensive
herd
open server
bottoms side bottomland 3 thermal thermalgroupsstreams climate
hills
sites

Antelope
small
CreekaBechlersmallBlacktailCougar Creek
small
areaa
Elk Park
Firehole+
Gallatin River
Gardiner area
GibbonMeadows
Hayden+ValleyLamar+
Norris area
Pelican+ValleySwan Lake
area

+

+

+

+
+

+
+
+
+

+

+

+

+

+

+

+
+

+

+
+

+

+

+

+

+

+

+
+

+

+

+

+

+

+

+

+
+

aNo bison present since mid-1950s.

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The Bison of Yellowstone National Park (Appendix 1)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

APPENDIX I:COMMON AND SCIENTIFIC NAMES OF PLANTS
Common nameScientific name

Alpine Foxtail
Alpine Fir
ArnicaBalsamroot
Barley, Meadow
Barley, Wild
Blue-eyed Mary
Bluegrass
Bluegrass, Alpine
Bluegrass, Canby
Bluegrass, Cusick
Bluegrass, Kentucky
Bluegrass, Sandberg
Bluegrass, Timberline
Cinquefoil
Cinquefoil, Northwest
Cinquefoil, Shrubby
Clover
Dandelion
Dwarf Huckleberry
Engelmann Spruce
Eriogonum
Eriogonum, Sulfur
Geranium
Giant Wild-rye
Groundsel
HorsetailIdaho Fescue
Junegrass
LupineMountain Brome

Alopecurus alpinus
Abies lasiocarpa
Arnica spp.
Balsamorrhiza sagittata
Hordeum brachyantherium
Hordeum spp.
Collinsia parviflora
Poa spp.
P. alpina
P. canbyi
P. cusickii
P. pratensis
P. secunda
P. rupicola
Potentilla spp.
P. gracilis
P. fruticosa
Trifolium repens
Taraxacum spp.
Vaccinium scoparium
Picea englemanni
Eriogonum spp.
E. umbellatum
Elymus cinereus
Senecio spp.
Equisetum spp.
Festuca idahoensis
Koeleria cristata
Lupinus spp.
Bromus marginatus

The Bison of Yellowstone National Park (Appendix 1)

Needle-and-Thread
Needlegrass
Needlegrass, Columbia
Needlegrass, Richardson
Onion
Phlox
Pine, Lodgepole
Pine, Whitebark
Pinegrass
Purple Onion Grass
Pussytoes
Raspberry
Red Dogwood
Rush
Rush, Long-styled
Rush, Slender
Rush, Wire
Sagebrush
Sagebrush, Big
Sagebrush, Fringed
Sedge

Stipa comata
Stipa spp.
S. columbiana
S. richardsonii
Allium rubrum
Phlox spp.
Pinus contorta
P. albicaulis
Calamagrostis rubescens
Melica spectabilis
Antennaria parvifolia
Rubus spp.
Cornus stolonifera
Juncus spp.
J. longistylus
J. tenuis
J. balticus
Artemisia spp.
A. tridentata
A. frigida
Carex pp.
aC. acutaSedge, Beaked
Sedge, Hepburn
Sedge, Nebraska
Sedge, Ovalhead
Sedge, Silvertop
Sedge, Smallwing
Sedge, Valley
Sedge, Woolly
Serviceberry
Spike-sedge
Sweetgrass
Timber Oatgrass
Timothy
Timothy Alpine
Tufted Hairgrass

C. aperta
C. aquatilis
C. athrostachya
C. nova
C. platylepsis
C. raynoldsii
C. xerantica
C. rostrata
C. hepburnii
C. nebraskensis
C. festivellaC. foenea
C. microptera
C. vallicola
C. lanuginosa
Amelanchier spp.
Eleocharis macrostachya
Hierochloe odorata
Danthonia intermedia
Phleum pratense
P. alpinum
Deschampsia caespitosa

The Bison of Yellowstone National Park (Appendix 1)

Western Bulrush
Wheatgrass
Wheatgrass, Bluebunch
Wheatgrass, Bluestem
Wheatgrass. Slender
Wheatgrass, Thickspike
Willow

Scirpus acutus
Agropyron spp.
A. spicatum
A. smithii
A. trachycaulum
A. dasystachyum
Salix spp

aNot listed its Booth (1050), but determined by him (1968 pers. Comm.)<<< Previous

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The Bison of Yellowstone National Park (Appendix 2)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

APPENDIX II:

SUMMARY OF BISON REPORTS PRIOR TO 1903,
YELLOWSTONE NATIONAL PARK AND VICINITY
SourceDate

ReportRaynolds(1867)

25 June 1860crossed Low Pass from Henry's Lake to the Madison(west of Yellowstone National Park) "We have seen one
band of buffalo among the hills,..."DeLacy(1876)

7 Sept. 1863

eastern side of Shoshone Lake "through scrubby pines,
without underbrush. There were many game trails madeby the wood buffalo, whose tracks appeared numerous
and fresh. We did not see any..."Haines(1968
pers.
comm.)

1860s

Potter(1962)

1867

south end of Yankee Jim Canyon (north of Gardiner,Mont.) "That whole flat would be covered with buffalo.""'all this buffalos',"

Cook, et al(1869)

3 October
1869

reference to Buffalo Pool, Lower Geyser Basin (Fireholearea) "in one spring we saw the entire skeleton of abuffalo..."Henderson(1870)

21 June 1870

Buffalo Plateau (north edge of park) "thousands ofbuffalo quietly grazing."

27 June 1870

upper Buffalo Creek (north edge of park) "All gameplenty—buffalo,..."

2 July 1870

Lake Abundance (just beyond northeast corner of park)"Thousands of bear, elk, buffalo, and deer."

17 July 1870

N. Fork of Clark's Fork (Broadwater River, east ofnortheast corner of park) "several beautiful parks, full of
buffalo,..."

22 July 1870

Cache Creek (Lamar area) "thro buffalo, elk & bear ... allvery tame."quotes local newspapers of the period as saying there wasa herd of bison in the Snowy's (north of park, part ofAbsarokas).

The Bison of Yellowstone National Park (Appendix 2)

24 July 1870

Specimen Ridge (north edge Mirror Plateau) "Buffalo ..."

8 August 1870

summit between Buffalo Cr. and Hellroaring (north edgeof park) "Saw several buffalo."

9 August 1870

head of Middle Boulder River (north of Park) "Thousandsof buffalo,..."

Doane(1875)

18 Sept. 1870

Old Faithful (Firehole area) "numerous fresh signs ofbuffalo..."Barlowand Heap(1872)

2 August 1871

Lower Geyser Basin (Firehole area) "Across the plain to
the west... mud springs in ravine... tracks of deer, elk andbuffalo..."Blackmore(1872)

1872

Lamar"B.H. informs me that this valley is a favorite resort ofthe mountain buffalo or bison. The hills on the left werethe last place that he saw the buffalo this spring followed
them for nearly 30 miles and captured during his hunt 7
young calves... informs me that the M.B. congregate inbands of from 5-30 rarely more altho he has seen 50..."

LeHardy(1873)

1873(about midAugust)"The valley of the East Fork [Lamar] extends Eastward
very straight for many miles, the floor... deeply covered
with grass. In this grass we saw in the distance quite anumber of Buffalo."Jones(1875)

1873

found bison bones embedded in soil at the bottom of acave at Mammoth

Dunraven(1876)

1874

general locale of Yellowstone National Park. "On thelittle prairies, open glades, and sparsely wooded slopes,
grazes the small mountain bison or buffalo, whose race
has also nearly vanished from the scene;..."

