https://doi.org/10.1016/j.gecco.2024.e02944.
Amphibians at risk: Effects of climate change in the southwestern North American drylands
The study "Amphibians at Risk: Effects of Climate Change in the Southwestern North American Drylands" employs advanced modeling and ecological analysis to evaluate how climate factors, particularly temperature and precipitation changes, shape amphibian distribution and vulnerability. Here’s an in-depth summary:
Introduction
Drylands, characterized by low water availability, encompass ecosystems prone to climate-induced degradation. Amphibians are disproportionately affected due to their dual life cycle (aquatic and terrestrial) and habitat specificity. The research aims to:
Quantify environmental contributions to amphibian distribution.
Predict habitat responses under future climate scenarios.
Identify species traits linked to increased vulnerability.
Methods
Study Area and Data
Focus: Southwestern U.S. and northern Mexico drylands, delineated by aridity indices.
Species data: Derived from IUCN and environmental layers (e.g., temperature, precipitation, solar radiation, and topography) from WorldClim and other databases.
Categorization: Species were grouped as dryland specialists, rare, or multi-ecoregion, based on their range overlap with drylands.
Species Distribution Modeling (SDM)
Models were calibrated using MaxEnt to identify environmental predictors of species distribution.
Climate scenarios: Four Shared Socioeconomic Pathways (SSPs) were simulated for 2081–2100.
Statistical metrics: Area Under the Curve (AUC) and True Skill Statistic (TSS) validated model performance.
Results
Predictors of Distribution
Key Factors:
Temperature and Precipitation: Most significant drivers, influencing 57% of species' habitat suitability.
Solar Radiation: Critical for thermoregulation but associated with declines at extreme levels.
Topography: Elevation gradients shape species distributions by modifying temperature exposure.
Climate Change Impacts:
48% of suitable habitats are projected to disappear under high-emission scenarios (SSP 585).
Hotspots of habitat loss include semiarid regions in eastern Texas and northern Mexico.
Amphibians in areas of severe drought or high temperature are at heightened risk.
Species Vulnerability
Range Size: Narrow-range species are disproportionately affected.
Status: Critically endangered and endangered species face the highest habitat losses.
Adaptability: Multi-ecoregion species retain some resilience outside drylands, unlike specialists.
Body Size: No strong correlation between body mass and vulnerability was observed.
Discussion
Climate and Habitat Suitability:
Energy-water dynamics govern amphibian biogeography, with temperature influencing breeding, growth, and thermoregulation.
Solar radiation interacts with biotic (e.g., disease) and abiotic (e.g., temperature extremes) factors, amplifying stress.
Fragmentation and Isolation:
Habitat fragmentation isolates populations, reducing dispersal and genetic diversity.
Rare and specialist species face higher risks of extinction due to limited dispersal capabilities.
Implications for Conservation:
Protecting dryland refuges and restoring habitat connectivity are critical.
Conservation strategies must address climate-induced habitat shifts alongside disease threats.
Conclusion
This study quantifies the severe impacts of climate change on amphibians in drylands, emphasizing the need for integrated conservation approaches. It pioneers methods to correlate habitat loss with species traits and environmental pressures, providing critical insights for policymakers. Future research should examine the interplay between climate-induced habitat loss, evolutionary adaptation, and disease ecology.
Andrew R. Blaustein, Lisa K. Belden, Deanna H. Olson, David M. Green, Terry L. Root, Joseph M. Kiesecker
The paper "Amphibian Breeding and Climate Change" explores how climate change impacts the timing of breeding for four North American anuran species (frogs and toads). The authors analyzed long-term data to investigate whether increasing temperatures are causing amphibians to breed earlier. The results showed no statistically significant trend toward earlier breeding for most species, though there were some associations between warmer temperatures and earlier breeding in certain populations. The findings suggest that while climate may affect breeding patterns, the evidence for widespread shifts in amphibian breeding is limited.
Cynthia Carey, Judsen E. Bruzgul, Lauren J. Livo, Margie L. Walling, Kristin A Kuehl, Brenner F. Dixon, Allan P. Pessier, Ross A. Alford, Kevin B. Rogers
Introduction
Background on Chytridiomycosis: Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), has been a significant factor in global amphibian declines. Bd primarily affects the keratinized skin of amphibians, interfering with essential functions like respiration and water balance.
Study Objectives: This study focuses on experimentally inducing Bd infections in boreal toads (Bufo boreas) to better understand how variations in fungal dosage, temperature, and duration of exposure affect toad survival. Additionally, the study investigates whether infection can occur through water containing zoospores and how body size influences survival.
Methods
Toad Collection: Boreal toadlets were collected from Colorado and raised in a controlled environment at the John W. Mumma Native Aquatic Species Restoration Facility. They were assumed to be Bd-free as no pathogen outbreaks had been reported in the hatchery.
Experimental Design:
Toadlets were exposed to different doses of Bd zoospores (ranging from 1 to 10⁶ zoospores) over varying exposure periods (1-3 days). They were divided into groups housed in environments at two constant temperatures (12°C and 23°C).
Infection rates were determined using both histological examination of skin tissues and polymerase chain reaction (PCR) testing for Bd DNA.
The experiments aimed to address four key questions: (1) whether Bd infection can be experimentally induced, (2) how temperature and body mass affect survival, (3) whether Bd transmission can occur through water, and (4) the effects of exposure duration and dosage on survival.
Results
Induction of Bd Infection: Bd infection was successfully induced in boreal toads. Exposure to a high dose of 10⁶ zoospores for 3 days caused skin lesions and eventually led to death in most toads. Histological examination revealed characteristic chytrid thalli in infected skin tissues, confirming the presence of the pathogen.
Effect of Temperature on Survival: Temperature (12°C vs. 23°C) had no significant effect on the survival times of toads, indicating that moderate temperatures do not strongly influence the lethality of Bd infection. However, body mass significantly affected survival, with larger toads surviving longer than smaller ones after exposure to Bd.
Transmission Through Water: The study found that Bd could be transmitted through water. Toads housed in water previously inhabited by infected individuals developed chytridiomycosis, demonstrating that physical contact is not necessary for transmission.
