Herpetofauna II

Contributed Oral Presentations

Contributed paper sessions will be available on-demand for the duration of the conference, then again at the conclusion of the conference.


Improving Amphibian Road Mitigation Structures to Reduce Roadkill at the Barrier Fence Ends
Krisine Elisa Harman
A new highway was built through the largest tract of continuous forest in Ohio. To address concerns for wildlife populations, several crossing tunnels were installed, including an amphibian barrier-ecopassage. Since 2015, we have documented over 13,000 dead amphibians because the highway divides an important migratory corridor used by amphibians as they move from forest habitats to breeding ponds in the adjacent wetlands. To prevent amphibians from accessing the road, fencing was installed as a measure to reduce roadkill. Although, roadkill significantly declined within the boundaries of the fencing, we subsequently detected an increase in mortality at the fence ends, a common phenomenon known as the fence-end effect. Fence-end treatments are often recommended to block animals from moving around the fence ends, but studies demonstrating the effectiveness of these treatments are lacking. For my study, I compared the effectiveness of 90° and 45° fence-end treatments to determine the most effective treatment for (1) preventing movement around fence ends, and (2) redirecting movement back to the ecopassages. To test these two options, I built four experimental fences, each with a fence-end treatment. Amphibian behavior will be recorded as they navigate the experimental fences. I will assess whether animals can locate the simulated tunnel side (opposite to the fence-end treatment), and if they interact with the fence-end treatment, do they escape around the fence ends or reverse direction. Studies investigating behavior to address key conservation issues to mitigate road effects is critical, particularly for amphibian populations that are highly impacted by roads.
Assessing Short-Term Efficacy of Translocation As a Conservation Strategy for Wild Eastern Hellbenders
Bradley D. Nissen; Emilly Nolan; Michael Freake; Rebecca Hardman; William Sutton
Translocations have become a common conservation strategy for herpetofauna, yet are not always rigorously monitored to evaluate their success. Due to population declines and habitat fragmentation throughout its range, the Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) is a strong candidate for translocation in Tennessee. Our objective was to evaluate the short-term success of translocation on wild Hellbenders by comparing the 1) survival rates, 2) home range sizes, and 3) habitat usage of individuals pre- and post-translocation using radio-telemetry. We studied the spatial ecology and multi-scale habitat use of individuals (N =27) in two sustainable populations (Tumbling Creek and Hiwassee River) for one year and then subsequently collected similar data from a portion of these individuals (N =17) that were translocated (May-July 2019) into two nearby streams with declining populations (Rough Creek and Citico Creek, respectively). We collected 1,584 location data points (869 prior to translocation and 715 post-translocation) from our four study sites. Survival rates of translocated individuals increased when moved from Tumbling to Rough Creek (80% to 100%), while they decreased when moved from Hiwassee to Citico Creek (76% to 33%). Long distance movements (>100 m) were observed in 58% of translocated individuals (7/12) at Citico Creek, compared to only 20% (1/5) at Rough Creek. The greater rate of “exploration” amongst individuals in Citico Creek could be due to increased competition for prey items with other predators (e.g. large fish, otters), and likely led to the increased predation by otters. This study will serve to inform managers about the potential for translocation as a conservation strategy for Eastern Hellbenders.
