Effects of acid precipitation on embryonic mortality of Ambystoma salamanders in the Connecticut Valley of Massachusetts

The phenomenon of increased embryonic mortality of the spotted salamander Ambystoma maculatum concomitant with breeding pond acidification from acid rainfall was investigated in the Connecticut Valley of Massachusetts. The pH and chemistry of rain and pond water were analysed, and embryonic mortality of spotted and Jefferson salamanders A. jeffersonianum was monitored in 1976 and 1977.Rainfall pH, 4·16 and 4·07 in 1976 and 1977, respectively, indicates that acid rain continues to occur in the area. Ambystoma breeding ponds are acidic, due to background and rainfall acidity. The average pH of six ponds dropped from 5·62 in 1976 to 5·10 in 1977. Pond pH decreased up to 0·75 pH units following heavy rainfall. These trends indicate that pond acidification from acid rain is occurring.Despite pond acidity, embryonic mortality of spotted and Jefferson salamanders was low. For spotted salamanders, mortality ranged from 2·1 to 30·2%, with 15 of 17 ponds below 16%. Embryonic mortality of Jefferson salamanders ranged from 12·4 to 40·3%. No significant correlation between pond pH and percent embryonic mortality was found.Estimates based on numbers of breeding females showed Connecticut Valley spotted salamander populations to be larger than in areas where their decline has been correlated with acid rain. The size of present populations, and the embryonic acid tolerance exhibited by spotted and Jefferson salamanders, indicate that acid rain has not affected their populations in the Connecticut Valley of Massachusetts.     

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.     

Using habitat models to determine conservation priorities for pond-breeding amphibians in a privately-owned landscape of northern Idaho, USA

As rural landscapes experience increasing levels of residential development, the persistence of species that rely on them will depend on informed planning and management decisions. An understanding of habitat requirements is essential for setting priorities and developing landscape-level plans for the survival of these species. In many temperate rural landscapes, artificially created ponds may be the only wetlands available for aquatic reproduction by amphibians. The introduction of non-native fish into these ponds reduces survival and prohibits successful reproduction of many native pond-breeding amphibians. We surveyed 105 randomly selected wetlands in a primarily privately-owned, rural landscape in north Idaho, USA, for pond-breeding amphibian larvae in 2004 and 2005. We used an information theoretic multimodel inference and an algorithmic (random forests) approach to model habitat for each species based on local and landscape characteristics. We also used a mail survey to quantify how landowners value fish in their wetlands and their plans for future wetland development and fish stocking. Sixty-seven percent of pond owners reported that fishing in their pond was at least slightly important to them and 36% of owners indicated that they were at least 50% likely to add fish to their ponds in the next 5-10 years. Landscape change predictions for this area indicate that forests will become more open due to thinning; habitat models indicated that this is likely to be detrimental to long-toed salamanders and beneficial to Pacific treefrogs. Habitat models also indicate that Columbia spotted frog breeding sites consist of wetlands on flat ground with high solar insolation and that this species is sensitive to nearby development, indicating that as this landscape becomes further developed, this species may require habitat protection for persistence.     

Long term monitoring of amphibian populations with respect to the effects of acidic deposition

Amphibians breed in a variety of aquatic habitats in the United States. While the tolerance of low pH has been examined for many species of amphibians, those that breed in temporary ponds have been the most studied in terms of acidic precipitation. Some of the latter have been shown to have lethal limits for low pH that are close to or above the pH's found in many breeding ponds. Temporary ponds occur in large numbers in the areas of the country most affected by acidic precipitation. Many of these ponds are susceptible to acidification and reduced reproductive success of sensitive species of salamanders has been observed in acidic ponds. Additional practical and logistical considerations clearly make temporary ponds, and certain salamanders that breed in them, the best candidates for monitoring the long term effects of acidic precipitation on amphibian populations. We recommend a cost efficient monitoring scheme across three categories of acidic temporary ponds (low, medium, and high) that incorporates (a) chemical analyses of pond samples, (b) a census of the annual deposition of egg masses, as well as assessment of embryonic mortality in enclosed and unenclosed egg masses in the ponds, and (c) sampling of larval success. This plan offers the best opportunity for detecting changes in amphibian populations that are correlated with the acidity of precipitation, and would provide desperately needed long term data on the abundance of these amphibians.     

