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Study Area

Elk Population

Population Dynamics


Elk Habits

Effects on Habitats

Elk Management






Research Report GRTE-N-1
The Elk of Grand Teton and Southern Yellowstone National Parks
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Information on elk habits was obtained while covering established routes through the study area. Routes were covered under a system which employed periodic aerial flights, horseback and foot travel through roadless areas, and vehicle trips. Observations of elk numbers, activities, occurrences on different habitat types, and locations were recorded. Most observations were made during early morning or evening when the animals were more observable and feeding. Animal locations were determined from gridded topographic maps. Sex and age classifications and identifications of individually marked animals were made whenever possible. Binoculars and a variable 15 to 60 power spotting scope were used.


Spring Migrations

During January through March periods when they were being fed hay, large groups of 1,000 to 4,000 elk concentrated on two or three feed ground sites within the south half of the National Elk Refuge. As snow-free areas became available and new grass growth started during April and May, the animals dispersed from feed grounds and ranged into the north half of the refuge. Snowstorms or inclement weather halted or even reversed these spring dispersals.

First migrations of significant numbers of elk (500 or more counted) off the refuge and onto Grand Teton lands occurred on April 30 in 1963, May 14 in 1964 and 1965, May 2 in 1966, and May 9 in 1967. Numbers moving onto Grand Teton Park progressively increased once migrations started. Movements to limited snow-free areas in the northern portion of the valley occurred over extensive flats with up to 1 foot of snow and over much deeper drifts. Such movements took the animals from refuge areas where new vegetation growth was abundant into areas where new growth either had not started or was so short as to be unavailable. The rate of spring movements by elk which migrated through Grand Teton into southern Yellowstone and the use of particular areas by females for calving appeared to be strongly influenced by snow accumulations in mountain passes. Proportionately fewer females with calves appeared to be present in southern Yellowstone during late June in 1962 and 1965 when June 1 snow depths at a representative 8,000 foot mountain pass exceeded 60 inches (Table 10). The proportion doubled in 1963 and 1966 when June 1 snow depths were 28 and 20 inches respectively. The highest proportion in 1964, with a 43-inch snow depth, appeared to represent a situation where intermediate mountain areas had sufficient snow accumulations to hasten, but not prevent, movements to lower elevations in Yellowstone Park. Yorgason (1964) reported from aerial flight observations that large numbers of elk migrated into Yellowstone Park over at least 10 councontinuouses of snow cover between May 9 and June 13. Alternative, more snow-free, but less direct, routes up main drainage courses were available. These apparently did not serve as alternative migratory routes for the majority of the animals that habitually traveled through mountain areas.

Table 10.—Numbers and sex and age classes of elk observed in Yellowstone Park areas in late June in relation to snow depths at an 8,000 foot station.

Period Total
Classified Percentages
June 1

June 24, 28, 19622682413063 71061
June 24-27, 19635714492562132028
June 26, 19646734761465213243
June 29, 19654083803460 61070
June 27-July 1, 19668727811571142020

Elevational Movements

Recorded locations from 16,103 elk observations showed that progressively greater numbers of animals moved from low to high elevation ranges above 8,500 feet in southern Yellowstone through June and July (Table 11). Peak numbers were observed on high ranges during the last half of July during 4 of the 5 years; during the first half of July in 1966. The animals used forest types at both high and low elevations to a greater extent during the first half of August and were generally less observable. Movements from high to low elevations and even greater use of forest cover occurred during the last half of August and September. Some animals moved back to high elevations during late September and October in years when fall storms were not too severe.

Sex and Age Differences

Classifications of 12,682 elk showed adult males and females not attending calves were most involved in initial June movements onto high elevation ranges above 8,500 feet (Figure 9). Females with calves or attached to female-calf groups was the population segment most involved in progressive movements to high ranges through July. Movements of adult males to high ranges appeared to be largely completed mid-July. Yearling males occurred in about equal proportions in early and late arriving groups. Adult males usually occurred in small groups apart from other population segments and at the highest elevations during late July. All sex and age classes were involved in early or mid-August dispersals into forest habitats and late August through September movements to lower elevations.

Fig. 9. Percentages of female, calf, yearling, and adult male elk observed between 6800 to 9800 and 8600 to 10,000 ft. elevations within mountain areas during June through October periods, 1962-1966. (click on image for an enlargement in a new window)

Table 11.—Numbers and percentages of elk observed on mountain range areas above 8,500 feet, 1962-1966.

