Scientists Unearth Fossils At Natural Trap Cave One Last Time

Aug 4, 2017

Wyoming Public Radio Producer Erin Jones descending down into the cave.
Credit Maggie Mullen

Thousands of years ago in northern Wyoming, countless animals fell to their death at the bottom of an 85-foot cave. Natural Trap Cave has long been closed to recreation, but scientists have spent the last four summers unearthing the remains of many now-extinct animals. Excavations will soon come to an end.


Out on the Big Horn Basin, it’s windy and the views in every direction stretch for miles. It’s not exactly where you might expect to find a cave. That might be why so many animals, like the American cheetah and the short-faced bear overlooked the 15 by 20-foot opening and tumbled into Natural Trap Cave.


Now Bureau of Land Management has covered the hole with a metal grate, to prevent falls and illegal fossil collection.


Juan Laden is standing near the opening, where he’s putting on his harness and securing it the safety rope.


“The morning ritual right away is getting my rig on,” says Laden.


He’s been teaching researchers from Des Moines University how to safely descend and ascend using a rope system for the last four years.


Juan Laden, head caver, preparing the rigging for that day’s descent.
Credit Erin Jones

This is the only working team of scientists with approval from the BLM to excavate the site, and are some of the few people in the world who have had the chance to see the inside of the cave.


Excavations of the cave have been done before by other universities, but not since the 1970s. The cave remained closed, until Doctor Julie Meachen and her team were approved to re-enter in 2014. She says the cave wasn’t necessarily off-limits during those years, but it was remote and expensive.


“You can’t just walk down into the road into the cave,” says Meachen. “You have to rappel in. You need a relatively large crew and to do that you need a lot of equipment. You need people who can train the crew in the rappelling techniques. And you need all sorts of support staff to do this.” 


And Meachen’s team could be the last people to step foot on the bottom of the cave. Unless they seek and secure more funding, after this summer, the cave will become off-limits. For now, they’re packing up their gear for another day in the cave.


Natural Trap Cave
Credit Maggie Mullen

Only one person can descend at a time, and when it’s my turn I can feel my heart pounding in my chest. After clipping into the safety rope, I walk down a ladder that’s secured against a grassy ledge, where Juan Laden is standing. Besides a few headlamps bobbing around below, it’s impossible to see any other details through the darkness of the cave. Laden goes through his safety checklist, and helps me adjust the rappel rack I’ll use to control my speed as I descend.


Soon, I get used to the feeling of dangling in the air and my eyes begin to adjust. I can make out the cave’s bell shape that expands into a much larger space.


Once I reach the bottom, it’s cool—about half the temperature that it was outside, and Dr. Julie Meachen says that’s part of what makes Natural Trap Cave so unique.


“The cave is like a refrigerator,” says Meachen. “It’s constantly cold, it’s never above  42 degrees Fahrenheit.”


The low temperature paired with the cave’s 98-percent humidity is ideal for preserving genetic material. Meachen says the specimen quality varies—the ones that are right underneath the cave’s opening are not as intact because of precipitation.


“The ones that are more peripheral, have much better preservation and we’ve got original collagen still left in the bones. So they’re technically sub-fossil, they’re not completely fossils. So we’ve had basically sub-fossils of animals that were alive 30-thousand years ago,” says Meachen.


Researchers in the drop zone.
Credit Maggie Mullen

The main question they’re interested in is two-fold—how did the climate and habitat change from the late Pleistocene to the early Holocene, and how did animals respond to that change?


Meachen says she’s especially interested in the fossils of species that survived the extinction events of the Pleistocene.


“Coyotes… we also have some wolves, we have some pronghorn antelope, we have big horn sheep, we have bison. So these are all animals that we think of today, but are they the same in the Ice Age, through the Pleistocene as they are now?” asks Meachen.


They won’t be able to completely answer this question until they can look at the fossils’ genetics. Certain animals may have been able to adapt to a changing climate. If so, Meachen says they could develop a deeper understanding of the relationship between climate and environmental shifts.


“Although that wasn’t one of the goals of this project,” says Meachen. “It might be a consequence of the project, so that would be really great.”


Meachen says she’s thankful for the last four years.


“All of the things you have to do, all of the data collection, and all the minutia you have to do gets really tiresome. But then somebody finds something really great, and it makes it all worth it,” says Meachen.


Even if they’re the last team to descend into Natural Trap Cave, there’s the potential to continue learning from the fossils they’ve gathered. Over a thousand of the specimen collected by Meachen’s team will soon be stored at the University of Wyoming, where the public will get the chance to see them for themselves.