Multi-scale effect of landscape processes and habitat quality on newt abundance: Implications for conservation

Recent studies in population dynamics suggest that landscape processes and habitat quality act at different scales on population abundances, but very few have modelled their simultaneous effects. However, at a time of large declines in natural populations, it is essential to understand such multivariate components. We tested the hypothesis that natural populations of palmate newts (Triturus helveticus) are affected on three scales: breeding patch (pond), habitat complementation (terrestrial cover), and metapopulation structure (density of ponds, surrounding populations). We conducted our survey in 130 ponds from southern France (Larzac) and analysed data with generalized additive models (GAM). Two main novel results emerge from these models: (1) the three landscape scales have significant effects on newt abundance, with more newts in deep, vegetated ponds, devoid of fish and surrounded by wooded areas and inhabited ponds; (2) the quality of the surrounding breeding patches is of primary importance in determining the abundance at core sites in a complex way: high abundances are associated positively with high densities of inhabited ponds, but negatively with the number of surrounding ponds. Deforestation, invasive species and abandonment of ponds all have negative impacts on the persistence of palmate newt populations. Future studies should encompass landscapes at different scales and incorporate the habitat quality in surrounding sites to better understand population dynamics and provide adequate conservation measures.     

Amphibian pond loss as a function of landscape change – A case study over three decades in an agricultural area of northern France

Agricultural reform and infrastructural development are among the major drivers of biodiversity loss and landscape homogenization worldwide. Ponds and other small stagnant water bodies are crucial for maintaining regional biodiversity, yet they are vulnerable to human induced landscape change. We investigated for 199 ponds in the ‘département’ Pas-de-Calais in north-western France if pond persistence (n = 86, 43%) or disappearance (n = 113, 57%) was related to wider changes in the landscape, over the period 1975–2006. Landscape data were obtained from aerial photographs (1963), two ASTER satellite images (2001 and 2003) and observations on the ground (1975 and 2006) and land use around the ponds was described over concentric circles with five different radii in the 100–1000 m range. Overall, pond disappearance was associated with a decrease in grassland and an increase in arable fields around the ponds. We found that the small, man-made cattle ponds, with either natural substrate or concrete drinking troughs, were more often affected than the larger, semi-natural ponds. Since the cattle ponds are regularly used for amphibian reproduction, their massive abandonment therewith weakens the population network and puts the local occurrence of some of the rarer species at risk. Spatial extrapolation of models on pond persistence allowed the identification of areas most at risk of further pond loss. We suggest that local amphibian conservation efforts will be the most effective if the focus is on the marshes and dune areas and on pond preservation in the remaining grasslands.     

Acid precipitation and reproductive success of ambystoma salamanders

The two species of mole salamander that occur in the Ithaca, New York, region (Ambystoma maculatum and A. jeffersonianum) breed in temporary ponds that are formed by accumulation of melted snow and spring rains. Water in many of these pools during the breeding season is acid; pH values as low as 3.5 have been measured. In laboratory experiments A. maculatum tolerated pHs from 6 to 10 and had greatest hatching success at pH 7 to 9. Ambystoma jeffersonianum tolerated pH 4 to 8 and was most successful at pH 5 to 6. Mortality rose abruptly beyond the tolerance limits. The pH optimum shifted upward with increasing temperature for A. jeffersonianum and downward for A. maculatum. Judging from our laboratory studies, the acidity measured in breeding ponds should cause mortality in A. maculatum and permit normal development in A. jeffersonianum. In a 4 yr study of a large, acidic vernal pond, 938 adult A. maculatum produced 486 metamorphosed juveniles (0.52 juvenile/adult), while 686 adult A. jeffersonianum produced 2157 juveniles (3.14 juveniles/adult). Because the effects of acid precipitation on the salamanders' breeding ponds are cumulative from year to year, profound changes in the salamander populations can be anticipated.     

