"The reintroduction of wolves in YNP provided an opportunity to pose the following 5 questions: (1) How would winter severity effect wolf predation on a previously wolf-free elk herd? (2) Would introduced wolves tend to take older, malnourished , or otherwise vulnerable elk as they do with other prey (summarized by Mech 1970 and Mech et al. 1998)? (3) What is the kill rate and amount of prey consumed? Usually the degree to which wolves consume each kill depends on prey vulnerability at the time. During rare periods when prey are especially vulnerable and abundant, wolves kill often and may not completely consume each carcass (Pimlott et al. 1969, Mech and Frenzel 1971, Peterson and Allen 1974, Carbyn 1983, Miller et al. 1985, Boyd et al. 1994, DelGiudice 1998, Mech et al. 1998). This pattern is also common in other carnivores (Kruuk 1972). (4) Would reintroduced Yellowstone wolves find predation so easy that they would eat small amounts from each kill? (5) Finally, how would these relationships be effected by winter severity?"

"The 1997 winter was 1 of the severest on record with a Winter Severity Index (WSI) of –2.6 on a scale of –4.0 to +4.0. The 1998 winter was relatively mild with a WSI of +2.9"(999)

"We observed 24 wolves in 1997 and 57 wolves in 1998 at the remains of 55 and 62 kills or probable kills, respectively."(1000)

"The mean 1997 kill rate of 17.1 kg of prey/wolf/day was higher than the 1998 rate of 6.1, a difference that was consistent among packs (Table 3). In addition to killing more prey on a biomass/wolf basis in 1997, the wolves also killed more individual animals (1.9/wolf in 1997 vs. 1.1/wolf in 1998)."(1000)

"During our 1997 study, the Druid Peak pack, Rose Creek pack, Leopold pack and scavengers consumed an average of 7% of the available food from their kills on the day they made the kill (n=5), and 23% after 1 more day (n=15; Table 4); 5 kills were untouched to about 5% eaten. During 1998, wolves and scavengers consumed an average of 86% of the available food from their kills the day they made the kill (n=14), and 89% after 1 more day. All kills were fed upon (n=23)."(1000)

"Mean marrow fat content for 22 adult elk killed was 27% in 1997 and 70% for 20 adult elk in 1998."(1000)

"In 1997, all but 2 of the elk kills during our study were adults (including 1 yearling), whereas in 1998, almost half the elk killed in March were calves. Of the adult elk killed, most were old females and males of various ages."(1001)

"During 1997, at the end of one of the most severe winters on record, YNP wolves had a higher killing success rate, killed more prey, and consumed less of each carcass than in the mild winter of 1998. The nutritional condition of the prey killed in 1997 was poorer than of prey killed in 1998."(1001)

"Although YNP wolves killed prey in poor condition during both mild and severe winters, they had a lower success rate during the mild 1998 winter, and a lower kill rate (despite an increased wolf density), and they tended to promptly consume all that they killed. Their 1998 kill rate was still high compared with published data (Schmidt and Mech 1997). Further, they were not aggressive or persistent in defending their kills from scavengers, indicating they had adequate provisions. Nevertheless, the degree of consumption of their kills showed that they did not kill more than they could immediately eat in 1998."(1002)