BISON OF YELLOWSTONE NATIONAL PARK QL 737 .U53 M4 1973 BRIGHAM YOUNG UNIVERSITY 3 1197 22177 9835 THE BISON OF YELLOWSTONE NATIONAL FARK Margaret Mary Meagher Research Biologist National Park Service National Park Service Scientific Monograph Series Number One 1973 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 has basic responsibilities for water, fish, wildlife, mineral, land, park, and recreational resources. Indian and Territorial affairs are other major concerns of America's "Depart- ment of Natural Resources." The Department works to assure the wisest choice in managing all our resources so each will make its full contribution to a better United States-now and in the future. This publication is one in, a series of research studies devoted to special topics which have been explored in connection with the various areas in the National Park System. It is printed at the Government Printing Office and may be purchased from the Superintendent of Documents, Government Printing Office, Washington, D.C. 20402. Price $2.25. Stock No. 2405-00524 Library of Congress Catalog Card Number: 73-600221 Ackn owledgm en ts THIS RESEARCH WAS UNDERTAKEN with the Sponsorship of the National Park Service and the Museum of Verte- brate Zoology, University of California, Berkeley. The re- search 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 appre- ciation is due John Good, former Chief Park Naturalist, for encouragement and assistance in arranging work require- ments to allow time for the study. Park Rangers Peter Thompson, Dale Nuss, and Gordon Boyd assisted with some of the field work. 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, Su- pervisor of the Montana State Fish and Game Department Laboratory, provided food habits analysis assistance. W. E. Booth, Montana State University, verified plant identifica- tions. 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, adminis- tered by the University of California. The Yellowstone Li- brary and Museum Association contributed to the reproduc- tion of dissertation copies. To these people and organizations, and the many other individuals who provided information, encouragement, and assistance — my thanks. juiy 1972 Margaret Mary Meagher [ Digitized by the Internet Archive in 2014 https://archive.org/details/bisonofyellowstoOOmeag Summary Objectives OF this study were to provide basic data on the life history, habits, and ecology of bison in Yellow- stone National Park. The original population of bison in historic times consist- ed of mountain bison, Bison bison athabascae. In spite of poaching to near-extermination by about 1901, a remnant of the subspecies 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 of hybrid descendants of the two subspecies. The present wintering distribution within the park ap- proximates 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 the his- toric 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 his- toric numbers. Examination of 71 females killed for population reduc- tion 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 than formerly re- corded 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 than formerly. The observed changes may reflect the shift from a semiranched popula- tion to a wild one. Records from live-trapping operations in 1964-66 pro- vided sex and age structure information. The records sug- gested that female survival was favored during the calf year, but that male survival was favored the next 3 years of life, after which differential survival could not be distin- guished 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 num- bers 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 mor- tality occurred during the first year. Nearly half the calves which survived into their first winter died before 2.5 years of age. Recruitment into the population occurred with sur- vival to 3 years of age. Population trends suggested that increases in the popu- lation 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, occur- ring 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 eleva- tions; final movements to winter ranges occurred by mid- November. Bull movements were somewhat more irregu- lar. Movements and distribution on summer range areas appeared more influenced by the presence of 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 oc- curred 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 en- tities in terms of winter range. This may explain the lack of population emigration to and reestablishment on unoccu- pied 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 pro- vided 96% of the diet volume throughout the year. Forage availability did not appear to be a population-limiting fac- tor under most conditions. Population numbers in Pelican over a span of many years suggested that the levels were regulated by environ- mental 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 pop- ulation 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 sagebrush-grassland uplands, open streams, and thermal areas may allow habitation over time by mixed herd groups of bison in this wintering valley. Contents ACKNOWLEDGMENTS SUMMARY Chapter 1 INTRODUCTION Methods 1 Chapter 2 THE STUDY AREA Physiography 3 Climate 8 Vegetation 9 History 10 Chapter 3 THE BISON POPULATION The historic population 13 Mountain bison 14 Numbers and distribution through 1902 17 The present population 26 Origins 26 Present composition 27 Numbers and distribution 29 Chapter 4 GENERAL CHARACTERISTICS Physical characteristics 38 Appearance 38 Weight 38 Life Span 46 Behavioral characteristics 46 Grouping characteristics 46 Behavior and specific circumstances 47 Senses and disposition 47 Visitor opportunities to see bison 49 Chapter 5 POPULATION CHARACTERISTICS Sexual maturity 50 Reproduction rate 5 1 Fetal sex ratio 56 Number of young at birth 58 Population structure 58 Calf percentages 60 Mortality 62 Calf Mortality 62 Subadult mortality 64 Other mortality 65 Population trends 65 Chapter 6 MORTALITY FACTORS Parasites 69 Internal parasites 69 External parasites 69 Diseases 70 Predation 72 Other causes 73 Chapter 7 HABITS Calving 75 Rut 76 Movements 77 Migratory movements 77 Summer range movements 8 1 Winter range movements 84 Movements beyond park boundaries 85 Mixing of population segments 85 Food habits 90 Chapter 8 HABITAT RELATIONSHIPS Use of forage areas 96 Use of thermal areas 98 Effects on habitat 103 Page Chapter 9 SUGGESTED MECHANISMS OF POPULATION REGULATION 110 APPENDICES I Common and scientific names of plants 114 II Summary of bison reports prior to 1903, 116 Yellowstone National Park and vicinity III Reports of wild bison, 1903-19, Yellowstone National Park 136 IV Bison population, 1902-68 144 V Data on fetal sizes compiled from tabulation of late January 1 94 1 (Skinner 1941) 148 VI Known bison movements to and beyond Yellowstone National Park boundaries, 1942-67 149 VII Occurrence of grasses and grasslike plants in bison use areas 150 xi Figures 1 Map of Yellowstone National Park showing study area 4 2 Aerial view of a part of the forested plateau 5 3 Springtime view west across lower Lamar Valley 6 4 Upper Lamar drainage, Absaroka Mountains in background 6 5 Bison on the Pelican Valley winter range 7 6 A part of the Hayden Valley winter range 7 7 Lower Geyser Basin, Firehole winter range, early spring 8 8 Summer range on the western part of the Pitchstone Plateau 9 9 Cows and calves, Hayden Valley, sometime before 1894. 15 10 Skulls of Bison bison athabascae and B. b. bison 16 11 Map of bison distribution and movements in historic times 24 12 Bison wintering in Hayden Valley prior to 1894. 25 13 Buffalo Jones and Army Scout Holt with captured bison calf 27 14 Clipped appearance of a mature bull. 39 15 Bison shedding old hair, mid-summer 40 16 Wisps of shed bison hair on a branch of a lodgepole pine 41 17 Newly-born calves in a mixed herd group. 41 18 Calf that has lost its first red-brown pelage. 42 19 Head shape and size of cow compared with bull 42 xii Page 20 Spike-horn bull, approximately 2.5 years old. 43 21 Spike-horn bull, yearling female, cows, and bull. 44 22 Horns of adult cow and spike-horn bull compared 44 23 Old Tex, a record Yellowstone bull 45 24 Bison population trends from population counts, 1936-68 66 25 Trench left in soft snow by traveling bison 73 26 Bull bison foraging in snow approximately 2.5 feet deep 74 27 Feeding site in snow approximately 2 feet deep 74 28 Calves a few days old 76 29 Grassy spot uprooted by bison horning during the rut 77 30 Map of the Lamar-Pelican area 79 31 Map of Hayden Valley-Firehole-Madison Plateau area 80 32 Bison herd groups on Alum Creek, Hayden Valley 81 33 Bison on the strip of sedge meadows along upper Alum Creek 82 34 A herd group on the east boundary near Canoe Lake 83 35 Map showing bison movements across park boundaries 86 36 Neckbanded bison in a group at Pocket Basin on the Firehole. 87 37 Population fluctuations in wintering areas caused by shifts 87 38 Snow-free bison feeding site on warm ground in Firehole 98 xiii Page 39 The same site shown in Figure 38, in early summer 99 40 Warm site along Alum Creek in Hayden Valley 99 41 The same site shown in Figure 40, in summer 100 42 Bison bull wintering among active geysers and hot springs 100 43 Aerial view of the Alum Creek winter feeding area. 101 44 Hot water keeps Firehole River open all winter 101 45 Sedge growth along Firehole River provides winter forage 102 46 Bison in small thermal area west of Astringent Creek 103 47 Trees debarked by rubbing bison, Hayden Valley 104 48 Bison horning effects on a lodgepole pine 105 49 Bull bison at a wallow which is used year after year 106 50 A bison trail, Hayden Valley area 107 51 Pelican Valley population numbers, 1902-68 1 1 1 xiv 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 1 1 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 1 Introduction The bison of Yellowstone na- tional 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 Lin- naeus), introduced into Yellow- stone National Park in 1902, and mountain or wood bison (Bison bison athabascae Rhoads), which originally inhabited the Yellow- stone and surrounding country. They are a wild population, unre- stricted 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 historical interest, Yellowstone's bison have not been objects of extensive research. McHugh (1958) studied behavior of bison in Yellowstone. Rush (1932a), Tunnicliff and Marsh (1935), and Locker (1953) pub- lished information on parasites and disease. Cahalane (1944) summarized the history of the in- troduced herd and management practices as of that date. The present study was begun in 1963 to provide basic data on the life history, habits, and ecology of bison in the park. This study re- port, based on extensive field work and supplemented by an intensive search for historical information, provides a basis for management and for evaluation of the impor- tance of this particular bison pop- ulation. As a source 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, com- position of groups, distribution, and habits was obtained by using fixed-wing aircraft and helicopter flights, horse and ski travel, and limited vehicle use. No set pattern of route and interval was estab- lished; work was scheduled ac- cording to season, general animal location, and distances involved. Time of day was generally not a factor. A monocular and a varia- ble-power spotting scope were used for observation. Age and sex information was compiled at herd-reduction opera- 521-650 O - 73 - 2 2 Bison of Yellowstone National Park tions 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 park at intervals since 1932, primarily to keep the bison population at numbers sug- gested 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 ef- forts 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 slaughter on the basis of brucellosis infection. Un- infected animals were also taken to fill removal quotas. All animals were permanently metal ear- tagged during brucellosis testing, and marked with temporary back- tags, which were visible even from an airplane. Most were aged by Department of Agriculture veteri- narians and weighed. During both winters, some re- leased 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 distrib- ute marked animals among re- leased groups as much as possi- ble. Forty-four individuals (30 of them females) were neckbanded, half at each trap. Seventeen fe- males and two males were young adults and older. Half of the neck- bands were lost during the first year. More males than females lost neckbands. Attempts to neckband animals through use of field im- mobilization techniques were not satisfactory. During slaughter operations, approximately 47% of the animals removed from the park were ex- amined for pregnancy, abnormali- ties, and evidence of injury or dis- ease other than brucellosis. Re- productive tracts could not be examined, nor fetal sex ratios de- termined because approximately half of removed animals had bru- cellosis or were suspect. Depart- ment of Agriculture veterinarians advised against examination of reproductive organs, where the Brucella organism most often lo- calizes, to avoid contamination of slaughterhouse premises and ex- posure 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 shot in the park at all seasons and in various locations. Percent composition of samples was determined by vol- ume after separation and identifi- cation of materials. The analyses were supplemented by general field observations of animal feed- ing behavior. 2 The Study Area The study area included all parts of Yellowstone National Park regularly used by the bison popu- lation, or frequented by them in the past 20-25 years (Fig. 1). The occupied bison range covers near- ly half of Yellowstone's 3472 square miles, extending diagonally across the park from the northeast quarter to the southwest quarter. Some phases of study effort were emphasized in the northeast quarter. Lands outside the bound- aries are not used to any extent by the park bison, and hence were not part of the study area, but they are discussed where pertinent to historical populations. Physiography Much of the park is plateau-like, varying in elevation from about 7000 to 8000 feet, and cut by large and small stream valleys (Fig. 2). Mountains project above the gen- eral level on all sides, but are less extensive in the interior. The Con- tinental 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. Tributar- ies of the Snake River drain the southwestern corner. Park geology is discussed by Hague ( 1 899), whose work was fol- lowed by numerous topical stud- ies. U.S. Geological Survey person- nel are now completing a compre- hensive research program which will add much to present knowl- edge of the complex geologic his- tory of Yellowstone. Extensive vol- canism, of which the widely dis- tributed thermal activity is a rem- nant 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 Pla- teau, and Bechler (Fig. 1). The Lamar (Fig. 3), at approximately 3 4 Bison of Yellowstone National Park Fig. 1. Map of Yellowstone National Park showing study area. 6400 feet, includes lower Hellroar- ing and Slough creeks, the main Lamar River Valley below Soda Butte Creek, the north-facing low- er 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 and tributaries ris- ing 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 The Study Area 5 Fig. 2. Aerial view of a part of the forested plateau, located centrally. River to the north and 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 the mouth of Pelican Creek and in- cludes Marv Bay on Yellowstone Lake. Hayden Valley, elevation 7700 feet, is centrally located in the park (Fig. 6). It extends from the Grand Canyon of the Yellow- stone south to the Mud Volcano, west to Mary Mountain, and in- cludes Beach and Dryad lakes to the south and Cygnet Lakes to the north. The Firehole, at 7200 feet, refers 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 the Continental Divide and extends to the Bechler Meadows. The Pitchstone Plateau (Fig. 8) lies southeast of the Madi- son Plateau. The Bechler Mead- ows, at6400feet,arecomparableto the Lamar in elevation. Soils vary greatly. Generally, there are deep silts in the bottoms of the big valleys. Morainal materi- als are especially prominent in Lamar. Lake deposits of clays and 6 Bison of Yellowstone National Park Fig. 4. The upper Lamar drainage with the edge of the Mirror Plateau to the right, a part of the Absaroka Mountains in the background. The Study Area 7 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. 8 Bison of Yellowstone National Park Fig. 7. The Lower Geyser Basin area of the Firehole winter range in early spring. sands are found in Pelican and Hayden valleys. Higher areas commonly have shallow, poorly developed soils derived from vol- canic parent material interspersed with alluvial sites. Climate Throughout the area winters are long and cold, with short cool summers. The U.S. Department of Commerce Weather Bureau (1930-59) summary for Yellow- stone National Park indicated for the headquarters' station at Mammoth, near the north bound- ary, 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 aver- age about 5°F higher than those for most of the park. The same summary indicated that average annual precipitation in the study area varied from 13.73 inches at Lamar to 38.26 inches at Bechler. Near Pelican, the annual average was 19.00 inch- es. Most precipitation occurred as snow. For most of the park, be- tween the 7000- and 8500-foot levels, the average snowfall was about 150 inches, with Lamar av- eraging 85-95 inches, and Lake, near Pelican, averaging 146 inch- es. For a 50-year period at Lake, a range in snowfall of 81-270 inches The Study Area 9 is recorded. Actual depth on the ground at Lake, as recorded by snow 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. Lamar would usually have somewhat less; Bechler, somewhat more. Crusting conditions, for which no record is available, var- ied considerably. Seasons of the year vary with location and altitude. Warm sites near thermal activity are snow-free earlier and have a longer growing season than surrounding areas. Winter extended from mid-No- vember 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 July in the valleys, late July in the mountains. Killing frosts are usual in most locations before the end 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. Vegetation Vegetation types were not mapped for purposes of this study. Figure 1 indicates the ex- tent of the larger meadows within the forested parts of the study area. More detail is apparent in Figs. 30 and 31, which show subu- nits of the study area. Major spe- cies of plants, according to site, are 1 Fig. 8. Summer range on the western part of the Pitchstone Plateau. 10 Bison of Yellowstone National Park listed in Table 1. General descrip- tions 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). The large, open valleys of La- mar, Pelican, Hayden, and Fire- hole have dense sedge growth bordering the streams and extend- ing across the flat bottoms. The slightly higher slopes and levels support bunchgrasses, forbs, and sagebrush, with scattered marshy swale areas. Shrubs, except sage- brush, are of limited extent gener- ally in these valleys. In Lamar, wil- low was grubbed out in some places to increase the area of pas- ture and hay land during early Buffalo Ranch operations. Exten- sive grassland and sagebrush areas on high slopes and ridges are par- ticularly common in the northeast quarter, although patches of more lush herbaceous vegetation are frequent. Much of the study area is forest- ed, predominantly by lodgepole pine, which varies from dense, even-age growth with little under- story to open stands with consider- able sedge and grass. Dense shrub- by undergrowth is usually not ex- tensive. Down timber is common. At higher elevations, Engelmann spruce and alpine fir replace the lodgepole. Whitebark pine is found in some locations. Meadows are scattered throughout the for- est on moist sites along streams and around 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 mead- ows are found. Above these, at the highest elevations, alpine vegeta- tion occurs to a limited extent. History Yellowstone National Park was established in 1872, before the surrounding area became the states of Idaho, Montana, and Wyoming. Boundary changes, made twice, added small areas to the original rectangle and altered the east boundary in 1929 to con- form for most of its length to the drainage divide formed by the Absaroka Mountains. Most of the land adjacent to the boundary 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 sev- eral tribes of modern Indians were primarily summer hunters, al- though a few sheep-eaters lived a marginal existence throughout the year. Hostile Indians did not travel the park after the Bannock War of 1878, but hunting parties from The Study Area 1 V ■y i 2 o S 3 Ja 04 S to u 3 o 2 PQ u .s & 3 .£ 73 V to W lO «J "O " & 5 £ c75 C3 S 3 « 3 « 11 % 2 «j a > v £ -a 3 «u O C H 'B V 2 CO O J2 O 3 O » © 3 ^ 0 0 > 3 s s CO o ° a .S g s * a c ° O =5 ; s '© J CO ^3 13 e r 0 c« 5s < o ~ o o o <+- oo 0 «j CO 3 r3 O 1 i 5 c £ 2 "1 § S of £ £ 2 T3 <+- £ o a00 to 0 .£ -S 3 ™ if 0 «) S £ 5-1 > a D I u s I ■8 12 Bison of Yellowstone National Park reservations were known at the park fringes as late as 1893 (Hough 1894). Although few left written accounts, trappers, begin- ning with John Colter in 1807, vis- ited the area many times before the end of the fur trade in 1840. Miners and explorers followed. The park was not subject to set- tlement, and there were few peo- ple for some years after its estab- lishment. With the exception of a few early squatters, developments were for administrative use or concessioner operation. In con- junction 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 Al- corn (1942-51) summarize the Buffalo Ranch-Lamar Ranger Sta- tion operations of Lamar and Slough Creek valleys from 1907 through 1951. Seeding and irriga- tion practices were part of the hay- ing program, as well as construc- tion of buildings, 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 au- thority for dealing with violators. Outside the park, ineffective laws contributed to poaching within the boundaries. Not until 1901 did the Superin- tendent 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 doubt- ful. Intensive management of an introduced herd began in 1902 to ensure survival of some bison in Yellowstone. For a time the ani- mals lived in semidomestication, and were fed hay and tended al- most like a herd of cattle. Manage- ment 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 com- pletely wild and unfettered by fencing or artificial management. 