Population Regulation Of The Jackson Elk Herd

Authors(s): B. L. Smith

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Publication Date: 0000-00-00

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Location: Laramie Wyoming

Abstract: From 1990-1992, 164 neonatal elk (Cervus elaphus) calves were captured and radio-collared in Grand Teton National Park (GTNP) and the Bridger-Teton National Forest (BTNF) of northwest Wyoming. The elk were monitored with radio-telemetry through April 1994 to evaluate seasonal distributions and survival, causes of mortality, juvenile dispersal, and relationship of harvest to migratory patterns. The overall objective was to determine any significant differences in regulation of the relatively high densities of elk in GTNP and the elk that summered in the other three segments of the Jackson elk herd. Densities of elk on calving areas (GTNP and BTNF) did not affect mortality rates of neonates. However, more males were born on BTNF than in GTNP; and neonatal mortality was male biased due to predation, primarily by black bears (Ursus americanus). Annual survival rates of both calves and elk >= 1-year-old were higher among females than males, but survival was unrelated to the ranges on which elk summered. Recruitment rates, as measured by mid-summer calf:cow ratios, also did not differ between GTNP and the other summer ranges. Twenty-three percent of yearlings and 2-year-olds dispersed among the herd segments. Dispersal into GTNP, which was male biased, exceeded the rate of dispersal out of GTNP, which was female biased. However, hunting significantly altered the role that dispersal played in regulating herd segments, resulting in no difference in the net rates of dispersal into and out of GTNP. Timing of fall migrations were correlated with 10 November snow depths and annual forage production. Mean annual arrival of the GTNP herd segment at winter range preceded arrival of the other herd segments by 11-29 days each fall. The absence of differences in the causes of mortality and rates of survival, recruitment, and dispersal suggests that the number of elk occupying GTNP and the other three herd segments were regulated similarly. Winter food supplementation and human predation of elk likely limit resource competition and contribute to this situation.

Keywords: Wyoming Cooperative Fish and Wildlife Research Unit, University of Wyoming, animal, mammal, ungulate, Jackson Hole, Teton County, elk, Cervidae, wapiti, Cervus Elaphus, radio collar, mortality, migration, hunting, human activity, Grand Teton National Park, Bridger-Teton National Forest, National Elk Refuge, predation, bear, Ursidae, black bear, Ursus americanus, winter food supplementation, forage, population, habitat, food, feeding, management