Great Basin Naturalist Volume 47 Number 4 Article 24 10-31-1987 Winter habitat-use pattern of elk, mule deer, and moose in southwestern Wyoming Olin O. Oedekoven University of Wyoming, Laramie Fredrick G. Lindzey University of Wyoming, Laramie Follow this and additional works at: https://scholarsarchive.byu.edu/gbn Recommended Citation Oedekoven, Olin O. and Lindzey, Fredrick G. (1987) "Winter habitat-use pattern of elk, mule deer, and moose in southwestern Wyoming," Great Basin Naturalist: Vol. 47 : No. 4, Article 24. Available at: https://scholarsarchive.byu.edu/gbn/vol47/iss4/24 This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact scholarsarchive@byu.edu, ellen_amatangelo@byu.edu.
WINTER HABITAT-USE PATTERNS OF ELK, MULE DEER, AND MOOSE IN SOUTHWESTERN WYOMING Olin O. Oedekoven'^and Fredrick G. Lindzey' Abstract. Habitat-use patterns of mule deer, elk, and moose were determined on two winter ranges near Kemmerer, Wyoming. Mule deer used areas with the least snow depth and dominated by sagebrush. Elk were located more often than expected on wind-swept hills but used sagebrush communities more frequently as snow depths increased. Moose were generally found associated with broad, riparian zones. All three species occasionally used the same area but differed in their use of specific vegetation types and topography. Many winter ranges in the Rocky Mountains are used by two big game species, but few ranges support three or more species of large ungulates. Nelson (1981) suggested that although mule deer (Odocoileus hemionus) and elk (Cervis elaphus) often share winter ranges, these species compete for forage only during extreme environmental conditions. His conclusions were based on the differing foraging strategies of mule deer and elk; elk selected mostly grasses, while mule deer preferred browse species. Elk and moose {Alces alces) relationships on winter ranges were evaluated by Stevens (1974), Nelson (1981), and Rounds (1981). These authors concluded that because elk and moose occupied unique habitats and exhibited differing diets, they were not usually competitors. Moose and elk appear to fill two discrete ecological niches with respect to range, food habitats, physical characteristics, and social organization. The purpose of this study was to document the winter distribution of three ungulate species on two adjacent winter ranges and to identify habitat characteristics associated with the distribution of each species. Study Areas The study included a majority of two large, adjacent big game winter range complexes in southwestern Wyoming (Wyoming Game and Fish Department, unpublished files 1983). The two winter ranges are separated by highelevation mountains (3,500 m) that receive little or no use by ungulates during midwinter. The combined 1985 population estimates for these areas were 20,000 mule deer, 2,700 elk, and 1,000 moose (Wyoming Game and Fish Department, unpublished files 1985). The western wintering area is about 15 km wide by 32 km long, and the eastern area is 28 by 46 km. Drainages generally flow from the north to south and east to west within the western area and west to east within the eastern area. Western exposures dominate the western portion and eastern exposures the eastern area. Elevations vary from 2,800 m to 1,800 m. Annual precipitation ranges from 25 to 35 cm, gradually shifting to less than 25 cm in the more xeric eastern portions of the winter range. Average growing season is 60-90 days (Bureau of Land Management, Kemmerer Resource Area, unpublished files). Sagebrush {Artemisia spp.) rangeland (Lanka et al. 1983) characterizes the majority of both winter ranges. This shrub vegetation type is composed of big sagebrush (A. tridentata), with lesser amounts of black sagebrush (A. nova), saltbushes {Atriplex spp.), and black greasewood {Sarcobatus vermiculatus). Mixed-shrub communities are found on more mesic sites. This community is dominated by Utah serviceberry {Aynelanchier utahensis), western snowberry {Symphoricarpos occidentalis), and antelope bitterbrush {Pursha tridentata). Quaking aspen {Populus tremuloides)slre present in small (< 0.5 ha) stands at higher elevations. Willow (Salix spp.) and grass meadows dominate the larger river bottoms. Pockets of mixed conifers dominated by Engelmann spruce {Picea engehnannii) and University of Wyoming Cooperative Fish and Wildlife Research Unit, Box 3166 University Station, Laramie, Wyoming 82071. ^Present address: Wyoming Game and Fish Department, 2800 Pheasant Drive, Casper, Wyoming 82604. 638
