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Anurans communicate with others using several types of calls such as advertisement, encounter, release, and rain calls. Some treefrog species produce rain calls from their daytime shelters, such as trees and bushes, during both the breeding and non-breeding seasons. However, the function of rain calls is poorly understood. We investigated the potential functions of rain calls by comparing the responses of male Dryophytes japonicus to the playback of advertisement and rain calls. During one minute of playback and three minutes post-playback, the frequencies of orientation and approach of male D. japonicus towards the call-producing speaker did not differ in the rain and advertisement calls. However, the number of individuals, who finally arrived at the speaker among the males, approached towards the speaker, was significantly lower for the rain call compared to the advertisement call during one-minute playback. Our results suggest that both types of calls evoke the attention of conspecific males, but rain calls do not attract conspecific males, unlike advertisement calls. This difference may reflect the distinct functions of rain and advertisement calls.

The introduction of exotic species and the associated impacts are increasing worldwide due to the development and increase in transportation and international trade. As new populations of the non-native Gekko japonicus and G. swinhonis have recently been discovered in South Korea, this study was conducted to investigate the distribution of these species, evaluate the establishment potential of non-native populations and infer their routes of introduction. The study comprised targeted field surveys around the major international ports, generation of ecological niche models (ENMs), based on the known distributions and comparison of the ecological niches of the two species. The results suggest that G. japonicus and G. swinhonis are primarily distributed in the humid subtropical climate (Cfa) and the monsoon-influenced hot-summer humid continental climate (Dwa), respectively. According to the ENMs predicted across South Korea, suitable habitats for G. japonicus were located along the western and southern coasts of the country, whereas those for G. swinhonis were predicted along the western coastal regions and several major cities inland. These distributional patterns may be attributed to adaptations of the two gecko congeners to distinct climatic conditions leading to divergent ecological niches. Considering the known distributions of the two species in South Korea, the most likely routes of introduction are accidental translocations through international trade and the inland populations most likely originated from human-mediated dispersals along the major rivers. This study highlights the need to implement quarantine procedures for international cargo arriving in South Korea. Additional field surveys are further recommended to focus on urban areas adjacent to international ports and major rivers to curtail further introductions of non-native geckos.

Background: To identify and avoid predators, amphibians rely on chemical cues. Onychodactylus koreanus undergo two to three years of the larval stage in mountainous streams, where they encounter various predators. We aimed to identify the potential predators of O. koreanus larvae based on their antipredator responses to predator odors. Additionally, we examined whether the response was innate or can be strengthened by predator olfactory learning. Results: In Experiment 1, O. koreanus larvae exhibited a substantial antipredator response to Chinese minnow (Rhynchocypris oxycephalus) odor but not to Korean freshwater crayfish (Cambaroides similis) odor. In Experiment 2, O. koreanus larvae, who did not previously expose to R. oxycephalus odor, demonstrated a substantial antipredator response to it. Experiment 3 indicated that predator olfactory learning of R. oxycephalus did not enhance the antipredator response of the larvae. Conclusions: Rhynchocypris oxycephalus could prey on O. koreanus larvae, whose antipredator response to R. oxycephalus odor is innate and not enhanced by olfactory learning. Further investigation into the olfactory system of this species may provide insights into the life cycle of O. koreanus, uncovering hidden underground breeding sites and unknown breeding periods.

