Natural Trap, Wyoming, 1975

In August 1975, there were three ways to get to the bottom of the Natural Trap — scaffolding, rapelling and falling. I liked to rapel into the cave but climb the scaffolding back to the entrance.

In August 1975, while working for the University of Kansas, I was assigned to report on a dig in a cave in Wyoming. I didn’t know the Miocene from the Eocene, but I was happy to be on the road, it was a paid week out of the office, and I wanted to get back to Wyoming for a visit. I didn’t get paid expenses, so a friend and I camped out along the way to save money, making a stop at Yellowstone National Park.  I still remember the bird-sized mosquitoes buzzing around the tent, driving us crazy.  We eventually slept in the car.

Here I am standing outside of my Army Surplus tent. To the left you can barely see an overturned car from the early 1960s that had been used for target practice. The paleontologists’ camp was near derelict uranium mining camp cabins. (August 1975)

The dig itself was a thrilling adventure beginning with the drive up the boulder-strewn single-lane John Blue Canyon into the foothills of the Big Horn Mountains (below the road was the carcass of a Range River that didn’t survive).  Once there, we lived in Army surplus tents, ate grilled Cornish game hen and rapelled into the cave, which was packed with fossils from the Pleistocene epoch.
I soon got a crash course in paleontology. For thousands of years during the Pleistocene Epoch, mammals had fallen into an 85-foot-deep cave on the western slope of the Big Horn Mountains. Paleontologists from KU and the University of Missouri at Columbia were digging up the bones of thousands of animals, such as mammoths, cheetahs, camels, bison, bears and horses. (After horses went extinct at the end of the Pleistocene, they didn’t populate North America again until the Spanish brought them in the 1500s. )

Paleontologist Larry Martin examines a specimen.

I’ve been hooked on paleontology ever since this trip. I don’t mean that I love the dirty and painstaking work of actually uncovering bones and fossils and trying to figure out what and how old they are, but the excitement of seeing discoveries made in exotic locales and learning about how these animals lived and died. I’m afraid that makes me a bone-digging voyeur.

 The dig revealed a lot about the climate in the area by the types of animals that were found.  The Pleistocene climate was marked by repeated glacial cycles.  At the maximum of this Ice Age, 30 percent of the Earth’s surface was covered by ice.  At the time of this dig, it was thought we were heading into another Ice Age. Newspapers and magazines warned that it could happen very quickly and that possibly a little more carbon dioxide from the burning of fossil fuels might stave it off and keep us from freezing to death.

The food in camp was great!

Larry Martin, now head of vertebrate paleontology at the University of Kansas, was one of the expedition leaders at the dig, which was conducted with B. Miles Gilbert from the University of Missouri at Columbia from 1974 to 1980.  Some of the Natural Trap specimens are on display at K.U.’s Museum of Natural History. Paleontologist George Blasing featured Dr. Martin and the Natural Trap in Episodes Nine of “Jurassic Fight Club” on the History Channel. Dr. Martin has also appeared on NOVA.
I’ve kept up with Dr. Martin through the years and have written about K.U.’s dig of Jurassic dinosaurs near Newcastle, Wyoming. (More on that in a future post.)
Below is a story I wrote that appeared in several newspapers in 1975, including The Kansas City Star.  Except for a few minor editing changes, the story appeared as published below.

AUGUST 1975 — The western foothills of Wyoming’s Big Horn Mountains are arid, red and rocky, peppered by clumps of pungent sage brush and dwarfed juniper trees.

A few cattle graze on the sparse grass, and an occasional deer bounds through a ravine, but the harsh terrain supports few animals.

It wasn’t always so desolate.  In the Pleistocene Epoch, 10,000 years ago and earlier, the Big Horn foothills teemed with large mammals.  It was a wetter climate.  The seasons were more moderate, the land more lush and more forested than today.

Herds of bison, horses and camels grazed on the meadows, stalked by fleet, long-legged bears and cats.  Mammoths lumbered through the valleys.  Bighorn sheep cropped hillside grasses.