October 1987 Oedekoven, Lindzey: Winter Habitat in Wyoming 639 subalpine fir on the steep, usually northern exposures of {Abies hisiocarpa) are common the higher-elevation ridgelines. An extensive stand of curl-leaf mountain mahogany {Cercocarpus ledifolius) is present on the northwestern portion of the western winter range. Juniper (Juniperus spp.) stands are infrequent and limited to small (< 0.25 ha) pockets. Higher ridges that are devoid of shrubs are generally vegetated by mosses, lichens, and warm-season grasses (Poaceae). Most of the land in both winter ranges is administered by the Bureau of Land Management or the State of Wyoming. Principle land uses include grazing by cattle and domestic sheep and energy exploration and extraction. Methods Aerial Surveys Flights w^ere conducted over the winter ranges during December and January of each year. A highly modified Maule N5AR singleengine, fixed-wing aircraft (Stockhill 1986) was used to fly 0.9-km-wide, established transects. Transects were located to provide complete and consistent coverage of the winter range. Animal locations were recorded on an onboard computer interfaced with an area navigational system. Locations were recorded in precise latitude and longitude coordinates as the aircraft flew over each animal group (one or more animals). This navigational system also allowed the same predetermined transects to be flown each month. Data Collection Vegetation type, topography, exposure, snow depth, snow cover, and animal activity were recorded for each observation. Vegetation-type categories included sage-grass, mixed shrub, aspen, willow, mountain mahogany, mixed conifer, alpine grass, and agricultural areas. Topographic categories were: drainage (draws, ditches, and narrow canyons), flat (less than 5% slope), toeslope (slope base to 30 m up a slope), steep (20-h% slope), ridgeline, and hilltop. Exposure categories were one of the eight cardinal directions. Snow conditions were estimated for the area occupied by an animal group and included snow depth and percent snow cover. Estimates of snow depth were subjective and based on height of plants and animals. Estimates of availability of the various vegetative communities, topographic, and snowcondition categories were obtained by making observations at intervals of three nautical miles during aerial surveys. Data were recorded for the availability site (about 50 x 50 m) in the same manner as that used when animals were observed. Characteristics of sites where animals were observed were compared to estimates of availability using Chisquare tests of independence (Khazanie 1979) with the Mine Tab computer program (Ryan et al. 1985). Spatial overlap of species was examined by simply comparing counts of species present in 1.6-km" grids. These grids were positioned on section, range, and township boundaries. Evaluation of Potential Sampling Biases Making inferences from observation data about dispersion or habitat-use patterns requires that several assumptions regarding animal detectability be met. Animals should be equally or proportionately detectable throughout the sampled area (species and individuals). To evaluate the possibility that deer, elk, and moose were more easily detected from the airplane when standing or bedded or in specific vegetation types, we conducted surveys on the ground after each flight. We located animals by searching with a truck or snowmobile or driving to areas where they had been observed from the airplane. Once we located an animal or group of animals, we visited them periodically through the day and noted the activity (standing or bedded) and habitat type for each animal. Observations were not begun for at least 0.5 hr after the group was first located to minimize the possibility that they were located because of their activity or the vegetation type in which they were initially found. Results of ground surveys were compared with results of the airplane transects to identify differences that would suggest differential detectability. Additionally, we searched areas on the ground for animals and their sign where no animal had been observed from the air. On five occasions we walked or drove through dense vegetation types (i.e., sagebrush draws, mountain brush stands) and attempted to count the animals present for comparison with counts made from the air.
640 Great Basin Naturalist Vol. 47, No. 4 Table 1. Mule deer, elk, and moose observed during aerial transects and ground surveys in southwestern Wyoming, 1984-1986.
October 1987 Oedekoven, Lindzey; Winter Habitat in Wyoming 641 Table 3. Percent of mule deer, elk, and moose observations in the various topographic categories during the winters of 1984-85 and 1985-86 and estimates of availahihty as determined from monthly aerial sampling.
