Canyon Dwellers During the Ice Age and Since

We all have known for a few decades now that during the Ice Age (11,000 years ago back to about two million) the extinct Harrington mountain goat (Oreamnos harringtoni) was the predominant large canyon dweller. It lived from rim to river, east to west. Its remains are found in almost every cave, all except those located on the sheer face of the Redwall. It was a most ardent cliff climber—far better than the bighorn sheep (Ovis) and certainly more adept than the deer (Odocoileus) or the awkward wapiti (elk, Cervus). Only condors, vultures, owls, and ravens could out-do the mountain goat—and they could fly. But there are other critters that lived in the Canyon.
The mosaic, the construct, of animal communities is ever changing; never the same. Can our views, conclusions, and sustainability laws keep up with these constant alterations? What we have studied is patchy in distribution; in other words, biased. What we do understand—or think we know—are the fossil deposits within the river corridor of the upper, say, 50 river miles (rm). Unfortunately, it is rare to have a comprehensive knowledge of deposits up and away from the effects of the river corridor. The deposits are less well known from rm 50 to 100. From there to rm 274 we understand just about zippo; about 170 miles of corridor, associated side canyons, and rimming plateaus are terra incognita (unknown lands) for Ice Age fossils. We do have a pretty good understanding of the last four miles of corridor as the River readies to jettison (now ooze) from the Colorado Plateau at the Grand Wash Cliffs.
I began my search for the Ice Age animals of the Grand Canyon in 1974—thanks to Paul Martin. What little we know today stems from thirty years worth of work. Recently a new wave of prospecting and discoveries has materialized. Grand Canyon National Park, Grand Canyon-Parashant National Monument, and Lake Mead National Recreation Area realize that they need assistance in locating and assessing their fossil resources—our natural heritage. Teamwork is required with this vast land.
Larry Coats, Steve Emslie, and I have examined dried deposits well out of the river corridor in the eastern Grand Canyon. A tooth of the extinct camel (Camelops; not related to the living camels) radiocarbon dated to 16,000 years old. This is detailed in a chapter in the new book, Ice Age Cave Faunas of North America (Indiana University Press). Related to this is Coats’ detailed report about the changes in vegetation going back about 46,000 years. Occasionally bones of the extinct shrubox (Euceratherium; relative of the living muskox) are being recovered in relatively flat plateau areas that have easy access from the rim.
The keratinous horn sheaths of the bighorn sheep have been recovered from a number of dry deposits. Radiocarbon dating minute fragments (the size of a match head) of these treasures illustrates that the bighorn and Harrington mountain goat co-existed for at least 10,000 years along the river corridor. It is not understood if it was the glacial climates that corralled the bighorn in the warmer Inner Gorge 11,000–20,000 years ago or if it was out-competed (restrained) by the well-established Ice Age horse (Equus; a small species like the burro) and Harrington mountain goat. My studies of the dung of the Harrington mountain goat indicate that its diet was very similar to that of the living bighorn sheep. The nps concluded years ago that the burro introduced by the miners had a diet similar enough to that of the native bighorn that they were both in competition for the same food resource—hence why the invading burro was removed. The diet of the Ice Age burro may have been similar. It appears to me that the bighorn has filled all available niches vacated by the extinction of the Ice Age horse and Harrington mountain goat 11,000 years ago. Extinction of one species can lead to expansion of another.
Sandy Swift (nau Laboratory of Quaternary Paleontology) has located a wealth of information left by a little carnivore, the ringtail (Bassariscus). This new data set is recovered by screen washing 6,900-year-old dung deposits through 500-micrometer mesh sieves (1 mm mesh was way too big). She found that bones of the nocturnal banded gecko (Coleonyx) were common. She also retrieved the first fossil record in the Grand Canyon of the desert iguana lizard (Dipsosaurus), blind snake (Leptotyphlops), shovel-nosed snake (Chionactis), and frogs (Hyla and Bufo). The ringtail was preying on these critters in the wide, sandy, riparian community bordering the Colorado River in the western-most four miles of the corridor—an area not thoroughly studied prior to being inundated by the rising Lake Mead reservoir in the 1930s.

Mary Carpenter (nau Laboratory of Quaternary Paleontology) has finished her study of the vertebrate fossils collected by the Smithsonian Institution from Rampart Cave (rm 274) in the 1930s and ’40s. Although famous for its copious amount of dung produced by the extinct Shasta ground sloth (Nothrotheriops), the cave also contains a wealth of information about Ice Age bighorn sheep, tortoises (Gopherus), Harrington mountain goats, condors (Gymnogyps), black vulture (Coragpys; this species not in Canyon today), other birds, and among all things, vampire bats (Desmodus).
Bison (Bison)—the American buffalo, icon of the prairies and mid-West in the 1800s—is an interesting problem for the Grand Canyon land managers. A state herd is sneaking onto national park lands along the North Rim country (without a permit no less). It should do well on grassy, even patchy, open woodlands, forests, and plateau tops. Although considered a “good climber,” it will be difficult for it to go down to the river corridor. The bison will not do well in regions with really hot summer temperatures. These temperatures and availability of water will likely be its constraints.
Is it a newcomer or just a reminder from the past? We know that during the Ice Age climates it lived along the rims and likely was able to get to the river a few places within Marble Canyon. Maybe the Ice Age bison was removed when the horse, Harrington mountain goat, and scavenging condor were forced out of the Grand Canyon by changing community structure, climate, and the arrival of hot summer temperatures. Beginning about 8,000 years ago, much of the Grand Canyon and surrounding plateaus became marginal habitats for the bison. Were bison completely eradicated, living only to the south, north, east, and west of the Grand Canyon? Part of the problem is that we have not adequately prospected those areas that could have supported a marginal population (for instance on the Sanup Plateau). Bison are known from archaeological localities in the Grand Canyon region. Maybe these were locally procured, or alternatively, brought in (traded in) as a “foreign product.” We don’t know enough yet, but we do know there is a huge area of potentially suitable habitat yet to search. Land managers and ecologists fully understand that bison do modify meadows today (wallow pits and trails)—just as they did years and years ago. Another complication is that the invading bison of today is utilizing a slightly different habitat with a slightly more stressful climate than the bison did during the late Ice Age or even since. The issue is complex. I would think that any bison that cannot make a living in the Grand Canyon today would be a welcome dinner or two for the reintroduced condor.
We still do not fully understand when the wapiti first showed up along the Grand Canyon, but subfossil data imply that it was very recently. And, talk about recent…the peccary (the wild javalina; Tayassu or Pecari) is just now moving into the Grand Canyon. This introduction appears to be natural, allowed by the overly warm winters that we have experienced over the past 5–10 years.
I hope the reader realizes that the animal communities of the Grand Canyon region are dynamic—an ever-changing mosaic of species. Extinction and expansion are not necessarily an “event” but a “process” over time. As precipitation, seasonality of precipitation, and temperatures change, species of animals react individualistically to this either by disappearing (dying) or migrating (either expanding or retreating). As more areas open up as suitable habitat, then through time those areas are filled, first by vagrant explorers then by colonizers. The dry environment and the enormous number of caves and shelters have preserved an unusually detailed record of the changing animal communities in the Grand Canyon. We still have a lot to learn about a record worth assessing and preserving.

Jim I. Mead
Department of Geology, and Quaternary Sciences Program, nau