For six months each year forbidding temperatures challenge the wildlife in the park. The bison literally have to dig up their food from beneath the deep snow, and not all animals survive the harsh conditions during the long frost period.
With spring life becomes easier in the park. Bison and bear babies are born and learn their lessons of survival quickly as they are easy targets for the predators.
When pioneer James Colter first explored the Yellowstone in 1807-08 nobody believed his reports. So the Hayden expedition of 1871 made sure to present evidence of the area's wonders that helped establish the world's first national park.
