Common Toad Bufo Research Articles

Consistent phenological advancement of Common Toad migration in response to climate change in Flanders, Belgium

Abstract Many species use temperature as a cue to time certain life events. Such phenological events can be particularly sensitive to climate change. In amphibians, seasonal migration events between ponds and winter habitats are crucial to ensure reproduction. Therefore, shifts in phenological events – called phenological shifts – can significantly affect the persistence of amphibian populations, especially when induced by climate change. We used citizen science data collected during the spring migration of the Common Toad (Bufo bufo) from 1981 until 2020 to: (i) estimate the phenological shift, (ii) determine consistency of these changes within the studied region, and (iii) relate its temporal variation with changes in temperature. The results revealed an advancement in the peak migration of 3.1 days per decade. This shift was consistent across all populations in Flanders, indicating a regional effect that is most likely due to climate change. This reasoning is supported by the temperature-based model, which indicates that earlier migration occurs in warmer years. Nonetheless, significant local variations persist in the timing of spring migration. Our results highlight the importance of studying in detail the timing of spring migration and its variability, as it may elucidate mechanisms underlying trends in population decline at both national and international scales.

Trunk climbing among ground-dwelling European amphibians – first observation from Poland

Most European amphibian species are considered land-dwelling, associated with moving along the ground and as poor climbers. However, more recent research indicates that non-arboreal amphibians use nesting boxes and tree hollows in Central and Western Europe. This study describes the first observation of tree climbing by the common toad Bufo bufo (Linnaeus, 1758) and common frog Rana temporaria Linnaeus, 1758 in Poland. While conducting a night survey of newt mortality in the ‘Traszki Ratajskie’ protected area in an urban park in the city of Poznań, Poland, we detected the unexpected use of trees by two species of amphibians. In June 2020, we observed cases of Bufo bufo and Rana temporaria foraging on and using arboreal ambush sites. The toads were found at an average height of 124 cm above the ground, and the frogs at 35 cm, on the tree trunks and branches of two willows (Salix cfr. alba L.) and a dead silver birch specimen (Betula pendula L.). The willows had an extensive multi-stem structure, and exhibited signs of maturity and ageing (hollow-bearing trees with open cavities and crevices). This is the first observation of arboreal behaviour in B. bufo and R. temporaria in Poland. The climbing behaviour and use of tree sites were likely linked to the search for a humid shelter provided by the interior of the ageing trees, as well as to the foraging behaviour that we observed. Trees exhibiting signs of maturity usually have complex structures, and seem particularly important for amphibians during periods of drought, as both a suitable shelter and an area from which to ambush prey. We recommend focusing greater attention on the protection of mature, ageing trees, especially Salix spp. within a terrestrial buffer zone of at least 250 metres from ponds, as these are poorly researched components within amphibian habitats. This type of resource may be essential for long-term amphibian conservation due to site fidelity and the limited number of shelters in human-altered landscapes. The recently adopted EU Nature Restoration Law presents an opportunity to develop good practices in this area, particularly urban tree planting and habitat management.

Interplay of abiotic conditions, density, and body size in shaping demography in a high‐elevation toad population

