Data from: Distinguishing between determinate and indeterminate growth in a long-lived mammal

Background: The growth strategy of a species influences many key aspects of its life-history. Animals can either grow indeterminately (throughout life), or grow determinately, ceasing at maturity. In mammals, continued weight gain after maturity is clearly distinguishable from continued skeletal growth (indeterminate growth). Elephants represent an interesting candidate for studying growth because of their large size, long life and sexual dimorphism. Objective measures of their weight, height and age, however, are rare. Results: We investigate evidence for indeterminate growth in the Asian elephant Elephas maximus using a longitudinal dataset from a semi-captive population. We fit growth curves to weight and height measurements, assess sex differences in growth, and test for indeterminate growth by comparing the asymptotes for height and weight curves. Our results show no evidence for indeterminate growth in the Asian elephant; neither sex increases in height throughout life, with the majority of height growth completed by the age of 15 years in females and 21 years in males. Females show a similar pattern with weight, whereas males continue to gain weight until over age 50. Neither sex shows any declines in weight with age. Conclusions: These results have implications for understanding mammalian life-history, which could include sex-specific differences in trade-offs between size and reproductive investment.研究背景：物种的生长策略对其生活史的诸多关键特征具有重要影响。动物的生长模式可分为两类：终生持续生长的不定向生长（indeterminate growth），以及成熟后即停止的有限生长（determinate growth）。在哺乳动物中，成熟后体重的持续增长与骨骼的持续生长（即不定向生长）有着明确的区分。大象凭借其庞大体型、较长寿命以及显著的性二态性，成为研究生长模式的理想对象。然而，针对其体重、体高与年龄的客观测量数据却较为匮乏。 研究结果：本研究依托半圈养种群的纵向数据集，探究亚洲象（Elephas maximus）是否存在不定向生长现象。我们通过对体重与体高测量数据拟合生长曲线，评估生长过程中的性别差异，并通过比较体高与体重生长曲线的渐近值，检验不定向生长是否存在。研究结果显示，亚洲象并无不定向生长的证据：两性个体的体高均不会随终生增长，雌性个体的绝大多数体高生长在15岁左右完成，雄性则在21岁左右完成绝大多数体高生长。雌性个体的体重变化模式与体高类似，而雄性个体的体重增长会持续至50岁以上，且两性个体的体重均未随年龄增长出现下降趋势。 研究结论：本研究结果有助于深入理解哺乳动物的生活史策略，其中或包含体型与繁殖投入之间的性别特异性权衡。