Common Toad Bufo Research Articles

Prey-Catching Behaviour in Mudskippers and Toads: A Comparative Analysis

The invasion of land by a diverse group of fishlike amphibians during the Middle-Late Devonian was a key event in the history of life. It is obvious that the evolutionary transition from an aquatic to a terrestrial habitat was associated with physiological adaptations such as novel feeding strategies that can not be elucidated with fossils alone. Here we show that two extant vertebrate species, an amphibious fish (the Atlantic mudskipper Periophthalmus barbarus L.), and the common toad (Bufo bufo L.), which both feed on earthworms, have evolved the same modes of prey recognition. In double-choice experiments, both the fish and the tetrapod tried to capture a moving black bar in worm configuration; a vertical (anti-worm) stimulus did not elicit such a response. This finding sheds light on events that may have occurred in semi-aquatic habitats over 370 million years ago.

A Survey on the Faunal Diversity of Savar Upazila, Dhaka, Bangladesh

A survey was conducted during January to December 2006 to assess the status of faunal diversity of Savar Upazila, Dhaka, Bangladesh. A total of 30 species of birds, 24 species of winter birds, 7 species of reptiles, 3 species of amphibians, 15 species of mammalians and 32 species of fishes were recorded. Relative abundance of those species were determined. Of the birds, House Sparrow (Passer domesticus) was abundant while Blyth's Kingfisher (Alcedo hercules), Rock Eagle Owl (Bubo bengalensis), Hooded Pitta (Pitta sordida), Black-headed Oriole (Oriolus xanthornus), White-winged Duck (Cairina seululala) and Duck (Anser indicus) were rare. The relative abundance of winter bird could not be assessed because of their migratory habit. Striped keelback (Amphiesma stolata) and Common Smooth Water Snake (Enhydris enhydris) were very common while Black pond turtle (Geoclyms hamiltonii) and Pond tortoise (Melanochelys trijuga) were recorded as endangered. Common Toad (Bufo melanostictus) were abundant but Bull Frog (Rana tigrina) was rare. Asiatic Wild Dog (Cuon alpinus) and House Mouse (Mus musculus) were abundant while Common Otter, Large Indian Civet, Irrawaddy River Dolphin, Indian Hare were rare. Carpu, Silver carp, Tilapia, Nilotica were abundant while, Freshwater Garfish, One stripe spinyeel and Grey Featherback were rare. Landfilling, deforestation, poaching, industrial effluents and current jal were identified as major threats to the faunal diversity of Savar area.

Chytridiomycosis‐mediated expansion of Bufo bufo in a montane area of Central Spain: an indirect effect of the disease

ABSTRACTEmerging infectious diseases (EIDs) may indirectly influence community structure by altering biotic interactions in which affected species participate. This kind of indirect effects has received little attention to date, although recent research suggest they may not be infrequent. Chytridiomycosis is an EID that is affecting amphibian assemblages worldwide. Here we present the first (to our knowledge) field evidence of its indirect effect on assemblage structure through the disruption of a biotic interaction. We have documented an expansion of the common toad (Bufo bufo) after chytridiomycosis nearly extirpated the midwife toad (Alytes obstetricans) in Peñalara Natural Park (Central Spain). Bufo bufo has significantly increased its number of breeding sites. All newly occupied breeding ponds were colonized once the large numbers of large, overwintering A. obstetricans tadpoles they had previously held disappeared. An experiment demonstrated that breeding B. bufo adults strongly avoided laying eggs in water containing A. obstetricans tadpoles, accounting for observed patterns of pond use. A second experiment failed to show any predation by large A. obstetricans tadpoles on B. bufo eggs, but other researchers have documented reductions in condition, growth and survival of B. bufo larvae caused by the presence of A. obstetricans tadpoles. In Peñalara, chytridiomycosis attacks B. bufo too, but its effect on it has been quite less severe than on A. obstetricans. Our findings show how, besides any chytridiomycosis direct effects, interspecific differences in its impact may alter assemblage–influencing biotic interactions and, hence, assemblage structure in indirect ways.

