Fitness consequences of early-life conditions remain unclear and poorly studied in mammals. Based on long-term observations of yellow ground squirrels (Spermophilus fulvus), we identified early determinants of female fitness by analyzing the effects of early-life individual and environmental characteristics (weaning weight, weight gain rate, date of natal emergence, natal litter size, location of the natal burrow, local density of juveniles, population density and precipitation in the post-weaning period) on lifetime reproductive success (LRS). We found high variation and right-skewed distribution in all five LRS components (survival to adulthood, adult lifespan, and lifetime numbers of weaned litters, weanlings, and yearling offspring). Numbers of litters, weanlings, and adult offspring were correlated with each other and increased with lifespan, confirming that longevity is a better predictor of LRS than fecundity. Survival to adulthood was the most sensitive fitness component to early conditions and was higher in females (a) with greater weaning weight, (b) born further from human settlement and (c) born at lower population density. Population density at birth was the best early predictor of all LRS components and negatively influenced adult lifespan and numbers of weanlings and yearling offspring. Early growth rate positively affected the probability of reproducing after the first hibernation and the number of offspring weaned. Such syndrome of high-quality (heavy and fast-growing) young born in a favourable environment ("a silver spoon effect") with downstream damping fitness consequences has been observed so far in only a few mammalian species.

中文翻译：

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孤独冬眠者女性终生生殖成功的早期预测因子：“银匙”效应的证据。

早期生活状况对健康的影响尚不清楚，在哺乳动物中研究不足。基于黄地松鼠（Spermophilus fulvus）的长期观察，我们通过分析早期个体和环境特征（断奶体重，体重增加率，出生日期，产仔数）来确定女性健康的早期决定因素。 ，出生地的位置，幼虫的局部密度，断奶后的人口密度和降水量）对一生的生殖成功（LRS）的影响。我们发现LRS的所有五个组成部分（成活率，成年寿命，成年断奶仔猪，断奶仔和一岁后代的数量）均存在较高的变异和右偏分布。产仔，断奶和成年后代的数量相互关联，并随着寿命的增加而增加，证实寿命比肥力更好地预测LRS。成年后的生存是对早期状况最敏感的适应因素，女性（a）断奶体重更大，（b）因人类住区而出生和（c）人口密度较低而更高。出生时的人口密度是所有LRS成分的最佳早期预测指标，并且对成年寿命和断奶和一岁后代的数量产生负面影响。早期生长率对第一次冬眠后的繁殖概率和断奶后代数量产生积极影响。迄今为止，仅在少数几个哺乳动物物种中观察到这种在有利环境（“银匙效应”）中出生的高品质（重壮和快速成长）幼年的综合症，并具有下游阻尼适应性后果。