AbstractIn natural populations, vital rates such as survival and reproduction are influenced by a complex interplay of abiotic conditions (e.g., environment), density dependence, and individual factors (e.g., phenotypic traits). Studies at the extremes of species distributions, particularly high elevations, offer unique insights due to the intensified effects of abiotic stressors, which can amplify both direct and indirect effects on vital rates. In this study, we focus on a high‐elevation population of the common toad (Bufo bufo) located near the upper limit of its elevational range in the Swiss Alps. This setting provides a critical context for examining how extreme abiotic conditions interact with density dependence and individual factors to influence life history traits. Utilizing 28 years of capture–mark–recapture data and individual body size measurements from nearly 2500 toads, we applied in a Bayesian statistical framework a Cormack–Jolly–Seber model for estimating male survival probabilities, and a multistate model for assessing female survival and breeding probabilities, alongside sex‐specific growth curves. Our analysis indicates that survival probabilities are significantly impacted by interactions between abiotic conditions such as the active season length and temperature at emergence from hibernation, density dependence, and individual phenotypic traits such as body size. The breeding patterns of females showed a biennial cycle, with temperature at hibernation emergence influencing the likelihood of skipping breeding events and density affecting the resumption of breeding. These results highlight the role of abiotic conditions and density in shaping physiological and reproductive strategies in a high‐stress ecological niche. Moreover, we uncovered indications of indirect effects, where both abiotic conditions and density potentially affect asymptotic growth and thus survival, mediated through changes in body size. Our findings illustrate the complex dynamics at play in high‐elevation populations and the importance of long‐term, individual‐based data in studying these processes. This study underscores the value of integrating multiple sources of variation to understand population dynamics comprehensively, particularly in understudied, extreme environments where traditional ecological models may not fully capture the nuanced interdependencies of natural systems.

Predation of anurans in southern England by Batracobdella algira, a leech previously unknown in the UK

Leech predation of amphibians is known to occur in Europe. Observation of severe leech infestation affecting a common toad Bufo bufo in southern England in summer 2020, with leeches covering the toad’s eyes, throat and axillae, initiated a collaborative investigation to learn more about the occurrence of such leech predation of anurans in the UK. Soliciting reports from the general public identified leech predation of common toads and common frogs Rana temporaria in Devon, Greater London, Hampshire, the Isle of Wight and Somerset in southern England. Through morphological and/or molecular investigation of samples, Batracobdella algira, a leech species not previously reported in the UK, was identified in the majority of cases. The known native Placobdella costata was also identified, with the observed feeding behaviour on anuran hosts being indistinguishable from that of B. algira. Whether the latter is a previously unrecorded or an introduced species has not yet been established. However, sequence data from multiple gene loci were identical to B. algira found in Tunisia, suggesting it more likely to be a non-native species to the UK. Further work is required to elucidate the potential origin and distribution of B. algira in the UK and whether it has any impact on amphibian populations. Keywords: amphibians, Bufo bufo, Glossiphoniidae, Hirudinea, Rana temporaria

A case of hyphema in the common toad Bufo bufo from eastern England

A case of hyphema in the common toad Bufo bufo from eastern England

No sex-dependent mortality in an amphibian upon infection with the chytrid fungus, Batrachochytrium dendrobatidis.

One of the major factors driving the currently ongoing biodiversity crisis is the anthropogenic spread of infectious diseases. Diseases can have conspicuous consequences, such as mass mortality events, but may also exert covert but similarly severe effects, such as sex ratio distortion via sex-biased mortality. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd) is among the most important threats to amphibian biodiversity. Yet, whether Bd infection can skew sex ratios in amphibians is currently unknown, although such a hidden effect may cause the already dwindling amphibian populations to collapse. To investigate this possibility, we collected common toad (Bufo bufo) tadpoles from a natural habitat in Hungary and continuously treated them until metamorphosis with sterile Bd culture medium (control), or a liquid culture of a Hungarian or a Spanish Bd isolate. Bd prevalence was high in animals that died during the experiment but was almost zero in individuals that survived until the end of the experiment. Both Bd treatments significantly reduced survival after metamorphosis, but we did not observe sex-dependent mortality in either treatment. However, a small number of genotypically female individuals developed male phenotype (testes) in the Spanish Bd isolate treatment. Therefore, future research is needed to ascertain if larval Bd infection can affect sex ratio in common toads through female-to-male sex reversal.

Physiological responses to a changing winter climate in an early spring-breeding amphibian.

