Bears and Man at Porcupine Cave, Western Uinta Mountains, Utah [Ours et homme dans la grotte de Porcupine, montagnes Uinta occidentales].

Résumé

Porcupine Cave is located at an elevation of 2800 m in a steep glacier-cut valley in the western Uinta Mountains of Utah. The cave was discovered in 1960 by Dale J. Green and John F. Haman of the National Speleological Society who cleared rubble from a tight 12 m long horizontal crawlway to gain entry. Beyond this crawlway a larger dirt-filled passage called the Bridge Junction (2 m wide and 2 m high) slopes downward into the deeper parts of the cave. In this passage, 25 m inside the cave, Green and Haman collected a juvenile maxilla and adult cranium of black bear (Ursus americanus UUMZ 22360-22361) and found what appear to be bear claw marks on the cave walls. The dirt fill ends 30 m inside the cave, and the passage beyond is littered with earthquake-shattered speleothems. This passage is horizontal and leads to a large room (10 m wide and 14 m high) full of breakdown blocks. In this room Green and Haman found a pair of sub-adult grizzly bear dentaries (U. arctos UUMZ 22362) 65 m inside the cave, and the room was named the Bear's Den. These bones were donated to the University of Utah Museum of Zoology and identified by Stephen D. Durrant. The cave was mapped and described in a private publication (Haman 1963). In 1986 I collected additional material at the Bridge Junction. The soil there, which came in from the cave entrance, is composed of fist-sized angular limestone cobbles in a clay and organic matrix partly covered with decaying sticks, roots, and bones. This soil slopes 20ø and appears to be disturbed from slumping. The room was carefully mapped, and bone (now at Brigham Young University) was collected from the upper 0.2 m of soil. The rest of the juvenile black bear skull was recovered, as was about half of its skeleton (BYUVP 9960). Bones of this animal were disarticulated and widely scattered. At least two adult black bears were represented by two left maxillae, an upper canine, thoracic vertebra, metacarpal, calcaneum, and claw (BYUVP 9961-9967). In addition to bears, a suite of boreal mammals and birds typical of the Uinta Mountains was found. The 43 bird bones (BYUVP 9855-9897) have not been identified. Of small mammals I recovered 2 jaws of snowshoe rabbit (Lepus americanus), 24 of marmot (Marmota flaviventris), 16 of northern pocket gopher (Thomomys talpoides), 3 of bushy-tailed wood rat (Neotoma cinerea), 7 of porcupine (Erethizon dorsatum), 2 of pine marten (Martes americana), 1 of long-tailed weasel (Mustela frenata), and 1 of striped skunk (Mephitis mephitis BYUVP 9898-9959). Of artiodactyls Ifound 2 phalanges of wapiti (Cervus elaphus), 15 bones of mule deer (Odocoileus hemionus), and a metacarpal probably of bison (Bison bison BYUVP 9968-9985). The bones were coated with wet clay, and some were heavily gnawed by rodents. Several artifacts have been recovered from Porcupine Cave. Haman (1963) reported finding a white quartzite arrowhead (3 cm long and 2 cm wide) in the entrance crawlway. I found a tan chert elko series point (10 cm long and 5 cm wide) at the Bridge Junction. It was on the surface near the bottom of the soil fill its broken tip was 1.5 m lower on the slope. Some charred, water-soaked wood was also found in the soil. A femur of the juvenile black bear was C-14 dated at 510 +/- 75 yr B.P. (GX-13292). This date suggests that this fauna (recovered near the cave entrance) and its associated artifacts are very recent. In 1987 I collected additional bones of the grizzly bear in the Bear's Den including skull fragments and an assortment of postcranial elements. Rock fall appears to have damaged some bones and buried others. Dripping water kept these bones wet and deposited calcite on some, and some are heavily gnawed by rodents. A group of ribs was C-14 dated at 10,620 +/- 245 yr B.P. (GX-13676). This is an early date for grizzly bear, which immigrated from Asia in the late Wisconsin, but it has been