New Mexico Geological Society Annual Spring Meeting — Abstracts

In April 2002, a field crew consisting of paleontologists, cave specialists, and volunteers from the New Mexico Museum of Natural History (NMMNH), Carlsbad Caverns National Park (CCNP), and Kartchner Cavems State Park in Arizona, conducted excavations of the fossiliferous Pleistocene bat guano deposits in Slaughter Canyon Cave (also known as New Cave) in CCNP, Eddy County, southeastern New Mexico. We collected 21 bags of sediment (~300 kg) from two test pits in different arcas of the cave. Test Pit 1 is ~2 m deep by 1 m wide; Test Pit 2 is ~1 m deep by 1 m wide, The soft, unconsolidated guano deposits are overlain throughout the cave by a thin (~10-15 cm thick) multilayered flowstone deposit. We excavated the sediments from the vertical walls of trenches (some up to ~5 m deep) left behind by miners who dug the guano for fertilizer. Because most of the fossils consist of tiny bat bones, the sediments were carefully excavated and placed into nylon bags for transport to the NMMNH for screenwashing and sorting.

Except for the description of the extinct free-tailed bat Tadarida constantinei, little paleontological research has been conducted in Slaughter Canyon Cave. The vast majority of fossils from this cave, numbering in the thousands of bones, belong to Tadarida constantinei. This species is very similar to the living Mexican free-tailed bat Tadarida brasiliensis but is ~20% larger in most measurements. Other fossil samples of a large Tadarida that may be referable to T. constantinei are known from Mammoth Cave in Kentucky and Hamilton Cave in West Virginia, both of which are medial Pleistocene (Irvingtonian) age. T. brasiliensis forms large colonies in caves throughout the southwestern US, including the main cave at Carlsbad Caverns. The tremendous abundance of T. constantinei fossils in Slaughter Canyon Cave strongly suggests that this extinct species also formed large colonies. Ten other species are represented in the Slaughter Canyon Cave vertebrate fauna: desert tortoise Gopherus agassizi, lizard, snake, large raptorial bird; the bat Myotis, desert cottontail rabbit Sylvilagus auduboni, the pocket mouse Perognathus, the woodrat Neotoma, extinct pronghorn antelope Capromeryx minor, and a large carnivore-possibly the short-faced bear Arctodus simus. Previous attempts to radiocarbon date the guano and fossil bat bones from Slaughter Canyon Cave have proven unsuccessful, suggesting these deposits are older than 40,000 years Before Present.