Climate change is swiftly altering environmental winter conditions, leading to significant ecological impacts such as phenological shifts in many species. As a result, animals might face physiological mismatches due to longer or earlier activity periods and are at risk of being exposed to late spring freezes. Our study points for the first time to the complex physiological challenges that amphibians face as a result of changing thermal conditions due to winter climate change. We investigated the physiological responses to a period of warmer winter days and sudden spring freeze in the common toad (Bufo bufo) by acclimating them to 4°C or 8°C for 48 h or exposing them to 4°C or -2°C for 6 h, respectively. We assessed the daily energy demands, determined body condition and cold tolerance, explored the molecular responses to freezing through hepatic tissue transcriptome analysis, and measured blood glucose levels. Toads acclimated to higher temperatures showed a higher daily energy expenditure and a reduced cold tolerance suggesting faster depletion of energy stores and the loss of winter acclimation during warmer winters. Blood sugar levels were higher in frozen toads indicating the mobilization of cryoprotective glucose with freezing which was further supported by changed patterns in proteins related to glucose metabolism. Overall, our results emphasize that increased thermal variability incurs physiological costs that may reduce energy reserves and thus affect amphibian health and survival. This might pose a serious threat to breeding adults and may have subsequent effects at the population level.

Occurrence of common frog (Rana temporaria) and common toad (Bufo bufo) adults and metamorphs in agricultural fields in Germany: Potential for exposure to plant protection products.

To characterize the potential for exposure of amphibian terrestrial life stages to plant protection products (PPP), we studied the occurrence and habitat use of adult and metamorph common frogs (Rana temporaria) and common toads (Bufo bufo) in an agricultural landscape in Germany. The four selected study sites were breeding ponds with approximately 80% agricultural land within a 1-km radius. Adults were monitored by radio tracking for two years, and metamorph numbers were assessed for one summer using pitfall traps alongside drift fences. The results demonstrate that adults were rarely present in arable fields at any of the sites (overall 0.5% and 4% of total observations for frogs and toads, respectively). Metamorph captures in arable fields were more variable, ranging from 1.2% to 38.8% (frogs) and from 0.0% to 26.1% (toads) across study sites. Unsurprisingly, most captures in arable fields for both toad and frog metamorphs occurred at the site where the pond was completely surrounded by arable fields. Overall, the presence of adult amphibians in arable fields was limited and, for the metamorphs, occurred primarily when crops were denser and PPP spray interception higher. Diurnal hiding behavior was observed with the highest activity recorded at night, further reducing the risk of dermal exposure from direct PPP overspraying. In addition, it appeared that alternative habitats, such as woody structures or water bodies in the broader surrounding area, were preferred by the animals over the arable areas. The use of buffer zones around water bodies in agricultural areas would be an effective risk mitigation measure to protect terrestrial adults and metamorphs residing there and would reduce spray drift entry into water bodies during PPP application. It is hoped that these results will contribute to the discussion of risk assessment and mitigation options for amphibians. Integr Environ Assess Manag 2024;20:2218-2230. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Limited evidence for genetic differentiation or adaptation in two amphibian species across replicated rural-urban gradients.

Urbanization leads to complex environmental changes and poses multiple challenges to organisms. Amphibians are highly susceptible to the effects of urbanization, with land use conversion, habitat destruction, and degradation ranked as the most significant threats. Consequently, amphibians are declining in urban areas, in both population numbers and abundance, however, the effect of urbanization on population genetic parameters remains unclear. Here, we studied the genomic response to urbanization in two widespread European species, the common toad Bufo bufo (26 localities, 480 individuals), and the smooth newt Lissotriton vulgaris (30 localities, 516 individuals) in three geographic regions: southern and northern Poland and southern Norway. We assessed genome-wide SNP variation using RADseq (ca. 42 and 552 thousand SNPs in toads and newts, respectively) and adaptively relevant major histocompatibility complex (MHC) class I and II genes. The results linked most of the genetic differentiation in both marker types to regional (latitudinal) effects, which also correspond to historical biogeography. Further, we did not find any association between genetic differentiation and level of urbanization at local scales for either species. However, urban smooth newts, but not toads, have lower levels of within-population genome-wide diversity, suggesting higher susceptibility to the negative effects of urbanization. A decreasing level of genetic diversity linked to increasing urbanization was also found for MHC II in smooth newts, while the relationship between MHC class I diversity and urbanization differed between geographic regions. We did not find any effects of urbanization on MHC diversity in the toad populations. Although two genetic environment association analyses of genome-wide data, LFMM and BayPass, revealed numerous (219 in B. bufo and 7040 in L. vulgaris) SNPs statistically associated with urbanization, we found a marked lack of repeatability between geographic regions, suggesting a complex and multifaceted response to natural selection elicited by life in the city.

