Mountain Goats, Condors, Equids, and Mammoths
We must never underestimate the patience of extinction.
Michael Rosenzweig, Win-Win Ecology:
How the Earth's Species Can Survive in the Midst of Human Enterprise
"Dammit, Bob! What are you dumping?" I was pissed. It was early in the morning, not my best time of day—and in June on Arizona standard time, mornings come very early. I was talking to Robert C. Euler, professor of anthropology at Prescott College, then Arizona's only private four-year nondenominational college. Wayne Learn, Bob's helicopter pilot, had just unloaded me and my gear on the floor of Marble Canyon, next to the surging Colorado River, 100 feet below the mouth of Stanton's Cave and 2,000 feet below the canyon rim. The view of the layered cliffs is spectacular, top down or bottom up, and I would see it both ways.
But on this June 1969 morning Bob and I were climbing up over talus littered with fresh "back dirt," the screenings discarded in the process of separating what would be bagged and saved by the field team. I eyed the back dirt with dismay. I had heard that archaeologists excavating desert caves for artifacts left the dung of extinct animals behind. Now I had caught one red-handed. The back dirt included rocks and pieces of driftwood, but it was mainly composed of ancient fecal pellets. Many were relatively large; at over half a gram in weight, they would prove to be more than twice the dry weight of those of mountain sheep or deer, but smaller than those of elk.
Appalled and outraged, I informed Bob in no uncertain terms that the pellets might well be those of Harrington's extinct mountain goat, which we (and Remington Kellogg before us) had also found in Rampart Cave. He was throwing away invaluable information. The samples would be ideal for radiocarbon dating and dietary analysis. "This is good shit!" I moaned. "You can't trash it!"
Fortunately for Bob, on the climb to the cave I was getting short of breath. Patiently he explained his procedures. His excavations were both modest and controlled. His trenches sampled only part of the cave floor, leaving a large volume of unexcavated fill for future investigators armed with new techniques and new questions. His field team methodically excavated and screened cave earth from 40-inch squares in two controlled trenches. All archaeological materials as well as bones of fish, reptiles, birds, and small mammals, along with seeds and other plant remains, were saved and bagged. In addition, his field crew sieved and saved dung pellets in a systematic fashion. Numerous rocks and boulders and abundant fossil driftwood made their work more difficult. They sampled the cave fill at 2-inch intervals from the surface down to 10 inches, and then at 10-inch intervals to the bedrock below. Pellets from deeper levels were often broken, and there were so many that Bob and his crew did not think they needed to save them all. I subsequently estimated that the cave contained roughly a million artiodactyl pellets.
Poor Bob. There he was, searching for precious artifacts, and what he was finding was mostly fossil goat shit. On top of that, when he invited a devotee of such stuff to see what he had found, he was ordered to save all of it. He might well have suggested that I find my own grant, helicopter, and field team. But whatever Bob, an ex-Marine officer, may have thought along those lines, he kept to himself. I cooled down slowly, perhaps influenced by the mellow rose-tinted illumination reflected into the cave from sun on the Redwall across the river. In the end, my colleagues and I were to gather much valuable data from Stanton's Cave, both on this trip and on a one-week return arranged by Bob in September 1970, of which I was delighted to be a part.
I wanted to know what animal had produced the large pellets. We concluded it was indeed Harrington's mountain goat, Oreamnos harringtoni, a fossil species related to the living mountain goat, Oreamnos amer-icanus. We based this conclusion largely on the bones associated with the pellets. According to Dick Harington (1984), extinct goats (and pos-
sibly living mountain goats) accounted for the majority of the 120 ungulate bones identified from the cave. (The other bones included those of bighorn sheep, bison, and two small species of Equus.) The most common artiodactyl bones and horn sheaths found at Rampart Cave were those of Harrington's goats. No other artiodactyls in the fossil fauna would have produced these pellets, which were larger than those of mountain sheep and smaller than those of elk. Since the time of Kellogg, those excavating Grand Canyon caves have commonly found these distinctive pellets associated with bones or horn sheaths of Harrington's goat. In the 1980s, Steve Emslie, Jim Mead, and Larry Coats explored the eastern Grand Canyon and found additional caves with numerous pellets of this size. Future investigators should be able to check this interpretation by DNA analysis.