The Identification of the Sex Chromosome and Karyotype of Four Toad Species (Genus Bufo) in Thailand by T-lymphocyte Cell Culture

Our knowledge is the first report on karyotypic study of four toad species (genus Bufo) in Thailand namely; large-eared toad (Bufo macrotis Boulenger 1887), Indochinese dwarf toad (Bufo parvus Boulenger 1887), common Indian toad (Bufo melanostictus Schneider 1799) and river giant toad (Bufo asper Gravenhorst 1829). Blood samples were taken from 5 males and 5 females of each four toad species. After the standard whole blood T-lymphocyte culture in the presence of colchicine, the metaphase spreads were performed on microscopic slides and air-dried. Conventional staining, G-banding and C-banding techniques were applied to stain the chromosomes. The results indicated 2n=22 and fundamental number (NF) 44 in both male and female of four toad species. The autosomes of B. macrotis and B. melanostictus is being as 18 metacentric and 4 submetacentric chromosomes while B. parvus and B. asper is as 16 metacentric and 6 submetacentric chromosomes. G-banding technique showed a B. melanostictus's constriction on short arm of Y chromosome (the largest chromosome) but did not show on X chromosome. C-banding technique demonstrated a dark band constriction on Y chromosome of B. melanostictus, the representative of constitutive heterochromatin. However, there is no dark band constriction on X chromosome. So, we conclude that the sex determination of B. melanostictus is XY system. Although we do not treat B. macrotis, B. parvus and B. asper with G-banding and C-banding technique, we also predict that those three species have the same sex determination as B. melanostictus. We extremely appreciate to public our present research, the first cytogenetic study of B. macrotis and B. asper.

Pond and landscape characteristics — which is more important for common toads (Bufo bufo)? A case study from central Romania

The primary anthropogenic factor causing amphibian declines in Europe is habitat loss and fragmentation. Here we explore the effects of aquatic and landscape habitat variables on the adult counts of the Common Toad (Bufo bufo) in 43 ponds in central Romania surveyed between 2000 and 2005. Principal components analysis (PCA) identified two main factors, with which the adult counts can be related the first related to landscape variables (percentage of forest cover, presence/absence of roads and habitat corridors) and the second, to pond variables, in particular the presence/absence of fish, together accounting for 49% of the total variance. Analysis of variance (ANOVA) showed differences between ponds where toads were present or absent in factor loadings of both principal components, but only the landscape factor was significantly correlated with toad counts. These results highlight the role of landscape composition and configuration in maintaining toad populations in this area, and suggest a negative effect of landscape fragmentation. To efficiently protect amphibians in Romania, appropriate legislation and a close collaboration between landowners, landscape planners and herpetologists are needed.

EFFECTS OF DIAZINON ON LARVAE OF THE ASIAN COMMON TOAD (BUFO MELANOSTICTUS, SCHNEIDER 1799)

Continuous subchronic exposure experiments were conducted to assess the effects of diazinon, an organophosphate pesticide, on the survival, growth and activity of larvae of the Asian common toad Bufo melanostictus. Two larval stages, the gill stage (Gosner stages 21 and 22) and gill-atrophy stage (Gosner stages 24 and 25), were continuously exposed to 4 microg/L, 400 mirog/L, and 10 mg/L of commercial-grade diazinon for 30 d. Treatments and untreated controls were maintained in triplicate with water changed and pesticide concentrations renewed every 3 d. Observations showed that subchronic exposure to 400 microg/L and 10 mg/L diazinon caused a significant dose-dependent increase in mortality compared to the control, regardless of the age at which larvae were exposed. One hundred percent mortality was observed in larvae exposed to 10 mg/L. No clear age-related sensitivity was evident in this study. The lethal concentrations at which 50% of the tadpoles (LC50) died during 30 d of continuous exposure were 6 and 7.5 mg/L for gill stage and gill-atrophy stage larvae, respectively. Diazinon impaired larval growth and activity. Tail abnormalities were apparent in larvae exposed to 400 microg/L and 10 mg/L of diazinon. This investigation provides the first empirical evidence of the negative effects of diazinon on the survival, growth and activity of B. melanostictus. The high degree of diazinon toxicity in this study highlights the need to consider important nontarget groups when recommending safe levels of pesticide application.

Endosulfan acute toxicity in Bufo bufo gills: Ultrastructural changes and nitric oxide synthase localization

