Evidence of demographic buffering in an endangered great ape: Social buffering on immature survival and the role of refined sex-age-classes on population growth rate

Theoretical and empirical research has shown that increased variability in demographic rates often results in a decline in the population growth rate. In order to reduce the adverse effects of increased variability, life-history theory predicts that demographic rates that contribute disproportionately to population growth should be buffered against environmental variation. To date, evidence of demographic buffering is still equivocal and limited to analyses on a reduced number of age-classes (e.g. juveniles and adults), and on single sex models. Here we used Bayesian inference models for age-specific survival and fecundity on a long-term dataset of wild mountain gorillas. We used these estimates to parameterize two-sex, age-specific stochastic population projection models that accounted for the yearly covariation between demographic rates. We estimated the sensitivity of the long-run stochastic population growth rate to reductions in survival and fecundity on ages belonging to nine...理论与实证研究均证实，种群统计率（demographic rates）的变异程度升高常会导致种群增长率下降。为缓解变异升高带来的不利影响，生活史理论（life-history theory）预测：对种群增长贡献不成比例的种群统计率，应可抵御环境波动的干扰。截至目前，种群统计缓冲（demographic buffering）的相关证据仍尚无定论，且仅局限于针对少量年龄组（如幼体与成体）以及单性模型的分析。 本研究基于野生山地大猩猩的长期监测数据集，构建了用于年龄特异性存活率（age-specific survival）与繁殖力（fecundity）的贝叶斯推断（Bayesian inference）模型。我们利用上述估计值对双性、年龄特异性且纳入种群统计率年度协变关系的随机种群预测模型进行参数化。我们还估算了长期随机种群增长率，针对九类……年龄组对应的存活率与繁殖力降低的敏感性。