Data from: Determinants of age at first reproduction and lifetime breeding success revealed by full paternity assignment in a male ungulate

Age at first reproduction is an important determinant of individual variation in reproductive success in ungulates, but few studies have examined its relationship with later fitness-related traits in males. We used a long-term individual based study of a harvested moose population to quantify the individual reproductive performance and survival of males, as well as to examine the determinants of age at first reproduction and consequences of age at first reproduction on lifetime breeding success. The probability that a male successfully reproduced at the age of two was negatively related to the mean age of adult males in the population, but the relationship weakened with increasing population size. Large antlers and large body mass relative to other males in the population increased the number of calves sired at their first successful mating season. In addition, those that successfully reproduced as two year-olds were more likely to sire calves the next year, making them more productive at a given age compared to those that first reproduced at the age of three or older. We emphasize the importance for males to start reproducing as soon as possible in a harvested population to gain lifetime fitness benefits, as surviving the hunt is a major determinant of reproductive success in this population. We found no costs of early reproduction in males, hence leading to high individual heterogeneity in male reproductive performance. The apparent lack of reproductive costs could partly be explained by the age distribution in the population, individual variation in early-life body mass and antler size, and differences in probabilities of being killed during hunt between successful and unsuccessful males.

初产年龄是决定有蹄类动物（ungulates）个体繁殖成功率变异的关键因素，但目前鲜有研究探讨其与雄性个体后续适合度相关性状的关联。我们基于某狩猎型驼鹿种群的长期个体水平研究，量化了雄性个体的繁殖表现与存活状况，并检验了初产年龄的影响因子，以及初产年龄对终生繁殖成功率的后续效应。雄性在2岁时成功繁殖的概率，与种群中成体雄性的平均年龄呈负相关关系，但该相关性会随种群规模增大而逐渐减弱。相较于种群内其他雄性个体，拥有更大鹿角与更高体质量的雄性，在首次成功交配季所繁育的幼崽数量更多。此外，于2岁时便成功繁殖的雄性，次年繁育幼崽的概率显著更高，因此在相同年龄下，其繁殖生产力要高于3岁及之后才首次繁殖的雄性个体。我们强调，在狩猎型种群中，雄性尽早开启繁殖对获取终生适合度收益具有重要意义，因为在该种群中，能否在狩猎活动中存活是繁殖成功的核心决定因素。本研究未发现雄性早期繁殖存在繁殖成本，这使得雄性繁殖表现呈现出高度的个体异质性。这种繁殖成本的显著缺失，可部分通过种群的年龄结构、个体早期体质量与鹿角大小的变异，以及成功繁殖与未成功繁殖雄性在狩猎中被捕杀的概率差异来解释。