The definition of ethereal is “extremely delicate and light in a way that seems too perfect for this world,” as fitting a definition for the small number of bison that remain in West as it is for the fog through which they now pass.
Certainly, a bison itself is anything but ethereal ― each is about as light and delicate as a Mack Truck.
Yellowstone’s winters are often severe with deep snows and temperatures that reach -44F. With thick skin and underfur, long hairs and layers of fat, these massive beasts are built to survive and thrive in such an environment. Even so the geyser basins, hot springs and thermals are attractive destinations during these frosty months.