Using the dead to infer about the living: Amphibian roadkill spatiotemporal dynamics suggest local populations' reduction

Roads represent one of the main sources of wildlife mortality, population decline, and isolation, especially for low-vagility animal groups. It is still not clearly understood how wildlife populations respond to these negative effects over space and time. Most studies on wildlife road mortality do not consider the spatial and temporal components simultaneously, or the imperfect roadkill detection, both of which could lead to inaccurate assumptions and unreliable mitigation actions. In this study, we applied a multi-season occupancy model to a 14-year amphibian mortality dataset collected along 120 km of roads, combined with freely available landscape and remote sensing metrics, to identify the spatiotemporal patterns of amphibian roadkill in a Mediterranean landscape in Southern Portugal. Our models showed an explicit general decrease in amphibian roadkill. The Iberian painted frog (Discoglossus galganoi) experienced roadkill declines over time of ∼70 %, while the spiny common toad (Bufo spinosus) and the fire salamander (Salamandra salamandra) had a loss of nearly 50 %, and the Southern marbled newt (Triturus pygmaeus) had 40 %. Despite the decreasing trend in roadkill, spatial patterns seem to be rather stable from year to year.Multi-season occupancy models, when combined with relevant landscape and remote sensing predictors, as well as long-term monitoring data, can describe dynamic changes in roadkill over space and time. These patterns are valuable tools for understanding roadkill patterns and drivers in Mediterranean landscapes, enabling the differentiation of road sections with varying roadkill over time. Ultimately, this information may contribute to the development of effective conservation measures.

The Effect of Gentamicin on the Motility of Hormonally Induced Spermatozoa of Toad Bufo bufo during Storage at 4°C.

We studied the effect of antibiotic gentamicin at concentrations of 0.05, 0.1, 0.2, 0.4, and 1 mg/ml on the maintenance of sperm motility of the common toad Bufo bufo during cold storage of spermic urine samples at 4°C. Parameters of sperm motility during storage of samples with gentamicin at concentrations of 0.05-0.4 mg/ml did not differ significantly, but were higher (p<0.0001) than in the control (storage without antibiotic). Gentamicin at a concentration of 1 mg/ml had a negative effect on sperm motility. After 2 weeks of storage of toad spermic urine samples with gentamicin, the largest number of sperm was preserved when using antibiotic at a concentration of 0.4 mg/ml.

Contrasting effects of ammonium nitrate on tadpole survival, growth and behavior in two common anuran species

Extensive fertilizer use often leads to an accumulation of chemicals in waterbodies that are in close proximity to agricultural fields. One such commonly used fertilizer, ammonium nitrate, has been shown to negatively affect anuran survival and behavior. We performed experiments on tadpoles of two amphibian species, the Agile frog (Rana dalmatina) and the Common toad (Bufo bufo), to test the effects of different concentrations (0 mg/L, 50 mg/L, 100 mg/L and 200 mg/L) of ammonium nitrate on survival, growth and movement activity. We also examined whether sensitivity to predator cues might be altered in the presence of ammonium nitrate. Finally, we tested for the capacity of the two species to exhibit avoidance behavior. Overall, we found that the Agile frog is more sensitive to ammonium nitrate than the Common toad in terms of survival, growth and movement activity. Sensitivity to predator cues was not affected by the fertilizer for the Agile frog, but was shown to alter the behavior of Common toads, whose movement activity did not decrease in the presence of predator cues. Neither species showed an avoidance behavior. Our results suggest that ammonium nitrate can have significant effects on Agile frog tadpoles through direct toxicological effects on survival and growth, but also through behavioral effects. For Common toads those effects were less obvious, but were nonetheless shown in terms of growth, activity and predator detection.

