Bighorn sheep, Theodore Roosevelt National Park, 2015.

Bighorn sheep (Ovis canadensis) originally crossed into North America over the Bering land bridge from Siberia. The population peaked in the millions and bighorn sheep entered into the mythology of Native Americans. Unfortunately, by 1900 the population had crashed to just several thousand due to diseases spread through the introduction of European livestock and overhunting. Conservation efforts have restored the North American population. Bighorn sheep from British Columbia were reintroduced to the north unit of Theodore Roosevelt NP in 1996.