Although the global population of many native frog species has declined in recent years, alien frog species have spread rapidly worldwide. In order to eradicate alien frogs, characterizing their spawning sites is highly important. In recent years, eastern-Japanese common toads, Bufo japonicus formosus, have caused negative impacts on native ecosystems though predation and poisoning deaths as a domestic alien species. However, their spawning sites preference is little known. Here, to clarify when and what kind of ponds B. j. formosus prefers for spawning, we conducted a field survey on Sado Island which is one of the invaded regions of this species. We recorded their breeding season and analyzed what kind of ponds they use mainly focusing on the pond structure and landscape to obtain basic information for their eradication. Our results clarified that alien B. j. formosus on Sado Island have the same reproductive features as the native population according to the environmental conditions (lunar phase, wind speed, and rainless period), and the ponds they prefer for spawning are in areas with more surrounding forest and less rice paddy area regardless of pond structures. In addition, we identified that B. j. formosus on Sado Island currently have not yet formed large populations. These findings provide useful information for their eradication not only Sado Island but also in areas where B. j. formosus is distributed as an alien species. It is possibile that B. j. formosus on Sado Island can be eradicated completely if extermination activity is started immediately.
To characterize the prey composition of frogs inhabiting the Tottori Sand Dunes, we examined the stomach contents of 141 individuals of five species (Dryophytes japonicus, Rana japonica, Pelophylax nigromaculatus, Fejervarya kawamurai, and Lithobates catesbeianus). Stomach contents were obtained from 86 frogs. A total of 356 individuals of prey were obtained from 50 P. nigromaculatus. Species in the orders Coleoptera and Araneae were frequently observed in the diets of P. nigromaculatus, but the most common prey item was Labidura riparia in the order Dermaptera (Class Hexapoda); its numerical percentage and frequency of occurrence percentage were 26.7% and 74%, respectively. Labidura riparia was also the most common prey item in the diets of the other four frog species, although the sample sizes for the other species were small. These findings suggest that when P. nigromaculatus migrated to new habitats (e.g., coastal habitats in our study), the immigrant frogs may be able to change its diet in response to the change in available prey items in the habitats. The plastic prey consumption in response to variations in prey resources might be an important factor for its survival in new habitats.
Studying the relationships between predators and their prey is generally complex but provides valuable knowledge into the process of evolution. The clay model method is a technique that has been widely used to assess prey-predator interaction. In the study, we used clay models of the Vietnam warty newt (Paramesotriton deloustali) to evaluate its predator pressures in Tam Dao National Park (NP), northern Vietnam. We also employed camera traps to detect specific predators of the newt in nature. Our camera trap results showed that northern treeshrew (Tupaia belangeri), rats (Rattus sp.), and greater coucal (Centropus sinensis) are predators of the newt in Tam Dao NP. For the clay model experiment observed attacks on the head of clay models were triple those expected by chance, indicating that predators perceived the clay model as actual prey items. The proportions on the models predated upon differed in three habitat types: broadleaf evergreen forests, mixed broadleaf evergreen and bamboo forests, and bamboo forests. We also detected that the attacks on the models were mainly made by mammals. Attack rates at nighttime were three times higher than during the daytime.
The aim of this study was to investigate the diet of Rhinella marina by comparing the availability of food in its environment with its actual diet, and verify whether there is a relationship between the size and volume of its prey and the size of the toad and the width of its mouth. A total of 43 toads (95.55%) presented food items in the stomach. In general, R. marina feeds on the most abundant items in the environment with a niche amplitude of B=0.055. Hymenoptera was the most representative prey numerically. On the other hand, Diplopoda was the most representative prey in volume and frequency. Considering the food importance index (Ix), Diplopoda (Ix=0.47) was the most important part of the diet of R. marina. The relationships between the biometric characteristics of R. marina and its prey are significant with a low coefficient of determination. This result demonstrates that larger individuals predate smaller and lower volume prey, such as ants, and on large prey such as Diplopoda. In general, the diet of R. marina is specialized and is composed of arthropods that occur in greater abundance in nature, but mainly of Diplopoda and Hymenoptera, without selectivity regarding the size of the prey.
The Miyako toad, Bufo gargarizans miyakonis, is a subspecies endemic to the Miyako Islands of the Ryukyu Archipelago. The distribution of B. g. miyakonis is curious since no toads are found on other islands in the remaining part of the Ryukyu Archipelago. In this study, we conducted phylogenetic estimation and population genetic analyses using sequence data of the mitochondrial control region to clarify the phylogenetic position of B. g. miyakonis in the B. gargarizans species group and its population history. Results of phylogenetic analyses suggested that B. g. miyakonis was closely related to eastern populations of B. gargarizans and that there is incomplete lineage sorting among these populations. The divergence time between B. g. miyakonis and its closest lineages was estimated to be 0.54–0.75 Ma, the Middle Pleistocene, which was a little younger than the estimated value provided by the previous study. It is probable that the migration of the ancestor of B. g. miyakonis was strongly affected by the Middle Pleistocene glacial cycle. Population genetics analyses suggested that this subspecies experienced a rapid population size expansion, and that there is moderate genetic differentiation of sub-populations. Although the B. g. miyakonis population has a relatively high-level genetic diversity, it is also unique, having a significant number of accumulated mutations following rapid demographic expansion.