Using multiple metrics to assess the effects of forest succession on population status: A comparative study of two terrestrial salamanders in the US Pacific Northwest

Investigations to determine stable or source-sink animal population dynamics are challenging and often infeasible for most species due to the time and expense of mark-recapture studies and the challenge of life histories attributes that result in low detectability and low recapture probabilities. Often, managers rely solely on occupancy or relative abundance patterns to assess a species’ sensitivity to environmental changes. Greater insight into population-level responses to environmental change can be gained by consideration of a combination of readily obtainable metrics, including occupancy, relative abundance, demographic structure and body condition. We examined how these metrics can improve our understanding of population-level responses to forest disturbance, using datasets for two exemplar species of terrestrial salamanders resident to the Pacific Northwestern USA. We compared population metrics for the Del Norte salamander (Plethodon elongatus) and the Siskiyou Mountains salamander (Plethodon stormi) across the seral continuum represented by four forest age classes: pre-canopy, young, mature, and old-growth. We compared these data with those collected from reference stands in mature (P. stormi) or old-growth (P. elongatus) forest containing robust populations. P. elongatus was twice as common as P. stormi. Both occupancy and salamander counts were lowest at pre-canopy sites for both species. Although there were numerous P. elongatus detections in young forests, higher proportions of these individuals were juveniles and sub-adults when compared to populations in late-seral forests. We found a negative relationship between the proportion of immature animals and total counts at a site, indicating that the high proportion of young animals in young forest stands is likely due to dispersal of young salamanders from nearby source populations and/or low survival of adult animals in young forests. We also found reduced body condition of P. stormi populations in young forests. Our results suggest that there are costs to populations occupying early seral forests, such as skewed age class structure and reduced body condition that are indicative of sink populations. Consideration of population-level metrics beyond occupancy and relative abundance can provide important insights when assessing a species’ sustainability in managed forest landscapes.     

Community-level impacts induced by introduced largemouth bass and bluegill in farm ponds in Japan

Largemouth bass Micropterus salmoides and bluegill Lepomis macrochirus have been introduced into many countries and have become cosmopolitan exotic species. However, only a few studies show their impact on introduced communities. To investigate their impact, we performed natural snapshot experiments in 15 farm ponds in Saitama prefecture, eastern Japan. We selected 10 and 5 small ponds in similar environmental conditions, but with and without exotics, respectively. The numbers of fish, crustaceans, and nymphal odonates were smaller in ponds where exotics were found and some species were considered to be locally extinct in several ponds. On the other hand, the numbers of benthic organisms, i.e. tadpoles, chironomids, chaoborids, and Oligochaeta were more abundant in ponds with exotics. These two groups of organisms were separated clearly on the first axis of DCA, which indicats that this difference was mainly induced by bass predation. This result suggests a trophic cascade in which top-down effects induced by exotics propagated to fish, crustaceans, and nymphal odonates directly and to some benthic organisms indirectly. Therefore, when one is to conserve native organisms, attention should be paid not only to direct negative effects, but also to indirect effects propagating to various trophic levels. Because farm ponds are typical Japanese small lentic systems having rich biodiversities and bass and bluegill have been shown to change farm pond communities widely, conservational treatments including eradication of exotic fish should be conducted immediately.     

The importance of understanding spatial population structure when evaluating the effects of silviculture on spotted salamanders (Ambystoma maculatum)

Current silvicultural practices in the northeastern United States create diverse vegetation patterns and microclimates that provide a mosaic of terrestrial habitats for amphibian species. We inferred patterns of habitat use by the spotted salamander, Ambystoma maculatum, by studying colonization of four newly created breeding pools each surrounded by four different forest treatments: a control, partial cut, clearcut with coarse woody debris (CWD) removed, and clearcut with CWD retained. Created pools were rapidly colonized, indicating that breeding salamanders readily bred in new pools they encountered. This suggests that in our study area pool-specific philopatry and site fidelity may not be high and that particular pools may not define local breeding populations. In the experimental silvicultural treatments, juvenile salamanders preferred the control forest to the clearcuts, whereas adult salamanders showed no significant preferences among the treatments. Although silvicultural practices such as clearcutting may reduce juvenile movement between pools, inter-pool movement by adults that are more tolerant of habitat change may ameliorate this effect in our study area. If juveniles are the primary life-history stage dispersing between local populations (i.e., moving between more isolated groups of pools), however, there is potential for clearcutting to reduce the connectivity between local populations.     

