Exploring the use of stable carbon isotope ratios in short-lived leporids for local paleoecological reconstruction

Most ecological proxies used in archaeological research operate at scales that are too coarse-grained for consideration of huntergatherer adaptive decisions. Hunter-gatherers adapt to local ecological conditions and short (e.g. seasonal, yearly) time frames. Our goal is to develop proxies to identify ecological shifts at fine-grained temporal and spatial scales for archaeological research. We use stable carbon isotope ratios (δ13C) in bone collagen from 58 modern leporids from two distinct ecological areas in the American Southwest as a proxy to reconstruct vegetation and climate patterns at fine-grained scales. Higher δ13C values in collagen of cottontail (Sylvilagus sp.) and jackrabbit (Lepus sp.) collected in the northern Chihuahuan Desert of New Mexico and West Texas suggest a more C4/crassulacean acid metabolism (CAM) dominated local vegetation when contrasted to samples from Kerr County in Central Texas. Comparisons of temperature and precipitation patterns between the two areas, along with vegetation data, suggest that key ecological differences, reflected in the collagen isotopic compositions, are likely related to rainfall amounts and the type of green forage available to leporids, especially during winter months. Leporids in dry areas may be relying on CAM plants, including prickly pear, which has a C4 isotopic signature. Alternative resources are likely to be available in wetter areas such as Central Texas.