Amphibian Abundance Research Articles

Amphibians in agricultural landscapes: the habitat value of crop areas, linear plantings and remnant woodland patches

AbstractMitigating the negative impacts of agriculture on amphibians requires knowledge of how different land uses affect species distribution and community composition. In the case of frogs, there is currently insufficient information on their use of terrestrial habitats in cropping landscapes to inform conservation planning. We examined how four different farmland types (linear plantings, cereal crops, grazing paddocks and woody mulch) and crop harvesting influenced amphibian abundance, richness, body condition and movement. We found the abundance of frogs was significantly higher in linear plantings compared to grazing paddocks and adjacent patches of remnant woodland vegetation. However, species richness and abundance of three individual species did not vary significantly between farmland types. For the most common frog Uperoleia laevigata, body condition was higher at the edges of the woody debris treatment (coupled with higher abundance) and lower in farmland with debris and linear plantings. The body condition of Limnodynastes tasmaniensis and L. interioris was not influenced by farmland type. Frog abundance and condition was largely unaffected by crop harvesting. However, frogs were less common after harvesting at the edges of farmland and within remnant patches. Movement patterns did not suggest mass movement out of crops after harvest, where almost half of all individuals recaptured remained within the farmland. These results suggest that some generalist frog species may have an affinity for habitats within agricultural paddocks, particularly when key habitat features like plantings are present. However, we found overall frog richness was low and did not differ between remnant patches, edges and farmland which may be an indication of habitat degradation within terrestrial habitats across the landscape. Although protection of remnant native vegetation is important, conservation strategies for the protection of amphibians will be ineffective if they do not consider the variety of land uses and the relationships of different species and their microhabitats within and outside of patches.

Connectivity among wetlands matters for vulnerable amphibian populations in wetlandscapes

Wetlands have been degraded and destroyed, resulting in the decline of many wetland-dependent species populations. Many conservation efforts are based on protection of individual wetlands; however, fluxes of energy, materials and organisms between wetlands create important structural and functional connections upon which several species depend. We investigated the role of individual wetlands within a wetlandscape in sustaining an amphibian population. Wetlandscapes were represented as networks, where nodes were wetlands and links were flows of organisms described by an amphibian population model. Relationships between a wetland’s connectivity to the other wetlands and the abundance of amphibians under different wetland management strategies were examined. The first finding was that wetlands within a network can be classified into sinks (where local mortality exceeds birth rate), sources (where local birth rate exceeds mortality), and pseudo-sinks (where excessive immigration maintains the population above the carrying capacity). These three wetland classes have low, medium, and high Indegree (a parameter reflecting a wetland’s connectivity), respectively. The second finding was that management interventions in wetlands have different consequences according to the wetland’s Indegree: wetland removal has the worst impact on amphibian populations if the wetland is a source, and wetland restoration has the best impact if the wetland is a pseudo-sink. These findings provide support for policies that managing wetlands not as independent objects but as integral parts of the wetlandscape.

Can rice field channels contribute to biodiversity conservation in Southern Brazilian wetlands?

Conservation of species in agroecosystems has attracted attention. Irrigation channels can improve habitats and offer conditions for freshwater species conservation. Two questions from biodiversity conservation point of view are: 1) Can the irrigated channels maintain a rich diversity of macrophytes, macroinvertebrates and amphibians over the cultivation cycle? 2) Do richness, abundance and composition of aquatic species change over the rice cultivation cycle? For this, a set of four rice field channels was randomly selected in Southern Brazilian wetlands. In each channel, six sample collection events were carried out over the rice cultivation cycle (June 2005 to June 2006). A total of 160 taxa were identified in irrigated channels, including 59 macrophyte species, 91 taxa of macroinvertebrate and 10 amphibian species. The richness and abundance of macrophytes, macroinvertebrates and amphibians did not change significantly over the rice cultivation cycle. However, the species composition of these groups in the irrigation channels varied between uncultivated and cultivated periods. Our results showed that the species diversity found in the irrigation channels, together with the permanence of water enables these man-made aquatic networks to function as important systems that can contribute to the conservation of biodiversity in regions where the wetlands were converted into rice fields. The conservation of the species in agriculture, such as rice field channels, may be an important alternative for biodiversity conservation in Southern Brazil, where more than 90% of wetland systems have already been lost and the remaining ones are still at high risk due to the expansion of rice production.

