Selection of Northern Yellowstone Elk by Gray Wolves and Hunters

Abstract

We compared selection of northern Yellowstone elk (Cervus elaphus) by hunters in the Gardiner Late Hunt and northern Yellowstone wolves (Canis lupus) with regard to sex, age, and impacts to recruitment. We compared harvest data from 1996–2001 with wolf‐killed elk data from 1995–2001. We assessed the effects of hunting and wolf predation on reproductive female elk by constructing a life table and calculating reproductive values for females in the northern Yellowstone herd. We devised an index of total reproductive impact to measure impacts to calf production due to hunting and wolf predation. The age classes of female elk selected by wolves and hunters were significantly different. Hunters selected a large proportion of female elk with the greatest reproductive values, whereas wolves selected a large proportion of elk calves and older females with low reproductive values. The mean age of adult females killed by hunters throughout the study period was 6.5 years, whereas the mean age of adult females killed by wolves was 13.9 years. Hunting exerted a greater total reproductive impact on the herd than wolf predation. The combined effects of hunters killing prime‐aged females (2–9 yr old), wolves killing calves, and predation by other predators has the potential to limit the elk population in the future. Yellowstone is unique in this regard because multiple predators that occur sympatrically, including hunters, wolves, grizzly bears (Ursus arctos), black bears (Ursus americanus), cougars (Felis concolor), and coyotes (Canis latrans), all prey on elk. Using an Adaptive Harvest Management process the known female elk harvest during the Gardiner Late Hunt has been reduced by 72% from 2,221 elk in 1997 to 620 elk in 2004. In the future, hunting harvest levels may be reduced further to partially offset elk losses to wolves, other predators, and environmental factors.

Factors Influencing Survival of Female Elk in a Harvested Population

“…We found a weak negative relationship between age and survival, which was consistent with age-specific variation in survival found in other ungulate populations (Loison et al 1999;Gaillard et al 2000;Festa-Bianchet et al 2003). A negative relationship between survival and age in the Fort Riley population could be due to hunters avoiding harvesting a calf or yearling, and thereby increasing the mortality risk for adult female elk in older age-classes (Wright et al 2006). The average age at harvest for female elk at Fort Riley ( x x = 6.9 y) was within what has been defined as the prime-age life stage for elk (2-9 y; Raithel et al 2007), and is similar to the average age of elk harvested from a population in Idaho ( x x = 7.3 y; Husseman et al 2003).…”

“…As the primary source of mortality, hunting is expected to directly influence adult survival rates, which may subsequently influence the overall rate of population growth (l). Harvest may have a particularly strong influence on population dynamics if prime-age classes are selectively harvested (Wright et al 2006).…”

Space use and social ecology of coyotes (Canis latrans) in a high-elevation ecosystem: relative stability in a changing environment

“…Associated trophic cascades have been documented, including recovery of riparian vegetation (Beyer et al 2007) and aspen (Ripple and Beschta 2007). The greater reproductive impact of cow elk hunting relative to wolf predation (Wright et al 2006) suggested adjusting hunting pressure was a more powerful management tool than predation for regulating elk population size. Whether coyotes on our study area are capable of filling a similar niche to wolves in Yellowstone is doubtful.…”

Female mate choice based upon male motor performance

“…The elaborate stotting that prey such as Thomson's gazelles, Gazella thomsoni, perform at the beginning of a predator attack suggests that the predators are capable of detecting slight differences in the motor performance of prey (FitzGibbon & Fanshawe 1988). It is also well known that predators efficiently identify weak, injured or sick prey (Mills, 1990;Quinn and Cresswell, 2004;Martin et al, 2006;Wright et al, 2006). In summary, natural selection on predators has probably enhanced animals' ability to detect subtle differences in the motor performance of potential prey.…”