There are clues that calcium (Ca) isotope composition of vertebrate bioapatite is influenced by diet and trophic level. These clues however conflict with several cases of mammal species exhibiting Ca isotope compositions which are inconsistent with their trophic levels. These observations support that diet may not be the only factor driving the Ca isotope composition in mammalian enamel and bone. To investigate this question, we selected a modern Cervus elaphus population (Bauges Natural Regional Park, Alps, France) to serve as a model for Ca isotope physiology of cervids and other mammals. Subsequently, we reinvestigated the case of the fossil Rangifer tarandus population from Jaurens (Late Pleistocene locality, 32.6 to 29.7 kyr BP, France), a population for which abnormal ⁴⁴Ca-depleted isotope compositions (regarding the low trophic level of reindeers) have been previously documented. By combining bone samplings and serial enamel micro-samplings, we discuss the main potential sources of Ca isotopic variability in bioapatite of young and adult individuals. This includes the effects of gestation, lactation, antlerogenesis, browser-grazer ecologies, osteophagia and natural mineral licks. Our results suggest an important effect of lactation on bone Ca isotope composition (δ^44/42Ca = +0.19 ± 0.09‰; 95% confidence interval), whereas other factors such as gestation or antlerogenesis seem more secondary. Our enamel micro sampling method allowed to detect when enamel Ca isotope composition could be affected by milk consumption or mineral supplementation. Thanks to these advances, we collected new data from the Pleistocene reindeers of Jaurens, which are now consistent with their known low trophic level and plant-based diet. This demonstrates that disentangling ecological and physiological signals within enamel Ca isotope compositions is possible by using serial micro-sampling. This approach allows retrieving accurate trophic information from this proxy and truly pushes forward the limits of Ca isotope applications regarding paleoecology, physiology and ethology.

有线索表明，脊椎动物生物磷灰石的钙（Ca）同位素组成受饮食和营养水平影响。然而，这些线索与几个展示钙同位素组成与其营养水平不一致的哺乳动物物种相冲突。这些观察结果支持饮食可能不是驱动哺乳动物搪瓷和骨骼中Ca同位素组成的唯一因素。为了调查此问题，我们选择了现代鹿种群（法国阿尔卑斯山的鲍格斯自然地区公园）来作为鹿类和其他哺乳动物的Ca同位素生理学的模型。随后，我们重新调查了Jaurens（晚更新世地区，法国32.6至29.7吉尔）的化石Rangifer tarandus种群，该种群异常先前已经记录了⁴⁴种贫钙同位素组成（关于低营养级的驯鹿）。通过结合骨采样和连续搪瓷显微采样，我们讨论了年轻人和成年个体生物磷灰石中Ca同位素变异性的主要潜在来源。这包括妊娠，哺乳，鹿角生成，浏览器掠食者生态，吞噬和天然矿物质舔the的影响。我们的研究结果表明泌乳对骨骼钙同位素组成具有重要影响（^δ44/42Ca ＝ + 0.19±0.09‰；95％的置信区间），而其他因素（例如妊娠或鹿茸发生）似乎是次要的。我们的搪瓷微量采样方法可以检测出食用牛奶或补充矿物质对搪瓷Ca同位素组成的影响。由于这些进展，我们从Jaurens的更新世驯鹿中收集了新数据，这些数据现在与已知的低营养水平和植物性饮食相一致。这表明，通过使用连续微量采样，可以分解搪瓷Ca同位素组合物中的生态和生理信号。这种方法允许从该代理检索准确的营养信息，并真正推动了Ca同位素在古生态学，生理学和伦理学方面的应用范围。