Pond-breeding Amphibian Species Research Articles

Environmental Drivers of Amphibian Breeding Phenology across Multiple Sites

A mechanistic understanding of phenology, the seasonal timing of life history events, is important for understanding species’ interactions and the potential responses of ecological communities to a rapidly changing climate. We present analysis of a seven-year dataset on the breeding phenology of wood frogs (Rana sylvatica), tiger salamanders (Ambystoma tigrinum), blue-spotted salamanders (Ambystoma laterale), and associated unisexual Ambystoma salamanders from six wetlands in Southeast Michigan, USA. We assess whether the ordinal date of breeding migrations varies among species, sexes, and individual wetlands, and we describe the specific environmental conditions associated with breeding migrations for each species/sex. Breeding date was significantly affected by species/sex identity, year, wetland, and the interactions between species/sex and year as well as wetland and year. There was a great deal of variation among years, with breeding occurring nearly synchronously among groups in some years but widely spaced between groups in other years. Specific environmental triggers for movement varied for each species and sex and changed as the breeding season progressed. In general, salamanders responded to longer temperature lags (more warmer days in a row) than wood frogs, whereas wood frogs required longer precipitation lags (more rainy days in a row) than salamanders. Wood frogs were more likely to migrate around the time of a new moon, whereas in contrast, Ambystoma salamander migration was not associated with a moon phase. Ordinal day was an important factor in all models, suggesting that these amphibians require a latency period or similar mechanism to avoid breeding too early in the year, even when weather conditions appear favorable. Male wood frogs migrated earlier than female wood frogs, and male blue-spotted salamanders migrated earlier than female A. laterale and associated unisexual females. Larger unisexual salamanders migrated earlier than smaller individuals. Differences in species’ responses to environmental cues led to wood frogs and A. laterale breeding later than tiger salamanders in colder years but not in warmer years. This suggests that, as the climate warms, wood frog and A. laterale larvae may experience less predation from tiger salamander larvae due to reduced size differences when they breed simultaneously. Our study is one of few to describe the proximate drivers of amphibian breeding migrations across multiple species, wetlands, and years, and it can inform models predicting how climate change may shift ecological interactions among pond-breeding amphibian species.

Survey of the amphibians in “Fânațele Clujului – Copârșaie”, part of the “Dealurile Clujului de Est” (ROSCI0295) Natura 2000 protected area

"As habitat loss poses challenge to conservation, it is becoming increasingly important to address questions about the extent to which connectivity between habitat patches is changing, and how this affects the local population of different species in these patches. The objective of our research was to monitor ponds and the pond-breeding amphibian species in a protected area. Therefore, we conducted day and night surveys, and compare the data collected in 2022 with the results of the latest available survey (2019), to simulate the patch occupancy of amphibian species over a 25-year timeframe. We found that combining the species occupancy data collected from both day and night surveys lead to higher patch occupancy values and higher number of registered individuals, compared to data collected only during daytime. The number of ponds decreased from 2019 to 2022, and further habitat loss could result in the disappearance of the local population if the area continues to dry out. Climate and landscape change could be major contributors to habitat loss in the future, therefore, in order to ensure the persistence of these local populations, we recommend the development of climate and habitat scenarios, and the planning of conservation measures based on these scenarios. Keywords: amphibian conservation, Transylvanian Plain, SPOM"

Bending the curve: Simple but massive conservation action leads to landscape-scale recovery of amphibians

Success stories are rare in conservation science, hindered also by the research-implementation gap, where scientific insights rarely inform practice and practical implementation is rarely evaluated scientifically. Amphibian population declines, driven by multiple stressors, are emblematic of the freshwater biodiversity crisis. Habitat creation is a straightforward conservation action that has been shown to locally benefit amphibians, as well as other taxa, but does it benefit entire amphibian communities at large spatial scales? Here, we evaluate a landscape-scale pond-construction program by fitting dynamic occupancy models to 20 y of monitoring data for 12 pond-breeding amphibian species in the Swiss state Aargau, a densely populated area of the Swiss lowlands with intensive land use. After decades of population declines, the number of occupied ponds increased statewide for 10 out of 12 species, while one species remained stable and one species further declined between 1999 and 2019. Despite regional differences, in 77% of all 43 regional metapopulations, the colonization and subsequent occupation of new ponds stabilized (14%) or increased (63%) metapopulation size. Likely mechanisms include increased habitat availability, restoration of habitat dynamics, and increased connectivity between ponds. Colonization probabilities reflected species-specific preferences for characteristics of ponds and their surroundings, which provides evidence-based information for future pond construction targeting specific species. The relatively simple but landscape-scale and persistent conservation action of constructing hundreds of new ponds halted declines and stabilized or increased the state-wide population size of all but one species, despite ongoing pressures from other stressors in a human-dominated landscape.