Grinnell(1876)

1875"The so-called 'Mountain Buffalo' was abundant in the
Yellowstone Park."

Supt.
AnnualReport(1877)

1875"Scores if not hundreds of moose and bison were takenout of the park in the spring of 1875,..."

1877

refers to the triangle of land with the East Fork (Lamar) as
the base, extending south 50 miles to the head of
Yellowstone Lake (Mirror Plateau, Pelican) "Here is stilla herd of three or four hundred of the curly, nearly blackbison or mountain buffalo."

Holmes(1878)

1878

Twin Buttes (Firehole area) "there are some upland parks
in which there are buffalo signs (the Mountain Bison)."Raymond1880?

"whitened skeleton of a mountain buffalo..." (in a hot pool

The Bison of Yellowstone National Park (Appendix 2)(1880)— Firehole area)

Supt.
AnnualReport(1880)

1880"Bison or Mountain Buffalo" "Bison, so called, in thePark, are somewhat smaller, of lighter color, less curly,
and with horns smaller and less spreading than those of
the bison that formerly inhabited the great parks ofColorado. They have also smaller shoulder humps, andlarger, darker brisket wattles. They differ materially fromthe buffalo of the Great Plains, being more hardy, fleet,and intelligent; their hides also are more valuable forrobes, as they are darker, finer, and more curly; and theseanimals are, in all probability, a cross between the twovarieties just mentioned.
"There are about three distinct or separate herds of bison
within or adjacent to the Park.
[north edge of park]"The first, numbering about two hundred, pasture insummer in the valleys of the Crevice, Hellroaring, andSlough Creeks, and the mountain spurs between them,descending, with the increasing snows, to winter in thedeep, sheltered grassy valleys of the East Fork [Lamar]of the Yellowstone and Soda Butte, and as the snows
melt, accompanied by their young, returning to their old
haunts.
[Mirror Plateau and Upper Lamar]"The second, numbering over one hundred, summer inthe elevated and abruptly broken, little-known section of
the Park, extending from the Hoodoo region to the Grand
Cañon, and from Amethyst Mountain to Pelican Creek,near the foot of the Yellowstone Lake, and winteroccasionally upon the East Fork [Lamar] of the
Yellowstone and on Pelican Creek. Their other winterhaunts are unknown.
[west side of park]"The third herd, numbering about three hundred, roams
in scattering bands. This season they were discovered
upon the Madison Plateau and Little Madison River.
Their winter haunts are unknown, though it is probablethey are on the Pacific side of the Continental Divide,
and, if so, they are not permanent occupants of the Park,and are therefore likely to be slaughtered by advancing
settlers.
"most keen of scent and difficult of approach of all
mountain animals."

Yount(1880)

1880"Here I purpose wintering [junction Soda Butte Cr.Lamar River] so as to protect the game, especially elk andbison, in their sheltered chosen winter haunts, from the
Clark's Fork and other miners."

Yount(1881)

1881[north edge of park]"The Slough Creek and Hellroaring bands of bison did
not venture near the cabin until February, nor did thoseof Amethyst Mountain at all;... I found... that a small

The Bison of Yellowstone National Park (Appendix 2)band of bison wintered on Alum Creek [Hayden Valley]
and another on the South Fork (Firehole River] of theMadison River;..."
Supt.
AnnualReport(1881)

1881

Mary Mountain area "It also greatly extended ourknowledge of the fire holes in those regions, and afforded
proof positive that a band of bison wintered there, at anelevation of nearly 9,000 feet."

BozemanAvantCourier(1883)

11 Jan. 1883

"at least one band of bison, containing four hundred..."22 Feb. 1883

There is a reference to the employment of hunters andmeat contractors by the Park Improvement Company.
refers to Lamar area
"Mammoth... Feb. 16... Hunting in the Park has been
stopped... parties... contract for Eaton & Co.... out, being
unable to get the meat through from Soda Butte... deepsnow... brought out a fine lot of buffalo meat... huntersand meat contractors were ordered in... in hot water."

Pierrepont(1884)

11 Sept. 1884

toward Lake Abundance from Slough Creek (north edgeof park) "Five miles to the eastward they ran upon a herdof buffalos numbering about a hundred and eighty, out of
which they killed seven..."Hague(1893)

1884"In 1884 I estimated the buffalo in the Park at 200;...

Livingston
Enterprise(1885)

winter1884-85"the herd of bison or mountain buffalo that has long
inhabited the Yellowstone

March 7

Mountain slopes and valleys was seen to number two or
three hundred in the Park this winter."

12 Dec. 1885

quotes New York Sun—George Bird Grinnell"There are, to my positive knowledge, not more than 700
bison... left... About 180 are in Yellowstone... I haveheard that twenty head were killed in Yellowstone Parkby a party of English tourists."

19 Dec. 1885

claims from a hunter "well posted" that there are 2 bands
in the National Park—1 of 40 on Souce (probably
Slough) Creek and 90 more or less between the forks of
the Madison—supposedly some of the 40 were drivenout of the park by use of explosives, and killed.

1885"The game in the Park had been shot with impunity andmarketed at the hotels... I succeeded in a measure in
breaking up the wholesale slaughter.... There issomewhere in the neighborhood of two hundred bison in

Supt.
AnnualReport(1885)

The Bison of Yellowstone National Park (Appendix 2)

the Park,..."
Supt.
AnnualReport(1886)

1886"stopped the wholesale slaughter of game...""From the reports... abundance of game [including
buffalo]..."

Supt.
AnnualReport(1887)

1887"A small number of buffalo still remain in the Park, but...
I am unable to state their number with any... accuracy.
My impression is that... they will not exceed one hundredin number. They are divided into three separate herds.
One of these ranges between Hellroaring and Slough
Creeks; in summer well up on these streams in themountains, outside the Park limits, and in the winterlower down on small tributaries of the Yellowstone,
within the Park. ... this herd... doubtful if it now exceeds
some twenty or thirty in number. ... Another herd ranges
on Specimen Mountain and the Waters of Pelican Creek.
... variously estimated at from forty to eighty. A traveler
on the Cooke City road claimed to have counted fiftyfour near the base of Specimen Ridge. A scouting party
which I sent out during the month of May found but
twenty-seven head of this herd, with four young calves...
The third herd ranges along the continental divide and ismuch scattered. A band of nine or ten from this herd wasseen several times this spring in the vicinity of the Upper
Geyser Basin. ... It is practically certain that none havebeen killed within the Park limits during the past two
years,..."