Exposure Duration and Dosage: Both the length of exposure and the dose of zoospores significantly influenced survival rates. Toads exposed to higher doses (10,000 or 10⁶ zoospores) for longer periods (3 days) had shorter survival times compared to those exposed to lower doses or for shorter durations. The survival rate dropped dramatically with higher dosages and longer exposure, with mortality occurring after approximately 15 days in the highest dosage groups.
Discussion
Critical Infection Threshold: The study demonstrated a clear dose-response relationship. The number of zoospores must reach a critical threshold (between 10⁷ and 10⁸ zoosporangia) to cause death. Smaller toads, with less surface area for infection, succumbed faster to the infection than larger toads.
Behavioral Observations: Infected toads exhibited notable changes in behavior, including avoidance of water and decreased respiration rates, possibly as a way to minimize contact with waterborne zoospores and delay reinfection.
Implications for Amphibian Populations: The results suggest that even low levels of Bd exposure can eventually lead to death if the toad is reinfected over time, emphasizing the importance of environmental and ecological conditions that might enhance or reduce the likelihood of Bd outbreaks in the wild.
Larger Toads and Longevity: Larger toads had longer survival times after Bd exposure, which correlates with field observations that adult females (generally larger than males) often survive longer in Bd-affected populations.
Conclusion
The study provides key insights into the dynamics of Bd infections in boreal toads. It confirms that Bd can cause lethal infections under controlled conditions and that both dosage and exposure duration play a critical role in determining survival outcomes. The ability of Bd to spread through water without direct contact underscores the high transmissibility of this pathogen in aquatic environments.
Caroline Zank, Fernando Gertum Becker, Michelle Abadie, Diego Baldo, Raul Maneyro, Marcio Borges-Martins
The paper explores the impact of climate change on the distribution of Neotropical red-bellied toads (Melanophryniscus) and suggests strategies to prioritize species and populations for conservation. It identifies that many species of this genus are vulnerable to climate changes, with habitats projected to shrink. The research also uses models to assess current and future distributions, proposing conservation efforts based on the urgency of threat and species' capacity to adapt.
The paper found that climate change is likely to have significant effects on the distribution of Neotropical red-bellied toads (Melanophryniscus). Many species are projected to experience habitat loss as suitable climatic conditions shrink and shift. The study identifies specific species and populations that are at the greatest risk and suggests conservation priorities based on vulnerability and adaptive capacity. The research underscores the need for targeted conservation strategies, especially for species that inhabit restricted or fragmented environments.
Broadscale and fine-scale variables predict the occurrence of a stream-breeding bufonid
This study examines habitat use and conservation needs for the Arizona toad (Anaxyrus microscaphus), a stream-breeding species facing threats from climate change and habitat loss in Arizona, New Mexico, Utah, and Nevada. Researchers conducted surveys in 500-meter stream sections over 2021 and 2022, focusing on larval stages of the Arizona toad across a range of habitat types. They evaluated both broadscale (large environmental features like climate and topography) and fine-scale (localized vegetation, substrate, and water depth) variables to predict toad occurrence.
Objectives and Context
Amphibians, including the Arizona toad, are experiencing alarming declines due to factors like habitat loss, invasive species, and climate change. The study’s primary goals were to determine:
Broadscale predictors of Arizona toad occupancy.
Fine-scale habitat variables linked to the presence of larval toads.
The Arizona toad, a conservation priority, depends on riparian and streamside environments susceptible to environmental changes such as altered water availability from climate shifts.
Methods
The study area included multiple riparian zones along the Mogollon Rim and other areas within Arizona. To survey toad occupancy and habitat preferences, researchers divided these areas into 500-meter segments along streams and conducted daytime visual surveys in spring and summer, targeting larval stages. Occupancy modeling used remotely sensed data on climate, habitat heterogeneity, and topographic features, alongside fine-scale data like vegetation cover, substrate, and algae presence. Principal component analyses (PCA) were applied to reduce and refine environmental variables.
Key Findings
Broadscale Predictors: Arizona toad occupancy was best predicted by climate variables, specifically less extreme high temperatures and lower winter precipitation, which were positively associated with toad occupancy. This indicates that toads prefer areas with stable temperature and precipitation patterns.
Fine-Scale Habitat Preferences: Larval toads showed a preference for habitats with shallow water, canopy cover, pebble substrate, and low woody debris presence. Toads were often found in shaded areas with complex riparian vegetation that could offer protection from temperature extremes and predators.
Occupancy and Detection Rates: Occupancy was relatively low across surveyed sites, with detection rates highest in cooler, shaded habitats. This confirms the rarity of the Arizona toad and highlights the need for targeted conservation efforts to maintain suitable riparian habitats.
Implications for Climate Adaptation: The study suggests that as climate change progresses, regions with extreme temperatures and altered precipitation patterns could see a decline in toad populations due to habitat loss. Conservation strategies should prioritize preserving riparian complexity and water availability to support both the Arizona toad and other sensitive species.
Conservation Implications
Maintaining riparian vegetation, which provides essential canopy cover, shallow water areas, and complex substrates, is crucial for toad conservation. This habitat configuration supports not only the Arizona toad but also other species reliant on streamside ecosystems in the arid Southwest. As water availability declines with climate change, strategic water and land management will be essential to sustain these vulnerable populations.
This study reinforces the importance of considering multiple scales in habitat selection research and the need for long-term monitoring of climate variables to inform conservation actions for amphibians like the Arizona toad.
Somaye Vaissi, Azam Chahardoli, Zahra Minoosh Siavosh Haghighi, Pouria Heshmatzad
The study explores how metal nanoparticles impact green toads (Amphibia, Anura) under climate change conditions. It examines the potential conservation risks posed by nanoparticles such as silver and titanium dioxide, which can interact with the toads’ biology in harmful ways, especially as the climate shifts. The research emphasizes the importance of monitoring these effects to develop better conservation strategies for amphibians facing environmental stressors.
