Assessing the use of stable isotope values from deer antlers as proxies for seasonal environmental variations

Abstract

Stable isotope analysis is used in archaeology for nutritional, environmental, and forensic studies. Additionally, the use of oxygen, carbon, and nitrogen isotope analyses of faunal bone samples can provide information reflective of past environmental conditions. White-tailed deer (Odocoileus virginianus) antlers, although found in many archaeological assemblages, remain underutilized as paleoenvironmental proxies. Here we assess their feasibility to serve as archives for past year around seasonality by analyzing both apatite (δ13C, δ18O) and collagen (δ13C, δ15N) for stable isotope values of white-tailed deer antlers from four modern samples collected in central Iowa, USA (PEL-0090, PEL-0114, PEL-0164, PEL-0165). These samples are then compared with local environmental data (precipitation, relative humidity, and temperature) from their respective years of death and location. Because antlers develop from early spring to late summer in Iowa, they may serve as an archive for intra-annual seasonal variations and provide snapshots for past weather conditions. Results from antler PEL-0114 exhibit no correlation between stable isotopes and environmental variables. δ18O shows a strong direct and weak indirect correlation with precipitation and relative humidity only for antler PEL-0090, respectively. δ13Capatite shows strong indirect correlations with temperature for PEL-0165 and weak indirect correlations with relative humidity for PEL-0090 and PEL-0164. While antler PEL-0090 δ15N exhibit strong indirect correlations with temperature and antler PEL-0164 δ15N exhibit indirect correlations with precipitation. Mixing of C3 (carbon fixation pathway that converts CO2 into an organic compound) and C4 (carbon fixation pathway that forms four carbon compounds from phosphoenolpyruvate to liberate the CO2 as a C3 pathway) dietary consumption might interfere between δ13Ccollagen correlation with climatic variables. Therefore, this method can help relate behavioral ecology to important past human events. However, potential complications with the method include physiological mechanics of antler growth, the ingestion of water and food from various sources by the deer, and the age of the specimens.