Assessing the Distribution and Status of the Neuse River Waterdog in a Heavily Modified Landscape Across 40 Years of Surveying
Eric W. Teitsworth
The Neuse River Waterdog (Necturus lewisi) is an aquatic salamander endemic to the Neuse and Tar-Pamlico River basins of eastern North Carolina. As listed in the North Carolina State Wildlife Action Plan, N. lewisi is experiencing range contractions and decline in overall abundance, likely caused by habitat loss via land use change in the upstream watershed. North Carolina Wildlife Resource Commission surveys conducted 2011-2015 prompted the United States Fish & Wildlife Service to issue a Species Status Assessment in 2017 and propose N. lewisi as Federally “Threatened” in 2019. Our objective was to understand the distribution of N. lewisi across a heavily altered landscape and to explore what is driving population dynamics over time by combining two historical datasets with our recently collected occupancy data. We conducted presence/absence surveys at 116 unique locations in the historic range of N. lewisi Nov. 2018-Mar. 2019 and Dec. 2019-Mar. 2020. We wanted to explore the effects of daily weather fluctuation on detection probability and the effects of land use/land cover data on occupancy probability. We hypothesized increased streambank erosion and sedimentation is a primary driver of site occupancy and used an index of stream instability to test this hypothesis. After estimating detection probability for the recently collected data, we adjusted our historical data to accommodate variable detection rates and to understand occupancy dynamics over a 40 year period including variables influencing local colonization and extinction rates. Our results suggest the observed and modeled declines in occupancy are caused by rapid land use change, specifically the expansion of agricultural land and urban areas in the Neuse and Tar-Pamlico River basins, and the subsequent effect it has on stream instability and sedimentation. These results were critically important in the final Federal listing decision and for developing future management strategies for the Neuse River Waterdog.
Microbiome and Skin Peptide Activity Associated with Lesions in Hellbenders
Rebecca Hardman
Hellbenders, Cryptobranchus alleganiensis, are declining throughout their range and Arkansas (AR) populations of the Ozark subspecies, C. a. bishopi, are now reduced to a single river. Further, biologists have observed an increase in foot skin lesions with unknown etiology. Amphibian skin is physiologically important often manifesting lesions with systemic disease. We compared skin microbiome and skin peptides between C. a. bishopi in AR, and eastern hellbenders, C. a. alleganiensis, in Tennessee to determine if skin parameters could help explain health discrepancies noted in the field. We collected dorsal skin swabs from both AR and eastern TN (ETN) populations in 2014 for skin microbial analysis. In 2016-2017, we collected passive skin secretions to evaluate skin peptide activity against both chytrid fungi (Batrachochytrium dendrobatidis and B. salamandrivorans). In the latter group we also collected a skin swab and tissue biopsy for qPCR analysis of pathogens Bd/Bsal and ranavirus, respectively. We found skin microbial communities were richer with less dispersion in ETN compared to AR, and further, dispersion increased between individuals with severe lesions. From skin peptides assays, we discovered that invitro activity was markedly decreased in AR individuals compared to MTN and ETN and that presence of toe lesions was significantly associated with decreased activity. Inhibitory activity was on average greater against Bsal in comparison to Bd. We also observed a potential interaction between Bd and ranavirus infection on peptide production. In summary, skin peptide and microbiome are altered in AR populations and changes are likely associated with a chronic disease process manifested as presence of swollen and ulcerated toes. Both environmental and infectious etiologies are hypothesized. This work highlights the importance of apply several sampling techniques to analysis wildlife health and further research will be needed to implement a mitigation strategy for hellbenders
Cutaneous Immune Response of Eastern Hellbender Salamanders during Vaccination and Challenge with Chytrid Fungus
Alyssa Wetterau Kaganer; Robert Ossiboff; Elizabeth Bunting; Brian Gratwicke
Chytridiomycosis, the deadly disease caused by chytrid funguses including Batrachochytrium dendrobatidis (Bd) targets amphibian skin and currently represents the most significant global disease threat to biodiversity. The disease has been associated with amphibian declines across six continents but elicits substantial inter- and intra-species variation in amphibian host response. Eastern hellbender salamanders (Cryptobranchus alleganiensis alleganiensis) are a species of conservation concern throughout their range in the eastern United States of America with a heterogeneous response to Bd infection. We investigated the functional relationships between host, pathogen, and commensal skin microbiome which play a role in producing observed differential disease outcomes in this species. We explored the utility of a longitudinal metatranscriptome approach to characterize gene expression of host, pathogen, and microbiome during a previously conducted vaccination and challenge experiment of eastern hellbenders with Bd. We examined transcripts from tail skin punch biopsies collected at four experimental time points: 1) Day 0- prior to vaccination, 2) Day 89- post vaccination and pre-infection, 3) Day 117- early infection, and 4) Day 187- late infection. Eighteen animals were selected for analysis including six unvaccinated and uninfected animals, six unvaccinated and infected animals, and six vaccinated and infected animals. Commensal microbial and Bd transcripts were aligned to their respective genomes while eastern hellbender transcriptomes were de novo assembled for differential gene expression analysis. Application of a longitudinal metatranscriptome approach enabled us to monitor cutaneous host immune response throughout the course of infection and provided insights into the associated activity of pathogen and microbiome.