The hills are limestone and pocked with caves and hollows.  One cave mouth was open to the sky at the end of a finger of land, affording no escape for a panicking herd pursued by a fast-moving predator.  This narrow peninsula was flanked by canyons which funneled predator and prey toward a rise, and then they all plummeted into the hole.  Hungry wolverines and jackal-like dire wolves, catching a tempting whiff of rotting meat, crept daringly on a ridge of melting snow along the edge and tumbled below.

Here the crew digs in the Natural Trap Cave. Working hours were short because the crew relied on natural light, which only fell in the cave from mid-morning to mid-afternoon. Daylight was augmented by a few lamps.

As thousands of years passed, the cave gathered a scrambled mass of victims, preserved in layers, until a severe change in the climate wiped out most of the large mammals above, ending the cave’s carnage.

 Today (1975), paleontologists and anthropologists from the University of Kansas and the University of Missouri – Columbia are making an easier descent to the bottom of the cave to return the bones of those Pleistocene animals to the surface, where they become the survivors of their age.

A grate covers the opening of the Natural Trap to keep modern animals and people from falling in.

The hole, known as the Natural Trap, is a vast 85-foot-deep dome-shaped limestone cavern (karst sinkhole).  Tens of thousands of years ago part of the cavern’s roof fell in, making it a death-trap.

The names of the Pleistocene mammals in the trap may sound the same as some of the modern-day Big Horn animals — bighorn sheep, bison, bear — but the Pleistocene specimens were larger, different animals. The Pleistocene versions often had longer legs. The modern counterparts of other animals also found in the Natural Trap are smaller, such as wolves, wolverines and pronghorn antelope.  Other animals found in the Trap, such as horses, camels, American lion, mammoth, woodland musk ox and American cheetah, all went extinct at the end of the Pleistocene.

“I don’t think we have a good potential in a specimen from the cave that is a good ancestor of any animal now in the area, ” Dr. Martin said.

Humans, who hunted the large Pleistocene mammals for food, partly has been blamed for their extinction, but most of the evidence points to climatic change as the cause, not only in North America but world-wide, Dr. Martin said.

The paleontologists are studying soil samples and bone deposition, looking for clues to the climatic fluctuations of the past, useful in anticipating future climate changes.  The types of animals found in the trap probably will indicate the climate at the time since animals migrate to their favorite climates, Dr. Martin said.

In the forefront are Dr. Miles Gilbert, left, and Dr. Larry Martin, right, sorting a tray of specimens.

The specimens from the trap went to K.U. Museum of Natural History, which has the tenth largest vertebrate paleontology collection in the country.

There have been some remarkable finds, such as the cheetah-like cat, which has the characteristically long radius and ulna limb bones of the modern-day cheetah and has been found nowhere else in North America, Dr. Martin said.

“The cheetah-like cat found in the cave is the first good evidence that there was one in North America,” Dr. Martin said.  There were several cheetah-like cat specimens found in the trap with the small cheetah canine teeth, necessary to give more space in the nose area. To run as swiftly as it does, the cheetah requires a large lungful of air.

Larry Martin digs in one of the areas staked out in the Natural Trap.

The short-faced bear specimen is one of the most spectacular finds do far (as of August 1975), Dr. Martin said. The beat was a long-legged open country animal, adapted for running and more carnivorous than modern-day bears. (A fight between a short-faced bear Arctodus simus and an American lion Panthera atrox near the Natural Trap is featured in episode nine of the History Channel’s “Jurassic Fight Club” in 2008.)

The bones of horses are the most abundant specimens found. Many seemed to have landed on their feet, snapping their leg bones. The cave’s fine limestones preserved the bones well, but most were broken from the initial impact or later by roof fall and other carcasses.  To find the bones fragment, the crew sieves all of the dirt from each five-by-five section.  The pieces are then painstakingly washed, scrubbed with toothbrushes and sorted at camp. Some are glued there, the rest to be assembled at K.U.

Temporary scaffolding is erected and dismantled each summer, the most dangerous part of the expedition, Dr. Gilbert said.  The group couldn’t afford permanent scaffolding.  Many team members prefer to drop into the cave by rappelling, which was the only way to enter the cave before 1974. There is a natural ledge just below the cave opening from which it’s easy to rappel. Climbing out by jumaring on a rope is a much more strenuous exercise, so everyone climbs up the shaky scaffolding to get out of the cave.

