Turnover of oxygen and hydrogen isotopes in the body water, CO2, hair, and enamel of a small mammal

Oxygen and hydrogen isotope signatures of animal tissues are strongly correlated with the isotope signature of local precipitation and as a result, isotope signatures of tissues are commonly used to study resource utilization and migration in animals and to reconstruct climate. To better understand the mechanisms behind these correlations, we manipulated the isotope composition of the drinking water and food supplied to captive woodrats to quantify the relationships between drinking water (ddw), body water (dbw), and tissue (dt). Woodrats were fed an isotopically constant food but were supplied with isotopically depleted or enriched water. Some animals were switched between these waters, allowing simultaneous determination of body water turnover, isotope change recorded in teeth and hair, and fractional contributions of atmospheric O2, drinking water, and food to the oxygen and hydrogen budgets of the animals. The half-life of the body water turnover was 3–6 days. A mass balance model estimated that drinking water, atmospheric O2, and food were responsible for 56%, 30%, and 15% of the oxygen in the body water, respectively. Drinking water and food were responsible for 71% and 29% of the hydrogen in the body water, respectively. Published generalized models for lab rats and humans accurately estimated dbw, as did an updated version of a specific model for woodrats. The change in drinking water was clearly recorded in hair and tooth enamel, and multiplepool and tooth enamel forward models closely predicted these changes in hair and enamel, respectively. Oxygen and hydrogen atoms in the drinking water strongly influence the composition of the body water and tissues such as hair and tooth enamel; however, food and atmospheric O2 also contribute oxygen and/or hydrogen atoms to tissue. Controlled experiments allow researchers to validate models that estimate dt based on ddw and so will increase the reliability of estimates of resource utilization and climate reconstruction. 2007 Elsevier Ltd. All rights reserved.