Nursing and weaning are behaviors that are central to the growth of offspring and success of mammal populations. The duration of nursing and timing of weaning are essential elements of a species' life history, but they are also somewhat plastic; weaning age increases during intervals of drought or other dietary stress. Thus, weaning age provides a proxy for nutritional stress in an extinct population, provided there is a way to determine weaning age for long-dead individuals. In growth records of proboscidean tusks, stable isotope compositions have been used to investigate nursing and weaning, but a taxon-specific framework for interpreting isotope data has been lacking. Here, we present results of a longitudinal study of stable isotopes in a nursing dam-calf pair of captive African elephants. The data include behavioral observations and hair growth rates, as well as stable isotope ratios in elephant feed and drinking water, in plasma and milk from the dam, and in tail hair from both individuals. Serial changes in the stable isotope ratios of nitrogen (δ¹⁵N), carbon (δ¹³C), oxygen (δ¹⁸O), and hydrogen (δ²H) reflect the transitions from placental nutrition in utero to exclusive nursing immediately after birth, and then to final weaning when the calf was six years old. Three of the four isotope systems reveal enrichment in the calf with respect to the dam prior to parturition and all show this relative enrichment during early nursing. At the end of nursing, final weaning was marked by changes in two of the systems: the convergence of dam and calf δ¹³C records and the abrupt onset of relative depletion in calf ¹⁵N following a year of elevated δ¹⁵N in both individuals. These patterns provide criteria for recognizing records of nursing and weaning contained in fossil tusks, providing grounds for assessing stress in prehistoric populations.

护理和断奶是后代生长和哺乳动物种群成功的关键。护理时间和断奶时间是一个物种生活史的基本要素，但它们在某种程度上也是可塑的。在干旱或其他饮食压力间隔期间，断奶年龄会增加。因此，断奶年龄为绝种人群的营养压力提供了一种代名词，只要有一种方法可以确定长死者的断奶年龄。在长鳍象牙的生长记录中，稳定的同位素组成已被用于研究护理和断奶，但缺乏用于解释同位素数据的分类群特定框架。在这里，我们介绍了在人工饲养的非洲小牛对小象中稳定同位素的纵向研究结果。数据包括行为观察和毛发生长率，以及大象饲料和饮用水，大坝的血浆和牛奶中以及两个人的尾毛中的稳定同位素比。氮的稳定同位素比（δ¹⁵ N），碳（δ ¹³ C），氧（δ ¹⁸ O），和氢（δ ² 2H）反射从胎盘营养的过渡在子宫内独家护理出生后立即，然后向最终断奶时小腿是六岁。四个同位素系统中的三个揭示了分娩前小牛相对于大坝的富集，并且都显示了早期护理期间的相对富集。在哺乳结束，最后断奶在两个系统中被打上了变化：大坝及小腿δ收敛^13个Ç记录和相对枯竭的小腿突然发病¹⁵ N A一年后的升高δ ¹⁵两个人均为N。这些模式为识别化石象牙中所含的护理和断奶记录提供了标准，为评估史前人群的压力提供了依据。