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Although it has long been known that stressors such as diseases and contaminants do not act alone, estimating how combinations of different stressors affect amphibians in the wild has generally proven elusive. A new ARMI study helps clarify the threat of the amphibian chytrid fungus (Bd), a pathogen linked with population declines and extirpations of amphibians globally. One of the most surprising results was that Bd reduced adult survival even for some species previously considered resistant to Bd, such as the Eastern Newt. This study also provides the first evidence of that methylmercury can affect survival of wild amphibians, even at sites without obvious sources of mercury contamination. In some cases, Bd and methylmercury appeared to act synergistically to magnify the effect of disease, further reducing survival. This study builds on a recent nation-wide assessment of methylmercury bioaccumulation that used non-lethal sampling, allowing researchers to sample threatened and endangered species that otherwise could not have been included in the study. This new study involved coordinated sampling by ARMI-scientists across the contiguous USA, using a multi-species, multi-population, multi-year modeling effort to provide robust results on the effects of Bd and mercury on adult amphibian survival. The results highlight the challenges associated with managing amphibian populations in the face of endemic disease combined with other environmental stressors.

To view the full article, click this link: https://doi.org/10.1038/s41598-025-99839-3

Rapid warming in polar regions is causing large changes to ecosystems, including altering environmentally available mercury (Hg). Though subarctic freshwater systems have simple vertebrate communities, Hg in amphibians remains unexplored. We measured total Hg (THg) in wetland sediments and methylmercury (MeHg) in multiple life stages (eggs to adults) of Wood Frogs (Rana sylvatica) and larval Boreal Chorus Frogs (Pseudacris maculata) from up to 25 wetlands near Churchill, Manitoba (Canada), during summers 2018?2019. We used egg mass counts for Wood Frogs from 24 wetlands (2015–2019) and per-ovum MeHg concentrations to estimate site-level MeHg flux by metamorphs from wetlands to the terrestrial environment. Total Hg in wetland sediment was unrelated to MeHg concentrations of amphibian larvae, but sediment THg increased with from coastal tundra vegetation to inland boreal forests. Methylmercury concentrations of Wood Frog eggs (geometric mean = 35.9; range: 6.7–77.9 ng/g dry weight [dw]) exceeded previous reports for amphibians, including from sites contaminated by industrial sources of Hg. Methylmercury concentrations of adult Wood Frogs (298.9 ng/g dw) was also higher than that for frogs included in a recent assessment of MeHg in amphibians across the contiguous United States. Within wetlands, MeHg concentrations of Wood Frog larvae were strongly correlated with MeHg concentrations in eggs earlier in the summer and concentrations increased with each life stage. We estimate there would have been 1971.8?3286.4 ng MeHg exported from wetlands by Wood Frog metamorphs, which is 3.4?5.6 times more MeHg than inputted by eggs. Collectively, these data provide an initial assessment of Hg concentrations, body burdens, and dynamics in subarctic food webs that are expected to experience large changes from climate warming.

Climate change is a primary threat to biodiversity, but for many species, we still lack information required to assess their relative vulnerability to changes. Climate change vulnerability assessment (CCVA) is a widely used technique to rank relative vulnerability to climate change based on species characteristics, such as their distributions, habitat associations, environmental tolerances, and life-history traits. However, for species that we expect are vulnerable to climate change yet are understudied, like many amphibians, we often lack information required to construct CCVAs using existing methods. We used the CCVA framework to construct trait-based models based on life history theory, using empirical evidence of traits and distributions that reflected sensitivity of amphibians to environmental perturbation. We performed CCVAs for amphibians in 7 states in the north-central USA, focusing on 31 aquatic-breeding species listed as species of greatest conservation need by at last 1 state. Because detailed information on habitat requirements is unavailable for most amphibian species, we used species distributions and information on traits expected to influence vulnerability to a drying climate (e.g., clutch size and habitat breadth). We scored species vulnerability based on changes projected for mid-century (2040?2069) from 2 climate models representing “least-dry” and “most-dry” scenarios for the region. Species characteristics useful for discriminating vulnerability in our models included small range size, small clutch size, inflexible diel activity patterns, and smaller habitat breadth. When projected climate scenarios included a mix of drier and wetter conditions in the future, the exposure of a species to drying conditions was most important to relative rankings. When the scenario was universally drier, species characteristics were more important to relative rankings. Using information typically available even for understudied species and a range of climate projections, our results highlight the potential of using life history traits as indicators of relative climate vulnerability. The commonalities we identified provide a framework that can be used to assess other understudied species threatened by climate change.