Amphibians distribution and habitats in the southwestern region of Saudi Arabia.

This study surveyed 205 wetland sites in the Southwestern Saudi Arabia. We found seven species of amphibians (Anura), which belong to four families: Bufonidae; which includes four species, Sclerophrys tihamica; S. Arabica, Duttaphrynus dhufarensis, and Bufotes viridis; Hylidae, represented by only one species, the tree frog Hyla savignyi; Ranidae, which represented by one species, Pelophylax ridibundus and finally the Dicroglossidae, represented by one species, Euphlyctis ehrenbergii. The reasonable amount of rain received in southwest Arabia, and habitat diversity contribute to the relative abundance of amphibians in the region. Five types of wetland habitats were found in the study area. Valley streams, irrigated farms, seasonal ponds, dam reservoir and lagoons of treated sewage water. The current study revealed the wide spread of amphibians in southwestern Saudi Arabia than what had been reported earlier and confirmed the presence of the Bufotes viridis at three new sites in Asir Heights. It also showed the wide spread of S. arabica in all types of habitats in the southwestern region of Saudi Arabia. Habitat degradation was evident in the region, which might lead to species loss.

Seasonal and Land Use Effects on Amphibian Abundance and Species Richness in the Sakaerat Biosphere Reserve, Thailand

Habitat destruction and degradation in the tropics have led to a dramatic increase in altered habitats. Understanding the impacts of these disturbed areas on biodiversity will be critical to future conservation efforts. Despite heavy deforestation, Southeast Asia is underrepresented in studies investigating faunal communities in human-modified landscapes. This project assessed the herpetofaunal community in dry dipterocarp forest, secondary disturbed forest, and Eucalyptus plantations in the Sakaerat Biosphere Reserve. In May, June, and September of 2015, we surveyed using 10 passive trapping arrays. Both the Eucalyptus plantations and secondary disturbed forest habitats (224 and 141 individuals, respectively) had higher amphibian abundance than the dry dipterocarp forest (57 individuals), but we observed significant seasonal variation in amphibian abundance. During the wetter month of September, we recorded higher numbers of amphibian individuals and species. In particular, we noted that distance to a streambed influenced amphibian abundance during the rainy season. The three most abundant species in May and June were Microhyla fissipes, Fejervarya limnocharis, and Microhyla pulchra. In September, the three most abundant species were Microhyla fissipes, Glyphoglossus molossus, and Kaloula mediolineata.Our findings suggest that seasonal resources should be considered when conducting monitoring programs and making conservation decisions for amphibians.

Responses of Wetland Ecosystems to Drought-Induced Fish Eliminations

Landscape alterations can alter fish occurrence and abundance in wetlands. By increasing turbidity in wetland ponds, fishes can induce a shift from a clear- to a turbid-water state, resulting in reduced plant and amphibian abundance. In 2012, a drought reduced water levels and eliminated fishes from many wetlands of the prairie-pothole region (PPR) in the Midwestern United States. Our study objective was to evaluate if fish eliminations were associated with changes in wetland condition. A one-way ANOVA was used to compare the magnitude of change in parameters indicative of wetland condition (turbidity, plant cover and taxon richness, and tiger-salamander (Ambystoma tigrinum) biomass and numerical abundance) from 29 Iowa PPR wetlands between 2010 and 2011 (pre-drought) and 2014–2015 (post-drought) among wetlands where 1) all fishes were eliminated 2) large-bodied fishes were eliminated, 3) small-bodied fishes were eliminated, 4) fishes were retained, and 5) fishes were never detected. Turbidity decreased and plant cover increased more where large-bodied fishes were eliminated compared to the other groups. Changes in tiger-salamander biomass and abundance and plant-taxon richness were not different among groups. Results indicate that wetlands can shift from a turbid- to a clear-water state following drought and elimination of large-bodied fishes.