3 The Bison Population The Historic Population The genus Bison probably in- vaded 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 Skin- ner and Kaisen (1947). Of the in- vading species, only one persisted to give rise to B. occidentalis, the ancestor of B. bison, the modern form. Two subspecies, B. b. bison and B. b. athabascae, are recog- nized by cranial evidence, al- though historical accounts suggest there may have been others (Roe 1951). The form athabascae is apparently the more 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 from bulls, cows, and calves (B. bison) were found near the edge of a glacier northeast of Yellowstone National Park (Pattie and Verbeek 1967). In 1964 a fos- sil cranium (B. b. athabascae) was found embedded in a natural oil seep on the Mirror Plateau in the park. The Yellowstone bison of histor- ic times were a remnant of a once much more extensive bison popu- lation, known to trappers and In- dians, which inhabited the moun- tain ranges and the intermountain valleys of the Rockies and extend- ed 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), these were mountain bison. Considerable numbers of bison once lived close to the park. Many skulls have been found in the Red Rock Lakes area, approximately 35 miles west of Yellowstone (Owen Vivion 1968 pers. comm.) Frank Childs, for- mer Yellowstone ranger who worked on Red Rocks land acquisi- tion matters during the mid- 1980s, heard that 300 bison died there during a bad winter many 13 14 Bison of Yellowstone National Park 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 Rus- sell, 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 "buf- falo skulls are strewn by thousands — " in the Yellowstone valley about 40 miles north of the park. Ac- counts 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, and long before the killing of the northern herd of Great Plains bi- son in the early 1880s. A misconception of some writers — that Yellowstone's bison of his- toric times were displaced survi- vors from the Great Plains slaugh- ter— probably stems from: (1) the lack of recognition of two subspe- cies of Bison bison; and (2) the impression that early explorers found little "game" in the Rocky Mountains. Three factors contrib- ute to the idea that bison were sparse in the mountains. Com- pared to the abundance of certain large mammals on the plains, the mountains probably seemed al- most uninhabited. Secondly, travel routes followed river valleys and drainages, crossing small areas of high summer range at few loca- tions, 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 trav- elers who wrote of their journeys, including official government par- ties, often commented only on wildlife which was actually sought out or shot for food. Mountain Bison The existence of mountain bi- son, different in appearance and behavior from the plains type and gone from much of their range by the 1840s, has generally been little known. Christman (1971) reviews historical evidence for the subspe- cies, their distribution to the west of the plains type, and reasons for their early disappearance. He be- lieves the Indians' acquisition of the horse was the factor underly- ing the extermination of mountain bison from extensive areas of orig- inal range, particularly in Wash- ington, Oregon, and Idaho. Many early references to Yel- lowstone 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 and ob- servers. Historical accounts gener- ally agree that, compared with the plains bison, these mountain ani- mals were more hardy, fleet, and wary, and had darker, finer, curl- The Bison Population 15 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 ob- servers. Photo by John Folsom, a winterkeeper at Canyon. ier hair. Sex and age differences among animals seen may account for discrepancies in description of size. The geologist Arnold Hague (1893) provides the following: The Park buffalo may all be classed under the head of mountain buffalo and even in this elevated region they live for the greater part of the year in the timber. . . .most unusual, save in midwinter, to find them in open val- ley 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 midsum- mer, even by those most familiar with their haunts and habits. They wander about in small bands. . . . Blackmore (1872) was informed that the mountain buffalo con- gregated usually in bands of 5-30, rarely more. Other observers agree that the bands were small, and the animals quite wary. Super- intendent Norris described them as "most keen of scent and difficult of approach of all mountain ani- mals" (Superintendent of the Yel- lowstone National Park 1880). Altitudinal migrations were an- other characteristic of mountain bison (Christman 1971). Historical accounts from Yellowstone also suggest this habit. Superintendent Norris, in his annual report of 1880, describes summer and win- ter distributions of bison in the 16 Bison of Yellowstone National Park park, stating clearly: . . .summer in the valleys of the Crevice, Hellroaring, and Slough Creeks, and the mountain spurs be- tween them, descending with the in- creasing 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 repeti- tive pattern of seasonal bison dis- tribution which reflects altitudinal movements. Historical accounts recognizing a mountain buffalo are supported by limited cranial evidence. Skin- ner and Kaisen (1947) show an overlap in general distribution between mountain and plains bi- son along^ the east slopes of the Rockies, including Yellowstone, but state that ranges for historic times must be based on early ac- counts plus occasional bones or crania. Seven skulls from Yellow- stone's original wild herd were picked up on the ground along the Gardner River and at Mammoth in 1902. All had weathered sur- faces. These were considered as most likely representing athabas- cae. The 1964 skull (Fig." 10) found 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. The Bison Population 17 on the Mirror Plateau was identi- fied by Skinner (1965) as "an ex- ceptionally long horned, appar- ently young Mountain bison = B. (B.)b. athabascae " No Yellow- stone skulls which predate the 1902 introduction have been iden- tified as plains type. Numbers and Distribution through 1902 Numbers and distributions from the historical accounts of Appen- dix II are shown in Table 2. Norris (Superintendent of the Yellow- stone National Park 1880) estimat- ed a total of 600, dividing the population into three herds ac- cording to area. By this date, poaching had certainly begun in- side the park, along with increas- ing pressure on an ever-shrinking mountain bison population out- side. Numbers in a given area fluc- tuated then as now. After consid- eration of all the listed reports of numbers and distribution, the his- torical population, ranging in part beyond the park boundaries, is es- timated to have been perhaps 1000 animals. This seems reasona- ble when bison habits and behav- ior and difficulties of making counts are all considered. Subesti- mates by area and season are at the bottom of Table 2. They are made to provide a reference point and must be considered educated guesses. Table 2 also shows the decline of the population to an actual count of 23 in 1902. Again — considering habits, behavior, and census diffi- culties— the population probably was higher; perhaps 40-50 moun- tain bison survived. The near-ex- tinction in about 25 years was the result, initially, of sport and table hunting on both sides 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 verged on extinction, the price paid for heads, plus the minor penalties if caught, attracted poachers who killed all ages and both sexes in the wintering areas. Known losses as listed do not re- flect the extent of the kill. Al- though the Howell poaching case resulted in passage of the Lacey Act in 1894, the population de- clined further as poaching, prima- rily from the west side, continued. Natural losses, coupled with scat- tering of the few remaining ani- mals, left a minimal breeding population in the most remote places of the Pelican-Mirror-Up- per Lamar country. The distribution, to the extent known, of the original population was similar to the present distribu- tion, but larger numbers used cer- tain areas more extensively and 521-650 O - 73 - 3 18 Bison of Yellowstone National Park o g ~ g c/3 55 T3 « .s 11 ■*2 cd o O ed 2 I <3 S3 a- 1 3 3 -a j$ T! i> §5 T3 0) D r- r- 00 00 en 00 00 00 00 The Bison Population 19 6fl tH) '5 c O C bo jo to 3. m too ^ -3 •§ o -B •a c ea *J c § 3 00 3 £ iZ go * a S 5 S | a> — 3 ■d .5 jc 1 O 1.2 js a* o 13 2 " S - 71 Sf? x - ft 20 Bison of Yellowstone National Park 111 C I o o g ~ 5-2 o % 3 1 2 a 2 u J > h 5, g 2 D J II 0 *t? o . o 13 llll a .5 ^ O 3 <1> ^ ^ o 3 .5 | ~ » o 3 2 ° § a 3 . — i on — 3 9? ^ >- 13 > T3 » « aJ cd ■£ VO U ON | -h cn -h £ O + M3 C CJj 22 Bison of Yellowstone National Park o e w 5^ C 73 o B e i i— i > 5 J Oh > !T! > °1 > .53 ^ fa 9 ^ s O cS C 93 o E o 0-1 E o go -go - S.2 O £ -2 § W K '43 >> T3 O The Bison Population 23 ranged beyond the park bounda- ries part of the time. Figure 1 1 shows the probable general distri- bution 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 as well 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. From northeast to southwest, the four areas of historic summer range were: north of Lamar, Up- per Lamar-Mirror Plateau, Hay- den Valley, and Madison-Pitch- stone 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 sum- mer range is less clear. Some of 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 have seen 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. Large numbers of bison regular- ly wintered in Lamar, Pelican, and Hayden valleys (Fig. 12). The Fire- hole seems to have been less im- portant. Snow conditions common in the Bechler Meadows make it unlikely that large numbers habit- ually wintered there, but certainly small groups must have since calves were captured there in early spring (Murri 1968). Historical reports do not indi- cate groups along the Madison and Gallatin rivers to the northwest, within the park, but Raynolds (1867), while crossing from Hen- ry's Lake to the Madison River, just west of the park, in 1860 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 Cou- gar 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, loca- tions, and movements (Fig. 11). 24 Bison of Yellowstone National Park Fig. 11. Map of general distribution and movements of bison mixed herd groups in historic times. Fig. 12. Bison wintering in Hayden Valley prior to 1894. Photo probably by John Fol- som, early Canyon winterkeeper. Hague (1893) mentions the lack of buffalo trails, but he was compar- ing Yellowstone to the plains. Definite buffalo trails did exist (DeLacy 1876). Norris' (Superin- tendent of the Yellowstone Na- tional Park 1880) map shows a trail northeast across the Mirror Pla- teau 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 Yel- lowstone Lake, was implied by ear- lier writers, and stated as fact by Hough in 1894. Routes in use by patrols 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 the northwest 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 south of the boundary, found before 1925, presumably belonged to another such individual. 26 Bison of Yellowstone National Park The Present Population Origins As stated previously, the Yellow- stone bison of the present derive from two subspecies: plains bison from Montana (Pablo-Allard herd) and Texas (Goodnight herd), in- troduced in 1902, and a remnant of the original wild population of mountain bison. Skinner and Al- corn (1942-51) summarize the in- troduction, numbers, and subse- quent management practices per- taining to the introduced herd at the Buffalo Ranch in Lamar. Pop- ulation numbers are from that source and other official reports. Skinner also provides a resume7 of official information concerning the wild bison, but does not attempt to evaluate the question of their sur- vival. Information scattered in the diaries, reports, and correspond- ence of park personnel (Yellow- stone National Park Archives) pro- vides the basis for the following. Before 1915, introduced bison of plains stock could not have es- caped 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 the fenced herd was turned out in 1903, and one or two stray bulls were mentioned later in scout reports, these appar- ently never joined the wild bison. Twenty bulls from the Buffalo Ranch were driven 14 miles up the Lamar River in 1914; these all re- turned. 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 orig- inal wild herd did persist, and gradually increased once protec- tion from poaching was assured. The critical survival period ex- tended 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 na- tive 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 individu- als 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. The Bison Population 27 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." Official population estimates of the time did not allow for more animals than were actually seen; they were undoubtedly conserva- tive. By 1912, as Nowlin's classifi- cation of 35 animals shows, the survival of calves (8) and yearlings (7) was encouraging, and the po- tential for increase (13 females) was apparent. By 1915, the popu- lation may have been nearing 100. Known mortality is shown only in 1904. While winter loss probably occurred during other years, 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 pre- sent population gene pool is, at best, rough but is preferable to having none. Table 3 shows the sex and adult-calf composition of 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 add- ing a second bloodline is also shown. From these numbers, Ta- ble 4 was compiled to show the age classes according to sex. The bulls 4 years and older were assumed to have done the breeding in this fenced situation, although young- er 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 Fig. 13. Buffalo Jones and Army Scout Holt with a captured bison calf on a sled. Photo from Yellowstone National Park files. 28 Bison of Yellowstone National Park -o M o £ * v be S2 g o S bp CM + 5* »H >, i-i r» O r-i CM rj< CO CM + cd a CO CM CM r>. CD CD if) if) CM CM 1— 1 + ed Cd ed ed + CM <£> CO CD CO CO CD kf) O 00 CM CM S3 ed ed cd ed ed cd ed ed cd o cd cd CM CM CM CD CM CD O CM CM CM CO m m CD co if) CD ed cd cd cd ed ed ed 00 00 o CD CM <* CM 10 <£> CM CD CM CO if) lO oo CD O CM CO »f> o o o o o O o o CD cd cd CD cd cd CD CD CD CD CD CD CD £1 S3 3 £ « o ed J3 4»ip The Bison Population 29 tables, the wild strain in the fenced group was estimated at a maxi- mum of 10% by 1910. Further di- lution of the wild strain in the fenced herd was assumed until perhaps 1917. Sometime between 1915 and 1920, intermingling of the intro- duced and wild animals began. At first this was probably gradual. Park records do not show the spe- cific 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 sev- eral 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 ef- forts were made to keep the intro- duced herd on the higher summer ranges, where intermingling with the wild bison must have quickly increased. After intermingling of wild and introduced animals began, several factors tended to increase the wild strain in the total population, al- though the plains type outnum- bered the wild roughly 3:1 about 1917, and perhaps 4:1 in 1921. The number of males in the intro- duced herd was reduced by the yearly segregation of a show herd of bulls beginning in 1909. Addi- tional bulls were removed by live shipment and slaughter. To fur- ther reduce the male surplus (from a ranch operation view- point), castration of bull calves averaged slightly over 50% from 1916 through 1931. As a result, the number of aggressive, domi- nant plains-type bulls with the in- termingled 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 the mountain 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 to be 30- 40%. Numbers and distribution Management practices for many years made little attempt to re-cre- ate a natural, wild bison popula- tion in the park. Efforts concen- trated on ensuring bison in num- bers sufficient to guarantee perpe- tuation. 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, 30 Bison of Yellowstone National Park CM CM CM CM CM CM CM CO ^ CT) CM CM CM CM CM CM CO if) 00 2 o o o o O o © CT> i-H The Bison Population TABLE 5. Presumed age classes of male bison on the range, 1921. 31 Age classes wiiQ neru Tn1"rr*Hiir'fkH hprrl 1I1LI UUULA U llvl U 1 7 21 o I R •J 47 2 O 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. aged animals, and those infected with brucellosis or otherwise con- sidered 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 roundup. Hay was fed to some extent every win- ter 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 of very large populations wintering in Lamar, natural rees- tablishment of the population west beyond the Pelican area into Hay- den Valley and the Firehole did not occur, although a 1946 file report contains a penciled nota- tion of some bison in Hayden Val- ley in 1930-31. 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 move- ment between the two valleys be- came obvious, and they were called the Mary Mountain herd. Two other herds were distin- guished, on the basis of wintering areas, as the Lamar and Pelican. None of these herds is geographi- cally isolated at all seasons of the year, but the names are still used to designate the wintering popula- tions. 32 Bison of Yellowstone National Park Population counts, estimates, and known losses (mainly reductions) are listed in Appendix IV by the three wintering populations and as park totals. Aerial counts were started for the four main winter- ing valleys (Lamar, Pelican, Hay- den Valley, Firehole) in 1949. These counts were not made every year, nor were all main areas checked each time. Usually no at- tempt was made 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 ground counts were made. Estimates based on previous counts, reduc- tion figures, and presumed in- creases were made by park person- nel when counts were not availa- ble. Because of possible popula- tion shifts, these may be unrelia- ble. 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 one of ranching to one of preservation of bison in a natural state, the Na- tional Park Service decided to cut the numbers wintering in Lamar. The decision was based on the gradual elimination of artificial management practices and sup- ported by information derived from a range-condition and carry- ing-capacity study (Rush 1932b). Lamar-wintering bison numbered over 1000 from 1929 through 1932, before Rush recommended a maximum of 1000. Later deci- sions lowered the maximum num- ber until frequent reductions had cut Lamar herd numbers to a count of 143 in 1952. After an aer- ial 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 consid- ered very accurate. Thus, the park population of bison for most of the study period was lower than at any time since the early years of the introduced herd. Winter and summer distribu- tions for mixed herd groups and separate bulls at population levels of the study period are shown in Table 6. Divisions between major areas indicate geographic separa- tion but do not imply population isolation. Bulls were found in all areas of herd use and also 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 were higher. In effect, places most frequented by mixed herd groups probably represent core areas or population centers from which bulls and mixed herd groups move into less-favored locations as the population increases. Although Firehole and Hayden valleys are combined as the Mary Mountain area, winter distribution of total numbers and mixed herd The Bison Population 33 groups favored Hayden Valley, according to available counts since the 1950s. During the reduc- tions of 1964-65 and 1965-66, animals were herded from Hay- den Valley to the Nez Perce trap on the Firehole side with helicop- ters, 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 ani- mals 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 Hay- den Valley and to the south of it as far as Beach and Dryad lakes, al- though some animals from the same population summered to the west of the Firehole. Ranger re- ports indicate that infrequent mixed herd use of the Madison Plateau began in 1939, 3 years af- ter the bison were released on the Firehole. By the early 1950s, use had become common, but appar- ently almost ceased after the 1955 reduction. But in 1963 as many as 50 ranged from the Little Firehole Meadows to the Pitchstone Pla- teau. 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 Meadows southwest of the Madison Plateau until Feb- ruary 1955, when three bulls were seen just outside the park. An oc- casional bull may have wintered in the meadows earlier, since a few animals again began to summer on the Madison Plateau in 1939. Ob- servations and reports indicate a few animals in that area nearly every winter since the mid-1950s, in spite of considerable 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 the area 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 dur- ing most of the winter except for occasional movements of a few hardy bulls. Table 6 shows the val- leys as distinct wintering areas. Groups in Lamar ranged the val- ley 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 low- er parts of Astringent Creek and 521-650 O - 73 - 4 34 Bison of Yellowstone National Park o * 3 .3 ^! C m U U 0 2 u * -d .5 xi bO g 3 * 3 in O hJ O U & ts *2 r> ill S >• 4; c3 * 3 0 ™ 1 s o o *o o a o 2 i - OS U S 9 u 4J ^ i2 . 9 u ^ U 7 > SI** £ U S U (5" 2 "O «W Cd O u 1 "S -2 3 u O CQ (4-1 (4-1 o o -O "3 ed cd S3 2 a £ .2 £ c "3 -c -3 a o EG 3 e . g $ a ! .§ 2 & 2 a c i >> 5. c « s 50 +3 U C/2 O j W 3 S 2 ft< > H •£ o Cd 3 «J 3 £ 1 2 2 § « 4; Oh 'u li 1 1 1 o H 3 cd ■r" n 1 O " X a 3 o « 3 "3 X 0 ed <4i r^ cd O U J 13 > M 3 u J c '"5 bO " 3 In .3 CJ £ a ft. o p4 O u ^ 3 ♦S O t/3 "5 a 3 o -3 'S •I s 3 o 2 S W PQ The B ison Population 35 § I | £ ■§ 5 2 3 U H _, w s I -a - 3 3 P 5 v 3 £ 0 2 « a 3 o fee -o CJ C i v O QJ U £ B ° 6- -j H t S5 J Si «- u & * 5 CQ ™ t/5 a c £ 3 •a •& w R» 1 .2 « S « O J- So a C/5 O "ft 6 | '35 re o CQ «-s * C & o o ffi In T3 W C ll PQ Q, 36 Bison of Yellowstone National Park adjacent hot-spring areas to the west. Although no groups fre- quented Ponuntpa Hot Springs (6 miles north of Pelican Valley) dur- ing the study, both historic records and reports of the mid-1950s (Jim Stradley 1969 pers. comm.) indi- cated some previous mixed herd use. Bison from both Pelican and Lamar Valley wintering popula- tions ranged widely during sum- mers on the Mirror Plateau and the Upper Lamar. Neckband ob- servations and aerial counts showed that the two populations, except scattered bulls, combined on the east boundary for several weeks in 1967. Main use areas in the Upper Lamar region during the study 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 pla- teau extending from the head of Flint Creek to the heads of Peli- can-Timothy-Raven creeks. At higher population numbers, as reports of the 1930s and 1950s indicate, herd-group use included most of Specimen Ridge north and west of Flint Creek as well. To the north of Lamar Valley, where at present only bulls sum- mer, 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 re- ceived of an estimated 150 bison near Lake Abundance, just out- side the northeast corner of the park. Two small areas, separated by distance and topography from the four main valleys, have had small wintering mixed herd groups be- fore the study period, according to recent records. Approximately 40- 50 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 An- telope Creek basin on the north- east 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 the Madison Riv- er, although the bison wintering there in the 1950s may also have summered there. Bulls were not distributed pro- portionately among the four main wintering valleys, as shown in Ta- ble 7. Most of the Mary Mountain area bulls wintered in Hayden Val- ley. Lamar Valley had more bulls than did the Pelican area. In summer, bull distribution was widespread. Animals were so scat- tered 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 historical sources (Fig. 11). Winter distribu- tions within the park approximate those of early times, as do summer distributions on the Mirror-Upper The Bison Population 37 TABLE 7. Comparative distribution of bulls wintering apart from mixed groups. Lamar Pelican Hayden Valley Firehole Year No. bulls Total pop. % Bulls No. bulls Total pop. % Bulls No. bulls Total pop. % Bulls No. bulls Total 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 Lamar. Other summer distribu- tions 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 seg- ments of these two historical summer herds which wintered beyond the park boundaries are also gone. The recent Hayden Val- ley summering population seems larger than the historic popula- tion. Bison use of the valley may actually have increased, compared to former times, as the population became reestablished. Or the in- crease may not be real, but may result from incomplete historical information. Although present winter distri- butions seem little altered (except in total numbers) compared to his- toric times, the Firehole popula- tion 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 ear- ly low numbers. General Characteristics Physical Characteristics Appearance Bison are generally dark brown in color, almost black when a new coat is growing in during 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 coat ages, the longer hair over the hump and shoulders may lighten considerably, becoming almost tan on some animals, particularly old- er bulls. Shedding of old hair be- gins in spring, but many bison still have ragged patches of lighter- colored, old hair in mid-summer, particularly on the shoulders (Fig. 15). Wisps of this crinkly, shed- ding hair are commonly seen on trees and bushes (Fig. 16). Calves are reddish tan at birth (Fig. 17) but begin to lose this first coat and change to brown-black at about 3 months (Fig. 18). By about 5-6 months of age calves are com- pletely dark. The occasional red one seen in the fall is a late-born calf. Males and females generally resemble each other in color, shape, and presence of permanent horns. Both sexes have the shoul- der hump (calves do not) which, together with the longer hair on the foreparts and head, give a massive appearance to the front of the body compared with the hind- quarters. Bison are, however, sex- ually dimorphic (different in ap- pearance); older animals can be differentiated by an observer (Figs. 19-22). Horn size and shape is characteristic; additionally, bulls are larger and the head shape is broader and generally more mas- sive. The contrast between areas of long and short hair on bulls is more marked. Weight Weight differences are greatest between male and female adult bison. Weights (except adult bulls) were recorded in Yellowstone dur- ing the winters of 1964-65 and 1965-66, when adults weighed less (indicated by sequential winter 38 General Characteristics 39 Fig. 14. Clipped appearance of a mature bull. Photo by M.D. Beal, Yellowstone Na- tional Park. 