The Bison of Yellowstone National Park
NPS Scientific Monograph No. 1
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The Historic Population

THE GENUS Bison PROBABLY INVADED North America during the later part of the early Pleistocene. The bison occupying the continent in historic times were descendants of a second migration of Bison from Eurasia, which crossed the Bering Straits at the start of the late Pleistocene according to Skinner and Kaisen (1947). Of the invading species, only one persisted to give rise to B. occidentalis, the ancestor of B. bison, the modern form. Two subspecies, B. b. bison and B. b. athabascae, are recognized by cranial evidence, although historical accounts suggest there may have been others (Roe 1951). The form athabascae is apparently 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 o Yellowstone National Park (Pattie and Verbeek 1967). In 1964 a fossil cranium (B. b. athabascae) was found embedded in a natural oil seep on the Mirror Plateau in the park.

The Yellowstone bison of historic times were a remnant of a once much more extensive bison population, known to trappers and Indians, which inhabited the mountain ranges and the intermountain valleys of the Rockies and extended on west into Washington and Oregon. Most of these bison were gone by the 1840s (Aubrey Haines 1968 pers. comm.). According to the distribution map of Skinner and Kaisen (1947), 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, former Yellowstone ranger who worked on Red Rocks land acquisition matters during the mid-1930s, heard that 300 bison died there during a bad winter many years earlier (1965 pers. comm.). Many skulls have also been taken from the Mud Lake area of Idaho, approximately 55 miles southwest of Yellowstone (Richard Wilson 1968 pers. comm.). Osborne Russell, writing in 1835, mentions the large numbers of buffalo (bison) seen in both the Red Rock and Mud Lake areas (Haines 1955). Doane (1876) comments that "buffalo skulls are strewn by thousands —" in the Yellowstone valley about 40 miles north of the park. Accounts of wild bison adjacent to and within the park, dating from 1860 through 1902 (Appendix II), leave no doubt that substantial numbers of bison inhabited the Yellowstone Plateau at all seasons, and long before the killing of the northern herd of Great Plains bison in the early 1880s.

A misconception of some writers — that Yellowstone's bison of historic times were displaced survivors from the Great Plains slaughter — probably stems from: (1) the lack of recognition of two subspecies of Bison bison; and (2) the impression that early explorers found little "game" in the Rocky Mountains. Three factors contribute to the idea that bison were sparse in the mountains. Compared to the abundance of certain large mammals on the plains, the mountains probably seemed almost uninhabited. Secondly, travel routes followed river valleys and drainages, crossing small areas of high summer range at few locations, often at a season when biting insects may have driven the game from the lower elevations of passes to adjacent higher slopes and ridges. Finally, the few early travelers who wrote of their journeys, including official government parties, often commented only on wildlife which was actually sought out or shot for food.

Mountain Bison

The existence of mountain bison, different in appearance and behavior from the plains type and gone from much of their range by the 1840s, has generally been little known. Christman (1971) reviews historical evidence for the subspecies, their distribution to the west of the plains type, and reasons for their early disappearance. He believes the Indians' acquisition of the horse was the factor underlying the extermination of mountain bison from extensive areas of original range, particularly in Washington, Oregon, and Idaho.

Many early references to Yellowstone bison use the term "wood" or more commonly "mountain" bison or buffalo (Fig. 9); some of the characteristics of the race were recognized by a number of early travelers and observers. Historical accounts generally agree that, compared with the plains bison, these mountain animals were more hardy, fleet, and wary, and had darker, finer, curlier hair. Sex and age differences among animals seen may account for discrepancies in description of size. The geologist Arnold Hague (1893) provides the following:

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

The Park buffalo may all be classed under the head of mountain buffalo and even in this elevated region they live for the greater part of the year in the timber. . . .most unusual, save in midwinter, to find them in open valley or on the treeless mountain slope. They haunt the most inaccessible and out-of-the-way places, . . . living in open glades and pastures, the oases of the dense forest, . . . the rapidity of their disappearance on being alarmed. It is surprising how few buffalo have been seen in midsummer, even by those most familiar with their haunts and habits. They wander about in small bands. . . .

Blackmore (1872) was informed that the mountain buffalo congregated usually in bands of 5-30, rarely more. Other observers agree that the bands were small, and the animals quite wary. Superintendent Norris described them as "most keen of scent and difficult of approach of all mountain animals" (Superintendent of the Yellowstone National Park 1880).

Altitudinal migrations were another characteristic of mountain bison (Christman 1971). Historical accounts from Yellowstone also suggest this habit. Superintendent Norris, in his annual report of 1880, describes summer and winter distributions of bison in the park, stating clearly:

. . . summer in the valleys of the Crevice, Hellroaring, and Slough Creeks, and the mountain spurs between them, descending with the increasing snows, to winter . . . East Fork [Lamar]. . . . and as the snows melt . . . returning to their old haunts.

The historical accounts of dates and locations of bison (Appendix II) collectively also show a repetitive pattern of seasonal bison distribution which reflects altitudinal movements.

Historical accounts recognizing a mountain buffalo are supported by limited cranial evidence. Skinner and Kaisen (1947) show an overlap in general distribution between mountain and plains bison along the east slopes of the Rockies, including Yellowstone, but state that ranges for historic times must be based on early accounts plus occasional bones or crania. Seven skulls from Yellowstone's original wild herd were picked up on the ground along the Gardner River and at Mammoth in 1902. All had weathered surfaces. These were considered as most likely representing athabascae. The 1964 skull (Fig. 10) found on the Mirror Plateau was identified by Skinner (1965) as "an exceptionally long horned, apparently young Mountain bison = B. (B) b. athabascae No Yellowstone skulls which predate the 1902 introduction have been identified as plains type.

