Life Histories of Juvenile Woolly Mammoths from Siberia: Stable Isotope and Elemental Analyses of Tooth Dentin.

Abstract

In order to expand knowledge of woolly mammoth life history and paleobiology, serial compositional analyses (δ13C, δ15N, δ18O, and ratios of Mg, P, Mn, Fe, Cu, Zn, Sr, Ba, and Pb to Ca) were performed on the tooth dentin of juvenile woolly mammoths (Mammuthus primigenius) from Siberia, and a juvenile African elephant (Loxodonta africana) from Hwange National Park, Zimbabwe. A procedure in which incremental lines are digitally enhanced permits high-resolution, serial sampling of dentin even when growth lines are not visible during actual sampling. Experimentation with pretreatment procedures for analyses of structural carbonate in dentin suggests that H2O2 is preferable to NaOCl for removal of organic material because use of H2O2 minimizes possible bicarbonate or carbonate contamination. A juvenile elephant tusk shows nitrogen isotope patterns consistent with higher milk intake in the first year of life, followed by seasonal oscillations. Carbon isotopes also show seasonal oscillations due to changes in the ratio of C3 to C4 plants in the diet, and this pattern is correlated with weather data from the time of life. Evidence from compositional patterns suggests that the relative importance of milk in the diet may have fluctuated seasonally. In juvenile mammoths, δ15N decreases with age, consistent with decreasing milk intake. However, these individuals died young and may not have been fully weaned at death. Thus, weaning ages cannot be determined. Carbon and oxygen isotopes generally vary seasonally. Strontium/calcium and barium/calcium ratios vary seasonally in some tusks. Analyses of individuals with neonatal lines marking the time of birth show that it occurred when δ15N was increasing, likely in spring. In these individuals, zinc/calcium is elevated near the time of birth. Study of the teeth, tissues, and gut contents of “Lyuba,” a remarkably well-preserved calf, offers additional insights into juvenile mammoth paleobiology. Milk residues and processed vegetation present in her intestine suggest that she was nursing and also engaging in coprophagy near the time of death. Absence of prenatal permanent tusk development in Lyuba and its presence in a male calf suggests that timing of tusk development was variable and may have differed by sex.