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 usually weighed be- tween 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 the largest listed in the records of the Boone and Crockett Club (1964). This animal, a member of the Buffalo Ranch herd (see History) was shot in 1925 after he became too dangerous for the semiranch- ing operation of the time. Old park files indicate he was the off- spring of one of the plains bison cows which was pregnant when brought to Yellowstone in 1902. Hence this bull was of plains bison stock, rather than a hybrid off- spring of plains and mountain bi- son. 40 Bison of Yellowstone National Park General Characteristics 41 Fig. 17. Newly-born calves in a mixed herd group. Photo by Verde Watson, Yellow- stone National Park. 42 Bison of Yellowstone National Park Fig. 18. The calf (5-6 months old) to the left of the cow has lost its first red-brown pelage. Photo by David Condon, Yellowstone Na- tional Park. Fig. 19. Note head shape and relative size of the cow, left center, compared with the bull at right. Photo by David Condon, Yel- lowstone National Park. General Characteristics Fig. 20. Spike-horn bull, approximately 2.5 years old. Photo by David Condon, Yellow- stone National Park. 44 Bison of Yellowstone National Park Fig. 22. The horns of the adult cow (at right) are relatively slender compared with those of bulls. The spike-horn bull at left is approximately 3.5 years old. Photo by David Condon, Yellowstone National Park. Fig. 23. Old Tex, the Yellowstone bull whose head is still first among record bison heads listed by the Boone and Crockett Club (1964). Photo by James Kimber- lin, Yellowstone National Park. 46 Bison of Yellowstone National Park Life span Longevity in a wild bison popu- lation is usually less than that of animals in zoos and other protect- ed 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 years of 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 Grouping characteristics Bison are gregarious animals usually found in groups of various sizes, although there are scattered solitary bulls at all season. The vast herds (of plains bison) commonly mentioned by historians are not seen in Yellowstone. Small bands, typical of the original mountain bison population (as described by early travelers), are also character- istic at present. During the higher population levels of the 1950s, McHugh (1958) found that cow (mixed) group size ranged from 10 to 50 in Lamar during the win- ter, 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 pre- sent 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 sum- mer, 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 ani- mals) were solitary, but pairs and small groups up to four and five were common, particularly in win- ter. 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 na- ture of these bands is not clear. Fuller (1960) considered the ob- servations of various writers and concluded that there was a basic unit of some sort, centering around 11-20 individuals. Mc- Hugh (1958) concluded that subgroup and group formation General Characteristics 47 was flexible, with little dependence on blood relationship (except the cow with calf). Behavior in specific circumstances Historical references often men- tion that bison face into the wind during snowstorms. This may have been very common among plains bison when no shelter was available. Conditions which prevail during severe snowstorms in Yel- lowstone permitted few observa- tions during this study, but bison, when visible at all, were not seen standing head into the wind. Rath- er, 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 the wintering 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 consider- able head shoving, but actual bat- tles were never witnessed. Fuller (1960) witnessed shoving matches between bulls, but most encoun- ters were decided by threats. McHugh (1958) described battles but did not state that these were between unfenced bison bulls. The bulls do a great deal of bellowing, along with 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 can- adensis), but are usually part of a mixed herd group along with oth- er bulls of various ages. There was no evidence 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 with speed. They are capable of a top speed of 30-35 mph (Fuller I960) and are strong swimmers. Although large, they readily disappear in the forest, blending with the darkness of lodgepole pines. Senses and disposition Bison use the senses of smell, hearing, and sight. The sense of smell is well developed, and bison reaction to the odor of an observer is often more marked than reac- tion to sight or sound. Bison are typically alert and are wary of an observer whether seen or heard, but a careful approach to a view- point is often possible if the wind has not carried the scent to them. After an 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 more disturbing than one on horseback. 48 Bison of Yellowstone National Park -t-> +-> c s 3 3 cr cr >■ >■ >■ >« c S g 3 o 3 0* '35 CT 'efl o .HO 0 «w O o o So * c a a u P3 "y (3 >> 1) o s- V Si o fi3 « > O e )h H U o «i <2 J J S > — — iir e u 3 cr 2. 3 cr cr 3 £ fi la > >> J K S § —5 So 3 < & u 3 M 3 U - — . D- w O « C/l 8 I .2 8 3 General Characteristics 49 In winter a skier is usually detect- ed as soon as in view of a herd, al- though the skier may be a mile or more away. However, if the skier uses white clothing, approach to less than 100 yards is sometimes possible unless scent disturbs the bison. One exception to the usual wari- ness of bison is common. Solitary bulls are probably as aware of an observer in a given set of circum- stances as is a group of bison. However, these bulls are much more inclined to stand their ground, particularly near roads, where they are more accustomed to people. Their tolerance of ap- proach is misleading; they are not aggressive, but when approach is beyond tolerance, they will depart. The line of departure may be through or over unwary people who sometimes nearly surround one of these bulls. Observations made during this study concur with those of Fuller (1960), who reported that bison were neither aggressive nor un- predictable. He characterized the mixed herds as usually shy and timid and used the term "stolid indifference" for the bull groups. All bison should be viewed from a respectful distance. Visitor opportunities to see bison Bison behavior and habits (see Movements) influence opportuni- ty to see them from park roads (Table 8). Such viewing is best done from a vehicle, to minimize disturbing the animals and de- stroying the opportunity for oth- ers to watch. The visitor who is able and will- ing to penetrate the wilderness of Yellowstone on foot or horseback may, with luck, see the herd groups on their summer ranges. The herd groups in Yellowstone can be characterized as very elu- sive and very mobile, and a sight of them is not always 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 an experi- ence to be remembered and cher- ished. 521-650 O - 73 - 5 5 Population Characteristics This chapter discusses the REPRODUCTION and population structure and dynamics of Yellow- stone bison during the period 1964-68. A series of bison reduc- tions from 1961 through 1965 consistently removed a large num- ber of breeding-age females. Re- cords 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 popula- tion conditions. Sexual Maturity Incidence of pregnancy by age class for two Yellowstone studies 25 years apart are compared in Table 10 as an indication of sexual maturity in the female population. The 1940-41 study sampled the semiranched population of La- mar; the 1964-66 study sampled the entire free-ranging popula- tion. 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 indicat- ed that a few more bred as 2-year- olds and that approximately a fourth of the 3-year-olds were breeding. Both studies showed that the majority of females at- tained sexual maturity when 4 years old. Sexual maturity for the female population as a whole may be oc- curring somewhat later now. The 1964-66 study of wild bison showed fewer females pregnant in the 3.5 and 4.5 age classes (27 and 71%, respectively) compared with 1940-41 study of the semidomesti- cated bison (50 and 92%, respec- tively). Sexual maturation also may be later in the Yellowstone popula- tion of this study compared with 50 Population Characteristics 51 herds 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 (92 and 31 sampled, respectively) for 3- year-olds (Fuller 1962). At Wichi- ta, 74% (35 sampled) of the 3-year- old cows had calves (Halloran 1968). Sexual maturity of males was not studied in Yellowstone. How- ever, Fuller (1962) found that examination 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 oth- ers by 3 years of age. Halloran (1968) found that two experimen- tal bulls were effective sires as 2- year-olds. According to observa- tions made by McHugh (1958) in Hayden Valley in Yellowstone, males 8 years and older 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 ob- served 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 com- pared with the semidomesticated herd of 1940-41 (Table 10). Fe- males 3.5 years of age and older averaged 56 and 90%, respective- ly. Females 4.5 years and older averaged 62 and 90%, respectively. Table 1 1 compares reproductive data recorded at Lamar by Rush (1932a), several later unpublished compilations also made at Lamar, and this study of the entire popu- lation. The pregnancy rate of 52% for females 2.5 years of age and older determined in this study was the lowest recorded in Yellow- stone. The reason for this was not clear, because the age classes rep- resented in all previous compila- tions (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 semi- domestic 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. Yellowstone's present wild bison population showed a reproductive rate equal to the 52% reported by Halloran (1-968), and lower than the rate among all populations compared by Fuller (1962). Hal- loran attributed the low rate at Wichita Mountains Wildlife Re- fuge to high calf survival. Calves were known to nurse into their Bison of Yellowstone National Park Population Characteristics o o o © o o o o o © o o o o o o * H 00 M Of) fH CT> CM CM N CO 00 00 CO CM 00 Ifi N CM CM CM O CM CM cm •■H CM 2 ^ 16 O) 00 O CO CM CO if) ^ If) * If) CO CO f-H cm m O) CO CM C> CM O) rf« 00 -H fH I tr J J J2 e "S3 c B s s J C a c 3 o S >- i a •a c sf 1 2 a u •J 2 (S o CM CO m ifi m (0 ifS CM If) <£> <£> CD O C7> CD 54 Bison of Yellowstone National Park TABLE 10. Comparison of female pregnancy rates, by age classes, 1940-41 and 1964-66. No. sampled Percent pregnant Age class 1 940-4 la 1964-66 1 940-4 la 1964-66 2.5 2 7 0 14 3.5 4 11 50 27 4.5 13 7 92 71 Young adult 10 6 100 50 Adult 49 23 86 57 Aged 8 17 100 75 Entire sample 86 71 86 52 aFrom Skinner, Curtis K. 1941. Special report on Yellowstone National Park bison. Yell. Nad. Park Bio. Files, 715-03. Buffalo (General). Typed. second year of life, thus prolong- ing the physical drain on the cows (and perhaps influencing the pos- sibility of conception). Fuller con- sidered 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 re- productive rate determined by the present study. Although survival appeared high (see Calf Mortali- ty), no yearlings were observed nursing during the study- Only 4% of the cows (Table 11) examined during the mid-winter reductions were still lactating. Brucellosis in Yellowstone ani- mals did not appear to be a factor in the low incidence of pregnancy. 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 Fi- rehole 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 have occurred, abortions were appar- ently rare except in the crowded corral at the Buffalo Ranch (Dave Pierson 1968 pers. comm.). Quor- trup (1945) stated that brucellosis had little or no effect on the herds, as did Tunnicliff and Marsh (1935) and McKenney (Skinner 1941). Population Characteristics 55 o 5 1 * O ■S -a o 1 1 O bo 0. If .O. >> 3 *-> C/3 CM 0 10 CO t m 6 CO CT> co CO 56 Bison of Yellowstone National Park Differences in population age structure, as reflected in the sam- ples, partly explain differences in reproductive rates between the wild bison popultions of Wood Buffalo and Yellowstone National parks. Subadults and young adults formed a much larger part of the Wood Buffalo National Park sam- ples (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, in part related to severity of the winters. Both Yellowstone and Wood Buffalo National parks have severe 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 condi- tions during the winter. Trees provide protection from the wind. Differences in amount of wind were not as apparent. Yellowstone apparently has a more severe win- ter environment, for bison, than does Wood Buffalo National Park. The effects of the Yellowstone winters on subadults is suggested by the mortality among them, as discussed later. Winter conditions, perhaps through nutritional influ- ences, may delay sexual maturity among subadults. Houston (1968) suggested that animal nutrition during winter periods might con- trol yearling moose (Alces alces) ovulation rates. Robinette et al. (1955) attributed reproductive rates among yearling mule deer (Odocoileus hemionus) to the type of winter preceding that during which the pregnancy rates were determined. Possible variation in effects between mild and severe Yellowstone winters was not ob- tained 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 those from other ranges (Houston 1968). Other environmental fac- tors which were not apparent from this 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 esti- mated 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 fe- males and averaging 127 males/ 100 females (294 fetuses). This was slightly higher than the 1 12 males/ 100 females reported by Fuller (1962). Population Characteristics 57 o u a ■a c be V .£ 55 n 2 5s .3 * 13 "o 0 "§ — G $ fa 1 o U g .s s S 1*8 2 o S S -a d g u S 5 x 6 £ fa •a l 2 fa 1 « w W r* < H O (4-1 a a i ■a u "Eb O sS 8 58 Bison of Yellowstone National Park Number of Young at Birth No twin fetuses were noted in any of the above records. One in- stance of twins in the Lamar herd was reported (McHugh 1958). Other workers (Fuller 1962; Hal- loran 1968) and historical accounts agree that twins are rare. Population Structure Sex and age structure was sug- gested mainly by trap records made during live-trapping opera- tions from late December to late February in the winter of 1964-65, and from mid-January to mid- March 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 indicated by comparison of 1964-65 Mary Mountain early winter aerial count records (72 calves) and Nez Perce trap records (77 calves). Most yearlings were probably trapped. Success (indi- cated by the temporary backtags and the number of retrapped animals) was high in the 2.5- and 3.5-year-old classes, 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, particular- ly 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 addi- tion 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 pop- ulation sex-ratio information for animals 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 variabili- ty, when individual trap records are compared, among the percen- tages of females in the 2.5- and 3.5-year-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 years of life. Fuller (1960) also noted more males than females in the spike- horn, or 2.5- to 3.5-year-old group, but believed the identifica- tions were biased. By 4.5 years of age and older, differential survival cannot be distinguished from dif- ferential trap success. Trap records, together with the Population Characteristics o £ I Ho cm H 65 2 5 CM HO CM i 2 a 2 ^ Ho cm bS> H z - CM c ,3 a> Ho - kP H o 10 3 2 60 Bison of Yellowstone National Park 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 mini- mum bull population of 150 was estimated from the number of trapped bulls removed (48), the scattered bulls in Hayden Valley which could not be driven toward the trap (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 Moun- tain populations after the reduc- tions of the early 1960s removed large numbers of adult cows. The normal proportion may be the reverse; adult cows may outnum- ber adult bulls. Fuller (1960) be- lieved this to be the situation among the wild bison of Wood Buffalo National Park. Adult male bison may be "biologically expend- able" according to Etkin (1964), who states that sexual dimorphism (termed aggressive potential in bison) interferes with male surviv- al. Age classes were calculated for the Mary Mountain population, using the Nez Perce trap records of 1964-65 and the prereduction count of 480 bison. Mary Moun- tain herd records were used, rath- er than pooled data, because trap- ping success was high (68%), the sample was largest, and trapping 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 these percentages differ from those of a Yellowstone population not influenced by reductions is not known. 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 consid- erable variation because of reduc- tion programs. The lowest percen- tages recorded during the study for Lamar, Pelican, and Mary Mountain were 7, 14, and 7%, re- spectively, during the spring of 1965 after reductions in all three areas removed large numbers of cows. Thereafter, all percentages 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 Population Characteristics c 'I c 3 O s a S u 6 a i£ is d £ 65 A 5 Cu > O CO O CT) CO a> CT> CM i-H i-H CO CM CO o ^ - 64 Bison of Yellowstone National Park conditions of weather and animal visibility may have affected the quality of the counts. The percent- ages 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 from the same popula- tion that winter the pregnancy rate was 51%. The sampling may have been biased, 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. Subadult mortality Trap records (Table 13) suggest- ed considerable mortality among subadults. The records show that a progressive decline in numbers occurred between calf and year- ling, and between yearling and 2.5-year-old age classes. One ex- ception, an increase in percentage of yearlings compared- with calves at the Nez Perce trap in 1965-66, may have been caused by a shift of a mixed herd group from one win- ter range to another. Previous reductions (1961-62 in Lamar; 1962-63 at Nez Perce) may have affected the size of some age class- es, but do not explain the similar pattern of percentages 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% year- lings, 6% 2.5-year-olds, 67% older) suggested that half the calves which survive into their first win- ter 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), re- spectively. 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 and early April) at the end of the first and second years of life, rather than early in winter during the second and third years of life (see Other Mor- tality). 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 sub- ject to an unusually severe winter for several years, these percen- tages may approximate usual mor- tality among these age groups. Population Characteristics 65 Other mortality Natural mortality recorded dur- ing the study period totaled 49 animals. All but one occurred dur- ing the winter after considerable snow had accumulated, usually after January. The number of re- corded deaths were 38, 4, 3, and 3 for the winters of 1964-65 (a se- vere winter), 1965-66, 1966-67, and 1967-68, respectively. With the exception of a small mixed herd group (18 animals), all dead 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 found because of larger carcass size. Reductions, by removal of mixed herd animals, may have substituted for propor- tionately more natural mortality among cows and younger animals than among bulls. Natural mortality recorded annually over mild and average winters of the study period aver- aged less than 1% of the winter herd numbers. One or two ani- mals, usually bulls, were the most found dead in any one of the main wintering valleys. This was also the usual number found before the study period, according to earlier ranger reports, although popula- tion numbers varied considerably (Appendix IV). The amount of natural mortality associated with a severe winter such as 1964-65 was obscured by concurrent reduction programs, but the number of dead animals 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 subun- its of Lamar, Pelican, and Mary Mountain. Known losses, mainly reductions, are also shown. The reductions, held only in Lamar prior to 1954, accounted for the general downward trend in that area, although at the same time the population as a whole in- creased, influenced mainly by the steady increase of the Mary Moun- tain herd as it repopulated an area uninhabited by bison for more than 40 years. The peak popula- tion in the latter herd and for the total bison population in 1954 apparently coincided with in- creased use of the Madison Pla- teau-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, some- times large in size. In June 1952, 124 adults and 11 calves were seen. Since the 1954 peak, all popula- tion segments have decreased. 