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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. 

Elucidating factors that limit the number of offspring produced is fundamental to understanding life‐history evolution. Here, we examine the hypothesis that parental ability to maintain an optimal physical developmental environment for all offspring constrains clutch size via effects on offspring quality.

Experimental laboratory studies of birds have shown that a <1°C difference in average incubation temperature has diverse effects on fitness‐related post‐hatching offspring phenotypes. Thus, the inability of parents to maintain optimal incubation temperatures could constrain clutch sizes.

A fundamental question that has not been sufficiently addressed is whether larger clutch sizes lead towithinnest variation in egg temperature that is large enough to produce offspring with different phenotypes within a brood. This could lead to differential survival among offspring, and could create a trade‐off between offspring number and quality.

We manipulated clutch size in nests of free‐living wood ducks and measured incubation temperature among and within clutches using multiple temperature loggers.

As clutch size increased, average incubation temperatures were lower and more variable, and eggs took longer to hatch. Notably, the range inaverageincubation temperature among eggswithinnests increased with clutch size and exceeded 1°C in large clutches. Clutch size did not affect hatch success.

In conjunction with our companion laboratory studies that used artificial incubation to document the effects of temperature variation on fitness‐related traits in this species, our work suggests that suboptimal incubation temperatures could be a factor that limits clutch size through diminishing returns on post‐hatch offspring quality.

A freeplain language summarycan be found within the Supporting Information of this article.

 

Artificial shelters show considerable promise as tools for studying imperiled hellbender salamanders. Their full utility has not yet been fully reached in practice, however, because during initial trials shelters often became blocked by sediment or dislodged during high stream discharge events. To determine whether these challenges could be overcome, we deployed 438 artificial shelters of two different designs across 10 stream reaches and three rivers in the upper Tennessee River Drainage in 2013–2018. We recorded shelter entrance availability during surveys, and recorded which shelters became dislodged following high discharge events. We evaluated two hypotheses: (a) shelter availability was driven by shelter placement and maintenance frequency and (b) shelter stability was driven by shelter design and shelter placement. Shelters were available 78.6% of the time on average (range = 0–100%), and 88.6% (388 of 438) of shelters were stable across all high discharge events. Shelter availability was maximized by clearing sediment from shelter entrances at least once every 40 days (more often in impaired reaches with high siltation) and after large storm events, situating the shelter within 1 m of ≥5 boulders, and orienting shelters such that their entrances do not face directly downstream. Shelter stability with our initial shelter design was 77.5% (169 of 218), but approached 100% (219 of 220) for heavier (~40 kg vs. ~25 kg) shelters with recessed lids, and in reaches with abundant large boulders. Our findings demonstrate that with an improved design and careful placement, artificial shelters can serve as valuable tools for monitoring hellbenders in reaches with modest siltation.