Endosulfan is an organochlorine pesticide used in agriculture for a wide range of crops. Endosulfan concentrations of up to 0.7 mg/L can be found in ponds and streams near sprayed agricultural fields. We investigated the short-term toxicity of endosulfan in common toad ( Bufo bufo) tadpoles after 24, 48, and 96 h of exposure. Acute toxicity was evaluated at nominal concentrations ranging from 0.01 to 0.6 mg/L: concentrations that could be found after the application of pesticide. Our results show that 0.43 mg/L of endosulfan caused 50% mortality (LC 50). The effects of a sublethal endosulfan concentration (0.2 mg/L) on gill apparatus morphology were evaluated by scanning and transmission electron microscopy. Immunohistochemical methods were also applied to detect the expression pattern of the inducible isoform of nitric oxide synthase (iNOS) in the gills using the confocal laser scanner microscope. Exposure to 0.2 mg/L of endosulfan caused an apparent increase in mucus production, the occurrence of secretory vesicles and lamellar bodies, a widening of intercellular spaces and additionally there was evidence of an inflammatory response in the gill apparatus. The morphological alterations occurred after 24 h and were more pronounced after 48 and 96 h of exposure. Altered morphology and increased mucus secretion indicate impaired gas exchange and osmoregulation in the gills. In addition, there was an increase of iNOS expression after 24 and 48 h which may reflect hypoxia and inflammation in the gill epithelium. Our results clearly indicate that short-term exposure to a sublethal concentration of endosulfan, near the high end of the environmental range, disrupts gill morphology and function in B. bufo tadpoles.

Immunohistochemical Demonstration of Ranavirus Antigen in the Tissues of Infected Frogs (Rana temporaria) with Systemic Haemorrhagic or Cutaneous Ulcerative Disease

Ranavirus disease emerged as a cause of annually recurring epidemic mortality of common frogs (Rana temporaria) in Britain in the late-1980s. Affected frogs present with a peracute disease characterized by systemic haemorrhage, or with a chronic disease characterized by skin ulceration, but no internal gross lesions. Common toads (Bufo bufo) have also been found with haemorrhagic ranavirus disease. In order to investigate possible differences in the pathogenesis of ranavirus infection for each main disease syndrome, we studied a range of tissues from both naturally and experimentally infected frogs using anti-ranavirus immunohistochemistry. Ranavirus was located in a variety of cells, including fibrocytes, epithelial cells, lymphocytes, hepatocytes and melano-macrophages, but fewer tissues were infected in frogs with the skin ulcerative syndrome than in frogs with systemic haemorrhagic disease. Specifically, and in contrast to frogs with haemorrhagic syndrome, there was no labelling for viral antigen in the splenic lymphocytes, pancreas or gastrointestinal epithelium in frogs with ulcerative syndrome. Intracytoplasmic virus inclusions were seen in the liver, kidney, pancreas and stomach of frogs with systemic haemorrhagic disease, but not in frogs with the ulcerative syndrome. Immunohistochemical labelling of selected tissues from an affected toad demonstrated ranavirus antigen in the skin and viscera. This technique demonstrates that, in comparison to ranavirus ulcerative syndrome, the haemorrhagic form of ranavirus disease is associated with virus infection of a wider range of internal organs and identifies the infection of certain tissues, such as the spleen, which might be important in the pathogenesis of the haemorrhagic disease.

Complete mitochondrial genomes of three neobatrachian anurans: A case study of divergence time estimation using different data and calibration settings

We sequenced the whole mitochondrial (mt) genomes of three neobatrachian species: Japanese tree frog Hyla japonica, Japanese common toad Bufo japonicus, and narrow-mouthed toad Microhyla okinavensis. The gene arrangements of these genomes diverged from that of basal anurans (suborder Archaeobatrachia), but are the same as that of the members of derived frogs (i.e., superfamily Hyloidae and Ranoidae in suborder Neobatrachia), suggesting the one-time occurrence of a gene rearrangement event in an ancestral lineage of derived anurans. Furthermore, several distinct repeat motifs including putative termination-associated sequences (TASs) and conserved sequence blocks (CSBs) were observed in the control regions (CRs) of B. japonicus and H. japonica, while no repeat motifs were found in that of M. okinavensis. Phylogenetic analyses using both nucleotide and amino acid data of mt genes support monophyly of neobatrachians. The estimated divergence time based on amino acid data with multiple reference points suggests that the three living amphibian orders may have originated in the Carboniferous period, and that the divergences of anurans had occurred between the Permian and Tertiary periods. We also checked the influence of the data types and the settings of reference times on divergence time estimation. The resultant divergence times estimated from several datasets and reference time settings suggest that the substitution saturation of nucleotide data may lead to overestimated (i.e., older) branching times, especially for early divergent taxa. We also found a highly accelerated substitution rate in neobatrachian mt genes, and fast substitution possibly resulted in overestimation. To correct this erroneous estimation, it is efficient to apply several reference points among neobatrachians.