521-650 O - 73 - 6 66 Bison of Yellowstone National Park /9JS /940 /94S /950 /955 /960 /965 /970 Cumulative Populahcw a/umbexs & so* % zo° pi re i'l I !. /9JS /940 /945 /9SO /9SS /960 /965 /970 fcwcr/cws Fig. 24. Bison population trends from population counts, 1936-68. The 1955 reduction in the Mary Mountain area may have started the downward trend shown be- tween the counts of 1954 and 1956. The marked decrease in population numbers in the Mary Mountain and Pelican herds, and the smaller decrease in Lamar cannot be entirely due to the re- ductions 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 indi- cated by sightings of 20-30 dead animals in Pelican during an aerial census of late January 1956 (Jim Stradley 1968 pers. comm.). The following June, 32 dead animals were counted in the main valley (Larry Brown 1969 pers. comm.). Reduction only added impetus, apparently, to a natural occur- rence. Population Characteristics 67 Immediate increase in the La- mar numbers followed reductions when population levels remained well over 200 animals, before 1952, by which time the last ves- tiges of the Buffalo Ranch opera- tion (feeding of hay) ceased. Since then, Lamar has shown only very slow increase, although reductions have been few and comparatively small. Reported natural mortality (an occasional 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 fe- males (yearlings and older). After the 1965 reduction, only nine females (yearlings and older) and 10 female calves were released. The temporary effect of even small reductions on low popula- tion levels was apparent, but some increase (with recruitment of more breeding females into the popula- tion) expected by 1968 did not occur. This suggests that some fac- tor, other than reductions, may have retarded increase in this population at levels below 200 animals. The factor may be related to the change to a truly wild popu- lation, subject to natural environ- mental influences. The Pelican population in- creased from near extinction about 1900 to an estimated more than 100 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 be- tween 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 be- tween 100 and 200 animals. The lack of increase over fairly long periods of time suggests some bal- ance exists with environmental factors, in which factors favoring increase are usually offset by mor- tality factors such as winterkill. The 1954 peak may have occurred with exceptionally favorable influ- ences, which existed only briefly. The park-wide population counts do not suggest that periodic emi- gration 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 were reported 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 proba- bly accounted for the usual popu- lation increases in those areas. Population estimates for the en- tire park of 400 and 440 animals in 1967 and 1968, respectively, showed a 10% increment for that period. Reduction effects and in- sufficient population data preclud- 68 Bison of Yellowstone National Park ed calculation of annual increment over a longer period. Between 1965 and 1968, when the study ended, the bison popula- tion 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 the influence of reductions. Environmental conditions have continued to exert major influence on the bison populations in con- junction with the activities of man. Population trends (since the near extinction of the original wild population about 1902) apparent- ly 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 condi- tions of semidomestication (La- mar), and when favorable environ- mental conditions combined with availability of an extensive, unin- habited area (Mary Mountain). Later increases were apparently offset by reductions (Lamar), or by reductions in combination with periodically severe environmental conditions (Pelican, Mary Moun- tain). At lower population num- bers, less severe environmental conditions appear adequate to have offset increases and to have resulted in periods of near stability or very slow increase in all popula- tion segments. Presumably, the original wild bison population which inhabited the Yellowstone area throughout the year lived in some balance with the prevailing environmental con- ditions of that time. Fluctuations in numbers undoubtedly occurred as favorable conditions alternated with periodically 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 num- bers of some of the predatory and grazing mammals have decreased. The bison population may be ex- pected 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 with natural environmental conditions. 6 Mortality Factors Parasites Internal parasites Yellowstone bison appear comparatively free from internal parasitism. During the present study, parasite investigation cen- tered on the occurrence of lung- worm (Dictyocaulus sp.), as report- ed by Meagher (1966). Rate of infection for 185 animals exam- ined was 11.4%. Aged animals, with an incidence of 35%, showed the highest rate of infection, con- trary to the situation in cattle, where calves show both higher in- cidence and intensity of infections. Dictyocaulus sp. has been reported from a few animals in Wood Buf- falo National Park (Fuller 1961), from the National Bison Range (Locker 1953), from Elk Island National Park (Conner and Cor- nell 1958), and from a fenced herd in Kansas (Frick 1951). No other internal parasites were found in the brief examinations made of bison during the present study. Locker (1953) recorded only tapeworms (Moniezia bene- deni) in Yellowstone bison, occur- ring randomly among all age groups, at an apparently low in- tensity of infection. A variety of internal parasites which have been recorded from other bison herds have not been found here. External parasites External parasites were not col- lected from animals during the study period. Burger (1967a, 1967b, 1969 pers. comm.), who studied biting insects in Yellow- stone during 1966 and 1967, re- ported that mosquitoes (Aedes sp.), blackflies (or buffalo gnats), particularly Simulium venustum, horse and deer flies (Tabanidae), snipe flies (Rhagionidae), and members of the Muscidae may all have had some association with bison. The last two families were most important. The genus Symphoromyia of the Rhagionidae apparently influ- enced 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 sum- mer, bison are nearly naked, as the 69 70 Bison of Yellowstone National Park newly growing hair is very short, resembling fine, black plush. They are particularly vulnerable to bit- ing insects. Three genera of Muscidae were associated with bison in Yellow- stone. The stable fly (Stomoxys calcitrans) and the horn fly (Hae- matobia irritans) were observed feeding on bison with no noticea- ble effect. The face fly (Musca au- tumnalis) 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 conjunc- tivitis associated with the presence of this fly among bison at the Na- tional Bison Range. Diseases Disease-caused mortality was not identified in the present wild bison population, although out- breaks of hemorrhagic septicemia in 1912, 1919, and 1922 caused considerable mortality in the intro- duced herd in Lamar Valley. In two instances during the study, young animals died from 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 for several days at Old Faithful before she died. Both carcasses were nearly consumed by scavengers before examination was possible, but the fat-depleted bone marrow in both cases indicated very mal- nourished animals. Neither tuber- culosis 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 Brucella abortus, occurs in the present bison popu- lation. Whether the organism was introduced or was endemic 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 in different years during reduction operations, and also among the wintering populations of a given year. In 1964-65, 129 animals test- ed 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 brucel- losis has little effect on the Yellow- stone bison. Limited examination of reactors slaughtered during the study period indicated normal pregnancies. Rate of pregnancy was apparently not influenced, as discussed previously. Veterinari- ans who investigated brucellosis in Yellowstone before the study peri- Mortality Factors 71 od agreed that there were no ap- parent effects on the population (Tunnicliff and Marsh 1935; Skin- ner 1941; Quortrup 1945). Quor- trup mentioned that few abortions were observed and gross lesions were rarely seen at postmortem examinations. Dave Pierson, Buf- falo Herder and Animal Keeper over a period of 30 years, believed that observed abortions occurred as a result of the handling of preg- nant females in chutes, and their confinement in pens during the reductions held at the Buffalo Ranch (1968 pers. comm.). Quor- trup believed that brucellosis had probably existed in the Yellow- stone 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 brucellosis-free condition as part of the U.S. Department of Agriculture brucellosis control program. In Wood Buffalo Na- tional Park in Canada, where the presence of brucellosis was con- firmed in 1956, Fuller (1962) con- sidered it a possible influence on conception rate. Choquette et al. (1966) also assumed that brucellos- is influenced productivity. Among cattle, effects include abortion of calves, temporary sterility, and lowered milk production (Gilman and McAuliff 1956). 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 popu- lation within levels which the habi- tat can support. Brucellosis is of economic con- cern to cattlemen, and of health importance to the general public. It is presumed that bison can transmit brucellosis to cattle, be- cause the causative organism is apparently the same in both spec- ies of bovids. Transmission tests have not been made to verify this, but on the basis of the assumption, the National Park Service has co- operated with the Department of Agriculture in brucellosis control among bison. In Yellowstone, cooperation has consisted of vacci- nation of calves and removal of reactors during reductions (held primarily to cut herd numbers). This cooperation resulted in re- duction of animal numbers below the park's management objective at Lamar in 1964-65. No reduc- tions have been held specifically for brucellosis control in Yellow- stone. Participation in brucellosis con- trol in Yellowstone National Park has recently been reevaluated by the National Park Service (Bar- more 1968). Present bison man- agement objectives are to maintain a wild population under natural conditions. By order of the Super- 72 Bison of Yellowstone National Park intendent of Yellowstone National Park, future reductions will be held only when research clearly indicates that compensation for a lack in natural controls is neces- sary. As an alternative to brucellos- is control within the park, the objectives of the Department of Agriculture control program can be met by preventing contact be- tween park bison and domestic livestock beyond the park bounda- ries (see Movements Beyond Park Boundaries). Predation There was no direct evidence for predation on the present herd. Circumstances suggested a grizzly kill of an apparently healthy, ma- ture bull in mid-summer of 1967. Remains of bone and hair indicat- ed 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 site of death all suggested a grizzly (Ursus horribilis) 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, but calf counts during the study do not indicate much loss. However, such loss might have occurred 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 Yellow- stone. Studies such as that made by Mech (1966) have indicated that effective wolf predation on large mammals results from the cooper- ative 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 addi- tional 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 im- paired, she was usually with other 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 free from predation. Old bulls, obviously weak, were often ob- served for several winter months in nearly 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, particu- larly wolves, were more numer- ous, healthy bison of all ages were relatively safe from attack. Al- though predation becomes more difficult as the prey species de- creases (MacArthur and Connell Mortality Factors 73 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 of climatic stress, forage availability, and physiologi- cal condition of individual ani- mals, was the main cause of ob- served mortality (see Other Mor- tality). Death usually occurred af- ter prolonged weakening, often in late winter (March and early April). A few animals died annual- ly, but the number increased greatly with severe winters. This suggested that climatic influences (long winters, periods of pro- longed cold, deep and sometimes crusted snow) acting directly and indirectly on the bison were the most important mortality factors. The most apparent direct effect of the winter environment, above the energy levels required to main- tain body temperature, was the effort required to travel between foraging areas. In deep snow the mixed herd groups usually trav- eled 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 traveling bison. 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 (by swinging the head in a sideways motion) with appar- ent 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 var- ied according to physical condi- tion, as would be expected. Aged animals found dead in mild and average winters indicated that they 74 Bison of Yellowstone National Park were most susceptible. Crippled and otherwise handicapped ani- mals, and those weaker because of size, would also be affected more quickly. Differential and total mor- tality among subadults, as dis- cussed previously, suggested that among otherwise healthy bison of all ages they were most vulnerable. Size, together with social standing in the population (see Suggested Mechanisms of Population Regu- lation), may explain this. A quick-acting type of winterkill occurred once during the study period, but old bison bones indi- cated similar occurrences in the past. During the severe winter of 1964-65, a group of 18 bison (in- cluding 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 Be- chler Meadows. The snow there, west of the Continental Divide, Fig. 26 Bull bison foraging in snow approximately 2.5 feet deep. Fig. 27. Feeding site in snow approxi- mately 2 feet deep. was too deep that winter to allow the animals to move away from the slough area, and presumably they starved to death when the small amount of feed was gone. The slough area apparently becomes a unique trap 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 indicat- ed by ranger reports. Most com- monly animals drowned in bog holes or fell into hot pools. 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). 7 Habits Calving Comparison of records kept during the study period with ear- lier information suggested that the onset of the calving season is later than formerly. From 1937 to about 1950, the first calves were regularly reported in Lamar be- fore mid-April. Since 1950, first calves 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 oc- curred during the first half of May, and calving season was over by the end of May. There were always a few late births; occasional- ly a new calf was seen in late sum- mer. (Subsequent to this study, calving season has extended into June as the population has in- creased.) Fetal size information compiled before the study period also sug- gested that a large part of the calv- ing extended over a longer period of time. Rush (1932a) reported only that there was considerable variation. E. R. Quortrup's unpub- lished data (Skinner 1941) indicat- ed a size range from a 2-inch em- bryo 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 same time (early May). Observations of the earliest calves were rarely possible except in Lamar (because of limited ac- cess before 1 May), but the few records made by rangers for the Firehole suggested that first calves are usually born there perhaps a week later than in Lamar. Calves were born on the winter- ing areas (Fig. 28), except for the occasional late one. In Lamar dur- ing 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 predat- ing the study indicated that this same area was the usual place of calving. In Pelican, most calving occurred in the eastern half of the main valley from Astringent Creek to Raven Creek. Mary Mountain animals calved in both Hayden 75 76 Bison of Yellowstone National Park 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. and Firehole valleys. On the Fire- hole, most calves were born in the Lower Geyser Basin areas of Senti- nel Creek, Fairy Meadows, Pocket Basin, lower Nez Perce Creek, and the Firehole Loop. Most Hayden Valley calving occurred in the western half of the big valley, near Alum Creek. 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 the rut in 1967, all of the ani- mals were at the crest of the Absa- roka Mountains on the east boundary, 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 of these animals crossed the Lamar River to the Mirror Pla- teau, where breeding activity oc- curred from the meadows south of Amethyst Mountain south to the meadows at the headwaters of Pel- ican-Timothy-Raven creeks. Most of the breeding activity in the Mary Mountain herd occurred in the southwest corner of Hayden Habits 77 Valley and adjacent forest and meadow areas. In all of these areas there were small uprooted coni- fers and many rubbed trees. Small wallow-sized patches of grass (Fig. 29), apparently uprooted by horn- ing but not much used for wallow- ing, were another common sign of rutting activity. The period of breeding activity observed during this study (1963- 68) was shorter than that given by McHugh (1958). He observed in the much larger Hayden Valley population of that time that the season extended from 15 June to 30 September, with less activity during the first and last 2 weeks. Movements Migratory movements Most of the bison in Yellowstone are migratory, moving in spring from the lower wintering valleys to higher summer ranges, and re- versing 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 val- leys. Although all groups of a par- ticular wintering area did not move at once in spring, they all moved within a few days' time. Records kept during the study showed that mixed herd groups 78 Bison of Yellowstone National Park 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 ani- mals moved to Hayden Valley or the Little Firehole Meadows area of the Madison Plateau during the first week of June, 3 of 4 springs. Wintering groups began to move from lower to upper Pelican Val- ley at the same time. Some years, further movement across the Mir- ror Plateau to the Upper Lamar area was delayed until mid-June. Observations suggested that near- ly every year the entire Pelican population, except some bulls, crossed to the Upper Lamar, re- turning to the Mirror later in the summer. Most movements took place along definite travel routes, as shown in Figs. 30 and 3 1 . The bulls that wintered as soli- tary animals, or in bull groups, left the wintering areas gradually dur- ing 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, at Mary Bay, and in Lamar Valley almost to the end of June. The bulls followed not only the routes used by the mixed groups but moved upcountry along the various stream drainages to scatter widely on the summer ranges. The cause of the spring move- ment was not clear. In 1966, an earlier spring than others of the study, 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 from the new spring growth of the upper Pelican Val- ley, across high meadows, which were mostly covered with snow or standing water, to the Lamar Riv- er. By the third day they were on the greening slopes of Little Sad- dle Mountain. They did not follow any discernible vegetation or snow melt sequence. Spring weather patterns and temperatures pre- sumably influenced the migration. 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 ap- peared in the main valley (to stay) by late November. Some groups were reported in the Lower Gey- ser Basin about the middle of Sep- tember most years, 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 ear- lier 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. Habits 79 Habits 81 Bulls commonly began to ap- pear on winter ranges before herd groups were reported. The move- ment was gradual, continuing for some time after herd groups moved in for the winter. Most win- ters, 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 win- ter ranges; immediately after a fall storm, in temperatures often near 0°F, herd groups which had moved down returned to high ele- vations. 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 early summer. 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 the fall 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 Fig. 32. Bison herd groups on Alum Creek in the western part of Hayden Valley. 82 Bison of Yellowstone National Park Fig. 33. Bison on the strip of sedge meadows along upper Alum Creek south of Hay- den Valley. ranged the small meadows and parks scattered in the extensive 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. Pelican and Lamar wintering herds were seen in early summer on the lower ridges of the Upper Lamar (Mount Norris, the western ends of the Cache-Calfee and Mill- er Creek ridges, and Little Saddle Mountain). By the end of June to mid-July, they moved higher, to the east boundary (Fig. 34), rang- ing 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 the La- mar River to the Mirror Plateau, where they ranged the northeast rim from Flint creek to upper Raven Creek until the shift to win- ter range. At higher population numbers than those occurring during this study, groups also commonly moved the length of Specimen Ridge on the north edge of the Mirror Plateau (Dave Pier- son 1968 pers. comm.). Apparent influences for move- ment of groups over large areas during summer were the rut, sea- sonal vegetation changes (see Use of Forage Areas), and, most ob- viously, biting insect populations. Small, gray, biting flies were par- ticularly noticed on the Mirror and Habits 83 Fig. 34. A herd group on the east boundary near Canoe Lake in early August. Photo by John Good, Yellowstone National Park. the Upper Lamar in 1965. In 1967, the flies were numerous in those areas, and in Hayden Valley also. From mid-June to mid-Au- gust 1965, neither aerial flights nor ground checks showed mixed herds on the Mirror Plateau, al- though in 1966 groups were seen there by 24 July. From mid-June to early August 1967, herd groups were observed only once in Hay- den Valley, but were seen, from the air, to the south. Every year herd groups were seldom ob- served in Hayden Valley during much of July when biting insects were at their worst. Burger (1967a) compared biting insect populations and animal dis- tribution in 1966 and 1967. He noted that the distribution and abundance of species of Sympho- romyia, a small gray biting fly, par- ticularly 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 high on the east boundary, at ele- vations of 9500-10,000 feet, for more than 2 weeks in late July and early August 1967. Other sum- mers, although the same boundary area was used by bison, they did not remain as long and were more broadly distributed. Apparently, the insect popula- tions influenced bison distribution and concentration more strongly 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 activi- ty began to diminish. 