The scaffolding rests in a depression where deposits continually are eroded by rainfall even though the annual precipitation averages less than 15 inches. Bones remain intact in a mound to the east of the scaffolding where the crew lie on their sides and stomachs picking at the dirt, ice picks and whisks brooms.  Dig sites were selected at random until a few productive sections were located.

The dining tent at Armpit Camp.

There are possibly 30 feet of deposits to excavate, Dr. Gilbert said. Specimens could be as old as 50,000 years at the bottom, but there’s no way to tell except to dig there.

“I personally don’t want to dig the entire cave,” Gilbert said.  “I’d like to leave a third or half of it for the future to investigate when they have better technology to understand it.”

George Blasing’s Blog “Dinosaur George” is on my blogroll at the right.

History Channel’s Jurassic Fight Club

About Larry Martin.

About the Pleistocene Epoch.

When the crew wasn’t working, there were classes about the area’s plants, animals and history. Some of us could barely stay awake after a late-night trip exploring another cave, which required climbing in and out by rope. We were led by a geologist mapping the caves for the U.S. Geological Survey. He liked to scare us by leading us into a cavern and then ask us which way we’d come. We never knew. Another time he told us to turn off our acetylene head lamps. It was very dark and unsettling to be so far under the earth. A couple of times while exploring caves we felt the earth shake from dynamite blasts and worried that more rocks would fall from the ceiling to join those on the cave floor.

Armpit Camp.

This is a section of Bighorn Canyon National Recreation Area north of the Natural Trap.


Sign at the opening to the Natural Trap, which is now closed.

An update: Natural Trap to Be Reopened. and The Daily Mail: The Natural Trap to Be Reopened.


Filed under Animals, Biology, Environment, History, Natural History, Nature, Paleontology, Science, Travel, University of Kansas

26 responses to “Natural Trap, Wyoming, 1975

  1. You know, I never knew that the Natural Trap existed! Thanks for the great history lesson and fabulous photos. We like dinos too.

    Information about the Natural Trap is hard to come by, but there is some online. It’s a very significant find of Pleistocene mammals, but you don’t hear much about it. I’ll probably post more photos when I get digital copies of some color slides that I have. I’ll also write about the Jurassic dinosaur dig, although I don’t have good photos. That was a fantastic, amazing site. The fossils of a huge brachiosaurus were just lying there on a hilltop, which once was a riverbed. There were so many fossils, you’d find one if you dug just about anywhere. Cathy


  2. What a fascinating account. And yes, Catherine, I did see this post. It was a great read and I really enjoyed it. I just didn’t have time to comment before now.

    Those are some great photos. Thanks for sharing them with us.

    The sign for Natural Trap Cave is interesting, especially the part where they ask visitors to refrain “from throwing objects into the cave.” That immediately brought to mind Morning Glory Pool at Yellowstone National Park, also in Wyoming.

    That amazing pool is known for its vibrant colors, but the color has diminished over the years because, get this, visitors have thrown “tons” of garbage into the pool. The garbage clogs the pool’s vents which reduces the temperature of the water which in turn limits the bacteria that need a certain temperature in order to survive. It is those bacteria that provide the pool with its unique and thrilling colors.

    I’ve never actually been to Wyoming to see it in person but I recently became aware of the pool and was thinking about blogging about it at some point in the future. It really troubles me to think that people would throw garbage into one of the natural wonders of the world.

    The fact that the sign at Natural Trap Cave has to even mention this is also troubling.

    So, what was it like rappelling down into that cave? It must have been incredible.

    I remember that Morning Glory pool was one of my favorite sights when I first went to Yellowstone Park in the Fourth Grade, so I have seen it change over the decades….Yellowstone is an amazing place. My husband backpacks there every year. I only go when the plan is to sleep in an hotel. I don’t mind sleeping on the ground, but I have an irrational fear of grizzly bears. I’m just sure that one will drag me out of my tent at night, although that did happen to a cousin’s college roommate in Glacier National Park, so maybe it’s not so irrational.