São Tomé Island Endemic Treefrogs (Hyperolius spp.) and Land-Use Intensification: A Tale of Hope and Caution

Forest degradation is a major driver of the global biodiversity declines. However, responses to forest degradation vary greatly between taxa and are predominantly understudied. This study investigates the effects of land-use change on the endemic amphibian fauna of São Tomé Island (Central Africa), where a fast-growing human population increases pressure on forest resources. We sampled acoustic data on reed frog ( Hyperolius spp.) abundance at eight transects in each of four land-use categories, representing different levels of forest degradation: old-growth forest, secondary forest, agroforest, and horticulture. While Hyperolius molleri was most abundant in secondary forest and horticulture, Hyperolius thomensis was almost exclusively found in agroforest. We interpret these differences based on reproductive traits, since both species deposit terrestrial eggs and have aquatic larvae, but reproduce in different microhabitats. H. molleri utilizes open water bodies bordered by vegetation for calling and oviposition, which human disturbance has made available in secondary forest and horticulture. In contrast, H. thomensis breeds in water-filled tree holes (phytotelmata), which predominantly occurred in agroforest, often within coral trees ( Erythrina spp.). This first study on Santomean amphibian abundances revealed that H. molleri and H. thomensis males exhibit distinct nonlinear responses to forest degradation and may reap some benefit from human habitat alteration. However, despite their apparent tolerance to some anthropogenic disturbance, further land-use intensification may reduce overall habitat suitability for these and other endemic species.

Seasonality and microhabitat selection in a forest-dwelling salamander.

Many small terrestrial vertebrates exhibit limited spatial movement and are considerably exposed to changes in local environmental variables. Among such vertebrates, amphibians at present experience a dramatic decline due to their limited resilience to environmental change. Since the local survival and abundance of amphibians is intrinsically related to the availability of shelters, conservation plans need to take microhabitat requirements into account. In order to gain insight into the terrestrial ecology of the spectacled salamander Salamandrina perspicillata and to identify appropriate forest management strategies, we investigated the salamander's seasonal variability in habitat use of trees as shelters in relation to tree features (size, buttresses, basal holes) and environmental variables in a beech forest in Italy. We used the occupancy approach to assess tree suitability on a non-conventional spatial scale. Our approach provides fine-grained parameters of microhabitat suitability and elucidates many aspects of the salamander's terrestrial ecology. Occupancy changed with the annual life cycle and was higher in autumn than in spring, when females were found closer to the stream in the study area. Salamanders showed a seasonal pattern regarding the trees they occupied and a clear preference for trees with a larger diameter and more burrows. With respect to forest management, we suggest maintaining a suitable number of trees with a trunk diameter exceeding 30cm. A practice of selective logging along the banks of streams could help maintain an adequate quantity of the appropriate microhabitat. Furthermore, in areas with a presence of salamanders, a good forest management plan requires leaving an adequate buffer zone around streams, which should be wider in autumn than in spring.

Assessing the impacts of the decline of Tsuga canadensis stands on two amphibian species in a New England forest

AbstractDisturbances such as outbreaks of herbivorous insects and pathogens can devastate unique habitats and directly reduce biodiversity. The foundation tree species Tsuga canadensis (eastern hemlock) is declining due to infestation by the nonnative insect Adelges tsugae (hemlock woolly adelgid). The decline and expected elimination of hemlock from northeastern U.S. forests is changing forest structure, function, and assemblages of associated species. We assessed 10 years of changes in occupancy, detection probability, and relative abundance of two species of terrestrial salamanders, Plethodon cinereus (eastern red‐back salamander) and Notopthalmus viridescens viridescens (eastern red‐spotted newt), to the experimental removal in 2005 of T. canadensis at Harvard Forest. Salamanders were sampled under cover boards and using visual encounter surveys before (2004) and after (2005, 2013, 2014) canopy manipulations in replicate 0.81‐ha plots. In 2004, occupancy of P. cinereus was 35% lower in stands dominated by T. canadensis than that in associated mixed‐hardwood control stands, whereas detection probability and estimated abundance of P. cinereus were, respectively, 60% and 100% greater in T. canadensis stands. Estimated abundance of N. v. viridescens in 2004 was 50% higher in T. canadensis stands. Removal of the T. canadensis canopy increased occupancy of P. cinereus but significantly reduced its estimated detection probability and abundance. Estimated abundance of N. v. viridescens also declined dramatically after canopy manipulations. Our results suggest that ten years after T. canadensis loss due to either the adelgid or pre‐emptive salvage logging, and 50–70 years later when these forests have become mid‐successional mixed deciduous stands, the abundance of these salamanders likely will be <50% of their abundance in current, intact T. canadensis stands. This study adds to our understanding of how forest disturbance, directly and indirectly caused by invasive species, can contribute to declines in the relative abundance of amphibians.