Period Total elk
Elk above 8,500 feet

June 16-303,3721,52545
July 1-153,1261,82458
July 16-314,6063,59778
August 1-152,5211,80071
August 16-311,21740033
September and October1,261


Insect Relationships

Midsummer aggregations of large numbers of elk at high elevations were influenced by molesting insects. Horseflies (Tabanidae) were obvious molesters of elk. Mosquitoes (Culicidae) caused avoidance reactions when very abundant. An unknown insect, possibly a heel fly (Oestridae), caused pronounced avoidance reactions in elk, but did not molest men or horses.

Numbers of elk observed on high elevation ranges during July and early August with different intensities of insect molesting activity are shown in Table 12. Intensities were considered high when elk almost solely occupied with avoiding or dislodging insects, moderate when such actions were secondary to other activities, and light when the animals appeared to be completely or almost unmolested. Peaks of molesting activity were through midday periods. High intensities caused obvious aggregations of elk on ridgetops and/or bedding in dense vegetation.

Table 12.—Numbers and average size of elk groups observed on high elevation ranges in relation to molesting insects.

Year Relative abundance of
molesting Insects
Elk above 8,500 feet
Number and average group size ( )
July 1-15 July 16-31 August 1-5

1962 Moderate late July, early August 328 (27) 650 (20) 609 (24)
1963 Intense late July; moderate early August 422 (23) 1,036 (77) 486 (20)
1964 Low all summer 256 (21) 671 (15) 136 (8)
1965 Intense early August 50 (27) 990 (35) 493 (19)
1966 Intense early July 768 (18) 250 (10) 76 (7)

Effects of molesting insects were most apparent in late July of 1963 and early July of 1966. This coincided with relatively high numbers of tabanids and the probable heel fly. The intense molesting action in early July caused the unusual occurrence of some females with young calves at elevations up to 10,000 feet. The habits of elk with the almost complete absence of insect molesting activity are reflected by the 1964 data. Elk remained scattered and in comparatively small groups throughout the summer. Similar scattered distributions occurred after early July of 1966.

Dispersals of elk into smaller groups usually occurred in early August. The effects of insect molesting activity occurring in or extending into August are illustrated by the 1962 and 1965 data. This suggests insects partially prevented elk dispersals into smaller groups. The relatively high elk numbers and group sizes seen during late July of 1965 appeared to result from the first migrations of large numbers of females with calves into Yellowstone National Park. These migratory groups dispersed and remained scattered in the absence of significant numbers of molesting insects through the remainder of the summer.

Intermingling Between Herds

The extent of intermingling between animals from the refuge and northern Yellowstone winter herds on the study area was indicated by 2,340 locations of marked elk (Table 13). Animals from these two almost 100-mile distant winter areas were shown to be intermingled to the greatest extent on Yellowstone summer ranges 50 to 55 miles from the south boundary of the refuge, to a lesser extent within 45 to 49 miles, and to a very limited extent on ranges south of Yellowstone Park. Simple proportion calculations, that related estimated herd sizes to numbers marked, suggested that at least 90 percent of the animals using the sampled central southern Yellowstone ranges were from the refuge winter herd during 1963 and 1964 (Cole, 1965). This figure may not be entirely applicable for the east and west portions of southern Yellowstone Park. A portion of the animals summering in the eastern Two Ocean Plateau and Thorofare regions were from the Gros Ventre winter herd and another herd which migrated east to winter ranges near Dubois, Wyoming (Murie, 1929; Anderson, 1958; Yorgason, 1964). A portion of the animals summering on the western Pitchstone Plateau region migrated southwest to Idaho winter ranges (Anderson, 1958) and possibly north to winter ranges along the Firehole and Madison Rivers inside Yellowstone Park.

Table 13.—Numbers of marked refuge and Northern Yellowstone elk observed within distance zones from the south boundary of the National Elk Refuge, 1963-1966.

Month Grand Teton
North of
Southern Yellowstone Park
7-25 miles 26-44 miles 45-49 miles 50-55 miles


1 NY

4 NY
3 NY
19 NY

1 NY
6 NY
1 NY
1 NY


In summary, the intermingling of elk from widely separated winter ranges, on and across mountain divide or plateau areas in southern Yellowstone Park, was a common occurrence. The presence of marked animals from two different winter ranges in a single group was also common during this study. Marked animals from three different winter ranges were occasionally seen together.

Despite this common intermingling on summer ranges, interchanges of animals between winter herds seemed to be less than would be expected. Over the 1962 through 1967 period, a maximum of three marked animals from the northern Yellowstone herd were present on refuge winter ranges during the winter of 1964-65. Numbers observed during other years ranged from none to two. Two marked refuge elk were observed on northern Yellowstone winter ranges in 1963-64; single animals, during each of the other 4 years.

