When snow blankets the meadows and outlines the spewing hot pots of Yellowstone National Park in winter, bison and elk head to lower ground where grasses can still be reached beneath the powdery forest floor. Wolves follow, primarily to the Lamar Valley, one of few areas in Yellowstone that's accessible by road in winter. The Yellowstone Association Institute, in partnership with park concessionaire, Xanterra, runs wolf tracking programs every winter that follow resident packs by bus, snow shoes, or cross-country skis. If you're lucky, your group will run into the "wolf watchers," telescope-peering volunteers led by Rick McIntyre, who has monitored Yellowstone wolves every day for more than 10 years. Once you feel like your toes have become popcicles, soup and hot drinks will save you at Buffalo Ranch, the site that helped preserve one of the last bison herds in the United States. The day's adventures end at Mammoth Hot Springs Hotel, unless, of course, you brave the cold again to soak in the Boiling River.