Answer:
Plains Indians started hunting buffalo more efficiently.
Step-by-step explanation:
On Average, Buffalos can run up to around 35 mph. This made it really hard for north Americans to hunt Buffalos unless they can catch them by surprise (average running speed for humans is only around 9 mph)
After the Spanish introduced the use of horses as a method of transportation, the buffalos can conduct a chase to the buffalos even when their targets were running away at full speed.