521-650 O - 73 84 Bison of Yellowstone National Park The spring and fall migratory habits of the Yellowstone bison did not prevent animals from occa- sionally visiting areas of winter range during the summer. Ob- servations made during the study period and earlier ranger reports indicated that scattered bulls sometimes appeared on all winter ranges. When population levels were higher, mixed herd groups also occasionally visited winter ranges for brief periods, according to ranger reports. Such groups were sometimes seen in the main Lamar Valley in mid-July, or more commonly, in August. Mid-sum- mer movements of groups rarely occurred to areas near roads in the Firehole. No groups were report- ed 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 the limits 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 and for greater dis- tances, but sometimes stayed in one locality for days or even weeks. Bull groups 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 food require- ments. Winter conditions hin- dered but did not prevent occasion- al extensive movements by groups and single bulls between main win- tering valleys. Reasons for such moves were not apparent, but for- age requirements did not appear to be a factor. No movements to areas of high summer range dur- ing the winter are known; the soli- tary 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-aver- age snow depths, most of the herd animals crossed of their own voli- tion a few days later. The follow- ing winter, during the 1965-66 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 such crossings, uninfluenced by reduction operations, was un- known. Mid-winter movements between Habits 85 Lamar and Pelican valleys appar- ently involved only bulls. Some- time between early December 1965 and mid-January 1966, a marked young bull crossed from Lamar, presumably by way of the Mist Creek divide. Rangers report- ed 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. Movements between Pelican and Hayden valleys apparently oc- curred 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 re- ports indicated an occasional group in late fall. Jim Stradley (1968 pers. comm.) observed from the air about two dozen cows and calves 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 in- volved one or more bulls. Most years some bulls summered be- yond the north boundary. Since 1951, a few bulls have been report- ed almost every year beyond the southwest boundary in Idaho. These movements have occurred regardless of fluctuations in popu- lation numbers. Mixed herd groups have only been reported beyond the north boundary of the park. Late during the winters of 1943 and 1948, groups briefly left the park near Gardiner, Montana. Severe weath- er 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 the boundary on Elk Creek in the Hellroaring area (R. Murphy 1970 pers. comm.). All these mixed-group movements occurred when larger numbers of bison wintered in Lamar. Mixing of Population Segments Census records, aerial observa- tions, and the limited records of neckbanded bison (Fig. 36) indi- cated that movements of popula- tion groups affected numbers in- habiting the winter ranges from one year to the next (population shifts), and resulted in interbreed- ing between populations of winter- ing areas during the summer. Movement occurred during the fall and winter between the valleys 86 Bison of Yellowstone National Park Fig. 35. Map showing known locations of bison movements across the boundaries of Yellowstone National Park. of the Firehole, Hayden, Pelican, and Lamar, as previously dis- cussed. Observations confirmed the assumption made by. park per- sonnel some years ago that the extent and frequency of mixing between the Firehole and Hayden Valley animals during most of the year, including the breeding sea- son, justified considering them as one population, called the Mary Mountain herd, distinct but not isolated from the other two herds. Shifts of other population groups were indicated by some fluctuations in actual winter counts from 1935 to 1950 (Fig. 37). De- creases in Lamar winter numbers Habits 87 Fig. 36. Neckbanded bison in a group at Pocket Basin on the Firehole. Photo by John Douglass, Yellowstone National Park. /935 /940 /945 /9S0 II I I 1 I Fig. 37. Population fluctuations in win- tering areas caused by shifts of mixed herd groups. coincided with increases in Pelican in 1937, 1941, and 1942; decreases in Pelican winter numbers coin- cided with increases in Lamar in 1940, 1943, and 1949. Reductions, made only in Lamar during this period, probably added to the amount of decrease there in 1941 and 1942, but could not have in- fluenced the 1937 decrease nor any Pelican decreases. Bias in Peli- can population counts made by rangers on winter ski trips might account for some variation, but not the coincidence of changes in population numbers in the two valleys. Mixed herd groups which moved between Lamar and Peli- can in late fall and early winter probably remained on the winter range that was in use when weath- er conditions worsened. Shifts between Pelican and Hayden Valley were infrequent 88 Bison of Yellowstone National Park and less obvious. Such shifts did occur in 1941 and 1946 (Fig. 37). Other shifts have occurred since, but the less frequent population counts made after 1950 gave no indication. During the study peri- od, aerial observations and reduc- tion records suggested two shifts occurred. Mary Mountain popula- tion counts after the 1964-65 re- duction totaled fewer than the expected number of animals, based on numbers seen before trapping began (480), numbers removed (238), and possible natu- ral mortality. A move of animals to Pelican after the early December count would explain the discrep- ancy. The next winter, in the re- duction of 1965-66, 47% of the animals (yearlings and older) trapped at Nez Perce had no metal eartags, showing they had not been 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 (34 ani- mals) wintering in Bechler Mead- ows in 1962-63 also indicated this. No herd group was reported there in 1961-62 or 1963-64. Over a span of time, the wintering num- bers of the Mary Mountain, Peli- can, and Lamar population seg- ments would be unaffected by such shifts. Observations of both total num- bers of animals and individuals neckbanded in Lamar showed that, during the breeding season, intermingling of the Lamar and Pelican wintering groups was ex- tensive 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 interbreed- ing which presumably would occur in such circumstances suggested that these bison also be considered one population segment. Howev- er, because winter season move- ments were so few, the separate designations were retained. Separation was most complete between the Mary Mountain pop- ulation and the Pelican-Lamar animals. The infrequent move- ments between Pelican and Hay- den Valley at any time, coupled with the separation of the popula- tion segments during breeding season, resulted in almost no inter- mixing. Historically, when there were large summering populations (parts of which wintered beyond the park area) north of the Lamar and west of the Firehole, inter- breeding between the wintering populations of the Lamar and Peli- can valleys, and of the Firehole and Hayden valleys, was probably less extensive because of geo- graphic separation of some groups during the summer. Then as now, however, the groups which shared summer ranges undoubtedly in- terbred. Before intensive poach- ing greatly reduced numbers and Habits 89 probably altered or eliminated habitual patterns of movement, there may have been more contact between Pelican and Hayden Val- ley animals, but the amount of in- termingling and interbreeding was probably least, even then, of the population segments. Geographic separation during the breeding period through sea- sonal migration to higher summer ranges, seen in the present park bison on a local scale, could ex- plain the existence of two recog- nized subspecies of bison in histor- ic times whose distribution pre- sumably overlapped in the Rocky Mountains (Skinner and Kaisen 1947). Possibly the mountain and plains types jointly used some win- tering places along the east side of the Rockies, but breeding isolation kept the populations distinct. The apparent temporary nature of group population shifts be- tween main areas of winter range, discussed previously, and neck- band records both suggest that animals have affinities for particu- lar winter ranges. Neckband rec- ords for the Mary Mountain herd showed that some individuals pre- ferred one winter valley to the other, regardless of movement between the two valleys at all sea- sons. The entire population (ex- cept for the many scattered bulls) had crossed to the Firehole side during the winter of 1964-65 when helicopters drove them to- ward the trap on 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 the Fire- hole side to the trap on Nez Perce Creek. Aerial observations after the trapping showed that 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 2-year-old cow, and two young bulls. Three marked adult cows wintered on the Firehole in both 1966-67 and 1967-68 although they were iden- tified 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 winter habitually in the same valleys was stronger among mature females. Marked animals of all ages were seen on various parts of the summer range, including Raven Creek on the Mirror Plateau (close to Peli- can Valley), but only three imma- ture bulls and two immature fe- males spent at least one winter in Pelican Valley. Cows marked as adults (five marked) were identi- fied in winter only in the Lamar Valley, two of them for three suc- cessive winters. 90 Bison of Yellowstone National Park A tendency for animals, particu- larly mature females, to prefer a given winter range might explain the lack of any lasting interchange or permanent shifts by groups from one winter range to another. The lack of emigration to new ter- ritory, such as from Pelican to Hayden Valley before the rein- troduction of 1936, might also be explained. Possibly, except for young animals or old bulls, inter- change between wintering valleys involved only groups. Although the basis of such groups is not known, observers generally agree that a group structure exists. Ful- ler (1960) believed there was a unit of some sort. McHugh (1958) be- lieved 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 deep snow, 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 move- ments of both individuals and groups result in a varying amount of separation among population segments which winter in the val- leys of the Firehole, Hayden, Peli- can, and Lamar (Table 16). The Yellowstone bison of the present (and recent past) remain almost entirely within the park bounda- ries throughout the year. Those that range to the northeast (Lamar and Pelican) are almost separate from those designated the Mary Mountain herd. Affinities for giv- en winter ranges 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 groups prevent total separation of any one part of the population. Food Habits Results of analysis of 22 rumen samples, half of them collected in the winter and half throughout the rest of the year, are shown in Table 17. The 1 -quart sample tak- en represented approximately 1% of the rumen-reticulum volume of 91 quarts averaged from eight adult males. Approximately two- thirds of the samples were taken from adult males. Because of some uncertainties in distinguishing between sedges and some grasses, doubtful material was placed in the grass category. Sedge may thus be underrepresented in the analy- sis. Grasses and grasslike plants formed most of the diet through- out the year. Totals were 99, 96, 91, and 99% for winter, spring, summer, and fall, respectively. Sedge was the main source of for- age at all seasons, averaging more than half the diet. Its value in win- Habits 91 TABLE 16. Comparative summary of movements shown by the present wintering populations. Firehole-Hayden Valley Populations Pelican-Lamar Populations Winter separation Group movement between valleys Partial Frequent — year around Almost complete Least frequent — fall and early wintera Almost complete Infrequent — fall and early winter Seasonal migrations Summer interbreeding Amount of movement on summer range Amount of movement on winter range Less marked Complete Range less widely (except Madison Plateau) Varies among herd groups, bull groups, and solitary bulls Quite marked Complete Range widely Varies among herd groups, bull groups, and soli- tary bulls Movement beyond boundaries A few bulls, SW corner A few bulls, N&E boundaries, sum- mer; herd groups, N boundary, Summary: Population separation One population: Mary Mountain Almost separate One breeding pop- ulation, with winter range designations as Lamar and Pelican Applies to relationship between Hayden and Pelican valleys. ter (56%) reflects the animals' fre- quent concentration during this season on sites where nearly all the plant growth is sedge. Grass, sec- ond in quantity during all seasons except fall, averaged more than one-third of the diet for the entire year. Its highest value (46%) in spring probably reflects both greater palatability and increased 92 Bison of Yellowstone National Park a B o U u vo m © u » >n « h « o o o o o o (C N n w W h h CM a B o u 65 ffi N O (N | ft w eo w o o o o o o o o I I I I I I 8 8 I co co l I I I CO CO © CM 00 a> in « o o o o o o o o o m o m in O i i? O m if) CM in a ^ h O) ^ mm© N M O I I I I I I I I I ft >n w o o o o o o o o m oo 0 u 2 2 CO I I oo I I I I I I I u a S 2 W So & is £ o £ CL. ill O T3 3 o 2 2 u o S eg Habits to u c "a •c B a m (A fe5 a E 6 to fe5 d S o U £ o U 6? a B o U u w u 1^ CM CM CO Q -a c ll £5 1 s 111 J K 2 J D 94 Bison of Yellowstone National Park 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) aver- aged 3% of the spring diet; north- west 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 nutri- tionally. 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 diet but oc- curred in only one of the four samples. Its presence may be inci- dental to the summer use of for- ested areas where it is common on the forest floor. Other browse plants shown in the analysis may also be incidental to feeding at a particular site. Their possible importance nutritionally is un- known. Forage composition data for the bison use areas represented by the food-habits analysis are limited. Descriptions of species composi- tion for the Lamar Valley are con- tained in Rush (1932b). The Soil Conservation Service (1963) and Bergstrom (1964) provide some quantitative data. Descriptions of species composition and abund- ance at higher elevations of the Lamar area were made by Olde- meyer (1966) and Woolf (1968). Hayden Valley species are men- tioned by Kittams (1949) and the Soil Conservation Service (1964). From these sources and informa- tion obtained during this study, a list of grasses and grasslike plants was compiled according to site (Appendix VII). Forage composi- tion information for the thermal sites used by bison during critical winter periods (see Use of Ther- mal Areas) has not been deter- mined. Wet bottomlands, creek banks, and pond edges support dense sedge growth (mainly Carex aqua- tilis, beaked sedge, and Nebraska sedge). Slightly less wet sites sup- port a greater variety of sedges, horsetail, wire rush, and grasses such as sweetgrass, timothy (par- ticularly in Lamar), 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 the most commonly observed additonal species. Horse- tail, 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 Habits 95 wheatgrasses occur in most areas; the sedge Carex xerantica is com- mon in Lamar. At higher elevations on moun- tain herbland sites, sedges such as Carex raynoldsii and smallwing sedge are prominent. Rushes, bluegrasses, Idaho fescue, moun- tain brome, needlegrass, wheat- grass, alpine timothy, and tufted hairgrass are all common. Subal- pine meadows have fewer sedges (mainly Carex raynoldsii and Hepburn sedge). Grasses are pre- dominantly bluegrasses and tufted hairgrass. 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 availa- bility did not appear to be a popu- lation-limiting factor most of the time. Conditions under which for- age might be a limiting factor were suggested but not established by this study. Bison, in turn, influ- enced their foraging areas (see Effects on Habitat). Grasses and grasslike species which commonly occur in some forage areas are list- ed in Appendix VII. During the winter, most bison concentrated on sedge sites for their forage. At Soda Butte in Lamar, 30 or more bison concen- trated at times, and a few to a doz- en bulls stayed all winter long. 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 re- cords showed that herd use was constant, much of every year, along the Pelican Creek bottoms where snow depths permitted. In Hayden Valley, some years, the mixed 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 these sedge 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 Ther- mal Areas). Use of specific upland sage- brush-bunchgrass areas on the winter ranges apparently varied more from year to year. In 1965- 66, on aerial observation flights, animals were observed most fre- quently on the north side of Peli- can Creek, at the lower end of As- tringent Creek, and to the west for 2 miles. The next year they were usually observed on the slopes of the southeast edge of the valley, in the vicinity of the old bridge over Pelican Creek. A third year they 96 Habitat Relationships 97 were in the east end of the valley. Only three times during 30 years of ranger ski patrols and once dur- ing the present study were mixed herds seen at the Mushpots-Mud- kettles area of the upper valley in winter, although they crossed this area in spring. In Hayden Valley one year, the herd groups, when not on Alum Creek, ranged the north-facing slopes of the hills on the south bank 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 specific sites also existed on the Firehole and in Lamar. Presumably, vary- ing patterns of snow drifting, crusting, and melting which affect- ed forage availability influenced these shifts of use on upland sites. During spring, summer, and fall, bison use of forage areas con- centrated less on any one place or type. Use of sagebrush-bunchgrass sites increased particularly in the spring, but during all three sea- sons bison were more commonly seen on swales and lusher mead- ows where sedge species composed much of the vegetation, even at high elevations. Use of forested sites for feeding was usually limit- ed to the more open growth and seemed incidental to other influ- ences (rutting activity, shade needs, escape cover, travel, escape from insects). At no time did for- age appear limited during these seasons, either for the present populations or for the higher populations of the past. Observations indicated that al- though 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 reached high- er elevations. Movement among the main use areas of swales and lush spots was considerable, prob- ably because these places were usually small in extent and widely scattered, although numerous. Local movements at all seasons appeared influenced by intersper- sion 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 and upland sites. Present observations were limited to rela- tively low population numbers and were made during mild and aver- age 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 bi- son to reach these sites, and the 98 Bison of Yellowstone National Park direct physical influences of pro- longed cold or storm conditions. Forage in these sites appeared quite limited; thus these sites may be a population regulation mecha- nism influencing mortality accord- ing to the numbers of bison forced to use them and the length of time they stay. Use of Thermal Areas Bison utilized wintering sites which were influenced by the widespread thermal activity in the park. The amount of use varied with the size of the bison group (solitary bulls, bull groups, mixed herd groups) and the kind of ther- mal influence. Thermal activity refers to sites where thermal fea- tures (geysers, hot springs, fumar- oles) are located. The ground at these sites is usually 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 ther- mal features but warm ground results in small snow-free areas or larger areas where snow does not accumulate as deeply as it would without the thermal influence (Figs. 38-41). One to several bulls used sites of thermal activity (Fig. 42) more Fig. 38. Snow-free bison feeding site on warm ground at the edge of Fairy Meadows in the Firehole. Habitat Relationships 99 Fig. 39. The same site shown in Fig. 38, in early summer. than larger bull groups and mixed herd groups did, but these sites were not used by a majority of such bulls. Scattered bulls were habitually found at various places in the Firehole, at the Mud Vol- cano 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 of the bulls which wintered apart from the mixed herd groups were located where there was neither thermal activity nor the influence of warm ground. Both Lamar and Hayden Valley had proportionately more of the Fig. 40. Site along Alum Creek in Hayden Valley where warm ground causes snow to melt early. 100 Bison of Yellowstone National Park Fig. 41. The same site shown in Fig. 40, in summer. total number of the wintering bulls, as discussed previously. In both valleys, most of the solitary bulls and bull groups were ob- served apart from any site of ther- mal influence. Herd groups were seldom seen at sites of thermal activity but of- ten used areas of thermal influ- ence, particularly sedge bottoms where snow depths were less (junction of Alum and Violet 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 Astrin- gent 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 wintering valleys, were thermally influenced places little used by mixed herd groups; thermal activity is least there (ex- cept Soda Butte). Fig. 42. Bison bull wintering among active geysers and hot springs. Habitat Relationships 101 Fig. 44. The Firehole River is open all winter because of an influx of hot water from geysers and hot springs along the banks. Photo by Karl Bittler. 102 Bison of Yellowstone National Park Fig. 45. Sedge growth along the banks of the Firehole River provides forage for bison and elk moving in the open water. Total use by all bison of areas where thermal influence alleviated otherwise more severe winter con- ditions involved was more than the use of thermally active sites. In the Hayden, Pelican, and Firehole val- leys, the amount of use of sedge bottoms with lessened snow depths, and of ice-free streams, indicated that thermal influence was important in maintaining win- tering populations. In Lamar, where winters are comparatively less severe, the lack of thermal 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 influ- ence where small, warm, snow- free patches occurred, sometimes in conjunction with the activity of a few hot springs or fumaroles, were of great importance to the bison population during brief but critical periods. During the pro- longed very cold spells of the se- vere winter of 1955-56, Jim Strad- ley (1968 pers. comm.) observed mixed herd groups in the scat- tered small, warm areas west of Astringent Creek in the Pelican area, in the Mud Volcano area of Hayden Valley, and just east of the Firehole River (Pocket Basin) in the Lower Geyser Basin (Firehole). During the study, herd groups were seen in these same Astrin- gent Creek areas of Pelican (Fig. 46) late one winter (1968) after a stormy period and presumably were there the few other times Habitat Relationships 103 Fig. 46. Bison in one of the scattered small thermal areas west of Astringent Creek in the Pelican country. they could not be located in the usual places. Winters (except 1964-65) were not severe during the study period, and mixed herd groups were not observed at Mud Volcano nor in Pocket Basin. The areas were not preferred by the herd 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 the margin for sur- vival of the herd groups in Fire- hole, Hayden, and Pelican valleys during the most extreme winter conditions. Effects on Habitat Effects on habitat as observed throughout the study period were considered from two points of view: those which seemed to occur even under low population densi- ties of bison, and those which might have resulted from an eco- logical imbalance and overpopula- tion by bison. Bison caused or con- tributed to five kinds of impact on their habitat: debarking of trees, formation and maintenance of trails and wallows, trampling of sinter rock deposits in areas of thermal activity, and alteration of plant cover. Trees which were debarked and even girdled by the rubbing and horning of bison in summer were not scattered throughout the bison use areas, but occurred in certain localities, apparently favored by both the mixed herds and the scat- tered bulls. In extensive areas of lodgepole 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 oc- curred during the period of shed- ding and regrowth of hair, when biting insects were sometimes numerous, and extended on through the rut. Horning of trees by bulls, more specifically associat- ed with rutting activity, had even more effect than rubbing (Fig. 48). Although many trees survived years of this use, isolated trees and those near the edges of the forest were often killed. McHugh (1958) found that in rare cases in Hayden Valley the tree line was actually forced back, but that overall effects on reproduction were minor. Pat- ten (1963) concluded that elk con- tributed to maintenance of an abrupt ecotone between forest and meadows in the Madison Range (just west of the park) but that for- est areas were increasing slowly. Similarly, the bison might impede, but not stop, the invasion of the meadow areas by the forest, which appears to be occurring. Wallows, particularly those lo- cated 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 the bison themselves (Fig. 49). Even after areas such as Blacktrail Deer Creek were unin- habited by bison for a number of years, the depressions left by the Habitat Relationships 105 Fig. 48. Bison horning effects on a lod- gepole pine. wallows could still be discerned, although no differences between the vegetation within and around the depressions were apparent. When situated on slopes, wallows sometimes formed focal points of erosion, particularly in the shallow sandy soils of the hills in the south- west part of Hayden Valley. The presence and continued use of such sites did not appear to be re- lated 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 all seasons on some of these sites, which suggested that as long as any bison inhabited Hayden Valley these favored places re- ceived 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 those connecting 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 used historically, as now, because of habits and distribution patterns. Areas of thermal activity used by bison, where hot pools and geysers are located, sometimes show breakage of sinter deposits by trampling. Because the rock de- posits form slowly, the effects may be apparent for years. Mixed herd groups used such areas infre- quently and for brief periods, ac- cording to the severity of winter- ing conditions, as discussed pre- viously. Some wintering bulls used certain thermal areas throughout the winter every year regardless of changes in bison numbers. Locations where debarked trees, wallows, trails, and trampling of thermal areas were most noticea- 106 Bison of Yellowstone National Park Fig. 49. Bull bison at a wallow which is used year after year. ble were in the Firehole-Hayden Valley part of the park. Before the present study, during the much higher bison populations of the mid-1950s, these effects caused considerable concern. The impact of the presence of bison was ob- vious, and may have seemed espe- cially striking because bison (ex- cept perhaps a few strays) had been absent from that area for at least 35 years and had not been present in any numbers for at least 50 years. Then, over a span of about 15 years, the marks of bison habitation became suddenly ap- parent, and increased rapidly as the population expanded into this uninhabited section. The resulting concern was understandable, but perhaps exaggerated. Observations made during the study period indicated that de- barked trees, wallows, trails, and trampled thermal areas were all effects which occurred at locations favored by bison for specific activi- ties. The amount and distribution of such effects might increase somewhat at higher population levels, but not to the same extent as the numerical increase. An as- sessment 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 condi- tions. Observations indicated that effects on summer range from use by the wide-ranging bison ap- peared less important than influ- ences from climatic factors (late- melting snow patches, late springs, short growing seasons) and edaph- ic influences (slope, soil, expo- sure). During the present study, evalu- Habitat Relationships 107 Fig. 50. A bison trail, one in a network connecting the most-used parts of the Hayden Valley area. ations made of range conditions in Lamar, Pelican, and Hayden val- leys by the Soil Conservation Serv- ice (1963, 1964) indicated large areas of upland (usually steeper slopes and southwest exposures) in the poor and fair condition classes, producing less than 25% and 26- 50%, respectively, of potential or climax vegetation. Soil erosion and disturbance (particularly in Peli- can 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 excel- lent condition. The condition of these wintering valleys was attrib- uted 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 condi- tions prevailed. The effects which bison had on the vegetative cover of the winter ranges they inhabited, as the above surveys showed, were mostly con- fined to upland sagebrush-bunch- grass sites. Both the surveys and the present study indicated that the sedge-producing wet bottom- lands and swales showed little ef- fect. 