Larval development and survival of pond-breeding anurans in an agricultural landscape impacted more by phytoplankton than surrounding habitat.

The destruction of freshwater habitat is a major contributor to biodiversity loss in aquatic ecosystems. However, created or restored wetlands could partially mitigate aquatic biodiversity loss by increasing the amount of available habitat across a landscape. We investigated the impact of surrounding terrestrial habitat and water quality variables on suitability for two species of pond-breeding amphibians (bullfrogs [Lithobates catesbeianus] and Blanchard's cricket frogs [Acris blanchardi]) in created permanent wetlands located on an agricultural landscape. We examined tadpole growth and survival in field enclosures placed in ponds surrounded by agricultural, forested, or grassland habitats. We also evaluated the potential for carryover effects of the aquatic environment on terrestrial growth and overwinter survival of cricket frog metamorphs. We found that habitat adjacent to ponds did not predict tadpole growth or survival. Rather, phytoplankton abundance, which showed high variability among ponds within habitat type, was the only predictor of tadpole growth. Cricket frogs emerged larger and earlier from ponds with higher phytoplankton abundance; bullfrogs were also larger and at a more advanced developmental stage in ponds with higher levels of phytoplankton. Overwinter survival of cricket frogs was explained by size at metamorphosis and there were no apparent carryover effects of land use or pond-of-origin on overwinter growth and survival. Our results demonstrate that created ponds in human-dominated landscapes can provide suitable habitat for some anurans, independent of the adjacent terrestrial habitat.

Pond-Breeding Amphibian Community Composition in Missouri

We examined pond-breeding amphibian community composition at 210 ponds in Missouri between 2002 and 2012 using drift fence, dipnet, and funnel trap data. We encountered a total of 20 pond-breeding amphibian species in the combined surveys. We also examined whether the presence of American Bullfrogs, Lithobates catesbeianus, and fish influenced these patterns of diversity. Our results indicate the presence of American Bullfrogs, fish, and their interaction influenced the community composition of amphibians at these sites but in opposite patterns. American Bullfrogs often had a positive relationship with the total number of species, total caudate species, and total anuran species, whereas fish presence was negatively associated overall with species diversity, and the presence of both American Bullfrogs and fish was negatively associated with anuran species diversity. It is important to have baseline community species composition data from wide geographical ranges so spatiotemporal changes in community structure can be noted and assessed.

Terrestrial distribution of pond‐breeding salamanders around an isolated wetland

Terrestrial habitats surrounding isolated wetlands are a critical resource for many pond-breeding amphibian species, yet few studies have examined the terrestrial distribution of post-metamorphic juveniles and adults. We used an encircling drift fence at a breeding pond in conjunction with partial fences at 90, 172, and 332 m from the wetland to estimate the terrestrial distribution of adult marbled salamanders (Ambystoma opacum; four breeding seasons) and mole salamanders (A. talpoideum; two seasons), as well as the dispersion of newly metamorphosed A. opacum (one summer). For newly metamorphosed A. opacum, 79% emigrated < 90 m from the wetland, and 8% moved beyond 172 m; movement distance was unrelated to body size. Distribution of adult A. opacum varied among years, with an average of 28% (range 23-31%) occurring beyond 172 m in all years. Averaged across two years, 51% of adult A. talpoideum occurred beyond 172 m. Lognormal models provided a good fit to both the juvenile and adult ambystomatid distributions, and parameters differed between age classes, sexes, species, and years within species. For adult A. opacum a buffer radius of 300 m or 340 m, depending on the year, is estimated to include 95% of adults; for A. talpoideum the estimate is 464 m or 501 m. A reanalysis of distribution data for seven ambystomatid species shows that a previous estimate of a 164-m radius to protect 95% of a population underestimates the needed buffer radius by 185 m. Because our study wetland requires a nearly 500 m wide radius to protect 95% of its ambystomatid adults, preservation of similar communities may require much more surrounding terrestrial habitat than previously thought.

