Juvenile survival and population regulation of the Jackson elk herd
Smith, B.L.; Anderson, S.H.
Journal of Wildlife Management 62(3): 1036-1045
Elk (Cervus elaphus nelsoni) that summer in Grand Teton National Park (GTNP) are part of the migratory Jackson Elk Herd. They are fed in winter on the National Elk Refuge (NER) and have been hunted in portions of GTNP since 1950 to control population size. However, the number of elk in the Jackson Elk Herd has grown from about 8,000 in 1984 to >16,000 in 1997. We captured and radiocollared 164 newborn calves during 1990-92 to quantify juvenile mortality and its role in regulating the Jackson Elk Herd. Elk captured in GTNP (5.9 elk/km2 ) and on adjacent national forest lands of lower elk densities (2.4 elk/km2) Were radiomonitored through May 1994. Mortality of calves was similar during summer (15.2%), fall (15.3%), and winter (16.5%) 1990-92. Most deaths resulted from predation, hunting, and winter mortality associated with increased precipitation, duration of winter, and epizootic disease. Survival of calves supplementally fed in winter exceeded survival of calves not fed (P = 0.039). All but 1 of 16 deaths of elk gtoreq 1 year old (n = 122) resulted from hunting. Early-born calves experienced higher winter survival (P = 0.02) than late-born calves. Annual calf survival (x = 0.579) was inversely related to birth date (P < 0.01) and winter precipitation (P = 0.05). Annual survival of female calves (x = 0.662) exceeded survival of males (x = 0.502; P = 0.049). Survival of juvenile elk born and summering in GTNP did not differ seasonally or annually from survival of juveniles outside the park (P > 0.47). Because much of the variation in juvenile survival was density independent, we recommend management that reduces the dependence of elk on supplemental feed and increases harvests of female elk.