Population Analysis of a Northern Utah Elk Herd

Abstract

Population changes from 1951 to 1972 in the Cache elk (Cervus canadensis) herd are discussed, based on analyses of aerial trend counts, productivity estimates, hunting pressure trends, harvest figures, and tagging data. Population changes during the study period could be correlated with levels of female harvest. Mortality rates, derived from analysis of tag recoveries from 1951 to 1960 were 0.42 and 0.36 for males and females, respectively. Female recruitment for the same period averaged 28 calves per 100 cows. The disparity between recruitment and mortality resulted in a population decline of approximately 8 percent per year from 1959 to 1966. Curtailment of female harvest (1966-68) effected a reversal of this decline, the population increasing at approximately 15 percent annually during the initial recovery phase. Following initiation of unlimited bull hunting (1968) the rate of population growth dropped to approximately 3 percent. Various contributory components of the female mortality rate are estimated to interpret the observed differential rates of population change. Estimated rates of hunting and other mortality for females during the period 1951-60 are 0.16 and 0.24, respectively. Observed and predicted initial effects of unlimited bull hunting and various levels of female harvest are also discussed as guidelines in future management. J. WILDL. MANAGE. 38(2):761-174 The primary objectives of early elk management programs in Utah were the protection of elk populations and removal of nuisance animals (Olsen 1943). As elk populations prospered under this protection, accompanied by increasing demands on the resource, the need for a more refined management program developed. In an effort to gain more knowledge about these expanding populations, the Utah Division of Wildlife Resources complemented its regular management program with periodic research projects (McCormack 1951, Hancock 1955, King and Muir 1971, Follis 1972). The history of the Cache elk herd, as described by McCormack (1951) and Hancock (1955), generally parallels a pattern found throughout the West. Following settlement of the area, the native elk population declined rapidly, until by the late 1800's it was virtually eliminated. Between 1911 and 1917 elk were reintroduced with the aid of local sportsmen's organizations. The first subsequent elk hunt was authorized in 1925 primarily to control nuisance animals; since 1931 elk hunts have been held annually. Early hunts were restricted to bull-only permits, but from 1935 through 1967 antlerless or either-sex permits were also issued. Hunting pressure prior to 1968 was limited by the number of permits authorize . Since 1968, however, the unit has been open to unlimited hunting with limited either-sex permits offered for specific problem areas only. With the advent of open-bull seasons, hunter participa ion more than tripled. Watershed management and range protection, competition with deer (Odocoileus hemionus) and livestock, loss of winter and summer range to suburban development, and increasing recreational demands also augmented pressures on the elk herd and intensified the need for better understanding of the population. In this paper, we have attempted to integrate annual survey data with the results of specific studies cited above and tagging data into a general population analysis of the Cache elk herd. The analysis should provide insights into the following aspects of our management program: (1) the effect on the population of the increased bull J. Wildl. Manage. 38(2):1974 161 This content downloaded from 157.55.39.45 on Thu, 01 Sep 2016 05:40:21 UTC All use subject to http://about.jstor.org/terms 162 ELK POPULATION ANALYSIS * Kimball and Wolfe TA7AH BEAR WINTER RANGE