Yang, Luoyang; Huang, Lixin; Zhang Huabin; Lee, Pingshin; Zhang, Naijing; Cai, Ruiqing; Li, En; Pan, Tao; Wu, Xaiobing
The paper titled "Habitat Stability and Distribution Pattern Response to Global Climate Change in a Widespread Species, the Asiatic Toad (Bufo gargarizans)" explores how climate change impacts the distribution and habitat suitability of the Asiatic toad. Using the Maxent model and GIS technology, the authors predict that while the species will lose some suitable habitats, it will expand its range to higher latitudes and elevations in China by 2050 and 2070. Key environmental variables like rainfall during the wettest season and temperature during the driest season significantly affect its habitat suitability.
David S. Pilliod, Erin Muths, Rick D. Scherer, Paul E. Bartelt, Paul Stephen Corn, Blake R. Hossack, Brad A. Lambert, Rebecca McCaffery, Christopher Gaughan
Introduction
Amphibian chytrid fungus: Batrachochytrium dendrobatidis (Bd) is responsible for chytridiomycosis, which has caused significant declines in amphibian populations worldwide. However, little is known about its long-term demographic effects on infected species.
Objective: This study aims to examine how Bd infection affects the survival rates and population growth of boreal toads (Bufo boreas, now Anaxyrus boreas) in the Rocky Mountains, focusing on both infected and uninfected populations.
Methods
Study Population: The researchers collected capture-recapture data from three populations of wild boreal toads in the Rocky Mountains over six years. Two populations were infected with Bd, while one was uninfected, allowing comparisons of survival between diseased and healthy groups.
Sampling Sites: The three sites, selected for their established populations, included the Lost Trail National Wildlife Refuge in Montana (LT), an oxbow pond in Wyoming (BR), and Denny Creek in Colorado (DC). LT and BR were infected with Bd, while DC was not.
Data Collection: The team conducted multiple capture sessions during the breeding season (2003–2008). During each session, toads were captured, tagged with passive integrated transponders (PIT), and skin swabs were taken for Bd testing. The focus was primarily on male toads since they were more frequently captured.
Statistical Analysis: Using capture-recapture models (Cormack-Jolly-Seber models) and reverse-time models, the researchers estimated survival probabilities and population growth rates for the infected and uninfected populations. Environmental factors like temperature and humidity were also analyzed for their potential impact on survival and Bd prevalence.
Results
Prevalence of Bd: The study confirmed the presence of Bd at two sites (LT and BR), with prevalence rates of 62% and 53%, respectively. No Bd was detected at DC, confirming its status as uninfected.
Survival Rates: Infected toads at LT and BR had significantly lower survival probabilities than uninfected toads. The disease reduced annual survival rates by 31–42%. For example, infected toads at LT had an average survival rate of 42%, while uninfected toads had survival rates of 73–77%.
Population Decline: Over six years, the populations at the infected sites declined by 5–7% annually, while the uninfected population remained stable. This slow decline suggested that chytridiomycosis functions as a chronic, low-level disease, rather than causing immediate, rapid declines.
Environmental Covariates: Although environmental factors like cold temperatures during breeding were weakly correlated with increased survival, the direct effects of Bd on survival were stronger than any indirect effects from environmental conditions.
Discussion
Chronic Disease: The findings indicate that chytridiomycosis is operating as a chronic disease in these boreal toad populations, reducing survival without causing rapid population crashes. Some infected individuals are able to survive year to year, and there is evidence that infected toads can clear Bd from their systems.
Host-Pathogen Coexistence: The study provides evidence that some amphibian populations may coexist with Bd. Although the disease reduces survival, populations are not immediately driven to extinction. The ability of infected toads to survive and possibly recover suggests that resistance or behavioral adaptations may be at play.
Conservation Implications: The slow decline of infected populations calls for long-term monitoring and conservation strategies that address both disease management and environmental changes. The relatively stable population growth at the uninfected site offers hope for maintaining amphibian populations in areas where Bd is absent.
Conclusion
The study demonstrates that Bd can reduce the survival probability of boreal toads, leading to slow population declines, but it also suggests that infected populations may persist for extended periods. The disease operates more as an enzootic condition rather than causing mass mortality, highlighting the importance of monitoring amphibian populations in Bd-infected areas.
Erin R. Zylstra, Robert J. Steidl, Don E. Swann, Kristina Ratzlaff
Introduction
Focus on Hydrology and Amphibians: The paper investigates how hydrologic variability affects population dynamics, particularly survival and recruitment, of the lowland leopard frog (Lithobates yavapaiensis) in an arid environment. Amphibians are especially vulnerable to changes in water availability, and understanding these dynamics can inform conservation efforts.
Research Area: The study is based on 16 years of survey data from the Sonoran Desert, specifically intermittent mountain streams in southern Arizona, where hydrologic variability strongly influences amphibian populations.
Objectives
The main objective is to evaluate how the availability of surface water impacts both adult frog survival and recruitment into the adult age class. The study also examines long-term population trends and how environmental factors, particularly water availability, influence demographic rates.
Methods
Study Species: The lowland leopard frog, an aquatic obligate, inhabits low-order intermittent streams. This species is highly dependent on surface water for breeding and survival.
Field Surveys: Over 16 years, 162 pools across four canyons were surveyed, documenting the presence of surface water and adult frogs. Observers conducted visual encounter surveys and mark-resight methods to estimate frog movement and population dynamics.
Environmental Data: Data were collected on surface water availability (measured as the proportion of pools containing water), and canyon elevation. The connectivity between frog populations and the number of pools per complex were also considered.
Results
Survival Rates: Monthly survival of adult frogs ranged from 0.72 to 0.99 during summer and from 0.59 to 0.94 in winter. Survival was strongly associated with the availability of surface water—when more pools contained water, survival increased significantly.
Recruitment: The recruitment of juvenile frogs into the adult population also varied with water availability, ranging from 1.9 to 3.8 frogs per season. Recruitment occurred mostly during winter and was positively correlated with the amount of surface water.
No Systematic Population Decline: Despite hydrologic variability and other environmental pressures, the study found no long-term trend of population decline over the 16-year study period, although frog abundance fluctuated across seasons and years.