We assessed amphibian diversity, rarity, and threats across the U.S. National Park System, which covers 3.5% of the U.S. and 12% of federal lands. At least 230 of 354 (65%) amphibian species native to the U.S. occur in parks. Of the species documented in parks, 17% are considered at-risk globally and 20% are uncategorized, reflecting still-widespread data deficiencies. Parks in the Northwest and Northeast accumulated species most quickly (i.e., steepest species?area relationships). Non-native crayfishes and amphibians occur within 50 km of 60% and 25% of parks, respectively, illustrating the broad threat of non-native predators. Projected mid-century (2040–2069) changes in climatic water deficit, based on 25 climate futures, produced an expected 34% increase in dryness across all parks in the contiguous U.S. territory. Our analyses highlight the extent and regional differences in current and future threats and reveal gaps in species protection, but also reveal opportunities for targeted expansion and active management.

Optimal egg size theory predicts females must balance investment per offspring to maximize fitness. This balance can change based on resources or habitat quality. In wetlands, common aspects of habitat quality are duration of water (hydroperiod) and predator presence. Ectotherms using habitats that dry or contain predators are likely under selection to optimize offspring production. We measured ovum and clutch sizes from wood frogs (Rana sylvatica) in 30 wetlands (2014?2019) in Subarctic Canada, where rapid changes in climate are accelerating wetland drying. We predicted wetlands with short hydroperiods would have larger ova, smaller clutch sizes, and larger ovum-to-clutch-sizes than wetlands with long hydroperiods or with fish predators. We found partial support for our predictions, with larger ova in habitats with short hydroperiods and no fish. We did not, however, find evidence of larger clutch sizes in wetlands with fish or a relationship with ovum-to-clutch size. Given the large environmental changes that are already occurring, our study is novel as one of the first to implicate these rapid changes as potential selective agents on reproductive output in an ectotherm.

The 10th World Congress of Herpetology was held in the city of Kuching, in Sarawak, Malaysia (northwest Borneo) August 5 – 9. ARMI scientists Brian Halstead, Blake Hossack, Pat Kleeman, and Erin Muths presented research papers. There were over 1400 delegates at the Congress, with > 900 contributed talks and 33 symposia.

Halstead and Muths organized a symposium targeted at graduate students (What Editors Want: A Guide to the Publication Process for Graduate Students) that included talks from 7 past and present editors, including Judit Voros, co-editor of Amphibia-Reptilia and Secretary General of the World Congress.

Hossack presented a talk co-authored by ARMI scientists Kelly Smalling and Brian Tornabene titled: “Energy-related secondary salinization of wetlands: Coordinated experiments and field surveys to identify mechanistic links with amphibian abundance”. This invited talk was included in the symposium titled: Haunting the seaside: Integrative biology of salt tolerance in amphibians.

Halstead presented a talk titled: “Effects of translocation and head-starting on giant gartersnake (Thamnophis gigas) behavior and survival”, co-authored by USGS scientist A. M. Nguyen and B. D. Todd (University of California, Davis). This invited talk was included in the symposium titled: Improving conservation and mitigation outcomes of snake translocations—global lessons.

Kleeman presented a contributed talk co-authored by Halstead and J.P. Rose (ARMI scientists), and collaborators from the Nevada Department of Wildlife, K. Guadalupe and M. West, titled: Initial demographic estimates for two species of narrowly endemic toads in central Nevada: Anaxyrus monfontanus and Anaxyrus nevadensis.