    Rappelling was a lot of fun, though I did it very slowly. The fact that you weren’t banging off the side of the Natural Trap cave, because it was like a giant fish bowl, made it easier. The rope expert did it in seconds and then stopped himself instantly when he neared the bottom. Climbing out by rope, as we did in another cave, was exhausting. I have no upper body strength. I look forward to your Morning Glory Pool post. There are many different types of bacteria in pools in Yellowstone creating an amazing array of colors. Maybe I can find some photos that show this, although they’d be pre-digital so I’d have to scan them. Cathy


  3. Wow, how fortunate you were to get an opportunity for an adventure like this one.

    I’ve rappelled and I’ve been on scaffolding. Scaffolding scares me enough that I think once I was in that cave I’d never make it out.

    What a striking shot that first photo is!

    I still feel incredibly lucky that I got this opportunity. The scaffolding was very shaky. The black and white photographs were all taken by David B. from the KU Office of University Relations. David, if you’re out there, please check in! Cathy


  4. sandysays1

    Hi CS,

    What a coincidence my human, the Geezer, is very involved with the Randell Research Center here in Florida. RRC is part of the University of Florida and the Florida Museum of NH. The Center is a 60 acre coastal site that has had human habitation for as far back as 11000 years and continuous settlement for the last 2100. (Primarily the Calusa Indians) Because of the unique factors here materials in the mittens are preserved and allows the archs to do some unique work in regard to sea levels. The Geezer is chairing an effort raise money for more research there. In the last 2000 years the levels have been 4 ft higher and 2 ft lower during that brief period, a blink of the eye as far as time is reckoned. Its fascinating once you realize the earth will do its thing and only man’s arrogance allows him to think he can excercise any control over it. Sandy


  5. What a fantastic article! I am also very interested in the subject. I have always tried to get a friend to go with me on a trip like that. The Forest service used to offer spots to beginners to go and help do the painstaking brush work, etc. It is something I still plan to do. So what did you think of rappelling? I did it once on a quartz collecting trip, needless to say, I was a little freaked out, particularly because the rope was a little muddy and slippery. I sure did not want to look how far down it was from the top of the mountain I was hanging from. I decided once was enough. That does give me the idea to write about my quartz hunting trip and my snake river canyon trip, which was loaded with native american sites, cave paintings, and a lot of history. Thank you, for the enjoyable and informative article! I learned a lot.


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  7. healthprotector

    amazing collection of old pictures. every pics having separate identity……gr8.


  8. Michael Stolberg

    I was in Armpit (NaTural Trap) in the summer of ’75 or ’76. I remember bathing at the horse troughs each evening, shivering in the chill. Sitting around the fire drinking Yukon Jack, ‘the Black Sheep of Canadian whiskey’, everyone just grunting until the first sip of coffee in the morning. I remember using the outhouse early in the morning so you can keep the door open, waving to B. Miles, ’cause he had the same idea. And the night we all spent exploring a cave (not at the dig)..Names I remember besides B. Miles, were Steve Chomko, ‘Bear’ Fuller.


    • Eric

      Michael you may remember my sister ,Freya she is in the photo with Barry Fuller aka”Bear” .If you have any photo’s you would like to share ,I would be very appreciated .


  9. S White

    I am disappointed to read NTC has been closed to cavers. I rapelled into it many many times in the 70’s. It was a pretty boring cave to explore, but it was a fun trip. The irony is that cavers are typically very careful about disturbing the cave and contents. Looking at the pictures it sure seems that the in the name of science that there has been much more damage done to it’s natural setting than anything done by cavers over the years. We would have never dreamed of digging deep holes and carting stuff out. And to build scaffolds to the surface would have been out of the question. When we left the cave, there was zero sign that we had been there. We would tied our ropes to the bumper of our car and drop in. I hope that after all the bones have been removed that the NPS will consider taking the gate off and let the caving community drop in again. Looks like a bunch of nonsense and waste of tax dollars right now.


  10. Eohippus

    Thanks for the memories!

    As a regional news reporter, I visited “Armpit, Wyoming” in summer, 1977, and my report was datelined “Armpit,” which aggravated some Wyoming folk. Took some color slide shots from the bottom of Natural Trap Cave, which showed the scaffold and top opening.

