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.