Effects of landscape composition, habitat features, and nest distribution on predation rates of simulated turtle nests

We investigated predation of simulated turtle nests in an effort to understand how land-use patterns and the availability of nesting habitat may affect turtle recruitment in a region where human populations and associated development are increasing. Simulated nests were patterned after those created by painted turtles (Chrysemys picta), a common aquatic turtle in our study area, and distributed in four patterns (clustered and near pond, scattered and near pond, clustered and far from pond, and scattered and far from pond) around 36 ponds. Landscape composition (500-2000 m from pond perimeters) and habitats surrounding pond edges (an area extending 250 m from the shore of each pond) were then compared with rates of predation at each pond. Nest-site characteristics also were compared to the fate of individual nests. Landscape composition and habitats surrounding ponds apparently had little influence on predation rates. Nest distribution and the immediate habitat features associated with each nest did affect vulnerability to predation. Clumped nests were preyed upon at a higher rate than scattered nests, and nests close to ponds (within 50 m) were more vulnerable to predators than those created far (100-150 m) from a pond. Counter to our expectations, proximity to edge habitats (other than the shore of a pond) reduced the probability that a nest would be detected by predators. Also, nests placed near roads and suburban lawns had a reduced likelihood of predation whereas those placed in agricultural areas or disturbed sites had a greater probability of being preyed upon. Our results suggest that predation of simulated turtle nests may be a consequence of their distribution and location relative to the foraging activities of common nest predators, especially raccoons (Procyon lotor). Efforts to enhance recruitment among declining populations of turtles should consider the abundance and distribution of nesting habitat. Providing additional nesting sites away from predator foraging habitats may reduce nest predation and increase the recruitment of hatchlings into a population.     

Three decades of urbanization: Estimating the impact of land-cover change on stream salamander populations

Urbanization has become the dominant form of landscape disturbance in parts of the United States. Small streams in the Piedmont region of the eastern United States support high densities of salamanders and are often the first habitats to be affected by landscape-altering factors such as urbanization. We used US Geological Survey land cover data from 1972 to 2000 and a relation between stream salamanders and land cover, established from recent research, to estimate the impact of contemporary land-cover change on the abundance of stream salamanders near Davidson, North Carolina, a Piedmont locale that has experienced rapid urbanization during this time. Our analysis indicates that southern two-lined salamander (Eurycea cirrigera) populations have decreased from 32% to 44% while northern dusky salamanders (Desmognathus fuscus) have decreased from 21% to 30% over the last three decades. Our results suggest that the widespread conversion of forest to urban land in small catchments has likely resulted in a substantial decline of populations of stream salamanders and could have serious effects on stream ecosystems.     

Habitats of the British amphibians (2): suburban parks and gardens

An investigation was made into the use of park and garden ponds as breeding sites by amphibians in Sussex, England. Of the five common British species, three were widespread in the study area; in order of abundance (of records) these were: Rana temporaria > Triturus vulgaris > Bufo bufo. Although more or less randomly distributed with respect to each other, records of amphibians generally became scarce near the most intensively developed areas of town centres. Neither pond volume, age nor local geology seemed to exert significant effects on species distribution. Aquatic vegetation was also unimportant, but fish did prove to be a relevant factor: toads tended to be absent from ponds not containing fish, whereas newts demonstrated a slight preference for such pools. Neither pH nor ionic score correlated with the distribution of any of the three species individually, but large old ponds of high ionic scores were associated with a greater abundance of toads compared with frogs in situations where the two species occurred together. Surveys indicated that in the study area about 15% of gardens contained ponds and of these at least 50% were used as breeding sites by amphibians.     

