Dennis D. Austin

Effects of cattle grazing on mule deer diet and area selection.

Split enclosures, half grazed and half ungrnzed by cattle in summer, were compared for mule deer habitat use in late summer using tame deer. Diet composition, dietary nutrition, and area selected for grazing by mule deer were used PS criteria to assess the grazing effects of cattle. Generally few dietary or nutritional differences were determined. Nonetheless, deer preferred to forage on areas ungrnzed by livestock at low deer use levels, hut this preference rapidly decreased as deer use increased. Many reported studies have indicated proper livestock grazing maintains or improves habitat for mule deer (Odocoileus hemionus) (Smith 1949, Smith and Doe11 1968, Jensen et al. 1972, Longhurstetal. 1979,Smithetal. 1979,Neal 1981, Urness 1981, Rciner and Urness 1982, and others). In such management situations short-term direct effects~primarily competition for forage and habitat-may adversely affect mule deer. Although many studies have dealt with dietary overlap between livestock and mule deer (Hansen and Reid 1975, Hubbard and Hansen 1976, Hansen et al. 1977, Vavra and Sneva 1978. Campbell and Johnson 1983, and others). few have determined changes in mule deer foraging behavior and quantified the results. Previous study in this area (Austinand Urness 1985) determined forage production and plant variety were abundant in spring and early summer, and that forage selection by mule deer only became potentially restricted in late summer. Therefore the effects of livestock grazing on mule deer would also be expected to be most critical in late summer. Consequently it was the intent ofthis study to compare late summer diet and area preferences of mule deer on contiguous areas grazed and ungrazed by cattle.

Spring livestock grazing affects crested wheatgrass regrowth and winter use by mule deer.

Areas grazed and ungrazed by cattle in spring were compared for regrowth of crested wheatgrass on a big sagebrush-grass range. Overwinter utilization of crested wheatgrass by tame mule deer and their grazing area preferences were assessed under 3 snow cover conditions-snow free, partial, and complete. Results showed regrowth production was usually higher on areas previously ungrazed by livestock. Overwinter utilization of crested wheatgrass by deer was determined to be greater on ungrazed areas in both percentage of available grass used and weight per unit area consumed. Thus, interference from cured growth limiting green grass availability was more than compensated by increased production. The percentage of grass in the diet was generally higher on areas ungrazed by cattle, and deer preferred these areas under snow free and partial snow cover conditions; no preference was exhibited during complete snow cover. Recommendationsfor livestock grazing of seeded, foothill ranges where deer use is critical are discussed. Few winter rangelands are used exclusively by either domestic or wild ungulates, rather, use is usually sympatric, but not necessarily simultaneous. Critical foothill ranges used by mule deer (Odocoileus hemionus) in the winter are typically grazed by livestock during spring, fall or both. As demands for and values of wildlife recreation increase, managing these critical ranges primarily for wildlife habitat becomes monetarily and socially justifiable (Hendee 1974, Wennergren et al. 1977). The purpose of this study was to determine the influence of spring livestock grazing on a big sagebrush (Artemisia tridentata)crested wheatgrass (Agropyon desertorum) range on overwinter forage utilization and area choice by mule deer.

Alfalfa hay crop loss due to mule deer depredation.

To define alfalfa crop loss from depredating mule deer, the spotlight count and paired plot techniques were applied in 12 fields located throughout Utah. Protected and grazed plots were used to determine alfalfa loss. A significant relationship between deer-nights of grazing and alfalfa loss was determined. Based on our studies, we recommend using 2.4 kg/deer-night for mule deer depredation of alfalfa using the spotlight count assessment technique. Nutritional quality of alfalfa was not different between grazed and protected plots.

Impacts of mule deer and horse grazing on transplanted shrubs for revegetation

Revegetation success on foothill ranges in northern Utah using big sagebrush (Artemisia tridentata Nutt. spp. wyomingensis Beetle and Young) and rubber rabbitbrush brush (Chrysothamnus nauseosus Britt. spp. albicaulis H. and C.) was determined as influenced by winter mule deer browsing and spring horse grazing. Treatment areas of 0.1 ha with 3 replications included a protected control, use by deer only, use by horses only, use by deer and horses, and use by deer with horse grazing delayed for 3 years after seedling transplant. Results from the first 6 growing seasons following transplanting of seedlings showed grazing by horses only tripled the available, per-plant browse production of big sagebrush compared to protected plots, whereas browsing by deer only resulted in a 40% decrease in browse production. Seedling survival of big sagebrush differed between treatments during the first 3 growing seasons but was not affected by grazing after the third growing season. Rubber rabbitbrush was not affected by treatments.

Nutritional Value of Crested Wheatgrass for Wintering Mule Deer

The nutritional value of crested wheatgrass in the fall to spring diet of mule deer was determined from in vivo and in vitro digestibilities, a field graxing trial, and crude protein analyses. Its dietary significance was evaluated by comparing the known diet with and without the grass component. Findings indicated fall regrowth and spring growth of crested wheatgrass favorably affected the nutritional plane of mule deer on winter range dominated by big sagebrush having intermingled seedings of this exotic grass.

Vegetal change in the absence of livestock grazing, mountain brush zone, Utah.