Testing Rapid-Assessment Models for the Conservation of Woodland Vernal Pools in South-Central Pennsylvania

Abstract The conservation of woodland vernal pools is a priority for land managers throughout the Northeast. They are a focus of conservation efforts because several amphibian species breed exclusively in these unique wetlands. Vernal-pool protection efforts could benefit from the development of rapid, cost-efficient, and accurate tools for assessing these temporally dynamic amphibian-communities. In this study, we evaluated a rapidassessment method comprised of 3 predictive equations that use measures of habitat quality as indicators of the diversity, richness, and abundance of amphibians in vernal pools in south-central Pennsylvania. To test the models, we implemented the suggested field protocol to acquire estimates of habitat quality. We entered these estimates into the predictive equations to provide projections of amphibian diversity, richness, and abundance. We then directly measured these amphibian-community metrics to compare them with the predicted values. We detected substantial disparity betwe...

Desarrollo larval de anfibios anuros en un río impactado por urbanización: efecto de factores ambientales

En este trabajo se estudio el efecto de variables ambientales sobre la abundancia y el desarrollo larval de anuros, en un rio urbanizado de la provincia de San Luis, Argentina. Abundancia y riqueza de larvas, temperatura del agua y caudal fueron relevados, en siete sitios con diferente grado de urbanizacion del rio Volcan, durante cuatro meses. Las larvas se identificaron a nivel de especie, y en una muestra se midio su longitud y se estimo su estadio; se encontraron larvas de tres especies: Rhinella arenarum, Hypsiboas pulchellus y Odontophrynus occidentalis. La abundancia y riqueza de larvas variaron entre sitios y, aunque no se correlacionaron significativamente con la urbanizacion, fue posible identificar eventos puntuales de impacto sobre la abundancia. Las larvas de anuros crecieron y se desarrollaron en sitios con diferentes grados de perturbacion, y fue posible establecer efectos del caudal, la temperatura del agua y la antropizacion en el crecimiento y desarrollo. Este trabajo proporciona informacion basica relevante sobre el desarrollo de anuros en ambientes loticos y los efectos de variables ambientales en sitios con impacto urbano. Los conocimientos generados son de utilidad para analisis integrados de calidad ambiental y como herramientas para medidas basicas de conservacion de la anurofauna nativa.Palabras clave: abundancia, larvas, impactos ambientales.

Diversity and abundance of amphibian species in the Guguftu highland and Chefa wetland, Amhara Regional State, Ethiopia

Objective: To describe the population status, abundance and diversity of amphibians found in Guguftu highland and Chefa wetland. Methods: The present study dealed with amphibian diversity at Guguftu highland and Chefa wetland during the period of August 2015 to September 2015. Transect line and visual encounter survey methods were used in careful visual estimation and amphibians were recorded in all possible habitats of the study area. Results: The total of 251 individuals of amphibians within 12 species grouped into 5 families were recorded in the Guguftu highland and Chefa wetland. Chefa wetland had the highest species abundance as well as richness with a total of 231 individuals falling in 11 species. Conclusions: This study reveals that the Chefa wetland is rich in amphibian diversity and supports many more species. Further studies are needed on molecular basis, population structure, habitat use by amphibians for better understanding and also imposing several conservation strategies in Chefa wetland.

