Amphibian Conservation Research Articles

Groundwater decline has negatively affected the well-preserved amphibian community of Doñana National Park (SW Spain)

Abstract The success of amphibian conservation efforts is highly dependent on the preservation of amphibian breeding habitats. Doñana National Park contains an abundance of ponds with heterogeneous characteristics, which has historically favoured its amphibian community. However, most of the park’s ponds are groundwater dependent, and aquifer overexploitation outside the park is leading to shorter hydroperiods and even desiccation in the pond network. This problem has been exacerbated by the scarcity of rain over the last decade. In 2021-2022, we surveyed the occurrence of the park’s 11 amphibian species, with a view to comparing our findings with those from the last previous survey in 2003-2004. We mapped the species occurrence within the park for the two survey periods. While all 11 amphibian species could still be found in Doñana, their occurrence had decreased across the board. In 2003-2004, 6 species were present across more than 50% of the sampling area. In contrast, 18 years later, such was the case for only two species (Pelophylax perezi and Hyla meridionalis). Declines were greatest for Epidalea calamita, followed by Pelobates cultripes, Triturus pygmaeus, and Lissotriton boscai. The mean number of species per sampling unit (i.e., grid cell) dropped from 4.3 to 3.1. To preserve Doñana’s amphibian community, it is important to restore the park’s pond network, which implies reducing regional groundwater overexploitation.

Amphibian conservation status in Brazil: Spatial patterns, threats, and challenges

Extinction risk assessments are valuable conservation tools, especially for sensitive groups like amphibians, which are facing escalating threats from habitat loss and degradation. In this scenario, Brazil stands out as a pivotal player in amphibian conservation due to its exceptional amphibian diversity. Between 2010 and 2014, 973 amphibian species were assessed in Brazil. More recently, from 2017 to 2018, this number increased to 1096. In this study, we (1) compare the extinction risk status of Brazilian amphibians between the 1st and 2nd assessments; (2) evaluate the reasons for changes in status; (3) identify the main threats and research recommendations; and (4) analyze the spatial patterns of threatened species in relation to protected areas and ecoregions in Brazil. Our findings reveal an increase in the number of threatened species from the first to the second assessment. The categories of Least Concern and Critically Endangered experienced the most significant increases, with 169 and 16 more species, respectively, while the count of Data Deficient species dropped by 71. The primary factor contributing to these changes is the availability of new, more precise information, affecting 134 species, or 85.4% of the cases. Threatened species are predominantly clustered within the Atlantic Forest biome, itself the most endangered biome in Brazil, hosting 46 species, or 78% of the total. Notably, one-third of threatened species in Brazil do not inhabit protected areas and thus require immediate conservation attention. While substantial progress has been made in understanding Brazilian amphibians in recent years, an urgent need persists for fundamental research. This research should encompass taxonomy, natural history, and the evaluation of threat impacts, providing a robust foundation for more effective conservation efforts concerning this group.

The importance of quantifying fitness-determining traits throughout life to assess the application of reproductive technologies for amphibian species recovery

The application of reproductive technologies to amphibian conservation breeding programs is gaining momentum and the field is poised to contribute significantly toward amphibian species recovery. We briefly discuss the opportunities for reproductive technologies to enhance conservation breeding outcomes, including their potential to enhance the genetic management, and in turn, the fitness of threatened species. Despite this potential, an important consideration that is not yet well understood is the degree to which specific reproductive technologies might influence (either enhance, or in some instances potentially decrease) individual fitness and lead to shifts in population viability. The development of a standardised approach to monitoring offspring throughout life-stages to detect changes to morphology, behaviour, physiology, survivorship, and developmental trajectories is essential. The primary focus of this review is to provide a ‘best-practise’ framework for quantifying key fitness determining traits expected to contribute to the fitness of individuals and long-term viability of populations, which will ultimately allow us to progress the field of amphibian reproductive technologies and assess the impact of protocol refinement.

Field-based molecular detection of Batrachochytrium dendrobatidis in critically endangered Atelopus toads and aquatic habitats in Ecuador.

