Male breeding behaviour and mate acquisition in the Common toad, Bufo bufo

The breeding behaviour of a Common toad ( Bufo bufo ) population was studied at a breeding pond on Portland, Dorset. Major toad movements towards the breeding pond occurred on warm, wet nights when the temperature did not fall below 6°C. Males arrived earlier than females resulting in an initially exaggerated sex ratio which then slowly reduced as the breeding season progressed. No size assortative pairing was found although large males were more successful at mating than small males. Although males demonstrated no ESS (evolutionary stable strategy) in searching for a female between sites within the pond evidence suggesting the existence of one between the pond and an undefined area surrounding it was found.     

斯洛维尼亚池塘中大蟾蜍的交配模式

为了解大蟾蜍( Bufo bufo)的配对成功是否与身体大小有关,在蟾蜍产卵之前,我们在斯洛文尼亚捕捉和测量了2 224只成体样本。在这些捕获的个体中, 1 772只为雄性, 452只为雌性,其中355对处于抱对状态。雌性的体长(从吻端到泄殖腔的距离)一般比雄性稍长。无论雄性还是雌性,抱对者的体长均大于未抱对者。抱对的雄性和雌性的体长具有显著的正相关。我们所发现的大小匹配的交配模式,与从其它普通蟾蜍种群得到的结果一致[动物学报51 (3) : 513 -515 , 2005]。     

Non‐Selective and Time‐Dependent Behavioural Responses of Common Toads (Bufo bufo) to Predator Acoustic Cues

Acoustic predator recognition has rarely been studied in anurans, in spite of the fact that hearing is widespread in these animals and that it has been demonstrated to play an important role in both arthropods and other vertebrates. Using field playback experiments, we tested the hypothesis that adult common toads (Bufo bufo) are capable of recognizing natural vocalizations of a common predator, the Eurasian otter (Lutra lutra), and show antipredator responses. We found that toads exposed to both natural (two types of otter sounds) and synthetic stimuli [white noise (WN) and otter sound‐based amplitude modulated WN] increased time allocated to locomotion and escape behaviour. These responses were correlated with time elapsed from sunset to the onset of testing and were independent from the type of acoustic signal, toad features and other environmental factors monitored. We conclude that B. bufo has not developed a selective recognition of predator vocalizations, suggesting that low‐frequency or seismic sounds associated with predator movements may provide anurans with better cues about an approaching risk. We propose that the time‐dependent response to acoustic stimuli of common toads represents a case of threat‐sensitivity and demonstrates that it can occur even when the response to the threat is not predator specific.     

Egg production in the Common toad, Bufo bufo

The number and size of eggs produced by the Common toad (Bufo bufo) was investigated at a site in southern England. There was a trend within the population as a whole for egg weight, egg number and ovary weight to increase with female size, as defined by body length and body weight. However, with use of partial correlation analysis to remove the effects of female size from the data, some of these trends changed. Thus, for females of the same size, although egg number increased with ovary weight, no significant correlation was found between egg weight and ovary weight whilst egg weight became negatively correlated with egg number. The possible significance of variation in egg weight on tadpole survival and female reproductive success is discussed.     

Phylogeny and Biogeography of Common Toad(Bufo bufo) in Xinjiang,China

The common toad, Bufo bufo(Linnaeus, 1758), is widely distributed in Europe and parts of Africa. Previous studies of the genetic relationships among B. bufo populations have not included Asian populations. Here, we investigated the phylogenetic relationships of B. bufo, including a population from Xinjiang, China, using 722 bp of the mitochondrial cytochrome b sequence and identified six subclades and 85 haplotypes in populations from 22 countries. Phylogenetic analyses and pedigree differentiation revealed that the subclade containing the Xinjiang population has undergone a relatively recent expansion. Combining our results with those of previous studies, we found that the common toad population of Xinjiang, China, belongs to the European-Caucasian lineage and that its closest relatives based on phylogenetic relationships were eastern European populations. Our research contributes to expanding knowledge of the geographic distribution of B. bufo and illuminates the lineage and genetic relationships of the B. bu fo population in Xinjiang, China. Future research should continue to update the geographic distribution of B. bufo and complete a genetic investigation of the full range of this species.     