Assessing Effects of Translocation on Amphibian Chytrid Fungus and the Cutaneous Microbiome of Wild Eastern Hellbenders
Emilly Nolan; Bradley Nissen; Donald Walker; Rebecca Hardman; Michael Freake; William Sutton
Eastern Hellbenders are declining across historic ranges and many populations are locally extirpated. To augment declining populations, we conducted a translocation project for this species in eastern Tennessee. In 2018, 30 hellbenders were implanted with radio-transmitters and 17 were translocated in 2019. Disease monitoring is an essential step in translocation projects, specifically in amphibians where emerging pathogens such as Batrachochytrium dendrobatidis are linked to population declines. Species like the hellbender may be resilient to Bd due to disease resistant bacteria found on amphibian skin. However, the amphibian cutaneous microbiome is sensitive to disturbance, and changes to microbial composition may lead to an increase in disease susceptibility. Bd and skin bacterial samples were collected pre- and post-translocation to test for changes in pathogen prevalence and community differences that may occur. Quantitative polymerase chain reaction was used to test for presence of Bd and quantify zoospore loads. To characterize skin microbial communities, the bacterial 16S ribosomal V4 region was amplified and sequenced using an Illumina MiSeq system. A total of 16 hellbenders tested positive for Bd, however none showed signs of chytridiomycosis. Translocation did not have an effect on Bd prevalence. Alpha and beta diversity of bacterial communities did not change post-translocation. Results of this study directly benefit hellbender conservation as it shows wild hellbenders can be successfully used in translocation projects. Although sample size was low, we also show translocation does not increase Bd prevalence or have an effect on cutaneous microbial communities.
Spatial and Temporal Variability in Salamander Population Size
Allison Kaitlyn Williams; Daniel Hocking
Amphibians have experienced global declines from factors including habitat loss and modification, diseases, direct exploitation, and climate change. Even in protected areas such as US National Parks, amphibians have declined in the areas they occupy. Despite these trends, our understanding of declines, range contractions, and range shifts of most specific populations is insufficient. Furthermore, a lack of knowledge regarding spatial and temporal variation in population sizes obfuscates detection of trends in populations over time. Part of this challenge is in separating ecological processes from observational processes such as distinguishing detection, temporary emigration, and survival. As part of the larger regional Salamander Population and Adaptation Research Collaborative Network (SPARCnet), we established six 5 x 10 m coverboard plots in western Maryland to assess woodland salamander population dynamics beginning in 2017. We conducted spatial capture-recapture on 3-5 occasions each spring and fall in a robust design framework. We caught a total of 533 Plethodon cinereus 1,255 times across six primary sampling periods. The best supported model included random emigration with an estimate of 12% and mean survival estimates ranged from 40-70% with 2% variance among years. The capture rate and recapture rates were equal but varied over time ranging from 7 – 36% depending on environmental conditions. There was considerable spatial variation in states and vital rates even among even nearby sites (<100 m apart), but high-density sites tended to stay at relatively high over time. This provides baseline information for understanding spatial and temporal variation in terrestrial salamanders in a portion of their range. These data will be combined with other studies across the range of the species to understand the larger scale spatial patterns and regional synchrony in population dynamics as well as contributing to our understanding of local adaptations and responses to environmental conditions.


Contributed Oral Presentations
Location: Virtual Date: Time: -