Discussion
Hydrologic Dependence: The findings highlight the crucial role of water availability in sustaining frog populations. Frogs require surface water for breeding, and prolonged droughts or reductions in water could lead to population declines.
Climate Change Concerns: With climate change expected to reduce precipitation and increase temperatures in desert regions, the availability of surface water could become more limited, potentially threatening amphibians that depend on aquatic environments. The study emphasizes the need to preserve riparian habitats and hydrologic processes in arid ecosystems to protect vulnerable species.
Conservation Recommendations: The authors recommend protecting the structures and ecosystem processes that maintain surface water availability in arid regions, as this will be key to conserving amphibians like the lowland leopard frog.
Conclusion
Water as a Critical Factor: The study underscores that water availability is a primary driver of population dynamics in the lowland leopard frog. Conservation efforts should focus on mitigating threats to water sources, especially in the face of climate change, to ensure the long-term survival of amphibian populations in arid environments.
Key Points
Urbanization Threats: Over a third of amphibian species are at risk due to urbanization, which leads to habitat loss, fragmentation, isolation, and degradation. Amphibians, sensitive to both terrestrial and aquatic changes, face challenges from various urbanization-driven factors like habitat destruction, pollution, and human disturbance.
Species Response to Urbanization:
Variable Responses: Different amphibian species show different levels of sensitivity to urbanization. Species with generalist habitat needs and lower dispersal requirements tend to survive better in urban areas. In contrast, species requiring specific habitats or longer dispersal tend to struggle.
Key Drivers: Urbanization impacts amphibians mainly through habitat loss and fragmentation, changes in hydrology, increased pollution, introduction of exotic species (predators and competitors), and human interference like light and noise pollution.
Framework for Assessing Amphibian Survival: The authors propose a conceptual framework that includes four critical components:
Habitat Availability: The reduction and fragmentation of natural habitats due to urban growth limit the suitable environments for amphibians. Urban wetlands and ponds are often lost or altered, and their isolation inhibits amphibian movement between habitats.
Habitat Quality: Vegetation loss, hydrological changes, introduction of non-native species, pollution, and human disturbances reduce the quality of remaining habitats. Poor quality habitats, particularly those affected by urban runoff, can act as ecological traps.
Species Availability: The ability of amphibians to survive urbanization also depends on whether suitable species are present in or near urban areas. Populations within cities or towns must be large enough to colonize newly created or restored habitats.
Species Response: Different amphibians respond differently based on their life-history traits. Species that are habitat generalists and have lower dispersal needs may adapt better to urban environments.
Challenges and Conservation Strategies:
Habitat Creation and Restoration: Artificial habitats like garden ponds can support some amphibian species, though their ecological value depends on design and management. Urban conservation efforts should focus on maintaining natural hydrology and reducing pollutants.
Mitigating Habitat Loss: Conservation strategies should aim at preventing further habitat loss, maintaining connectivity between habitats, and enhancing both aquatic and terrestrial habitats to sustain amphibian populations.
Research Needs: There is a need for more data on amphibian ecology in urban environments, particularly in tropical and developing regions. Long-term, large-scale studies are required to better understand the impact of urbanization and to develop more effective conservation methods.
Conclusion
The paper concludes that amphibian conservation in urban areas requires a multi-faceted approach that addresses both habitat availability and quality. Conservation strategies should prioritize maintaining connectivity between habitats, reducing the impacts of human disturbance, and mitigating the negative effects of exotic species and pollution.
The document provides a comprehensive review of the complex factors affecting amphibian populations in urban landscapes and emphasizes the need for targeted conservation strategies to protect these vulnerable species.
Need to read again, I forgot most of this paper
Brent H. Sigafus, Blake R. Hossack, Erin L. Muths, and Cecil R. Schwalbe - 2014
Background
Chytridiomycosis: A disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) has led to significant declines in amphibian populations worldwide.
Geographic Focus: The study is centered on the Buenos Aires National Wildlife Refuge (BANWR) in southern Arizona, which provides a unique habitat for various amphibian species.
Objectives
The primary goal was to determine the prevalence of Bd in amphibian populations at BANWR.
The study aimed to assess how environmental factors might influence Bd prevalence.
Methods
Sampling: Researchers collected amphibians from various sites within BANWR between 2015 and 2016.
Species: They focused on several amphibian species common to the region, including the Sonoran Desert toad (Incilius alvarius), spadefoot toads (Spea spp.), and treefrogs (Hyla spp.).
Testing for Bd: Skin swabs were taken from amphibians to test for the presence of Bd using quantitative polymerase chain reaction (qPCR), a sensitive method for detecting the fungal DNA.
Environmental Variables: Data on temperature, humidity, and habitat characteristics were collected to analyze correlations with Bd prevalence.
Results
Prevalence Rates: The study found varying prevalence rates of Bd among the different amphibian species sampled. Some species exhibited a higher infection rate, while others had low or no detectable infections.
Species-Specific Insights: Certain species, like the Sonoran Desert toad, showed higher susceptibility to Bd, suggesting some species are more affected than others.
Environmental Correlations: The study found correlations between Bd prevalence and specific environmental conditions, including temperature and humidity levels, indicating that these factors might play a role in the spread and severity of chytridiomycosis.
Discussion
Implications for Conservation: The findings highlight the ongoing risk that Bd poses to amphibian populations in the region. The study underscores the need for monitoring amphibian health and implementing conservation strategies to mitigate the impact of this pathogen.
Further Research: The authors recommend further studies to explore the dynamics of Bd transmission in various habitats and among different amphibian species.
Conclusion
The study at BANWR contributes valuable data on Bd prevalence in Arizona, emphasizing the critical need for continued surveillance of amphibian populations to understand and combat the effects of chytridiomycosis in the region.
Significance
This research provides insights into the ecological impacts of Bd, demonstrating the importance of habitat management and species protection in areas vulnerable to amphibian diseases.