Interspecific spawning between Common frogs (Rana temporaria) and Common toads (Bufo bufo)

The interaction between Common frogs (Rana temporaria) and Common toads (Bufo bufo) during the breeding season was studied at a small pond on Portland, Dorset. Although the frogs started and finished spawning earlier than the toads there was a period during which interspecific spawning between female toads and male frogs took place. This appears to have resulted from reduced male toad activity caused by the cold breeding season given that spatial, temporal and behavioural species separation did not occur.     

Prey selection by Toads (Bufo bufo L.) in response to configurational stimuli moved in the visual field z,y-coordinates

Summary Recognition of prey-like stimuli by the Common Toad depends on both the shape of the stimulus and its direction of motion. To evoke preycapture the direction of motion must be parallel to the long axis of the stimulus. We show here that the same relation between shape and direction of motion applies to stimuli which moved towards or away from the toad, and that retreating stimuli are more powerful releasers than approaching ones.Supported by the Deutsche Forschungsgemeinschaft Ew 7/6.     

Measuring Energetics and Behaviour Using Accelerometry in Cane Toads Bufo marinus

Cane toads Bufo marinus were introduced to Australia as a control agent but now have a rapidly progressing invasion front and damage new habitats they enter. Predictive models that can give expansion rates as functions of energy supply and feeding ground distribution could help to maximise control efficiency but to date no study has measured rates of field energy expenditure in an amphibian. In the present study we used the accelerometry technique to generate behavioural time budgets and, through the derivation of ODBA (overall dynamic body acceleration), to obtain estimates of energetics in free ranging cane toads. This represents the first time that accelerometers have been used to not only quantify the behaviour of animals but also assign to those behaviours rates of energy expenditure. Firstly, laboratory calibrations between ODBA and metabolic rate were obtained and used to generate a common prediction equation for the subject toads (R² = 0.74). Furthermore, acceleration data recorded during different behaviours was studied to ascertain threshold values for objectively defining behaviour categories. Importantly, while subsequent accelerometer field deployments were relatively short they agreed with previous studies on the proportion of time that cane toads locomote yet suggest that the metabolic rate of cane toads in the wild may sometimes be considerably higher than might be assumed based on data for other species.     

The Association Between Personality Traits,Morphological Traits and Alternative Mating Behaviour in Male Endler's Guppies,Poecilia wingei

Alternative mating behaviour, personality traits and morphological characters are predicted to be correlated. Bolder, larger and more colourful males are expected to preferentially court females, while shy, small and drab‐coloured individuals are predicted to sneak copulations. We used males of Endler's guppy, Poecilia wingei, to test this association over a long temporal period (hence including ontogenetic changes) and under two social environments (male‐biased and female‐biased). We found that personality traits (exploration, boldness, activity) of P. wingei males were highly repeatable across long time spans, but they were not correlated (formed no behavioural syndrome). Male age and social environment had no effect on any personality trait, despite their effects on alternative mating behaviour. Young males with higher activity levels were more likely to attempt sneaking. In older fish, there was an association between orange coloration, courtship and boldness, but this was not observed in young males. Our results suggest that alternative mating behaviour is more flexible than personality traits and is independent of them. Non‐colour‐based morphological traits (gonopodium length, body length, caudal straps length, dorsal fin length) were not correlated with any particular mating behaviour.     

A case of pulmonary cryptococcosis in a free-living toad (Bufo bufo)

Pulmonary cryptococcosis was observed in a free-living adult female common toad (Bufo bufo) that was killed by a vehicle. Both lungs had various eosinophilic, monomorphic, and spherical to elliptical organisms identified as Cryptoccocus spp. The yeasts were demonstrated by Grocott's silver method and the periodic acid-Schiff reaction and the capsule was positive for mucin with a mucicarmine stain. The agent was confirmed by immunohistochemistry, using the monoclonal antibody anti-Cryptococcus neoformans, and by a polymerase chain reaction-based method using a C. neoformans-specific primer. This report, to the best of our knowledge, represents the first case of cryptococcosis in a common toad.     