Canopy cover of vegetrtion dominated by Cambel oak was determined in 1983 in adjacent canyons characterized by different grazing histories. Results were compared with data collected in 1935, and the methods replicated those used in the earlier study. Vegetal changes since 1935 in Red Butte Canyon where livestock grazing had been excluded since 1905 were small compared with those of Emigration Canyon where heavy graxing contfnued into the 1930’s, but was gradually phased out and discontinued in 1957. Large differences in vegetal cover between the 2 canyons reported in 1935 were mostly eiimhrated by 1983. Selective foraging by livestock is an important factor determining the composition of plant communities, and directly affects associated animal communities. Livestock select palatable forage and thereby give a growth advantage to less palatable, ungrazed plants. On many mule deer winter ranges in the Intermountain Region livestock grazing shifted presettlement, grassdominated communities to shrublands (Stewart 1941, Reynolds 1960, Christensen and Johnson 1964, Hull and Hull 1974, Harniss and Wright 1982). Mule deer herds responded to the increase in available winter forage and numbers significantly increased (Hancock 198 I). Authors are wildlife biologist, associate professor, and research assistant, Department of Range Science, UMC 52, Utah State University, Logan 84322. This oaoer is a contribution of Utah State Division of Wildlife Resources. Federal Aid Project W-105-R. Manuscript accepted 9 June 1986. However, due to erosion problems often associated with excessive livestock grazing and increased emphasis on watershed and recreation values, livestock grazing on many Intermountain winter ranges has been decreased or eliminated (Stewart 1936, Stoddart and Smith 1955). On those ranges where previously heavy livestock grazing was eliminated, secondary succession, accelerated by deer use in winter, would be expected to slowly alter plant communities toward more grasses and forbs and fewer desirable shrubs (Rogers 1982). Consequently reductions in numbers of mule deer may be predicted. The mountain brush zone found throughout the Intermountain Area commonly occurs as transition range between sagebrush foothills and coniferous forest. Open stands of deciduous trees, with abundant grass and forb understory having high nutritive value, make the zone valuable and attractive for grazing. Consequently many areas were highly impacted by livestock before grazing was curtailed. However, little is known about post-grazing succession. This study reports changes in vegetal composition from 2 areas previously grazed by livestock, but receiving no livestock use in several decades.

Values of four communities for mule deer on ranges with limited summer habitat.

Four plant communities were evaluated from May through September for mule deer dietary and nutritional values. The communities were dominated by Utah serviceberry, Gambel oak, big sagebrush, and mixed browse. In early summer deer diets contained many browse and forb species and were high in crude protein, but as summer progressed fewer species were selected and dietary crude protein declined, especially in the big sagebrush and serviceberry communities. Thus late summer was determined the critical period for forage quality. Range conditions were reflected by body size and condition of deer in fall. Little information is available on the value of various plant communities for mule deer where summer range is limiting and winter range is extensive. Furthermore, criteria are lacking for determining optimum deer densities on these summer ranges. Although the extent of winter range is more often the limiting factor for deer herds in the Intermountain Region, numerous herds have restrictive summer ranges, yet contribute substantially to the harvested resource. In Utah, a minimum of 9, and possibly 19, of 60 total deer units are limited by summer range; they contributed 9-22% of the total 1977-82 harvest. In this paper summer range is used as areas where deer are found in summer. However it should be recognized that the communities studied were far different from the lush mountain meadow, aspen, riparian, or conifer habitats commonly associated with mule deer summer range. In contrast the communities studied are warm and dry in summer and provide summer range mostly comprised of broad-leaved shrub communities that vary in composition. They are commonly considered as winter range for deer in areas where lush summer range is extensive, but they provide most of the

Response of curlleaf mountain mahogany to pruning treatments in northern Utah.

Production of curlknf mountain mahogany (Cercocarpus Iedifoliur) within browsing height of big game on winter ranges was increased 500-900% when 90-99% of the canopy was pruned from mature trees. However, since ndventitioussproutingdidnot occur, numerous live twigs must he present in the browsing zone before treatment for any practical benefit to accrue. Pruning at less than 90% canopy removal and girdling showed positive but smaller vegetative responses, while 100% canopy removal and application of pruning paint to wound surfaces in an attempt to eliminate sap flow had no effect on forage production available to big game. Improvement of the forage resource on big game winter range is one method to compensate partially for past and present reductions in habitat caused by human encroachment. Improvement can be via range restoration through reductions of competing low-value vegetation and reseeding, or improvement of existing, on-site conditions through intensified management. Methods found to increase the forage yield of desirable range plants become potential management tools (Plummer et al. 1968). Curlleaf mountain mahogany (Cercocarpus ledifolius) occurs throughout most of the Intermountain Area as part of the mountain brush zone. It is usually associated with true mountain mahogany (Cercocarpus montanus) at lower elevations and often grades into Douglas-fir (Pseudotsuga menziesii). When foliage is within the browsing reach of deer and elk, intensive utilization reduces available forage by shifting the competitive growth advantage to the upper unused portions. It has been shown to be high in nutritive value (Smith 1952; Bissell and Strong 1955), palatability (Smith 1950; Hoskins and Dalke 1955), digestibility (Smith 1957a), and dietary importance (Mitchell 1951; Smith and Hubbard 1954). Unfortunately, in many mature stands, most of the production is unavailable except through occasional snow or wind breakage of limbs. Thus a practical means of reducing canopy height while retaining productivity of these low trees could be highly beneficial to big game. Revegetation with curlleaf mountain mahogany is generally impractical because oflow seed viability(Younget al. 1978), poor seedling survival (Holmgren 1954) eve” with hand-planted nursery stock (Brown and Martinson 1959), and slow growth (Plummer et al. 1957). Likewise, bulldozing of mature trees has been unsuccessful due to high mortality (Dealy 197 I). Pruning has been found to stimulate vegetative growth in many shrubby species (Ferguson and Basil 1966; Plummer 1974), with variable success for curlleaf mountain mahogany (Smith 1957b; Phillips 1970); Thompson 1970). I” s”mmary, a successful methodology has not yet been defined, “or has the magnitude of change m available production been determined under various intensities and methods of treatment. These were the objectives of this study.