Determining the genetic diversity and source rookeries of sea turtles collected from feeding grounds can facilitate effective conservation initiatives. To ascertain the genetic composition and source rookery, we examined a partial sequence of the mitochondrial control region (CR, 796 bp) of 40 green turtles (Chelonia mydas) collected from feeding grounds around the Korean Peninsula between 2014 and 2022. We conducted genetic and mixed-stock analyses (MSA) and identified 10 CR haplotypes previously reported in Japanese populations. In the haplotype network, six, three, and one haplotype(s) grouped with the Japan, Indo-Pacific, and Central South Pacific clades, respectively. The primary rookeries of the green turtles were two distantly remote sites, Ogasawara (OGA) and Central Ryukyu Island (CRI), approximately 1,300 km apart from each other. Comparing three parameters (season, maturity, and specific feeding ground), we noted that OGA was mainly associated with summer and the Jeju Sea, whereas CRI was with fall and the East (Japan) Sea ground. The maturity did not show a distinct pattern. Our results indicate that green turtles in the feeding grounds around the Korean Peninsula originate mainly from the Japan MU and have genetic origins in the Japan, Indo-Pacific, and Central South Pacific clades. Our results provide crucial insights into rookeries and MUs, which are the focus of conservation efforts of the Republic of Korea and potential parties to collaborate for green turtle conservation.

Information on the morphological characteristics of a species can assist in understanding its ecological niche and adaptation to the habitat. The Slender racer (Orientocoluber spinalis) is a near-threatened snake species in the Republic of Korea, but its morphology has not been comprehensively identified. Thus, herein, 45 O. spinalis individuals (21 females and 24 males) from four populations in the Republic of Korea were analyzed using five physical parameters and 19 scales to assess their morphological variations. Their mean snout-vent length, tail length, and body mass were 539 mm, 191 mm, and 39.5 g. Unlike previous studies, the Korean O. spinalis showed sexual dimorphism and geographic variation among populations, mainly in the relative head size. Such variations in the head size may be related to prey competition and availability. The results of this study could present indications of the adaptation of O. spinalis to each habitat that could be further verified if additional research on external environments, such as local prey sources and predators, is conducted.

Abstract Conservation assessments are essential for preserving biodiversity. However, many reptile species have not been evaluated owing to data deficiencies. The Slender racer (Orientocoluber spinalis) is threatened in four out of six inhabiting countries. However, despite its apparent rarity and data deficiency, the International Union for Conservation of Nature (IUCN) has classified it as a Least Concern. In this study, we combined field surveys, habitat analysis, and ecological niche models (ENMs) to identify the critical habitat characteristics of O. spinalis, evaluate its distribution status in the Republic of Korea, and register it as a nationally endangered species. Across the country, we found a few small populations on the mainland but large populations on the islands. Orientocoluber spinalis is mainly found in low-altitude ecotone habitats between grasslands and forests. Based on previous genetic and climatic studies, we propose designating it as an endangered species to conserve this species in protected areas such as national parks, and its non-isolated mainland populations can be preserved as source populations.

Verifying habitats, including the foraging and nesting areas for sea turtles, enables an understanding of their spatial ecology and successful planning of their conservation and management strategies. Recently, the observation frequency and bycatch of loggerhead (Caretta caretta) and green (Chelonia mydas) turtles have increased in the northern limit of their distribution range, in the northern part of the East China Sea and East (Japan) Sea. We conducted satellite tracking to investigate the habitat use of seven loggerhead and eight green turtles from June 2016 to August 2022 in this area, where little is known about their spatial ecology. We applied a 50 percent volume contour method to determine their main foraging areas and analyzed 6 environmental variables to characterize their habitats. Loggerhead turtles mainly stayed in and used the East China Sea as a foraging area during the tracking period, while two individuals among them also used the East Sea as a seasonal foraging area. Most green turtles also used the East China Sea as a foraging area, near South Korea and Japan, with one individual among them using the lower area of the East Sea as a seasonal foraging area. Notably, one green turtle traveled to Hainan Island in the South China Sea, a historical nesting area. Our results showed that the two sea turtle species included the East Sea as a seasonal foraging area, possibly owing to the abundance of food sources available, despite its relatively lower sea temperature. Considering that loggerhead and green sea turtles were observed using the northern part of the East China Sea and East Sea more frequently than previously known and that the sea temperature gradually increases due to climate change, conservation and management activities are required for sea turtles in these areas.