Loss of genetic diversity and fitness in Common Toad (Bufo bufo) populations isolated by inimical habitat

Measures of genetic diversity (including heterozygosity), survival and developmental homeostasis were found to be significantly lower in small, urban populations of the Common Toad (Bufo bufo) than in larger, rural populations of the same region. The autecology and genetic analysis of this relatively sedentary species suggested that the causal mechanism was genetic drift, arising from barriers to migration created by urban development. The pre-metamorphic survival of larvae cultured in identical conditions increased positively with the mean number of alleles at a locus and the percentage of polymorphic loci. Observed heterozygosity in urban garden and rural populations was correlated inversely with the number of observed physical abnormalities (used as a measure of developmental homeostasis) in the developing tadpoles. Genetic distances between town sites of mean 2.2 km separation were significantly higher than those between rural sites of mean 37 km separation. Genetic data were based on allozyme analysis of 27 loci in 8 urban and 4 rural populations. A subset of these sites (3 urban, 2 rural) were also assessed at 3 minisatellite loci and a positive correlation found between the average number of alleles per locus detected by the two methods. Estimates of Nei's 1972 genetic distance, derived separately from the DNA and protein data, were not, however, correlated. The reduction in genetic diversity and fitness observed in these urban toads provides an example of the effect on population persistence that longer term depletion in numbers and habitat fragmentation can have in the wider environment.     

Allocation of Matter in the Body of Growing Toads,Bufo bufo: Components of ‘Condition’

The condition, CI = [body mass (g)/length (cm)³]-1000, tends to increase in toads growing in the laboratory on a diet of meal-worms. The allocation was therefore studied of ingested food to growth corresponding to maintenance of standard condition (ΔW_S) and to increases in condition, expressing bulky growth. A condition index of 100, typical of toad populations, is chosen to characterize standard growth, higher values expressing bulky growth. The relationship between mass specific standard growth (ΔW_s/W₀) and actual growth in mass (ΔW/W₀) was the same in controls and growth hormone-treated toads and was independent of sex and season. It could be described by the allometric equation ΔW_s/W₀ = 0.28 (ΔW/W₀)^1.36, r = 0.93. The composition of mass representing increases in bulk in excess of a CI = 100 was assessed from allometric relationships established between the indices of the chemical constituents and the overall condition index. The increases in condition were partitioned among the organs and parts of the body from allometric relationships established between indices of organs and body parts and the overall condition index. Treatment with growth hormone enhanced growth in mass and significantly increased the relative proportion of mass allocated to standard growth. However, the effect was not specific to growth hormone, but was an indirect effect of the increased growth rate. Water was the predominant constituent of the growth in bulk, amounting to about 70% of increases in CI. Fat and protein contributed about equally initially, 5–10%, with fat strongly increasing and protein slightly decreasing with increasing condition, fat to approach 20–30% when CI approached 200. Increases in water content largely reflected increases in volume of blood and lymph.     

Variation in Male Calling Behaviour and Relation to Male Mating Success in the Strawberry Poison Frog (Dendrobates pumilio)

Calling behaviour and the characteristics of the males’ call are important for mate attraction, female mate choice and male mating success in anurans. In this study I investigated the variation in calling activity and the variation in one spectral (dominant frequency) and four temporal properties (call rate, call duration, duty cycle and pulse rate) of the advertisement call of strawberry poison frogs, Dendrobates pumilio, in two Costa Rican populations during two study periods. Regarding all call properties, no differences were found between populations or years, but between‐male variation was significantly higher than within‐recording and within‐male variation. Dominant frequency was less variable within and among males than temporal call properties and I classified the former as static and the latter as intermediate properties of the call. No call property seemed to be strongly affected by body length or weight. Moreover, I used behavioural observations to relate male calling behaviour to mating success. Calling activity was more variable between males and accounted for more variability in mating success in multiple regression models than any call property. Some call properties (call rate, dominant frequency and pulse rate) were also related to male mating success in one or two study periods. These call properties are probably important for females during courtship to assess their prospective mate and/or for competitive male–male interactions. Furthermore, I compared call properties and mating success of some males for which data were available for both study periods. Pulse rate was lower in the second than in the first year, suggesting age‐related changes in this call property. Moreover, male D. pumilio increased their relative mating success from the first to the second study year. Together with other studies, the data of this study suggest that, in anurans, endurance rivalry contributes more to variation in male mating success than does female choice based on male characteristics.     

