Hayden Valley is the great open stretch between Mud Volcano and Canyon, and the Lower Loop's best bet for large animals. Its grasses grow on fine sediment left by glaciers and an ancient lake, and that is what keeps the trees out. There is no designated parking, only large pullouts, mostly on the river side, and the Trout Creek vault toilet is on the left for northbound drivers. Grizzlies are most likely in spring and early summer, and bison gather in large herds through the August rut. Coyotes are nearly a sure thing, and wolves appear often. Wildlife jams can multiply the drive time. The valley carries Hayden's name, and Tribes have asked to change that.
The trees quit. That's Hayden Valley opening up, and they quit for a reason. The valley floor is fine-grained glacial sediment over fine-grained lake sediment, and in soil like that, grasses beat trees to the water. An ice dam south of Canyon Village once backed up the Yellowstone River and flooded this valley under an ancestral lake much larger than today's. The rules here are serious. Pull off only at pullouts, most of them on the right, the river side, with all four tires past the white line. Never stop in the lane. Stay twenty-five yards from bison and elk, and a hundred yards from bears and wolves. Bison have injured more people in Yellowstone than any other animal, and they can run three times faster than you can. Grizzlies show mostly in spring and early summer. Bison gather in big herds in spring, in early summer and for the rut, when bulls bellow, wallow and fight and a group can reach about a thousand animals. You'll almost always find coyotes, and often wolves. Watch for shorebirds on the mud flats at Alum Creek, sandhill cranes, and pelicans cruising the river. Those bison aren't only grazing. They leave winter range with the spring green-up, then let it pass and keep regrazing the same ground, which keeps the plants short and nutritious. Nowhere else in the United States have bison lived continuously since prehistoric times. Now look east across the river, out at the horizon. A gentle slope out there, shaped like a Hawaiian shield volcano, is Sour Creek Dome, ground that still moves up and down.
Photo: NPS Photo / Neal Herbert · Public domain