Antimicrobial activity of skin secretions isolated from Indian toad, Bufo melanostictus Schneider 1799

AbstractAmphibians like toads have been known to secrete antimicrobial secretions outside their body into their environments, through skin pores and parotid glands. Toad skin-secretions contain four types of compounds namely, biogenic amines, bufadienolides, alkaloids & steroids and peptides & proteins. Bulk of research relating to amphibian antimicrobial secretions has been done on frogs. In toads, such research has only been done in South America, Europe and China. Antimicrobial secretions vary considerably from specie-to-specie and drastically across various biomes. This prompted us to examine and confirm presence of antimicrobial activity (if any) in Indian Common Toad (Bufo melanostictus Schneider 1799) skin secretions since; no such analysis had been previously done on this toad which is found all across the South-east Asia. The antibacterial potency of toad skin secretions was tested against the bacteria, Escherichia coli. After running preliminary antibacterial analysis assays, we found that these cutaneous secretions retrieved from Indian Common Toad possessed potential bactericidal activity. The results that we got confirmed that some unexplored bactericidal components were present in skin secretions of these toads. These conclusions call for further research into biochemistry and molecular characterization of these components.

Antimicrobial activity of skin secretions isolated from Indian toad, Bufo melanostictus Schneider 1799

Amphibians like toads have been known to secrete antimicrobial secretions outside their body into their environments, through skin pores and parotid glands. Toad skin-secretions contain four types of compounds namely, biogenic amines, bufadienolides, alkaloids & steroids and peptides & proteins. Bulk of research relating to amphibian antimicrobial secretions has been done on frogs. In toads, such research has only been done in South America, Europe and China. Antimicrobial secretions vary considerably from specie-to-specie and drastically across various biomes. This prompted us to examine and confirm presence of antimicrobial activity (if any) in Indian Common Toad (Bufo melanostictus Schneider 1799) skin secretions since; no such analysis had been previously done on this toad which is found all across the South-east Asia. The antibacterial potency of toad skin secretions was tested against the bacteria, Escherichia coli. After running preliminary antibacterial analysis assays, we found that these cutaneous secretions retrieved from Indian Common Toad possessed potential bactericidal activity. The results that we got confirmed that some unexplored bactericidal components were present in skin secretions of these toads. These conclusions call for further research into biochemistry and molecular characterization of these components.

Vertebrate phenology at similar latitudes: temperature responses differ between Poland and the United Kingdom

We examined the phenology of 2 amphibians (common frog Rana temporaria, common toad Bufo bufo) and one resident bird species (blackbird Turdus merula) at locations in Poland and in the UK on similar latitudes. The timing of phenology was earlier in the UK than in Poland, presum- ably as a consequence of a warmer maritime environment. This was further confirmed by the earlier frog spawn phenology in the warmer west of the UK than in the east. In the amphibians, the response to temperature was significantly greater in the UK than in Poland, although for the resident bird spe- cies the greater response in the UK did not achieve significance. These results suggest that species are adapted to local conditions. However if such adaptive strategies are not able to evolve rapidly to match rapidly changing climatic conditions, then severe disruption to the least flexible elements in any system may result.

Combined exposure to ambient UVB radiation and nitrite negatively affects survival of amphibian early life stages

Many aquatic species are sensitive to ambient levels of ultraviolet-B radiation (UVB) and chemical fertilizers. However, recent studies indicate that the interaction among multiple stressors acting simultaneously could be contributing to the population declines of some animal species. Therefore, we tested the potential synergistic effects between ambient levels of UVB and a contaminant, sodium nitrite in the larvae of two amphibian species, the common European toad Bufo bufo and the Iberian green frog Rana perezi. We studied R. perezi from both mountain and coastal populations to examine if populations of the same species varied in their response to stressors in different habitats. Both species were sensitive to the two stressors acting alone, but the interaction between the two stressors caused a multiplicative impact on tadpole survival. For B. bufo, the combination of UVB and nitrite was up to seven times more lethal than mortality for each stressor alone. In a coastal wetland, the combination of UVB and nitrite was four times more toxic for R. perezi than the sum of the effect on mortality for each stressor alone. One mg/L of nitrite killed half the population of R. perezi at Gredos Mountains at day 10 in the absence of UVB. In the presence of UVB, 50% of the tadpoles from the same experiment died at day 7. Similar toxic response were found for R. perezi in two highly contrasted environments suggesting this synergistic interaction can be a widespread phenomenon. The interaction of excess chemical fertilizers and manure with ambient UVB radiation could be contributing to the global decline of some amphibian species. We suggest that potential exposure to UVB radiation be accounted for when assessing water quality criteria regarding nitrite pollution.