Polymerase chain reaction primers for microsatellite loci in the Common Toad Bufo bufo

The Common Toad Bufo bufo is a wide‐ranging species, with a distribution encompassing much of Europe and Asia. Few molecular studies have been undertaken on this species, and only one polymorphic microsatellite locus has been identified. Therefore, little is known about the genetic variability within and between B. bufo populations. The value of such information is essential for monitoring the species and its environment. This paper reports the characterization of 15 B. bufo microsatellite loci using individuals from a Spanish and UK sample.     

Mating System Variation in Woodhouse's Toad (Bufo woodhousii)

Sexual selection and mating-system variation was studied in two disjunct populations of Woodhouse's toad (Bufo woodhousii) with dissimilar breeding-period durations. In spite of the differences in breeding-period duration, nightly operational sex ratios were roughly equivalent and strongly male biased in both populations, ranging from 0 to 0.5 in the population with a prolonged breeding period, and from 0 to 0.2 in the explosively breeding form. Although operational sex ratios were similar, some males mated with up to three females in the population with an extended breeding period, whereas none of the males mated polygynously in the population with a short breeding season. Two alternative reproductive tactics, satellite and active-searching behavior, were only exhibited by males under high densities in the population with a short breeding period. In the population with an extended breeding period, male mating success was positively related to call rate, but independent of size or number of nights of participation in chorus activity. Although operational sex ratios were equally low, mating was random by size, number of nights of participation in chorus activity, and call rate for males in the explosively breeding population.     

Experimental Exposures of Boreal Toads (Bufo boreas) to a Pathogenic Chytrid Fungus (Batrachochytrium dendrobatidis)

One of the major causes of worldwide amphibian declines is a skin infection caused by a pathogenic chytrid fungus (Batrachochytrium dendrobatidis). This study documents the interactions between this pathogen and a susceptible amphibian host, the boreal toad (Bufo boreas). The amount of time following exposure until death is influenced by the dosage of infectious zoospores, duration of exposure, and body size of the toad. The significant relation between dosage and the number of days survived (dose-response curve) supports the hypothesis that the degree of infection must reach a particular threshold of about 10⁷–10⁸ zoosporangia before death results. Variation in air temperature between 12°C and 23°C had no significant effect on survival time. The infection can be transmitted from infected to healthy animals by contact with water containing zoospores; no physical contact between animals is required. These results are correlated with observations on the population biology of boreal toads in which mortalities associated with B. dendrobatidis have been identified.     

Calling Behaviour Influences Mating Success in Male Painted Reed Frogs,Hyperolius marmoratus

A detailed study was made of the natural calling behaviour of male painted reed frogs in the wild. Comprehensive minute by minute records of the vocal activity of males calling simultaneously in the breeding chorus were generated over a 19-night period using a multi-channel event recorder. With few exceptions, the period over which males called either spanned or extended beyond the time window when females sought mates in the chorus. Males varied little in calling persistence and the majority produced advertisement calls during each minute of the calling period. Aggressive interactions between males curtailed advertisement call production but fights were short-lived, seldom repeated and limited to a small proportion (12.6%) of males. Call rate was independent of body size and varied widely among males active in the chorus at the same time and under the same environmental conditions. The relative call rate ranks of individuals were sustained over time. The call rates of mated males were high in relation to the rates of other males monitored in the chorus at, and prior to, the time of mating. Females usually preferred the higher of two call rate alternatives presented in a range of two-choice phonotaxis experiments.     

Growth response of testis tissue to partial castration in toads, Bufo bufo bufo

The growth response of the remaining intact testis or testis fragments to partial castration was studied as a function of the duration of the postoperative period, the amount of testis mass excised, as well as the functional state of the testes at the time of operation. Excision of about 90% of the testis mass caused a growth response that increased from slight after eight weeks to pronounced after 14 weeks. After 14 weeks the growth response was slight tounilateral excision of 75% of a testie and pronounced to bilateral excision of 75% of each testis. Subtotal castration caused formation of new seminiferous tubules within the remaining testis tissue when the operation was performed early in the annual testis cycle, whereas the growth response late in the cycle was primarily caused by increased spermatogenetic activity within existing tubules. Partial castration stimulated oocyte formation within fragmented testes, but not in a remaining intact testis. Oocyte formation within a testis fragment was independent of the presence of the Bidder's organ.