Open Journal of Archaeometry 2014; volume 2:5306 [Open Journal of Archaeometry 2014; volume 2:5306] [page 81] Exploring the use of stable carbon isotope ratios in short-lived leporids for local paleoecological reconstruction Stephen Smith, 1 Raymond Mauldin, 2 Cynthia M. Munoz, 2 Robert Hard, 1 Debajyoti Paul, 3 Grzegorz Skrzypek, 4 Patricio Villanueva, 5 Leonard Kemp 6 1 Department of Anthropology, University of Texas at San Antonio; 2 Center for Archaeological Research, University of Texas at San Antonio, TX, USA; 3 Department of Civil Engineering (Geosciences), Indian Institute of Technology, Kanpur, India; 4 West Australian Biogeochemistry Centre, School of Plant Biology, The University of Western Australia, Crawley, Australia; 5 Department of Geology, University of Texas at San Antonio, TX; 6 Geo-Marine, El Paso, TX, USA Abstract Most ecological proxies used in archaeolog- ical research operate at scales that are too coarse-grained for consideration of hunter- gatherer 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 (δ 13 C) 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 δ 13 C values in col- lagen of cottontail (Sylvilagus sp.) and jackrab- bit (Lepus sp.) collected in the northern Chihuahuan Desert of New Mexico and West Texas suggest a more C 4 /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 col- lagen isotopic compositions, are likely related to rainfall amounts and the type of green for- age available to leporids, especially during winter months. Leporids in dry areas may be relying on CAM plants, including prickly pear, which has a C 4 isotopic signature. Alternative resources are likely to be available in wetter areas such as Central Texas. Introduction Reconstructions of past ecological condi- tions in archaeological research often rely on proxy data, such as shifts in pollen frequen- cies, which operate at variable spatial and tem- poral scales. While appropriate for many con- cerns, most ecological proxies operate at scales that are too coarse-grained for consider- ation of human adaptive decisions. Hunter- gatherers and agriculturalists adapt to local rather than regional ecological conditions, and to changes that occur on a seasonal or yearly time frame, not shifts that happen over cen- turies (Winterhalder and Leslie, 2002). Arch- aeologists need to develop high-resolution eco- logical proxies that operate at scales that are coterminous with those used by humans in making adaptive decisions. In this paper, we explore the use of stable carbon isotope ratios (δ 13 C) of bone collagen in cottontails (Sylvilagus sp.) and jackrabbits (Lepus sp.) as potential high-resolution prox- ies to reconstruct vegetation and climate pat- terns at short-term temporal and spatial scales. We have used samples from an archaeological assemblage from Texas, USA to monitor eco- logical shifts (Munoz et al., 2011; Kemp, 2008) and are currently investigating other archaeo- logical assemblages in the American Southwest. We focus on refining the applica- tion through a comparison of δ 13 C values in bone collagen (δ 13 C collagen ) of leporids from two distinct ecological settings. δ 13 C values of mod- ern leporids collected in southern New Mexico and West Texas (n=26) suggest that these areas have a stronger C 4 /CAM signature rela- tive to those collected in Kerr County in Central Texas (n=32). Comparisons of temper- ature and precipitation patterns between the two areas, along with vegetation transects data, suggest that key ecological differences reflected in the collagen are likely related to rainfall amounts and the type of green forage available to leporids, especially during the win- ter months. As a paleoecological proxy, leoprids have several advantages. Jackrabbit and cottontail diets incorporate a variety of plants, with grasses, forbs, shrubs, and succulents con- sumed in response to availability, growing con- ditions (i.e. temperature, rainfall, and plant dormancy), and moisture content. Analyses of the stomach contents of Lepus collected in southern Arizona (Vorhies and Taylor, 1933) suggest a seasonal preference for grasses in the spring and midsummer, following rains. As grass production declines in early fall and win- ter, rabbits concentrate on browse consisting primarily of mesquite (Prosopis glandulosa). Cactus, such as prickly pear (Opuntia sp.) and cholla (Echinocereus fendleir), are more heav- ily consumed during drier months. Similar seasonal trends, with grasses preferred in the late spring, summer, and early fall, forbs and shrubs in the fall and winter, and shrubs and succulents in winter and early spring are reported for jackrabbits in a variety of regions (Best, 1996; Currie and Goodwin, 1966; Fatehi et al., 1988; Hayden, 1966; Hoffman et al., 1993; Correspondence: Cynthia M. Munoz, Center for Archaeological Research, 1 UTSA Cir, University of Texas at San Antonio, San Antonio, 78249 TX, USA. Tel./Fax: +1.210.458.4397. E-mail: cindy.munoz@utsa.edu Key words: carbon isotopes, paleoecological reconstruction, leporids. Acknowledgements: thanks to Richard Doucett and Melanie Caron [Colorado Plateau Analytical Laboratory, Nothern Arizona University (NAU), Flagstaff, AZ], to Bruce Moses who drafted the figures for this manuscript, and to the Center for Archaeological Research - The University of Texas at Sant Antonio (CAR-UTSA) staff. Kevin Daiber, Kelly Denham, and Lynn Wack of CAR helped with sample preparation. Thanks to Heath Garner of the Texas Tech University Museum (Lubbock) and Dr. Robert Baker, National Science Research Laboratory, at Texas Tech for graciously allowing us to sample their modern faunal collections. Bryant Saner provided addi- tional modern specimens. Thanks to Dr. Mark Pollard (Archaeological Science Research Lab for Archaeology, University of Oxford) for reviewing this manuscript and to Robert Tykot [Department of Anthropology, University of South Florida (USF), Tampa, FL] for compiling and editing the Proceeding of the 2010 ISA. This research is sup- ported by NSF grant #0804169 awarded to Raymond Mauldin and Robert Hard. All data sets used here, as well as the samples themselves in many cases, are available through Raymond.mauldin@utsa.edu. Details on the research can be found at http://car.utsa.edu Citation: Smith S, Mauldin R, Munoz CM, Hard R, Paul D, Skrzypek G, Villanueva P, Kemp L, 2014. Exploring the use of stable carbon isotope ratios in short-lived leporids for local paleoecological reconstruction. In: RH Tykot (ed.), Proceedings of the 38 th International Symposium on Archaeometry – May 10 th -14 th 2010, Tampa, Florida. Open Journal of Archaeometry 2:5306. Presented at the 38 th International Symposium on Archaeometry – May 10 th -14 th 2010, Tampa, Florida. This work is licensed under a Creative Commons Attribution 3.0 License (by-nc 3.0). ©Copyright S. Smith et al., 2014 Licensee PAGEPress, Italy Open Journal of Archaeometry 2014; 2:5306 doi:10.4081/arc.2014.5306 Non-commercial use only