Evaluating factors affecting amphibian mortality on roads: the case of the Common Toad Bufo bufo, near a breeding place

The Common Toad Bufo bufo is the amphibian with the highest rates of road mortality in many European countries. This elevated incidence of road kills has frequently been associated with migration to breeding sites. In this study, we analysed the mortality of the Common Toad in the road network in Catalonia (NE Spain), and investigated the related causative factors on four roads near a breeding site in the Pyrenees. Results suggest that the high mortality rate is due to a combination of factors: toad abundance, traffic density and quality of water bodies for breeding. On the road with the highest incidence of road kills we investigated whether deaths occurred at specific spots or in a random manner. The road was divided into 500 m sections and each section was classified according to biotic (type of vegetation) and abiotic (presence of streams, roadside topography) variables. Multiple correspondence analysis showed that sections with streams crossing under the road had the highest mortality rate, suggesting that such water bodies flowing into the breeding pond are the toads’ main migratory pathways for hibernation and breeding. As toads use the same migratory routes each year, it is critical to identify areas with a high potential mortality so that efficient measures can be designed to increase wildlife permeability, and thereby reduce habitat fragmentation. This methodology could be applied in other areas with high amphibian mortality.

DC electrical stimulation of the pretectal thalamus and its effects on the feeding behavior of the toad (Bufo bufo)

The feeding motivation of the common European common toad (Bufo bufo) can be quantified by the feeding sequence of arousal-orientation-approach-fixate-snap. Previous work has found that the optic tectum is an important structure responsible for the mediation of feeding behaviors, and combined electrical and visual stimulation of the optic tectum was found to increase the animals feeding behaviors. However, the pretectal thalamus has an inhibitory influence upon the optic tectum and its lesion results in disinhibited feeding behaviors. This suggests that feeding behavior of anurans is also subject to influence from the pretectal thalamus. Previous studies involving the application of DC stimulation to brain tissue has generated slow potential shifts and these shifts have been implicated in the modulation of the neural mechanisms associated with behavior. The current study investigated the application of DC stimulation to the diencephalon surface dorsal to the lateral posterodorsal pretectal thalamic nucleus in Bufo bufo, in order to assess effects on feeding motivation. The application of DC stimulation increased the incidence of avoidance behaviors to a visual prey stimulus while reducing the prey catching behavior component of approach, suggesting that the DC current applied to the pretectum increased the inhibition upon the feeding elements of the optic tectum. This can be explained by the generation of slow potential shifts.

Common toads (Bufo arenarum) learn to anticipate and avoid hypertonic saline solutions.

Toads (Bufo arenarum) were exposed to pairings between immersion in a neutral saline solution (i.e., one that caused no significant variation in fluid balance), followed by immersion in a highly hypertonic saline solution (i.e., one that caused water loss). In Experiment 1, solutions were presented in a Pavlovian conditioning arrangement. A group receiving a single neutral-highly hypertonic pairing per day exhibited a greater conditioned increase in heart rate than groups receiving either the same solutions in an explicitly unpaired fashion, or just the neutral solution. Paired toads also showed a greater ability to compensate for water loss across trials than that of the explicitly unpaired group. Using the same reinforcers and a similar apparatus, Experiment 2 demonstrated that toads learn a one-way avoidance response motivated by immersion in the highly hypertonic solution. Cardiac and avoidance conditioning are elements of an adaptive system for confronting aversive situations involving loss of water balance.

Spatial distribution and seasonal pattern in road mortality of the common toad Bufo bufo in an agricultural landscape of south-western Poland

AbstractAmphibians are the group of animals suffering particularly from the presence of roads and vehicle traffic. The seasonal migration to breeding places undertaken by amphibians in the temperate climate zone is the main reason for their appearance on roads. Between June 2001 and August 2003, 957 common toads Bufo bufo were recorded killed on 48.8 km road network with various traffic volumes (350-10500 cars per 24 h), situated in the agricultural landscape of south-western Poland. The highest mortality was recorded in April (57% of all road-kills). The places with highest recorded mortality varied markedly throughout the year. In spring, many more animals died within the built-up areas, while in summer and autumn their number increased in the open countryside. During the whole study period, 73% of all road-kills were recorded on roads (55% of all controlled) with the lowest traffic volume (350-470 cars per 24 h). The average number of road-kills on roads with the high traffic volume (5700-10500 cars per 24 h) was over 15 times lower than on the roads with low traffic (0-0.17 road-kills per 100 m on roads with high traffic vs 2.59 road-kills per 100 m on roads with low traffic). The number of road-kills on 15 road sections was most closely related to the abundance of local populations of Bufo bufo and to the size of water bodies situated in the road vicinity. The yearly level of local mortality in breeding populations of Bufo bufo due to the vehicle traffic ranged from 2 to 18%.