Muths’ presentation, co-authored by L. Bailey, A. Fueka, L. Roberts (Colorado State University) and B. Hardy (Chapman College), was in the symposium titled: Improving animal welfare. This invited talk was titled, “Methods in marking toads: PIT tagging versus photography”.

The World Congress is held every four years on different continents with the specific aim of facilitating attendance from herpetologists around the world especially those from developing countries. The first World Congress was held in Canterbury, Great Britain in 1989, with subsequent congresses in locations including China, Brazil, Australia, and Canada. ARMI hosted a symposium on amphibian decline in 2012 at the 7th World Congress in Vancouver.

Congress delegates in Kuching enjoyed multiple plenary talks with topics ranging from Bornean flora and fauna, to the Biogeography and Evolution of reptiles in the Arabian Peninsula, to Frog diversification in Old World tree frogs.

USGS ARMI scientists recently published a critical review on what is known about the effects of harmful algal blooms (HABs) on amphibians and reptiles.

HABs are a persistent and increasing problem globally in both freshwater and marine environments, yet we still have limited knowledge about how they affect wildlife. HABs can occur when colonies of algae have abundant resources, grow rapidly, and produce cyanotoxins. This natural phenomenon was first described in the late 1800s but have become more common due to increases in nutrient inputs and availability (e.g., from agriculture or runoff) and global temperatures that favor their growth.

Although semi-aquatic and aquatic amphibians and reptiles have experienced large declines and occupy environments where HABs are increasingly problematic, their vulnerability to HABs remains unclear. The current review was designed to synthesize existing information of the effects of cyanotoxins on amphibians and freshwater reptiles. The information gained by evaluating and synthesizing previous studies and reported mortality events could enhance monitoring and conservation efforts while also guiding future studies on both amphibians and reptiles.

Our review highlights how cyanotoxins can be lethal and negatively affect larval amphibians, but information on effects on reptiles or embryonic and adult amphibians is lacking, apart from a few observational studies. Cyanotoxins can have systemic effects and negatively influence reproductive, digestive, and liver function in amphibians. Given that amphibian and some reptile populations are declining worldwide, it is important to increase monitoring and experimental efforts to understand the singular and synergistic effects of these toxins. It will also be important to better understand the events that cause algal blooms to synthesize and release toxins and effects of HABs that do not produce cyanotoxins. We also propose future near-term and long-term studies that could help clarify the population-level effects of HABs on amphibians and reptiles and could enhance monitoring and management efforts, especially in areas where HABs have been documented consistently.

Harmful algal blooms (HABs) are a persistent and increasing problem globally, yet we still have a limited knowledge about how they affect many wildlife. Although semi-aquatic and aquatic amphibians and reptiles have experienced large declines and occupy environments where HABs are increasingly problematic, their vulnerability to HABs remains unclear. To inform monitoring, management, and future studies, we conducted a literature review and synthesized studies and reported mortality events describing effects of cyanotoxins from HABs on freshwater herpetofauna. Our review identified 37 unique studies and 71 endpoints (no-observed-effect and lowest-observed-effect concentrations) involving 11 amphibian and three reptile species worldwide. Responses varied widely among studies, species, and concentrations used in experiments. Concentrations causing lethal and sublethal effects in experiments were generally 1–100 µg/L, which is near the mean value of reported events but 70times less than the maximum cyanotoxin concentrations reported in the environment. However, one species of amphibian was tolerant to concentrations of 10,000 µg/L, demonstrating potentially immense differences in sensitivities. Most studies focused on microcystin-LR (MC-LR), which can increase systemic inflammation and harm the digestive system, reproductive organs, liver and kidneys, and development. The few studies on other cyanotoxins illustrated that effects resembled those of MC-LR at similar concentrations, but more research is needed to describe effects. All experimental studies were on larval and adult amphibians; there were no such studies on reptiles. Experimental work with reptiles and adult amphibians is needed to clarify thresholds of tolerance. Only nine mortality events were reported, mostly for reptiles. Given that amphibians likely decay faster than reptiles, which have tissues that resists decomposition, mass amphibian mortality events from HABs have likely been underreported. We propose seven major areas to focus future efforts to enhance our understanding of effects and monitoring of HABs on herpetofauna that fill important roles in freshwater and terrestrial environments.

