SUMMARYEctothermic species living in temperate regions can experience rapid and potentially stressful changes in body temperature driven by abrupt weather changes. Yet, among amphibians, the physiological impacts of short-term temperature variation are largely unknown. Using an ex situ population of Cryptobranchus alleganiensis, an aquatic North American salamander, we tested the hypothesis that naturally occurring periods of temperature variation negatively impact amphibian health, either through direct effects on immune function or by increasing physiological stress. We exposed captive salamanders to repeated cycles of temperature fluctuations recorded in the population's natal stream and evaluated behavioral and physiological responses, including plasma complement activity (i.e. bacteria killing) against Pseudomonas aeruginosa, Escherichia coli and Aeromonas hydrophila. The best-fit model (ΔAIC c =0, w i =0.9992) revealed 70% greater P. aeruginosa killing after exposure to variable temperatures and no evidence of thermal acclimation. The same model predicted 50% increased E. coli killing, but had weaker support (ΔAIC c =1.8, w i =0.2882). In contrast, plasma defenses were ineffective against A. hydrophila, and other health indicators (leukocyte ratios, growth rates and behavioral patterns) were maintained at baseline values. Our data suggest that amphibians can tolerate, and even benefit from, natural patterns of rapid warming/cooling. Specifically, temperature variation can elicit increased activity of the innate immune system. This immune response may be adaptive in an unpredictable environment, and is undetectable by conventional health indicators (and hence considered cryptic). Our findings highlight the need to consider naturalistic patterns of temperature variation when predicting species' susceptibility to climate change.

Spindly Leg Syndrome (SLS) is a persistent animal welfare issue associated with the rearing of amphibians in captivity. We conducted two experiments to investigate the effects of diet, water composition and overfeeding on prevalence of SLS in newly metamorphosed harlequin frogs (Atelopus spp.). In our first experiment, we offered 400 full-sibling tadpoles of Atelopus certus isocaloric diets in treatments of 31%, 37%, 42% and 48% crude protein respectively. Tadpoles fed higher protein diets metamorphosed faster, but the incidence of SLS exceeded 80% in all treatments leading to the conclusion that variation in dietary protein was not responsible for causing SLS. We used 720 full-sibling Atelopus glyphus tadpoles in a second experiment to examine the effects of diet type, water composition and diet ration on SLS. We found that an overall incidence of 58% spindly leg in tadpoles reared in tap water, but reduced to about 10% in water treated by reverse osmosis and then reconstituted. It is possible that the reverse osmosis treatment removed some factor that caused the SLS, or that the reconstitution may have added a mineral lacking in the original tap water. Within tap water treatments, overfeeding tadpoles in tanks increased the incidence of SLS. We recommend further experimental research into this condition to identify the causative factors in the water. Additional research into the nutritional composition of food available to wild tadpoles would be useful in formulating captive diets, that have to date been solely based on surrogate species.

We report new occurrence records for stygobiontic invertebrates from the Edwards and Trinity aquifers in Blanco, Hays, and Travis counties of central Texas, USA. Our collection includes seven species from four families: Caecidoteareddelli (Steeves, 1968), Asellidae; Crangonyxnr.pseudogracilis Bousfield, 1958, Stygobromusbalconis (Hubricht, 1943), Stygobromusbifurcatus (Holsinger, 1967), and Stygobromusrusselli (Holsinger, 1967), Crangonyctidae; Sphalloplanamohri Hyman, 1938, Kenkiidae; and Cirolanides sp., Cirolanidae. Specimens of Caecidoteareddelli and Crangonyxnr.pseudogracilis are new records for Hays County and Travis county, respectively. Specimens of an undescribed species of Cirolanides were collected from a well in Hays County and from two localities in Travis County.

We present 7 new occurrence records for the Barton Springs Salamander (Eurycea sosorum Chippindale, Price & Hillis, 1993) from Hays and Travis counties, Texas, USA, including the first for this species from the Trinity Aquifer. Eurycea sosorum is listed as endangered under the Endangered Species Act of 1973 due to ongoing threats from urbanization and aquifer overdraft throughout its narrow range. Although this species is more widely distributed than when it was first described in 1993, its range is still exceptionally small, restricted to portions of only two watersheds (Onion and Barton creeks) in one of the fastest-growing metropolitan areas in the United States (Austin, Texas). Under any ecologically-relevant criterion that is based on the best available scientific evidence, this species remains in danger of extinction throughout its range.

