Brown, Oliver, Judith Field and Mike Letnic (University of Sydney)

Variation in the Taphonomic Effect of Scavengers in Semi-Arid NSW Linked to Rainfall and the El Niño Southern Oscillation (ENSO)

Scavenging is one of the primary taphonomic processes shaping the final composition of faunal assemblages, and it must be understood if we are to accurately reconstruct palaeofaunas and pre-historic human subsistence. We have conducted a 4 year study in semi-arid NSW to investigate the relationships between ENSO, variable rainfall and scavenging on medium-large mammal carcasses (6 kangaroos, 2 emus and 4 pigs; in 5 experimental periods). Following periods of above average rainfall (coincident with the La Niña phase of ENSO) there was an increase in primary productivity and subsequent increases in the abundance of most species. Following below average rainfall (coincident with the El Niño phase of ENSO), resources diminished, leading to a greater importance of carrion for facultative scavengers such as pigs and foxes, and an increase in their scavenger-effect on experimental assemblages. Other species (e.g. ravens, eagles, goannas) also probably scavenged with an increased intensity. Essentially, scavenging is greater during times of drought and other types of ecosystemic stress. Many archaeological faunal assemblages in Australia will have been formed in ways that mirror experimental circumstances in which most faunal remains are removed by scavengers. However, because Australia has such a variable climate, the impact of scavengers on faunal assemblages will also be variable. Therefore, taphonomic analyses will require that palaeoecological and palaeoclimatological data in the archaeological record be integrated with the results of ecologically informed actualistic research.

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