More than 12,000 years ago, early big game hunters who occupied lava caves in this area ate elephants, camels, and giant bison. As a gradual change to a warmer, drier climate turned local grasslands into more desert, their elephant herds left for cooler plains farther north. But 8,000 years ago, bison still were available here. Indians continued to hunt buffalo on these plains until about 1840, and then had to go to Montana for their plains hunting trips.