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

Numbers and Distribution through 1902

Numbers and distributions from the historical accounts of Appendix II are shown in Table 2. Norris (Superintendent of the Yellowstone National Park 1880) estimated a total of 600, dividing the population into three herds according to area. By this date, poaching had certainly begun inside the park, along with increasing pressure on an ever-shrinking mountain bison population outside. Numbers in a given area fluctuated then as now. After consideration of all the listed reports of numbers and distribution, the historical population, ranging in part beyond the park boundaries, is estimated to have been perhaps 1000 animals. This seems reasonable when bison habits and behavior and difficulties of making counts are all considered. Subestimates by area and season are at the bottom of Table 2. They are made to provide a reference point 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 difficulties—the population probably was higher; perhaps 40-50 mountain bison survived. The near-extinction in about 25 years was the result, initially, of sport and table hunting on 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 reflect the extent of the kill. Although the Howell poaching case resulted in passage of the Lacey Act in 1894, the population declined further as poaching, primarily from the west side, continued. Natural losses, coupled with scattering of the few remaining animals, left a minimal breeding population in the most remote places of the Pelican-Mirror-Upper Lamar country.

The distribution, to the extent known, of the original population was similar to the present distribution, but larger numbers used certain areas more extensively and ranged beyond the park boundaries part of the time. Figure 11 shows the probable general distribution and population movements of mixed herd groups. The term "mixed group," as in Fuller (1960), is used here also for groups which usually contain some mature bulls 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.

TABLE 2. Summary, native bison information, 1860-1915.

YearWest of
North of
not stated

1860one bandb

1863many trails



numerous sign




herd groups

7 calves captured

abundantscores hunted




100 200

small bandsmall band




400; one bandmarket hunting


7 tourist hunting200
188590 estim.


market hunting poaching 20 tourist hunting200-300


decrease in market hunting
1887much scattered9-10
40-80 20-30

1888 200




someabundant fresh sign


small band, larger groups—winter

189160 + 12 - 15 calves, sing. & other small groups

poachingincreasing 200-400



poaching implied 2 calves captured400; 20% calves
50-60 inc. 13 calves

seen often12 poached400

1036 + 7

a few inc. calves24
1895100 (rumor)

3 + 4 + 103 calves west side poaching200


3 + 12 + 3 sign 910 est. west side poaching25-50
1897sign 20
sign 5sign 2

18981 + 5sign 3; sign 2; sign 4; 1 + 2sign 5-61 + 5
sign 21


5 + 1202 + 4 + 3 + 15

2-Snake R.

1 calf50 +

29poaching implied39




16 adults
3 calves
19 adults—winter

2 male calves captured for introduced herd

211 (5 female 6 male)12 (summer)

1 female calf captured for introduced her, 4 Ad. 1 Yrlg.


1907sign 6
sign 15


2 adults male20 maximum


23 + signspring, summer

1 male calf captured for introduced herd

29 max.5 + sign


827 inc. 2 calvessign 1

19121 male

48 inc. 10 calves

49 thriving



considerable numbersincreasing

31 (5 males, 6 yrlg., 4 calves inc.)

Estimate of Historic Population, Winter

Estimate of Historic Population, Summer300

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

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

From northeast to southwest, the four areas of historic summer range were: north of Lamar, Upper Lamar-Mirror Plateau, Hayden Valley, and Madison-Pitchstone plateaus. Large numbers of bison apparently ranged at least three of the four areas. North of Lamar, the summering herds of the northern part of the Absaroka Range split south to the Lamar Valley and north beyond the park to other valleys to winter. On the west side, the greater part of the summering herds of the Madison-Pitchstone plateaus probably moved southwest beyond the park toward the east end of the Snake River plains (Mud Lake area) as Norris presumed (Superintendent of the Yellowstone National Park 1880). Historically, as now, the Upper Lamar-Mirror Plateau was used extensively. The importance of Hayden Valley as historic summer range is less clear. 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 regularly wintered in Lamar, Pelican, and Hayden valleys (Fig. 12). The Firehole seems to have been less important. Snow conditions common in the Bechler Meadows make it unlikely that large numbers habitually wintered there, but certainly small groups must have since calves were captured there in early spring (Murri 1968).

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

Historical reports do not indicate groups along the Madison and Gallatin rivers to the northwest, within the park, but Raynolds (1867), while crossing from Henry'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 Cougar Creek) as they did in the 1950s.

Knowledge of travel routes used by people during the early days of the park, which probably followed main game trails, suggests relative game population numbers, locations, and movements (Fig. 11).

Hague (1893) mentions the lack of buffalo trails, but he was comparing Yellowstone to the plains. Definite buffalo trails did exist (DeLacy 1876). Norris' (Superintendent of the Yellowstone National Park 1880) map shows a trail northeast across the Mirror Plateau which follows the route of present buffalo trails. The usual Pelican-Upper Lamar route (in part an elk trail) once crossed Lovely Pass between Raven and Mist creeks (Superintendent of the Yellowstone National Park 1897). Movement of bison across the Mary Mountain route between Hayden Valley and the Firehole, commonly used by people prior to construction of a road along Yellowstone Lake, was implied by earlier writers, and stated as fact by Hough in 1894. Routes in use 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.

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Last Updated: 24-Jan-2005