There have been few studies of wolf (Canis lupus) predation in multi-species prey systems characteristic of the Rocky Mountains. Therefore, I investigated the ecology of wolf predation amidst high ungulate diversity in NE Jasper National Park, Alberta, from 1989 to 1992. In winter, estimated populations of 420 bighorn sheep and 300 elk occurred in large groups mostly in patches of grassland habitat interspersed among coniferous forests. An estimated population of about 350 deer ($\ge$2 mule deer for every white-tailed deer) was dispersed more evenly in various cover types across the landscape. About 30 moose occurred as singles or pairs in riparian shrub types or scattered through upland pine or spruce-fir forests. Amidst this rich diversity of ungulates, a pack of 4-9 wolves in winter preyed more than expected upon deer (especially white-tailed deer and male individuals of both species) and used moose, elk and bighorn sheep less than expected. With ungulate numbers considered in terms of groups, however, the wolf pack preyed upon ungulates in proportion to availability (i.e., no selectivity). Adult deer and elk comprised most of the biomass in the wolves' winter diet, yet the proportion of biomass of elk and bighorn sheep (especially adults) consumed was less than that available. Kill sites of deer were characterized by greater relative density of elk and moose than typical for the landscape. During the denning period, the wolf pack selected deer fawns and fed on adult elk and bighorn sheep less than expected; wolves continued to use the different species in proportion to availability of groups. During the rendezvous period, the pack switched from deer to calf and adult elk (about a 20% shift) with significant selectivity for elk calves.

A re-examination of 9 studies across North America involving wolf predation amidst high ungulate diversity revealed that wolves preyed principally upon elk and deer. Elk represented the most profitable prey with minimal risk-of-injury whereas wide dispersion of deer facilitated frequent encounters. In this multi-species context, moose were less profitable due to risk-of-injury; opportunities for wolves to find bighorn sheep away from escape terrain seemed infrequent. Small group size, wooded or hilly terrain, and deep snow fostered wolf selection of elk. When elk were not as vulnerable, wolves preyed more intensively upon deer. I propose that wolves living amidst high ungulate diversity forage as 'expanding specialists' whereby they specialize on vulnerable individuals of large prey (elk and moose) yet readily generalize to common prey (deer). In a diverse prey system, wolf predation may shift among species depending upon annual fluctuations in winter severity or landscape changes. Wolf densities lower than predicted by Fuller's (1989) equation were all characterized by high ungulate diversity in which at least one of the prey species occurred in large groups.