Current Herpetology

The cane toad, Rhinella marina, is invasive on several islands in Japan, including Ishigaki Island which lacks native bufonid species. Cane toads possess toxins in the aquatic and terrestrial life stages, and thus pose a risk to native predators, especially predators that have evolved in the absence of bufonids. We tested tadpoles of three anuran species native to Ishigaki Island (Fejervarya sakishimensis, Microhyla kuramotoi, Zhangixalus owstoni) for responses to cane toad hatchlings as potential prey. All three species showed high propensity to consume toad hatchlings. However, the species differed in sensitivity to hatchling toxins: consumption of toad hatchlings was always fatal to M. kuramotoi and Z. owstoni, whereas toxic effects on F. sakishimensis were variable (approximately 40% mortality) independent of tadpole size, developmental stage or the number of hatchlings consumed. Our results are the first to highlight the potential for toxic impacts of invasive cane toads on native anurans in Japan.

Japan has a high diversity of amphibians; however, there are concerns that native species may become extinct due to habitat degradation and invasive species. Raccoons, which prefer wetland habitats, have caused population declines in amphibians, even those with short breeding periods. We evaluated the hypothesis that raccoons appear in wetlands and predation events increase according to the timing of amphibian breeding. In particular, we evaluated differences in the presence of raccoons in wetlands depending on the breeding status of various frog species, accounting for spatiotemporal autocorrelation. From May to July 2022, January to July 2023, and January to February 2024, we monitored animal and frog calling levels using camera traps at 28 sites in Aina Satoyama Park, Hyogo Prefecture. We constructed a generalized linear mixed model with the number of raccoon appearance events and average estimated staying time as objective variables and presence or absence of breeding frogs of each species on the day and previous day, number of egg masses, and month as explanatory variables, using a poisson distribution and tweedie distribution accounting for spatiotemporal autocorrelation. The both best models based on Akaike's information criterion values included the breeding of Rana japonica on the day, breeding of Zhangixalus schlegelii on the previous day, egg masses of R. japonica, and month. Our results suggest that raccoons form an association between frog calls or breeding days and prey resources.

We determined the complete mitochondrial genome sequence of the White-lipped Tree Frog, Polypedates leucomystax, in Okinawa, Japan, from a single individual. The mitochondrial genome encoded 13 protein-coding genes, two rRNAs, 22 tRNAs, and two control regions (D-loops). When compared using full-length mitochondrial genome sequences, our mitochondrial genome is most similar to that of P. leucomystax from Thailand (94.5%). From the phylogenetic analysis of partial mitochondrial genome sequences, P. leucomystax was divided into three subgroups: western (Myanmar), central (Malaysia and Thailand), and central/eastern (Indonesia, Philippines, and Japan). The mitochondrial genome sequences from the Okinawa and Thailand frogs were representative sequences of central/eastern and central subgroups, respectively. In spite of the high similarity between the Okinawa and Thailand frogs' mitochondrial genome sequences, we found a difference in length and the sequence in the second D-loop. In this region, we found a repetitive sequence region, which was composed of an 86-bp sequence with 13- and 14-bp spacer sequences. The repetitive sequence regions were different in length, copy number, the combination of the 86-bp, and the spacer sequences among eight individuals of P. leucomystax in Okinawa, Japan.

Spawning activity of the Japanese red-bellied newt, Cynops pyrrhogaster, was surveyed in Minami-ohsawa, Hachioji-shi, Tokyo, using artificial egg strips. The number, size, and mortality of the deposited eggs were monitored daily from April to July in 2017. Spawning activity was observed mainly over three months from April to June, and a total of 5,339 eggs were successfully detected using artificial egg strips, which was estimated to be approximately 40% of the total number of eggs deposited in the study population. Time-series data were analyzed using state-space modeling to estimate the impact of water temperature on spawning parameters owing to the presence of plausible temporal autocorrelation. The survey quantitatively showed seasonal changes in spawning activity and demonstrated a significant effect of water temperature as females laid more eggs on warmer days. The average daily mean egg size was 2.19 mm (SD=0.05, N=86), and average daily egg mortality was 0.169 (SD=0.148, N=84), with clear seasonal trends: a convex trend for egg size and a concave trend for egg mortality. We did not detect any significant effects of water temperature on egg size or mortality. Currently, there are no data on the factors affecting seasonal changes in egg size and mortality in this species. Newt eggs are difficult to find in natural ponds, but the present study demonstrated that newt surveying using artificial egg strips is an effective way to monitor newt spawning activity.