Batrachochytrium dendrobatidis (Bd) is a lethal fungal species that parasitizes vertebrates and is associated with the worldwide decline of amphibian populations. The development of sensitive, rapid detection methods, particularly DNA-based techniques, is critical for effective management strategies. This study evaluates the efficacy of DNA extraction and a portable PCR device in a mountable field laboratory setup for detecting Bd near the habitats of three critically endangered Atelopus toad species in Ecuador. We collected skin swabs from Atelopus balios, A. nanay, and A. bomolochos, and environmental DNA (eDNA) samples from streams in Andean and coastal regions of Ecuador. For eDNA, a comparison was made with duplicates of the samples that were processed in the field and in a standard university laboratory. Our findings revealed Bd detection in eDNA and swabs from 6 of 12 water samples and 10 of 12 amphibian swab samples. The eDNA results obtained in the field laboratory were concordant with those obtained under campus laboratory conditions. These findings highlight the potential of field DNA-based monitoring techniques for detecting Bd in amphibian populations and their aquatic habitats, particularly in remote areas. Furthermore, this research aligns with the National Action Plan for the Conservation of Ecuadorian Amphibians and contributes to the global effort to control this invasive and deadly fungus.

Framework for multi-stressor physiological response evaluation in amphibian risk assessment and conservation

Framework for multi-stressor physiological response evaluation in amphibian risk assessment and conservation

Preparing for a Bsal invasion into North America has improved multi-sector readiness

Western palearctic salamander susceptibility to the skin disease caused by the amphibian chytrid fungus Batrachochytrium salamandrivorans (Bsal) was recognized in 2014, eliciting concerns for a potential novel wave of amphibian declines following the B. dendrobatidis (Bd) chytridiomycosis global pandemic. Although Bsal had not been detected in North America, initial experimental trials supported the heightened susceptibility of caudate amphibians to Bsal chytridiomycosis, recognizing the critical threat this pathogen poses to the North American salamander biodiversity hotspot. Here, we take stock of 10 years of research, collaboration, engagement, and outreach by the North American Bsal Task Force. We summarize main knowledge and conservation actions to both forestall and respond to Bsal invasion into North America. We address the questions: what have we learned; what are current challenges; and are we ready for a more effective reaction to Bsal’s eventual detection? We expect that the many contributions to preemptive planning accrued over the past decade will pay dividends in amphibian conservation effectiveness and can inform future responses to other novel wildlife diseases and extreme threats.

Density-dependent performance of larval and juvenile toads: Implications for amphibian conservation

Density dependent carry-over effects from one life history stage to another can affect the dynamics of populations. Here we study such carry-over effects from the tadpole to the postmetamorphic juvenile stage in an endangered amphibian, the natterjack toad (Epidalea calamita). We raised tadpoles in outdoor aquatic mesocosms at four densities and assessed juvenile performance after metamorphosis in terrestrial mesocosms. High larval density reduced mass at metamorphosis by 50 % and doubled the length of the larval period. Survival was reduced at the high densities. Larger metamorphs had higher survival in terrestrial mesocosms and remained larger than cohort members at the end of the 30-day experiment. Because juvenile survival drives amphibian population dynamics, density-dependent carry-over effects to the juvenile stage are likely to affect population viability. We discuss the implications of the results for amphibian conservation practice, both pond construction programs and surveys of amphibian populations.

Discovery and description of a new species of burrowing frog Sphaerotheca Gnther, 1859 (Anura: Dicroglossidae) from the suburban landscapes of Bengaluru, India.