Greater Glasgow pond amphibian surveys 2022

In 2019, Clyde Amphibian and Reptile Group (CARG) decided to organise a spring 2020 common frogspawn (Rana temporaria) survey of the Greater Glasgow area, Scotland. The COVID-19 lockdown postponed this project until 2022. The 2022 survey area was spread across four council districts: Glasgow City, South Lanarkshire, Renfrewshire and East Renfrewshire. The primary aim of the surveys was to collect records of amphibian breeding throughout the Greater Glasgow Area, with secondary aims of: (1) revisiting the ponds to see if the ponds supported the spawn through to tadpole and froglet stages; (2) assessing the condition of the ponds for amphibians; (3) identifying areas for habitat enhancement work; and (4) collecting data on breeding common toads (Bufo bufo) and newts (Lissotriton, Ichthyosaura and Triturus spp.). A total of 45 volunteers participated in the surveys. Surveys were completed between March and May 2022, with a primary focus between March and April in order to capture frog spawning data. Surveyors were asked to record amphibian population data, and habitat data in order to estimate Habitat Suitability Indices. In total 162 ponds were surveyed, with evidence of breeding common frogs found in 66.1% of ponds with 11,478 frogspawn clumps counted on the first set of surveys. Only 12.2% of ponds were found to contain common toads, and small newts (Lissotriton spp.) were identified in only 7.4% of ponds. In relation to the quality of breeding habitat, 24.5% of ponds were assessed as drying out annually, which significantly reduces the suitability of these ponds for breeding. This figure is predicted to increase with anthropogenic climate change reducing the number of breeding ponds available to amphibians in the absence of intervention. Furthermore, the majority of the ponds surveyed were assessed as offering poor or below average suitability for great crested newts (Triturus cristatus) and nearly half of the ponds surveyed were found to have poor or bad water quality, which can increase stress levels for larval amphibians and may adversely affect mortality levels. However, as the analysis of water quality was subjective, these findings should be treated with caution.

An overview of the Scottish National Adder Survey 2022-24

A study was commissioned by NatureScot to analyse changes in the status of the adder (Vipera berus) and other native reptiles at 16 sites across mainland Scotland, the Isle of Skye and the Isle of Arran over a 30-year period from 1992-93 to 2022-24. In 2022-24, volunteer surveyors revisited sites that were previously surveyed in 1992-93 to identify changes in occupancy. Visual surveys recorded adder, common lizard (Zootoca vivipara), slow-worm (Anguis fragilis), common frog (Rana temporaria), common toad (Bufo bufo), smooth newt (Lissotriton vulgaris), and palmate newt (Lissotriton helveticus). Adders were observed in comparable or even greater numbers at eight sites (seven of the original sites surveyed in 1992-93), but an apparent loss of adders at three of the original sites, and major declines at a previously favourable site on the Scottish Borders are cause for concern. Of the other reptiles, common lizards were the most widespread, recorded at 12 sites; and slow-worms were least often recorded, in low numbers at only four sites, though this could be expected in visual surveys for this cryptic species. This publication reviews the factors most likely to be affecting adders in Scotland, particularly the loss of suitable habitat, the likely historic impact of persecution and the potential effects of disturbance by recreational site users. It highlights the importance of sympathetic habitat management, with a particular focus on maintaining favourable micro-habitats for reptiles.