Supt.
AnnualReport(1888)

1888"During the early... winter... desirable... to secure someaccurate information concerning the winter haunts of thebuffalo ....
"The herd of buffalo which had passed a portion of theprevious winter along Specimen Ridge was notencountered, and the only buffalo encountered on the trip
were three in Hayden Valley. ... Early in April... a bandof buffalo were located in Hayden Valley and along
Alum Creek. ... a herd of buffalo numbering at least one
hundred had passed the winter on the divide between thewaters of the Madison and Yellowstone Rivers and in theadjacent valleys. Numbers of these animals have been
seen during the spring along the Fire Hole River and its
tributaries, and extended investigations have shown thatthey range in considerable numbers from Alum Creek, in
Hayden Valley, across the divide between the waters of
the Yellowstone and Madison Rivers and the Continental
Divide to Fall River Basin, in the southwestern part of
the Park. From the numbers seen and from the quantity
of 'sign' observed over an extended area, the number ofthese animals that range in this portion of the Park can be
estimated at not less than two hundred. ... The large
number of young calves and yearlings which have been
seen leads to the belief that a natural increase is in

The Bison of Yellowstone National Park (Appendix 2)

progress....
...
"During the past two years,... but little game has been
killed....
...
"Hunters, stimulated by the high prices offered bytaxidermists for specimens, are now lying in wait beyond
the borders of the Park ready to pounce upon any
unfortunate animal [ref. to bison] which may straybeyond it limits."
Supt.
AnnualReport(1889)March 1889

"to visit the warm-spring basins on the east side of
Yellowstone Lake, for the purpose of ascertaining
whether or not they were the winter resorts of thebuffalo. These basins.... well-nigh unapproachable,
except when the ground is frozen and covered with deepsnow,... successful in locating the buffalo in their hauntsof the previous winter near the hot-spring basins on thedivide between the waters of the Yellowstone andMadison Rivers. Although no buffalo were seen east of
the Yellowstone, it was evident from the abundant signs
that they habitually frequented the hot-spring basins inthis locality, some of the signs being quite fresh."

Supt.
AnnualReport(1890)

1890"I have no reason to believe that a single animal has been
destroyed. ... First in importance,... comes the buffalo. ...
enumeration... impossible. ... In the summer season they
are broken up into small bands and scattered over a wide
area of timber-covered mountains. ... In the winter the
deep snows drive them to the open country for food.
They are then found in large herds."

Supt.
AnnualReport(1891)

1891"Poachers""So long as there is no law within the Park for theprevention of hunting and trapping, it will be a mostdifficult matter to break them up.
...
"I am satisfied that both hunting and trapping are carriedon... from over the western border.
...
"I learn of three or four buffalo heads that have been
mounted in Bozeman,... I doubt not all of these were
killed within the Park, or very close to the line without it.
... fine ones are held at $400 to $1,000."...

May 1891"I haveabundant
evidence,
however, thatthe buffalo ...
are on theincrease.
Some tourists

The Bison of Yellowstone National Park (Appendix 2)

who went
through thePark in May
saw a herd ofabout 30, withseveral small
calves, near
the Trout
Creek lunch
station."July 1891"In July I sent
Wilson out
to... the westline... found
two smallbands ofabout 30 each,
one with 12 or
15 calves; inaddition hesaw several
single ones
and smallbunches. I do
not think it isexaggeration
to say there
are 200, andprobably there
are 400,
within thePark, and thatthey arethriving andincreasing."

Hague(1893)

winter 189192"the grazing-ground in Hayden Valley was visited by asnowshoe party, who counted the scattered bands,...
groups were generally small, and each contained agoodly number of calves. They numbered by actual countnearly 300, but there is no means of knowing what
proportion of the Park buffalo were then gathered here."

Supt.
AnnualReport(1892)

1892"I was informed that one Pendleton, a butcher andpoacher from Cooke City, had captured two buffalo
calves on specimen range, and had taken them across thenorth end of the Park,...
"there are certainly not less than four hundred here; ofthese about 20 percent were calves last year. This year,
also, the calves seem numerous and prosperous. The
great value placed upon them by sportsmen andtaxidermists makes their protection difficult,..."

The Bison of Yellowstone National Park (Appendix 2)

Hague(1893)

1893"That buffalo were among the animals inhabiting the
Yellowstone Park was known in the early days of its
history; ...The Park buffalo may all be classed under thehead of mountain buffalo, and even in this elevatedregion they live for the greater part of the year in thetimber. ... their habits are quite different from... thebuffalo of the plain, and it is most unusual, save in
midwinter, to find them in open valley or on the treelessmountain slope. They haunt the most inaccessible andout-of-the-way places,... living in open glades andpastures, the oases of the dense forest, often only to bereached by climbing over a tangle of fallen timber. ... therapidity of their disappearance on being alarmed. ... It issurprising how few buffalo have been seen in
midsummer, even by those most familiar with theirhaunts and habits. They wander about in small bands insuch unfrequented country as the southern end of theMadison plateau, the Mirror plateau, and the head of
Pelican Creek, and on the borders of that elevatedtableland known as Elephant Back. In winter, leaving theforest, they feed over the slopes of Specimen Ridge, andin the open Hayden Valley.
"It is not likely that there ever were many buffalo in thePark. ... If they ever roamed over this country in large
herds, evidence of the fact should be apparent by welltrodden buffalo trails, which nowhere form a feature of
the Park plateau. ... They occasionally wander beyond thePark Borders into Idaho and Montana with the first fall ofsnow, returning to their mountain homes with theapproach of spring."

Supt.
AnnualReport(1893)

1893"As the game diminishes in the adjacent States,
professional hunters and trappers become more bold andmore active. Montana, Idaho, and Wyoming all havestringent game laws, but in spite of them the game grows
rapaidly less. ... A stringent law, with severe penalties, is
one of the most urgent needs of the Park. ... Confiscationof the outfit, under existing regulations, has but little
effect, as the outfit is generally worthless. "I have pretty
reliable information that about a dozen buffalo were
killed last winter, and it is not improbable that even moreshared that fate. The heads of these were mounted. ...
"The buffalo have been seen often during the year, andthey appear to be doing well. In all the herds a fair
proportion of calves is found. Those killed have beenmostly bulls, so the capacity of the herd for increase has
not been diminished. Late in June a herd of fifty to sixty
crossed the road from west to east near the Riverside
Geyser. Thirteen calves were counted. They were... very
tame, and not the least scared by the soldiers who went
among them. The estimate of four hundred placed on
their number last year is surely not too high."Houghspring 1894

"We counted 75 to 85 head of buffalo in Hayden this trip.

The Bison of Yellowstone National Park (Appendix 2)(1894)

Supt.
AnnualReport(1894)... Sergt. Parker makes the Hayden and Nez Perce district
buffalo 81 head. Capt. Scott counted 103 head in Hayden
Valley one day three weeks ago. One band of 6 andanother of 7 head were seen in the Pelican country,... We
saw three head in Nez Perce Valley."
Hough states that Howell was killing cows and calves,and probably killed, during the winter, more than the 11
known killed at his capture in March, as he had been in
Pelican since September. Also Hough states 19 were
killed SW of the Park by Indians, fall '93; that 7 otherheads were offered to a Bozeman taxidermist; that 6 or 8
dead bison were found in Hayden Valley, "John Folsom
discovered ten head more of dead buffalo in that same
part of the country;" and that "I have track of several
other heads.""I think forty buffalo have been killed this fall andwinter, and no one knows how many more.""The buffalo do sometimes cross the divide about where
we did, and work between the hot country of Mary's
Mountain and this sheltered little valley. They have not
wintered on the west side of the divide in any numbers
for a considerable time.
"wild wall of mountains which we saw to the north of the
Yellowstone—so desolate and forbidding that evennow... there may be a few head of bison left over beyond
the Bison Peak—....
"I do not personally believe there are over 150 buffalo
left alive in the Park."
1894"not able to report any diminution of poaching..."(describes Howell poaching case, with Howell caught
killing 5 bison in Pelican, and his cache of 6 additional
heads).
"The dead bodies of 13 bison have been discovered intheir winter range. ... convinced they perished fromnatural causes.""Buffalo have been more carefully watched and moreaccurately counted than ever before. After deducting thelosses from all causes, I feel disposed to reduce myestimate... to 200,... A few were seen in their winterrange as late as the middle of June, and these had calves
with them."

