Academic literature on the topic 'Endangered frogs'

The gold-spotted pond frog (Pelophylax chosenicus) is an endangered amphibian species in South Korea. In order to obtain ecological information regarding the gold-spotted pond frog’s habitat environment and biological interactions, we applied stable isotope analysis to quantify the ecological niche space (ENS) of frogs including black-spotted pond frogs (P. nigromaculatus) and bullfrogs (Lithobates catesbeianus) within the food web of two different habitats—an ecological wetland park and a rice paddy. The gold-spotted pond frog population exhibited a broader ENS in the ecological wetland park than in the rice paddy. According to the carbon stable isotope ratios, gold-spotted pond frogs mainly fed on insects, regardless of habitat type. However, the results comparing the range of both carbon and nitrogen stable isotopes showed that gold-spotted pond frogs living in the rice paddy showed limited feeding behavior, while those living in the ecological wetland park fed on various food sources located in more varied trophic positions. Although the ENS of the gold-spotted pond frog was generally less likely to be overlapped by that of other frog species, it was predicted to overlap with a high probability of 87.3% in the ecological wetland park. Nevertheless, gold-spotted pond frogs in the ecological wetland park were not significantly affected by the prey competition with competitive species by feeding on other prey for which other species’ preference was low. Since these results show that a habitats’ food diversity has an effect on securing the ENS of gold-spotted pond frogs and prey competition, we recommend that the establishment of a food environment that considers the feeding behavior of gold-spotted pond frogs is important for the sustainable preservation of gold-spotted pond frogs and their settlement in alternative habitats.

Abstract The gopher frog Lithobates capito is one of the most terrestrial frogs in the southeastern United States and often inhabits gopher tortoise burrows Gopherus polyphemus outside of the breeding season. Gopher frog populations have declined, and the species is under review for listing as threatened or endangered under the U.S. Endangered Species Act. Much of our knowledge on the status of gopher frogs is based on detections of larvae at breeding wetlands, which can be challenging because of environmental variability and provides no information on the terrestrial life stages of the species. Therefore, an alternative method is called for. We recorded observations of gopher frogs during gopher tortoise surveys at four conservation lands in Florida and used line-transect distance sampling to estimate frog abundance. We also recorded burrow size, incidence of frog co-occupancy with tortoises, and distance from frog-occupied burrows to breeding wetlands. We observed 274 gopher frogs in 1,097 tortoise burrows at the four sites. The proportion of burrows occupied by gopher frogs among sites ranged from 0.17 to 0.25. Gopher frog abundance in tortoise burrows was 742 (512–1,076 95% CL) at Etoniah Creek State Forest, 465 (352–615) at Ft. White Wildlife Environmental Area, 411 (283–595) at Mike Roess Gold Head Branch State Park, and 134 (97–186) at Watermelon Pond Wildlife Environmental Area. We observed up to four frogs in a single burrow. The proportion of frogs detected in burrows occupied by a gopher tortoise ranged from 0.46 to 0.79 among sites, and overall, gopher frogs preferred burrows occupied by tortoises over unoccupied burrows (χ2 = 15.875; df = 3; P = 0.001). Gopher frogs used burrows from 7 to 43 cm in width; mean width of frog-occupied burrows did not differ from that of unoccupied burrows (F1,3 = 0.049, P = 0.825). Distance from frog-occupied tortoise burrows to the nearest breeding wetland ranged from 141 to 3,402 m. Our data on gopher frogs collected in conjunction with gopher tortoise monitoring efforts using line-transect distance sampling and burrow cameras provided novel information on frog abundance in their terrestrial habitat and required no additional effort. However, the extent to which frogs use tortoise burrows relative to other available refuges (small mammal burrows, stumps, or other structures) is unknown; thus, our estimates should be considered conservative. We suggest that terrestrial abundance estimates for gopher frogs can complement efforts to monitor breeding activity to provide a more comprehensive means of monitoring population trends in this cryptic species.

Public interest in and preferences for certain species can sometimes provide an opportunity for conservation and management. Here, we attempted to identify ‘popular’ anurans from YouTube data. In addition, the attractiveness of anuran advertisement-calling sounds were analyzed using acoustic data. By searching YouTube with the search term ‘frog calling’, 250 videos were selected. Of these, 174 videos could be classified according to species; these videos aided in extracting clean calling sounds, free from the overlapping calls of other male frogs, as well as other sounds. To assess the interests and preferences of viewers for different species, the numbers of videos, view counts, ‘likes,’ and ‘dislikes’ were recorded. From the videos, the calls of 78 species belonging to 17 families were identified. Viewer interest was highest for the Hylidae and Ranidae species, which are often discoverable in the field. In addition, invasive frogs had large numbers of videos and large numbers of ‘likes.’ People tended to prefer frogs calling with lower dominant frequencies. However, there were few videos on endangered species, and these garnered relatively less interest than other species. To manage and conserve invasive or endangered frog species, there is a need to increase ecological understanding by adjusting species awareness and charisma.