Disease monitoring is an essential step in translocation projects, specifically in amphibians where emerging pathogens such as the chytrid fungus Batrachochytrium dendrobatidis (Bd) are linked to population declines. The eastern hellbender Cryptobranchus alleganiensis is a large, fully aquatic salamander experiencing precipitous range-wide population declines; however, the role Bd plays in these declines is unclear. To augment declining hellbender populations and determine effects of translocation on Bd prevalence, we conducted a translocation study of wild adult hellbenders from 2 source streams with abundant hellbender populations to 2 streams with declining populations in east Tennessee, USA. In 2018, we implanted radio transmitters into 30 hellbenders and sampled them periodically for Bd until 17 of the 30 hellbenders were translocated in 2019. We attempted to recapture translocated hellbenders approximately every 45 d for 3 mo to determine Bd prevalence post-release. We used qPCR to detect Bd and quantify zoospore loads on positive samples. Hellbenders had a pre-translocation Bd prevalence of 50% (15 of 30), which decreased to 10% (1 of 10) post-translocation. The average zoospore load for positive samples was 73.63 ± 30.82, and no hellbenders showed signs of chytridiomycosis throughout the study. Although we detected no significant effect of translocation on Bd prevalence, we observed a reduction in Bd prevalence post-release. Our results indicate that translocation did not lead to an increase in pathogen prevalence in translocated wild adult hellbenders, suggesting that chytrid did not impact the success of short-term translocations of eastern hellbenders in the Blue Ridge ecoregion.

Translocations of freshwater species have become a widespread conservation strategy to mitigate the impacts of habitat fragmentation, yet they are not often rigorously monitored using animal movement data to determine their success. We demonstrate the value of monitoring pre- and post-translocation movements and home-range sizes of a fully-aquatic, benthic stream salamander, the eastern hellbender (Cryptobranchus a. alleganiensis) to determine translocation success. We studied the home range sizes, movements, and habitat use of individuals (n = 27) in two self-sustaining populations (S1 & S2) for one year, and then subsequently collected similar data from a subset of these individuals (n = 17) that were translocated into two nearby streams (T1 & T2) with dam-isolated, declining populations in the Blue Ridge Ecoregion of Tennessee. We collected 1,571 location data points (869 pre-translocation and 715 post-translocation) from four study sites, and evaluated effects of mass, sex, and pre-translocation home range size/sedentariness, as well as habitat covariates on home range size and movements. Hellbender home range sizes increased from pre-translocation estimates at both sites, but response depended primarily on physical characteristics of release sites. Home range and fine-scale movement metrics indicated that hellbenders translocated from S1 to T1 settled in more quickly, had greater site fidelity, and smaller home ranges than hellbenders translocated from S2 to T2. Hellbender movements were influenced by cover rock size and density rather than individual characteristics. Study-long survival rates of translocated hellbenders increased from S1 to T1 (80% to 100%) and decreased from S2 to T2 (76% to 33%). Monitoring pre- and post-translocation movements was a valuable method for evaluating short-term translocation success in a freshwater environment. For future hellbender translocations, managers should prioritize selecting suitable release sites with contiguous boulder-dense areas (1–2 per m2), adequate prey (crayfish) densities (>1/m2), and habitats with low risk of predation.

Movement behavior is an important aspect of animal ecology but is challenging to study in species that are unobservable for some portion of their lives, such as those inhabiting subterranean environments. Using four years of robust-design capture-recapture data, we examined the probability of movement into subterranean habitat by a population of endangered Barton Springs salamanders (Eurycea sosorum), a species that inhabits both surface and subterranean groundwater habitats. We tested the effects of environmental variables and body size on survival and temporary emigration, using the latter as a measure of subterranean habitat use. Based on 2,046 observations of 1,578 individuals, we found that temporary emigration was higher for larger salamanders, 79% of which temporarily emigrated into subterranean habitat between primary sampling intervals, on average. Body size was a better predictor of temporary emigration and survival compared to environmental covariates, although coefficients from lower ranked models suggested turbidity and dissolved oxygen may influence salamander movement between the surface and subsurface. Surface population dynamics are partly driven by movement below ground and therefore surface abundance estimates represent a fraction of the superpopulation. As such, while surface habitat management remains an important conservation strategy for this species, periodic declines in apparent surface abundance do not necessarily indicate declines of the superpopulation associated with the spring habitat.

Environmentally cued hatching has been well‐documented in amphibians in response to a wide range of abiotic and biotic factors. The hatching of terrestrial amphibian eggs in response to flooding may be basal within the group, but amphibian lineages in tropical Asia and sub‐Saharan Africa have not received as much attention as their Neotropical counterparts. We investigated submergence‐induced hatching in Feihyla hansenae, a Rhacophorid tree frog with terrestrial eggs. We quantified natural rates of clutch submergence at our study site in Thailand. Using submergence experiments, we found that embryos are capable of hatching early to escape flooding, and that failure to hatch results in mortality. Among the embryos that were able to hatch early, only the earliest, youngest hatchlings experienced a trade‐off in body size that persisted for 6 days, while later, older hatchlings were not significantly smaller than spontaneous hatchlings under control conditions. By incorporating our natural and experimental data into Monte Carlo methods to simulate and compare survival probabilities with and without hatching plasticity, we found an overall 3.1% increase in submergence survival due to hatching plasticity. Our findings support the idea that flooding‐induced hatching is widespread across amphibians with terrestrial eggs and highlight the importance of researching understudied tropical regions. As climate change is projected to affect rainfall patterns, the ability of embryos to escape abiotic egg‐stage threats may be an indicator of species' ability to flexibly navigate a changing environment.