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 suggest- ed that these sites were particular- ly vulnerable to impact and might 108 Bison of Yellowstone National Park remain in such condition in spite of varying patterns of use. Cole (1969) suggested that free-ranging elk would maintain upland areas in similar condition, which he termed biotic disclimaxes. Information on the quantity and composition of the forage re- sources of the thermal sites used by mixed herd groups under ex- treme winter conditions has not been obtained. Use of these areas in stress circumstances (which oc- curred infrequently) rather than by preference suggests that al- though the forage resources ap- pear 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 win- ter 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 win- tering valleys (except Lamar) has been little altered by the activities of man, although animal numbers and distributions have been changed. 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 num- bers, and those for much of the park's history, have been less than the original populations which apparently centered on the var- ious winter ranges. Pelican Valley may indicate the extent to which present conditions represent the past. A bison popu- lation has wintered there annually since the park was established (and probably long before), it has been least disturbed by man (reduc- tions), and historical sources pro- vide 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 bur- rowed up the ground to such an ex- tent that it is traveled over with diffi- culty . 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 those which 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 Con- servation Service 1964) attributed retrogressive changes in plant cover on upland sites primarily to the effects of bison use. The ab- sence of many bison for nearly 50 years apparently permitted a trend toward climax vegetation; subsequent repopulation caused marked retrogression which may represent reestablishment of con- Habitat Relationships 109 ditions which were prevalent with use by the original bison popula- tion. Conditions resulting from use by bison in the Firehole may be comparable. In Lamar, present effects of bi- son use probably represent more of a departure from early condi- tions. Habitat disturbance by man has been greater, bison popula- tions were maintained in semido- mestication for many years, and the area provides winter range for a more diversified ungulate popu- lation (elk; bighorn, Ovis canaden- sis; moose). The extent to which bison use and resulting effects may overlap with that of other ungu- lates on this range is presently being studied (William Barmore 1969 pers. comm.). Present low bison numbers contribute minimal effects on vegetative cover com- pared with other influences, and have much less impact than in his- toric times. 9 Suggested Mechanisms of Population Regulation Bison 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 envi- ronmental and populational mechanisms. Regulation, to a vary- ing degree, has been imposed by man since near-extermination of the original bison. Limited knowl- edge of original bison population characteristics, habits, and distri- bution, together with application of ranching methods to the plains bison introduced in 1902, has in- fluenced subsequent management practices. After 1952, all vestiges of artificial management, except reductions to control population numbers, were eliminated. Reduc- tions were continued at irregular intervals to compensate for the alterations in natural conditions which were the accepted result of the establishment and use of the park, and settlement of the sur- rounding country. Information from the present study indicates that compensatory reductions are not necessary on all population segments; the need for future reductions on any popula- tion segment is less clear. Figure 51, which shows the known Pelican Valley wintering bison population from 1902 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-extermi- nation before 1902, the popula- tion increased gradually for nearly 20 years. Counts as shown are probably somewhat low, but suggest that a fairly stable popula- tion existed for another decade. A general slow upward trend is evi- dent from the early 1930s to the early 1950s, but the population remained near or below 300 ani- mals 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 inad- equately explained by either re- ductions or group shifts. 110 Population Regulation 1 1 1 /900 /905 /9/0 /9/5 /920 /92S /930 /Qjf 500 /935 '940 /945 /950 /9S5 /960 /96S /970 re** 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 Popula- tion Trends) in spite of the occa- sional temporary group shifts. Predation and disease, previously discussed, have been only minor influences. Environmentally influ- enced factors of low reproduction rates compared with those of other bison herds, low increment rates in spite of some increase in new-calf percentages following recent re- ductions, and heavy mortality dur- ing exceptionally severe winters appeared most important in Yel- lowstone as a whole. Presumably, the same factors apply to Pelican as a subunit. Environmental effects, particu- larly the combination of low tem- perature conditions and snow depths sufficient to require consid- erable efforts for survival, were not measured and were difficult 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 with the decreased rates among yearlings and 2-year-olds, suggest- ed that calves, perhaps because of closer association with the cows, were not as stressed by environ- mental 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) ob- served a dominance hierarchy based on sex and age. He noted that calves derived dominance from their cows, and that domi- nance was displayed in feeding situations and deep-snow travel. The stress on subordinate animals, as well as aged or otherwise weak- ened adults, would increase with increasingly severe weather re- gardless of forage availability for 1 1 2 Bison of Yellowstone National Park Population Regulation 1 1 3 the entire population. The rela- tionship between numbers of ani- mals, available forage, and mortal- ity did not appear to be direct; forage quantity, although affected by snow depth and distribution, exerted effects in combination with the physical stress imposed by snow depth and storm conditions at low temperatures. Figure 51 also shows a level be- low which the Pelican population has not dropped since the recov- ery (about 1935) from the low of 1902. Although only 88 were counted in 1957, no attempt was made to locate all animals (Jim Stradley 1968 pers. comm.). Thus, approximately 100 animals may represent the maximum popula- tion which could survive the most severe winter, but perhaps a figure of 100-200 bison better represents a level around which this popula- tion 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 environ- ment which does not occur else- where. The survival factor for bison in parts of Yellowstone may be the existence of thermal areas. As pre- viously 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 the study period — may determine the lower limits to which the population numbers drop. A comparison of the larger Yel- lowstone valleys (Table 18) gives further evidence on which factors make habitation by bison possible. In addition to the previously dis- cussed wintering valleys, there are other large valleys in Yellowstone where bison herd groups appar- ently were never known, histori- cally or more recently. Extensive sedge bottoms are a feature of the valleys used by bison; additionally, where winter conditions are con- sistently less severe, as in Lamar, there are extensive open side hills of sagebrush-grassland which al- low 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 is possible. Some streams which remain unfrozen because of an influx of warm water are an addi- tional feature of most wintering areas, as are some river benches or valley side slopes and small hills (sagebrush-bunchgrass up- land 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. 114 Appendix I COMMON AND SCIENTIFIC NAMES OF PLANTS Common name Scientific name Alpine Foxtail Alopecurus alpinus Alpine Fir Abies lasiocarpa Arnica Arnica spp. Balsamroot Balsamorrhiza sagittata Barley, Meadow Hordeum brachyantherium Barley, Wild Hordeum spp. Blue-eyed Mary Collinsia parviflora Bluegrass Poa spp. Bluegrass, Alpine P. alpina Bluegrass, Canby P. canbyi Bluegrass, Cusick P. cusickii Bluegrass, Kentucky P. pratensis Bluegrass, Sandberg P. secunda Bluegrass, Timberline P. rupicola Cinquefoil Potentilla spp. Cinquefoil, Northwest P. gracilis Cinquefoil, Shrubby P. fruticosa Clover Trifolium repens Dandelion Taraxacum spp. Dwarf Huckleberry Vaccinium scoparium Engelmann Spruce Picea engelmanni Eriogonum Eriogonum spp. Eriogonum, Sulfur E. umbellatum Geranium Giant Wild-rye Elymus cinereus Groundsel Senecio spp. Horsetail Equisetum spp. Idaho Fescue Festuca idahoensis Junegrass Koeleria cristata Lupine Lupinus spp. Mountain Brome Bromus marginatus Needle-and-Thread Stipa comata Needlegrass Stipa spp. Needlegrass, Columbia S. columbiana Needlegrass, Richardson S. richardsonii Onion Allium rubrum Phlox Phlox spp. Pine, Lodgepole Pinus contorta Pine, Whitebark P. albicaulis Pinegrass Calamagrostis rubcscens Purple Onion Grass Melica spectabilis Pussytoes Antennaria par vi folia Raspberry Rubus spp. Common and Scientific Names of Plants Common name Scientific name Red Dogwood Cornus stolonifera Kusn Juncus spp. Rush, Long-styled J. longistylus I\ Ll j 1 1 , JIC11UC1 J fpnuK Rush Wire J. balticus Sagebrush Artemisia spp. . l. Ll JU I- 1 1 La La Sagebrush, Fringed A. frigid a Sedge Carex spp. aC. acuta L>. aUCl la C. aquatilis C. athrostachya C. nova C. platylepsis C. raynoldsii C. xerantica Sedge, Beaked C. rostrata Sedge, Hepburn C. hepburnii Sedge, Nebraska C. nebraskensis Sf»H crp Oval riparl V ' . l(,i7LiVLJla Sedge, Silvertop C. foenea Sedge, Smallwing V ' . M/H i UUILJ CI Sedge, Valley r am\~vjla crp AA/r»nllv V > . tall UizliiLJja jci vii^cucri l y f\lllClalH~lllCl Mjn. Snikf -spH of J .in'l l/dl Jj HUH 1 Ujlatilrfl 1 lit l v /l_ 1 1 1 v iyt_iC/I aLa Timber Oatgrass Danthonia intermedia 1 HHUIII y illlCLllll Ul alCllbC Timothy, Alpine P. alpinum TiiftfH Haircrrass X UlltU 1 1 CI 1 1 tZl ajj i-^CTjCl JcaiJl LMoia \~aCjLJlL\Jja Wpsrprn RiilrnsVi IttJlV-l 11 U Ull UJU virniK ^/"iifiic k7L 11 L/tUj aLUlUJ vv 1 1^ el I til a j j Agropyron spp. Whpatcrrass Rlupbunch A. spicatum Wheatgrass, Bluestem A. smithii Wheatgrass, Slender A. trachycaulum Wheatgrass, Thickspike A. dasystachyum Willow Salix spp aNot listed in Booth (1950), but determined by him (1968 pers. comm.) 521-650 O • 73 - 9 116 Appendix II SUMMARY OF BISON REPORTS PRIOR TO 1903, YELLOWSTONE NATIONAL PARK AND VICINITY Source Date Report Raynolds (1867) DeLacy (1876) Haines (1968 pers. comm.) Potter (1962) 25 June 1860 7 Sept. 1863 1860s 1867 crossed Low Pass from Henry's Lake to the Madison (west of Yellowstone National Park) "We have seen one band of buffalo among the hills, ..." eastern side of Shoshone Lake "through scrubby pines, without underbrush. There were many game trails made by the wood buffalo, whose tracks appeared numerous and fresh. We did not see any ... " quotes local newspapers of the period as saying there was a herd of bison in the Snowy's (north of park, part of Absarokas). 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 (Firehole area) "in one spring we saw the entire skeleton of a buffalo . . . " Henderson (1870) 21 June 1870 27 June 1870 2 July 1870 17 July 1870 22 July 1870 24July 1870 Buffalo Plateau (north edge of park) "thousands of buffalo quietly grazing." upper Buffalo Creek (north edge of park) "All game plenty— buffalo, ..." Lake Abundance (just beyond northeast corner of park) "Thousands of bear, elk, buffalo, and deer." N. Fork of Clark's Fork (Broadwater River, east of northeast corner of park) "several beautiful parks, full of buffalo,... Cache Creek (Lamar area) "thro buffalo, elk & bear ... all very tame." Specimen Ridge (north edge Mirror Plateau) "Buffalo ..." Bison Reports Prior to 1 903 117 Source Date Report Doane (1875) Barlow and Heap (1872) 8 August 1870 9 August 1870 18 Sept. 1870 2 August 1871 summit between Buffalo Cr. and Hell- roaring (north edge of park) "Saw several buffalo." head of Middle Boulder River (north of Park) "Thousands of buffalo, ..." Old Faithful (Firehole area) "numerous fresh signs of buffalo ..." Lower Geyser Basin (Firehole area) "Across the plain to the west . . . mud springs in ravine . . . tracks of deer, elk and buffalo ..." Blackmore (1872) 1872 Lamar "B.H. informs me that this valley is a favorite resort of the mountain buffalo or bison. The hills on the left were the 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 in bands of from 5-30 rarely more altho he has seen 50 ... " LeHardy (1873) Jones (1875) Dunraven (1876) 1873 (about mid-August) 1873 1874 Grinnell (1876) Supt. Annual Report (1877) 1875 1875 "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 a number of Buffalo." found bison bones embedded in soil at the bottom of a cave at Mammoth general locale of Yellowstone National Park. "On the little prairies, open glades, and sparsely wooded slopes, grazes the small mountain bison or buffalo, whose race has also nearly vanished from the scene; ..." "The so-called 'Mountain Buffalo' was abundant in the Yellowstone Park." "scores if not hundreds of moose and bison were taken out of the park in the spring of 1875, ..." 1 1 8 Bison of Yellowstone National Park Source Date Report 1877 refers to the triangle of land with the East Fork (Lamar) as the base, extend- ing south 50 miles to the head of Yellow- stone Lake (Mirror Plateau, Pelican) "Here is still a herd of three or four hundred of the curly, nearly black bison or mountain buffalo." Holmes (1878) 1878 Twin Buttes (Firehole area) "there are some upland parks in which there are buffalo signs (the Mountain Bison)." Raymond (1880) Supt. Annual Report (1880) 1880? 1880 "whitened skeleton of a mountain buffalo ..." (in a hot pool — Firehole area) "Bison or Mountain Buffalo" "Bison, so called, in the Park, 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 of Colorado. They have also smaller shoulder humps, and larger, darker brisket wattles. They differ materially from the buffalo of the Great Plains, being more hardy, fleet, and in- telligent; their hides also are more valua- ble for robes, as they are darker, finer, and more curly; and these animals are, in all probability, a cross between the two varieties just mentioned. "There are about three distinct or separate herds of bison within or adjacent to the Park. [north edge of parkj "The first, numbering about two hundred, pasture in summer in the valleys of the Crevice, Hellroaring, and Slough Creeks, and the mountain spurs between them, descending, with the increasing snows, to winter in the deep, sheltered grassy valleys of the East Fork [LamarJ 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 hun- dred, summer in the elevated and abruptly Bison Reports Prior to 1903 1 19 Source Date Report broken, little-known section of the Park, extending from the Hoodoo region to the Grand Carion, and from Amethyst Moun- tain to Pelican Creek, near the foot of the Yellowstone Lake, and winter oc- casionally upon the East Fork [Lamar] of the Yellowstone and on Pelican Creek. Their other winter haunts 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 probable they are on the Pacific side of the Continental Divide, and, if so, they are not permanent occu- pants of the Park, and are therefore likely to be slaughtered by advancing settlers. "most keen of scent and difficult of ap- proach of all mountain animals." "Here I purpose wintering [junction Soda Butte Cr.-Lamar River] so as to protect the game, especially elk and bison, in their sheltered chosen winter haunts, from the Clark's Fork and other miners." Yount 1881 [north edge of park] (1881) "The Slough Creek and Hellroaring bands of bison did not venture near the cabin until February, nor did those of Amethyst Mountain at all; ... I found . . . that a small band of bison wintered on Alum Creek [Hay den Valley] and another on the South Fork [Firehole River] of the Madison River; ..." Supt. Annual 1881 Mary Mountain area "It also greatly ex- Report (1881) tended our knowledge of the fire holes in those regions, and afforded proof positive that a band of bison wintered there, at an elevation of nearly 9,000 feet." Yount 1880 (1880) 120 Bison of Yellowstone National Park Source Date Report Bozeman Avant-Courier (1883) 11 Jan. 1883 22 Feb. 1883 Pierrepont (1884) 11 Sept. 1884 "at least one band of bison, containing four hundred ..." There is a reference to the employment of hunters and meat 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 . . . deep snow . . . brought out a fine lot of buffalo meat . . . hunters and meat contractors were ordered in . . . in hot water." toward Lake Abundance from Slough Creek (north edge of park) "Five miles to the eastward they ran upon a herd of buffalos numbering about a hundred and eighty, out of which they killed seven . . . " Hague (1893) Livingston Enterprise (1885) 1884 winter 1884-85 March 7 12 Dec. 1885 19 Dec. 1885 "In 1884 I estimated the buffalo in the Park at 200; ..." "the herd of bison or mountain buffalo that has long inhabited the Yellowstone Mountain slopes and valleys was seen to number two or three hundred in the Park this winter." 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 have heard that twenty head were killed in Yellow- stone Park by a party of English tourists." 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 driven out of the park by use of explosives, and killed. Bison Reports Prior to 1 903 121 Source Date Report Supt. Annual Report (1885) 1885 "The game in the Park had been shot with impunity and marketed at the hotels ... I succeeded in a measure in breaking up the wholesale slaughter .... There is some- where in the neighborhood of two hun- dred bison in the Park, ..." Supt. Annual Report (1886) 1886 "stopped the wholesale slaughter of game ..." "From the reports . . . abundance of game [including buffalo] ..." Supt. Annual Report (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 ex- ceed one hundred in 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 the mountains, outside the Park limits, and in the winter lower down on small tributaries of the Yellow- stone, 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 fifty-four 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 is much scattered. A band of nine or ten from this herd was seen several times this spring in the vicinity of the Upper Geyser Basin. ... It is practically certain that none have been killed within the Park limits during the past two years, ..." 1 22 Bison of Yellowstone National Park Source Date Report Supt. Annual Report (1888) 1888 "During the early . . . winter . . . desira- ble ... to secure some accurate informa- tion concerning the winter haunts of the buffalo .... "The herd of buffalo which had passed a portion of the previous winter along Specimen Ridge was not encountered, and the only buffalo encountered on the trip were three in Hayden Valley. . . . Early in April ... a band of 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 the waters of the Madison and Yellowstone Rivers and in the adjacent valleys. Numbers of these animals have been seen during the spring along the Fire Hole River and its tribu- taries, and extended investigations have shown that they 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 of these 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 progress .... "During the past two years, . . . but little game has been killed .... "Hunters, stimulated by the high prices offered by taxidermists for specimens, are now lying in wait beyond the borders of the Park ready to pounce upon any un- fortunate animal [ref. to bison] which may stray beyond its limits." Bison Reports Prior to 1903 123 Source Date Supt. Annual March 1889 Report (1889) Report "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 the buffalo. These basins, . . . well-nigh un- approachable, except when the ground is frozen and covered with deep snow, . . . successful in locating the buffalo in their haunts of the previous winter near the hot-spring basins on the divide between the waters of the Yellowstone and Madi- son Rivers. Although no buffalo were seen east of the Yellowstone, it was evi- dent from the abundant signs that they habitually frequented the hot-spring basins in this locality, some of the signs being quite fresh." Supt. Annual Report (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. Annual Report (1891) 1891 "Poachers" "So long as there is no law within the Park for the prevention of hunting and trap- ping, it will be a most difficult matter to break them up. "I am satisfied that both hunting and trap- ping are carried on . . . 