Variation in the taphonomic effect of scavengers in semi-arid Australia linked to rainfall and the El Nino Southern Oscillation

Scavenging is one of the primary taphonomic processes shaping the final composition of fossil faunal assemblages. The taphonomic effect of scavengers is variable and must be understood in the context of the causes of that variation. In this study, we investigated relationships between the El Nino Southern Oscillation (ENSO), variable rainfall and scavenging on 20-40 kg mammal carcasses in semi-arid New South Wales over four years. Following periods of above-average rainfall (coincident with the La Nina phase of the ENSO), there was an increased availability of non-carrion food and scavenging activity was moderate. Following below-average rainfall (coincident with the El Nino phase of the ENSO), foraging options diminished, leading to a greater importance of carrion in the diet of scavengers and a resultant increase in carcass disturbance, transport and destruction by scavengers. Feral pigs (Sus scrofa) and red foxes (Vulpes vulpes) were the most taphonomically significant scavengers in the study. Australian ravens (Corvus coronoides) and wedge-tailed eagles (Aquila audax) were active scavengers throughout the period of the study, but had little impact on bone survival. Lace monitors (Varanus varius) also fed mostly on soft tissue and were only present seasonally. We found that climate variability in the form of short-term oscillation can result in significant variation in the impact of scavengers on carcasses and may be an important consideration when evaluating site formation scenarios and biases in fossil faunal assemblages. Copyright (c) 2006 John Wiley & Sons, Ltd.