Movement and survival of an amphibian in relation to sediment and culvert design

ABSTRACTHabitat disturbance from stream culverts can affect aquatic organisms by increasing sedimentation or forming barriers to movement. Land managers are replacing many culverts to reduce these negative effects, primarily for stream fishes. However, these management actions are likely to have broad implications for many organisms, including amphibians in small streams. To assess the effects of culverts on movement and survival of the Idaho giant salamander (Dicamptodon aterrimus), we used capture‐mark‐recapture surveys and measured sediment in streams with 2 culvert types (i.e., unimproved culverts, improved culverts) and in streams without culverts (i.e., reference streams). We predicted culverts would increase stream sediment levels, limit movement, and reduce survival of Idaho giant salamanders. We also determined the effect of sediment levels on survival of salamanders because although sediment is often associated with distribution and abundance of stream amphibians, links with vital rates remain unclear. To estimate survival, we used a spatial Cormack–Jolly–Seber (CJS) model that explicitly incorporated information on movement, eliminating bias in apparent survival estimated from traditional (i.e., non‐spatial) CJS models caused by permanent emigration beyond the study area. To demonstrate the importance of using spatial data in studies of wildlife populations, we compared estimates from the spatial CJS to estimates of apparent survival from a traditional CJS model. Although high levels of sediment reduced survival of salamanders, culvert type was unrelated to sediment levels or true survival of salamanders. Across all streams, we documented only 15 movement events between study reaches. All movement events were downstream, and they occurred disproportionately in 1 stream, which precluded measuring the effect of culvert design on movement. Although movement was low overall, the variance among streams was high enough to bias estimates of apparent survival compared to true survival. Our results suggest that where sedimentation occurs from roads and culverts, survival of the Idaho giant salamander could be reduced. Though culverts clearly do not completely block downstream movements of Idaho giant salamanders, the degree to which culvert improvements affect movements under roads in comparison to unimproved culverts remains unclear, especially for rare, but potentially important, upstream movements. © 2016 The Wildlife Society.

Biodiversity effects and rates of spread of nonnative eucalypt woodlands in central California

Woodlands comprised of planted, nonnative trees are increasing in extent globally, while native woodlands continue to decline due to human activities. The ecological impacts of planted woodlands may include changes to the communities of understory plants and animals found among these nonnative trees relative to native woodlands, as well as invasion of adjacent habitat areas through spread beyond the originally planted areas. Eucalypts (Eucalyptus spp.) are among the most widely planted trees worldwide, and are very common in California, USA. The goals of our investigation were to compare the biological communities of nonnative eucalypt woodlands to native oak woodlands in coastal central California, and to examine whether planted eucalypt groves have increased in size over the past decades. We assessed site and habitat attributes and characterized biological communities using understory plant, ground-dwelling arthropod, amphibian, and bird communities as indicators. Degree of difference between native and nonnative woodlands depended on the indicator used. Eucalypts had significantly greater canopy height and cover, and significantly lower cover by perennial plants and species richness of arthropods than oaks. Community composition of arthropods also differed significantly between eucalypts and oaks. Eucalypts had marginally significantly deeper litter depth, lower abundance of native plants with ranges limited to western North America, and lower abundance of amphibians. In contrast to these differences, eucalypt and oak groves had very similar bird community composition, species richness, and abundance. We found no evidence of "invasional meltdown," documenting similar abundance and richness of nonnatives in eucalypt vs. oak woodlands. Our time-series analysis revealed that planted eucalypt groves increased 271% in size, on average, over six decades, invading adjacent areas. Our results inform science-based management of California woodlands, revealing that while bird communities would probably not be affected by restoration of eucalypt to oak woodlands, such a restoration project would not only stop the spread of eucalypts into adjacent habitats but would also enhance cover by western North American native plants and perennials, enhance amphibian abundance, and increase arthropod richness.

Amphibian diversity increases in an heterogeneous agricultural landscape

As a group amphibians are the vertebrates most affected by anthropic activity, particularly by agriculture. The rapid advance of the agricultural frontier makes it important to identify the role of agroecosystems as habitat supply for amphibians. We analyzed the differences in amphibian assemblages and populations between habitats with different plant covers and different degrees of human intervention in northwestern Argentina. For three years we conducted 114 high frequency trap samplings to quantify abundance, specific composition and species richness of amphibian assemblages in three habitat types (lemon and sugarcane crops and secondary forest) of a piedmont agroecosystem of Tucumán province. Crops hosted more species and individuals than secondary forests, but the specific composition of forest was different from that of crops suggesting that they could be complementary. Although the assemblage abundance of every observation responded to climate, the strong effect of sampling year was not related to climatic factors suggesting that there might be long term fluctuations that were not analyzed. We also found that responses to agricultural practices were species specific, so no generalizations about these practices should be done. Our study shows that cultivated areas are not hostile environments for amphibians since they can lodge huge amphibian populations and that the occurrence of disturbances associated to agricultural practices is not necessarily reflected in a decrease in the abundance and richness of amphibians in the short term. However, our results also show that forested lands are necessary to lodge some specialist species which are very rare in the croplands. This suggests that environmental heterogeneity generated by the combination of natural and cultivated patches can increase biodiversity at landscape scale because this allows the coexistence of species related to either kind of environment.