Body size mediates latitudinal population differences in the response to chytrid fungus infection in two amphibians

Factors behind intraspecific variation in sensitivity to pathogens remain poorly understood. We investigated how geographical origin in two North European amphibians affects tolerance to infection by the chytrid fungus Batrachochytrium dendrobatidis (Bd), a generalist pathogen which has caused amphibian population declines worldwide. We exposed newly metamorphosed individuals of moor frog Rana arvalis and common toad Bufo bufo from two latitudinal regions to two different BdGPL strains. We measured survival and growth as infections may cause sub-lethal effects in fitness components even in the absence of mortality. Infection loads were higher in B. bufo than in R. arvalis, and smaller individuals had generally higher infection loads. B. bufo had high mortality in response to Bd infection, whereas there was little mortality in R. arvalis. Bd-mediated mortality was size-dependent and high-latitude individuals were smaller leading to high mortality in the northern B. bufo. Bd exposure led to sub-lethal effects in terms of reduced growth suggesting that individuals surviving the infection may have reduced fitness mediated by smaller body size. In both host species, the Swedish Bd strain caused stronger sublethal effects than the British strain. We suggest that high-latitude populations can be more vulnerable to chytrids than those from lower latitudes and discuss the possible mechanisms how body size and host geographical origin contribute to the present results.

Аналіз спектру живлення жаби трав’яної (Rana temporaria) та ропухи сірої (Bufo bufo) в антропогенно-трансформованих оселищах Українського Розточчя

As a result of the research, 109 individuals of two amphibian species: the common frog (Rana temporaria) and the common toad (Bufo bufo) were selected. These two species are the most numerous among other species of amphibians within the studied territory, therefore, they can be considered typical species in the anthropogenically transformed habitats of the Ukrainian Roztochchia. During the analysis of the collected material, Ivlev’s selectivity index was used to determine the selective attitude of the studied amphibian species to the number of consumed objects. Comparing data obtained from Barber’s traps and material extracted from the stomachs of amphibians, it was concluded that depending on the habitat type, both the common frog (Rana temporaria) and the common toad (Bufo bufo) show a certain feeding selectivity. The common toad consumes mostly the representatives of Annelida (15%), Arachnida (15%) and Coleoptera (18%), what makes up 48% of all consumed objects in total. The common frog, under the conditions of anthropogenically transformed environment, prefers Mollusca (15%), Myriapoda (20%) and Hemiptera (20%) mostly, what is 55% in total. In half of the stomachs we examined for, both amphibian species, plant residues were found, specifically parts of leaves and branches. Additionally, in individuals of the Bufo bufo species, stones were discovered in the stomach. Most likely, these items ended up there accidentally during the capture of primary food objects. Species of tailless amphibians are highly vulnerable to the negative impact of various anthropogenic factors. Deforestation, water bodies drainage, and global or local environmental pollution can significantly affect diverse ecosystems. This, in turn, may lead to the disappearance of segments of the dietary spectrum for amphibians. Monitoring the trophic interactions of this animal class is crucial, given the importance of amphibians as vital links in food chains. This factor underscores the need for periodic trophic monitoring, as amphibians play a pivotal role in sustaining ecological balance within their vulnerable populations.

Metabolites of Xenorhabdus bacteria are potent candidates for mitigating amphibian chytridiomycosis

Chytridiomycosis, caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), has caused extreme losses in amphibian biodiversity. Finding bacteria that produce metabolites with antifungal properties may turn out to be invaluable in the fight against this devastating disease. The entomopathogenic bacteria, Xenorhabdus szentirmaii and X. budapestensis produce secondary metabolites that are effective against a wide range of fungal plant pathogens. To assess whether they may also be effective against Bd, we extracted cell-free culture media (CFCM) from liquid cultures of X. szentirmaii and X. budapestensis and tested their ability to inhibit Bd growth in vitro. As a second step, using juvenile common toads (Bufo bufo) experimentally infected with Bd we also tested the in vivo antifungal efficacy of X. szentirmaii CFCM diluted to 2 and 10% (v/v), while also assessing possible malign side effects on amphibians. Results of the in vitro experiment documented highly effective growth inhibition by CFCMs of both Xenorhabdus species. The in vivo experiment showed that treatment with CFCM of X. szentirmaii applied at a dilution of 10% resulted in infection intensities reduced by ca. 73% compared to controls and to juvenile toads treated with CFCM applied at a dilution of 2%. At the same time, we detected no negative side effects of treatment with CFCM on toad survival and development. Our results clearly support the idea that metabolites of X. szentirmaii, and perhaps of several other Xenorhabdus species as well, may prove highly useful for the treatment of Bd infected amphibians.

