Answer:
They were used to keep food cold.
Step-by-step explanation:
Before the coming of the refrigerator, hunters store dead buffalo during winters so that the meat could last for a period. Hunters would dig ice holes and fill it with blocks of ice. Once the hole was well stuffed, the meat would be dropped into it and covered up. During the winter, meat would become freeze and stay stored well into the summer. In summer, the hunters would go back to these buffalo hole and took out preserved meat.