Breath and diet samples were collected from 29 taxa of animals at the Zurich and Basel Zoos to characterize the carbon isotope enrichment between breath and diet. Diet samples were measured for 13C and breath samples for CH4/CO2 ratios and for the respired component of 13C using the Keeling plot approach. Different digestive physiologies included hindgut coprophagous, hindgut non-coprophagous, foregut non-ruminants, and foregut ruminants. Isotope enrichments from diet to breath were 0.8±0.9‰, 3.5±0.8‰, 2.3±0.4‰, and 4.1±1.0‰, respectively. CH4/CO2 ratios were strongly correlated with isotope enrichments for both foregut and hindgut digestive strategies, although CH4 production was not the sole reason for isotope enrichment. Average CH4/CO2 ratios per taxon ranged over several orders of magnitude from 10-5 to 10-1. The isotope enrichment values for diet-breath can be used to further estimate the isotope enrichment from diet-enamel because Passey et al. (2005) found a nearly constant isotope enrichment for breath-enamel for diverse mammalian taxa. The understanding of isotope enrichment factors from diet to breath and diet to enamel will have important applications in the fields wildlife ecology, animal physiology, and in paleontology.

中文翻译：

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食草哺乳动物的饮食与呼吸之间的CH4 / CO2比和碳同位素富集

从苏黎世和巴塞尔动物园的29个动物分类中收集了呼吸和饮食样品，以表征呼吸和饮食之间碳同位素的富集。使用Keeling图法测量饮食样本的13C和呼气样本的CH4 / CO2比以及13C的呼吸成分。不同的消化生理学包括后肠共食，后肠非共食，前肠非反刍动物和前肠反刍动物。从饮食到呼吸的同位素富集分别为0.8±0.9‰，3.5±0.8‰，2.3±0.4‰和4.1±1.0‰。尽管CH4的产生不是同位素富集的唯一原因，但是CH4 / CO2的比例与前肠和后肠消化策略中的同位素富集密切相关。每个分类单元的平均CH4 / CO2比范围从10-5到10-1几个数量级。饮食呼吸的同位素富集值可用于进一步估计饮食釉质的同位素富集，因为Passey等人（2003年）提出。（2005年）发现了用于各种哺乳动物类群的呼吸釉的同位素浓度几乎恒定。从饮食到呼吸，从饮食到牙釉质的同位素富集因子的理解将在野生生物生态学，动物生理学和古生物学领域中具有重要的应用。