How wolves affect elk herds
Posted on 09 March 2009
The long-term counts of northern Yellowstone elk indicates the elk population has decreased 60 percent since wolf reintroduction.
The Northern Yellowstone Cooperative Wildlife Working Group conducted its annual aerial survey of the northern Yellowstone elk population in January and February, and revealed a total of 7,109 elk. Approximately half of the elk were located within Yellowstone National Park, and one-half were located north of the park. The northern Yellowstone elk herd winters between the northeast entrance of Yellowstone National Park and Dome Mountain/Dailey Lake in the Paradise Valley. This year’s count was slightly higher than the counts during the three previous winters (6,279 -6,738 elk), but lower than the 9,545 elk counted in winter 2005.
The slight increase in elk counted during winter 2009 compared to the three previous winters “may reflect favorable counting conditions, a reduction in the hunter harvest of antler-less elk, and a reduction in wolf predation owing to a fairly large decrease in wolfnumbers during the summer of 2008” according to P.J. White, biologist for Yellowstone National Park. Wolf numbers on the portion of the northern range inside the park decreased by 40%, from 94 to 56 wolves, during 2008.
Predation by wolves and other large carnivores, human harvests of antler-less elk during the Gardiner Late Hunt and drought effects on maternal condition and recruitment were indicated as the primary factors contributing to this decreasing trend during 1995-2005. However, the Montana Department of Fish, Wildlife, and Parks decreased the number of antler-less elk permits from 1,102 in 2005 to 100 per season during 2006-2009 owing to decreases in elk abundance and recruitment. This adjustment of permits was intended to increase the number of prime-aged females in the population which, in turn, should increase the recruitment rates of calves into the breeding population.
Collaborative analyses by the Montana Department of Fish, Wildlife, and Parks, Montana State University, and the National Park Service suggest elk numbers have decreased in areas where combined high numbers of wolves and grizzly bears occurred in relation to numbers of elk, while elk populations remained stable or increased where consistently low numbers of wolves and/or grizzly bears coexisted with elk and moderate levels of hunter harvest occurred. Also, elk calf recruitment is generally lower in areas where the ratio of predators to prey is higher.
Tom Lemke, biologist for Montana Fish, Wildlife and Parks, also cautioned that even though biologists counted 830 more elk than last year, it is unlikely “we will see any significant long-term increase in elk numbers until there is long-term improvement in elk calf recruitment rates.”
Last year’s recruitment rate was 11 calves per 100 cows. Elk recruitment objectives for this population are 20-30 calves per 100 cows. Poor recruitment rates over the last number of years are largely attributable to high predation rates — wolves, lions and bears.
Montana’s state elk management plan calls for a wintering population objective of 3,000 to 5,000 elk north of Yellowstone National Park, with 2,000-3,000 of those animals wintering on or near the state-owned Dome Mountain Wildlife Management Area. This year biologists counted 3,511 elk north of the park with 2,896 of those elk wintering in the Dome Mountain area, according to Lemke. In fact, elk survey numbers have been within population objectives for about the last seven years. In contrast, during the last five years of the 1990’s, 5,300-8,600 elk wintered north of the park with 3,500-4,500 elk in the Dome Mountain area. Wintering such large numbers of elk could lead to long-term habitat decline and increase the likelihood of game damage on private lands. •