NOTE: Garretson (1938) states that during the winter of 1893-94 most of the buffalo
were on the Madison Plateau, that 76 head were killed on the west side, and 40 head in
the Gallatin valley. He states that no more than 20 could be counted thereafter. He cites
no source for his statements, and while the poaching was undoubtedly heavy that year,
neither the losses nor the population figure afterwards were stated as fact by any of therecorders of the time.
Marble(1932)no datementions Dick Rock (of Henry's Lake, west of the park)
catching 5 calves.

The Bison of Yellowstone National Park (Appendix 2)

Murri(1968)no datereference to Dick Rock getting his buffalo calves in the
Bechler Meadows in early spring, known to have gotten a
pair.

Hofer
(1927)

approx. 1894or 1895"Hunters from the West Side were getting calves in theearly spring and heads in the winter. From near Gardiner
three young fellows killed a number in the basin. These
were the ones we found when I was with E. Hough..."(some of those presumed dead of natural causes).

Supt.
AnnualReport(1895)

1895"The act of May 7, 1894, seems to have had... effect upon
the poachers... those of the north, the east, and the south
sides have nearly... ceased.... I can not say as much for
the Idaho border. ... So long as the only herd of wildbison now existing in the United States is on the borderof this State. ... inquiry into various rumors of the killingof bison, either in the Park near the Idaho line or acrossit... convinced me that this last remaining herd is indanger of extinction by these people. ... I have goodevidence of the killing of at least ten less than two years
ago... prior to the passage of the protection act,... I haveundoubted evidence of the capture of three calves thisspring by a resident of Henry's Lake. ... There are rumorsof a herd of nearly one hundred having been seen in
Idaho outside the Park within the last two or threemonths.
[Comments that there was less snow than before known,that the large game could pass at will.]"the bison that have heretofore wintered in the Hayden
Valley were not massed there this year. The most seen
there in a single bunch... was about thirty. Small herds offrom three to four to ten were seen in widely separated
localities where they have not usually wintered. I feel
sure that many of them did not leave their summer range
along the Idaho line. [undetermined losses]... but I fearthat their number has not increased. ... estimate... two
hundred still remain."

Supt.
AnnualReport(1896)

1896"I... organized three parties for operations against the
merciless freebooters of the Henry's Lake country. ... The
ground covered by the buffalo in their summer range wasmost thoroughly gone over. Carcasses,... of about ten
buffaloes were found. ... One party of poachers was
encountered. ... I obtained information... buffalo scalps
for sale in the city of Butte.
"For some reason the main herd did not winter in Hayden
Valley as usual, and on the extensive scouts made by myorder during the winter months only about a dozen in all
were seen. They were scattered singly and in small
bunches over a large portion of the Park. Within the lastmonth [July] one party reported a small bunch of 3 in one
place, and of 12 in another. A second party reported abunch of 3 in a valley in a distant part of the park, andtracks of a herd of 8 or 9 more, but this herd was not

The Bison of Yellowstone National Park (Appendix 2)

seen. From reports received, I feel confident that the
majority wintered in the extreme southwest corner ofpark, in the Falls River [Bechler] meadows; and I alsofeel sure that there are now a considerable number east of
the Yellowstone River. ... fair certainty of the existenceof 25 or 30, and possibly of 50."
Snake
River
Monthlyreport21 Aug. 1897

"By way of Summit Lake. Saw sign of about 20
buffalo..." (Madison Plateau)

Whittaker(1897-99)

14 Nov. 1897

sign of 5, Mary Mountain area (Hayden Valley)

18 Nov. 1897

sign of 2, Astringent Creek (Pelican Valley)

Supt.
AnnualReport(1897)

1897"game, buffalo excepted, is increasing." The number ofbuffalo is estimated at 24.
"the buffalo remaining in the park are now scattered invery small herds at a number of points far remote fromeach other. They are mostly in rough rugged regions,...
...
"But very few buffalo have been reported this season.
The scouts, however, seldom see much sign in thesummer, and now the few remaining buffalo are scatteredand range in the most remote and inaccessible parts ofthe park in summer. I am confident of finding 25 thiswinter, when the snowshoe season sets in, and hope there
are nearly double this number in the park. Since Idaho
has forbidden the killing of buffalo... I have strong
hopes.. protect them from further slaughter by poachers."
The section containing instructions to stations recognizes
known buffalo haunts as: Mirror and Lamar, Hayden
Valley, and the Firehole area.

Soda Butte
State
Record19 Feb. 1898

reports wild buffalo

Morrison(1897-98)

Feb. 1898

refers to Mirror Plateau "across to Broad Cr up it to hot
springs near Fern Lake... Ponuntpa Springs to look for
buffalo. Found numerous signs of buffalo all around thespring and on both sides of Sour Cr. after followed themdown Sour Cr. to where a hot creek came down from a
hot mountain on the north which they went up, and aclose examination of the trail. ... [the trail was not madein single file but band was spread out] I estimate the bandas follows 4 calfs, 8 bulls, about 8 to 9 cows, but thinksome of the signs which I took for cow signs may havebeen 2 yr. old bulls. In all 21 head. Ponuntpa Springs is
an ideal wintering place for the band which is there as
there is no snow to speak of on the flat which is about amile long and 3/4 wide and is covered with hot springs

The Bison of Yellowstone National Park (Appendix 2)and hot creeks. ...
11 April1898

sign, estimateof 3, 4 miles
north of theUpper Basin,Firehole area

Lake
StationRecord21 June 1898

old sign—hot formations on Mary Mt.

Morrison(1897-98)

July 1898"head of Pelican Cr went west to a small creek that flows
in to Broad Cr. ... down Broad Cr about 2 miles thence
NE. to hot springs on Shallow Cr up Shallow Cr to
Wapiti Lake thence east to camp. Saw signs of 3 buffalo
fresh 2 on the small creek that flows into Broad creek
and one at Wapiti Lake."

7 July 1898

"left... head of Pelican Cr went down it 5 miles madecamp... went over to Fern Lake around it to head of Sour
Cr down it then followed buffalo trail fresh over ridge to
Broad Cr, up it to Fern Lake and on to Tern Lake... tocamp. Saw one buffalo jumped 5 buffalo near ford of
Broad Cr followed them to Fern Lake where we saw theone was on one of the heads of Sour Cr. an old bull.
Around Ponuntpa Springs there were fresh signs of theband I saw there last winter."

8 July 1898

5-6 buffalo wintered near forks of Pelican Cr., fresh signs

27 July 1898

one bull buffalo on top of Mary Mt.

14 Aug. 1898

buffalo signs near headwaters of Raven Cr. (Pelican area)
supposed to have been made within the last 20 days—
quite a bunch of buffalo hair was found at outlet of White
Lake

12 Sept. 1898

signs 1 bull 6 mi from W boundary

13 Sept. 1898

West Boundary headed for Summit Lake "3 m. east ofbound. near a little spring saw where 5 buffalo had
bedded over night, probably 2 bull a yearling and 2
cows."

