母熊可以哺乳多少只幼崽？母熊的年龄和体型影响北极熊的幼崽数量。
How many cubs can a mum nurse? Maternal age and size influence litter size in polar bears.
机构信息
1 CEFE, CNRS, Univ Montpellier , Univ Paul Valéry Montpellier 3, EPHE, IRD, Montpellier , France.
2 Norwegian Polar Institute, Fram Centre , Tromsø , Norway.
出版信息
Biol Lett. 2019 May 31;15(5):20190070. doi: 10.1098/rsbl.2019.0070.
Life-history theory predicts that females' age and size affect the level of maternal investment in current reproduction, balanced against the future reproductive effort, maintenance and survival. Using long-term (30 years) individual data on 193 female polar bears ( Ursus maritimus), we assessed age- and size-specific variation on litter size. Litter size varied with maternal age, younger females had higher chances of losing a cub during their first months of life. Results suggest an improvement in reproductive abilities early in life due to experience with subsequent reproductive senescence. Litter size increased with maternal size, indicating that size may reflect individual quality. We also found an optimum in the probability of having twins, suggesting stabilizing selection on female body size. Heterogeneity was observed among the largest females, suggesting that large size comes at a cost.
生命周期理论预测，女性的年龄和体型会影响其当前繁殖的母性投资水平，以平衡未来的繁殖努力、维持和生存。本研究使用了 193 只雌性北极熊（ Ursus maritimus）长达 30 年的个体数据，评估了与年龄和体型相关的产仔数变化。产仔数随母体年龄而变化，年轻的雌性在生命的头几个月失去幼崽的几率更高。研究结果表明，由于与随后的生殖衰老有关的经验，雌性在生命早期生殖能力有所提高。产仔数随母体体型的增加而增加，表明体型可能反映了个体的质量。我们还发现了双胞胎出现的概率存在最佳值，这表明对雌性体型的选择是稳定的。在最大的雌性中观察到了异质性，这表明大型体型是有代价的。
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