Understanding snake prey breadth, within forest ecosystems, may elucidate their ecological role. We determined the prey items of 35 individuals of four snake species (11 through induced regurgitation analysis and 24 through molecular fecal analysis) collected from five mountain forests between May 2016 and October 2018, located within South Korea. Snake prey breadth spanned across six small mammal (4 rodents and 2 shrews) and five amphibian (2 urodeles and 3 anurans) species. Small mammals were more frequently detected as prey items than amphibians, but the proportion between small mammal and amphibian prey varied by different snake species. Two rodent prey species, Mus musculus and Craseomys regulus, made up 68.6% of the total amount of prey consumed (24 of 35 prey items). Elaphe dione and Gloydius intermedius samples contained only small mammal prey remains, whereas Rhabdophis lateralis and G. ussuriensis appeared to predate both small mammals and amphibians. These findings show snakes’ role in controlling small mammal population sizes in mountain forests and highlight the importance of conserving snake biodiversity native to South Korean mountain forests.

Studies using complete mitochondrial genome data have the potential to increase our understanding on gene organisations and evolutionary species relationships. In this study, we compared complete mitochondrial genomes between all 22 squamate species listed in South Korea. In addition, we constructed Maximum Parsimony (MP), Maximum Likelihood (ML) and Bayesian Inference (BI) phylogenetic trees using 13 mitochondrial protein-coding genes. The mitochondrial genes for all six species in the suborder Sauria followed the same organisation as the sequenced Testudines (turtle) outgroup. In contrast, 16 snake species in the suborder Serpentes contained some gene organisational variations. For example, all snake species contained a second control region (CR2), while three species in the family Viperidae had a translocated tRNA-Pro gene region. In addition, the snake species, Elaphe schrenckii, carried a tRNA-Pro pseudogene. We were also able to identify a translocation of a tRNA-Asn gene within the five tRNA (WANCY gene region) gene clusters for two true sea snake species in the subfamily Hydrophiinae. Our BI phylogenetic tree was also well fitted against currently known Korean squamate phylogenetic trees, where each family and genus unit forms monophyletic clades and the suborder Sauria is paraphyletic to the suborder Serpentes. Our results may form the basis for future northeast Asian squamate phylogenetic studies.

Frog virus 3 (FV3) in the genus Ranavirus of the family Iridoviridae causes mass mortality in both anurans and urodeles worldwide; however, the phylogenetic origin of FV3-like ranaviruses is not well established. In Asia, three FV3-like ranaviruses have been reported in farmed populations of amphibians and reptiles. Here, we report the first case of endemic FV3-like ranavirus infections in the Korean clawed salamander Onychodactylus koreanus, caught in wild mountain streams in the Republic of Korea (ROK), through whole-genome sequencing and phylogenetic analysis. Two isolated FV3-like ranaviruses (Onychodactylus koreanus ranavirus, OKRV1 and 2) showed high similarity with the Rana grylio virus (RGV, 91.5%) and Rana nigromaculata ranavirus (RNRV, 92.2%) but relatively low similarity with the soft-shelled turtle iridovirus (STIV, 84.2%) in open reading frame (ORF) comparisons. OKRV1 and 2 formed a monophyletic clade with previously known Asian FV3-like ranaviruses, a sister group of the New World FV3-like ranavirus clade. Our results suggest that OKRV1 and 2 are FV3-like ranaviruses endemic to the ROK, and RGV and RNRV might also be endemic strains in China, unlike previous speculation. Our data have great implications for the study of the phylogeny and spreading routes of FV3-like ranaviruses and suggest the need for additional detection and analysis of FV3-like ranaviruses in wild populations in Asian countries.

Abstract Species distribution models (SDMs) across past, present, and future timelines provide insights into the current distribution of these species and their reaction to climate change. Specifically, if a species is threatened or not well‐known, the information may be critical to understand that species. In this study, we computed SDMs for Orientocoluber spinalis, a monotypic snake genus found in central and northeast Asia, across the past (last interglacial, last glacial maximum, and mid‐Holocene), present, and future (2070s). The goal of the study was to understand the shifts in distribution across time, and the climatic factors primarily affecting the distribution of the species. We found the suitable habitat of O. spinalis to be persistently located in cold‐dry winter and hot summer climatic areas where annual mean temperature, isothermality, and annual mean precipitation were important for suitable habitat conditions. Since the last glacial maximum, the suitable habitat of the species has consistently shifted northward. Despite the increase in suitable habitat, the rapid alterations in weather regimes because of climate change in the near future are likely to greatly threaten the southern populations of O. spinalis, especially in South Korea and China. To cope with such potential future threats, understanding the ecological requirements of the species and developing conservation plans are urgently needed.