Recent resolution of prevailing taxonomic ambiguities in the genus Sphaerotheca and new species discoveries from urban/suburban landscapes highlight the need for attention to non-forested habitats for amphibian conservation. In this paper, we review the status of the members of the genus Sphaerotheca and justify the synonymy of Sphaerotheca magadha as a junior synonym of Sphaerotheca swani. The prospects of resurrection of Sphaerotheca swani (herein preliminarily referred to as Sphaerotheca cf. breviceps [swani]) are discussed. In addition, we describe a new species Sphaerotheca varshaabhu sp. nov. from the suburban region of Bengaluru, India. We employ an integrative taxonomic approach to characterize the new species using molecular phylogeny, genetic distance, morphological characters, and geographical isolation as lines of evidence. We also provide a description of vocal repertoire of Sphaerotheca varshaabhu sp. nov. and provide comparative bioacoustics data for four species. This previously undescribed species from the suburban areas of Bengaluru described herein as Sphaerotheca varshaabhu sp. nov. forms a genetically divergent lineage and its genetic distance varied from 3.6% to 12.2% for 16S rRNA with respect to other species of Sphaerotheca. Our phylogenetic analysis for the genus including the new species confirms the synonymy of one recently described species, resulting in 10 valid species in the genus Sphaerotheca. These results emphasize the need for utilizing an integrative taxonomic approach for uncovering hidden diversity of suburban areas. Given these recent discoveries, we advocate for more robust surveys in human dominated areas, so that these amphibians may receive more attention.

Preliminary estimate of a Gray Treefrog (<i>Hyla versicolor</i>) population at a protected site in New Brunswick using photo identification and community science

We provide a preliminary population estimate (n = 120, 95% CI 65–722) of (male) Gray Treefrog (Hyla versicolor) at the Hyla Park Nature Preserve, New Brunswick, Canada’s first amphibian conservation site. As proof of concept, we also demonstrate the efficacy of a minimally invasive photographic identification method (PIM) that uses pattern recognition software for estimating the population of a visually cryptic amphibian that is subject to physiological colour change. Finally, we validate the use of PIM data collected by community participants and the opportunity it provides to engage and educate the local community about amphibian conservation.

Champhibians, a citizen science programme for schools: a project introduction and case study from Malls Mire Local Nature Reserve in Glasgow, Scotland

Champhibians, the “champions of amphibians,” a pond adoption project instigated by Amphibian and Reptile Conservation (ARC), provides an interesting case-study of a citizen science project that was specifically designed for schools. This paper highlights the main aims and benefits of the project by showcasing one of the pilot schools that has participated in the project and adopted a pond at the Malls Mire Local Nature Reserve (LNR) in Glasgow, Scotland. The benefits of this project stem from its links to the school curriculum as well as the connection it establishes between schools, the ARC Trust and managers of local community greenspaces. The importance of outdoor education has long been recognised for benefitting children’s mental health and well-being as well as their relationship with nature. It can help to incorporate several of the United Nations Sustainable Development Goals (UNSDGs) into the curriculum, such as life below water, climate action and life on land, while at the same time providing valuable data for land managers through its citizen science approach.

From single to multiple habitat connectivity: The key role of composite ecological networks for amphibian conservation and habitat restoration

Many graph-based studies consider just one habitat type (breeding habitat) and one ecological process (dispersal) when measuring connectivity. However, in the course of their life cycle, some species use different habitats and are particularly sensitive to their spatial arrangement. We propose a new graph modeling approach that considers heterogeneous habitats and movements when assessing connectivity. Our hypothesis is that a multiple habitat approach is more relevant than a single habitat approach for studying the relationships between connectivity and composite habitat species occurrence. We constructed a bipartite graph with separate categories of nodes for aquatic and terrestrial habitats and an inter-habitat link set. Different connectivity values were measured from the graph depending on the ecological process under study. We then compared our models against field observation data for amphibian communities and tested whether multiple habitat connectivity models provide better predictions. Multiple habitat connectivity was as effective as single habitat connectivity, and often more so, in explaining the presence, abundance, and species richness of amphibian communities. Application to habitat restoration revealed that connectivity gains vary greatly depending on the ecological process, emphasizing the importance of links connecting habitats of different types. Multiple habitat graphs appear promising for incorporating habitat and movement heterogeneity into ecological network modeling. We encourage further theoretical and empirical work on multiple habitat connectivity to consolidate the results and evaluate its full potential, especially for global change issues.

