Lifetime fitness and its determinants are an important topic in the study of behavioural ecology and life-history evolution. Early life conditions comprise some of these determinants, warranting further investigation into their impact. In some mammals, babies born lighter tend to have lower life expectancy than those born heavier, and some of these life-history traits are passed on to offspring, with lighter-born females giving birth to lighter offspring. We investigated how weight at weaning, the relative timing of birth in the season, maternal weight, and maternal age affected the longevity and lifetime reproductive success (LRS) of female Columbian ground squirrels (Urocitellus columbianus). We hypothesized that early life conditions such as offspring weight would not only have lifetime fitness consequences but also intergenerational effects. We found that weight at weaning had a significant impact on longevity, with heavier individuals living longer. The relative timing of an individual’s birth did not have a significant association with either longevity or LRS. Individuals born to heavier mothers were found to have significantly higher LRS than those born to lighter mothers. Finally, maternal age was found to be significantly associated with their offspring’s LRS, with older mothers having less successful offspring. Our results provide evidence that early life conditions do have lifelong fitness and sometimes intergenerational consequences for Columbian ground squirrels.

中文翻译：

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天生优势：早年生活和母体对雌性地松鼠健康的影响

终生适应度及其决定因素是行为生态学和生活史进化研究的重要课题。早期生活状况包括其中一些决定因素，值得进一步研究其影响。在一些哺乳动物中，出生时体重较轻的婴儿的预期寿命往往比出生时体重较重的婴儿的预期寿命要低，并且其中一些生活史特征会遗传给后代，出生时体重较轻的雌性会生出体重较轻的后代。我们研究了断奶时的体重、季节中的相对出生时间、母亲体重和母亲年龄如何影响雌性哥伦比亚地松鼠 (Urocitellus columbianus) 的寿命和终生繁殖成功率 (LRS)。我们假设，诸如后代体重等早期生活状况不仅会产生终生健康影响，还会产生代际影响。我们发现断奶时的体重对寿命有显着影响，较重的个体寿命更长。个人出生的相对时间与长寿或 LRS 没有显着关联。研究发现，体重较重的母亲所生的个体的 LRS 明显高于体重较轻的母亲所生的个体。最后，发现母亲年龄与其后代的 LRS 显着相关，高龄母亲的后代不太成功。我们的研究结果提供了证据，表明早期生活条件确实对哥伦比亚地松鼠具有终生适应性，有时甚至是代际影响。