The Endangered Species Act helped save Yellowstone's grizzly bears from extinction, but that doesn't mean the great bears are out of the woods.

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See additional print additional Web and print resources about wolves and Yellowstone National Park.

Although the gray wolf remains an endangered -- and therefore protected -- species, wolves nevertheless face the same risks as any other animal species.

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The Yellowstone buffalo herd has become enmeshed in several heated debates over how the park's wildlife should be managed.

View additional online resources for NATURE's "Yellowstone Otters."

Yellowstone National Park, established in 1872, is a geothermal landmark. This unique environment has a built-in heating system that keeps rivers and lakes from freezing completely.

The American river otter once inhabited waterways throughout the United States. Over time, a combination of the fur trade and habitat destruction have caused the otter's numbers to decline.

Yellowstone National Park is home to some of the most spectacular natural wonders of the world. It's also a haven for the river otter, star of the NATURE program Yellowstone Otters.