Mass mortality of native anuran tadpoles in tropical Australia due to the invasive cane toad (Bufo marinus)

Specific pathways of the ecological impact of invasive species remain poorly known. Although the spread of toxic cane toads (Bufo marinus) through tropical Australia is widely believed to have caused extensive mortality of native reptiles and mammals, effects of toad ingestion on native anurans have been virtually ignored. Our studies on the Adelaide River floodplain show that the most numerous vertebrate victims of toad invasion are native tadpoles that die when they attempt to consume toad eggs. We documented 11 episodes of mass mortality, totalling >1300 tadpoles of 10 species, in five waterbodies within a single wet-season shortly after the toads invaded. A causal link between toad breeding and tadpole mortality is supported by observations that: (1) in at least 9 of the 11 waterbodies involved, toads bred immediately prior to mortality events; (2) water quality was indistinguishable from that of control ponds, and tadpoles placed in that water remained healthy; (3) dead tadpoles showed no sign of disease; and (4) laboratory trials showed rapid, 100% mortality in native tadpoles exposed to freshly-laid toad eggs. Despite these high mortality rates, toad invasion does not appear to threaten the viability of anuran populations because frogs often breed in ponds not used by toads, and because density-dependent growth and survival within tadpole communities mean that additional mortality may not reduce the total effective recruitment of metamorph frogs from a waterbody.     

Landcover predicts isolation in Ambystoma salamanders across region and species

Anthropogenic modification of the landscape can have important consequences for dispersal of terrestrial organisms. If certain landcover types consistently act as barriers to movement, their occurrence could serve as a proxy for population isolation. We tested the fit of a general a priori landcover model on genetically-inferred isolation in ambystomatid salamander species. The landcover model included terms for pond size, geographic isolation, and amount of surrounding agriculture. In all cases, agriculture was associated with increased population isolation, while deciduous forest was almost always associated with decreased isolation. The full model described over 70% of the variation in a genetically-inferred measure of isolation in the system for which it was developed, and 30–45% of variation in novel systems. We suggest that landscape analyses can serve as a proxy for population isolation in ambystomatid salamanders. Our findings suggest that preserving well-forested regions without substantial agriculture will protect salamanders through increased population connectivity. These results have important implications for conservation, as genetic analyses are costly and time-consuming, and decisions to purchase or preserve land must often occur quickly.     

A comparison of constructed and natural habitat for frog conservation in an Australian agricultural landscape

Constructed ponds are an important consideration in the conservation of wetland biota in agricultural landscapes. Twenty-two natural ponds and 22 adjacent constructed ponds (farm dams) were surveyed on the Southern Tablelands of New South Wales to compare patterns of use by frogs and develop frog conservation recommendations. Farm dams supported similar numbers of frog species to natural ponds, although differences in frog assemblage were observed between the pond types. Limnodynastes tasmaniensis and Uperolia laevigata were significantly more likely to occur at farm dams while L. peronii was more likely to occur at natural ponds. Results suggest waterbodies with high levels of emergent vegetation cover that lack fish are likely to support a high number of frog species, regardless of origin (i.e. natural or constructed). However, it is important for landholders to conserve natural waterbodies as these environments appear likely to support frog species that do not use farm dams.     

Distribution, species composition and management implications of seed banks in southern New England coastal plain ponds

Buried seeds that germinate during periods of low water or water level drawdown can play important roles in shaping plant community composition, community dynamics and species richness in ecosystems with fluctuating water levels. Northeastern US coastal plain ponds have fluctuating water levels and contain a characteristic shoreline flora that contains many rare plants. The objectives of this study were to: (1) test whether geographically distant ponds in Cape Cod and Martha’s Vineyard had distinct seed banks, (2) determine if hydrologic status as permanent and ephemeral ponds led to differences in seed banks, and (3) examine seed diversity and seed abundance across gradients of shoreline elevations and sediment characteristics. Viable seeds of 45 plant species were identified from nine ponds. Native species dominated pond-shore seed banks and made up 89-100% of all species. There was high overlap in seed bank composition across hydrological classes and geographic regions. One hydrological class captured 73-76% of total species and one geographical region captured 69-78% of the total species recovered from the entire suite of seed bank samples. Seeds were relatively evenly distributed along the shorelines of ephemeral ponds but seed diversity and abundance were lower at low elevations in permanent ponds. Results suggest that strategies to protect pond shorelines to capture maximum diversity of coastal plain pond plants contained in pond sediment seed banks should be implemented across pond hydrologic classes and across a wide geographic area. Shoreline seed distributions indicate that ground-water withdrawals or climate changes that lower pond water levels in permanent ponds will reduce the diversity and abundance of plants recovered from seed banks by shifting water levels to a shoreline zone of high sediment organic matter where seed densities are lower. This effect will be much less in ephemeral ponds where seed diversity and abundance on pond bottoms was high.     