Comma-separated values (.csv) file containing data related to amphibian sampling across the United States between 2016 and 2021. Data files contain mercury concentrations in amphibian and dragonfly tissues, mercury concentrations in sediment, as well as amphibian morphometrics, and habitat and climate characteristics where the samples were collected.

The first widescale assessment of methylmercury in adult amphibians in the U.S. shows that this toxic compound is common, widespread and, at least for some populations, can reach very high levels. The ARMI-led publication brought together scientists from around the country to test more than 3,200 amphibians representing 14 species from 26 populations. Amphibians are the most endangered group of vertebrates worldwide, but prior to this study, little information was available on mercury bioaccumulation in amphibians across the U.S.

Mercury is a contaminant of global concern that can harm humans and wildlife. In aquatic ecosystems, microbes can convert elemental mercury to methylmercury, which increases risks because methylmercury is more bioavailable, more toxic, and it biomagnifies through food webs.

Study results showed that the amount of methylmercury in amphibians varied widely among sites and by life history characteristics, such as diet, size, and sex. Amphibian methylmercury concentrations ranged from barely detectible at some locations, to levels above wildlife health benchmarks in others. The study also evaluated using dragonfly larvae to estimate bioaccumulation for amphibians that can’t be sampled because they are rare or secretive. Scientists determined that the concentration found in these insects can provide insight into methylmercury bioaccumulation in amphibians.

Despite its toxicity, scientists only have a limited understanding of methylmercury’s effects on amphibians and these results can be used to inform future research on the health effects of methylmercury exposure on amphibians. The study also provides new methods and baseline data that can help scientists and managers assess the risk from mercury for species of management concern, including species listed as threatened and endangered under the Endangered Species Act.

To view the full article click this link: https://pubs.acs.org/doi/10.1021/acs.est.3c05549

The Arizona Toad (Anaxyrus microscaphus) is restricted to riverine corridors and adjacent uplands in the arid southwestern United States. As with numerous amphibians worldwide, populations are declining and face various known or suspected threats, from disease to habitat modification resulting from climate change. The Arizona Toad has been petitioned to be listed under the U.S. Endangered Species Act and was considered “warranted but precluded” citing the need for additional information – particularly regarding natural history (e.g., connectivity and dispersal ability). The objectives of this study were to characterize population structure and genetic diversity across the species’ range. We used reduced-representation genomic sequencing to genotype 3,601 single nucleotide polymorphisms in 99 Arizona Toads from ten drainages across its range. Multiple analytical methods revealed two distinct genetic groups bisected by the Colorado River; one in the northwestern portion of the range in northwestern Arizona, southwestern Utah, and eastern Nevada and the other in the southeastern portion of the range in central and eastern Arizona and New Mexico. We also found subtle substructure within both groups, particularly in central Arizona where toad populations in lower elevations were less connected than those at higher elevations. The northern and southern parts of the Arizona Toad range are not well connected genetically and could be managed as separate units. Further, these data could be used to identify source populations for assisted migration or translocations to support small or potentially declining populations.

Recent ARMI-led research showed the removal of invasive American bullfrogs from livestock ponds and small lakes in southern Arizona also resulted in the apparent local extirpation of two pathogens associated with the bullfrogs. The American bullfrog is native eastern North America but has become widespread in the West, where it preys on many native species of conservation concern. Other recent ARMI-led research from the area suggested that American Bullfrogs could act as reservoirs for pathogens like amphibian chytrid fungus (Batrachochytrium dendrobatidis; Bd) and ranaviruses, which are often lethal to native amphibians, but less so to American Bullfrogs.