642 Great Basin Naturalist Vol. 47, No. 4 Table 5. Percent of mule deer, elk, and moose observations in the various snow-condition categories during the winters of 1984-85 and 1985-86 and estimates of availability as determined from monthly aerial sampling.
B D O October 1987 Oedekoven, Lindzey: Winter Habitat in Wyoming 643 dery, allowing fairly unrestricted movement by moose. Our results suggested that although deer, elk, and moose often used the same areas, they selected differing habitats within shared areas. These patterns might be expected to change with deeper snow as suggested by CliflF (1939). The greatest spatial overlap of elk and mule deer occurred during January of the first winter and December of the second, the months with the greatest snow depths (Table 2). Because of the dominant use and availability of the sagebrush vegetation type, slightly underestimating deer use of mixed-shrub vegetation from the airplane would not demonstrably alter the results presented. Acknowledgments We would like to express our gratitude for the cooperative efforts of the Wyoming Game and Fish Department, the Bureau of Land Management, and the University of Wyoming. E. Raper was instrumental in the success of the project. Funding for the project was provided by the Wyoming Game and Fish Department, and it was conducted under the auspices of the Wyoming Cooperative Fishery and Wildlife Research Unit. Literature Cited Beall, R C 1974. Winter habitat selection and use by a western Montana elk herd. Unpubhshed dissertation, University of Montana, Missoula. 197 pp. Cliff, E P 1939. Relationship between elk and mule deer in the Blue Mountains of Oregon. Trans. N. Amer. Wildl. Conf. 4: 560-,569. COADY. J W. 1974. Influence of snow on behavior of moose. Nat. Canadienne 101: 417-436. Gilbert, P F, C Wallmo, and R B Gill 1970. Effect of snow depth on mule deer in Middle Park, Colorado. J. Wildl. Manage..34(1); 15-23. Kelsall, J P 1969. Structural adaptations of moose and deer for snow. J. Mammal. 50(2): 302-310. Khazanie, R 1979. Elementary statistics in a world of applications. Good Year Publ. Co., Santa Monica, California. 488 pp. Lanka, R P, B. Inkley, and S H Anderson 1983. Wyoming and Montana land cover classification and mapping project. Final Rept., U.S. Dept. Inter., Fish and Wildl. Serv., Wyoming Fish and Wildl. Coop. Res. Unit, Laramie. 33 pp., 2 maps. LeResche, R E, and R A Rausch. 1974. Accuracy and precision of aerial moose censusing. J. Wildl. Manage. 38(2): 175-182. Nelson, J R 1981. Relationships of elk and other large herbivores. Pages 415-441 in J. W. Thomas and D. E. Toweill, eds.. Elk of North America: ecology and management. Stackpole Books, Harrisburg, Pennsylvania. 698 pp. Nelson,] R.andT A Leege, 1981. Nutritional requirements and food habits. Pages 323-367 in J. W. Thomas and D. E. Toweill, eds.. Elk of North America: ecology and management. Stackpole Books, Harrisburg, Pennsylvania. 698 pp. Peek, J M 1974. On the nature of winter habitats of Shiras moose. Nat. Canadienne 101: 131-141. Rounds, R. C 1981. First approximation of habitat selectivity of ungulates on extensive winter ranges. J. Wildl. Manage. 45(1): 187-196. Ryan, B F, L Joiner, andt A Ryan, Jr 1985. Minitab handbook. Sec. Rd. Dusbury Press, Boston. 374 pp. Smith, J, G 1952. Food habits of mule deer in Utah. J. Wildl. Manage. 16(2): 148-155. Springer, L. M 1950. Aerial census ofinterstate antelope herds of California, Idaho, Nevada, and Oregon. J. Wildl. Manage. 14(3): 295-298. Stevens, D. R 1974. Rocky Mountain elk-shiras moose range relationships. Nat. Canadienne 101(4): 505-516. Stockhill, M E 1986. The making of a microchip Maule. Aero (10): 18-25. Wilkins, B T 19.57. Range use, food habits, and agricultural relationships of the mule deer, Bridger Mountains, Montana. J. Wildl. Manage. 21(2): 1,59-169.