Differential Preference of Wintering Mule Deer for Accessions of Big Sagebrush and for Black Sagebrush

Abstract

Free-roaming mule deer showed significant differential preference for accessions of big sagebrush (Artemisia tridentata) grown in a uniform garden. Mule deer also selectively preferred certain accessions of black sagebrush (A. nova). The role of monoterpenoids (essential or volatile oils) in determining preference among accessions and taxa of Artemisia-the sagebrushes-and the role of sagebrush as a food of starvation is discussed. Differential preference of mule deer for populations and individual plants of big sagebrush (Artemisia tridentata) has been noted by several workers (Smith 1950; Plummer et al. 1968; Winward 1970; Hanks et al. 1973; Stevens and McArthur 1974; Winward and Tisdale 1977; Willms et al. 1979; and McArthur et al. 1979). Few, however, have quantified their observations. Hanks et al. (1973), Sheehy (1975), and Scholl et al. (1977) did quantify their observed preferential differences. Of these workers, only Sheehy (1975) made statistical comparisons. He found that mule deer significantly preferred some sagebrush taxa over others. Preference of wintering mule deer for accessions of big sagebrush is one of several key characteristics being considered in our selecting and breeding program (Welch and McArthur 1979a). Therefore, we undertook this study to expand our knowledge base concerning mule deer preference for accessions of big sagebrush (A. tridentata) and for black sagebrush (A. nova) grown in a uniform garden. Materials and Methods From a uniform shrub' garden located at the Gordon Creek wildlife management area near Helper, Utah, 10 accessions of big sagebrush (Artemisia tridentata) and four accessions of black sagebrush (Artemisia nova) were chosen to determine differential preference by free-roaming, wintering mule deer. The accessions (plant material from a specific site) were transplanted onto the garden as wildlings from various Intermountain areas (Table 1). For each accession of big sagebrush, 10 plants were randomly selected. Plants were approximately the same age (planted 1968-1971). Twenty annual leaders per plant were measured to the nearest centimeter during mid-October 1977 and 1978. The leaders were selected at random over the entire crown of the plants. The 20 measurements per plant were used to arrive at a mean annual leader length (before browsing) for each plant. After the winter, and before spring growth, the plants were remeasured in the same manner as they were in October and a mean annual leader length Authors are research plant physiologist and research geneticist with the U.S. Dep. Agr. Forest Service, Intermountain Forest and Range Experiment Station, Shrub Sciences Laboratory, Provo, Utah 84601; and wildlife research biologist with the Utah Division of Wildlife Resources, Shrub Sciences Laboratory, Provo, Utah 84601. Manuscript received March 4, 1980. 'The uniform shrub garden at the Gordon Creek wildlife management area near Helper, Utah, is cooperatively maintained by the Utah State Division of Wildlife Resources (W-82-R) and the Intermountain Forest and Range Experiment Station. Table 1. Locations of 10 accessions of big sagebrush (A rtemisia tridentata) and four accessions of black sagebrush (Artemisia nova) used to determine differences in preference of wintering wild mule deer. These accessions were grown on a uniform garden near Helper, Utah. Species Subspecies Accessions County and State tridentata vaseYana Hobble Creek Utah, Utah Spanish Valley Grand, Utah Indian Peaks Beaver, Utah Milford Beaver, Utah Monticello San Juan, Utah tridentata tridentata Indianola Sanpete, Utah Loa Wayne, Utah Dove Creek Dolores, Colorado Marysvale Piute, Utah tridentata wv'omingensis Trough Springs Humboldt, Nevada nova Lund Iron, Utah Manti Sanpete, Utah Pioche Lincoln, Nevada Pine Valley Millard, Utah (after browsing) was determined. Percent used was calculated by dividing the mean leader length after browsing by the mean leader length before browsing, and then multiplied by 100. This method of measuring leader length contained a precision error term of 4%. During the first year, we had the occasion to visit the shrub garden before the start of winter (December 12, 1977). Significant browsing of the big sagebrush was noted. We remeasured the big sagebrush in the manner described above so we could determine the amount of big sagebrush eaten before winter's onslaught. For black sagebrush, 10 plants per accession were analyzed by the ocular method (National Academy of Sciences 1962) to estimate deer use. This was done only in the winter of 1978. A completely random-designed analysis of variance was used to detect significant effects due to accessions. Hartley's multiple range test was used to compare accession means (Snedecor and Cochran 1967). A t-test with paired observations was used to compare winters (Snedecor and Cochran 1967).