Celeste M. Dodge, Cathy Brown, Amy J. Lind, Roland A. Knapp, Lucas R. Wilkinson, Vance T. Vredenburg
The paper "Historical and contemporary impacts of an invasive fungal pathogen on the Yosemite toad" examines the effects of the fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes the fatal amphibian disease chytridiomycosis. The study focuses on the Yosemite toad (Anaxyrus canorus), a species that has experienced population declines due to this pathogen. The researchers explore both historical data and modern infection trends to assess how the fungus continues to impact the species, offering insights into potential conservation measures and ecological consequences
Historical Data:
The research includes a retrospective analysis of 719 museum specimens (collected between 1915 and 2005) and 1678 live samples collected from the wild (between 2004 and 2012).
The study found that Bd likely coincided with historical Yosemite toad population declines, with mass die-offs noted as early as the late 1970s.
Infection Patterns:
The pathogen is now widespread across the toad’s range.
The likelihood of Bd infection is associated with certain biotic and abiotic factors such as life stage, elevation, and precipitation.
Juvenile toads were found to have the highest infection rates, with some exceeding Bd infection loads known to be fatal in other amphibian species.
Population Impact:
The researchers conclude that Bd may have played a significant but previously unrecognized role in the decline of the Yosemite toad population.
The disease continues to affect survival and recruitment, leading to depressed population growth and increasing extinction risk for the species.
Conservation Implications:
These findings provide crucial insights for recovery efforts targeting this species, emphasizing the need for strategies to mitigate Bd’s impact.
The study suggests that many other species might have experienced similar declines before Bd was identified in 1998
The study "Nothing a Hot Bath Won't Cure" by Forrest and Schlaepfer (2011) explores how water temperature influences the prevalence of the amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) in lowland leopard frogs. Conducted across multiple sites in Arizona, the research showed that warmer water significantly decreases Bd infection rates. The study emphasizes that amphibians in warmer habitats may naturally avoid or mitigate Bd infection, with infection rates nearly absent above 30°C. These findings highlight potential conservation strategies that leverage warm microhabitats to protect susceptible amphibian species.
Need to read the paper
Limited impact of chytridiomycosis on juvenile frogs in a recovered species | Oecologia
need to finish reading this
A. Kasler, J. Ujszegi, D. Holly, B. Uveges, A. M. Moricz, D. Herczeg, A. Hettyey
The paper titled "Metamorphic Common Toads Keep Chytrid Infection Under Control, but at a Cost" investigates how Bufo bufo toadlets respond to infection by Batrachochytrium dendrobatidis (Bd), the fungus responsible for chytridiomycosis. The study finds that while the toadlets are able to limit the intensity of the infection, they experience significant costs, such as reduced body mass and lower levels of toxin (bufadienolides) production. Although they can manage Bd infection without severe symptoms, the chronic impact on their fitness may hinder long-term survival and adaptability.
Survivorship in Wild Frogs Infected with Chytridiomycosis | EcoHealth
need to read this one
The paper "Effects of Amphibian Chytrid Fungus on Individual Survival Probability in Wild Boreal Toads" by Pilliod et al. (2010) investigates the impact of chytridiomycosis, a disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), on survival rates in wild populations of boreal toads (Bufo boreas) in the Rocky Mountains. The authors focus on three populations, two of which are infected by Bd, while one remains uninfected, to compare survival rates and evaluate the demographic impacts of Bd.
Key Findings and Methods:
Study Sites and Population Data: The study is conducted over six years at three sites in Montana, Wyoming, and Colorado, including annual data collection through capture-recapture methods. Male toads were primarily studied due to their higher detectability and return rates.
Survival Impact of Bd: Toads infected with Bd exhibited a reduction in average annual survival probability by approximately 31-42% compared to uninfected toads at infected sites. Interestingly, uninfected toads in infected populations had similar survival rates to those in the uninfected population, suggesting that the presence of Bd primarily impacts infected individuals.
Chronic, Low-Level Population Decline: Infected populations showed an average annual decline of 5-7%, while the uninfected population maintained stable numbers. This slow decline contrasts with previous observations of rapid population declines due to chytridiomycosis, suggesting that Bd can act as a chronic, low-level disease rather than causing immediate population collapse.
Environmental and Temperature Effects: The study evaluated environmental factors, particularly temperature and frost frequency, which might affect Bd infection dynamics and host survival. Although some correlation with colder breeding conditions was observed, environmental variables showed limited overall impact on survival, suggesting that Bd infection itself is the primary factor affecting survival probabilities.
Implications for Bd and Toad Populations: The results indicate that some amphibian populations may coexist with Bd in the wild, and Bd may not always be acutely lethal. This coexistence could reflect potential adaptations or environmental conditions that limit the pathogenicity of Bd, potentially allowing populations to persist despite infection.
Conclusions: This study contributes to understanding the variability in population responses to Bd infection and highlights that Bd does not uniformly cause extinction-level declines across all infected amphibian populations. The findings underscore the importance of long-term monitoring and demographic assessments for effective conservation management of Bd-affected amphibian populations.
This research provides valuable insight into the host-pathogen dynamics of Bd, suggesting a complex interplay between disease, host resilience, and environmental conditions.
Kristina Ratzlaff
The thesis "Dynamics of Chytrid Fungus (Batrachochytrium dendrobatidis) Infection in Amphibians in the Rincon Mountains and Tucson, Arizona" by Kristina Ratzlaff (2012) presents an in-depth study of Bd (chytrid fungus) infections in three amphibian species: Hyla arenicolor, Rana yavapaiensis, and Rana catesbeiana in southern Arizona. The research aims to identify patterns in Bd prevalence and infection intensity, investigating how factors such as species, location, elevation, season, and life stage influence these patterns. The study also evaluates the potential role of R. yavapaiensis as a reservoir of Bd infection for H. arenicolor.
Key points:
Bd Prevalence & Intensity:
Bd prevalence and infection intensity varied significantly by species, location, and other environmental factors. R. yavapaiensis showed the highest Bd prevalence and infection intensity, while H. arenicolor exhibited the lowest.