30 Sept. 1898

a trip was made up the Lamar to Cold Cr. and Mist Cr.,over the divide to the head of Willow Cr. (Mirror Plateauarea) and down Raven Cr., up to Pelican, to Broad Cr.
and return to Pelican "will make special report on
buffalo"

Lake
StationRecordMorrison(1897-98)

Whittaker(1897-99)

The Bison of Yellowstone National Park (Appendix 2)Morrison(1897-98)

10 Oct. 1898

Mirror Plateau area
"fresh trail of 2 buffalo at head of Willow Cr. they came
down Mist Cr. to the mouth... evidently a cow and a
yearling from the tracks. ..."

Whittaker(1897-99)

12 Oct. 1898

refers to Mirror Plateau area "but after riding around theentire summer range i could not find any sign of themmet Scout Morrison... presume they have all left theirsummer range on Flint and moved to either the head of
Pelican Creek or Willow Creek where i saw some sign ofthem on my last trip... " (see date of 30 September 1898)

Burgess(1898-99)

18 Oct. 1898

Bechler area one, track

19 Oct. 1898

"went to [Bechler] River saw 2 year old buffalo tracks...""tracks of about 6 B They had been made 6 or 7 daysago."

20 Oct. 1898

Firehold to Fountain "saw the Buffalos had been goingalong the river to the L[one] Star Geyser."

10 Nov. 1898

Trout Cr. to head of Nez Perce Cr.
"I found two Buffalo tracks one Bull and cow"

13 Nov. 1898

"Then to East Fork of Pellican, where I saw the tracks of
one buffalo."

23 Nov. 1898

east side of Hayden Valley "Went East to Forest Springs.
found old signs of Buffallos... to worm formation at headof Moss Creek. found some fresh Buffallo tracks going
South... and down in sour creek where there is quite an
opening there I found where 4 Buffalos had beded thenight before, from there I went to... Cotton grass andSour Creek I saw 2 old Bulls one laying down they werevery wild, and ran back toward sour creek."

Supt.
AnnualReport(1898)

1898

estimates 50 yet in the park
"This is about the only wild herd in the United States,and steps should be taken to prevent the extermination ofthis herd from the evils of inbreeding..."Burgess(1898-99)

10 Jan. 1899

refers to Mirror Plateau area
"up East forks of Estringent [Astringent Creek] to Headof Bluff Creek. Then to White Lake. I saw two Buffalos
and a Great Many tracks, then went to Tern Lakes on the
East side of the lake saw four Buffalos Then we went toFern Lake. Saw 3 Buffaloes on the northwest End of
Lake."

11 Jan. 1899

"went up middle Estringent, over White Lake to head ofSour Creek, on this Creek I saw 15 Buffalos 12 old one
and 3 calfs. went down sour creek. ... On this same trip,
no sign was found in Hayden Valley.

The Bison of Yellowstone National Park (Appendix 2)

6 March 1899"... 2 Buffalo... wintering on snake river."9 April 1899

"went to Estringent Cabin"

10 April 1899

"I looked for the Buffalos, saw 20"

14 April 1899

"went to Trout Creek one buffalo on Crater Hill"

15 April 1899

"went to Fountain 5 Buffalos on Central Plateau"

Whittaker(1897-99)

12 May 1899"saw one Buffalo near the Base of Hell-Roaring Mountain
about a 4 year old...."

Lake
StationRecord1 June 1899

buffalo sign at Mary Mt.

Whittaker(1897-99)

15 Aug. 1899

"to the headwaters of Deep Creek and flint creek on the
mirror plateau to look for the Buffalo. could not see any
but found numerous sign..."Holt(18991901)

23 Sept. 1899

Snake River to Lake
"fresh signs of two buffalo..."8 Oct. 1899

"Buffalo passed within sight of camp..." (Thorofare area)

26 Nov. 1899

Ponuntpa area, Mirror Plateau"no fresh signs of Buffalo. found skeleton of calf."

Supt.
AnnualReport(1899)

1899"it is not known how many there are left or whether or notthey are increasing. I shall try and find out this winter asto their number. One of the scouts saw twenty-six last
spring, and signs were seen of others. It is probable that
there are fifty or more."

Supt.
AnnualReport(1900)

1900"Twenty-nine head of buffalo were counted by scouts last
winter, and there were possibly 10 more in the park thatwere not seen. Unless stations are located near the twosouthern corners of the reservation and the force of
scouts increased the buffalo will be exterminated in a few
years. With that addition to the facilities for protection
they can be preserved and will increase."

Supt.
AnnualReport(1901)

1901"it has been impossible... to ascertain accurately the
number of buffalo... but... as soon as the snow falls,...
The buffalo are now protected by the laws of Wyoming,
Idaho, and Montana, and it is now possible that the small
herd remaining in the park may increase, though it may
be necessary to introduce some new blood in this herd,
and possibly it may be well to start an entirely new one
and to keep it under fence, turning the animals loose
gradually as the herd increases. From what I can hear I
do not believe that there are more than 25 buffalo left in

The Bison of Yellowstone National Park (Appendix 2)

the park." (One bull was killed in Jackson Hole.)
Lake
StationRecord8 Dec 1902

patrolled to Pelican Country, 1 buffalo

Supt.
AnnualReport(1902)

1902"In addition to the large corral that has been constructednear the Mammoth Hot Springs, a small corral... on
Pelican... to capture therein the few remaining buffalo...
During the past Winter... 22 of these animals on the headof Pelican Creek, and there are probably a few more that
we were unable to find. This herd is exceedingly wild,
and will probably never increase in size, and may
possibly die out completely. It is thought that we cancatch up some of the young. ...
...
"It is our intention to feed and handle the new herd of
buffalo in the same manner as domestic cattle. ...

app2.htm
Last Updated: 24-Jan-2005

The Bison of Yellowstone National Park (Appendix 3)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

APPENDIX III:REPORTS OF WILD BISON 1903-19, YELLOWSTONENATIONAL PARK
SourceLake Station
RecordDate
19 Jan.
1903
15 Feb.
1903
26 Feb.
1908
24 Mar.
1903
25 Mar.
1903
12 May1903
Supt. Annual
springReport (1903) 1903
Lake Station
4 AprilRecord1904
end April

Reportreturned from Pelican
15 buffalo
Pelican country 1 buffalo (main valley)from Pelican 19 buffalo
from Pelican seen 17 buffalo
Pelican 19 buffalo"from Pelican Country... Had 2 Buffalo bull calves on toboggan
drawn by dogs. Saw 16 old buffalo and 3 calves."
2 calves captured from wild herd
located one buffalo at the hay stack (Pelican)

Scouts¡Pelican Valley—"seeing 11 Buffalo 5 cows and 6 bulls
no calves saw 6 dead ones"
Superintendent's 6 May
party that went out for buffalo calves report finding as follows...
Journal, 1903- 1904
11 live buffalo 5 dead buffalo¡4 old ones and 1 yearling21(additional report of one old bull dead between Lake and Thumbrefers to one of the three Goodnight bulls which was turned out)
18 May party returns, having captured one female calf on the head of
1904
Sour Creek; they saw twelve live buffalo; men at Canyon station
saw two in Hayden ValleySupt. Annual
springremnant located on the head of Pelican Creek. "three calves have
Report (1904) 1904
been caught up from the wild herd... Two of these are males andone is a female." (the two males were those caught the previous
year)
Supt. Annual
1905"now about 30 of these animals left,... on the head of Pelican
Report (1905)
Creek."
Supt. Annual
probably sign of 15, Mirror Plateau and Specimen Ridge; signs of 6,
Report (1907) summer Madison Plateau.
Aug. 1907 4 seen in Hayden Valley
total estimated to be 25

