LAST STAND OF THE GROUND SLOTH

The hole in the cliff didn't look so unusual. In fact, it might not even be much of a hole. An investigation would probably show it to be just a shallow overhang. Still, to Willis Evans, it had tantalizing possibilities. Suppose it were more than just a hole in the rock; suppose it were a cave. After all, the cliff in which it was located was limestone-and caves are often found in limestone. If it were a cavern, then a whole new field of possibilities would open up, because caves in this part of Arizona were often places used by early man. The hole in the cliffs could certainly stand some investigating.

The year was 1936. For several weeks Evans had been working as the foreman in charge of a small Civilian Conservation Corp "fly camp" at Pierce Ferry, gateway to the lower end of the Grand Canyon. Every day he and his crew of enrollees took off in boats and headed into the canyon where newly formed Lake Mead had now drowned the once roaring waters of the Colorado River. Their job was to take acres of drifting logs and debris out of the lake before the material became a navigation hazard, pile the material ashore and burn it.

Each day, as he and his crew entered the canyon, Evans looked with great interest at the small hole high above the lake and wondered just what might be in it. He was especially interested because several shallow caves and overhanging ledges in the nearby region had been found that contained valuable Indian artifacts. Perhaps this hole might furnish another important find. Having some knowledge of archeology (he had helped excavate Gypsum Cave in southern Nevada in which were found traces of early man) and being an Indian himself, he decided to investigate at the first opportunity.

The opportunity was not long in coming, and a few days later he and one of his enrollees worked their way up a steep slope toward the hole in the cliffs about 650 feet above the lake shore. As Evans pulled himself up onto the ledge in front of the cave, he noted that the opening was actually fairly large-it had only looked small from a distance by comparison with the great height of the canyon walls. As his eyes became accustomed to the dim light of the cave, he could tell the passageway led back into the cliff for a considerable distance, as he could not see the end of it. But his interest in the possible depth of the cave was abruptly forgotten as he got a good look at the floor-it looked like an old deserted horse stable with droppings strewn around in large quantities. He hadn't found an early Indian site, but he had discovered something far more ancient. The cave had obviously been used at one time by the prehistoric ground sloth, remains of which he had also seen in Gypsum Cave.

Because it was located so high above the lake, with a superb view of the towering cliffs and canyons, the cavern was promptly named Rampart Cave. Steps were immediately taken to find out what it might contain. The National Park Service assigned a crew to dig a test pit from the dung-covered surface of the fill to the rocky floor of the cave. However, what at first appeared to be a somewhat routine job of excavating quickly developed into a major problem. The materials making up the fill were powder dry and the least disturbance caused a heavy choking fog of dust to fill the still air inside the cave. Before the excavation could proceed, it was necessary to bring in masks to filter the air so that the workers could breath with safety. However, the mask did not eliminate the discomfort of being covered from head to foot with a thick, irritating layer of dust as the digging got under way.

The spot selected for the test pit was some distance back in the cave at a point along the wall where the room split into two wings. This seemed the logical location at which to dig. Most animals have a tendency to crawl back against a wall when they die inside a cave, thus the site selected for the pit seemed likely to contain the best collection of any fossil remains. Ás it happened, the choice was a good one. Almost from the start, the pit (6 ft. square by 20 ft. deep) yielded a vast assortment of bones. But it was what was uncovered with the bones that proved of greatest interest. Piece by piece there came to light large sections of the ground sloth's coatcoarse, rather long-haired, with a rich red-brown color. Not only was it now possible to reconstruct one of these animals (Notbrotherium shastense) accurately to scale, but his true color was known. So dry had the cave been that the hair was not damaged, and even tissue, such as a section of the animal's windpipe, was found in good condition.

back in the cave at a point along the wall where the room split into two wings. This seemed the logical location at which to dig. Most animals have a tendency to crawl back against a wall when they die inside a cave, thus the site selected for the pit seemed likely to contain the best collection of any fossil remains. Ás it happened, the choice was a good one. Almost from the start, the pit (6 ft. square by 20 ft. deep) yielded a vast assortment of bones. But it was what was uncovered with the bones that proved of greatest interest. Piece by piece there came to light large sections of the ground sloth's coatcoarse, rather long-haired, with a rich red-brown color. Not only was it now possible to reconstruct one of these animals (Notbrotherium shastense) accurately to scale, but his true color was known. So dry had the cave been that the hair was not damaged, and even tissue, such as a section of the animal's windpipe, was found in good condition.

