NATURAL TRAPS, SHELTERS, OR PREDATOR DENS: WHY ARE PLEISTOCENE FOSSIL PRONGHORN (MAMMALIA: ANTILOCAPRIDAE) FOUND IN CAVES?

ABSTRACT:

We examine the Pleistocene record of fossil pronghorn (Mammalia: Antilocapridae) bones found primarily in caves throughout the Intermountain West of the United States and Mexico, but also in Florida, noting the different species present and their distribution in time and space. We briefly review the development of a framework for investigating the taphonomy of vertebrate fossils in caves. We review previously published explanations for pronghorn fossils found in caves and karst features. We then examine population structures, taphonomic factors, preservation biases, and abun- dance to identify patterns in the record that can resolve those different explanations. We focus on Pleistocene (Ice Age) sites known from Arizona, Colorado, Florida, Nevada, New Mexico, Texas, Wyoming, and in Mexico for the broader per- spective, and on 4 species of pronghorn from late Pleistocene (Rancholabrean) cave sites for a narrower perspective. The taxa include: the extinct Stock’s pronghorn Stockoceros conklingi from Papago Springs Cave in southern Arizona, Shelter Cave and Muskox Caves in New Mexico and San Josecito Cave in Nuevo Leon, Mexico; the dwarf pronghorn, Capromeryx furcifer from multiple sites; an older species of dwarf pronghorn, Capromeryx arizonensis, from the early Pleistocene Inglis 1A site in Florida; and the extant pronghorn Antilocapra americana from Natural Trap Cave in Wy- oming. We conclude that pitfall deaths account for those caves with large numbers of pronghorn fossils, while caves with smaller numbers of specimens are likely the result of carnivore activity, scavenging activity by rodents, or sporadic habitation by pronghorn.