We report the rediscovery of the yellow-bellied sea snake (Hydrophis platurus) in South Korea based on four specimens collected in Seogwipo-si, Jeju-do, between June 2017 and November 2018. Detailed morphological characteristics and the phylogenetic positions of the specimens, based on a comparison of partial mitochondrial Cytb gene sequences among congeneric species, are provided and used for species identification.

To conserve national biodiversity, enlisting and detailed morphological description of unrecorded species is critical. Here, we, for the first time in Korea, report and describe detailed morphological characteristics of two juvenile hawksbill turtles, Eretmochelys imbricata, captured from Seongsan-eup, Seogwipo-si, Jeju-do and Geumnam-myeon, Hadong-gun, Gyeongsangnam-do, South Korea on 4 August 2016 and 19 December 2016, respectively. Both specimens had a narrow head, pointed beak, four pairs of costal scutes, and four pairs of poreless inframarginal scutes, which are typical morphological characteristics of E. imbricata. Phylogenetic analysis of mtDNA control region sequences of a specimen confirmed again that the specimens are E. imbricata. With this addition of E. imbricata ( Mae-bu-ri-ba-da-geo-buk in Korean), four species of sea turtles have now been reported from Korean waters.

The slender racer, Orientocoluber spinalis, is a monotypic species found in northeast Asia. We collected 67 O. spinalis samples from the Republic of Korea (hereafter, South Korea) and 7 from China and Mongolia and investigated their genetic diversity and population structure. In South Korea, O. spinalis populations were mainly found on Oeyeondo, Uido, and Udo islands and Woraksan Mountain and showed low genetic diversity in the analysis of concatenated mitochondrial sequences of the cytochrome b (Cytb) and NADH dehydrogenase subunit 4 (ND4) genes. Orientocoluber spinalis populations in South Korea showed low differentiation and likely diverged recently. Orientocoluber spinalis may have colonized the Korean Peninsula from China and Mongolia, but this route is not confirmed due to the lack of samples from the Democratic People’s Republic of Korea and middle eastern China. Considering its extreme rarity, low population density, and low genetic diversity, O. spinalis should be designated an endangered species in South Korea, as it is in Russia, Mongolia, and Kazakhstan.

Knowing the distribution range and habitat characteristics of a species is an essential part of establishing an effective conservation strategy for that species. In this study, we analyzed the habitat characteristics of the endangered Sibynophis chinensis, found only in Jeju Island in South Korea, and predicted its present and future suitable habitats through showing potential distribution areas. Our results showed that S. chinensis was mainly observed on farm lands and in pine forests. Moreover, the habitat environment was more diverse than previously known. The distribution of S. chinensis was highly related with the precipitation of the wettest period. In the future, the suitable habitat of the snake will decrease in the western and central parts (highlands) of the island, whereas it will increase in the eastern part of the island. Climate change in part gives a chance for the species to expand its distribution range. Overlap between the distribution area of S. chinensis and the human activity area is identified as a potential threat that may lead to the decline of the species. These results could increase our understanding on the basic ecology of this species, which provides an important basis for the effective protection of this endangered species in Korea. Keywords: Distribution, Endangered species, Habitat suitability, Sibynophis chinensis