Reserva Natural Laguna Blanca, Departamento San Pedro: Paraguay’s First Important Area for the Conservation of Amphibians and Reptiles?

Geographical sampling bias and restricted search methodologies have resulted in the distribution of Paraguayan reptiles and amphibians being patchily known. Available data is almost entirely based on brief collecting trips and rapid ecological inventories, often several decades apart, which inevitably struggle to detect more inconspicuous species and patterns of abundance. This has led to a deficit in our knowledge of the true distribution and abundance of Paraguayan reptiles and amphibians. The establishment of the NGO Para La Tierra at Reserva Natural Laguna Blanca (RNLB), Depto. San Pedro, Paraguay allowed the first modern sustained, multi-method inventory of Paraguayan reptiles and amphibians to be performed at a single site. Despite the small size of the reserve (804 ha), a total of 57 reptiles (12 of national conservation concern) and 32 amphibians (one of national conservation concern) were collected during five years of random sampling, qualifying RNLB as the most biodiverse reserve for reptiles and amphibians in the country. Six species occurring at RNLB have been found at no other Paraguayan locality. Legal protection for this private reserve expired in January 2015 and the conservation implications of the inventory results are discussed. It is proposed that the long term legal protection of the reserve be considered a national conservation priority and that the diversity of the herpetofauna be recognized with the designation of RNLB as Paraguay’s first Important Area for the Conservation of Amphibians and Reptiles.

Herpetofaunal Diversity and Seasonality from a Remnant Coastal Chenier Forest in Southwestern Louisiana

Cheniers are ancient beach ridges in southwestern Louisiana that are often characterized by coastal forest surrounded by marshland. Coastal chenier forests (CCFs) are considered an imperiled habitat in Louisiana because many forest remnants are considerably impacted due to human activities and recent hurricanes. Because little is known about the herpetofaunal community of CCFs, I initiated a seasonal herpetofaunal diversity and abundance study on a privately-owned, remnant CCF in eastern Cameron Parish, Louisiana. Utilizing coverboards and drift fence arrays with pitfall and funnel traps, I documented 12 species (4 anuran, 4 snake, 3 lizard, and 1 turtle) comprising CCF obligate and facultative species, as well as one marsh transient species. Species-accumulation curves indicate the sample was representative of the small herpetofaunal community. Three amphibian (Incilius nebulifer [Gulf Coast Toad], Lithobates sphenocephalus utricularius [Coastal Plains Leopard Frog], and Gastrophryne carolinensis [Eastern Narrow-mouthed Toad]) and 2 reptile (Scincella lateralis [Little Brown Skink] and Thamnophis p. proximus [Orangestriped Ribbonsnake]) species comprised 94% of the captures. Diversity was highest during the spring, with 3 months (March–May) of sampling detecting 92% of the total diversity observed. Sampling during single months only yielded 42–75% of the diversity. Amphibian abundance varied by month (highest June to September) and with the presence of rain, whereas reptile abundance only varied by month (highest in March). Funnel traps were more effective and quantified diversity better than pitfall traps or coverboards. The herpetofaunal diversity at the site was low and comprised of mostly generalist species; regional specimen records also exhibit a modest herpetofaunal community. This data will provide baseline information to determine the impacts of future hurricanes on the herpetofaunal community, analyze recolonization dynamics following hurricanes, and make comparisons to other CCF remnants in the region. I also provide recommendations for improving herpetofauna sampling methodology in coastal settings.

Exotic Fish in Exotic Plantations: A Multi-Scale Approach to Understand Amphibian Occurrence in the Mediterranean Region.

