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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.

 

Amphibian declines are a global phenomenon but responses of populations to specific threats are often context dependent and mediated by individual physiological condition. Habitat degradation due to reduced riparian forest cover and parasitism are two threats facing the hellbender salamander (Cryptobranchus alleganiensis), but their potential to interact in nature remains largely unexplored. We investigated associations between forest cover, parasitic infection and physiology of hellbenders to test the hypotheses that physiological condition responds to infection and/or habitat degradation. We sampled 17 stream reaches in southwest Virginia, USA, on a year-round basis from 2013 to 2016 and recorded 841 captures of 405 unique hellbenders. At each capture we documented prevalence of two blood-associated parasites (a leech and trypanosome) and quantified up to three physiological condition indices (body condition, hematocrit, white blood cell [WBC] differentials). We used generalized linear mixed models to describe spatiotemporal variation in parasitic infection and each condition index. In general, living in the most heavily forested stream reaches, where hellbender density was highest, was associated with the greatest risk of parasitism, elevated neutrophil-to-lymphocyte (N:L) ratios and eosinophils, slightly lower hematocrit and lower mean body condition in hellbenders. All condition indices fluctuated temporally in a manner consistent with seasonal variation in hellbender metabolic demands and breeding phenology and were associated with land use during at least part of the year. Paradoxically, relatively low levels of forest cover appeared to confer a potential advantage to individuals in the form of release from parasites and improved body condition. Despite improved body condition, individuals from less forested areas failed to exhibit fluctuating body condition in response to spawning, which was typical in hellbenders from more forested habitats. We postulate this lack of fluctuation could be due to reduced conspecific competition or reproductive investment and/or high rates of filial cannibalism in response to declining forest cover.

 

This manuscript explores the reasons why landowners allow or decline to allow research on their properties based on a combination of surveys and interviews. Based on our findings, we make recommendations for how researchers hoping to conduct research on private land can successfully gain access and encourage a good experience for all involved. 

Secretive species are difficult to study and often of conservation concern, as exemplified by the Eastern Hellbender (Cryptobranchus alleganiensis). Traditional methods for sampling Hellbenders involves moving rocks, which damages essential habitat. Use and installation of artificial shelters has made studying Hellbenders less dangerous for the animal and less disruptive to stream habitat; however, researchers using shelters generally capture occupying animals to identify them. We tested the ability of a submersible portable Passive Integrated Transponder (PIT) antenna to accurately detect PIT-tagged Hellbenders in shelters. We tested the effects of the presence and depth of cover rocks on top of shelters, PIT tag location within the shelter, and tag orientation on detection efficiency of Hellbenders. For the 32 shelters occupied by a tagged individual with cover rocks in place, the scanner accurately detected 31% of the animals versus 88% when cover rocks were removed. The detection efficiency of the scanner dropped below 50% once cover rock depth exceeded 11 cm. Tags placed near the interface of the entrance tunnel and chamber, or along the chamber walls, had higher detection efficiencies than those in other locations within the shelter. Vertically oriented tags were 18% more likely to be detected than horizontally oriented tags. Our study demonstrates that while this technology has certain limitations, it shows potent 

Abstract In 1992, the Union of Concerned Scientists shared their ‘World Scientists’ Warning to Humanity’ with governmental leaders worldwide, calling for immediate action to halt the environmental degradation that threatens the systems that support life on Earth. A follow-up ‘Second Warning’ was released in 2017, with over 15 000 scientists as signatories, describing the lack of progress in adopting the sustainable practices necessary to safeguard the biosphere. In their ‘Second Warning’, Ripple and colleagues provided 13 ‘diverse and effective steps humanity can take to transition to sustainability.’ Here, we discuss how the field of conservation physiology can contribute to six of these goals: (i) prioritizing connected, well-managed reserves; (ii) halting the conversion of native habitats to maintain ecosystem services; (iii) restoring native plant communities; (iv) rewilding regions with native species; (v) developing policy instruments; and (vi) increasing outdoor education, societal engagement and reverence for nature. Throughout, we focus our recommendations on specific aspects of physiological function while acknowledging that the exact traits that will be useful in each context are often still being determined and refined. However, for each goal, we include a short case study to illustrate a specific physiological trait or group of traits that is already being utilized in that context. We conclude with suggestions for how conservation physiologists can broaden the impact of their science aimed at accomplishing the goals of the ‘Second Warning’. Overall, we provide an overview of how conservation physiology can contribute to addressing the grand socio-environmental challenges of our time.