The Japanese fire-belly newt, Cynops pyrrhogaster, is a near threatened species that is conservation dependent. Here, we examine feeding habits across the year within a genetically divergent intraspecific lineages of this species (the Central Lineage) to provide information to support future in-situ and ex-situ conservation activities. Stomach contents from newts were collected in a paddy field habitat, Kyoto City, central Honshu, Japan for two consecutive years. Throughout the year, dipteran aquatic larvae were the most important food source both for males and females, although terrestrial invertebrates were also important prey for the newts. During periods of low prey availability shed skin could also be a relatively valuable source of food. Sympatric frogs and newts appear to target different prey and this may facilitate their co-existence. Our study provides new information on suitable prey items for the Central Lineage of C. pyrrhogaster both in its natural habitat and in captivity.
To determine the habitat use and preferences of amphibian species inhabiting Langkawi Archipelago of Malaysia, we surveyed 53 sites from December 2018 to January 2020. Each sampling site had different habitat characteristics and topography. We used principal component analysis to evaluate the habitat assemblage of the 24 amphibian species we encountered. This analysis was done to illustrate the reduced dimensions of the variables via a component plot. The KMO value is 0.68 and Bartlett’s Test of Sphericity is significant (P<0.001), which means PCA successfully interprets the habitat assemblage of amphibians from the Langkawi Archipelago. In this study, these habitats were classified into three major groups. This study shows species that can tolerate more disturbance than others (unforested/urban and forested/rural species) together with their habitat type groupings based on their habitat preference and tolerance towards disturbances. This information is vital to understand how these species use their preferred environment and minimise tourism impacts on these creatures.
Recent molecular analyses cast doubt on the subspecific relationships of Japanese brown frogs Rana tagoi tagoi, R. t. okiensis, and R. t. yakushimensis. Many samples of R. tagoi from three main islands, i.e., Honshu, Shikoku, and Kyushu tend to form a genetic unit with rich variation. On the other hand, R. t. okiensis, R. t. yakushimensis, and some insular samples are clearly isolated from R. t. tagoi and each other. Thus, we propose to treat each subspecies of R. tagoi as full species and describe part of the Goto Islands populations as Rana matsuoi sp. nov. The new species and R. tagoi show a complicated distributional pattern within the Goto Islands but the former is distinguishable from the latter by their smaller male body size, relatively longer limbs, more developed toe webs, nuptial pad formation in breeding male, and advertisement call with repetition of short notes.
Long-term rearing of Cynops pyrrhogaster and Cynops ensicauda popei confirmed that the longevities of the two species were longer than 36 years; C. pyrrhogaster longer than 37 years and C. e. popei longer than 36 years, respectively. The male C. e. popei that was 34 years old or older showed reproductive behavior with a conspecific young female and successfully bred. The paternal relationships between the old male and the six offspring were also genetically proven, indicating that the male C. e. popei retained its fertility at the age of 34 or older. Since physiological longevity and reproductive ability are important parameters for life history studies, our findings are meaningful for the conservation of the species.
The genus Pelophylax has the most controversial taxonomy of any group of western Palearctic frogs. The taxonomic status of the Pelophylax ridibundus sensu lato from Iran is unclear and many populations of this marsh frog have not been examined. Here, we investigate cytogenetic and morphological variation in populations of this species from western and southwestern Iran. The morphometric results revealed that the frogs from these two areas can be largely distinguished in discriminate function analyses. All frogs are diploid and have 2N=26 chromosomes with five large pairs and eight small pairs of chromosomes. These chromosomes are metacentric, submetacentric and subtelocentric. All frogs have three or four pairs of subtelocentric chromosomes. The 6th and 13th pairs of chromosomes are subtelocentric in all western populations, but the position of the third subtelocentric chromosome pair varies. In south-western populations (Bushehr and Deylam regions) the 8th, 9th, and 13th pairs of chromosomes are subtelocentric, but frogs from Bushehr have one more pair of subtelocentric chromosomes (11th). The second pair of large chromosomes in western populations is submetacentric, but in southwestern populations, the second pair of large chromosomes is metacentric. These differences in the type of chromosomes of P. ridibundus, especially in the presence, absence and number of subtelocentric chomosomes, suggest that the taxonomy of Pelophylax in Iran requires further investigation.
The Japanese black salamander, Hynobius nigrescens, is endemic to Japan and breeds in still water. Egg sacs of three colors (white, intermediate, and transparent) have been identified to date. However, the cause of this variation is not well understood. Therefore, we conducted a survey within the Ryohaku Mountains, where genetic differences are assumed to be small, and investigated egg sac color type in 10 spawning ponds. Our results confirmed that the ratio of the intermediate and transparent types increases with altitude. Regarding egg sac color type at each altitude, all egg sacs found above 740 m asl were white, whereas the transparent and intermediate types began to appear from at or above 740 m. As altitude increased, the incidence of the white type decreased and that of the transparent and intermediate types increased. In addition, a redundancy analysis was performed to determine the relationship between egg sac color and the topographical and meteorological conditions and to clarify the results for each pond. The analysis revealed that maximum snow depth was strongly correlated with an increase in the number of egg sacs of intermediate and transparent types.