Spring is a great time to spot wildlife in Yellowstone National Park, and in the park the Lamar Valley is a particularly good spot to find yourself in right about now if you want to see wolves, bison, elk, and possibly grizzly bears.
June is when adult wolves are spending a great deal of time hunting for food they can feed their growing pups. With several wolf packs having overlapping territories in the Lamar Valley -- the Agate, Lamar Canyon, Blacktail, and Silver packs -- your odds of spotting the adults returning to the dens aren't bad during this month. You can enhance those odds by getting into the valley right around sunrise, or late in the afternoon or early in the evening.
Grizzly bears are hungry, too, and with elk and bison calves on spindly legs, they at times become prey for the bears.
Several years ago I witnessed a very unusual sight in the Lamar Valley along Soda Butte Creek -- a grizzly had taken down an elk calf, and its squeals alerted a pair of wolves that came down from the north of the Lamar Valley to see if they coudn't take advantage of the situation.
To increase your odds of spotting wildlife, come prepared with a good spotting scope or long telephoto or zoom lens.