Species Differences: Bd prevalence was highest in R. yavapaiensis, intermediate in R. catesbeiana, and lowest in H. arenicolor, likely due to differences in aquatic vs. terrestrial habits and environmental exposure.
Location & Elevation:
Bd prevalence and infection intensity in H. arenicolor and R. yavapaiensis were linked to location and elevation in the Rincon Mountains. Prevalence in H. arenicolor increased with elevation, but the relationship was complex, depending on species interactions and other local factors.
R. yavapaiensis in backyard ponds exhibited higher Bd infection rates compared to those in natural habitats, possibly due to stagnant water and higher density of frogs in these artificial ponds.
Seasonal & Life Stage Variability:
Bd infections in H. arenicolor were more prevalent in winter and spring compared to summer and fall, with zoospore loads highest in the spring. There were no significant seasonal patterns in R. yavapaiensis.
Tadpoles of H. arenicolor generally tested negative for Bd, while metamorphosed frogs had variable infection rates.
Itraconazole Treatment:
The study also examined the use of itraconazole, an antifungal medication, to treat Bd infections in R. yavapaiensis from a backyard pond. Results showed that itraconazole was not effective in reducing winter mortality due to chytridiomycosis.
Implications for Conservation:
The study emphasizes the conservation risks posed by Bd in amphibian populations, particularly the role of R. yavapaiensis as a potential reservoir species. It highlights the importance of understanding local environmental and ecological factors in managing Bd infections.
The paper "Effect of amphibian chytrid fungus (Batrachochytrium dendrobatidis or Bd) on apparent survival of frogs and toads in the western USA" by Russell et al. investigates the impact of Bd infection on the survival rates of multiple frog and toad species across the western United States. This study addresses the challenges of estimating the effects of infectious diseases, such as Bd, on wildlife survival rates. Using hierarchical models and over a decade of capture-mark-recapture data, the researchers assessed survival in four species of threatened or endangered frogs (Rana draytonii, R. muscosa, R. pretiosa, R. sierrae) and the boreal toad (Anaxyrus boreas) across multiple sites in California, Oregon, Wyoming, and Montana.
Key Findings:
Impact on Frogs and Toads: Bd was found to reduce apparent survival rates in all studied frog species. For ranid frogs, survival reduction ranged from 6-15%, depending on species and sex. For boreal toads, the effects were species and location-dependent, with Bd-infected toads showing up to a 55% reduction in survival in Wyoming, although estimates for the Montana population were less definitive.
Long-Term Disease Effects without Immediate Mortality Events: The study observed that Bd negatively impacts amphibian survival rates over time, even without causing large-scale, visible die-offs. This suggests that Bd’s impacts might be chronic rather than catastrophic, making its effects difficult to detect without long-term, detailed monitoring.
Environmental Factors and Host Characteristics: The results indicated that survival differences varied by species, sex, and location, with female frogs generally having higher survival rates than males. Bd prevalence was higher in certain populations and appeared to be associated with higher detection rates for infected individuals. Additionally, the environmental context of each population might influence Bd’s effect on survival rates, as environmental factors and host-pathogen interactions varied among species and locations.
Methodology:
The researchers employed robust design models in a Bayesian framework to manage missing data and variations in survey effort across the study sites. Individual Bd status was treated as a dynamic variable since it could change year-to-year, and random effects were included to account for differences across years and species.
Conclusions:
The study emphasizes the need for understanding the chronic impacts of Bd on amphibian survival to inform conservation strategies effectively. These insights underline that managing Bd in wild populations requires long-term monitoring to capture the gradual yet significant toll on survival that may accumulate without immediate, visible population crashes.
need to read this one
Mason J. Ryan, Ian M. Latella, J. Tomas Giermakowski, Howard L. Snell
The report "Current Status of the Arizona Toad (Anaxyrus microscaphus) in New Mexico: Identification and Evaluation of Potential Threats to its Persistence" (2014) focuses on the population trends, threats, and conservation of the Arizona toad in New Mexico. The research found that 34% of historical breeding sites were still occupied, with the presence of chytrid fungus (Bd) and hybridization with A. woodhousii posing serious threats. Environmental factors, such as habitat loss due to drought, forest fires, and drying of streams, further jeopardize populations. Conservation efforts and habitat management strategies are recommended to prevent further declines.
The study used several methods to measure the threats to the Arizona toad:
Chytrid Fungus (Bd): Swab samples from toads were collected and analyzed using qPCR for the presence of Bd.
Hybridization: Historical records and morphological analyses of museum specimens were reviewed to detect potential hybridization with A. woodhousii.
Habitat Loss: Researchers conducted call surveys at historical breeding sites, monitoring water levels and recording evidence of drying streams, drought impacts, and the aftermath of forest fires.
Climate Change: Long-term drying trends and forest fire frequency were assessed by analyzing stream conditions and environmental changes over time
need to read this one
https://conbio.onlinelibrary.wiley.com/doi/10.1111/cobi.12063
needs review (road mortality)
Estimating annual vertebrate mortality on roads at Saguaro National Park, Arizona
The paper, titled "Estimating Annual Vertebrate Mortality on Roads at Saguaro National Park, Arizona," examines the impacts of vehicle-induced mortality on vertebrate wildlife in the Saguaro National Park (SNP). The researchers modified an existing estimator, initially created for assessing bird mortality from wind turbines, to calculate the average annual number of vertebrates killed by vehicles on park roads.
Key Findings:
Methodology:
Data was collected from 1994 to 1999 across 76.6 km of roads within and around the park. Surveys were conducted weekly by driving along these roads, noting vertebrate carcasses, which were identified by taxonomic group (amphibians, reptiles, birds, mammals) where possible.
Additional walking surveys were performed to determine the detection probability, as many carcasses were missed by drivers.
Carcass persistence was also examined by marking carcasses and observing their rate of disappearance due to scavenging or other factors.
Mortality Estimates:
The study estimated an average of 29,377 vertebrate deaths annually (1.1 per km per day), with amphibians and small reptiles representing the largest proportions of roadkill.
Mortality rates varied seasonally, with higher rates during the monsoon season (July to October), when vertebrate activity is higher in the Sonoran Desert.
