Measuring Foraging Efficiency with Archaeological Faunas: The Relationship Between Relative Abundance Indices and Foraging Returns

In western North America, models from foraging theory have been used to address subsistence change using archaeological faunas. Several studies have argued that return rates from foraging declined in a variety of late Holocene contexts and support this position by applying a method involving the computation of a relative abundance index (AI) of large bodied animals to the sum of large and small ones. We present the results of a series of computer simulations devised to identify the relationship between changes in such indices and changes in a forager's average return rate and discuss the implications of these simulations in light of our current work in the Little Boulder Basin Area of north-central Nevada. These include, (1) the importance of using knowledge of both post-encounter return rates and changes in AI s to make inferences about changes in overall return rates; (2) the fact that there are good reasons to expect AI values to be low; and (3) what factors might contribute to the high AI values observed at archaeological sites.