Causes and consequences of individual variation: Linking state-dependent life histories to population performance

The tradeoff between investment in current reproduction versus future survival is central to life-history theory, and long-lived, iteroparous mammals disproportionately favor their own survival. Previous work has demonstrated that adjustment of reproductive effort in long-lived mammals often occurs after parturition, owing to the greater cost of lactation relative to gestation. Under the right conditions, however, this difference in the relative costs of reproduction may also facilitate another, arguably less intuitive, strategy. Those conditions, which are relatively common among capital-breeding ungulates, include: (1) Females have the capacity to adjust gestation length; (2) Neonatal mortality occurs mostly during the first month of life and is inversely related to birth mass; and (3) The influence of birth mass on the probability of surviving the first month of life is stronger than the influence of autumn body mass on the probability of surviving the first winter of life. Under th..., A detailed description of data-collection methods can be found in the following publications: Long, R.A., R.T. Bowyer, W.P. Porter, P. Mathewson, K.L. Monteith, S.L. Findholt, B.L. Dick, and J.G. Kie.  2016.  Linking habitat selection to fitness-related traits in herbivores: the role of the energy landscape.  Oecologia 181:709-720. Long, R.A., R.T. Bowyer, W.P. Porter, P. Mathewson, K.L. Monteith, and J.G. Kie.  2014.  Behavior and nutritional condition buffer a large-bodied endotherm against direct and indirect effects of climate.  Ecological Monographs 84:513-532., The two data files are in .txt format. The code is contained in .R files that require program R (or associated GUI like R Studio) to open., # Data from: Causes and consequences of individual variation: Linking state-dependent life histories to population performance The file \"Starkey_Elk_Data.txt\" contains data for the subset of dam/juvenile pairs for which we had data on (1) birth mass of the neonate, (2) mass of the juvenile in the winter following birth, (3) nutritional condition of the dam both in the spring prior to parturition and the winter following. It was exploratory analyses of these data that suggested the bet-hedging strategy in the first place. The following meta-data pertain to columns in that dataset: * **Sex:** Sex of the neonate (female or male). * **Birth mass:** Birth mass of the neonate in kg. * **Birth date:** Birth date of the neonate. * **Julian birth date:** Julian date on which the neonate was born. * **Winter mass date:** Date on which mass of the neonate (now juvenile) was measured during capture operations in the winter following birth. * **Julian winter mass date:** Julian date on which t...当前繁殖投入与未来存活之间的权衡是生活史理论（life-history theory）的核心议题，而长寿的多次繁殖类哺乳动物（iteroparous mammals）会不成比例地偏向自身存活。既往研究表明，长寿哺乳动物的繁殖投入调整往往发生在分娩之后，这是因为泌乳的成本远高于妊娠。不过在合适条件下，这类繁殖相对成本的差异也可能催生另一种可以说并不符合直觉的繁殖策略。这类在资本繁育型有蹄类动物（capital-breeding ungulates）中相对常见的条件包括：(1) 雌性个体具备调整妊娠期长度的能力；(2) 幼崽死亡率主要集中在出生后的第一个月，且与出生体重呈负相关；(3) 出生体重对幼崽出生后首月存活概率的影响，强于秋季体重对幼崽首个冬季存活概率的影响。在……条件下，数据收集方法的详细说明可参阅以下文献： Long, R.A.、R.T. Bowyer、W.P. Porter、P. Mathewson、K.L. Monteith、S.L. Findholt、B.L. Dick 及 J.G. Kie. 2016. 将栖息地选择与草食动物的适合度相关性状关联：能量景观的作用. 《Oecologia》181:709-720. Long, R.A.、R.T. Bowyer、W.P. Porter、P. Mathewson、K.L. Monteith 及 J.G. Kie. 2014. 行为与营养状况可缓冲大型恒温动物受到气候的直接与间接影响. 《Ecological Monographs》84:513-532. 本数据集包含两份 .txt 格式的数据文件，配套代码存储于 .R 格式文件中，需使用R程序（或其配套图形用户界面如R Studio）打开。 # 数据来源：个体变异的成因与后果：将状态依赖型生活史与种群表现关联起来 文件"Starkey_Elk_Data.txt" 包含母鹿-幼崽配对子集的数据，我们已获取以下信息：(1) 幼崽的出生体重，(2) 幼崽在出生后首个冬季的体重，(3) 母鹿在分娩前春季及产后冬季的营养状况。正是通过对这些数据的探索性分析，我们最初提出了风险分摊（bet-hedging）繁殖策略的设想。以下为该数据集各列的元数据说明： * **性别（Sex）：** 幼崽的性别，分为雌性与雄性。 * **出生体重（Birth mass）：** 幼崽的出生体重，单位为千克（kg）。 * **出生日期（Birth date）：** 幼崽的出生日期。 * **儒略出生日期（Julian birth date）：** 幼崽出生的儒略日。 * **冬季体重测量日期（Winter mass date）：** 幼崽（此时已为亚成体）在出生后首个冬季的捕获称重日期。 * **冬季体重测量儒略日（Julian winter mass date）：** 幼崽冬季体重测量对应的儒略日，原文未完整说明……