Sex allocation theories predict that under different ecological conditions the production of sons and daughters will affect parental fitness differently. Skewed offspring sex ratios often occur under captive conditions where individuals are exposed to nutritional and social conditions that differ from nature. Here, we analyzed 29 years of offspring sex ratio data from a captive population of an endangered marsupial, the Numbat (Myrmecobius fasciatus). We partitioned variation in offspring sex ratio based on parental origin (captive- vs. wild-bred), parental weight, maternal age, and maternal reproductive history. Our analyses revealed no effect of parental weight or maternal origin on offspring sex ratio—however, there was a significant effect of paternal origin. Data visualization indicated that captive-bred males tended to produce male-biased litters. We discuss the result in relation to recent studies that have shown that male mammals have the capacity to be arbiters of sex allocation and highlight candidate mechanisms, but consider it with caution due to the small sample size from which the result was derived. We performed a population viability analysis (PVA) to explore the potential impact of a sex ratio skew on the sustainability of the captive Numbat population under hypothetical scenarios. Our PVA revealed that supplementation with wild individuals is critical to the persistence of the captive Numbat population and that a biased sex ratio will lead to extinction of the captive colony under certain conditions. Overall, our study demonstrates that covert sex ratio skews can persist undetected in captive populations, which have the potential to become impactful and compromise population sustainability under changed management processes.

中文翻译：

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食蚁兽（Myrmecobius fasciatus）的父母对后代性别比例的影响：圈养是否会影响父亲的性别分配？

性别分配理论预测，在不同的生态条件下，儿子和女儿的生产会对父母的健康产生不同的影响。在圈养条件下，个体暴露于不同于自然的营养和社会条件的情况下，经常会出现后代性别比例失衡的情况。在这里，我们分析了濒危有袋动物袋食蚁兽 (Myrcobius fasciatus) 圈养种群 29 年的后代性别比数据。我们根据亲本来源（圈养与野生繁殖）、亲本体重、母亲年龄和母亲生殖史对后代性别比的变化进行划分。我们的分析显示，父母体重或母亲出身对后代性别比没有影响，然而，父亲出身却有显着影响。数据可视化表明，人工饲养的雄性往往会产生雄性偏向的后代。我们讨论了与最近的研究相关的结果，这些研究表明雄性哺乳动物有能力成为性别分配的仲裁者并强调候选机制，但由于得出结果的样本量较小，因此请谨慎考虑。我们进行了种群生存力分析 (PVA)，以探讨假设情景下性别比例偏差对圈养食蚁兽种群可持续性的潜在影响。我们的 PVA 表明，补充野生个体对于圈养食蚁兽种群的持续存在至关重要，并且性别比例的偏差在某些条件下会导致圈养群体的灭绝。总体而言，我们的研究表明，圈养种群中隐蔽的性别比例偏差可能会持续存在而不被发现，这有可能在管理流程发生变化的情况下产生影响并损害种群的可持续性。