Ha-Cheol Sung

Variation and Integration of the Simple Mandibular Postcanine Dentition in Two Species of Phocid Seal

Abstract Pinnipeds generally swallow prey whole, and most have simple, homodont, nonoccluding cheek teeth. We investigated whether cheek teeth in seals are more variable and weakly integrated than in terrestrial Carnivora. We measured mandibular length and crown length of mandibular postcanines (PCs) in ringed seals (Pusa hispida; n = 912) from the Canadian Arctic, and harp seals (Pagophilus groenlandicus; n = 636) from Newfoundland and Labrador. PC size was uncorrelated or only weakly correlated with adult mandibular length. PC length and mandibular length were strongly bilaterally symmetrical (r ≥ 0.8 between left and right sides). PC size was moderately variable (coefficients of variation [CVs] ∼ 7–10%), and CV varied with position in the toothrow. Adjacent PCs were correlated more strongly in size (to r > 0.8) than PCs more distant from one another. In summary, PC size in ringed and harp seals was slightly more variable than cheek teeth in complex dentitions of fissipeds, and the 2 seals were similar to fissipeds in strong bilateral symmetry in mandibular and PC size, patterned variation along the toothrow, and correlated size between adjacent PCs.

Food-supplementing parents reduces their sons' song repertoire size

Food-supplemented parents typically produce more offspring, as numerous experiments on vertebrate populations have shown. ‘Propagule’ (egg or neonate) size and parental care may also be affected, with implications concerning the adult quality of offspring, although few experiments have addressed whether food-supplementing one generation affects adult quality in the next. We conducted a food supplementation experiment on song sparrows (Melospiza melodia) and tested whether song repertoire size, a demonstrated indicator of male quality, differed between the adult sons of fed (food-supplemented) and unfed (non-food-supplemented) parents. Counterintuitively, fed parents produced sons with smaller adult song repertoires, who may thus be expected to contribute fewer offspring, and fewer grand-offspring, to the population. Fed and unfed parents invested equally in the total biomass of their clutches and broods, and average nestling condition was comparable, but because fed parents produced more offspring, average egg and nestling sizes were reduced. Fed and unfed parents apportioned care differently within their broods, and we suggest compensatory growth of offspring emerging from light eggs, or egg size itself, may have affected adult repertoire size. Conceivably, the conservation benefits of food-supplementing populations could attenuate over time if fed parents produce offspring of poorer quality than themselves.

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.

Skeletochronological Age Determination and Comparative Demographic Analysis of Two Populations of the Gold-spotted Pond Frog (Rana chosenica)

To obtain demographic information on threatened gold-spotted pond frog (Rana chosenica Okada, 1931) populations, we determined the ages of 45 male and 13 female frogs (20 males and 9 females from Cheongwon and 25 males and 4 females from Tae-an) and compared the age structures and growth patterns of the two populations in 2006. The snout-vent length (SVL) and body weight of female frogs were greater than those of male frogs in both populations. Male frogs` ages ranged 2 to 7 years old and females` ages ranged 3 to 6 years old. In both populations, 4 years old male frogs were the most abundant age-sex class. The age structures of the two populations were significantly different and the growth coefficients of male frogs from the Cheongwon population were greater than those from the Tae-an population. The mean age of males from the Tae-an population was higher than that from the Cheongwon population. However, the SVL and body weights of male frogs were not different between two populations and there was no difference between the two populations in the mean male SVL at any age. The results could increase our understanding of the life-history of this threatened frog and may be useful in conservation planning.

Male hynobius leechii (amphibia: Hynobiidae) discriminate female reproductive states based on chemical cues

Abstract A series of no‐choice olfactory response tests using water pre‐conditioned with females, with intact and surgically removed ventral glands, at various reproductive states were conducted to determine whether male Hynobius leechii discriminates among females in different reproductive states based on chemical cues. Similarly, ventral gland extracts were tested, and ventral glands were examined histologically. Males’ responses to putative odors of females in four (ovulating, ovulated, ovipositing, and oviposited) reproductive states were independently measured by: i) the latency time to initiate male behavioral response, ii) the arrival time at a fixed point of putative odor source, and iii) the staying time close to the odor point source. Male salamanders showed significant olfactory responses to recently ovulated and ovipositing female odors by quickly arriving at odor sources and staying longer at the origin of the source, but the olfactory responses to the earlier staged ovulating females and the later stage of already oviposited females were not different from controls. Olfactory responses of test males to water preconditioned by intact females or females with ventral glands excised were not different. In addition, ventral gland extracts did not induce significant olfactory responses of test males although the lumens of alveoli in ventral glands of oviposited females were smaller than those of ovulated females. These results indicate that male H. leechii recognizes ovulated and ovipositing females based on chemical cues released but not from the ventral glands.

