Interpreting abundance indices: Some zooarchaeological implications of Martu foraging

Indices of taxonomic abundance are commonly used by zooarchaeologists to examine resource intensification, overexploitation and gender-divisions in foraging labor. The original formulation of abundance indices developed a clear interpretive framework by linking the measure with foraging models from behavioral ecology. However, using the same basic tenets of behavioral ecology, archaeologists disagree about how to interpret variability in abundance index values: some suggest that high proportions of large prey remains represent higher overall foraging efficiency, while others argue the opposite. To help solve this problem, we use quantitative observational data with Martu hunters in Australia's Western Desert to examine how foraging decisions and outcomes best predict variation in the abundance index values that result. We show that variation in the proportional remains of large to small game is best predicted by hunting bout success with larger prey and the time spent foraging for smaller prey. A declining abundance index results from decreasing hunting success with larger prey, increasing time invested in hunting smaller prey, or both; any of which result in a lower overall return rate than if large prey were acquired reliably. We also demonstrate that where large prey acquisition is stochastic, high index values are correlated positively with men's proportional caloric contribution of large unreliable game, while low index values are correlated with women's proportional foraging time for small reliable game. We discuss these results with reference to evidence of resource intensification and gender-specific foraging.