Integrating detection probabilities in species distribution models of amphibians breeding in Mediterranean temporary ponds

AbstractAim The imperfect detection of species may lead to erroneous conclusions about species–environment relationships. Accuracy in species detection usually requires temporal replication at sampling sites, a time‐consuming and costly monitoring scheme. Here, we applied a lower‐cost alternative based on a double‐sampling approach to incorporate the reliability of species detection into regression‐based species distribution modelling.Location Doñana National Park (south‐western Spain).Methods Using species‐specific monthly detection probabilities, we estimated the detection reliability as the probability of having detected the species given the species‐specific survey time. Such reliability estimates were used to account explicitly for data uncertainty by weighting each absence. We illustrated how this novel framework can be used to evaluate four competing hypotheses as to what constitutes primary environmental control of amphibian distribution: breeding habitat, aestivating habitat, spatial distribution of surrounding habitats and/or major ecosystems zonation. The study was conducted on six pond‐breeding amphibian species during a 4‐year period.Results Non‐detections should not be considered equivalent to real absences, as their reliability varied considerably. The occurrence of Hyla meridionalis and Triturus pygmaeus was related to a particular major ecosystem of the study area, where suitable habitat for these species seemed to be widely available. Characteristics of the breeding habitat (area and hydroperiod) were of high importance for the occurrence of Pelobates cultripes and Pleurodeles waltl. Terrestrial characteristics were the most important predictors of the occurrence of Discoglossus galganoi and Lissotriton boscai, along with spatial distribution of breeding habitats for the last species.Main conclusions We did not find a single best supported hypothesis valid for all species, which stresses the importance of multiscale and multifactor approaches. More importantly, this study shows that estimating the reliability of non‐detection records, an exercise that had been previously seen as a naïve goal in species distribution modelling, is feasible and could be promoted in future studies, at least in comparable systems.

Adjacent land-use affects amphibian community composition and species richness in managed forests in New Brunswick, Canada

Here, we examine the effects of adjacent land use in a managed forest on pond-breeding amphibian species richness and community composition at 34 New Brunswick, Canada, ponds. Amphibian species richness was negatively correlated with the proportion of roads, precommercial thinning, and hardwood forest and positively correlated with the proportion of wetlands in adjacent lands. These land-use effects peak at 180 m from the ponds. Road density was negatively correlated with Lithobates catesbeiana and Lithobates septentrionalis presence. Precommercial thinning was negatively correlated with Ambystoma spp. presence and positively correlated with Anaxyrus americanus presence. Wetlands were positively correlated with L. septentrionalis and Notopthalamus viridescens presence. Correlations were also found between water table height and A. americanus, Lithobates palustris , and Ambystoma spp. presence. In addition, L. catesbeiana and N. viridescens presence–absence was positively correlated with the proportion of mature and overmature forest on the landscape (at scales of 500 and 1000 m, respectively). Lastly, the proportion of regenerating and sapling forest on the landscape was negatively correlated with L. palustris presence–absence but, by contrast, was positively correlated with A. americanus. These results suggest that the effects of adjacent land use may significantly impact amphibian populations in managed eastern Canadian forests.

Breeding and Recruitment Phenology of Amphibians in Missouri Oak-Hickory Forests

ABSTRACT Knowing the phenologies of species in a region helps guide management and conservation activities in breeding ponds and surrounding terrestrial habitats. We examined the phenology of pond-breeding amphibians in central Missouri oak-hickory forests. Two ponds were monitored for 4 y from 2000–2003 and five other ponds were monitored for 1 y during 2004 using drift fences with pitfall traps. We found 15 species of pond-breeding amphibians, nine of which we captured in sufficient abundance to evaluate breeding phenology. Among the nine species, breeding migrations occur from Feb. to Nov., while subsequent metamorph emigration occurred primarily from May to Oct.. Our ponds were nearly permanent, resulting in salamander-dominated communities in these oak-hickory forests. Pond-use was partitioned by species that differed in their timing of reproduction and post-metamorphic emergence. For example, breeding in the fall gives larval ringed salamanders a potential size advantage over the spring-breeding spo...