Globally, amphibian populations are threatened by a diverse range of factors including habitat destruction and alteration. Forestry practices have been linked with low diversity and abundance of amphibians. The effect of exotic Eucalyptus spp. plantations on amphibian communities has been studied in a number of biodiversity hotspots, but little is known of its impact in the Mediterranean region. Here, we identify the environmental factors influencing the presence of six species of amphibians (the Caudata Pleurodeles waltl, Salamandra salamandra, Lissotriton boscai, Triturus marmoratus and the anurans Pelobates cultripes and Hyla arborea/meridionalis) occupying 88 ponds. The study was conducted in a Mediterranean landscape dominated by eucalypt plantations alternated with traditional use (agricultural, montados and native forest) at three different scales: local (pond), intermediate (400 metres radius buffer) and broad (1000 metres radius buffer). Using the Akaike Information Criterion for small samples (AICc), we selected the top-ranked models for estimating the probability of occurrence of each species at each spatial scale separately and across all three spatial scales, using a combination of covariates from the different magnitudes. Models with a combination of covariates at the different spatial scales had a stronger support than those at individual scales. The presence of predatory fish in a pond had a strong effect on Caudata presence. Permanent ponds were selected by Hyla arborea/meridionalis over temporary ponds. Species occurrence was not increased by a higher density of streams, but the density of ponds impacted negatively on Lissotriton boscai. The proximity of ponds occupied by their conspecifics had a positive effect on the occurrence of Lissotriton boscai and Pleurodeles waltl. Eucalypt plantations had a negative effect on the occurrence of the newt Lissotriton boscai and anurans Hyla arborea/meridionalis, but had a positive effect on the presence of Salamandra salamandra, while no effect on any of the other species was detected. In conclusion, eucalypts had limited effects on the amphibian community at the intermediate and broad scales, but predatory fish had a major impact when considering all the scales combined. The over-riding importance of introduced fish as a negative impact suggests that forest managers should prevent new fish introductions and eradicate fish from already-occupied ponds whenever possible.

Seasonal differences in extinction and colonization drive occupancy dynamics of an imperilled amphibian.

A detailed understanding of the population dynamics of many amphibian species is lacking despite concerns about declining amphibian biodiversity and abundance. This paper explores temporal patterns of occupancy and underlying extinction and colonization dynamics in a regionally imperiled amphibian species, the Northern leopard frog (Lithobates pipiens) in Alberta. Our study contributes to elucidating regional occupancy dynamics at northern latitudes, where climate extremes likely have a profound effect on seasonal occupancy. The primary advantage of our study is its wide geographic scale (60,000 km2) and the use of repeat visual surveys each spring and summer from 2009–2013. We find that occupancy varied more dramatically between seasons than years, with low spring and higher summer occupancy. Between spring and summer, colonization was high and extinction low; inversely, colonization was low and extinction high over the winter. The dynamics of extinction and colonization are complex, making conservation management challenging. Our results reveal that Northern leopard frog occupancy was constant over the last five years and thus there is no evidence of decline or recovery within our study area. Changes to equilibrium occupancy are most sensitive to increasing colonization in the spring or declining extinction in the summer. Therefore, conservation and management efforts should target actions that are likely to increase spring colonization; this could be achieved through translocations or improving the quality or access to breeding habitat. Because summer occupancy is already high, it may be difficult to improve further. Nevertheless, summer extinction could be reduced by predator control, increasing water quality or hydroperiod of wetlands, or increasing the quality or quantity of summer habitat.

Amphibian assemblages in dry forests: Multi-scale variables explain variations in species richness

Pond-breeding amphibians depend on several habitats and scales throughout their complex life cycle. For pond-breeding amphibians inhabiting seasonal dry forests, landscape is composed of a set of scarce and ephemeral isolated ponds surrounded by a contrasting matrix. The Chaco ecoregion is one of the most extensive dry seasonal forests in South America. In the last four decades, agricultural expansion and transformation from subsistence livestock farming to commercial livestock production have triggered dramatic deforestation processes all across the region, changing landscape composition and configuration. We postulate that richness of pond-breeding amphibians in the Chaco dry forest is negatively associated with pond hydroperiod and isolation, and terrestrial matrix degradation. Pond attributes and landscape configuration and composition were used to fit a statistical model to predict amphibian species abundance and richness in Arid Chaco ponds. Our results show that amphibian abundance and species richness in Chaco ponds is related to local and landscape predictors. Isolated and ephemeral ponds located in degraded shrublands showed low species richness values in Chaco dry forests. These results suggest that present-day land-use changes in the Chaco will have important effects on amphibians assemblages from the region, because such changes imply not only the loss of native vegetation but also a reduction of rural people devoted to extensive livestock production, where the artificial ponds used for watering livestock are also used as breeding sites by Chaco amphibians.