Impact of Detection and Persistence:
Carcass detection by drivers was relatively low, with only about 6.5% of carcasses visible to drivers compared to walkers, especially for small vertebrates like amphibians and reptiles.
The average carcass persistence time was found to be around 3.2 days. This persistence rate, coupled with the low detectability, led to adjustments in the mortality estimates to better reflect the actual numbers.
Ecological Implications:
The research underscores the potential for significant impacts on wildlife populations due to road mortality. For instance, small and less detectable species might experience declines due to high mortality rates, impacting local biodiversity.
The study suggests that these high levels of vertebrate roadkill should be a concern for park and regional transportation management, advocating for mitigation measures like wildlife-friendly road crossings and barriers.
Management Recommendations:
The authors recommend collaborative efforts between the park and regional planners to minimize road density and implement mitigation strategies, such as fencing and animal underpasses/overpasses, especially in areas with high wildlife mortality.
This study highlights a critical human-wildlife conflict in protected areas and the need for better transportation planning to preserve biodiversity within and around parks like SNP.
The document outlines a validated protocol for monitoring genetic diversity within species using environmental DNA (eDNA) in amphibians, specifically the common frog (Rana temporaria). Here’s a detailed summary:
Objective
Due to a global decline in amphibian populations, there is a need for efficient methods to monitor species abundance and genetic diversity. This study developed and validated an eDNA-based protocol that could be used to assess genetic diversity in amphibians, especially in pond-breeding species like Rana temporaria.
Key Findings
eDNA for Genetic Diversity: The use of eDNA has been established for species detection in aquatic environments, but its application in assessing within-species genetic diversity, especially in amphibians, is less explored. This study fills that gap by investigating the common frog's mitochondrial DNA (mtDNA) haplotypes through eDNA sampling.
Advantages of eDNA: Traditional methods of monitoring amphibians, especially pond-breeders, are labor-intensive and challenging. eDNA offers a non-invasive, efficient, and potentially more accurate method for monitoring population genetics.
Methodology
Study Area: The study was conducted in the Province of Trento, Italy, known for diverse populations of Rana temporaria. Genetic data from tissue samples collected in previous studies were used as a reference for comparison.
Sampling Process:
Water samples were collected from 10 wetland sites over three years (2019-2021). Three replicates of temporal and spatial samples were collected.
The samples were filtered, and DNA was extracted using specialized kits. The focus was on amplifying a fragment of the COI gene, which is a standard barcode region for species identification.
eDNA Protocol Optimization:
The sampling protocol was optimized for different life stages of Rana temporaria (e.g., egg, tadpole, adult), and the efficiency of spatial and temporal replicates was evaluated. The study found that sampling in early spring (T1) provided the best results.
Field and lab protocols were carefully designed to avoid contamination and ensure reliability.
Bioinformatics and Data Analysis:
Sequencing results were compared to reference genetic data, with statistical methods used to compute genetic diversity estimates (haplotype and nucleotide diversity).
The study identified 10 haplotypes across the three Alpine lineages of Rana temporaria. Genetic diversity estimates from eDNA were strongly correlated with tissue-based reference data.
Results
Success of eDNA Protocol: Rana temporaria DNA was detected in 32 of the 72 water samples collected. Most positive results came from early spring samples, with high variability in amplification success across spatial and temporal replicates.
Haplotype Detection: The eDNA approach successfully identified haplotypes at eight out of the 10 sites, demonstrating the reliability of the method for genetic monitoring.
Correlation with Reference Data: The number of haplotypes detected by eDNA was strongly correlated with traditional tissue-based methods. The study showed significant statistical correlations in genetic diversity indices (haplotype diversity and nucleotide diversity) between eDNA and tissue samples.
Discussion
The protocol demonstrated the feasibility of using eDNA to estimate within-species genetic diversity. This non-invasive method could significantly enhance amphibian conservation efforts, especially for species in remote or challenging habitats.
The study suggests sampling during early life stages, particularly in early spring, as the optimal strategy for eDNA-based genetic monitoring. The protocol’s sensitivity to sampling conditions and site-specific factors (e.g., habitat type, seasonal changes) was noted.
Conclusion
The validated eDNA-based protocol offers a cost-effective and reliable tool for monitoring genetic diversity in amphibians. It can complement traditional methods and potentially be used in long-term monitoring programs. Additionally, it holds promise for broader applications in amphibian conservation and the detection of invasive species.
This approach contributes to biodiversity conservation by providing a method for regular, standardized genetic monitoring, aligning with global conservation goals like the Aichi Biodiversity Targets.
This is the best idea ever and we have to get this started in TMA!
Uses bug migration nights for amphibians to educate volunteers and help amphibians!
Volunteers come out to road systems in mass to help move amphibians across the road without being hit.
This document discusses the issue of amphibian crossing in Arcadia National Park, and a new study being implemented by Acadia Science Fellow and University of Maine Graduate student Marisa Monroe.
The study will focus on amphibian road crossings to identify areas where the animals are crossing for management purposes.
This research is largely run by a citizen science outreach program.
In the amphibian section of "Plants and Animals in the Yoeme World," the authors delve into the cultural and ecological aspects of toads and frogs, highlighting various species and their significance within the Yoeme culture.
Toads (Bufonidae)
General Overview:
The term voovok is used for toads, with kaureepa referring specifically to the larger species, such as the Sonoran Desert Toad (Incilius alvarius) and the Cane Toad (Rhinella horribilis). Toads are noted for their bumpy skin and paratoid glands behind their eyes.
Toads emerge primarily with summer rains, forming large breeding aggregations marked by loud male calls.
Species Highlighted:
Incilius alvarius (Sonoran Desert Toad): Known as kaureepa, this large toad is culturally significant, particularly in rain ceremonies. It is one of the few species to emerge before summer rains.
Anaxyrus cognatus (Great Plains Toad): A medium-sized toad found in Arizona and Sonora, known for its dark green blotches.
Anaxyrus kelloggi (Little Mexican Toad): A regionally endemic species in coastal thornscrub areas of Sonora.
