Carbon- and nitrogen-isotope tissue-diet discrimination and turnover rates in deer mice, Peromyscus maniculatus

The dietary habits of most small mammals are not well documented, and stable isotope measurements can provide information on when and how diets change. Here we document the discrimination and turnover tunes for carbon and nitrogen isotopes in blood, fiver, muscle, hair, and milk frorn deer mice (Peromyscus moniculatus (Wagner, 1845)) fed a controlled diet. Nonbreeding adults and pregnant females were livetrapped, maintained on a commercial laboratory chow. and had tissues sampled on a regular schedule. After adjusting to the laboratory diet, Most tissues of nonbreeding adults were slightly depleted of C-13 and enriched in N-15 relative to diet (Delta C-13(tissue-diet) range = 0.3 parts per thousand to -1.1 parts per thousand; Delta N-15(tissue-diet) range = 1.9 parts per thousand to 3.4 parts per thousand). Liver (half-lives of 2.8 and 3.6 days for C and N, respectively) turned over more rapidly than blood (22.4 and 19.8 days for C and N, respectively) and Muscle (18.7 and 24.8 days for C and N, respectively). The isotopic compositions of' nonhreeding and breeding adults indicated tissue turnover at approximately the same rate, but juvenile tissues reflected the laboratory diet Much more quickly than adult tissues.