BISON VIDEO: Officials at Yellowstone are saying it is bison mating season and the male bison are very aggressive right now. Remember to keep a distance of 25 yards from all bison and elk and 100 yards from other wildlife. Thanks to Yellowstone National Park for this video. Send us your photos and videos: nbcmontana.com/chimein | NBC Montana

The United States' bison population diminished dramatically in the late 19th century. Follow their sparse sightings in Iowa at the time and learn more about two men with connections to our state, William Hornaday and John Lacy, and their roles in keeping the animal from vanishing altogether. | Iowa PBS

Bison herd migration.🦬🦬🦬 | Jake Slater

WATCH THESE BISON SWIM THE YELLOWSTONE RIVER 👀 This small herd of bison decided to take a nice cold swim this spring (notice the melting snow ❄️ on the riverbank) in the Yellowstone River! Bison are the largest mammal in North America. Male bison (called bulls) weigh up to 2,000 pounds and stand 6 feet tall, while females (called cows) weigh up to 1,000 pounds and reach a height of 4-5 feet. It's hard to believe these large creatures can swim but as you can see from the video they do just fine!