Yellowstone Wolf Project: Annual Report 2008

Smith, Douglas; Stahler, Daniel; Albers, Erin; Metz, Matthew; Williamson, Libby; Ehlers, Nick; Cassidy, Kira; Irving, Joshua; Raymond, Rebecca; Almberg, Emily; McIntyre, Richard

At the end of 2008, at least 124 wolves in 12 packs and various groups occupied Yellowstone National Park. This is one more pack than in 2007, but several long-term, stable packs were replaced by smaller, newly formed packs. This represents a 27% decline from 171 wolves in 2007, similar to the decline in 2005 (from 171 to 118 wolves). Six packs counted toward the breeding pair objective for the Greater Yellowstone Wolf Recovery Area, the fewest since wolves first reached the minimum requirement for delisting in 2000 (30 breeding pairs in Idaho, Montana, and Wyoming). High mortality of both pups and adults caused by disease and intraspecific mortality were the primary factors in the population decline and low breeding pair count. Both the Leopold pack, one of the most stable in the park since 1996, and the Oxbow Creek pack, an offshoot of Leopold that formed in 2005, dissolved in 2008, and the Hayden Valley pack dispersed as a pack from the park. The status of two other previously stable packs, Agate Creek and Slough Creek, was in question at year end. Both packs had lost members and neither pack had radio collars. The Druid Peak pack remained relatively intact. Interior packs were more stable than northern range packs. The radio-collared wolf that had immigrated from Idaho into the park in 2007 and continues to be vitally important for genetic connectivity between recovery areas, left the park in mid-2008 and settled to the east in the Crandall Creek area. Pack size ranged from 4 to 25 and averaged 9.3 wolves, which was smaller than the long-term average of 10. Average number of pups per pack in early winter was 1.8. Reproduction was poor in 2008 and only 29% of the pups survived the summer. Quadrant Mountain and Cougar Creek packs had no evidence of pups; most other packs had pups but few or none survived. As in 1999 and 2005, the probable cause of poor pup survival was disease, likely distemper, although definitive evidence will not be available until blood samples from 2009 are analyzed. As in previous years, the leading cause of mortality (59%) among collared wolves was intraspecific strife (10 out of 17 deaths). Two of the other deaths were the second and third known malnutrition fatalities since reintroduction. The deaths included 12 females and 5 males: 5 yearlings, 10 wolves age 2–5, and 2 wolves over age 5. Twenty-eight wolves from 10 packs were captured: 17 females and 11 males, 16 pups, 5 wolves age 2–5, and 1 wolf over age 5. At year end, 32 of 124 (26%) wolves were collared with either VHF or Global Positioning System (GPS) radio collars. Placement of collars was dependent on monitoring objectives, but VHF radio collars are still the most commonly used in the park. Wolf Project staff detected 576 definite, probable, or possible kills by wolves in 2008: 463 elk (80%), 23 bison (4%), 19 deer (3%), 13 coyotes (2%), 11 wolves (2%), 5 pronghorn (<1%), 3 moose (<1%), 3 grouse (<1%), 2 bighorn sheep (<1%), 2 ravens (<1%), and one each of beaver, golden eagle, grizzly bear, cougar, red fox, and otter, and 26 unknown prey (5%). The composition of elk kills was 32% bulls, 27% calves (0–12 months), 16% cows age 1–9, 15% cows over age 10, and 10% elk of unknown sex and/or age. Bison kills included 4 calves, 3 cows, 7 bulls, and 9 adults of unknown sex.

Yellowstone Wolf Project: Annual Report 2008

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