Yellowstone Wolf Project: Annual Report 2005

Smith, Douglas; Stahler, Daniel; Guernsey, Debra

At the end of 2005, at least 118 wolves in 13 packs occupied Yellowstone National Park (YNP). This represents a decline of 51 wolves (a drop of 30%) from 2004, the largest population decline since reintroduction. Seven packs counted toward the breeding pair objective for the Yellowstone Recovery Area. Four packs dissolved or left the park: Geode Creek and Specimen Ridge packs no longer exist, the Biscuit Basin pack moved into Idaho, and the Chief Joseph pack is now counted as a state of Montana pack (other than denning in the park, movements are all outside YNP). One new pack (Hellroaring Creek) formed when the Leopold pack split and some members occupied old Geode Creek territory. The decline in 2005 is largely attributed to poor pup survival. Disease is suspected as the cause but laboratory tests are still pending. At least 69 pups were born and 22 (32%) survived. Pup survival is typically greater than 60%. Pup survival was poorest on the northern range, where only 8 of 49 (16%) survived. Three packs (Druid Peak, Nez Perce, Swan Lake) had no pups survive and one pack (Mollie’s) did not produce pups. Slough Creek and Leopold packs each had multiple breeding females. The 10 packs that produced litters had an average of 6.9 pups (range 1–19, including packs with multiple breeders), and an average of 2.2 pups per pack survived (range 0–5). Thirty-six wolves were captured and collared. At year’s end, 39 of 118 (33%) were radio collared. Global Positioning System (GPS) collars were deployed but, as in past years, transmitter failure continued to plague data gathering. Wolf predation was monitored year round with intensive study periods during early and late winter, and May through August. Wolf Project staff documented 316 kills (definite, probable, and possible combined) made by wolves in 2005, including 244 elk (77%), 29 bison (9%), 9 wolves (3%), 6 deer (2%), 4 moose (1%), 4 coyotes (1%), 2 skunks (1%), 2 ravens (1%), 1 pronghorn (less than 1%), 1 badger (less than 1%), and 14 unknown prey (4%). The composition of elk kills was 18% calves (0–12 months), 11% cows (1–9 years old), 12% older cows (≥10 years old), 43% bulls, and 16% elk of unknown sex and/or age. The increase in the percentage of bull elk killed in 2005 refl ects a change in prey selection and kill rates. Bison kills included 9 calves (unknown sex), 10 cows, 6 bulls, and 4 of unknown sex and age. During winter, some interior packs (Mollie’s and Hayden Valley) fed entirely on bison. Studies continued on scavenger use of wolf-killed prey, and expanded to include the collection of invertebrates at wolf kills. Den closures and other wolf management activities continued and increased. The Slough Creek pack denned within view of the road and attracted large crowds of visitors. The Hayden Valley pack was often observed and caused many “wolf jams.” Wolf Project staff published 5 peer-reviewed journal articles, 2 book chapters, 2 popular articles, 2 technical reports, and 1 book. Additional information on wolves in Yellowstone National Park is available.

Yellowstone Wolf Project: Annual Report 2005

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