RAPTORS, RODENTS, AND PALEOECOLOGY: TESTING PALEOECOLOGICAL ASSUMPTIONS USING TAPHONOMIC DAMAGE PATTERNS AT HOMESTEAD CAVE, UTAH

Shifts in the composition and structure of non-volant small-mammal communities have long been recognized as important sources of information on past environmental change, particularly over the Holocene (past 10,000 years). Raptors (avian predators) are major contributors to the Holocene small-mammal subfossil record; concentrating mammal remains in rock-shelters by producing pellets rich in skeletal material. Such stratified accumulations of small-mammal remains represent valuable archives of faunal shifts over time-scales most relevant to conservation efforts (10² - 10³ years). Although shifts in small-mammal community composition through Holocene subfossil successions are often assumed to have been environmentally driven, similar shifts can be generated by changes in the raptor taxa responsible for concentrating the remains. Correct interpretation of the impact of Holocene environmental change on small-mammal communities thus requires a solid understanding of the taphonomy (formational history) of small-mammal death-assemblages.

Here I present a multivariate approach to testing the assumption of constant raptor identity through time. I show that assemblage-level skeletal damage patterns can be used to distinguish small-mammal death-assemblages created by owls from those created by diurnal raptors and mammalian carnivores. The persistence of these skeletal damage patterns through time supports the use of sub-fossil damage patterns for raptor identification. By applying this multivariate approach to the stratified Holocene sub-fossil mammal record from Homestead Cave, Utah, I am able to examine the temporal concordance between shifts in assemblage-level damage patterns and shifts in the composition and structure of the local small-mammal community to test the assumption of constant raptor identity over the formational history of this cave's deposits. Preliminary results indicate dominant occupation of the cave by owls throughout the Holocene. Such taphonomic analyses are important for disentangling environmental vs. taphonomic drivers of observed paleoecologically significant shifts in the local small-mammal community through time.