Many endangered species exist in only a single population, and almost all species that go extinct will do so from their last remaining population. Understanding how to best conserve these single population threatened species (SPTS) is therefore a distinct and important task for threatened species conservation science. As a last resort, managers of SPTS may consider taking the entire population into captivity – ex situ, in toto conservation. In the past, this choice has been taken to the great benefit of the SPTS, but it has also lead to catastrophe. Here, we develop a decision-support tool for planning when to trigger this difficult action. Our method considers the uncertain and ongoing decline of the SPTS, the possibility that drastic ex situ action will fail, and the opportunities offered by delaying the decision. Specifically, these benefits are additional time for ongoing in situ actions to succeed, and opportunities for the managers to learn about the system. To illustrate its utility, we apply the decision tool to four retrospective case-studies of declining SPTS. As well as offering support to this particular decision, our tool illustrates why trigger points for difficult conservation decisions should be formulated in advance, but must also be adaptive. A trigger-point for the ex situ, in toto conservation of a SPTS, for example, will not take the form of a simple threshold abundance.

中文翻译：

---

选择非原生境的最佳触发点，以保护单个种群的受威胁物种

许多濒临灭绝的物种仅存在于一个种群中，几乎所有灭绝的物种都会从其最后剩余的种群中消失。因此，了解如何最好地保护这些单一种群威胁物种（SPTS）是威胁物种保护科学的一项独特而重要的任务。作为最后的选择，SPTS的管理者可能考虑在迁移中将整个人口圈养起来，以进行保护。过去，这种选择已使SPTS受益匪浅，但同时也导致了灾难。在这里，我们开发了一种决策支持工具，用于计划何时触发此困难的操作。我们的方法考虑了SPTS的不确定性和持续下降，剧烈的非原生境行动失败的可能性以及延迟决策提供的机会。特别，这些好处是持续进行原地操作取得成功所需的额外时间，也是管理人员了解系统的机会。为了说明其实用性，我们将决策工具应用于下降SPTS的四个回顾性案例研究。除了为该特定决策提供支持外，我们的工具还说明了为什么要预先制定困难的保护决策的触发点，但还必须具有适应性。例如，为了保护SPTS而进行异地迁移的触发点将不会采用简单的阈值丰度的形式。我们的工具说明了为什么要提前制定困难的保护决策的触发点，但也必须具有适应性。例如，为了保护SPTS，在异地触发的点将不会采取简单的阈值丰度的形式。我们的工具说明了为什么要提前制定困难的保护决策的触发点，但也必须具有适应性。例如，为了保护SPTS，在异地触发的点将不会采取简单的阈值丰度的形式。