The Bison of Yellowstone National Park (Appendix 3)

Scout Monthly 1 April
Reports (1908) 1908
13 April
1908
16 April
1908
13 July1908
7 Sept.
1908(approx.)
16 Sept.
1908
9 Oct.
1908
11 Oct.
1908
Supt. Annual
1908
Report (1908)

2 bull buffalo, Pelican Valley (near Raven Creek)
followed buffalo trail up Lamar to mouth of Mist Creek, saw 10
buffalo, 2 of them yearling calvessign as far down the Lamar as Miller Creek where buffalo had
been feeding
9 including 1 calf on upper Lamar"Patrolled west to Buffalo Lake, then south to 10 miles... saw...
signs of buffalo" (southwest boundary)patrolled northeast to Mist Creek and camped. 18 miles Saw 20
wild buffalo (apparently at the Mushpot-Mudkettle area on
Pelican Creek)
11 seen (on trip through Willow-Mist-Upper Pelican Creeks of
the Mirror Plateau)saw 7 head buffalo at Pelican Bridge (this report, as well as laterones for the immediate vicinity of Lake may refer to the
Yellowstone Boat Co. animals)"Wild herd: Reports from scouts and patrols state that signs of
two buffalo calves were seen on Mirror Plateau and one cow
and calf were seen in Pelican Valley during the season. Scout
Wilson reported that he saw 10 buffalo at the mouth of Mist
Creek on Lamar River on April 13. On September 7 Scout
McBride saw fresh tracks of 2 buffalo on Boundary Creek, near
the western boundary, and on September 16 he saw 20 buffalo
near the mush pots southwest of Pelican Cone in the valley of
Pelican Creek. From these reports it is evident that the remnantof the original wild herd is gradually increasing in numbers."
used a figure of 32 counted.

Skinner and1908
Alcorn (194251)
NOTE On October 15, 1907, the Yellowstone Lake Boat Co. E. C. Waters corrals at Lakewere torn down and the 8 buffalo within released. The Lake Station Record for the next two
years and the scout diaries indicate that the various sightings of buffalo west of Lake Station,
between Lake Station and Mud Geyser, and from Lake to Pelican Creek Bridge and east
along the lakeshore for several miles were probably these animals. Reports of animals seen,or sign thereof, for these areas in 1908-09 are not included as part of this summary. Four orfive buffalo were rounded up at Lake to be driven to headquarters in early December of1909. North of Canyon, with average snow depths of 4 feet, the buffalo broke away. Whenlast reported they had gone down into the Yellowstone Canyon to feed, apparently in thevicinity of Seven Mile Hole, where survival would be unlikely. Probably any left near Lakedisappeared one by one without ever mingling with the wild herd. There was no indicationthat they ever joined the tame herd, of which very close track was kept at this time. The Boat
Co. animals were of Goodnight plains bison stock, brought to the park in 1896, and kept incorrals (Timmons 1962).
Lake Station
15 & 16 patrol to Astringent Creek and White Lake, buffalo sign seen
RecordJan. 1909
23 March patrol to Astringent Creek cabin and White Lake, 3 buffalo seen1909
24 March sign at the Mushpot area on Pelican Creek

The Bison of Yellowstone National Park (Appendix 3)

1909
Scout Monthly 15 April
Reports (1909) 1909
16 April1909
17 April
1909
Supt. Annual
April
Report (1909) 1909

4 buffalo near Yellowstone Lake, very thin (these may have beenpart of Boat Co. animals, 6 were driven across the Pelican
Bridge in Nov. 1908)
Astringent Creek to Mist Creek and Lamar and to Willow Creekcabin, saw 3 buffalo near cabin
patrolled north to Soda Butte, saw 2 buffalo"Another small herd of 9 was seen near Pelican Creek in April."(this may be an error, representing the total of the above-listed
trip)
Scout Monthly mid-May "trying to corral 9 wild buffalo near Cache Cr. We captured 1
Reports (1909) 1909
buffalo bull calf"
Supt. Annual
May 1909 "A herd of 11 wild buffalo was seen on Cache Creek May 19, at
Reports (1909)
which time a "bull calf was caught..."Anonymous
15 May lists 10 at the mouth of Cache Creek—2 large bulls, 7 cows, 1File No. 21 & 1909
calf
22, 5/28/09
Supt. Annual
July 1909 "Signs were also seen in the southwestern part of the park in July
Report (1909)of this year."
Lake Station
23 Dec. Buffalo signs seen at Squaw Lake (Pelican area), 23 buffalo seen
Record1909
near Pelican Springs
13 Jan.
buffalo signs 2 mi. west of Steamboat Sp. (Yellowstone Lake,
1910
north edge)
Scout Monthly February Soda Butte to Cache Creek and return, saw 5 buffalo and signs
Reports (1910) 1910
of buffalo.
Anonymous
23 Feb.
29 buffalo seen on Pelican Creek (states group known not toFile No. 21 & 1910
contain the Boat Co. buffalo)
22, 3/2/10
Supt. Annual
1910"A herd of 29 wild buffalo was seen in Pelican Valley on
Report (1910)
February 23, and a small herd of 5 was seen on Cache Creek on
February 3. One old bull died during the winter in the vicinity of
Yellowstone Lake,..." (the one may have been from the BoatCo.)
Lake Station
9 March (Pelican Valley) "seen 20 of them"
Record1910
16 March from Park Point (Yellowstone Lake) to Pelican Creek, 6 buffalo
1910
17 March from Astringent Cabin to Lake, 21 buffalo.
1910
30 June Lake Station to 14 mile post, Sylvan Pass Rd., saw 7 buffalo
1910
Lake Station
17 Feb.
patrol to Pelican Cr., 20 buffalo
Record1911
Anonymous
Feb. ?
part of wild herd sighted recently, sure of 20, think 25 including
File No. 21 &some calves22, 3/14/11
Lake Station
2 March to Pelican Cabin, 25 buffalo
Record1911

The Bison of Yellowstone National Park (Appendix 3)