With most sea turtle populations declining, activities to conserve their habitat and nesting grounds and restore their populations are being implemented worldwide. To preserve the Northwestern Pacific populations, the National Marine Biodiversity Institute of Korea has been releasing artificially propagated sea turtles, but whether these individuals join the wild population remains unknown. The present study aimed to determine the movement patterns of artificially propagated juvenile loggerhead (Caretta caretta) and green (Chelonia mydas) turtles fitted with satellite transmitters on their carapaces and released in the waters of Jeju or Yeosu, Republic of Korea, between August 2018 and April 2022. Loggerheads traveled northward to the East Sea, whereas green turtles moved west or southwest. Two 36-month-old and two 48-month-old loggerheads moved toward their potential nursery grounds and toward their feeding grounds, respectively. Three green turtles with a curved carapace length (CCL) of 45 cm) moved toward their inshore foraging areas. The travel paths were closely related to the direction of local sea currents. Our results implied that releasing artificially propagated sea turtles, considering their age and CCL, can positively contribute to the conservation of Northwestern Pacific populations.

To cope with amphibian die-offs caused by ranavirus, it is important to know the underlying ranavirus prevalence in a region. We studied the ranavirus prevalence in tadpoles of two native and one introduced anuran species inhabiting agricultural and surrounding areas at 49 locations across eight provinces of South Korea by applying qPCR. The local ranavirus prevalence and the individual infection rates at infected locations were 32.6% and 16.1%, respectively, for Dryophytes japonicus (Japanese tree frog); 25.6% and 26.1% for Pelophylax nigromaculatus (Black-spotted pond frog); and 30.5% and 50.0% for Lithobates catesbeianus (American bullfrog). The individual infection rate of L. catesbeianus was significantly greater than that of D. japonicus. The individual infection rate of P. nigromaculatus was related to the site-specific precipitation and air temperature. The individual infection rate gradually increased from Gosner development stage 39, and intermittent infection was confirmed in the early and middle developmental stages. Our results show that ranavirus is widespread among wild amphibians living in agricultural areas of South Korea, and mass die-offs by ranavirus could occur at any time.

Differential microhabitat use may be beneficial to achieving fitness in seasonally variable environmental conditions. To explore whether the microhabitat use of the nocturnal Schlegel’s Japanese gecko, Gekko japonicus, varies seasonally and depends on juvenile, male, and female reproductive groups, we investigated five categorical and five quantitative measure variables of microhabitat use in a wild population both in spring and summer. Most geckos were found on white, vertical planes of concrete and plastered brick walls. None of the categorical variables (type of location, substrate, substrate color, light source, and refuge) significantly differed according to season or group, while substrate temperature and irradiance at the location where geckos were observed and the distance from the nearest potential refuge were significantly greater in summer than in spring. The quantitative measure variables did not differ among the reproductive groups. These results suggest that G. japonicus seasonally adjusts its microhabitat use mainly in terms of quantitative measure variables rather than categorical variables.

We report the complete mitochondrial genome of the slender racer (Orientocoluber spinalis), which is widely distributed in Northeast Asia, using a specimen collected from Mt. Worak, South Korea. The mitogenome was 17,196 bp long, consisting of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and 3 noncoding regions. The presented sequence could be useful for evolutionary and phylogenetic studies of Colubridae.

Numerous amphibian species are declining because of habitat loss and fragmentation due to urbanization of landscapes and the construction of roads. This is a mounting threat to species restricted to habitats close to urban areas, such as agricultural wetlands in North East Asia. The Suweon treefrog (Dryophytes suweonensis) falls into the list of species threatened with habitat loss and most populations are under threat of extirpation. Over the last decades, sub-populations have become increasingly disconnected and specifically the density of paved roads has increased around the only site connecting northern and southern Seoul populations. We surveyed this locality in Hojobeol, Siheung, Republic of Korea in 2012, 2015 and 2019 to first confirm the decline in the number of sites where D. suweonensis was present. The second objective was to analyze the habitat characteristics and determine the remaining suitable habitat for D. suweonensis through a species distribution model following the maximum entropy method. Our results show that rice paddy cover and distance from the paved road are the most important factor defining suitable habitat for D. suweonensis. At this locality, uninterrupted rice paddies are a suitable habitat for the species when reaching at least 0.19 km2, with an average distance of 138 ± 93 m2 from the roads. We link the decrease in the number of sites where D. suweonensis is present with the decrease in rice paddy cover, generally replaced by localized infrastructures, greenhouses and habitat fragmentation. Rice paddies should remain connected over a large area for the protection of the remaining populations. In addition, habitat requirements should be integrated in the requisites to designate protected areas.