Herbicide exposure affects the chemical recognition of a non native predator in common toad tadpoles (Bufo bufo)

In amphibians and fishes, evidence is increasing that chemical cues from injured conspecifics can play a role in the chemical labelling and learned recognition of unfamiliar predators. In this laboratory study, we tested the prediction that prior chemical exposure to a non-native predator feeding on conspecific tadpoles will subsequently allow tadpoles of the common toad (Bufo bufo) to recognize the chemical cues specifically released by this starved predator. Furthermore, we investigated the vulnerability of this chemically-mediated process to herbicide contamination. With these aims in view, groups of tadpoles were kept either unexposed or exposed for ten days to chemical cues from Turkish crayfish (Astacus leptodactylus) previously fed on tadpoles, both in uncontaminated water and in the presence of four sublethal concentrations of amitrole (0.01, 0.1, 1 and 10 mg.l−1). We then assessed the effects of the six conditioning treatments on general activity and behavioural response to chemical cues from starved crayfish. Larval treatments did not affect the general activity of the tadpoles. By contrast, the treatments had significant effects on the behavioural response to the test solution prepared form starved crayfish. The only tadpoles to show an antipredator behavioural response to the chemical stimulation from starved crayfish belonged to the groups derived from chemical exposure to tadpole-fed crayfish in uncontaminated water and in contaminated water with the lowest concentration of amitrole (0.01 mg.l−1). Conversely, this chemical stimulation produced no behavioural change in the control group or in the groups derived from exposure to tadpole-fed crayfish in contaminated water containing 0.1, 1 and 10 mg.l−1 of amitrole. This study demonstrates that chemical cues released during the predator’s feeding activity can subsequently be used by common toad tadpoles in the recognition of an unfamiliar predator. In addition, our results show that the presence of sublethal amitrole concentrations can impair this recognition process. Such a pesticide effect might be especially detrimental for amphibian populations threatened by invasive predators.

Linking global warming to amphibian declines through its effects on female body condition and survivorship

There is general consensus that climate change has contributed to the observed decline, and extinction, of many amphibian species throughout the world. However, the mechanisms of its effects remain unclear. A laboratory study in 1980-1981 in which temperate zone amphibians that were prevented from hibernating had decreased growth rates, matured at a smaller size and had increased mortality compared with those that hibernated suggested one possible mechanism. I used data from a field study of common toads (Bufo bufo) in the UK, between 1983 and 2005, to determine whether this also occurs in the field. The results demonstrated two pathways by which global warming may cause amphibian declines. First, there was a clear relationship between a decline in the body condition of female common toads and the occurrence of warmer than average years since 1983. This was paralleled by a decline in their annual survival rates with the relationship between these two declines being highly correlated. Second, there was a significant relationship between the occurrence of mild winters and a reduction in female body size, resulting in fewer eggs being laid annually. Climate warming can, therefore, act on wild temperate zone amphibians by deleteriously affecting their physiology, during and after hibernation, causing increased female mortality rates and decreased fecundity in survivors.

Female polyandry under male harassment: the case of the common toad (Bufo bufo)

AbstractSeveral recent studies have demonstrated the occurrence of multiple paternity in anuran amphibians, implying that it is more common than previously thought. However, an adaptive explanation for polyandry in anurans is still lacking. The common toad Bufo bufo is an explosively breeding species that releases its eggs in strings. The operational sex ratio (OSR) is male biased, causing strong scramble competition among males; females can even drown through harassment during multiple amplexi. We used microsatellite markers to determine patterns of paternity in natural B. bufo populations and experimentally mated individuals (females exposed to either two or six males). Thirty per cent of field‐collected and 22% of experimentally produced egg strings were sired by at least two males; all others were sired by a single father. Multiple paternities arose only from multiple amplexi, and we found no indication of fertilization from non‐amplexing males, for example through free‐swimming sperm. Our results suggest that polyandry in B. bufo is likely to occur most often at high population densities, and under the most male‐biased OSRs. Moreover, polyandry might be interpreted as being the consequence of females spawning when amplexed by a few males, to avoid the risk of drowning by amplexus with multiple males.