

Those animals include American cheetahs, mammoths and short-faced bears — species now extinct that were common more than 20,000 years ago.

Natural Trap Cave is a 15-foot-wide hole in the ground that opens up into an 85-foot-deep cavern. Over many years, tens of thousands of animals accidentally fell into the pit and died.

Starting Monday, scientists plan to resume digging in Natural Trap Cave for the first time since the early 1980s. One goal is to retrieve DNA from the animal bones.

They say the cave holds valuable clues to life in the last glacial period.