Nam-Yong Ra

Habitat Use and Home Range of the Endangered Gold-Spotted Pond Frog (Rana chosenica)

Abstract Because of their complex life styles, amphibians and reptiles living in wetlands require both aquatic and terrestrial buffer zones in their protected conservation areas. Due to steep declines in wild populations, the gold-spotted pond frog (Rana chosenica) is listed as vulnerable by the IUCN. However, lack of data about its movements and use of habitat prevents effective conservation planning. To determine the habitat use and home range of this species, we radio-tracked 44 adult frogs for 37 days between 10 July and 4 Nov. 2007 to observe three different populations in the breeding season, non-breeding season, and late fall. The gold-spotted pond frog was very sedentary; its daily average movement was 9.8 m. Frogs stayed close to breeding ponds (within 6.6 m), and did not leave damp areas surrounding these ponds, except for dormancy migration to terrestrial sites such as dried crop fields. The average distance of dormancy migration of seven frogs from the edge of their breeding ponds was 32.0 m. The average size of an individual’s home range was 713.8 m2 (0.07 ha). The year-round population home range, which accounts for the home ranges of a population of frogs, was determined for two populations to be 8,765.0 m2 (0.88 ha) and 3,700.9 m2 (0.37 ha). Our results showed that to conserve this endangered species, appropriately sized wetlands and extended terrestrial buffer areas surrounding the wetlands (at least 1.33 ha, diameter 130 m) should be protected.

Male Salamanders Hynobius leechii Respond to Water Vibrations via the Mechanosensory Lateral Line System

Abstract To test the hypothesis that male Korean salamanders, Hynobius leechii, respond to water vibrations via the mechanosensory lateral line system, we conducted a series of experiments. First, we examined behavioral responses of males to 0, 0.5, 1.0, and 1.5 Hz water vibrations generated by a model salamander, and we measured the number of times the males (1) oriented their heads toward the vibrating model; (2) approached within a 15-cm–diameter circle centered on the cloaca of the model; and (3) touched the model, as well as (4) the length of time the male stayed within the circle. To determine whether the mechanosensory lateral line system mediated these responses, we measured the same behavioral responses to 1.0 Hz water vibrations (1) both with and without a transparent vibration blocker placed between the model and test males, and (2) after exposing the test males to 0, 0.1, 0.5, and 1.0 mM concentrations of cobalt chloride for 1 h to disrupt the mechanosensory lateral line system. Test males showed significant responses to water vibrations from the model regardless of the vibration frequencies. Males showed significantly lower responses when a vibration blocker was placed and after cobalt chloride treatments. These results indicate that H. leechii males respond to water vibrations via the mechanosensory lateral line system. In addition, we describe aspects of the body undulation of mating males. This is the first clear result in urodeles that the mechanosensory lateral line system plays a role in male-male mating competition.

Reproductive function of the body and tail undulations of hynobius leechii (Amphibia: Hynobiidae): A quantitative approach

Abstract To clarify the reproductive function of vibration signals in Hynobius, which has externally fertilized eggs, we quantitatively analyzed the body and tail undulations of male Korean salamanders (Hynobius leechii) in sixteen mating events. One large and one small male, and one female were used in each mating event. We analyzed behaviors recorded over a total of 3 hrs for each mating event; 2 hrs before and 1 hr after females oviposition. Males touched females using their snouts or body trunk throughout the entire mating periods, but females touched males increasingly more after approximately 1 hr before oviposition. Males conducted body undulations more than 50 times per 10 minutes at a mean frequency of 0.64 Hz. Large males conducted more body undulations than small males, particularly on the tree twig where females attached their egg sacs. Males responded to other males’ body undulation throughout the mating period by orienting their head towards, approaching, and touching the undulating male. Females only responded for about 10–20 min before ovipositing, and most responses were directed to the large males body undulation. Males conducted tail undulations 3.0 times per 10 min at a mean frequency of 1.7 Hz and most tail undulations occurred after one male bit the other male. These results suggest that body undulations function in both male‐female and male‐male interactions, while tail undulations mainly functions in male‐male competition. Also, male H. leechii appear to actively attract females, while females respond to the males only at times close to oviposition.

Habitat Associations of the Endangered Gold-Spotted Pond Frog (Rana chosenica)

We used field surveys and statistical models to investigate habitat associations of the endangered gold-spotted pond frog (Rana chosenica). The characteristics of its habitat are of great importance for effective conservation for this declining species in western South Korea. We evaluated a priori models that incorporated biotic and abiotic variables at the pond and landscape scales. The best-ranked model predicts that gold-spotted pond frogs will be more abundant at sites with fewer introduced American bullfrogs (Rana [= Lithobates] catesbeianus) and greater coverage of shallow, vegetated water. Our study leads us to conclude that limiting the spread and abundance of bullfrogs has the potential to aid conservation of the gold-spotted pond frog in our region.

