Yellowstone Wolf Project: Annual Report 2006

Smith, Douglas; Stahler, Daniel; Guernsey, Debra; Metz, Matthew; Nelson, Abigail; Albers, Erin; McIntyre, Richard

At the end of 2006, at least 136 wolves in 13 packs occupied Yellowstone National Park. This represents a 15% increase over 2005, when disease caused the largest population decline since reintroduction. Ten packs counted toward the breeding pair objective for the Yellowstone Recovery Area. One pack dissolved (Nez Perce) and one new pack formed (Oxbow Creek), marking one of the more stable years in pack turnover. Wolf distribution changed little. The population increase is probably a response to low wolf numbers in 2005 and greater pup survival (80% compared to 32% in 2005). Although blood serology is not available at the time of this report, there was no evidence of a disease outbreak in 2006. Mortality was about equal (18%) to the 10-year average (20%). Intraspecific mortality was again the leading cause of death. Average pack size was 10.5, and an average of 4.6 pups survived per pack. Twenty-six wolves were captured and collared. At year’s end, 37 of 136 (27%) wolves were collared. A new type of radio collar was deployed this year. The ARGOS collar is designed to track animals in remote locations that are hard to track via fixed-wing aircraft. These collars use satellite technology that can forward data to the wolf office via email. Wolf predation was affected by a winter of average snow accumulation but above average temperature. Deep snow and temperatures that often rose above freezing produced a crust on the snow and made it difficult for ungulates to access forage. Significant winterkill was documented for the first time since the severe winter of 1996–1997. Elk were in poorer condition (as measured by bone marrow) and kill rates were higher than in 2005. Wolf Project staff documented 281 kills (definite, probable, and possible combined) made by wolves in 2006, including 219 elk (80%), 30 bison (14%), 6 coyotes (2%), 5 wolves (2%), 3 deer (1%), 2 bighorn sheep (<1%), 2 moose (<1%), 1 beaver (<1%), 1 golden eagle (<1%), and 12 unknown prey (4%). The composition of elk kills was 32% calves (0–12 months), 31% bulls, 16% cows (1–9 years old), 14% old cows (≥10 years old), and 7% elk of unknown sex and/or age. Bison kills included 12 calves (unknown sex), 11 cows, 3 bulls, and 2 of unknown sex and age. Bison kills increased compared to the last two years, and on the northern range an early winter (November–December) switch to calves was evident after two years of selection for bull elk.

Yellowstone Wolf Project: Annual Report 2006

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