When: Mid- to late December.
Where: National Elk Refuge, Jackson, WY.
What: Elk begin their migration to the refuge in late October/early November, so by December the refuge is teeming with the world's largest wintering population of elk (up to 7,000). Moose, bighorn sheep, and bison are other common winter residents.
Tip: The herd is visible from the highway, but your best bet is to rent a sleigh when the rides begin in mid-December, and head out to the southern end of the refuge for closer views. Don't get too close, however; elk can be dangerous when threatened.
For info: www.fws.gov/nationalelkrefuge; 307-733-9212.