Scout Monthly 28-30
Reports (1911) April
1911

from Signal Point (on Yellowstone Lake) north to Astringent
Creek, saw 27 wild buffalo of which 2 were calves, traveled toMist, Cold, and Willow Creek cabin N. to Lamar River, "sign of
one wild buffalo"
NOTE: During June 1911, 4 bison were rounded upon the Madison and brought toMammoth, in the mistaken belief that they were Yellowstone National Park animals. They
were returned, including offspring, to their owners (Sherman) at Henry's Lake in June 1913
(Scout Reports and File No. 21 & 22).
Nowlin (1912) 1911
comments droppings indicated buffaloes had ranged near Saddle
Mountain and on Mist Creek and the upper Lamar River; plentyof old signs along Pelican Creek, at White Lake on the head ofSour Cr., and near the heads of Deep Creek.
Thumb Station 10 August "patrolled to K. W. & De L. C. Reg. 82—8 buffalo" (contrary to
Record1911
the Supt. Report, 1911, the 8 buffalo were probably seen at theKnotted Woods, southwest of Dryad Lake, rather than west of
Thumb at DeLacy Creek)
Supt. Annual
1911"The wild herd has been seen several times, usually in theReport (1911)
Pelican Creek Valley. The largest number seen at any one timewas 27. A patrol reported having seen 8 along the road, about 7
miles west of Thumb Station, on August 12." (error, see above)
Anonymous
13 July48 (inc. 10 calves) on Raven Creek "Scouts McBride and Little. .
File No. 21 & 1912
. report having actually seen and counted 48 animals. They are22
not together in a herd, but are considerably scattered, mostly on
5/3/12
Pelican Creek, Upper Lamar River and tributaries." count
7/19/12included 10 this year's calves; one additional large bull on the
Pitchstone for a total of 49
Scout Monthly 6 July
1 bull, signs of 1 more, Cache Cr. (may have been from tame
Reports1912
herd)(1912)
7 Julysign of a small band, between Cache and Willow Creek
1912
8 Julysign of 6, Willow Cr. (seen by another scout)
1912
9 Julyfresh sign, vicinity of Mist Cr.
1912
10 July
1 bull, signs of others, Mist Creek.
1912
11 July
fresh sign, Mist to Raven Creek. (one seen by another scout)
1912
12 July"patrolled county" (Mirror Plateau), saw 38: 25 cows, 3 bulls, 10
1912
spring calves, one seen between Snake River and Aster Creek
22 Julysaw buffalo signs on Proposition Creek
1912
Nowlin22-30 July trip made on Specimen Ridge and Mirror Plateau, upper Lamar(1912)
1912
River, Saddle Mt., Miller and Cache Creeks; fresh sign cow &calf Upper Pelican, tracks and droppings at head of Raven
Creek, about 10 days old
saw about 10 at the head of Timothy Cr., followed them to theheadwaters of Clover Creek where they joined others, "all werefeeding quietly in an open park."
total of 35: 7 bulls inc. 2 large ones, 13 cows, 7 yearlings, S

The Bison of Yellowstone National Park (Appendix 3)

young calves, fresh sign of two bulls on Timothy Creek. total
counted for trip: 39"However, the summer range is so extensive and difficult totraverse that it would require a great deal of time and careful
work to examine it thoroughly... I have never seen buffaloes on
the range so wary and difficult to locate as the wild ones in the
Yellowstone Park. ... As these buffalo winter around the warm
springs... it seems reasonable to me that if undisturbed, theyought to gradually increase."
2 buffalo seen between Cold Creek and the Lamar R.

Scout Monthly 20 Sept.
Reports
1912(1912)(approx.)
27 Sept. 25 wild buffalo, vicinity of Saddle Mt.
1912
Supt. Annual
1912"A special effort was made during the month of July toReport (1912)
determine as nearly as possible the exact number of buffalo in
the wild herd in the park. Forty-nine animals, including 10 thisyear's calves, were counted. ... indicates that the herd is thriving
beyond expectation."
Anonymous
winteradded note: "Men on Lake Station claim 53 winter 1912-13 but
winter File No. 1912-13 not officially reported."
21 & 22 191213
8/2/12
Scout Monthly 28 Feb.
saw 35 wild buffalo, trip from Yellowstone Lake outlet toReports (1913) 1913
Pelican cabinMarch
1 bull, head of Mist Creek(early)Lake Station
17 March 53 buffalo, patrol from Pelican cabin
Record1913
Scout Monthly April
1 bull, trip from Cache to Willow Creek on top of Miller Creek
Reports (1913)
divideLake Station
30 May 2 buffalo, patrol to Cub Creek
Record1913
Scout Monthly 5 Sept.
20 buffalo, trip from Cold Creek to Frost Lake
Reports
1913(1913)
Supt. Annual
1913"No accurate count of the wild herd of buffalo was made, but
Reportscattering bands of them have been seen, and one party on patrol(1913)
reports having seen 7 calves with a herd at a distance. It isbelieved that there has been some increase."
Scout Monthly September sign seen, vicinity of Saddle Mt.
Reports(1914)
Supt. Annual
1914"No particular effort was made to make an accurate count... but
Reportthey have been seen in considerable numbers on several(1914)
occasions,... increasing slowly."
Stevenson
4 Dec.
"went up Pelican Creek and Raven Creek to count Buffalo. 4(1915-16)
1915
found on Pelican Cr. 27 on Raven Cr 31 in all about 5 large
bulls 6 yearlings 4 calves and the rest cows and young bulls."

The Bison of Yellowstone National Park (Appendix 3)

Supt. Annual
1915"has not been practicable to get an accurate count..."Report(1915)
NOTE: Superintendents' Annual Reports for a few more years indicate wild herd numbers,
which will not be included in this summary, as they may represent the addition of some
escaped tame-herd members.

app3.htm
Last Updated: 24-Jan-2005

The Bison of Yellowstone National Park (Appendix 4)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

APPENDIX IV:

BISON POPULATION 1902-68
Winter190102
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30

Lamar
ActualLoss Est.
Ct.

PelicanMary Mountain
Total
ActualActualLoss Est.
Loss Est. Actual Ct. Loss Est.
Ct.
Ct.

21

23

28
1
39
2
44
57
59
2
73
1
95
5
120
3
141
2
143 28
162
8
193
5
239
4
276 18330
8385
5414 45440 17526
7578 56672 14753 13764 109866 23936 41
996 541092 1061097 132

19
12
30

25
5

90
61
76
69
76
66
65
72
61
17
27

46

47
51

1
7

84
95
118
149
168
192
215

2
1
5
3
2
28
8

270
348
397

4
18
11

504
501
602
647
748

46
17
7
56
14

30

15
20
23
29
27
48
53
31
72
67

44

15

10
2

1

3
1

10

830 109931 231008 41
1057 41
1109 1061124 132

The Bison of Yellowstone National Park (Appendix 4)

31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68

1182 120
1016 222
985 207 1000
950 177
830 264 1000
640 109 708
456 17 488
554 25 577
582 67 605
630
3 675
536 212 560
513 200742
9
352 405445
348 200
442
7
313A 237
396
230 228

10

136
188
146
157
122
217
256
122
222
324
233

1192 120

150
200
160
165
165
1 230
2
2
1

71
30
55
72
116
56
100
100
173
163
210

68
63
80
130
137

1
38

929
756
800
850
970
927

101a
307
205
311A

143 243

251

158b

461

77 106

5

340
525A
553A
640A
582

960 237
1126
1094 2282

976 250858

621477 139 1425
288 1350
1258 373
543 27312
44 800800
869
148 975
370 8196 821
388 392c
226 54 366
397
3 400
418
4 440

288
207
145

847 109674 17755 25811 678683
809 213869 202964 11747 407932
791 23824
60

392 11888659 231
310 212
12
26

169

488

18
212
148 135
8 163
6 187
85 87
66
2
80
1 82
70
1 80

aFirehole only.
bCount made during reduction.
cIncludes 38 natural mortality.

Actual counts exclude loss figures.
Counts are postreduction, precalf.

