The Floating Island Cave mammals: Paleoecology, abundance indices, and human subsistence through a taphonomic lens

Abstract

Analyses of mammal remains from middle and late Holocene deposits in Floating Island Cave on the arid floor of the Bonneville basin in western North America are presented. Identified specimens consist of various desert mammals, especially leporids, which mirror collections from neighboring sites and provide additional data for one of the most comprehensive Holocene zoogeographic histories in the world. Taphonomic analyses identified large- and especially small-bodied mammal bones that were deposited by both human and non-human predators. Most horizons contained unusually high proportions of burned bones which are often viewed as unambiguous indicators of human subsistence activities. However, analyses of the cave’s deposits and the numbers and extent of burned bone indicate many specimens were charred in situ by post-depositional burning of the dry vegetal-rich fill. We employed abundance index measurements comparing artiodactyls against smaller leporids to investigate potential changes in human subsistence. We calculated two indices to illustrate the effects of non-human bone accumulations on abundance measures; one encompasses only specimens identified to genera and the other discounts scatological bones and other non-human accumulations and includes only bones and bone fragments classified as cultural refuse. When discounting the hundreds of leporid bones deposited by non-human vectors, the analyses show that the remains of leporids (especially hares [Lepus sp.]) are appreciably more abundant than artiodactyls, even during late Holocene periods of increased moisture. Given the dominance of Lepus in regional archaeological collections we argue that hares were not a low-ranked prey item but a low-risk dietary staple pursued throughout Holocene human occupation.