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." 124 Bison of Yellowstone National Park Source Date Report May 1891 "I have abundant evidence, however, that the buffalo ... are on the increase. Some tourists who went through the Park in May saw a herd of about 30, with several small calves, near the Trout Creek lunch station." July 1891 "In July I sent Wilson out to . . . the west line . . . found two small bands of about 30 each, one with 12 or 15 calves; in addition he saw several single ones and small bunches. I do not think it is exag- geration to say there are 200, and prob- ably there are 400, within the Park, and that they are thriving and increasing." "the grazing-ground in Hayden Valley was visited by a snowshoe party, who counted the scattered bands, . . . groups were generally small, and each contained a goodly number of calves. They num- bered by actual count nearly 300, but there is no means of knowing what propor- tion of the Park buffalo were then gathered here." "I was informed that one Pendleton, a butcher and poacher from Cooke City, had captured two buffalo calves on speci- men range, and had taken them across the north end of the Park, . . . "there are certainly not less than four hundred here; of these about 20 percent were calves last year. This year, also, the calves seem numerous and prosperous. The great value placed upon them by sportsmen and taxidermists makes their protection difficult, ..." Hague winter 1891-92 (1893) Supt. Annual 1892 Report (1892) Bison Reports Prior to 1 903 1 25 Source Date Report 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 the head of mountain buffalo, and even in this elevated region they live for the greater part of the year in the timber. . . . their habits are quite different from . . . the buffalo of the plain, and it is most unusual, save in midwinter, to find them in open valley or on the treeless mountain slope. They haunt the most in- accessible and out-of-the-way places, . . . living in open glades and pastures, the oases of the dense forest, often only to be reached by climbing over a tangle of fallen timber .... 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 in such unfrequented country as the southern end of the Madison plateau, the Mirror plateau, and the head of Pelican Creek, and on the borders of that elevated tableland known as Elephant Back. In winter, leaving the forest, they feed over the slopes of Specimen Ridge, and in the open Hayden Valley. "It is not likely that there ever were many buffalo in the Park, ... If they ever roamed over this country in large herds, evidence of the fact should be apparent by well-trodden buffalo trails, which no- where form a feature of the Park plateau. . . . They occasionally wander beyond the Park Borders into Idaho and Montana with the first fall of snow, returning to their mountain homes with the approach of spring." 126 Bison of Yellowstone National Park Source Date Report Supt. Annual Report (1893) 1893 "As the game diminishes in the adjacent States, professional hunters and trappers become more bold and more active. Montana, Idaho, and Wyoming all have stringent 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. . . . Confiscation of 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 more shared that fate. The heads of these were mounted .... "The buffalo have been seen often during the year, and they appear to be doing well. In all the herds a fair proportion of calves is found. Those killed have been mostly 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 River- side 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 hun- dred placed on their number last year is surely not too high." Hough (1894) spring 1894 "We counted 75 to 85 head of buffalo in Hay den this trip. . . . 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 and another 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 1 1 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 other Bison Reports Prior to 1903 127 Source Date Report heads were offered to a Bozeman taxi- dermist; 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 and winter, 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 Moun- tain and this sheltered little valley. They have not wintered on the west side of the divide in any numbers for a considera- ble time. "wild wall of mountains which we saw to the north of the Yellowstone— so desolate and forbidding that even now .... 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." Supt. Annual 1894 "not able to report any diminution of Report (1894) poaching ..." (describes Howell poach- ing case, with Howell caught killing 5 bison in Pelican, and his cache of 6 addi- tional heads). "The dead bodies of 1 3 bison have been discovered in their winter range. . . . con- vinced they perished from natural causes.' "Buffalo have been more carefully watched and more accurately counted than ever before. After deducting the losses from all causes, I feel disposed to reduce my estimate ... to 200, ... A few were seen in their winter range 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 un- doubtedly heavy that year, neither the losses nor the population figure afterwards were stated as fact by any of the recorders of the time. 128 Bison of Yellowstone National Park Source Date Report Marble no date mentions Dick Rock (of Henry's Lake, (1932) west of the park) catching 5 calves. Murri no date reference to Dick Rock getting his buffalo (1968) calves in the Bechler Meadows in early spring, known to have gotten a pair. Hofer approx. "Hunters from the West Side were getting (1927) 1894 or 1895 calves in the early 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). "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 wild bison now existing in the United States is on the border of this State, . . . inquiry into various rumors of the killing of bison, either in the Park near the Idaho line or across it . . . convinced me that this last remaining herd is in danger of extinction by these people. ... I have good evidence of the killing of at least ten less than two years ago . . . prior to the passage of the protection act, ... I have undoubted evi- dence of the capture of three calves this spring by a resident of Henry's Lake. . . . There are rumors of a herd of nearly one hundred having been seen in Idaho outside the Park within the last two or three months. [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 of from three to four to ten were seen in widely separated localities Supt. Annual 1895 Report (1895) Bison Reports Prior to 1 903 1 29 Source Date Report 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 fear that their number has not increased, . . . esti- mate . . . two hundred still remain." Supt. Annual Report (1896) 1896 "I . . . organized three parties for opera- tions against the merciless freebooters of the Henry's Lake country. . . . The ground covered by the buffalo in their summer range was most thoroughly gone over. Carcasses, ... of about ten buffa- loes 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 Hay den Valley as usual, and on the extensive scouts made by my order during the winter months only about a dozen in all were seen. They were scat- tered singly and in small bunches over a large portion of the Park. Within the last month [July] one party reported a small bunch of 3 in one place, and of 1 2 in another. A second party reported a bunch of 3 in a valley in a distant part of the park, and tracks of a herd of 8 or 9 more, but this herd was not seen. From reports received, I feel confident that the majority wintered in the extreme south- west corner of park, in the Falls River [Bechler] meadows; and I also feel sure that there are now a considerable number east of the Yellowstone River. . . . fair certainty of the existence of 25 or 30, and possibly of 50." Snake River Monthly report 21 Aug. 1897 "By way of Summit Lake. Saw sign of about 20 buffalo ..." (Madison Plateau) Whittaker (1897-99) 14 Nov. 1897 18 Nov. 1897 sign of 5, Mary Mountain area (Hay den Valley) sign of 2, Astringent Creek (Pelican Valley) 1 30 Bison of Yellowstone National Park Source Date Report Supt. Annual Report (1897) 1897 "game, buffalo excepted, is increasing. "The number of buffalo is estimated at 24. "the buffalo remaining in the park are now scattered in very small herds at a number of points far remote from each 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 the summer, and now the few remaining buffalo are scattered and range in the most remote and inaccessible parts of the park in summer. I am confi- dent of finding 25 this winter, 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 sta- tions recognizes known buffalo haunts as: Mirror and Lamar, Hayden Valley, and the Firehole area. Soda Butte Station Record 19 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 the spring and on both sides of Sour Cr. after followed them down Sour Cr. to where a hot creek came down from a hot mountain on the north which they went up, and a close examination of the trail . . . [the trail was not made in single file but band was spread out] I estimate the band as follows 4 calfs, 8 bulls, about 8 to 9 cows, but think some of the signs which I took for cow signs may have been 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 Bison Reports Prior to 1 903 131 Source Date Report 11 April 1898 Lake 21 June 1898 Station Record Morrison July 1898 (1897-98) 7 July 1898 8 July 1898 Lake 27 July 1898 Station Record 14 Aug. 1898 Morrison 12 Sept. 1898 (1897-98) 13 Sept. 1898 to speak of on the flat which is about a mile long and 3/4 wide and is covered with hot springs and hot creeks ..." sign, estimate of 3, 4 miles north of the Upper Basin, Firehole area old sign— hot formations on Mary Mt. "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." "left . . . head of Pelican Cr went down it 5 miles made camp . . . 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 ... to camp. Saw one buffalo jumped 5 buffalo near ford of Broad Cr followed them to Fern Lake where we saw the one was on one of the heads of Sour Cr. an old bull. Around Ponuntpa Springs there were fresh signs of the band I saw there last winter." 5-6 buffalo wintered near forks of Pelican Cr., fresh signs one bull buffalo on top of Mary Mt. 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 signs 1 bull 6 mi from W boundary West Boundary headed for Summit Lake "3 m. east of bound, near a little spring saw where 5 buffalo had bedded over night, probably 2 bull a yearling and 2 cows." 521-650 O - 73 - 10 132 Bison of Yellowstone National Park Source Date Report Whittaker (1897-99) Morrison (1897-98) 30 Sept. 1898 10 Oct. 1898 a trip was made up the Lamar to Cold Cr. and Mist Cr., over the divide to the head of Willow Cr. (Mirror Plateau area) and down Raven Cr., up to Pelican, to Broad Cr. and return to Pelican "will make spe- cial report on buffalo" 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 Burgess (1898-99) 18 Oct. 1898 19 Oct. 1898 20 Oct. 1898 10 Nov. 1898 13 Nov. 1898 23 Nov. 1898 refers to Mirror Plateau area "but after riding around the entire summer range i could not find any sign of them met Scout Morrison . . . presume they have all left their summer range on Flint and moved to either the head of Pelican Creek or Willow Creek where i saw some sign of them on my last trip . . ." (see date of 30 September 1898) Bechler area one, track "went to [Bechler] River saw 2 year old buffalo tracks . . ." "tracks of about 6 B They had been made 6 or 7 days ago." Firehold to Fountain "saw the Buffalos had been going along the river to the L[one] Star Geyser." Trout Cr. to head of Nez Perce Cr. "I found two Buffalo tracks one Bull and cow" "Then to East Fork of Pellican, where I saw the tracks of one buffalo." east side of Hayden Valley "Went East to Forest Springs, found old signs of Buff alios ... to worm formation at head of Moss Creek, found some fresh Buffallo tracks going South . . . and down in sour creek where there ii quite an opening there I found where 4 Buffalos had beded the night before, from there I went to . . . Cotton grass and Sour Creek I saw 2 old Bulls one laying down they were very wild, and ran back toward sour creek." Bison Reports Prior to 1 903 133 Source Date Report Supt. Annual Report (1898) Burgess (1898-99) 1898 Whittaker (1897-99) 10 Jan. 1899 11 Jan. 1899 6 March 1899 9 April 1899 10 April 1899 14 April 1899 15 April 1899 12 May 1899 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 of this herd from the evils of inbreeding . . ." refers to Mirror Plateau area "up East forks of Estringent [Astringent Creek] to Head of 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 to Fern Lake. Saw 3 Buffaloes on the northwest End of Lake." "went up middle Estringent, over White Lake to head of Sour 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 Hay den Valley. "... 2 Buffalo . . . wintering on snake river." "went to Estringent Cabin" "I looked for the Buffalos. saw 20" "went to Trout Creek one buffalo on Crater Hill" "went to Fountain 5 Buffalos on Central Plateau" "saw one Buffalo near the Base of Hell-Roaring Mountain about a 4 year old . . ." Lake Station Record Whittaker (1897-99) 1 June 1899 15 Aug. 1899 buffalo sign at Mary Mt. "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 . . ." 1 34 Bison of Yellowstone National Park Source Date Report Holt (1899-1901) 23 Sept. 1899 8 Oct. 1899 26 Nov. 1899 Supt. Annual Report 1899 (1899) Supt. Annual Report (1900) 1900 Snake River to Lake "fresh signs of two buffalo . . .*' "Buffalo passed within sight of camp . . ." (Thorofare area) Ponuntpa area, Mirror Plateau "no fresh signs of Buffalo, found skeleton of calf." "it is not known how many there are left or whether or not they are in- creasing. I shall try and find out this winter as to 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." "Twenty-nine head of buffalo were counted by scouts last winter, and there were possibly 10 more in the park that were not seen. Unless stations are located near the two southern 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 pre- served and will increase." Supt. Annual Report (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 pos- sibly 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 park." (One bull was killed in Jackson Hole.) Lake Station Record 8 Dec 1902 patrolled to Pelican Country, 1 buffalo Bison Reports Prior to 1 903 135 Source Date Supt. Annual 1902 Report (1902) Report "In addition to the large corral that has been constructed near the Mam- moth Hot Springs, a small corral . . . on Pelican ... to capture therein the few remaining buffalo . . . During the past winter ... 22 of these animals on the head of Pelican Creek, and there are probably a few more that we were un- able to find. This herd is exceedingly wild, and will probably never increase in size, and may possibly die out com- pletely. It is thought that we can catch 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. . . ." 136 Appendix III REPORTS OF WILD BISON 1903-19, YELLOWSTONE NATIONAL PARK. Source Date Report Lake Station Record 19 Jan. 1903 15 Feb. 1903 26 Feb. 1903 24 Mar. 1903 25 Mar. 1903 12 May 1903 returned from Pelican 15 buffalo Pelican country 1 buffalo (main valley) from Pelican 1 9 buffalo from Pelican seen 1 7 buffalo Pelican 19 buffalo "from Pelican Country . . . Had 2 Buffalo bull calves on toboggan drawn by dogs. Saw 16 old buffalo and 3 calves." Supt. Annual Report (1903) Lake Station Record spring 1903 4 April 1904 end April 2 calves captured from wild herd located one buffalo at the hay stack (Pelican) Scouts— Pelican Valley— "seeing 1 1 Buffalo 5 cows and 6 bulls no calves saw 6 dead ones" Superintendent's Journal, 1903-21 6 May 1904 Supt. Annual Report (1904) Supt. Annual Report (1905) 18 May 1904 spring 1904 1905 party that went out for buffalo calves re- port finding as follows ... 1 1 live buffalo 5 dead buffalo— 4 old ones and 1 yearling (additional report of one old bull dead between Lake and Thumb refers to one of the three Goodnight bulls which was turned out) party returns, having captured one female calf on the head of Sour Creek; they saw twelve live buffalo; men at Canyon station saw two in Hayden Valley remnant located on the head of Pelican Creek, "three calves have been caught up from the wild herd . . . Two of these are males and one is a female." (the two males were those caught the previous year) "now about 30 of these animals left, ... on the head of Pelican Creek." Supt. Annual probably Report (1907) summer sign of 15, Mirror Plateau and Specimen Ridge; signs of 6, Madison Plateau. Wild Bison 1903-19 137 Source Date Report Scout Monthly Reports (1908) Supt. Annual Report (1908) Aug. 1907 I April 1908 13 April 1908 16 April 1908 13 July 1908 7 Sept. 1908 (approx.) 16 Sept. 1908 9 Oct. 1908 II Oct. 1908 1908 4 seen in Hayden Valley total estimated to be 25 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 calves sign 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 1 0 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) 1 1 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 later ones for the im- mediate 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 1 3. 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 remnant of the original wild herd is gradually in- creasing in numbers." 138 Bison of Yellowstone National Park Source Date Report Skinner and Alcorn (1942-51) 1908 used a figure of 32 counted. NOTE: On October 15, 1907, the Yellowstone Lake Boat Co. E. C. Waters corrals at Lake were 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 or five buffalo were rounded up at Lake to be driven to headquarters in early December of 1909. North of Canyon, with average snow depths of 4 feet, the buffalo broke away. When last reported they had gone down into the Yellowstone Canyon to feed, apparently in the vicinity of Seven Mile Hole, where survival would be unlikely. Probably any left near Lake disappeared one by one without ever mingling with the wild herd. There was no indication that 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 in corrals (Timmons 1962). Lake 15 & 16 Jan. 1909 patrol to Astringent Creek and White Station Record Lake, buffalo sign seen 23 March 1909 patrol to Astringent Creek cabin and White Lake, 3 buffalo seen sign at the Mushpot area on Pelican Creek 24 March 1909 Scout Monthly Reports (1909) 17 April 1909 15 April 1909 16 April 1909 4 buffalo near Yellowstone Lake, very thin (these may have been part of Boat Co. animals, 6 were driven across the Pelican Bridge in Nov. 1908) Astringent Creek to Mist Creek and Lamar and to Willow Creek cabin, saw 3 buffalo near cabin patrolled north to Soda Butte, saw 2 buffalo Supt. Annual Report (1909) April 1909 "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 1909 Reports (1909) "trying to corral 9 wild buffalo near Cache Cr. We captured 1 buffalo bull calf" Wild Bison 1903-19 139 Source Date Report Supt. Annual Reports (1909) Anonymous File No. 21 & 22, 5/28/09 Supt. Annual Report (1909) Lake Station Record Scout Monthly Reports (1910) Anonymous File No. 21 & 22, 3/2/10 Supt. Annual Report (1910) Lake Station Record May 1909 15 May 1909 July 1909 23 Dec. 1909 13 Jan. 1910 February 1910 23 Feb. 1910 1910 9 March 1910 16 March 1910 17 March 1910 30 June 1910 "A herd of 1 1 wild buffalo was seen on Cache Creek May 19, at which time a bull calf was caught ..." lists 10 at the mouth of Cache Creek-2 large bulls, 7 cows, 1 calf "Signs were also seen in the southwestern part of the park in July of this year." Buffalo signs seen at Squaw Lake (Pelican area), 23 buffalo seen near Pelican Springs buffalo signs 2 mi. west of Steamboat Sp. (Yellowstone Lake, north edge) Soda Butte to Cache Creek and return, saw 5 buffalo and signs of buffalo 29 buffalo seen on Pelican Creek (states group known not to contain the Boat Co. buffalo) "A herd of 29 wild buffalo was seen in Pelican Valley on 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 Boat Co.) (Pelican Valley) "seen 20 of them" from Park Point (Yellowstone Lake) to Pelican Creek, 6 buffalo from Astringent Cabin to Lake, 21 buffalo Lake Station to 14 mile post, Sylvan Pass Rd., saw 7 buffalo Lake Station Record 17 Feb. 1911 patrol to Pelican Cr., 20 buffalo Anonymous File No. 21 & 22, 3/14/11 Feb. ? part of wild herd sighted recently, sure of 20, think 25 including some calves 140 Bison of Yellowstone National Park Source Date Report Lake 2 March 1911 Station Record Scout Monthly 28-30 April 1911 Reports (1911) to Pelican Cabin, 25 buffalo from Signal Point (on Yellowstone Lake) north to Astringent Creek, saw 27 wild buffalo of which 2 were calves, traveled to Mist, Cold, and Willow Creek cabin N. to Lamar River, "sign of one wild buffalo' NOTE: During June 1911,4 bison were rounded up on the Madison and brought to Mam- moth, 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; plenty of old signs along Pelican Creek, at White Lake on the head of Sour Cr., and near the heads of Deep Creek. Thumb 10 August 1911 Station Record "patrolled to K. W. & De L. C. Reg. 82- 8 buffalo" (contrary to the Supt. Report, 1911, the 8 buffalo were probably seen at the Knotted Woods, southwest of Dryad Lake, rather than west of Thumb at DeLacy Creek) Supt. Annual Report (1911) 1911 "The wild herd has been seen several times, usually in the Pelican Creek Valley. The largest number seen at any one time was 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 July 1912 File No. 21 & 22 5/3/12 7/19/12 48 (inc. 10 calves) on Raven Creek "Scouts McBride and Little . . . report having actually seen and counted 48 animals. They are not together in a herd, but are considerably scattered, mostly on Pelican Creek, Upper Lamar River and tributaries." count included 10 this year's calves; one additional large bull on the Pitchstone for a total of 49 Wild Bison 1903-19 141 Source Date Report Scout Monthly Reports (1912) Nowlin (1912) 6 July 1912 7 July 1912 8 July 1912 9 July 1912 lOJuly 1912 11 July 1912 12July 1912 22July 1912 22-30 July 1912 Scout Monthly Reports (1912) 20 Sept. 1912 (approx.) 27 Sept. 1912 1 bull, signs of 1 more, Cache Cr. (may have been from tame herd) sign of a small band, between Cache and Willow Creek sign of 6, Willow Cr. (seen by another scout) fresh sign, vicinity of Mist Cr. 1 bull, signs of others, Mist Creek fresh sign, Mist to Raven Creek, (one seen by another scout) "patrolled county" (Mirror Plateau), saw 38: 25 cows, 3 bulls, 10 spring calves, one seen between Snake River and Aster Creek saw buffalo signs on Proposition Creek. trip made on Specimen Ridge and Mirror Plateau, upper Lamar 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 the headwaters of Clover Creek where they joined others, "all were feeding quietly in an open park." total of 35 : 7 bulls inc. 2 large ones, 1 3 cows, 7 yearlings, 8 young calves, fresh sign of two bulls on Timothy Creek total counted for trip: 39 "However, the summer range is so ex- tensive and difficult to traverse 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, they ought to gradually increase." 2 buffalo seen between Cold Creek and the Lamar R. 25 wild buffalo, vicinity of Saddle Mt. 142 Bison of Yellowstone National Park Source Date Report Supt. Annual Report (1912) 1912 Anonymous File No. 21 & 22 8/2/12 Scout Monthly Reports (1913) Lake Station Record Scout Monthly Reports (1913) Lake Station Record Scout Monthly Reports (1913) Supt. Annual Report (1913) winter 1912-13 28 Feb. 1913 March (early) 17 March 1913 April 30 May 1913 5 Sept. 1913 1913 "A special effort was made during the month of July to determine as nearly as possible the exact number of buffalo in the wild herd in the park. Forty-nine animals, including 10 this year's calves, were counted. . . . indicates that the herd is thriving beyond expectation." added note: "Men on Lake Station claim 53 winter 1912-13 but not officially reported." saw 35 wild buffalo, trip from Yellowstone Lake outlet to Pelican cabin 1 bull, head of Mist Creek 53 buffalo, patrol from Pelican cabin 1 bull, trip from Cache to Willow Creek on top of Miller Creek divide 2 buffalo, patrol to Cub Creek 20 buffalo, trip from Cold Creek to Frost Lake "No accurate count of the wild herd of buffalo was made, but scattering bands of them have been seen, and one party on patrol reports having seen 7 calves with a herd at a distance. It is believed that there has been some increase." Scout Monthly Reports (1914) Supt. Annual Report (1914) Stevenson (1915-16) September 1914 4 Dec. 1915 sign seen, vicinity of Saddle Mt. "No particular effort was made to make an accurate count . . . but they have been seen in considerable numbers on several occasions, . . . increasing slowly." "went up Pelican Creek and Raven Creek to count Buffalo. 