Abstract: By studying the trophic niche of rodents, we can not only understand the nutrient layer occupied by rodents in the ecosystem, but also reveal their main food sources and their relationships with changes observed in rodents at different growth and development periods. In this study, 81 rodent specimens of 4 species were captured using the snap-trapping method in typical grasslands of Inner Mongolia in July 2018. The trophic niche of Brandt’s voles (Lasiopodomys brandtii) and their interspecific relationship with other three common rodents, i.e., Spermophilus dauricus, Phodopus sungorus and Allactaga sibirica, were analyzed using ¹³C and ¹⁵N stability isotope techniques. We found a marked age-specific trophic niche in the width of bone tissue in Brandt’s voles, i.e., the Ⅲ age group had the widest with 0.802 ‰² Bayesian standard ellipse area,  followed by the Ⅱ age group with 0.699 ‰² ellipse area, and the lowest in the Ⅳ age group with 0.666 ‰².  The trophic niche overlap commonality area among the three age groups was 0.064 ‰², and common food sources accounted for less than 10% of all food sources. Moreover, we did not find that Brandt's voles competed for food sources with the other three rodents in either the short-term or long-term diet. However, compared with the other three rodent species, the niche width of Brandt's voles was narrower and its food selectivity was stronger. These findings suggest that if food source composition changed and was no longer suitable for Brandt's voles in their habitat, the vole might face food shortage and emigration would be a direct and favorable strategy for the development of the voles’ population.

Key words: Brandt’s vole, Stable isotope, Nutritional niche, Population, Bayesian ellipse

摘要： 研究啮齿动物营养生态位不仅可以了解啮齿动物在生态系统中所占据的营养层，而且可以揭示啮齿动物不同生长发育时期的主要食物来源及变化，通过分析营养生态位的特征及变化，可以探讨多种啮齿动物的种间关系。本研究于2018年7月，在内蒙古典型草原采用铗日法捕获啮齿动物标本4种81只，应用稳定性¹³C、¹⁵N同位素技术对布氏田鼠（Lasiopodomys brandtii）营养生态位及其与达乌尔黄鼠（Spermophilus dauricus）、黑线毛足鼠（Phodopus sungorus）、五趾跳鼠（Allactaga sibirica）的种间关系进行研究。结果表明：（1）布氏田鼠不同年龄组骨骼组织营养生态位宽度即稳定同位素贝叶斯标准椭圆面积，Ⅲ龄组最高（0.802‰²），Ⅱ龄组次之（0.699‰²），Ⅳ龄组最低（0.666‰²），3个年龄组之间营养生态位共同重叠面积为0.064‰²，其共同食物源仅占不到10%；（2）布氏田鼠无论是长期食性或短期食性，与另外3种均不存在食物源竞争，但布氏田鼠生态位宽度较窄对食物的选择性较强，因此一旦食物源成分改变不再适于该鼠，布氏田鼠种群极有可能面临食物源短缺，种群迁移可能是最直接的选择。

关键词: 布氏田鼠, 稳定同位素, 营养生态位, 种群, 贝叶斯椭圆