Life history theory predicts trade-offs in allocation between survival, maintenance, growth, and reproduction, especially when resources are scarce. Individual variation in resource acquisition can affect trade-offs, but is often unaccounted for. We quantified the fitness costs of reproduction, accounting for environmental conditions, maternal characteristics and individual variation. We analyzed 10 years of data from marked kangaroos to evaluate how reproductive allocation affected annual mass change and skeletal growth, subsequent fecundity and weaning success, and survival, accounting for maternal mass or size and forage availability. Through repeated measurements of 76-91 females, we investigated how trade-offs varied within and between individuals, assessing whether individual variation could mask population-level trade-offs. In poor environments, females that weaned an offspring lost mass. Females that nursed an offspring for > 7 months had reduced skeletal growth. Females that did not gain mass over the previous 12 months rarely reproduced, especially if they had nursed an offspring for > 7 months the previous year. Reproductive allocation had no effect on weaning success, which was very low, and did not affect maternal survival, suggesting a conservative strategy. Disentangling within- and between-individual responses revealed trade-offs within individuals, but because individuals did not vary in their responses to earlier effort, these trade-offs did not drive population trends. The interacting effects of environmental conditions, maternal characteristics and individual variation on allocation trade-offs demonstrate the importance of long-term monitoring for understanding life history variations in changing environments.

中文翻译：

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饲草的可利用性和母性会影响大型有袋动物的繁殖成本。

生命历史理论预测，在生存，维持，增长和繁殖之间的分配之间需要权衡取舍，尤其是在资源稀缺的情况下。资源获取中的个体差异会影响权衡，但通常无法解释。我们量化了生殖的适应成本，考虑了环境条件，孕产妇特征和个体差异。我们分析了来自袋鼠的10年数据，以评估生殖分配如何影响年度质量变化和骨骼生长，随后的繁殖力和断奶成功率以及存活率，其中包括孕产妇的体重或体型以及可食性。通过对76-91岁女性的重复测量，我们研究了个体内部和个体之间的权衡如何变化，评估了个体差异是否可以掩盖人口水平的权衡。在恶劣的环境中，为后代断奶的雌性体重下降。哺育后代超过7个月的雌性骨骼生长减少。在过去12个月内未增加体重的雌性动物很少繁殖，特别是如果他们在前一年中哺育了超过7个月的后代。生殖分配对断奶成功率没有影响，断奶成功率很低，也没有影响产妇的生存，表明采取了保守的策略。解开个体内部和个体之间的反应揭示了个体之间的权衡，但是由于个体对早期工作的反应没有变化，所以这些权衡并没有推动人口趋势。环境条件的相互作用