VARIATION AND INDIVIDUALITY IN DISPLAY-FLIGHT CALLS OF MALE PIPING PLOVERS

Abstract In this first study of vocal individuality in the Charadriidae, we describe vocal variation in the endangered Piping Plover (Charadrius melodus). We studied a long-distance advertisement call given by breeding males during aerial displays, because functionally similar vocalizations of scolopacids are known to be individualistic. We analyzed recordings of 10 breeding males on Prince Edward Island, Canada, made in 1998 and 1999. Calls varied substantially among males: variance among males (in one-way ANOVAs) averaged 61% of the total variance across variables, similar to two scolopacid species. Males were distinguishable from one another even on the basis of single calls. However, discrimination ability (classification success) improved substantially when multiple-call averages per male were used; this approach more realistically represents how plovers experience one anothers calls. Calls of two males changed little over days to weeks. In future work, individual identification can be improved by using averages from multiple calls. To improve techniques for application to the Piping Plover, we recommend research on marked individuals of common related species, which share many acoustic homologies.

Age estimation by skeletochronology and advertisement call variation in the black-spotted pond frog (Rana nigromaculata)

Abstract Advertisement calls may contain information about the callers and the calling spot, which can be used during mate selection. The relationships between variations in advertisement call characters and age, snout-vent length (SVL), and water temperature were analyzed for the black-spotted pond frog (Rana nigromaculata). After recording the advertisement calls, we measured the SVL of the callers and the water temperature of the calling spot, then we collected a toe clipping from each of the 25 individuals recorded. The age of each frog was determined using the skeletochronological method. The frogs were two to eight years old and the asymptotic size was 6.3 cm when fitted to the von Bertalanffy growth equation. Age was not linearly correlated with SVL. In the analysis of 743 recorded advertisement calls from 25 individuals, the water temperature caused a decrease in males’ call duration with more pulse groups, each having higher pulse rates, irrespective of age and SVL. Older males produced calls with more pulse groups and shorter pulse-group duration, which led to increasing call durations irrespective of the water temperature. Larger males produced lower dominant frequency, irrespective of the water temperature. Advertisement calls of the black-spotted pond frog provide information about the quality of males and the manner in which females use this information during mate selection. In this study, we provide information on how frequency reflects male size while temporal characters reflect age.

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.

Estimating Detection Probabilities and Site Occupancy Rates of Three Anuran Species Using Call Surveys in Haenam Gun, Korea

We investigated the distribution of three anuran species, Three-striped pond frogs (Rana nigromaculata), Bullfrogs (Rana catesbeiana), and Narrow-mouthed toads (Kaloula borealis), in an administrative district, Haenam Gun, Junnam Province, Korea using volunteer call surveys. Twenty-eight volunteer call surveyors were assigned to each survey plot. Call surveys on whether the species are present or not were conducted for 5 minutes between 30 minutes after sunset and the midnight on rice fields and ponds from 10 April to 28 August in 2005. Depending on species, call surveys were carried out at seven to 28 plots with average 8.4 to 10.7 visits per the plot. We calculated the detection probabilities and occupancy rates of the three species using four models with three covariates: temperature, humidity, and the amount of water at the habitat. The model average detection probabilities of three anuran species of R. nigromaculata, R. catesbeiana, and K. borealis were 0.53, 0.74, and 0.41 respectively, and the site occupancy rates of them were 0.93, 0.94, and 0.86 respectively. Our results indicate that R. nigromaculata, R. catesbeiana, and K. borealis are common in Haenam Gun.

Large-Scale Habitat Association Modeling of the Endangered Korean Ratsnake (Elaphe schrenckii)

We used radio-telemetric monitoring and statistical models to investigate habitat associations of the endangered Korean ratsnake (Elaphe schrenckii) in a mountain region of Woraksan National Park based on the data collected from July 2007 to April 2009. We evaluated a priori models at landscape scales that incorporated natural and artificial variables to explain ratsnake presence and absence using geographic information system (GIS) databases. We generated models using logistic regression combined with Akaikes information criterion (AIC) to determine which variables are most important. The best-ranked model predicted that the ratsnakes are likely to use areas with high annual solar radiation and that they are closer to streams, coniferous and mixed forests, farmland, houses, and barren ground. We next evaluated the model by applying it to an internal and an external dataset, where the model showed high power of prediction and discrimination on the internal dataset with estimated mean probability of 94% while showing suitability as a predictive model on the external dataset with 64% probability. The present study suggests that a created habitat model can provide valuable contributions to conservation and management efforts directed towards ratsnake populations.