Abstract - Food Habits and Ecological Relationships of Elk to Other Herbivores in Wind Cave National Park
Wydevan, Adrian P. 1977. Food Habits and Ecological Relationships of Elk to Other Herbivores in Wind Cave National Park. Iowa State University. Final Report. 208 p.
Food habits, habitat use, physical condition, and competition of elk (Cervus elaphus) with other herbivores in Wind Cave National Park (WCNP), South Dakota, were studied from June 1976 to August 1977. Data on food habits and habitat use are necessary for establishing optimum population levels of elk and assessing potential competition with other herbivores.
Vegetation analysis was conducted seasonally on typical examples of major vegetation sites. Available forage (kg/ha of herbs and low-growing shrubs) was estimated during mid-summer 1977 to be 934 on shallow sites, 863 on silty, 890 on clayey, 1536 on overflow, 1391 on stony hills, 326 on pine-juniper (Pinus ponderosa Juniperus scopulorum), and 150 on ponderosa pine sites. Graminoids comprised most of the forage on upland prairie sites (shallow, silty, clayey, and stony hills), and ponderosa pine sites. Bluestems (Andropogon spp.) were dominant on shallow and stony hills sites, while western wheatgrass (Agropyron smithii) and needlegrasses (Stipa spp.) were dominant on silty and clayey sites. Shrubs comprised substantial portions of the forage on the overflow and pine juniper sites. A prairie dog town, which was analyzed only during summer, had a seral plant community dominated by both forbs and grasses.
A total of 27,606 instances of plant use was recorded at 92 elk feeding sites from August 1976 to August 1977. Louisiana sagewort (Artemisia ludoviciana) was the major species eaten in winter, when forage use consisted of 52 percent forbs, 38 percent graminoids, and 9 percent browse. Threadleaf sedge (Carex filifolia) was the major species eaten in spring; total spring use consisted of 18 percent forbs, 74 percent graminoids, and 8 percent browse. Big bluestem (Andropogon gerardii) was the major species grazed in summer when total graminoid use was 87 percent; forbs comprised 5 percent and browse 8 percent of total summer plant use. Fall forage use consisted of 58 percent forbs (mostly Louisiana sagewort), 35 percent graminoids, and 7 percent browse. The major species used each season were all highly preferred. Browse use was generally low, but seemed to increase with snow cover. True mountain mahogany (Cercocarpus montanus), the major browse species in WCNP was in excellent condition. Results from rumen analysis were generally similar to that from feeding-site examination; seasonal percentage similarity between the two methods ranged from 56 to 58 percent. The major difference between feeding-site examinations and rumen analysis was the high amount of sweetclover (Melilotus spp.) in the rumens of elk that had fed along roadsides during summer. Cow groups and bull groups were similar in summer and winter food habits, but dissimilar in food habits during spring and fall.
Elk fed mostly on shallow and stony hills sites and used woodland sites as resting habitats, but feeding also occurred on pine-juniper sites during winter and early spring. Major habitats used by mule deer (Odocoileus hemionus) were shallow and woodland sites, although in fall extensive use was also made of overflow sites. Pronghorn (Antilocapra americana) used silty and other prairie sites throughout most of the year, but grazed extensively on stony hills sites in fall and winter. The silty site was the most important bison (Bison bison) habitat, while other sites important to bison were overflow, clayey, and stony hills sites. Bison and pronghorn were the ungulates most similar in habitat selection, but were least similar of all ungulates in spatial distribution. Mule deer were generally dissimilar from pronghorn and bison in habitat selection. The greatest potential for competition was found between elk and pronghorn, especially in fall and winter when both selected similar food and habitats. Habitat and spatial segregation between male and mixed groups (females, offspring, and immature males) was most distinct among elk.
Elk production was high in WCNP; the calf-cow ration in fall 1976 was 64:100 and in summer 1977 was 76:100. Elk were also found to be in good physical condition. Winter ticks (Dermacentor albipictus) and Sarcocystis sp. were the only parasites prevalent among elk. Two elk were positive for anaplasmosis and three for brucellosis out of 25 serum samples; none were positive for six other diseases, including 12 serotypes of leptospirosis.
It is recommended that utilization surveys be made on key species: Louisiana sagewort, big bluestem, threadleaf sedge, and true mountain mahogany. Prescribed burns may be useful to increase production of key forage species. Cow-calf herds and the bull population of elk in WCNP are distinct, and should be managed separately to prevent localized overuse of forage and minimize competition with other ungulates.