Digging for bones in Wyoming

Justin Sipla ascends a rope 80 feet to reach the mouth of Natural Trap Cave in north-central Wyoming after working on the cave's floor in this July 2014 image. The cave holds the remains of tens of thousands of animals, including many now-extinct species, from the late Pleistocene period, tens of thousands of years ago. Scientists have resumed digging here for the first time in more than 30 years.

Excavating in Natural Trap Cave

Justin Sipla, from left, Julie Meachen, and Jenna Kaempfer collecting samples for analysis inside the Natural Trap Cave in north-central Wyoming.

Excavating in Natural Trap Cave

Researchers in the interior of the Natural Trap Cave in north-central Wyoming.

Excavating in Natural Trap Cave

A view of  the interior of the Natural Trap Cave in north-central Wyoming.

Excavating in Natural Trap Cave

BLM Paleontologist Brent Breithaupt at the mouth to the interior of the Natural Trap Cave in north-central Wyoming. The cave holds the remains of tens of thousands of animals, including many now-extinct species, from the late Pleistocene period tens of thousands of years ago.