1Geology and Anthropology, University of Cincinnati, 2Department of Anthropology, University of Illinois, 3Department of Anatomy, Midwestern University, 4Department of Anthropology, University of Massachusetts, Amherst
March 28, 2015 , Gateway Ballroom 2/3/4/5
Over the past 2000 years, Madagascar has undergone extensive ecological degradation. Deciphering the movement of animals among modern protected, unprotected, and degraded landscapes as well as mobility of individuals in the recent past could help direct management and conservation efforts. Strontium isotope (87Sr/86Sr) ratios, which predominantly reflect bedrock geology, are able to distinguish organisms from different regions as well as identify highly mobile individuals. We present strontium isotope data for modern plants and lemurs as well as subfossil hippos, lemurs, and carnivores. We find significant differences in 87Sr/86Sr ratios among lithologies. Samples from localities underlain by sandstones, unconsolidated sands, limestones, or lavas have lower and less variable 87Sr/86Sr ratios than those underlain by Precambrian igneous and metamorphic rocks. Modern plants and lemur bone from the same lithologies do not differ isotopically and overall, there are no differences in 87Sr/86Sr between modern and subfossil individuals from the same type of bedrock. However, there are several subfossil individuals that yielded 87Sr/86Sr ratios that are significant outliers for their respective lithologies. We identify these individuals as likely migrants and discuss their potential origins. Our results indicate that Sr isotope ratios can (i) distinguish plants and animals from localities underlain by different lithologies on Madagascar, and (ii) detect mobility of organisms prior to extensive habitat modification. Localities near geological contacts are particularly well suited for strontium provenience techniques. We anticipate that this geochemical tool could be used to identify historic and recent range restrictions, validate proposed conservation priorities, and identify additional key unprotected areas.