That the cave had been occupied for fairly long periods of time was evident from the vast deposits of dung, ranging up to more than twenty feet in depth in parts of the cave. The remains of young sloths were found, but whether they were actually born in the shelter of the cliffs could not be determined for certain, but such would appear to have been the case. What caused the death of these young animals could only be surmised, but the presence of a mountain lion skull possibly supplied part of the answer. There were also evidences that the cave was used intermittentedly, as dust layers were found separating dung deposits. Apparently there had been long periods of time when it was not occupied at all. But the sloth wasn't the only animal of scientific interest found during the excavations. Bones of a species of prehistoric horse, a type of mountain goat, marmots, mountain sheep, ringtails, lizards, birds and even a tortoise, were uncovered. Speculation at once mounted as to what the presence of these animals indicated. After all, the area today today in which the cave is found is definitely low desert-hot, arid and without very much in the way of vegetative cover. Some of these fossil animals were definitely not desert dwellers in any sense of the word, at least modern day descendents aren't. Take the mountain goat for example. Our present day goat lives in the rugged highlands of our Northwest mountains and in Canada. He would certainly never think of coming down into the desert to live. The same can be said for the marmot. By nature and choice he loves the rocky slopes of cooler elevations, and seldom gets into an environment in any way resembling that of even high desert. Add to that the presence of the horse-normally a temporate zone animal-and the evidence would tend to indicate that the climate at the time the cave was occupied must have been temporate to cold. However, at this point, other evidence obtained seems to throw such a belief into a state of confusion. For example, there was the finding of the remains of the Chuckwalla Lizard, commonly found yet today in the lower Grand Canyon, living in a typical desert environment. There was also the shell of the Desert Tortoise, and certainly it is no cool climate dweller. To top it all off and thoroughly confuse the picture, the sloth dung was analyzed by Dr. Munz and Dr. Laudermild, both of whom are recognized authorities in the field of plant research. Both identified the plant fragments found in the droppings as belonging to plants found growing in the area today! Thus, the evidence produced by the test pit, while contributing much of value, also left the story of the cave, its occupants and when they lived, in a pretty badly muddled state.

But perhaps the picture isn't as unclear as it might appear. It just might be that conditions actually existed at the time the cave was occupied that would cause all these conflicting bits of evidence to fall into place. Directly across the canyon in front of the cave, and at several other places in the nearby region, are vast limy deposits on the slopes and overflowing the cliffs. These came from numerous springs and seeps. Without doubt, such an abundance of water can only mean that at some time in the geologic past likely quite recent as there are several of these springs in existence in the area yet today -the region was relatively moist, at least in the highland regions. This would very likely have meant heavy snows on the canyon rim country in the winter and fairly frequent rains in the summer. Probably the bottom of the Grand Canyon was beginning to feel the approach of the arid, desert climate that was soon to arrive. Under such conditions, the mountain goat, marmot and horse would have found an almost ideal environment in the upper canyon region in the summer and in the lower part of the canyon in the winter. Similarly, the sloths could have found life very acceptable. However, as the climate slowly changed in the highlands from cold and wet to temperate and relatively dry, and the canyon floor changed from temperate to low desert, the animal life was unable to completely adapt itself to those conditions. The horse, goat and marmot disappeared, while the sloth hung on into very recent time, living off of the type of vegetation that lies below the cave entrance today. This belief is borne out by the fact that in the upper three feet of the cave fill, the sloth remains outnumbered those of other species by a ratio of almost ten to one. Below three feet, the reverse was true with the sloth remains outnumbered. Likely it was during this period of climatic change that the desert type Chuckwalla Lizard became a cave fossil. It was also likely that the Desert Tortoise was added to the fossil list during this period. However, one thing is certain the tortoise did not climb the cliffs to enter the cave. Instead it was undoubtedly carried in, possibly by one of the big, hawl-like birds (its bones were found in the cave) that landed at the mouth of the cave upon occasion, there to fall prey to some predator, such as the bobcat (whose bones were also uncovered). The tortoise might even have been carried some distance to this point, possibly from the desert area that had developed just off the lower end of the Grand Canyon.

It is expected that some light may soon be shed on the age of the sloth dung of the cave, thus dating the period when the animal actually lived there. Not long ago, the cave was revisited. This furnished an oppor-tunity to collect some of the undisturbed dung and seal it in air-tight containers. This material was then sent away for a Carbon 14 test. If the materials collected can be used in this type of dating, they may furnish the answer to when all this took place. It wouldn't be at all surprising to find that sloths lived in the cave within the past 5000 years, or possibly less. It is also possible that early man may have lived in the area during the last years of the sloth's existence-and might even have had something to do with the ani-mal's disappearance-but thus far nothing has been found to prove such is true. The nearby Mauv Caves also contains some sloth dung, and some Indian artifacts, but the Indian materials are on top of the dung.While the existence of the sloth has been known for many years in various parts of the United States (one type was even described in 1797 by Thomas Jefferson, who was a scientist of note as well as a statesman), the find at Rampart Cave is one of the richest and added a wealth of knowledge. Located in a rather unaccessible part of the Grand Canyon in the Lake Mead National Recreation Area, it is one of the really valuable scientific treasures of the region. Because of its great research value, the cave is closed to entry today by a steel door, placed there by the National Park Service to protect its still unexcavated portions from possible loss through unauthorized digging or from a carelessly dropped match or cigarette. All this has happened because an Indian, with a keen interest and imagination, climbed a cliff to see what new archeological treasures he might find inside a very unimposing hole in the cliff.

The cave is rather large and roomy, capable of housing several of the huge animals at one time. In some places the ceiling is rubbed smooth by the passage of the sloths from one area to another.

The entrance to the cave is now barred by a steel gate to prevent destruction of the scientific materials inside. Permission to enter must be obtained from the Park Service at Boulder City, Nev.

The large deposits of sloth dung found in the cave indicate long use of cave by by the prehistoric sloths.