Frogs (Anura)
Cultural Significance:
Frogs, referred to as vatat, hold importance in Yoeme traditions, where they are believed to assist in spiritual transitions. The tadpole, known as sivo’oli, can refer to the young of either frogs or toads.
Species Highlighted:
Agalychnis dacnicolor (Mexican Leaf Frog): An agile treefrog found along the Río Yaqui, known for laying eggs in shrubs that overhang ponds.
Rana catesbeiana (American Bullfrog): The largest frog in the region, characterized by mottled skin. It is a voracious predator and has contributed to the decline of native frog populations.
Rana yavapaiensis (Lowland Leopard Frog): A medium-sized frog documented in irrigation ditches and is now often replaced by the American bullfrog in its habitat.
Conservation Issues
The report discusses the declining populations of amphibians due to habitat loss, climate changes, and the impact of invasive species like the American bullfrog. The cultural context of amphibians within Yoeme traditions is emphasized, advocating for conservation efforts that align with Indigenous knowledge and practices
Notes:
DMT can be a powerful tool in treating multiple mental health disorders, especially depression and PTSD.
It is an illegal substance, but other similar substances like ayahuasca have begun to be decriminalized in many states.
These drugs are marketed as a "healing modality for emotional trauma" that can be used when conventional methods fail.
Paper does not mention the detriment to the toad at all, but it does consistently report that the poison is taken from I. alvarius.
Toad Poaching Is a Thing Now Because of Psychedelics - InsideHook
Notes:
Basically, just paraphrases the NYT article.
Notes:
Talks about a scientific study at Johans Hopkins that is using Psilocybin to treat addiction with high success rates.
Discusses the different anti-drug movements in the US and how they impacted drug use, especially psychedelics.
Does not include any information about DMT
Notes:
need to finish reading this
A Threatened Toad's Hallucinogenic Secretions Are in High Demand
Notes:
Discusses the poaching incident at Stur Pass.
need to finish reading
Notes:
This paper interviews Robert so the cultural importance is well represented.
5-MeO-DMT is legal in Mexico, making it a go to spot for using the drug. There are resorts in Mexico that are marketed as DMT retreats, with many celebrities taking part and giving rave reviews.
Majority of reported poaching is in Mexico.
5-MeO-DMT is a schedule 1 drug in the US.
You cannot grab a toad without a game and fish license (**I believe this is just a hunting license, I should check on this).
This paper does highlight the insect / toad relationship.
Discusses that they are an indicator species that is likely at risk from other threats such as climate change and drought already, and that poaching could cause a tipping point for the animals.
Mentions this paper- "up to 40% of amphibians worldwide are threatened by extinction in the next 50-100 years."
Mentions Chytrid as well.
Describes the "violence" of using the toad for DMT, as well as pointing out that there is a synthetic version.
Quotes Andrew Weil at UA (Integrative Medicine), "there is very little difference" between synthetic and toad harvested DMT.
Notes:
Talks more about "retreat centers," where people pay anywhere from $250 (east Texas woods) to $8500 (Tulum, Mexico) in order to consume the toxin.
Does immediately bring up concerns for the SDT populations.
Discusses a split in the "medicine apostles" between guides who will only use synthetic for the toad's survival, vs those who refuse to stop using DMT harvested directly from the toad.
Says New Mexico has the toad listed as threatened, citing excessive collection among on the factors. Also mentions extirpation in California.
Mentions negative human interactions such as death of one person who took the substance.
Compares SDT to the threat to the Asian River Turtle, which is facing extinction risk because of habitat loss and a belief that they can cure cancer.
Touches on the issue with breeding farms potentially causing chytrid fungus outbreaks.
Describes how the connection to Seri people practicing this as a "cultural practice" is not true and was only introduced to the Seri in 2011.
Points out that many of the bufo-toxins in the toad's secretions are actually toxic and can cause death.
Stop licking psychedelic Sonoran Desert toads, National Park Service says - The Washington Post
Notes:
need to read still
Notes:
Basically just documents two individuals taking toads in Arizona, some very simple comments from Randy Babb at AZGF.
Notes:
need to watch / read still
Stop licking psychedelic Sonoran Desert toads, National Park Service says - The Washington Post
Notes:
need to read still
The paper "Toad in the Road: Biocultural History and Conservation Challenges of the Sonoran Desert Toad" by Robert A. Villa (2023) explores the complex interactions between humans and the Sonoran Desert Toad (Incilius alvarius), which produces the potent psychedelic 5-MeO-DMT. The paper covers the toad's natural history, its exploitation for the psychedelic market, and the conservation challenges it faces, including habitat loss, illegal harvesting, and cultural appropriation of Indigenous knowledge. It emphasizes the need for biocultural reconciliation and sustainable conservation strategies to protect the species and its ecosystem.
Key topics discussed include:
Biocultural History: The Sonoran Desert Toad is culturally significant in its native regions, with myths tied to rain and fertility among Indigenous peoples, though its use as a psychedelic medicine lacks solid historical evidence.
Exploitation and Misuse: The discovery of the toad’s secretions containing 5-MeO-DMT in the 1960s led to the exploitation of the species in the psychedelic wellness movement, raising ethical and ecological concerns. Modern for-profit practices have often fabricated Indigenous origins, leading to biocultural erosion and damaging the conservation of the species.
Conservation Challenges: The rising demand for toad secretions, driven by celebrities and wellness influencers, has led to overharvesting and population decline. The report highlights how the illegal collection disrupts the natural population dynamics, as toads removed from their habitats struggle to survive.
Legal and Ethical Considerations: The toad is protected in parts of its range, but enforcement is weak. The paper advocates for stricter protections, better public awareness campaigns, and scientific research into synthetic alternatives to 5-MeO-DMT to relieve pressure on wild populations.
Conservation Strategies: Villa calls for conservation approaches that balance Indigenous knowledge and scientific methods, addressing not only the biological needs of the species but also the cultural and ethical dimensions of its use.
NPS Tells Visitors Not to Lick Toads With Poison Smoked by Joe Rogan - Business Insider
Notes:
need to watch / read still