115
100
123
160

190
238
274

650
418
400

38
1
1 124
2

188 267
76 51 200
194
1 194
188
1 200

The Bison of Yellowstone National Park (Appendix 4)

Losses are mostly reductions.
Counts before 1951-52 are ground unless marked with A. Beginning in 1951-52, all counts
are aerial.
Changes have been made from previous tabulations (Skinner and Alcorn, 1942-51)
according to more accurate information.

app4.htm
Last Updated: 24-Jan-2005

The Bison of Yellowstone National Park (Appendix 5)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

APPENDIX V:DATA ON FETAL SIZES COMPILED FROMTABULATION OF LATE JANUARY 1941 (SKINNER
1941)
Sex

No.
SampledFemale

28

Male
Total
Sample46
74

app5.htm
Last Updated: 24-Jan-2005

Size Range
4 lb. 5 oz.—
23 lb.
6 oz.—23 lb.

% < 1 % 1-5 % 5-10 % 10-15 % 15-20 % > 20
lb.
lb.
lb.
lb.
lb.
lb.
0

7

25

29

29

11

7

7

33

22

26

7

4

7

30

24

27

8

The Bison of Yellowstone National Park (Appendix 6)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

APPENDIX VI:

KNOWN BISON MOVEMENTS TO AND BEYONDYELLOWSTONE NATIONAL PARK BOUNDARIES
1942-67
West Boundary
Pop.
No.
Mary
Mtn.

No. out; location

South
North Boundary
Boundary
Pop.
Pop.
No.
No.
Mary No. out;
No. out;
Lamar
Mtn. location
location1942
Dec.
194243 late
winter742

A few; Gardiner

742

1943
Aug.
Sept.

100 1; 1-1/2 800
mi. S of est.
S. Gate3;
vicinity
S. Gate500

130; down YellR., most only
about 10 days
and returned
150; near Lake
Abundance

1947
fall
1948
late
winter1951
640 1; Young Ranchlate
1; Gallatin highway
Feb.
March
1955
900 3; Fall River Bridge
Feb.
est.
1956
Mar.
1957
Feb.

550 6; Fall River Bridge
est.

313

380
est.

East BoundaryPop.
No.
L'mr- No. out;
P'ln. location

31; Elk Cr.Hellroaring area
68; GardinerJardiner

6; near line,
inside220 8;
est. GardinerJardine

The Bison of Yellowstone National Park (Appendix 6)

1959
400
Feb.
est.
1962
winter
1963
500
winter est.
1964
400
late
est.
wintersummer
fall
1965
400
Jan.
est.
1966
400
Mar.
est.
May
July
Aug.

1; Bitch Cr.
135
est.
34; Bechler Mdws.
(in)
1; Fall River Ridge
1; Fall River Ridge

23; Bechler Mdws.
(in)2; Fall River Ridge
2-3;Cave Falls area
1; Grassy Lake
2;West Entr. toHenry's Lake to
Ennis

1967
200 2 female calved, 1
lateest. male PorcupinewinterWarm Riverfall
cow+calf Porcupine
Oftensummer
Everyyearsummer

400 2; 7 mi.
est. S. of
200
boundary est.

10; Eagle Cr.

1; Mol HeronCr.

150 Some
est. (bulls)
Upper
TimberCr.

200 1; S.
est. Gate

A few
A few; Upper
Hellroaring andSloughdrainages

NOTE: Refuge Manager Vivion, Red Rock Lakes National Wildlife Refuge, states (1968pers. comm.) there area few wild bison in that area from ranched herds of some years ago.
Occasional west side reports may not actually be Yellowstone bison.

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The Bison of Yellowstone National Park (Appendix 7)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

APPENDIX VII:

OCCURRENCE OF GRASSES AND GRASSLIKE
PLANTS IN BISON USE AREAS

Type of Site

Species

Pond and creek edges,
wet bottomlands

Sedge (Carex spp.
     C. aquatilis)
Beaked Sedge
Nebraska Sedge
Woolly Sedge
Western Bulrush
Sedge (Carex spp.
     C. acuta     C. aperta     C. aquatilis     C. platylepsis     C. raynoldsii     C xerantica)
Beaked Sedge
Silvertop Sedge
Smallwing Sedge
Woolly Sedge
Spike-sedge
Horsetail
Wire Rush
Grass species
Meadow Barley
Sweetgrass
Timothy
Tufted Hairgrass
Sedge (Carex spp.
     C. acuta     C. athrostachya

Swales, wet

Moist meadows

LocationF HV La P ULb
X
X
X
X

X

X
X
X

X
X
X

X X X
X X X
X
X
X X
X
X
X X
X
X
X
X X
X
X
X
X
X
X
X X
X X X X
X X X XXXX
X X X X
X
X
X

The Bison of Yellowstone National Park (Appendix 7)

Moist upland sites

Drier uplands sites     C. platylepsis     C. raynoldsii
Smallwing Sedge
Valley Sedge
Woolly Sedge
HorsetailLong-styled Rush
Wire Rush
Grass species
Alpine Foxtail
Bluegrass
Canby Bluegrass
Cusick Bluegrass
Kentucky Bluegrass
Giant Wild-rye
Sweetgrass
Timothy
Tufted Hairgrass
Grass species
Bluegrass
Giant Wild-rye
Idaho Fescue
Meadow Barley
Mountain Brome
Columbia Needlegrass
Richardson Needlegrass
Timber Oatgrass
Timothy
Sedge (Carex xerantica)
Smallwing Sedge
Grass species
Bluegrass
Canby Bluegrass
Cusick Bluegrass
Kentucky Bluegrass
Sandberg Bluegrass
Idaho Fescue
Junegrass
Needle-and-Thread
Needlegrass
Columbia Needlegrass
Richardson Needlegrass
Tufted Hairgrass
Wheatgrass

X
X
X

X
X
X
X X

X
X
X
X X
X X X XX
X X X X
X
X
X
X
X X
X
X X X X
X X
X
X X X XX
X X X X
X
X X X
X
X
X
X
X X
X
X
X
X X
X
X
X
X
X
X X X X
X X X
X
X X
X
X
X
X
X

The Bison of Yellowstone National Park (Appendix 7)

Mountain herbland

Mountain mountain sites

Subalpine meadows

F = Firehole
HV = Hayden Valley
L = Lamar

Bluestem Wheatgrass
Bluebunch Wheatgrass
Slender Wheatgrass
Thickspike Wheatgrass
Sedge (Carex aperta     C. raynoldsii     C. xerantica)
Ovalhead Sedge
Smallwing Sedge
Slender Rush
Wire Rush
Bluegrass
Alpine Bluegrass
Canby Bluegrass
Idaho Fescue
Meadow Barley
Mountain Brome
Needlegrass
Purple Onion Grass
Timothy
Alpine Timothy
Slender Wheatgrass
Tufted HairgrassLong-styled Rush
Bluegrass
Idaho Fescue
Junegrass
Timber Oatgrass
Sedge (Carex nova)     C. platylepsis     C raynoldsii)
Hepburn Sedge
Smallwing Sedge
Bluegrass
Alpine Bluegrass
Timberline Bluegrass
Idaho Fescue
Meadow Barley
Alpine Timothy
Tufted Hairgrass

X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X

The Bison of Yellowstone National Park (Appendix 7)

P = Pelican
UL = Upper LamaraData is more complete for Lamar. bAll wet sites are at higher elevations.

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The Bison of Yellowstone National Park (References)

YELLOWSTONE
The Bison of Yellowstone National ParkNPS Scientific Monograph No. 1

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