Variation in amount of surrounding forest habitat influences the initial orientation of juvenile amphibians emigrating from breeding ponds

Juvenile dispersal is important for the persistence of ​amphibian populations. Previous studies have observed nonrandom orientation in juvenile amphibians emigrating from breeding ponds; however, the environmental cues associated with these movements are not well understood. We examined the emigration behavior of recently metamorphosed juveniles of three pond-breeding amphibian species from three woodland ponds. We found that juvenile small-mouthed salamanders ( Ambystoma texanum (Matthes, 1855)), American toads ( Bufo americanus Holbrook, 1836), and wood frogs ( Rana sylvatica LeConte, 1825) exhibited nonrandom orientation upon exiting the breeding ponds. Furthermore, we found a positive relationship between captures of juvenile small-mouthed salamanders and wood frogs and width of the surrounding forest habitat, indicating that these species are selecting areas with broader forested habitat upon exiting the breeding ponds. Our results indicate that migrating juvenile amphibians may rely on direct environmental cues because the orientation of small-mouthed salamanders and wood frogs was influenced by width of the surrounding forested habitat. These observations support previous studies suggesting that maintaining forest habitat, along at least a portion of breeding ponds, is important for the persistence of amphibian populations.

Emigration Orientation Of Juvenile Pond-breeding Amphibians In Western Massachusetts

Abstract We studied the emigration of juvenile age-class individuals of four species of pond-breeding amphibians at 14 seasonal ponds over four consecutive years in western Massachusetts. Emigration orientation of each species was non-uniform for the majority of pond-years examined. While orientation was decidedly non-uniform in most individual pond-years, combining data from successive years led to a more uniform distribution for each of the study species, although in no case did it actually become statistically uniform. Additionally, while the exact orientation of each species at each pond differed among years in almost all cases, there were some directions with consistently greater than or less than expected use across years for all ponds. Similarly, despite overall differences in orientation of individuals among ponds for a particular species, or among species at a particular pond, there were some consistent directional biases (positive and negative) across ponds and across species. Overall, our resul...

RESPONSES OF POND-BREEDING AMPHIBIANS TO WILDFIRE: SHORT-TERM PATTERNS IN OCCUPANCY AND COLONIZATION

Wildland fires are expected to become more frequent and severe in many ecosystems, potentially posing a threat to many sensitive species. We evaluated the effects of a large, stand-replacement wildfire on three species of pond-breeding amphibians by estimating changes in occupancy of breeding sites during the three years before and after the fire burned 42 of 83 previously surveyed wetlands. Annual occupancy and colonization for each species was estimated using recently developed models that incorporate detection probabilities to provide unbiased parameter estimates. We did not find negative effects of the fire on the occupancy or colonization rates of the long-toed salamander (Ambystoma macrodactylum). Instead, its occupancy was higher across the study area after the fire, possibly in response to a large snowpack that may have facilitated colonization of unoccupied wetlands. Naive data (uncorrected for detection probability) for the Columbia spotted frog (Rana luteiventris) initially led to the conclusion of increased occupancy and colonization in wetlands that burned. After accounting for temporal and spatial variation in detection probabilities, however, it was evident that these parameters were relatively stable in both areas before and after the fire. We found a similar discrepancy between naive and estimated occupancy of A. macrodactylum that resulted from different detection probabilities in burned and control wetlands. The boreal toad (Bufo boreas) was not found breeding in the area prior to the fire but colonized several wetlands the year after they burned. Occupancy by B. boreas then declined during years 2 and 3 following the fire. Our study suggests that the amphibian populations we studied are resistant to wildfire and that B. boreas may experience short-term benefits from wildfire. Our data also illustrate how naive presence-non-detection data can provide misleading results.