Population Dynamics of the Long-Tailed Clawed Salamander Larva, Onychodactylus fischeri, and Its Age Structure in Korea

Larvae of the long-tailed clawed salamander, Onychodactylus fischeri, have a relatively long larval period, spending a year or more within the stream where they hatch; therefore, a well-established larval population could be critical for the conservation of adult populations. To study the population dynamics of long-tailed clawed salamander larvae, we surveyed a field population once or twice a month from September, 2005 to June, 2006, and determined the age of larval clawed salamanders collected from three different populations in October, 2004 using skeletochronology. The age of long-tailed clawed salamander larvae ranged from 0 to 3 years. New recruitment of larvae in the population primarily occurred in November, 2005, and mid-March, 2006. Larvae with a snout-vent length of more than 30 mm disappeared from the streams in September, 2005, suggesting that two to three year-old clawed salamander larvae metamorphosed during this period.

Ectoparasites: immature Japanese hard ticks (Ixodes nipponensis; Acari: Ixodidae) on Korean lizards

Although lizards are important hosts for hard ticks (Ixodidae), very few studies have been conducted in South Korea. To determine whether or not hard ticks can infest lizards endemic to South Korea, we examined 77 lizards of four species (Eremias argus, Sincella vandenburghi, Takydromus amurensis, and Takydromus wolteri) that were collected at 22 different sites between April and October 2010. We confirmed that all four lizard species can be infested by Ixodes nipponensis larvae or nymphs. Of the 62 E. argus examined, we found an average of 12.5 larvae on two lizards and an average of one nymph on one lizard. We found seven nymphs on one S. vandenburghi. We found an average of two nymphs on two of the five T. amurensis and an average of one nymph on four of the nine T. wolteri. Ixodes nipponensis larvae and nymphs were found most frequently on the foreleg axillae (87.8%), followed by the forelegs (7.3%), the eyelids (2.4%), and the ears (2.4%) of the lizards. To the best of our knowledge, this is the first report of I. nipponensis infestations of lizards endemic to South Korea.

Herpetofauna and habitat characteristics of 16 lagoons along the eastern coastline of South Korea

We conducted field surveys of amphibians and reptiles over a two-year period in 16 lagoons along the eastern coast - line of South Korea, and determined the habitat characteristics correlated with the number of amphibian and reptilian species and individuals. We documented 11 amphibian species and 8 reptilian species. The dominant amphibian spe- cies was the black-spotted pond frog (Rana nigromaculata), and the dominant reptilian species was the red-eared turtle (Trachemys scripta elegans), an invasive species. Among the 14 habitat characteristics, connectivity to mountainous area significantly affected the number of amphibian and reptilian individuals. Other factors, including emerged plant cover, salinity, pH, the number of birds for amphibians and connectivity to agricultural land, lagoon perimeter length for rep- tiles also influenced the number of species or individuals of them. Our results demonstrate that these lagoons are home to more amphibians and reptiles than has been previously known. To effectively conserve herpetofauna in the lagoon ecosystem, lagoons as well as surrounding wetlands, grasslands, and mountainous areas should be protected.

Detection of infectious fungal diseases of frogs inhabiting in Korea.

In recent years, there has been a rapid decrease in amphibian populations worldwide, and infectious diseases have been associated with this decline. Diseased frogs inhabiting Korea were collected from fields, and the diseases were identified by morphological and molecular analyses. Two fungal diseases-saprolegniasis and chromomyeosis-were detected in the frogs. Saprolegniasis caused by Saprolegnia spp. was found in Rana plancyi chosenica from Gangwon-do and Rana huanrenensis from Chungbuk. Chromomyeosis, which is caused by infection with Cladosporium dadosporioides, was detected in Rana catesbeiana from Busan.

Ovulated female salamander (Hynobius leechii) respond to water currents

To determine whether or not the female Korean salamander, Hynobius leechii , responds to water currents and, if so, whether those responses depend on their reproductive conditions, we evaluated the responses of ovulated and ovipos- ited females to 1-Hz water currents generated by a model salamander with and without the placement of a transpar- ent water current blocker between the model and the test females. The ovulated females responded to water currents by turning their heads toward, approaching, and/or making physical contact with the model. When the water current blocker was in place, the number of salamanders that approached the model was reduced significantly. The approaching and touching responses of ovulated females were greater than those of oviposited females, whereas the other measure- ments evidenced no differences. None of the responses of the oviposited females to water currents was affected by the presence of the blocker. Our results indicate that female H. leechii responds to water currents via a mechanosensory system.