The Late Pleistocene and Holocene Fauna and Flora of Vulture Cave, Grand Canyon, Arizona

Abstract

-Fifteen packrat middens and a ringtail refuse area were recovered and analyzed from Vulture Cave, western Grand Canyon, Arizona. Nineteen radiocarbon dates indicate that packrats inhabited the cave as early as 30,000 B.P. and persisted there throughout the Wisconsinan full and late glacial. No deposits were found which indicate that Neotoma lived in the cave from 11,000 to 2,000 B.P. Only one Holocene age (1,000 B.P.) packrat midden was dated from the cave. Forty-seven plant taxa were identified from the cave deposits. Extralocal species accounted for 28% of the total fossil flora while species still present in the local community accounted for 57%. Thirty-seven animal taxa (19 reptiles, 3 birds, and 15 mammals) were identified from the cave deposits. The long temporal depth of the Vulture Cave deposits has provided the only late Wisconsinan maximum and pre-maximum plant and animal community assemblage so far reported from the Grand Canyon. The development of the analysis of fossil packrat middens in the last 15 years by Wells (Wells and Jorgensen, 1964; Wells and Berger, 1967) and Van Devender (Van Devender, 1973, 1977), among others, has provided a needed source of paleoenvironmental information for desert regions seldom available through conventional pollen analysis. Midden analysis in the Southwestern deserts is predominantly a record of pinyon-juniper and juniper woodland invasion of the deserts during the most recent Ice Age. Fossil packrat middens occur in great abundance within the dry limestone caves and crevices of the Grand Canyon (Fig. 1; Phillips and Van Devender, 1974; Van Devender and Mead, 1976; Phillips, 1977). Rampart Cave (Colorado River Mile 275, conventional usage), well known for its unique stratified deposit of dung of Nothrotheriops shastense (Shasta ground sloth), also contains a thick unconsolidated packrat midden seam along with several isolated cemented middens. Phillips (1977) analyzed and radiocarbon dated 35 middens from Rampart Cave, Vulture Cave, and isolated rock crevices in nearby canyons. His record indicates a juniper-shadscale-single leaf ash woodland 1,000 m lower than present woodland communities, presumably the local vegetational response to the climate of the most recent Ice Age. This paper is a report of the ancient fauna and flora of Vulture Cave, a particularly rich midden location discovered in the course of our survey for packrat middens and sloth caves in the lower Grand Canyon. Vulture Cave was chosen for study because it contains the largest number of packrat middens from a single locality and provides the longest temporal depth of a series of packrat middens from a single fossil site. Previous packrat midden studies have centered upon the analysis and reconstruction of past environments based predominantly upon the fossil flora. Few midden studies have dealt with fossil vertebrates in association with the reconstructed floral communities (Van Devender et al., 1977; Van Devender and Mead, 1978). 'Contrib. No. 818, Dept. of Geosciences, Univ. of Arizona, Tucson. THE SOUTHWESTERN NATURALIST 26(3):257-288 AUGUST 21, 1981 This content downloaded from 207.46.13.13 on Fri, 26 Aug 2016 04:18:34 UTC All use subject to http://about.jstor.org/terms The Southwestern Naturalist 0 ' 80 t* KM * Rampart, Vulture, Muav Caves * Packrat midden localities A Stanton's Cave GRAND CANYON, ARIZONA FIG. 1.-Map of the Grand Canyon showing the positions of Vulture Cave and other fossil localities. PACKRAT MIDDENS.-Packrats or woodrats (Neotoma spp.) gather a great variety of materials (seeds, twigs, needles, leaves, teeth, bones, etc.) for use as food and structural components of the den (Finley, 1958). Materials are collected within the home range of the packrat, usually within a radius of 100 m from the den (Bleich and Schwartz, 1975; Stones and Hayward, 1968). Periodic cleaning of the den by the packrat produces a midden of discarded waste material which may become hard and cemented (indurated) through trampling and urination. If wastes are deposited in a vertical crevice, the resulting midden does not always accumulate following the laws of superposition. However, if the midden is developed on a more or less horizontal surface, the deposit can be as finely bedded as a layer cake. A midden located in a protected dry rock crevice or cave will last as long as the shelter exists. Ancient packrat middens contain many well-preserved plant fragments which usually can be identified to species, providing a detailed local flora for each site (Phillips, 1977). Approximately 300 species of plants have been identified from middens in arid North America (Van Devender, 1977). Bones, teeth, insect fragments, and fecal pellets also are well preserved in the middens. Although faunal remains have not yielded as much information on range and climatic change as have floral remains, ancient middens do provide an unusual opportunity to recover faunal and associated floral fossils from the same deposit. Macrofossil records of the flora and fauna along with a radiocarbon date obtained on an extralocal plant taxon from a single midden layer provide a basis for reconstruction of the local Pleistocene environment (Van Devender et al., 1977; Van Devender and Mead, 1978). SITE DESCRIPTION.-Vulture Cave, elevation 645 m (Fig. 1), is a small limestone cave in the Spencer Canyon member of the Cambrian Muav Formation. Three major conduits (West, Middle, and East tunnels) merge to form a large room (Entrance Room-Fig. 2) which opens to the surface near the base of the cliff-forming limestone member. A talus slope extends from the cave entrance down a short side tributary to the confluence with the major portion of Vulture Canyon. The present inconspicuous entrance to Vulture Cave is actually a series of voids in and around angular boulders, with only one space large enough for human entry. The large blocks are breakdown from the formation's overhanging wall. Inside the cave are large rectangular limestone blocks that have broken loose from the ceiling and have fallen a meter or more onto the floor. These blocks form the major partitions between the Entrance Room and the three tunnels. Since the middens lie undisturbed atop and beside the blocks, it appears that the blocks fell prior to occupation of the cave by packrats. The Entrance Room floor is predominantly of exposed limestone, with occasional floor depressions filled with eolian sediments and loose packrat debris. In this room the packrat middens are 258 vol. 26, no. 3 This content downloaded from 207.46.13.13 on Fri, 26 Aug 2016 04:18:34 UTC All use subject to http://about.jstor.org/terms VULTURE CAVE GRAND CANYON NATIONAL PARK ARIZONA r; : 1 i 1 ' I I . l , l , l ' , ' , ', ' , ' ,Packrat midden 8 number r7 I ', ] Z t , i x,,,,,,,,,, Subfloor midden. .