    That summer, they had the sabre-tooth tiger skull, pretty much intact. Spectacular!

    Sure enjoyed your report — Gracias!


  11. Leslie M.

    Don’t know if others from the summer of 1985 still recall our Earthwatch trip to Natural Trap; an awesome three weeks. I have so many great memories, including of “Bear” and Billy Mack. Are any of you out there?


  12. Cathy,
    Thanks for pointing me to this post. What a wonderful piece of journalistic account you’ve written of an amazing dig. Yes, I can relate the two caves… Chauvet and this one, both have such a wide variety of animals all in one place, simply amazing. So now I’ve learned that a cave is not necessarily horizontal but can be deeply vertical… just a concept I haven’t thought before.

    But this also makes me think of an area in our Province called “Head-Smashed-in Buffalo Jump” near Fort McLeod, Alberta. It’s a UNESCO world heritage site. For thousands of years aboriginals had chased buffalos off this cliff, a natural trap too but utilized by human hunters.

    And about Yellowstone National Park… I think just around the same time, in the summer and likely ’75 when I was in college, a few of us friends hopped into a car and drove all the way from Calgary, Alberta to Yellowstone on a whim. Spent a couple of nights there in the car and drove back. Ah… those were the days. I’ve enjoyed your account of your adventure! 😉



  13. Rich brame

    Brings back the memories of caving on Little Mountain. See this shot of scenic Armpit:


    • wayne

      I visited Armpit and the trap when I worked for the BLM out of worland around 1977. I still tell people about the trap. It was Brian, me and John F.
      Had fantastic trout fishing nearby.

      wayne L


  14. Sheila F....

    1978 Earthwatch in August…I was the official “Photographer” for the trip…what fun and need I say more about the adventure we all had that impacted my life..I’m so glad to have found this site as the whole experience had been in my head and heart since those very impressionable days…Miles, Kansas and the rest of our crew…where are you and what are you doing now? I’m just amazed…thank you for bringing me back to another time


    • Pat Dawson

      I have some slides I shot while at the bottom in 1977. Too bad I am unable to share them on this site, but there is one down at the bottom of this story:


    • Jim Hess

      HI!!!!!! I so hope you receive this. I was there in 1978 with Earthwatch, I think the first two weeks. GREAT memories. I had the green jeep. Have some pictures I can send as soon as I know I can contact you. Send response to my email at… SOOO excited. Jim Hess


      • Jim Hess

        Hi Catherine, Sorry for my absence…gmail messed up up my address. Here’s my new address Please replace, and if possible, cchanger the address on previous post to correct. I do have some additional pictures which I’ll send you. Thanks. Jim


    • Miles Gilbert

      Ya’ a’ teeh’ from Navajo land Sheila,
      I retired from 11 years as archaeologist for the USDA-Natural Resources Conservation Service here in AZ last June. Now I can afford to spoil my grand kids rotten and send them home. Alas, Larry Martin passed away last year, I’ve lost touch with others except Kerry Lippincott and Steve Chomko. You can post me at 1192 Whitetail Drive, Show Low 85901. Best regards,


  15. Tom Meador

    I was onsite for 2 weeks during the Summer of 79-Probably one of my best vacations and experiences so far in life- I would love to hear from anyone who was there durning the Summer of ’79. Miles, Randy, Bear – The bathing German girl??anyone?


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  19. Brandie

    I wish I could post the pictures I took yesterday, we went jeepin, and stumbled on the Ranch, but before that and right next to it were areas with signs that said, dangerous radon do not go in. Both areas were blocked off. We thought that was weird, so I’m wondering if those were the caves? We wondered also about the ranch and it’s history, I’m assuming now that you all built it?


    • Patrick Dawson

      Those are inactive old uranium mines on BLM land from the early 1950s. Most have been sealed and posted for safety and health reasons. Natural Trap Cave is east of the Bighorn River Canyon, and is sealed with steel grates. Two other caves up there are also locked, but spelunkers can sign out the key at the Worland, Wyoming BLM office, last I knew.

      Liked by 1 person

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