Stable isotope analysis of modern small mammals from Morocco: implications for reconstructing palaeoenvironment and palaeoclimate
Résumé
Small mammal remains from archaeological sites provide an excellent tool for reconstructing palaeoenvironment and palaeoclimate as they are abundant in the archaeological record, have small home ranges and prefer specific habitats. In this study we evaluate the stable carbon and oxygen isotope composition of small mammal teeth as a reflection of local climate and environmental conditions, with the
aim of assessing their use as a terrestrial proxy climate record in North Africa. Modern Gerbillus, Meriones and Mus teeth and bones, collected from mesic, semi-arid and arid environments across Morocco, were analysed for their δ13C and δ 18O, and δ 13C and δ 15N composition respectively. The results show oxygen isotopes in Gerbillus and Meriones tooth enamel are sensitive to changes in rainfall and relative humidity, with mammal teeth in more arid sites displaying higher oxygen isotope values relative to sites located in the mesic coastal zone. This is best explained by small mammals strong reliance on plant water, hence their bodywater and tooth enamel is highly sensitive to evaporative enrichment in plants under xeric
conditions. The carbon isotopes in the Gerbillus and Meriones tooth enamel display greater isotopic variability and likely reflect the vegetation within the mammal’s microhabitat. In Gerbillus, Meriones and Mus δ 15N appears insensitive to changes in aridity. Based on isotopic comparisons between individual Gerbillus and Meriones molar and incisor teeth, we find that molar teeth should be used in palaeoenvironmental reconstructions because these teeth consistently reflect the spring/summer breeding season. In contrast, incisors, which form continuously throughout the year, show increased isotopic variability in the proxy record. From this study we conclude that both oxygen and carbon isotopes in small mammal teeth are sensitive to environmental conditions in North Africa.