The Korean crevice salamander, Karsenia koreana, is the only known plethodontid salamander in Asia. In this study, we provide the first report of this salamander’s complete mitochondrial genome. The mitogenome had a length of 16,780 bp and consisted of 13 protein-coding genes, 2 rRNA genes, 22 tRNA genes, and 2 noncoding regions. The presented sequence may be highly useful for future phylogenetic and evolutionary studies of Plethodontidae.

To date, no study has reported detailed morphological characteristics of Korean sea turtles. Due to the lack of such basic information on Korean sea turtles, further related studies have been difficult in South Korea. In this report, we determined the species and the sex of the one sea turtle caught from the Yellow Sea of Korea (Taean-gun, Chungcheongnamdo) on July 17, 2013, and described its detailed morphological characteristics. The sea turtle was identified as a loggerhead sea turtle (Caretta caretta) by the presence of an interprefrontal scale on the head. The turtle had three times longer length between the edge of anal scute to the anus than that between the anus to tip of the tail, and the size of a pair of claws on the flippers were distinctively different, suggesting that the turtle was a male. Finally, the assumption that the sea turtle might be sexually mature is based on its body weight (59.95 kg), the maximum straight length of the carapace (72.5 cm), and the worn serrated parts at the edge of supracaudal scutes. The loggerhead sea turtle described in this study is the first record from the Yellow Sea of Korea.

Marine reptiles are declining globally, and recent climate change may be a contributing factor. The study of sea snakes collected beyond their typical distribution range provides valuable insight on how climate change affects marine reptile populations. Recently, we collected 12 Laticauda semifasciata (11 females, 1 male) from the waters around southern South Korea-an area located outside its typical distribution range (Japan, China including Taiwan, Philippines and Indonesia). We investigated the genetic origin of Korean specimens by analyzing mitochondrial cytochrome b gene (Cytb) sequences. Six individuals shared haplotypes with a group found in Taiwan-southern Ryukyu Islands, while the remaining six individuals shared haplotypes with a group encompassing the entire Ryukyu Archipelago. These results suggest L. semifasciata moved into Korean waters from the Taiwan-Ryukyu region via the Taiwan Warm Current and/or the Kuroshio Current, with extended survival facilitated by ocean warming. We highlight several contributing factors that increase the chances that L. semifasciata establishes new northern populations beyond the original distribution range.

Listing alien species is becoming more important due to the global spread of infectious diseases such as COVID-19, chytrid fungus, and ranavirus. We determined the identity and origin of newly discovered geckos (hereafter, Incheon gecko) near Incheon Port, South Korea, in September 2021, through morphological and genetic studies. The number of interorbitals of the Incheon geckos overlapped only with those of Gekko swinhonis, among four closely allied species. In addition, the cytochrome c oxidase subunit 1 (CO1, 658 bp) sequence of Incheon geckos had a close genetic p-distance (0.00-5.47%) with that of G. swinhonis in China. Furthermore, Incheon geckos shared major mitochondrial cytochrome b (Cytb, 1,140 bp) haplotypes with G. swinhonis samples collected in coastal cities along the Bohai Bay in northeast China, including Huludao, Shedao, Laiyang, and Tianjin, where regular car-ferry routes connect them to Incheon. These results suggest that the geckos, newly discovered in Incheon, South Korea, are G. swinhonis and were recently introduced from China via ocean cargo, showing a clear case of human-mediated introduction of non-native geckos. [ABSTRACT FROM AUTHOR]

This article discusses the different song types of bush warblers. Topics include variation depending on the sex of the receiver, and the difference between short-range or long-range communication.