Yellowstone Wolf Project: Annual Report 2003

Smith, Douglas; Stahler, Daniel; Guernsey, Debra

At the end of 2003, at least 174 wolves (13–14 packs, 2 groups of wolves of undefined status, and 2 loners) had some portion of their territory within Yellowstone National Park (YNP). Thirteen packs were considered “breeding pairs”—a pair with at least two pups-of-the-year that survive until December 31, according to the USFWS definition under the criteria for delisting the wolf as an endangered species in the Rocky Mountain recovery area. The goal of 30 breeding pairs with an equitable distribution throughout the three recovery areas for three successive years was achieved in 2002. With the biological criteria met, the states of Idaho, Montana, and Wyoming must complete approved management plans to ensure adequate wolf populations in the future. When state plans are approved, the USFWS will delist wolves in this area. As of this writing, Idaho’s and Montana’s plans have been approved. The discrepancy in total packs pertains to uncertainty about the Buffalo Fork pack. The only radio-collared individual in this pack died in May, after the pack had denned. Since there were no radio-collared wolves to track for the rest of the year, the status of this pack is unknown, but we believe it exists. Seven packs and one group reside in the northern portion of the park, and seven packs and one group live in the park interior. Pack sizes ranged from 2 (#302M group) to 20 (Swan Lake pack) and averaged 10.8. The increase in the population from 2002 to 2003 was mostly due to increases in pack sizes and not to the establishment of new packs. One new pack formed in 2003, but one also dissolved. At least 75 pups were born, and 59 (79%) survived to year end. Average litter size was five. Sixteen wolves were known to have died in YNP, one possibly to disease. Mange, although recorded in wolves around the park, has not been documented inside YNP. We had our best radio-collaring year so far, with 38 wolves captured and handled. Capture efforts began in November 2003, the earliest start date yet, which was the primary reason that greater success was achieved. At year end, all but one pack in the park was collared, and 53 (30%) of 174 YNP wolves wore radio collars. Both our early and late winter studies took place again, and a paper in the Journal of Wildlife Management summarized the results of the first five years of this work. In winter, wolf predation was still focused primarily on elk. The species composition of prey was 83% elk, 6% bison, 2% moose, 1% deer, and other prey (none of which exceed 1% of the diet) comprising the rest. The sex and age of wolf-killed elk was 29% cows, 27% calves, 26% bulls, with the rest (17%) elk of unknown sex and age. Wolves selected elk calves in early winter and bull elk in late winter. In summer, the importance of elk as prey decreased, and mule deer became part of the wolf diet.

Yellowstone Wolf Project: Annual Report 2003

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