In the early 2000s, American bullfrogs were eradicated from ponds in the Buenos Aires National Wildlife Refuge near the Arizona-Mexico border to assist with the reintroduction efforts for the federally threatened Chiricahua Leopard Frog. In 2015, the bullfrog reinvaded the refuge and was once again removed. This reinvasion from outside the refuge motivated funding for a multi-year, landscape-scale eradication program. In the fall-winter of 2016 and the winter of 2020-2021, the research team tested the water at bullfrog eradication and control (no eradication efforts occurred) sites for the DNA (environmental DNA or eDNA) of invasive bullfrogs, federally threatened Chiricahua Leopard Frogs, and Bd and ranaviruses.

Results from the eDNA sampling showed American Bullfrogs were eradicated successfully from most sites, and where bullfrogs were eradicated, the pathogens were also no longer detected. Chiricahua Leopard Frogs did not increase in occurrence after eradicating bullfrogs, possibly due to an exceptional drought that could have limited the ability of native amphibians to colonize sites.

To our knowledge, this is one of the few studies to link eradication of an invasive species to co-eradication of emerging pathogens. Our spatially replicated experimental approach provides strong evidence that management of invasive species can simultaneously reduce predation and disease risk for imperiled species.

To view the full article click this link: https://doi.org/10.1111/conl.12970

National parks and other protected areas are important for preserving landscapes and biodiversity worldwide. An essential component of the mission of the United States (U.S.) National Park Service (NPS) requires understanding and maintaining accurate inventories of species on protected lands. We describe a new, national-scale synthesis of amphibian species occurrence in the NPS system. Many park units have a list of amphibian species observed within their borders compiled from various sources and available publicly through the NPSpecies platform. However, many of the observations in NPSpecies remain unverified and the lists are often outdated. We updated the amphibian dataset for each park unit by collating old and new park-level records and had them verified by regional experts. The new dataset contains occurrence records for 292 of the 424 NPS units and includes updated taxonomy, international and state conservation rankings, hyperlinks to a supporting reference for each record, specific notes, and related fields which can be used to better understand and manage amphibian biodiversity within a single park or group of parks.

Mercury (Hg) is a toxic contaminant that has been mobilized and distributed worldwide and is a threat to many wildlife species. Amphibians are facing unprecedented global declines due to many threats, including contaminants. While the bi-phasic life history of many amphibians creates a potential nexus for methylmercury (MeHg) exposure in aquatic habitats and subsequent health effects, the broad-scale distribution of MeHg exposure in amphibians remains unknown. We used non-lethal sampling to assess MeHg bioaccumulation in 3,241 juvenile and adult amphibians during 2017–2021. We sampled 26 populations (14 species) across 11 states in the United States, including several imperiled species that could not have been sampled by traditional lethal methods. We examined whether life history traits of species and whether concentration of total mercury in sediment or dragonflies could be used as indicators of MeHg bioaccumulation in amphibians. Methylmercury contamination was widespread, with a 33-fold difference in concentrations across sites. Variation among years and clustered subsites was less than variation across sites. Life history characteristics such as size, sex, and whether the amphibian was a frog, toad, newt, or other salamander were the factors most strongly associated with bioaccumulation. Total Hg in dragonflies was a reliable indicator of bioaccumulation of MeHg in amphibians (R2 ? 0.67) whereas total Hg in sediment was not (R2 ? 0.04). Our study, the largest broadscale assessment of MeHg bioaccumulation in amphibians, highlights methodological advances that allow for non-lethal sampling of rare species and reveals immense variation among species, life histories, and sites. Our findings can help identify sensitive populations and provide environmentally relevant concentrations for future studies to better quantify potential threats of MeHg to amphibians.