Release trial of captive-bred variable harlequin frogs Atelopus varius shows that frogs disperse rapidly, are difficult to recapture and do not readily regain skin toxicity

AbstractVariable harlequin frogs Atelopus varius have declined significantly throughout their range as a result of infection with the fungal pathogen Batrachochytrium dendrobatidis (Bd). The Panama Amphibian Rescue and Conservation Project maintains an ex situ population of this Critically Endangered species. We conducted a release trial with surplus captive-bred A. varius individuals to improve our ability to monitor frog populations post-release, observe dispersal patterns after freeing them into the wild and learn about threats to released frogs, as well as to determine whether natural skin toxin defences of frogs could be restored inside mesocosms in the wild and to compare Bd dynamics in natural amphibian communities at the release site vs a non-release site. The 458 released frogs dispersed rapidly and were difficult to re-encounter unless they carried a radio transmitter. No frog was seen after 36 days following release. Thirty frogs were fitted with radio transmitters and only half were trackable by day 10. Tetrodotoxin was not detected in the skins of the frogs inside mesocosms for up to 79 days. Bd loads in other species present at sites were high prior to release and decreased over time in a pattern probably driven by weather. No differences were observed in Bd prevalence between the release and non-release sites. This trial showed that refinements of our methods and approaches are required to study captive Atelopus frogs released into wild conditions. We recommend continuing release trials of captive-bred frogs with post-release monitoring methods, using an adaptive management framework to advance the field of amphibian reintroduction ecology.

Importance of Genetic-Fitness Correlations for the Conservation of Amphibians.

Endangered animals suffer from isolation of their habitats. Isolation leads to a reduction in population size as well as a decrease in genetic diversity and a concomitant increase in the risk of extinction. Amphibians are the most endangered vertebrate class. Besides habitat loss, fragmentation and isolation, amphibians are threatened by emerging diseases e.g., chytrid fungus or Ranavirus. By employing experiments, researchers investigate whether changes in genetic diversity within or among isolated populations affect amphibian fitness. While genetic diversity estimates are based on molecular markers, typically microsatellites, fitness is mostly measured as tadpole performance in rearing experiments often under varying environmental conditions. Tadpole performances (e.g., body mass, growth rate and survival) have been found to be negatively affected by low genetic diversity, as several studies have found a positive association between genetic diversity and these fitness traits. Moreover, infection with pathogens also seems to be more likely in individuals or populations with lower genetic diversity. Overall, these genetic-fitness correlations seem to be more pronounced or detectable in smaller, declining populations but not in larger populations. Genomic studies, which sample a larger fraction of the genome, are still scarce in the conservation genetic literature on amphibians. These are likely to increase in upcoming years and may reveal adaptive variants that protect against dangerous pathogens or environmental changes. Altogether, genetic-fitness correlation studies should be a priority in order to develop effective management plans for the genetic rescue of isolated, imperilled amphibian populations.

Among the trees: shade promotes the growth and higher survival of juvenile toads

getation, including trees, significantly shapes microhabitats for amphibians due to the leaf litter input, providing stable shelter, creating a microclimate or indirectly through trophic interactions. It is known that some species can survive in a highly modified urban environment. Species associated with open space can find stable habitats in urban and human-transformed areas, but is the impact of shading (presence of canopy cover) significant in their case? We focus on the effect of solar exposure on the growth rate of juvenile green toads Bufotes viridis in fruit and canopy manipulation treatments. The main aim of the study was to examine the selected habitat traits promoting post-metamorphic growth of the green toad in semi-open enclosures. We investigated differences between exposure/land cover variants, i.e., sunny site (open area with direct solar exposure) and shadow site (shady site with a tree canopy cover). Using imitation fruits and real cherry plum Prunus cerasifera fruits (non-native tree species), we checked wheth­er amphibian growth is related to the additional structure that fruit lying on the ground created (a more heterogeneous surface structure) or to a trophic character (additional food source due to attracting inver­tebrates). We conducted a 40-day rearing experiment in three variants with two replications in semi-open enclosures with 20 juvenile toads each. We found differences in snout-vent length and body mass index in­vestigated due to site exposure during post-metamorphic growth. The survival rate of juvenile toads in the shaded site was higher than in sunny sites. We demonstrated a positive effect of the tree’s shade, regardless of the fleshy fruit’s presence on the ground. Toads benefit from developing at sites with reduced solar ex­posure (i.e., with a tree canopy), resulting in intensive growth and higher survival rate. Thus, there is an opportunity for planners and urban authorities to manage habitats for amphibian conservation purposes by creating a shaded zone, even for open habitat species, especially in transformed areas such as cities. Our results indicate that the beneficial effect of the lying fruit on the growth of juveniles is limited to specific conditions, and understanding this requires further research.

