Detecting declines and quantifying extinction risk of long-lived, highly fecund vertebrates, including fishes, reptiles, and amphibians, can be challenging. In addition to the false notion that large clutches always buffer against population declines, the imperiled status of long-lived species can often be masked by extinction debt, wherein adults persist on the landscape for several years after populations cease to be viable. Here we develop a demographic model for the eastern hellbender (Cryptobranchus alleganiensis), an imperiled aquatic salamander with paternal care. We examined the individual and interactive effects of three of the leading threats hypothesized to contribute to the species' demise: habitat loss due to siltation, high rates of nest failure, and excess adult mortality caused by fishing and harvest. We parameterized the model using data on their life history and reproductive ecology to model the fates of individual nests and address multiple sources of density-dependent mortality under both deterministic and stochastic environmental conditions. Our model suggests that high rates of nest failure observed in the field are sufficient to drive hellbender populations toward a geriatric age distribution and eventually to localized extinction but that this process takes decades. Moreover, the combination of limited nest site availability due to siltation, nest failure, and stochastic adult mortality can interact to increase the likelihood and pace of extinction, which was particularly evident under stochastic scenarios. Density dependence in larval survival and recruitment can severely hamper a population's ability to recover from declines. Our model helps to identify tipping points beyond which extinction becomes certain and management interventions become necessary. Our approach can be generalized to understand the interactive effects of various threats to the extinction risk of other long-lived vertebrates. As we face unprecedented rates of environmental change, holistic approaches incorporating multiple concurrent threats and their impacts on different aspects of life history will be necessary to proactively conserve long-lived species.

中文翻译：

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在父母照顾下的长寿、高繁殖力脊椎动物的并发威胁和灭绝风险

检测长寿、高繁殖力脊椎动物（包括鱼类、爬行动物和两栖动物）的衰退并量化其灭绝风险可能具有挑战性。除了大群体总是能缓冲种群数量下降的错误观念之外，长寿物种的濒危状态常常被灭绝债务所掩盖，即在种群不再具有生存能力后，成虫仍会在景观上持续数年。在这里，我们开发了东部地狱蝾螈（ Cryptobranchus alleganiensis ）的人口模型，这是一种受到父亲照顾的濒危水生蝾螈。我们研究了假设导致该物种灭绝的三种主要威胁的个体和交互影响：淤积造成的栖息地丧失、巢穴失败率高以及捕捞和收获造成的成虫死亡率过高。我们使用有关其生活史和繁殖生态学的数据对模型进行参数化，以模拟单个巢穴的命运，并解决确定性和随机环境条件下密度依赖性死亡率的多种来源。我们的模型表明，在野外观察到的高巢穴失败率足以将地狱蜥蜴种群推向老龄化年龄分布，并最终导致局部灭绝，但这个过程需要数十年的时间。此外，由于淤积、巢穴失败和随机成虫死亡率而导致巢址可用性有限，这些因素相互作用，会增加灭绝的可能性和速度，这在随机情况下尤其明显。幼虫存活和补充的密度依赖性会严重阻碍种群从衰退中恢复的能力。我们的模型有助于确定临界点，超过该临界点，灭绝就变得确定，管理干预就变得必要。我们的方法可以推广到理解各种威胁对其他长寿脊椎动物灭绝风险的相互作用影响。当我们面临前所未有的环境变化速度时，需要采取综合方法，纳入多种并发威胁及其对生命史不同方面的影响，以主动保护长寿物种。