Increasingly cautious sampling, not the black colouration of unpalatable prey, is used by fish in avoidance learning.

The efficiency of aposematic colouration of prey is based on the innate bias or facilitation of avoidance learning of predators. In many toxic bufonids, larvae are uniformly black, which is considered a warning signal. We compared fish predation on normal (black) and 'transient albino' (greyish) common toad Bufo bufo tadpoles that did not differ in toxicity or activity. In a two-stage experiment, each fish was presented with tadpoles of one colour in the first trial and the other colour in a subsequent trial. While tadpoles sampled by fish were typically not ingested, some died from injuries. The attack rate did not differ between tadpole phenotypes nor trials, irrespective of which phenotype was the first exposed to the fish. However, during the second trial, the sampled tadpoles, independent of colouration, were mouthed by fish for shorter periods and tadpole mortality decreased. The duration of mouthing also declined with an increasing number of attacks during subsequent trials. We conclude that in single-species prey populations, black tadpole colouration is not a warning signal as it does not accelerate predator learning about prey unprofitability. Our results indicate that with growing experience, predators sample potentially toxic prey more cautiously. This may explain why natural selection does not eliminate aposematic morphs even if predators continuously sample conspicuous prey.

Environmental constraints affect underground reproduction of the common toad (Bufo bufo)

Abstract The common toad (Bufo bufo) is a widespread species in Europe, with accidental occurrence in caves. This study reports the first case of breeding of B. bufo in a natural cave in the Carpathian Mountains. The breeding activity was observed at the end of May and the beginning of June. We identified pairs of common toads in axillary amplexus, egg strings and tadpoles up to a distance of 97 m inside the cave. We hypothesized that there is an active selection of some cave sites as breeding habitat and that the egg deposition is not randomly distributed inside the cave. In 25 sample points, we recorded ten cave environmental features and we assessed the relationship between egg strings presence and environmental features by performing a bias reduction in binomial-response generalized linear model. The results revealed that the strongest ecological factor determining the selection of breeding areas inside the cave was water flow velocity. The presence of light, although an important environmental feature, was not the most determining factor in breeding site selection, as toads successfully entered in completely dark environments to lay eggs in hydrologically favourable places. This study provides new information about the cave breeding of Bufo bufo and highlights the environmental features determining the common toad’s breeding site selection.

Comparison of Cryoresistance of Testicular and Urinal Spermatozoa of the Toad &lt;i&gt;Bufo bufo&lt;/i&gt; (Amphibia, Anura, Bufonidae) during Slow Freezing

A comparative study of the morphofunctional parameters of testicular (non-activated) and urinal (activated) spermatozoa of the common toad Bufo bufo (L., 1758) before and after cryopreservation was carried out. Cryopreservation was performed by a slow method. Sucrose (10%) and dimethylformamide (12%) were used as cryoprotectants. It was shown that the pool of testicular spermatozoa contains significantly more cells with abnormal morphology both before and after cryopreservation. The osmoticity of the base medium for the cryoprotective solution (Ringer’s solution for amphibians – 230 mOsm or urinal plasma – 45 mOsm) had little effect on the survival of testicular and urinal spermatozoa during cryopreservation. Comparison of the morphological and functional characteristics of spermatozoa before and after freezing-thawing indicates that the cryoresistances of testicular and urinal spermatozoa differ slightly.