Connectivity, land use, and fish presence influence smooth newt (Lissotriton vulgaris) occurrence and abundance in an urban landscape

IntroductionUrban areas are challenging environments for wetland species with complex habitat requirements and life cycles. However, even semiaquatic species, representing such complex wetland groups, can be provided with adequate conditions through thorough understanding of their habitat requirements coupled with comprehensive wetland management.MethodsWe studied the occurrence and abundance of the smooth newt (Lissotriton vulgaris), a widely distributed amphibian, in an urban landscape in metropolitan Helsinki, Finland. We classified 50 randomly selected urban wetlands based on their connectivity by applying isolation scores counted using principal component analysis (PCA) and measured the occurrence and abundance of smooth newts in these locations.ResultsOur analyses showed well-connected wetland sites to differ significantly in smooth newt occurrence from both isolated and partially connected sites. Additionally, smooth newt abundance in well-connected wetlands differed from isolated sites. A PCA model with residential buildings (negative effect) and aquatic vegetation (positive effect) best explained smooth newt occurrence and total and male abundance, and female newt occurrence was best explained by a model also incorporating forest and natural open areas. Predation pressure by fish negatively influenced both smooth newt occurrence and abundance.DiscussionTighter networks of constructed wetlands and stricter management guidelines for urban wetland planning and fish community management could increase the suitable habitat for smooth newts in urban landscapes. Managing such areas for the common smooth newt offers potential broad benefits to the conservation of other semiaquatic amphibians and reptiles in urban wetlands and to urban wetland biodiversity in general. Our results show that smooth newt presence may indicate sustained wetland connectivity in an urban landscape and could even be used to signal successful urban planning.

Ontogenetic and cohort estimates of tadpole survival for the threatened Betic midwife toad (Alytes dickhilleni) in two contrasting small waterbodies

Abstract Comprehensive knowledge on demographic parameters and early life history traits is essential for an effective amphibian management and conservation. Here, we assessed tadpole survival of Alytes dickhilleni in two contrasting small waterbodies (natural pool vs man-made drinking trough). For the first time in the genus Alytes, tadpole survival was quantified at ontogenetic and cohort level. Overall, low survival values were reported for both study sites, being values in the natural pool (0.16) twice than in the man-made drinking trough (0.07). Ontogenetic and cohort variation was congruent between both study sites, with survival rates decreasing in intermediate developmental stages, and highest values being observed in overwintering as compared to summer tadpoles. Owing to the ongoing decline in Alytes populations, these results can be particularly useful for informing future conservation schemes based on tadpole translocation or reintroduction from wild populations.

Trophic ecology of juvenile amphibians: relative level of myrmecophagy in two anuran species

ABSTRACT Research on trophic niche dimensions is essential to understanding the role of species in ecosystems. In the case of amphibian conservation, it is particularly important to study juveniles, given the vulnerability of this life stage. Here, the diets consumed by juvenile Rhinella arenarum and Odontophrynus sp. were evaluated, with special attention paid to the incidence of ants. Diet composition was quantified by analyzing the amphibians’ stomach contents. The representation of different taxonomic prey groups was determined, and the relationships between the amphibians’ morphological traits and the characteristics of their prey were explored. Diet composition and diversity differed between juveniles of the two species. Juvenile R. arenarum occupied an intermediate position along the specialist-generalist spectrum. Their most commonly consumed prey were ants (mainly Solenopsis and Linepithema) followed by mites. Juvenile Odontophrynus sp. had a more generalist diet. Their most commonly consumed prey were Isopoda followed by Coleoptera and miscellaneous larvae. Snout-vent length (SVL) was greater for juvenile Odontophrynus sp. than for juvenile R. arenarum, but the latter consumed more prey. The results suggest that juveniles of R. arenarum tend to specialize more on ants than do juveniles of Odontophrynus sp.