Several recent studies have highlighted that climate change is a major driver of biodiversity loss. In particular, amphibians, including the genus Philautus (small rhacophorid frogs), are seriously vulnerable due to their permeable skin and biphasic life cycle. This study used ecological niche modeling to predict the current and future distributions of three common Philautus species from Sumatra (P. larutensis, P. polymorphus, and P. thamyridion) under climate scenarios SSP2-4.5 and SSP5-8.5 for 2050 and 2090. The model results aligned well with field records of the examined species, showing that P. larutensis occupies a large area from north to south along the Bukit Barisan Mountain Range, while P. polymorphus and P. thamyridion are mainly distributed in the mountainous areas of southern Sumatra. Projections under future climate scenarios indicate that the suitable habitats of the three species could decline by 44% to 96%, with shifts toward higher altitudes. Alarmingly, only 8.6% to 12.5% of the suitable habitats of these tree frogs overlap with current protected areas. These findings highlight the urgent need for conservation measures to mitigate the effects of climate change on Philautus species on Sumatra.

A Bornean megophryid, Leptobrachella gracilis ( Günther, 1872 ), the type species of now synonymized genus Leptolalax, proved to contain two different call types that differ in various aspects of advertisement calls including pulse repetition rate and dominant frequency. Genetic analyses of mtDNA and nuDNA of these two types (slow- and fast-call) co-occurring at the type locality, Matang, Sarawak, revealed them to be heterospecific with no evidence of gene exchange. The female holotype of L. gracilis is estimated to belong to the slow-call type based on morphological similarities. We therefore describe the fast-call type as a new species, Leptolalax sarawakensis sp. nov.

Amphibians inhabit both aquatic and terrestrial environments and perform important ecological functions in each ecosystem. However, amphibian densities have been declining in recent years due to habitat degradation and loss, infectious diseases and climate change. In addition, predation by invasive raccoons (Procyon lotor) has recently become a concern globally. In this study, we evaluated impact of invasive raccoon to the Japanese common toad Bufo japonicus, which breeds briefly in early spring, over a five-year period to determine (1) the frequency of predation by raccoons using infra-red triggered camera traps, (2) whether the raccoon frequency differs before and after the breeding season of toads, and (3) the impact of raccoons on toad populations. We obtained clear video evidence of toad predation by raccoons over two years at a breeding site. Although it is necessary to investigate the decline in the toad population using more accurate methods, the maximum number of observed individuals decreased during the survey period. Furthermore, predation events exceeded 10 per breeding site per year. The frequency of raccoon appearances increased when toads began to breed. This suggests that raccoons selectively prey on toads aggregating in small ponds for breeding. The distribution of raccoons is expanding approximately 2.8-fold from 2007 to 2017 in Japan. Thus, there is an urgent need for toad conservation and raccoon control measures.

Climate change is a major factor contributing to the loss of habitat and decline of amphibian populations, posing a threat to biodiversity conservation. Bufonidae species are particularly sensitive to changes in their environment and vulnerable to climate change due to their strong homing instinct and frequent group behavior (mating and migration of juveniles). We identified the major distribution areas and habitat characteristics of two toad species found in Korea, toad, Bufo gargarizans, and water toad, B. stejnegeri, based on observation points and species distribution modeling. Distributional changes due to climate change were predicted. The toads used low altitudinal ranges and agricultural land, whereas the water toads used forested areas. The average model test area under the curve (AUC) value for toads was 0.695± 0.007, while the average test AUC value for water toads was 0.883±0.015. Toad distribution was most affected by temperature and altitude. By the 2100s, the number of occupied grid cells for toads and water toads is predicted to decrease by 99.57% and 100.00%, respectively, compared to the present number of occurred grid cells under the SSP 5-8.5 scenario. These critical data inform conservation measures for amphibians affected by global climate change.

This study investigates arboreal behavior in the scincid lizard, Plestiodon japonicus, focusing on populations in mainland Japan. Previous research suggested that the population on the Danjo Islands uses trees for basking, but whether this behavior is widespread or a specific adaptation to the islands remained unclear. To explore this, camera traps were set up in a forest in Kumamoto Prefecture from June 2022 to October 2023, recording lizard behaviors. Climbing behaviors were observed at two sites, with five climbing events recorded over 9,570 camera-days. The lizards moved smoothly along tree trunks, with speeds comparable to arboreal lizards like Anolis. The current findings may provide a reliable record of a specific aspect of the species' broader habitat use.

Sexual size dimorphism (SSD) in body size and head size can vary among species in the lizard genus Sceloporus. We studied the SSD in body and head size of two closely related species, Sceloporus nelsoni from Chihuahua and two populations of S. pyrocephalus, one from Michoacán and the other from Guerrero. Males had larger bodies than females in both species. However, SSD in head size was only found in the two populations of S. pyrocephalus, with males having relatively longer and wider heads than females. Our results suggest that these two species share SSD in body size, but vary in SSD in head size. This species pair might therefore be an interesting system in which to further explore the underlying causes of SSD in body and head size.