Ecological characteristics of small farmland ponds: Associations with land use practices at multiple spatial scales

Despite their restricted surface area, small farmland ponds often have a high conservation value because they contribute significantly to regional biodiversity and contain rare or unique species. For this reason, the creation of new ponds has become a widely applied practice in many countries. Information on the effects of land use on farmland ponds is very scarce. Farmland ponds differ from larger ponds, lakes and rivers in many aspects and can therefore be expected to be affected by land use via other mechanisms operating at different spatial scales. We here present a study on 126 ponds distributed over the entire territory of Belgium (surface area: 30.500 km²). We assessed variables related to turbidity state and vegetation complexity and related them to land use variables assessed at several spatial scales ranging from the pond edge up to 32 km² circular areas. According to redundancy analysis, trampling by cattle and percentage cover of nearby crop land were positively associated with turbid state related variables. Conversely, ponds with high coverage by forest in the immediate neighbourhood tended to be more associated with the clear water state. Multiple regression analysis demonstrated a negative effect of trampling and coverage by crop land on vegetation complexity. Effects of crop lands and forest were strongest at the local scale (<200 m radius) which indicates that adverse external influences can most efficiently be mitigated at a small scale. Based on these results we suggest several recommendations for pond construction and conservation.     

Amphibian production in forested landscapes in relation to wetland hydroperiod: A case study of vernal pools and beaver ponds

Many amphibian species are plastic in their selection of breeding sites and use both short- and longer-hydroperiod wetlands. Understanding which wetland types are most important to amphibian production is critical for focusing conservation efforts. We compared reproduction of wood frogs (Rana sylvatica) and spotted salamanders (Ambystoma maculatum) and production of wood frog juveniles between seasonal (vernal pools) and semi-permanent (beaver-created ponds) wetlands in the central Adirondack region of the northeastern United States. In 65 seasonal wetlands and 37 semi-permanent wetlands over 3 years, densities of wood frog egg masses were similar, but seasonal wetlands contained 4× as many spotted salamander egg masses as did semi-permanent wetlands. For wood frogs, survival to metamorphosis and juvenile production were an order of magnitude higher in semi-permanent wetlands. Models of wood frog production linked to the climatic record predicted that, depending on annual variation in rainfall and survival to metamorphosis, semi-permanent wetlands may produce annually 1.2–23× the number of wood frogs that seasonal wetlands produce within the study area. Models incorporating variation in demographic traits throughout the range of wood frogs suggest that higher survival to metamorphosis in beaver ponds and higher clutch densities in vernal pools strongly influence metamorph production on a regional basis. Semi-permanent wetlands make major contributions to amphibian production in our region and may also be an important source of colonists to seasonal wetlands following periods of drought. Protection of wetlands along the landscape-level continuum of hydroperiod therefore may be critical for maintaining and restoring amphibian populations.     

No evidence of general decline in an amphibian community of Southern France

We investigated long term changes in an amphibian community in the Languedoc area of Southern France by comparing results of a survey of 56 ponds made in the early 1970s with results of a survey of the same localities in 2001. Based on the frequency of new occurrences and disappearances of species in the sample ponds, there is no sign of a general decline of amphibians in this area. Most species showed non-significant variation in frequency of occurrence or had increased. “Green frogs” (Rana perezi/ridibunda/kl. grafi) showed clear signs of decline, but this is a local phenomenon rather than a decline at the regional scale. Pelodytes punctatus probably declined also, possibly due to its sensitivity to fish introduction. The species richness in the ponds has also remained stable except in ponds where fish have been introduced. The only adverse impact of human activities that we could detect was thus the introduction of fish, which had a significantly adverse effect on amphibian species richness.