Current State of Conservation Physiology for Amphibians: Major Research Topics and Physiological Parameters.

Analysis of physiological responses can be used to assess population health, identify threat factors, and understand mechanisms of stress. In addition to this, conservation physiologists have sought to establish potential management strategies for environmental change and evaluate the effectiveness of conservation efforts. From past to present, the field of conservation physiology is developing in an increasingly broader context. In this review, we aim to categorize the topics covered in conservation physiology research on amphibians and present the measured physiological parameters to provide directions for future research on conservation physiology. Physiological responses of amphibians to environmental stressors are the most studied topic, but conservation physiological studies on metamorphosis, habitat loss and fragmentation, climate change, and conservation methods are relatively lacking. A number of physiological indices have been extracted to study amphibian conservation physiology, and the indices have varying strengths of correlation with each subject. Future research directions are suggested to develop a comprehensive monitoring method for amphibians, identify interactions among various stressors, establish physiological mechanisms for environmental factors, and quantify the effects of conservation activities on amphibian physiology.

Natural area visitors’ willingness to pay for amphibian conservation in a global biodiversity hotspot

Transfer of harmful pathogens from imported pet animals to natural populations of wildlife is a new challenge in protected area management. Understanding visitors’ preferences for, and value they place on, protecting biodiversity from such disturbances is important in developing effective management interventions. By conducting a visitor survey at two natural areas in the Southern Appalachian region of the United States, a global hotspot of amphibian biodiversity, this study examined natural area visitors’ willingness to pay (WTP) to conserve wild amphibian populations under two different assumptions for the distribution of WTP – normal and log-transformed. Results from the retained model assuming a normal distribution for WTP showed that visitors were willing to pay US$10.55 (95% CI US$9.61—US$11.50) per visit in donation to ensure the persistence of healthy amphibian populations. Determinants of individual WTP under both model specifications included the perceived threat to amphibians from pathogen transmission in natural areas they visit, their self-assessed familiarity with general knowledge about amphibians, the level of importance they placed on the benefits to humans from amphibian biodiversity, and annual household income. These findings are useful in understanding the economic value of amphibian diversity to natural area visitors, and in assessing the viability of a visitor-supported mechanism to fund projects mitigating anthropogenic threats to amphibian biodiversity.

A guide to conserve amphibian species in Iran

ABSTRACT Globally, amphibians are one of the most threatened vertebrate groups and are hypersensitive to human-imposed habitat changes. Here we explore ways to conserve amphibians in two of the least-known biodiversity hotspots on earth, the Caucasus and Irano–Anatolian regions. We used two techniques: (ⅰ) combining species richness, endemism, and endangerness indices and (ⅱ) a species distribution model (SDM) to identify high-priority areas for Iran’s seven endemic and/or threatened amphibian species. The identified amphibian high-priority areas were then targeted to assess the levels of protection granted by the network of conservation areas (CAs) in Iran. We also computed the species-specific extent of occurrence (EOO) and the area of occupancy (AOO) to detect conservation gaps for the targeted species. Our results indicate that amphibian high-priority areas in Iran are mostly distributed across the Hyrcanian forest in the north and Zagros Mountains in the west. The gap analysis revealed that based on the most optimistic metric, 40% of amphibian hotspots are covered by CAs in Iran. However, the species-specific gap analysis showed that Iran’s CAs perform poorly at representing the EOO of all of the endemic and/or threatened amphibian species. These results suggest that expansion of CAs in Iran is essential for amphibian conservation.