The bighorn sheep is a species of sheep native to North America named for its large horns. These horns can weigh up to 30 lbs. (14 kg), while the sheep themselves weigh up to 300 lbs. (140 kg). Recent genetic testing indicates three distinct subspecies of Ovis canadensis, one of which is endangered: O. c. sierrae. Sheep originally crossed to North America over the Bering land bridge from Siberia: the population in North America peaked in the millions, and the bighorn sheep entered into the mythology of Native Americans. By 1900, the population had crashed to several thousand, due to diseases introduced through European livestock and overhunting. Conservation efforts (in part by the Boy Scouts) have restored the population.