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Browsing by Author "Lehner, Philip N., committee member"

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    Ecology and behavior of the gemsbok at White Sands Missile Range, New Mexico
    (Colorado State University. Libraries, 1975) Saiz, Richard B., author; Decker, Eugene, advisor; Lehner, Philip N., committee member; Welch, Robert D., committee member
    The gemsbok (Oryx gazella) is a large desert dwelling antelope native to the Kalahari region of southern Africa. Fifty-one have been released at White Sands Missile Range, New Mexico, as part of the exotic mammal introduction program of the New Mexico Department of Game and Fish. The program's goal is to establish huntable populations of foreign big game in areas where conditions are unsuitable for native big game. Gemsbok numbers increased to an estimated population of 100 animals by the end of the field study. They occupied semi-desert shrub and grassland habitats. Foods consumed included mesquite bean pods, desert grasses, tumbleweeds, and yucca leaves. They displayed an amazing ability to survive with little or no drinking water. Gemsbok were not found to compete significantly with the native big game of White Sands Missile Range due to differences in habitat preferences. They are reproducing at a satisfactory rate, and show potential of becoming successfully established in New Mexico.
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    Ecology of desert bighorn sheep in Colorado
    (Colorado State University. Libraries, 1986) Creeden, Paul J., author; Cook, Robert S., advisor; Bailey, James A., committee member; Ellenberger, John H., committee member; Lehner, Philip N., committee member
    Desert bighorn sheep (Ovis canadensis nelsoni & mexicana) were transplanted into western Colorado in 1979, 1980 and 1981. The ecology of these sheep following transplanting was studied during 1982 and 1983. The population increased 18%, from 34 to 40 sheep, during this period. Minimum natality rates of 71% and 75% were observed. Survival of lambs born in 1982 to 1 year of age was at least 70%. Three of 4 suspected lamb losses occurred during the fall and winter months. Five adult mortalities were recorded. Two of these were predator related and occurred within the first few months of transplanting. Timing of reproductive activities was significantly delayed during the first year following transplanting. Ewes bred in Arizona and transplanted to Colorado in 1981 lambed significantly earlier in 1982 than they did in 1983 after breeding in Colorado. During 1982, ewes from the 1979 and 1980 transplants lambed significantly later than the ewes released in 1981. No significant differences in reproductive seasons were evident between transplant groups during 1983. Ewes preferred inner-canyon habitats for lambing. They most often selected ledges at the bases of sheer canyon walls and above steep talus slopes. All sites were located on escape terrain. A moderate degree of fidelity of ewes to lambing sites used in previous years was observed. The seclusion period of ewes during the lambing season varied with the social status of individual ewes. Dominant females remained alone for less time, both before and after parturition, than did subordinate females. Movements of ewes with lambs following parturition varied with the ewe's home range size. Long-distance moves were first recorded with 2-week old lambs. Dispersal of sheep following transplanting appeared to be influenced by winter weather conditions and by association with other bighorn. Both factors seemed to decrease movements. Dispersal patterns exhibited immediately following release influenced ultimate home range size. Sheep released in 1981 centered activities around the areas explored initially following transplanting. Overlapping home ranges were observed for both rams and ewes, p ranging in size from 4.6 to 44.7 km2. Home range sizes of ewes varied significantly among release groups and with habitat-use patterns. Coefficients of association were generally low in the herd. Bighorn ewes associated in direct proportion with the amount of range shared. Bighorn use of aspect differed between the winter-spring and summer periods. Use of inner-canyon habitats appeared to be related to canopy coverage of trees and shrubs.
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    The bighorn sheep of Battlement Mesa - a low elevation population
    (Colorado State University. Libraries, 1991) Cunningham, Mary Louise, author; Bailey, James A., advisor; Alldredge, A. William, committee member; Lehner, Philip N., committee member
    I studied bighorn sheep on Battlement Mesa, Colorado, from 12/88 to 7/90, to determine present and past herd status and distribution, so that 1) management options are clarified and 2) future management activities may be evaluated. I studied the herd by tracking 1 radio-collared ewe and obtaining visual observations and by systematically sampling study area units for sheep, sheep sign, potential competitors, potential predators and sheep carcasses. I recorded water sources that were encountered. I developed an historic perspective of the herd by searching agency files and local newspapers and interviewing local residents. The herd numbered up to 200-250 animals in the early 1900s and declined to an estimated 50 animals by 1970. Minimum herd sizes during 1989 and 1990 were 23 and 26, including lambs, respectively. Since 1961, the herd has abandoned approximately 56 km2 of historic range in the Mamm Peaks area. The herd decline corresponded with probable vegetation changes on Battlement Mesa, intensive livestock grazing through the 1950s, reports of poaching and an increasing elk herd. Sheep remained on the western portion of the range during winter and spring, 1989. Ewe/juvenile groups migrated to Anderson and Durant Gulches between 5/15-7/15/89 for lambing. Rams were more dispersed and in groups of 1-3, except during the rutting season. Ewe/juvenile group size ranged from 1-13. During dry months, (7/89, 8/89, 6/90) sheep concentrated in Anderson and Durant Gulches where a free-flowing spring and a seep were located. Bighorn sheep on Battlement Mesa appear limited by dense mountain shrub stands which separate all productive meadows from escape terrain and cover historic migration routes. A significantly greater use of the shale slope habitat contributed most to rejecting the null hypothesis that sheep use habitat types in proportion to their availabilities on Battlement Mesa. Sheep remained on shale slopes most (75% of all observations) of the time, using scattered grasses, forbs and shrubs for forage and seeps for water. Intensive and long term habitat management for bighorn sheep on Battlement Mesa is required. I suggest a 4-phase management program to improve existing range and later to reestablish and maintain historic migration corridors to productive historic summer range. Without management to improve existing conditions, this small, unique herd will remain static or decline.