Non-invasive methods are important to conservation physiology to reduce negative effects on the species being studied. Glucocorticoid (GC) hormones are often used to assess health of individuals, but collection methods can be invasive. Many amphibians are imperiled worldwide, and saliva is a non- or semi-invasive matrix to measure GCs that has been partially validated for only four amphibian species. Validation ensures that assays are reliable and can detect changes in saliva corticosterone (sCORT) following exposure to stressors, but it is also necessary to ensure sCORT concentrations are correlated with plasma concentrations. To help validate the use of saliva in assessing CORT responses in amphibians, we captured uniquely marked Columbia Spotted Frogs (Rana luteiventris) on sequential days and collected baseline and stress-induced (after handling) samples. For a subset of individuals, we collected and quantified CORT in both saliva and blood samples, which have not been compared for amphibians. We tested several aspects of CORT responses and, by collecting across separate days, measured repeatability of CORT responses across days. We also evaluated whether methods common to amphibian conservation, such as handling alone or handling, clipping a toe, and tagging elevated sCORT. Similar to previous studies, we show that sCORT is reliable concerning parallelism, recovery, precision, and sensitivity. Saliva CORT was weakly correlated with plasma CORT (R2 = 0.21), and we detected elevations in sCORT after handling, demonstrating biological validation. Toe-clipping and tagging did not increase sCORT over handling alone, but repeated handling elevated sCORT for ~72 hours. However, sCORT responses were highly variable and repeatability was low within individuals and among capture sessions, contrary to previous studies with urinary and waterborne CORT. Saliva CORT is a semi-invasive and rapid technique that could be useful to assess effects of anthropogenic change, and conservation efforts, but will require careful study design and future validation.

Interventions of host-pathogen dynamics provide strong tests of relationships, yet they are still rarely applied across multiple populations. After American Bullfrogs (Rana catesbeiana) invaded a wildlife refuge where federally threatened Chiricahua Leopard Frogs (R. chiricahuensis) were reintroduced 12 years prior, managers launched a landscape-scale eradication effort to help ensure continued recovery of the native species. We used a before-after-control-impact (BACI) design and environmental DNA sampling of 19 eradication sites and 18 control sites between fall 2016 and winter 2020–2021 to measure community-level responses to bullfrog eradication, including for 2 pathogens. Dynamic occupancy models revealed successful eradication from 94% of treatment sites. Native amphibians did not respond to bullfrog eradication, but the pathogens amphibian chytrid fungus (Batrachochytrium dendrobatidis) and ranaviruses were co-extirpated with bullfrogs. Our spatially replicated experimental approach provides strong evidence that management of invasive species can simultaneously reduce predation and disease risk for imperiled species.

Mercury (Hg) is a toxic contaminant that has been mobilized and distributed worldwide and is a threat to many wildlife species. Amphibians are facing unprecedented global declines due to many threats including contaminants. While the biphasic life history of many amphibians creates a potential nexus for methylmercury (MeHg) exposure in aquatic habitats and subsequent health effects, the broad-scale distribution of MeHg exposure in amphibians remains unknown. We used nonlethal sampling to assess MeHg bioaccumulation in 3,241 juvenile and adult amphibians during 2017–2021. We sampled 26 populations (14 species) across 11 states in the United States, including several imperiled species that could not have been sampled by traditional lethal methods. We examined whether life history traits of species and whether the concentration of total mercury in sediment or dragonflies could be used as indicators of MeHg bioaccumulation in amphibians. Methylmercury contamination was widespread, with a 33-fold difference in concentrations across sites. Variation among years and clustered subsites was less than variation across sites. Life history characteristics such as size, sex, and whether the amphibian was a frog, toad, newt, or other salamander were the factors most strongly associated with bioaccumulation. Total Hg in dragonflies was a reliable indicator of bioaccumulation of MeHg in amphibians (R2 ? 0.67), whereas total Hg in sediment was not (R2 ? 0.04). Our study, the largest broad-scale assessment of MeHg bioaccumulation in amphibians, highlights methodological advances that allow for nonlethal sampling of rare species and reveals immense variation among species, life histories, and sites. Our findings can help identify sensitive populations and provide environmentally relevant concentrations for future studies to better quantify the potential threats of MeHg to amphibians.

