Just over 500 years ago, Europeans arrived in North America. And with these colonizers came an animal that hadn’t been seen here for thousands of years. The horse returned to the Americas, now tamed and carrying the Spanish conquistadors. This new form of transport was rapidly adopted by the native people, which was bad news for some native animals.

Bison had once lived alongside the wild horses of North America, and had prospered at the end of the Ice Age while the horses became extinct. But now the new tame horse became the bison’s enemy.

The horse’s speed and stamina gave native people an advantage over their prey that they never had before.

The horse was an even bigger ally to the increasing number of European settlers spreading out across the continent. They killed millions of bison for their meat and hides.