Emigration Timing of Juvenile Pond-breeding Amphibians in Western Massachusetts

Abstract Understanding the timing of movement events of pond-breeding amphibians to and from breeding and natal ponds, respectively, is essential to implementing effective conservation and monitoring strategies for this group of vertebrates. In this study, we assessed the emigration timing of newly metamorphosed juveniles of four species of pond-breeding amphibians (Ambystoma maculatum, Ambystoma opacum, Notophthalmus viridescens, and Rana sylvatica) in western Massachusetts from data collected at 14 seasonal ponds during four consecutive years (2000–2003). Results identified emigration “windows” for juveniles of each species during each year and for all years pooled. Additionally, analyses identified considerable intraspecific variation in the timing of emigration among ponds and years for at least three of the four study species. Our results are directly applicable to management strategies (e.g., road-closures) aimed at minimizing human-related impacts (e.g., road mortality) on populations of pond-breed...

Diet of the Gray Treefrog (Hyla Versicolor) in Relation to Foraging Site Location

Despite growing concern over habitat destruction, little is known regarding the activities of pond-breeding amphibians in the terrestrial environment. Yet, because most pond-breeding amphibian species spend the majority of their time in terrestrial habitats, it is important to understand what role terrestrial habitat plays in their life history. We examined the stomach contents of the Gray Treefrog (Hyla versicolor) in central Missouri using a stomach-flushing technique. Treefrogs were stomach-flushed; stomach contents were dried and weighed; and prey items were counted and identified for frogs caught in both artificial arboreal refugia and at breeding ponds. The majority of prey consisted of ants (41.2%) and beetles (29.6%). Both males and females caught in artificial refugia contained greater stomach content mass than those caught at breeding ponds. There was a positive correlation between mass of stomach contents and distance from breeding ponds, with the average number of beetles per stomach increasing with distance from ponds. There was also greater stomach content mass in frogs found in artificial refugia on white oaks than red oaks or sugar maples, but there was no relationship between tree diameter and stomach content mass. These results demonstrate the importance of protecting terrestrial habitat to maintain foraging areas for treefrogs.

Timing of large movement events of pond-breeding amphibians in Western Massachusetts, USA

Understanding the factors influencing the timing of large movement events in pond-breeding amphibians has important conservation implications, especially with regard to establishing road closures aimed at minimizing road mortality. We examined the timing of juvenile emigration and adult immigration in four species of pond-breeding amphibians ( Ambystoma maculatum, Ambystoma opacum, Notophthalmus viridescens, and Rana sylvatica) at 14 seasonal ponds in western Massachusetts from 1999 to 2003. Regression trees were variously successful in producing an effective and parsimonious description and robust prediction of large movement events based on a suite of temporal and meteorological variables. Julian date, degree-days, temperature, precipitation and droughtiness were all important correlates of movement for one or more species and age class. The amount of rainfall during the previous 24 h period was an important variable in four of the five trees built, and degree-days was an important variable in two of the three trees built describing juvenile emigration. In four of six cases, regression trees identified a few days each year that accounted for a large percentage of the total annual movement, and thus offered a practical means to determine when road-closure events designed to minimize road mortality of pond-breeding amphibians during migratory events would be most effectively employed.

Designing Wetlands for Amphibians: The Importance of Predatory Fish and Shallow Littoral Zones in Structuring of Amphibian Communities

Under section 401 and section 404 of the Clean Water Act, permission to degrade existing natural wetlands in the USA may be conditional on restoring or creating ‘replacement’ wetlands. Success of wetland mitigation efforts in adequately replacing lost wildlife habitats depends on our good understanding of key ecological attributes that affect the structure of wetland faunal communities. We examined the effects of the presence of predatory fish, shallow vegetated littoral zone, emergent vegetation cover, wetland age and size on amphibian diversity in 42 replacement wetlands located in the Ohio’s North Central Tillplain ecoregion. We recorded 13 species of pond-breeding amphibians, and the average local species richness (α-richness) was 4.2 ± 1.7 species per site (range 1–7). There is strong evidence for the positive association between amphibian species richness and presence of a shallow littoral zone, and the negative association with presence of predatory fish. There was no evidence for the association between species richness and age, size, amount of forest cover within 200 m, nor the amount of emergent vegetation cover at the study sites. It is estimated that local species richness in wetlands with shallows was 1.76 species higher on average than in wetlands without shallows (95% CI from 0.75 to 2.76). The presence of predatory fish was associated with an average reduction in species richness by an estimated 1.21 species (95% CI from 0.29 to 2.11). Replacement wetlands were placed in areas with little or no existing forest cover, and amphibian species associated with forested wetlands were either rare (eastern newt, spotted salamander) or not present at all (marbled salamander, wood frog). In addition, we surveyed all replacement wetlands constructed under section 401 in Ohio since 1990, and found that predatory fish were present in 52.4% of the sites and that shallows were absent from 42.7% of the sites. Our results indicate that current wetland replacement practices could have a negative effect on the amphibian diversity within our region.