Our Rampart Cave collaborators, Dick Hansen and Richard Clark, disagreed with us on identification of the pellets. They noted that small elk (wapiti, Cervus elaphus) voided similar pellets. Or they might belong to a poorly known extinct cervid, Navahoceros, whose bones are found occasionally in caves in western North America. No cervid bones, however, were found in Stanton's Cave. Indeed, I am unaware of any securely identified elk bones from any Grand Canyon cave (Szuter 1991). In any
case, living cervids rarely enter caves, and most of the caves in the Redwall would be inaccessible to them. Other than humans, the only large animals with climbing skills that might be equal to the challenge were mountain sheep and mountain goats. (Later in this chapter we will consider the mystery of how the bison bones got there.) I believe that the large fossil pellets can be assigned with confidence to the extinct goat. The smaller pellets, less than 0.25 grams in dry weight, might have been voided by immature Oreamnos harringtoni, by mountain sheep (genus Ovis), or by Rocky Mountain goats, which void much smaller pellets than did Harrington's goat. Mitochondrial DNA analysis should be able to resolve this question. But in the absence of their bones, I do not believe that any of the pellets found in Grand Canyon caves are attributable to cervids.
When did Harrington's goat last occupy Stanton's Cave? In Rampart and adjacent Muav Cave, Austin Long and I had estimated the time of extinction of ground sloths by dating samples from the top of their dung deposit (see table 5). With Bob Euler's help we could attempt the same thing here, separating out the large pellets to date the latest occurrence of the animals producing them. In the stratified pellet profiles, the large pellets last occur at about 8 to 12 inches below the surface, where they give way to smaller pellets, presumably of mountain sheep. The youngest sample of the presumed mountain goats was radiocarbon dated at 10,870 ± 200 (see lab catalogue number A-1155 in table 6). A sample of small pellets from the same level yielded a similar result, 10,760 ± 200 (A-1154). The youngest dates on goat pellets and horn sheaths at other sites also approximated 11,000 radiocarbon years ago (Mead, Martin, and others 1986). The youngest measurement, from Crescendo Cave in the Grand Canyon, yielded a date of 10,950 ± 70 (Emslie, Mead, and Coats 1995). Those numbers have a familiar look. The youngest pellets and horn sheaths of extinct goats (see table 6) are similar in age not only to each other but also to the youngest Shasta ground sloth dung at Rampart Cave (see table 5) (Long and Martin 1974).
Most of Jim Mead's data (Mead, Martin, and others 1986) were derived from horn sheaths, keratinous organic material akin to fingernails and toenails, ideal for an uncontaminated radiocarbon measurement. Mead's results ranged from 11,000 to 30,000 radiocarbon years ago, with at least one measurement in every millennium. Many samples comprised dung pellets (10 samples) or horn sheaths (24 samples) found on the surface of cave floors, mainly at Stanton's and Rampart. With rare exceptions, however, his samples could not be selected for youthfulness. He had to take them as they came, and a variety of ages was the result. In contrast, in the buried deposits of Stanton's Cave, we could target the last occurrence of large pellets using classic stratigraphy: the uppermost would be the youngest. The results were in accord with our measurements from Rampart Cave, where we had been able to concentrate on the top of a sloth dung deposit.
The concordance of dates on goat and ground sloth extinction (Mead, Martin, and others 1986) pointed to a common cause, a unique event around 11,000 radiocarbon or 13,000 calendar years ago. As will be discussed further in chapter 8, that was the time of the first well-documented and rapid appearance of prehistoric people, the mammoth hunters (C. V. Haynes 1993; Taylor et al 1996).
As with the ground sloths, we also obtained data on the extinct goat's diet. A Desert Lab student, Frances Bartos King, found no fossil pollen in the pellets, though fossil pollen was abundant in the cave earth. This suggests that the goats occupied the cave in winter, when no plants were in flower. In the summer, they probably migrated to higher elevations. It appears that, like the ground sloths at Rampart Cave, the goats did not occupy Stanton's Cave throughout the year.
Cuticle analysis of the plant remains in the pellets indicated that the
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