Fall Migrations

The general pattern of fall and early winter migrations back to the National Elk Refuge is illustrated by the September through November locations of marked elk (Table 13). Other migration information was primarily from track counts on a 47-mile road transect and periodic counts of animals appearing on the refuge. The road transect started at park headquarters at Moose, extended through the west side of the park to Moran, and from here east to the top of Togwotee Pass (Figure 7). Elk track counts were started in 1945 by Cahalane (1949). They have been made cooperatively with Wyoming personnel since 1950, Park Service and Wyoming biologists alternate senior authorship in preparing annual migration reports. Interested persons are referred to these reports for detailed information on migrations.

Migration Chronology

Records over a 40-year (1927-1966) period date main migrations occurring 4 times in October, 24 times in November, and 2 times in December (Yorgason and Cole, 1967). Three of the four "main" October migrations occurred consecutively from 1960 to 1962. Combined numbers rating during November and December were actually greater than October. Track count records and aerial observations indicated most of the elk making early October migrations came from Grand Teton valley and mountain areas. Refuge counts indicate habitual October migrations by comparatively small numbers of elk started in 1958 (Table 14). Road closures within Grand Teton Park and specially designed hunting seasons aided in curtailing early migrations after 1964.

Tabulations of tracks crossing Grand Teton transects after snow fall and direct counts of elk within periods show the overall chronology of migrations for the majority of the animals summering in both national parks. Nine counts over the 10 years between 1957 and 1966 indicated that, on the average, about 5, 16, 28, 40, and 11 percent of these elk had migrated during October 1-15, October 16-31, November 1-15, November 16-30, and December 1-30 periods, respectively. These yearly track counts sampled the movements of an estimated 5,000 to 7,000 animals, depending upon the extent of early migrations before snow cover. Counts tallied between 40 and 80 percent of these animals. Low counts mainly resulted from snowstorms or mass movements obscuring tracks, or thaws that temporarily removed snow cover.

Table 14.—Bimonthly counts of elk on the the souto-thirds of the National Elk Refuge.

195819591960 196119621963 196419651966

Oct. 1-153007751,1001,7262,450145145036
Oct. 16-318091,5502,5003,4702,5007281,000375300
Nov. 1-151,5002,5333,5004,5002,4905,0001,8005211,540
Nov. 16-305,0004,0005,800--12,6007,0002,9002,3004,000
Dec. 1-154,2003,8005,8506,200--16,2254,5003,900--1
Dec. 16-314,5004,2006,200--14,036--16,000--1--1

1 Elk scattered; count not possible.

Number Relationships

Accumulated track count records since 1949 show that the numbers proportions of elk crossing transect areas inside and outside Grand Teton have greatly changed over an 18-year period. Illustrative counts, at selected 6- and 7-year intervals, which sampled large numbers of elk are shown in Table 15. With the exception of the most eastern portion of the Four Mile Meadow to Togwotee Pass section (Figure 7), the transect mainly sampled animals migrating to the National Elk Refuge. The changes in numbers and proportions crossing different transect sections were generally progressive from about 1950 through 1958 and coincided with a period of relatively high hunting kills. Proportionately greater kills were apparently made on the more accessible migratory segments that crossed the eastern portions of Grand Teton (Buffalo and park boundary sections) and the transect sections outside park boundaries. Numbers decreased. Migratory segments that traveled through less accessible hunting areas (roadless or roads blocked by snow when migrations occurred) north of Grand Teton before crossing the Snake River and Pacific Creek transect sections were obviously less heavily hunted. These migratory segments increased. Increases in elk numbers crossing the Burnt Ridge section resulted from a buildup of a resident summer herd in Grand Teton after hunting eased on low security level valley habitats west of the Snake River.

In summary, the increases and decreases in particular migratory segments appeared to be in relation to their accessibility to hunters. Accessibility was largely determined by the presence of roads or the extent to which roads were blocked by snow during elk migrations.

Table 15.—Numbers of elk tracks crossing transects inside and outside Grand Teton National Park in years of maximum counts at 6 to 7 year intervals.


Park transects:
Burnt Ridge4249571,672
Snake River1,2851,0912,122
Pacific Creek Bridge7001,0251,416
Buffalo River Bridge26625999
Park Boundary842626371
Park Total3,5173,9585,680
Outside transects:
Four Mile Meadow3,1461,1121,028
Togwotee Pass7003,102470
Outside total7,3385,3731,893

Grand total10,8559,3317,573

Percent in park324275
Percent outside park685825

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Last Modified: Tues, Jan 20 2004 10:00:00 pm PDT

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