Core terrestrial habitat for conservation of local populations of salamanders and wood frogs in agricultural landscapes

Pond-breeding amphibians require aquatic and terrestrial habitats to complete their lifecycles, and preservation of both habitats is necessary for maintaining local populations. Current wetland regulations focus primarily on aquatic habitats, and criteria to define critical upland habitats and regulations to protect them are often ambiguous or lacking. We examined the association between the presence of seven pond-breeding amphibian species and the landscape composition surrounding 54 wetlands located within the Till Plains and the Glaciated Plateau ecoregions of Ohio, USA. We quantified landscape composition within 200 m of the wetland (“core terrestrial zone”) and the area extending from 200 m to 1 km from the wetland (“broader landscape context zone”). We constructed binary logistic regression models for each species, and evaluated them using Akaike Information Criterion. Presence of spotted salamanders ( Ambystoma maculatum), Jefferson's salamander complex ( A. jeffersonianum) and smallmouth salamanders ( A. texanum) was positively associated with the amount of forest within the core zone. Presence of wood frogs ( Rana sylvatica) was positively associated with the amount of forest within the core zone and the amount of forest within the broader landscape context zone. Presence of tiger salamanders ( A. tigrinum tigrinum) was negatively associated with the cumulative length of paved roads within 1 km of the site, and presence of red-spotted newts ( Notophthalmus v. viridescens) was negatively associated with the average linear distance to the five nearest wetlands. Overall salamander diversity was positively associated with the amount of forest within the core zone, and negatively associated with the presence of predatory fish and cumulative length of paved roads within 1 km of the site. Our results confirm the strong association between the structure of surrounding upland areas and amphibian diversity at breeding ponds, and stress the importance of preserving core terrestrial habitat around wetlands for maintaining amphibian diversity.

The role of introduced mosquitofish (Gambusia holbrooki) in excluding the native green and golden bell frog (Litoria aurea) from original habitats in south-eastern Australia.

The introduction of fish has decimated many amphibian populations through increased predation, primarily on their larvae. Some amphibian species now occupy marginal habitats as a response to the presence of introduced fish predators. Such habitats may include ephemeral water bodies where fish do not usually occur, although breeding in these suboptimal environments may incur some cost to a species if its larvae are not adapted to develop under these conditions. We investigated this scenario of amphibian decline using the endangered green and golden bell frog (Litoria aurea) and the introduced mosquitofish (Gambusia holbrooki) in a factorial experiment to determine the responses of tadpoles to declining water levels and the introduced predator. Tadpoles metamorphosed asynchronously but did not accelerate development in declining water or when housed with mosquitofish. Mass at metamorphosis was 30% less in declining water. Mass increased with time to metamorphosis in constant water-level treatments, but decreased in declining water. Tadpoles did not respond to mosquitofish and were therefore assumed to be naive to this predator. These results suggest that ephemeral habitats may be suboptimal for breeding, and tadpoles appear better suited to develop in permanent water bodies free of introduced fish. Intra-clutch variability in larval development (i.e. bet-hedging) may allow L. aurea to cope with unpredictable pond duration, whereby even permanent water bodies may occasionally dry out. The responses observed in L. aurea suggest that introduced fish may have reduced the suitability of permanent water bodies as breeding sites for other pond-breeding amphibian species. The use of less favourable ephemeral habitats as breeding sites may be responsible for some of the declines reported in amphibians since the 1970s.