4 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." Wild Bison 1903-19 143 Source Date Report Supt. Annual 1915 "has not been practicable to get an ac- Report (1915) curate count ... " 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. 144 O) « N >Q <£> O 1— ( l-H CM oo co CO T3 B V a a < 03 T-H 00 cm cm O -< CM o £ CO Bison Population 1902-68 145 CD to o o o CM m o m r» CD 00 00 cd to to CD CO 00 to CM O CD m CO -* m O cm m o CO CM o CM to 1— 1 CM 00 o 00 CD Tt< CM m oo o © o CO CO o m o » 00 CD CD O O o CD CD 00 to m in cd o CM CO m to 00 CD o CM CO m to 00 CD CM CM CM CM CM CM CM CM CM CM CO CO CO CO CO co CO CO CO CO 146 Bison of Yellowstone National Park CO CM 00 00 o CD 00 CO CO CM o CO CO CM CO 00 CM CM CM CM CM CM CM CO CM cd CM o t>- 00 CO o <£> <£> CO CD CM CD co 00 CD CD CD o cd CM o s 00 i—i CM CM 00 CO h h N CM CM CM d < < < o o CO CO o o m CO o CM 00 CD o ua o o <£> o CM lO 00 if> CM CO m m 00 vo CO p-H CM CM h CM CM Tt< CO CM 00 if) CM CM CM CO o o CD oo CM CM CM co CM CO CM CO CM CO CM O ~h O CM CM CO CM o 00 co o o CO CM t*» CM to CM CM CM CM 00 CM < CO <£> o co JP 00 »o CD CO If) o CO CO CO CM CM CM © CD Bison Population 1902-68 147 01 00 (M 00 ^0 co 0 0 O 0 CO <£> U CO m CO 00 lO 00 00 CM —1 CO CM °0 tJ< 00 o 0 "* 2 o © CM CM © 00 O CO CM S "2 3 o M f-H CM »? °^ « ^ c .2 o I" v u c < .S 6 ^ ■8* CM <-H l-H 00 *o o S £ f 1 -2 -S 00 o CO £ 3 -5 ™ U £ u 1 1 b i CM ■e *> § I) H C ^ m c 3 § y o < U £ o 09 3 ,336 521-650 0-73-U 148 Appendix VI 149 KNOWN BISON MOVEMENTS TO AND BEYOND YELLOWSTONE NATIONAL PARK BOUNDARIES 1942-67 West Boundary South Boundary Pop. No. Mary Mtn. 1942 Dec 1942-43 late winter 1943 Aug. Sept. 1947 fall 1948 late winter 1951 late Feb. March 1955 Feb. 1956 Mar. 1957 Feb. 1959 Feb. 1962 winter 1 963 winter 1 964 late winter summer fall 1965 Jan. 1966 Mar. May July 640 900 est. 550 est. 500 est. 400 est. 400 est. 400 est. Aug. 1967 late winter 200 est Often-summer Every year-summer NOTE: Refuge Manager Vivion, ago. Occasional west side reports No. out; location Pop. No. Mary Mtn. 100 No. out; location Pop. No. Lamar 742 742 1 ; 1 Vt mi. S of S. Gate 800 est. 3; vicinity S. Gate 500 313 380 est. North Boundary No. out; location A few; Gardiner 1 30; down Yell R., most only about 10 days and returned 150; near Lake Abundance 31; Elk Cr.-Hellroaring area 68; Gardiner-Jardine 6; near line, inside East Boundary Pop. No. L'mr-Pln. No out; location 220 est. 8; Gardiner-Jardine 135 est. 10; Eagle Cr. 2; 7 mi. S. of boundary 1 ; Mol Heron Cr. 1 ; Young Ranch 1 ; Gallatin highway 3; Fall River Ridge 6; Fall River Ridge 1 ; Bitch Cr. 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. to Henry's Lake to Ennis 2; 9 calved, 1 cJPorcu- pine-Warm River cow + calf Porcu- pine A few; Upper Hellroaring and Slough drainages Red Rock Lakes National Wildlife Refuge, states (1968 pers. comm.) there are a few wild bison in that area from ranched herds of some years may not actually be Yellowstone bison. 150 est. Some (bulb) Upper Timber Cr. 1;S. Gate 150 Appendix VII OCCURRENCE OF GRASSES AND GRASSLIKE PLANTS IN BISON USE AREAS. Location Type of Site Species F HV La P ULb Pond and creek edges, wet bottomlands Sedge (Carex spp. C. aqua ti Us) Beaked Sedge Nebraska Sedge Woolly Sedge Western Bulrush Swales, wet Sedge (Carex spp. C. acuta C. aperta C. aquatilis C. platylepsis C. ray no Ids ii C. xerantica) Beaked Sedge Silvertop Sedge Smallwing Sedge Woolly Sedge Spike-sedge Horsetail Wire Rush Grass species Meadow Barley Sweetgrass Timothy Tufted Hairgrass Moist meadows Sedge (Carex spp. C. acuta C. athrostachya C. platylepsis C. raynoldsii) Smallwing Sedge Valley Sedge Woolly Sedge Horsetail Long-styled Rush Wire Rush Grass species Alpine Foxtail Bluegrass Canby Bluegrass Grasses and Grasslike Plants 1 5 1 Location Type of Site Species F HV La P ULb Cusick Bluegrass X Kentucky Bluegrass X Giant Wild-rye X Sweetgrass X X Timothy X Tufted Hairgrass XX XX Moist upland sites Grass species XX X Bluegrass XX XX Giant Wild-rye X Idaho Fescue XX XX Meadow Barley X Mountain Brome XX X Columbia Needlegrass X Richardson Needlegrass X Timber Oatgrass X Timothy X Drier upland sites Sedge (Carex xerantica) X X Smallwing Sedge X Grass species X X Bluegrass XX X Canby Bluegrass X Cusick Bluegrass X Kentucky Bluegrass X Sandberg Bluegrass X Idaho Fescue XX XX Junegrass XX X Needle-and-Thread X Needlegrass X X Columbia Needlegrass X Richardson Needlegrass X Tufted Hairgrass X Wheatgrass X X Bluestem Wheatgrass X Bluebunch Wheatgrass X Slender Wheatgrass X Thickspike Wheatgrass X Mountain herbland Sedge {Carex aperta X C. raynoldsii X C. xerantica) X Ovalhead Sedge X Smallwing Sedge X Slender Rush X Wire Rush X 152 Bison of Yellowstone National Park Location Type of Site Species F HV La P ULb Bluegrass X Alpine Bluegrass X Canby Bluegrass X Idaho Fescue X Meadow Barley X Mountain Brome X Needlegrass X Purple Onion Grass X Timothy X Alpine Timothy X Slender Wheatgrass X Tufted Hairgrass X Drier mountain sites Long-styled Rush X Bluegrass X Idaho Fescue X Junegrass X Timber Oatgrass X Subalpine meadows Sedge (Carex nova X C. platylepsis X C. raynoldsii) X Hepburn Sedge X Smallwing Sedge X Bluegrass X Alpine Bluegrass X Timberline Bluegrass X Idaho Fescue X Meadow Barley X Alpine Timothy X Tufted Hairgrass X F = Firehole HV = Hayden Valley L = Lamar P = Pelican UL = Upper Lamar aData is more complete for Lamar. bAll wet sites are at higher elevations. References Allee, W. C, O. Park, A. E. Emerson, T. Park, and K. P. Schmidt. 1949. Principles of animal ecology. W. B. Saunders Co., Philadelphia, Pa. 837 p. ANON. 1909-11. Reports. In: File No. 21 & 22. Buffalo. Yell. Natl. Park Archives. 1912-13. Reports. In: File No. 21 8c 22. Buffalo. Yell. Natl. Park Archives. Bailey, Vernon. 1930. Animal life of Yel- lowstone National Park. Charles E. Thomas, Springfield, 111. 241 p. Bailey, Virginia L., and N.E. Bailey. 1949. Woody plants of the western national parks. University Press, Notre Dame, Ind. 274 p. Barlow, J. W., and D. P. Heap. 1872. Re- port of a reconnaissance of the basin of the upper Yellowstone in 1871. U. S. Gov't. Printing Office, Washington, D.C. 43 p. Barmore. William J. 1968. Bison and bru- cellosis in Yellowstone National Park: a problem analysis. Yell. Natl. Park. Typed report. 73 p. Bergstrom. R. C. 1964. Competition be- tween elk and phytophagous insects for food in the Lamar Valley, Yellowstone National Park. Ph.D. Thesis. Univ. of Wyoming, Laramie. 107 jJ- Blagkmore, WM. (Lord): 1872. Diary- fourth visit to the United States. (Tran- scription, Western Range Cattle Industry Study. State Museum, Denver, Colo.) Yell. Natl. Park Library. Photocopy. Boone and Crockett Club. 1964. Records of North American big game. Holt, Rine- hart & Winston, New York. 398 p. Booth, W. E. 1950. Flora of Montana. Part I. Conifers and monocots. The Research Foundation at Montana State College. Bozeman. 232 p. Booth, W. E., and J. C. Wright. 1959. Flora of Montana. Part II. Dicotyledons. 1966. The Research Foundation at Mon- tana State Univ., Bozeman. 305 p. Bozeman Avant-Courier. 1883. Game features of the Yellowstone Park. 1 1 Jan- uary. 1883. Park pencillings. 22 Febru- ary. Burger, John F. 1967a. Diptera: Rhagioni- dae. Effect of abundance on wildlife. Rept. to the Natl. Park Serv. Yell. Natl. Park Library. Typed. 2 p. . 1967b. Letter to Sup't. McLaughlin, Yell. Natl. Park, 13 March 1967. Yell. Natl. Park Library. Typed. 4 p. Burgess. F. 1898-99. Scout diary. Yell. Natl. Park Archives. Cahalane, Victor H. 1944. Restoration of wild bison. Trans. N. Am. Wildl. Conf. 9:135-143. Choquette, Laurent P. E., J. Guy Cousi- NEAU.and Eric Broughton.1966. Pathol- ogy. Can. Wildl. Ser. Annual Report, p. 75-80. Christman. Gene N. 1971. The mountain bison. The American West. 8(3):44-47. Cole. Glen. 1969. The elk of Grand Teton and southern Yellowstone National Parks. Research Report GRTE — N-l. Mimeo. 192 p. Conner. A. H., and Robert Cornell. 1958. Brucellosis in bison, elk, and moose in Elk Island National Park, Alberta, Canada. Can. J. Comp. Med., Vet. Sci. 22:9-20. Cook, Charles W., David E. Folsom. and William Peterson. 1869. An exploration of the headwaters of the Yellowstone Riv- er in the year 1869. In: Haines, Aubrey ed. 1965. The valley of the upper Yel- lowstone. University of Oklahoma Press, Norman. Delacy, Walter W. 1876. A trip up the south Snake River in 1863, p. 113-143. In: Contributions to the Historical Society of Montana. V. I. Rocky Mountain Pub- lishing Co., Helena. 153 154 Bison of Yellowstone National Park DOANE, G. C. 1875. The report of Lieut. Gustavus C. Doane upon the so-called Yellowstone Expedition of 1870 to the Secretary of War. Appendix M. In: Cramton, Louis C. 1932. Early history of Yellowstone National Park and its rela- tion to national park policies. U. S. Gov't Printing Office, Washington, D.C. 1876. Expedition of 1876-1877. Yell. Natl. Park Library. Typed. 44 p. Dunraven, Earl Of. 1876. The great di- vide. Chatto & Windus, London, Eng- land. 382 p. Etkin.William. 1964. Types of social or- ganization in birds and mammals, p. 256- 297. In: Etkin, William, ed. 1964. Social behavior and organization among verte- brates. University of Chicago Press. Chi- cago, 111. FRICK, E. J. 1951. Parasitism in bison. J. Am. Vet. Med. Assoc. 119:386-387. FRYXELL, Fritiof M. 1926. A new high alti- tude limit for the American bison. J. Mammal. 7:102-109. Fuller, W. A. 1959. The horns and teeth as indicators of age in bison. J. Wildl. Man- age. 23:342-344. 1960. Behavior and social organiza- tion of the wild bison of Wood Buffalo National Park, Canada. Arctic. 13: 3-19. 1961. The ecology and manage- ment of the American bison. Extrait de la Terre et la Vie. 2-1961:286-304. 1962. The biology and manage- ment of the Bison of Wood Buffalo Na- tional Park. Can. Wildl. Serv. Wildl. Man- age. Bull. Ser. l,No. 16. 52 p. Garretson, Martin S. 1938. The Ameri- can bison. New York Zool. Soc. 254 p. Gilman, N. L., and John L. McAuliff. 1956. Brucellosis, p. 538-556. In: Finch- er, M. G., ed. 1956. Diseases of cattle. American Veterinary Publishers, Inc., Evanston, 111. Grimm, Rudolf L. 1939. Northern Yellow- stone winter range studies. J. Wildl. Man- age. 3:295-306. Grinnell, Geo. Bird. 1876. Zoological report, p. 66-89. In: Ludlow, William. 1876. Report on a reconnaissance from Carroll, Montana Territory, on the Up- per Missouri, to the Yellowstone National Park. U. S. Gov't. Printing Office, Wash- ington, D. C. Hague, Arnold. 1893. The Yellowstone Park as a game reservation, p. 240-270. In: American big game hunting, the book of the Boone & Crockett Club. Forest 8c Stream Publishing Co., New York. 1899. Geology of Yellowstone Na- tional Park. U. S. Geo. Survey. Mono- graph 32, Part 2. U. S. Gov't. Printing Office, Washington, D.C. 893 p. Haines, Aubrey, ed. 1955. Osborne Rus- sell's journal of a trapper. Oregon Histor- ical Society, Portland. 179 p. . 1963. History of Yellowstone Na- tional Park, p. 84-136. In: A manual of general information on Yellowstone Na- tional Park. Yell. Natl. Park. Mimeo. Halloran, A. F. 1968. Bison (Bovidae) productivity on the Wichita Mountains Wildlife Refuge, Oklahoma. Southwest Nat. 13:23-26. Henderson, A. Bart. 1870. Narrative of a prospecting expedition to the East Fork and Clark's Fork of Yellowstone. . .1870. (Original in Coe Collection, Yale Univ. Library.) Yell. Natl. Park Library. Typed transcript. Hofer. T. E. 1927. Letter to LeRoy Hill. 5 February. Yell. Natl. Park Archives. Holmes. W. H. 1878. Exploration of the Yellowstone National Park by the U. S. Geological and Geographical Survey of the Territories, 1878. Yell. Natl. Park Library. Typed transcript. 43 p. Holt, Peter. 1899-1901. Scout diary. Yell. Natl. Park Archives. Hough. Emerson. 1894. Forest and Stream's Yellowstone Park expedition of 1894. Yell. Natl. Park Library. Newspa- per account. Houston, Douglas B. 1968. The Shiras moose in Jackson Hole, Wyoming. Grand Teton Natural History Assoc. Grand Te- ton Natl. Park. 110 p. Jones, William A. 1875. Report upon the reconnaissance of Northwestern Wyo- ming including Yellowstone National Park, made in the summer of 1873. U. S. References 155 Gov't. Printing Office, Washington, D.C. 331 p. Kittams, Walter H. 1947-58. Northern winter range studies. 2 Vol. Yell. Natl. Park Library. Typed. . 1949. Preliminary report on Hay- den Valley bison range. Yell. Natl. Park Library . Typed. 8 p. Lake Station. 1898-1911. Station re- cord. Yell. Natl. Park Archives. 1911-18. Station record. Yell. Natl. Park Archives. Le Hardy, Paul. 1873. Autobiography of Paul Le Hardy, p. 95-104. (Typescript copied from handwritten 247 p. auto- biography.) Yell. Natl. Park Library. Livingston Enterprise. 1885. News arti- cle. Mar. 7:3; Dec. 12:1; Dec. 19:3. Locker, Betty. 1953. Parasites of bison in northwestern U.S.A. J. Parasitol. 39:396- 397. MacArthur, Robert, and Joseph Con- nell. 1966. The biology of populations. John Wiley & Sons, New York. 200 p. McHUGH, Tom. 1958. Social behavior of the American Buffalo (Bison bison bison). Zoologica. 43, Part 1.31 March 1958. 40 p. McDougall. W. B., and Herma A. Bag- GLEY. 1956. Plants of Yellowstone Nation- al Park. Yell. Library and Museum, Assoc. Yell. Natl. Park, Wyo. 186 p. Marble, Charles. 1932. Fifty years in and around Yellowstone National Park and miscellaneous notes. Yell. Natl. Park Library. Typed. 36 p. Meagher, M. 1 966. Lungworm (Dictyocau- lus sp.) in bison of Yellowstone National Park. Yell. Natl. Park Library. Typed. 8 p. Mech, L. David. 1966. The wolves of Isle Royale. Fauna of the Natl. Parks of the U.S. U.S. Gov't Printing Office, Washing- ton, D.C. 210 p. Morrison, James. 1897-98. Scout diaries. 2 Vol. Yell. Natl. Park Archives. Mlrri, Ernest. 1968. Interview of 5 May 1968 by Natl. Park Service personnel. Yell. Natl. Park Archives. Tape recording. NOWLIN, D. C. 1912. Report on wild buffalo and elk, Yellowstone Park. July 22-30. Typed. 5 p. In: File No. 21 & 22. Buffalo. 1909-1 1 inc. Yell. Natl. Park Archives. Oldf.meyer. John L. 1966. Winter ecology of bighorn sheep in Yellowstone National Park. M. S. Thesis. Colorado State Univ., Fort Collins. 107 p. Park, Ed. 1969. The world of the bison. J. B. LippincottCo., Philadelphia. Pa. 161 p. Patten, D. T. 1963. Vegetational pattern in relation to environments in the Madi- son Range, Montana. Ecol. Monogr. 33:375-406. Pattie, Donald L., and Nicolaas A. M. Verbeek. 1967. Alpine mammals of the Beartooth Mountains. Northwest Sci. 41:110-117. Pierrepont, Edward, 1884. Fifth avenue to Alaska. G. P. Putnam Sons, New York, 329 p. Potter, Mrs. Lena. 1962. Notes from an interview. Yell. Natl. Park Archives. Tape recording. Quortrlp, Erling R. 1945. A report on brucellosis investigations, Yellowstone National Park. Dec. 1-20, 1944. Yell. Natl. Park Library. Mimeo. 27 p. Raymond, Rossiter W. 1880. Camp and cabin: sketches of life and travel in the west. Fords, Howard & Hulbert, New York. 242 p. Raynolds, W. F. 1867. Report of Brevet Colonel W. F. Raynolds, U. S. A., Corps of Engineers, on the exploration of the Yellowstone and Missouri Rivers in 1859- 1860. 40th Congr., 1st Sess. Senate Ex. Doc. No. 77. U. S. Gov't. Printing Office, Washington, D. C. 174 p. Robinette. W. Leslie,' Jay S. Gashwiler, Dale A. Jones, and Harold S. Crane 1955. Fertility of mule deer in Utah. /. Wild^ Manage. 19:115-136. Roe, Frank Gilbert. 1951. The North American buffalo. University of Toronto Press, Canada. 957 p. Rush. W. M. 1932a. Bang's disease in Yel- lowstone National Park buffalo and elk herds. /. Mammal. 13:371-372. . 1932b. Northern Yellowstone elk study. Mont. Fish Game Comm., Helena. 131 p. Scouts. 1908-14. Monthly reports. Yell. Natl. Park Archives. Skinner, Curtis K. 1941. Special report on Yellowstone National Park bison. Yell. 1 56 Bison of Yellowstone National Park Natl. Park Bio. Files. 715-03. Buffalo (General). Typed. Skinner, Curtis K., and Wayne B. Alcorn. 1942-51. History of the bison in Yellow- stone Park. Yell. Natl. Park Library. Typed report. Skinner, Morris F. 1965. Letter to Dr. J. D. Love, U.S.G.S. 19 Nov. Yell. Natl. Park Museum Files. Skinner, Morris F., and Ove C. Kaisen. 1947. 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Index Page Page Accidents 74 Brown, Larry 66 Anthrax 70 Browse species 93,94 Barmore, William 109 Brucellosis infection Bechler Meadows 3,5 Examination for 2 Summer range 23 Control 71 Wintering 33,88 Effect on productivity 71 Winterkill 74 First reported 70 Biotic disclimaxes 108 Rate of 54 Bison behavior Buffalo Ranch 39,67,71 Breeding activity 47,76,77 Buffalo trails 25 In snowstorms 47 Bulls "Tending bonds" 51 Distribution 36,37 Winter movement 73 Free-ranging 29,31 Bison bison athabascae Rhoads 1,13 Groups 46,84,98 Skulls 16,17 Horning of trees 104 Bison bison Linnaeus 1 Insects 83 Bison characteristics 38-49 Movements 78,85 Color 38 Physical characteristics 38 Hair 38 Population ratio 60 Horns 38 Reductions 29 Longevity 46 Sexual maturity 51 Sight 47 Show herd 29 Smell 47 Solitary 46 Speed 47 47,49,£ $1 ,84,85,89,98,99 Weight 38,39 Thermal areas 105 Bison occidentalis 13 Wallows 104,105 Bison population Weight 39 Breeding activity 47,76,77 Winter ranges 81,99,100 Composition 27,29 Wintering apart 37,96,99 Distribution 13,32,34,35,37 Calves Estimates 67 Calving 75,76 Group structure 46,90 Coat color changes 38 Interbreeding 85,88,89 Dominance hierarchy 111 Intermingling 29,88 Fetal size range 75 Isolation 89 Mortality 62,64 Movements 36,73 Numbers 60,63 see also Migratory movements Nursing 51,54 Origin 1,13,14,26 Sex ratio 58 Reproduction 50-57 Survival rates 51,54,111 see also Reproduction entries Wild herd 26,27 Blackflies (Simulium venustum) 69 Chapman, W. S. 31 Blacktrail Dee Creek 104 Childs, Frank 13 157 158 Bison of Yellowstone National Park Page Climate 8 Effect of wind and cold 56 Seasons 9 Colter, John 12 Cows Abortions 54,70 Brucellosis 70 Calving 75,76 Low reproductive rates 56 Pregnancy rates 54 Sexual maturity 50 Winter range preference 89,90 Crystal trap 2,58 Dominance hierarchy 1 1 1 Effects on habitat 103-109 Plant cover 106 Trails and wallows 104,105 Trampling 105,107 Trees and treeline 1 /AO 1 f\ A 103,104 Upland sites 108 Elk (Cervus canadiensis) 47 104,107,108 1711, I , 1 1 X ' " 1 f-> 1 Elk Island National Park 69 Face fly (Musca autumnalis) 70 Fenced herd 27-30 Composition 28,30 Discontinued 32 Intermingling 29 Fetal sex ratio 55,56 Firehole region 2,3 Area 5 Calving 76 Effects of bison 106 Interbreeding 86 Mary Mountain area 32 Migratory pattern 78,84 Thermal areas 100,102 Vegetation 1 o 1U Food habits 2,90,93 Foraging areas 96-98 Composition data 94 Effect on plant cover 106-109 Forbs and browse 94 Forested sites 97 Snow depth 73 Page Thermal sites 97,108 a 13 Use of areas 96-103 Forbs in forage 92-94 Goodnight herd 26 Grass species 91-95 Great Plains bison 14 Grizzly (Ursus horribilis) 72 Hague, Arnold 15 Haines, Aubrey 13 Hayden Valley 3 Area 5 Breeding activity 77 Bulls wintering 36 Calving 76 Counts 33 Grass species 94 Horning, rubbing 103,104 Insects 83 Interbreeding 86 Migratory patterns 78,84 Summer range 23,81,89 Thermal areas 100,102 Vegetation 10 Wallows 105,106 Winter range 23,33,96 Hemorrhagic septicemia 70 Herd reductions 1 2,29,32,52,66,67,72,88 Methods used 2 Hornfly (Haematobia irritans) 70 Horse and deer flies (Tabinidae) 69 Hot springs or fumaroles 102 Insects, biting 69,70 Summer movement 82,83,97 Lacey Act 12,17 Lamar region 1,3,12 Area 4 Brucellosis 54,70 Bulls 60 Calving 75 Increase 67 Management practices 26,32 Movement 82 Poaching 17 Reduction 32,65,66 Index 159 Page Summer range 23 Trapping 58 Vegetation 10 Winter range 23 31,33,36,89 Lungworm (Dictocaulus sp.) 69 Madison Plateau 3,5,33 Elk 194 Summer range 23,65 Management objectives 71 Management practices 1,2,12,26 Aerial counts 32,36,60 Buffalo ranch 67 Change to natural preservation 32 Cows and calves removed 52,53 Hay-baiting 31,67 Herding by helicopter 33 Population counts 32 Reductions 29,32,52,67 Roundup 29 Tagging 2 Mary Mountain herd 31,32 Age classes 60,64 Breeding 76 Increase 65,68 Interbreeding 86 Reduction 66 Semidomestication 68 Sex ratio 60 Wintering 33,89,90 Migratory movements 77,97 Beyond park boundaries 85 Biting insects 82 Patterns 90,97 Spring and fall 78,84 Summer 81,82,84 Winter 84 Mirror Plateau 3,4 Area 4 Breeding activity 76 Fossil cranium 13 Migratory pattern 78 Rubbing of trees 103 Skull 17 Summer range 23,31,36 Page Trails Vegetation 10 wild nera 9A Mixed herd groups no CO r» 11 Bulls A 1 4 / Can numbers OU,Oo Distribution no Q o 9 A Group size A& 40 Group structure 90 Migratory pattern 11 *7tt QO Population shifts o / ,oo Survival factors 1 1 1 lo Thermal areas QQ 1 f\(\ 1 no Winter movements HA ft Ft ftQ on Moose (Aires alces) DO Mortality Accidents 1A 1 4 nulls UJ Calves A9 Azl Disease-caused in /0 Natural a p. p.i Predation Subadults ClA ia 04, /4 winterKiii 1% 1A 1 O, 1 4 Mosquitoes (Aedes sp.) Mountain bison 1 A 14 Characteristics 1 4 1 ^ Distribution 1 1 ■ 1 Q 1 /, lo History 15-17 Increase 29 Migrations 15 Numbers (1902) 17 Skulls 17 Subspecies 89 Mountain buffalo history 15-17 Mule deer (Odocoileus hemionus) 56 Murphy, R 85 Muscidae 69,70 Mush pots- Mudkettles 97 National Bison Range 69 Conjunctivitis 70 Nez Perce trap 2,33,58 Brucellosis 70 Helicopter drive 84,89 Norris 15,17,25 160 Bison of Yellowstone National Park Page Pablo-Allard herd 9A Parasites AO. 7fl oy, /u Pelican region 3 Area 4 Brucellosis o4, /U Calving 75 Herd fluctuation 66,67 Maximum population 113 Migratory pattern 82 Reductions 110 Separation 88 Vegetation 10,96 Wild herd 26 Winter range 23,33,36,96,102,108 Pierson, Dave 36 47,54,71,72,78 Pitchstone Plateau 3,5 Summer range 23,65 Plains bison 1 Subspecies OA 97 Wild herd 26,27 Poaching 17,1 10 Ponumpta Hot Springs 36,99 Population regulation 110-113 Counting practices 32,33 Natural regulation 110,111 Neckbands 2,36 Numbers (1902) 17 Numbers (1964) 33,108 Reductions 2 29,50,60,65,71,110 Slaughter operations 2 Tagging 2 Population structure 8,58-60,89 Age classes 58-60,64 Fluctuations 67 Interbreeding 85,86 Sex ratio 58,60 Trends 68 Wild strain 29 Predation 72 Quortrup, E.R. 75 Reproduction 50-57 Calving 75,76 Eff ect of winter 56 Page Pregnancy rates 51,54,1 1 1 Sex ratios 55,56 Sexual maturity r;n f;a Research 1 Methods used o I Rocky Mountains on oy Rubbing of trees 103,104 Rumen samples O (\(\ C\1 Russell, Osborne 1 A 14 Sagebrush-grassland 1 1 ^ 1 1 J Seasons Q y Sedge 90-93 94,95 Thermal influence 102 Winter forage okuiis 16 17, 39 Slaughter operations o 4 Snipe flies (Rhagionidae) fiQ Snow Trapping Winter foraging 1 o Soils f; a Erosion 107 Qtcihl^ flv {^tnmnxvs calcitrans) 70 Stradley, Jim 32, 33, 36, 66, 85, 102, 113 Subspecies 13,14,26,27 Rocky Mountains 89 Summer ranges 31,36,65 Historic 23 Survival factors 113 Symphoromyia 69,83 Tape worm ( Moniezia benedini) 69 Thermal areas 9,96-98 Survival factor 113 Thermal influence 102,103 Trampling 105 Use of 99,100,108 Wintering sites 97,98 Trapping 58 Population shifts 88 Sex and age structure 59 Tuberculosis 70 U.S. Forest Service 10 Upland sites 108 Index 161 Page Upper Lamar region 3,4 Area 4 Summer ranges 23,3 1 ,36 Trails 105 Vegetation 9- 1 1 Plant species 1 1 Visitors' best viewing 48 Wallows 104,105 Wild herd 1,12,26,68 Present composition 27 Reproduction rate 5 1 Wild strain estimate 29 Wildlife protection 12 Wilson, Richard 14 Wind, effect of 56 Winter ranges Effect on plant cover 106,108 Factors of suitability 112,113 Habitual 89,90 Sedges 94,96 Thermal sites 97,98 Page \A/intf»rlf ill 73,74 Wire rush 94 Wolves (Cams lupus) 72 Wood Buffalo National Park bison 51 Diseases 70 7 1 Parasites 69 IXCIJI k)UL UCll VC laltJ 56 Sex ratio 60 Winter climate 56 Wolves 72 Yearlings 54 Moose 56 Mortality 64,111 TraDDinET 58 Yellowstone National Park 3-12 Bison range 3 Climate 8 Geologic history 3 History 10 Indians 10 Nine regions 3-5 Seasons 9 U. S. Department of the Interior U. S. GOVERNMENT PRINTING OFFICE ; 1973 O - 521-650