Boy skiing through snowy trees in Yellowstone National Park, Wyoming.

Sunstar through fog in trees at Mammoth Terrace in Yellowstone National Park.

Grey wolf running through snow right at you!

Boy skiing through frosty trees in Yellowstone National Park.

Old Faithful at sunrise with lodge in background, Yellowstone National Park.

Boy snowshoeing through fresh powder in Yellowstone National Park in winter with geysers in background.

Yellowstone National Park trail in Geyser Basin with two children skiing.

Cross country skiier on boardwalk in Yellowstone National Park's Geyser Basin, Wyoming.

Two skiiers, children viewing an erupting geyser from Yellowstone National Park's Geyser Basin, Wyoming.

Frosty wolf close up, yes it is cold.

Grey wolf running right towards you through snow.

Grey wolf wide angle, what a view!

Grey wolf after running through snow, with tongue out, panting.

Blue star spring in Yellowstone National Park, Geyser Basin.

Castle Geyser with bison in background, Yellowstone National Park.

Old Faithful at sunrise in winter at Yellowstone National Park.