Identifying a limiting factor in the population dynamics of a threatened amphibian: The influence of extended female maturation on operational sex ratio

We investigated sex‐specific population dynamics in the threatened green and golden bell frog (Litoria aurea) using intensive capture‐recapture methods in a newly created wetland complex and control sites. As hypothesised, females took longer to reach maturity compared to males. The length of female maturation was 3.9 times greater than that of males (428.68 days ± 107.6 SD and 110.16 days ± 20.59 SD, respectively). This resulted in a one‐year delay in female population size increase compared to the male population. The operational sex ratio (OSR) in the second year of monitoring in the created wetlands had the most disproportionate male bias out of any year and any site (12/1 male/female, male proportion = 0.92 ± 0.89–0.94 95% CI). In the third year, the OSR had become less male biased (2.6/1, male proportion = 0.72 ± 65–0.78 95% CI), likely attributed to the maturing of the females produced in the first year breeding events. We did not find any evidence that survival or detection probability influenced the observed OSRs in the created wetlands. Based on survival rates of each sex, we estimate that males are 77 times more likely to reach sexual maturity compared to females. We postulate that the combination of chytrid‐induced disease and sex‐biased maturation rates may be a driver of declines, especially in populations with limited recruitment. We encourage future research into investigating sex‐specific population dynamics of amphibians, especially relating to reintroduction ecology.
We have included the capture-recapture data of this study and the associated code embedded in R studio of the POPAN models used to estimate the super-population size of each year at every site.

本研究深入探讨了受威胁的绿色金斑蛙（Litoria aurea）的性别特定种群动态，通过在新建湿地复合体和控制站点实施密集的捕捉-释放方法进行。正如预期，雌蛙达到成熟的时间比雄蛙更长。雌蛙成熟的时长是雄蛙的3.9倍（分别为428.68天 ± 107.6标准差和110.16天 ± 20.59标准差）。这导致雌蛙种群数量比雄蛙种群数量延迟一年增长。在新建湿地监测的第二年中，操作性别比（OSR）在所有年份和所有站点中表现出最不均衡的雄性偏倚（12/1雄性/雌性，雄性比例 = 0.92 ± 0.89–0.94 95%置信区间）。到了第三年，OSR的雄性偏倚有所降低（2.6/1，雄性比例 = 0.72 ± 65–0.78 95%置信区间），这很可能归因于第一年繁殖事件中产生的雌蛙的成熟。我们没有发现任何证据表明存活率或检测概率影响了新建湿地中观察到的OSR。基于每性别的存活率，我们估计雄蛙达到性成熟的可能性是雌蛙的77倍。我们推测，由水霉病引起的疾病和性别偏倚的成熟率可能是导致种群数量下降的驱动力，尤其是在招募能力有限的种群中。我们鼓励未来对两栖动物的性别特定种群动态进行深入研究，尤其是与再引入生态学相关的研究。此外，本研究已将捕捉-释放数据及用于估计每年每个站点超级种群大小的POPAN模型相关代码嵌入R studio中。