Protected areas like national parks are essential elements of conservation because they limit human influence on the landscape, which protects biodiversity and ecosystem function. The role of national parks in conservation, however, often goes far beyond limiting human influence. The U.S. National Park Service and its system of land units contribute substantively to conservation by providing protected lands where researchers can document trends in species distributions and abundances, examine characteristics important for generating these trends, and identify and implement conservation strategies to preserve biodiversity. We reviewed the contribution of U.S. national parks to amphibian research and conservation and highlight important challenges and findings in several key areas. First, U.S. national parks were instrumental in providing strong support that amphibian declines were real and unlikely to be simply a consequence of habitat loss. Second, research in U.S. national parks provided evidence against certain hypothesized causes of decline, like UV-B radiation, and evidence for others, such as introduced species and disease. However, describing declines and identifying causes contributes to conservation only if it leads to management; importantly, U.S. national parks have implemented many conservation strategies and evaluated their effectiveness in recovering robust amphibian populations. Among these, removal of invasive species, especially fishes; conservation translocations; and habitat creation and enhancement stand out as examples of successful conservation strategies with broad applicability. Successful management for amphibians is additionally complicated by competing mandates and stakeholder interests; for example, past emphasis on increasing visitor enjoyment by introducing fish to formerly fishless lakes had devastating consequences for many amphibians. Other potential conflicts with amphibian conservation include increasing development, increased risk of introductions of disease and exotic species with increased visitation, and road mortality. Decision science and leveraging partnerships have proven to be key components of effective conservation under conflicting mandates in national parks. As resource managers grapple with large-scale drivers that are outside local control, public-private partnerships and adaptive strategies are increasing in importance. U.S. national parks have played an important role in many aspects of identifying and ameliorating the amphibian decline crisis and will continue to be essential for the conservation of amphibians in the future.

A new collaborative study provided evidence that invasive, non-native American Bullfrogs influence the occurrence of native amphibians and increase occurrence of pathogens, including ranaviruses and amphibian chytrid fungus (Bd). These pathogens can cause lethal diseases of amphibians and have been linked with widespread population declines. ARMI scientists partnered with collaborators from Arizona Game and Fish Department, US Fish and Wildlife Service, Turner Endangered Species Fund, University of Arizona, Washington State University, and National Autonomous University of Mexico (UNAM) to analyze water samples from 233 sites in the southwestern USA and northern Sonora, Mexico, for the presence of environmental DNA (eDNA). Federally threatened Chiricahua Leopard Frogs and Western Tiger Salamanders were 8 times and 2 times, respectively, less likely to occur at sites where bullfrogs occurred. Ranaviruses were 10 times and Bd was 2.5-times more likely to be present at sites with bullfrogs than without bullfrogs. These results provide evidence that bullfrogs reduce occurrence of native amphibians and can increase occurrence of pathogens. This information can clarify risks for native species and aid in the prioritization of conservation actions.

Paper:

Hossack, B. R., E. B. Oja, A. Owens, D. Hall, C. Cobos, C. L. Crawford, C. S. Goldberg, S. Hedwall, P. E. Howell, J. Lemos-Espinal, S. MacVean, M. McCaffery, E. Muths, A. H. McCall, C. Mosley, B. H. Sigafus, M. J. Sredl, and J. C. Rorabaugh. 2023. Empirical evidence for effects of invasive American Bullfrogs on occurrence of native amphibians and emerging pathogens. Ecological Applications e2785. https://doi.org/10.1002/eap.2785

Reintroduction programs are growing in use to help recover imperiled species. However, there is still little information on the long-term success of these programs or factors linked with successful establishment of populations. ARMI scientists collaborated with partners from the US Fish and Wildlife Service, Arizona Game and Fish Department, Turner Endangered Species Fund, and university scientists to analyze 25 years of reintroductions for the Chiricahua Leopard Frog in Arizona and New Mexico. The reintroduction program stocks larvae and frogs reared in several captive and semi-captive facilities in the region, as well as egg masses and frogs moved from wild sources. The results from the study can help improve reintroduction success and speed recovery for the Chiricahua Leopard Frog and other species with similar life histories.

Citation

Hossack and others. 2022. Identifying factors linked with population persistence: Lessons learned from 25 years of amphibian translocations. Global Ecology and Conservation 35: e02078. https://doi.org/10.1016/j.gecco.2022.e02078