Species-specific differences in breeding strategies and physiology have limited the application of assisted reproductive technologies (ART) for critically endangered amphibians in captive assurance colonies. In 2006, the Memphis Zoo (MZ) initiated a program to develop ART for the critically endangered Mississippi gopher frog after natural breeding failed. Standard gamete collection and IVF developed by MZ for reproducing endangered toads such as the Wyoming or boreal toad were applied to the gopher frog with little success, especially hormonal therapy for sperm production. Using the leopard frog as a model species for Ranids, we tested the time and dose dependence of a luteinizing hormone releasing hormone analogue (LHRHa) and hCG on sperm quantity and quality. Initial findings from the leopard frog study were critical in designing the study on gopher frogs. Our objectives were to (1) compare 2 different hormones administered intraperitoneal (500 IU hCG vs 15 μg LHRHa) or their combination on spermiation in gopher frogs; (2) develop in vivo oocyte maturation and ovulation protocols using LHRHa (15 μg) and hCG (500 IU); and (3) transfer this technology to another institution as proof of principle. In gopher frogs, 100 and 83% of the males produced sperm in response to the LHRHa and the combination treatment, respectively, whereas only 16% responded to hCG alone. Sperm concentration peaked at 1 h post-administration for all treatments, with the LHRH/hCG cocktail treatment producing the highest concentration of sperm (mean = 4.6 × 106 ± 1.2 × 106 sperm mL–1, n = 6). No differences in motility were observed between treatments (P > 0.05). For females, a series of priming hormones of hCG and LHRHa were given several months before an ovulatory hormone regimen resulting in ovulation by 100% of the females (n = 6), whereas animals not primed failed to ovulate (n = 4). These 3 separate priming and IVF trials conducted between 2008 and 2010 resulted in each female laying ∼2000 eggs, with an average fertilization rate of 76% for inseminated eggs and hundreds of tadpoles produced. These IVF tadpoles represent the first captive reproduction of gopher frogs and highlight how ART can be applied to conservation and genetic management of threatened species. Subsequently, we tested our IVF protocols on gopher frogs at Omaha's Henry Doorly Zoo using fresh (collected on site) and chilled, shipped sperm from MZ. We collected 6169 eggs from 9 hormone-primed females with all animals ovulating. A portion of the total eggs ovulated were inseminated, resulting in 2401 fertilized eggs (38.9% of total eggs collected) across 18 different male–female pairings leading to viable tadpoles. In addition, sperm transferred overnight from the MZ produced 202/441 fertilized eggs (46%). The transfer of this technology and production of endangered amphibians using chilled, shipped sperm from live animals is a conservation milestone that can be applied to other captive breeding programs.

This study was based on the development of a non-invasive glucocorticoid enzyme-immunoassay for the assessment of stress in wild and captive endangered Fijian ground frogs (Platymantis vitiana). Enzyme-immunoassays were developed and validated for the first time to non-invasively measure both cortisol and corticosterone metabolites in frog urine. Frog urine showed parallel displacement with corticosterone but not cortisol standards, therefore corticosterone enzyme immunoassays were used to examine stress in wild and captive frogs. Urinary corticosterone metabolite concentrations increased in frog urine (n = 4) at 6 h, 1 day and 2 days after injection with adrenocorticotropic hormone (0.44 μg g–1 bodyweight), indicating that the corticosterone enzyme-immunoassay could detect changes in circulating corticosterone in frogs. Urinary concentrations of corticosterone were measured in wild frogs (n = 18) after capture in the field. The first measurement beyond the initial sample was at 2–3 h. Mean urinary corticosterone concentrations rose after the initial sample and were significantly elevated in samples collected 3–4 h after capture. This is the first demonstration of a urinary corticosterone response to capture in amphibians. Urinary corticosterone metabolite concentrations for all months combined were lower in captive males than in wild males, and differed between vitellogenic, non-vitellogenic and captive females. Concentrations did not differ between captive and wild females. In conclusion, urinary corticosterone enzyme immunoassays can be used in frogs for assessing stress responses to capture and natural stress profiles of both captive and wild populations.

A new record of the Critically frog Insuetophrynus acarpicus was discovered in Chile from a site lying 66 km southwest from the southernmost locality reported for the species. This new population is the first occurrence of the species in a protected area, and considerably extends the geographical and altitudinal range of I. acarpicus, one of the most endangered frogs in the world.

Physiological stress assessment is important for in-situ conservation and captive management of threatened wildlife. Leukocyte (white blood cell) evaluation, especially the neutrophil : lymphocyte (N : L) ratio, provides a logical representation of experimentally elevated corticosterone (stress hormone) in amphibians. Urinary corticosterone enzyme-immunoassay (EIA) is a rapid non-invasive tool for assessing stress responses in amphibians. To our knowledge, no one has explored the relationship between N : L ratio and urinary corticosterone in wild amphibians in a non-experimental way. This study provides a comparative assessment of relative leukocyte numbers, N : L ratios and urinary corticosterone responses of the endangered Fijian ground frog (Platymantis vitiana) during transportation and captivity. Adult frogs (n = 40) were collected from Viwa, Fiji Island for captive breeding. Frogs showed significant changes in leukocyte proportions during transportation and captivity. N : L ratios were higher 6 h after transportation and over 5 and 15 days in captivity. Urinary corticosterone responses of the frogs were also higher 6 h after transportation and after 5 and 15 days in captivity. All leukocyte proportions, N : L ratios and urinary corticosterone concentrations of the frogs returned near baseline levels after the frogs were kept in an environmentally enriched outdoor enclosure for over 25 days. These results highlight the value of leukocyte evaluation and urinary corticosterone EIAs as physiological tools for evaluating stress in amphibians.

AbstractWe conducted surveys for the Endangered Sierra Madre yellow-legged frog Rana muscosa throughout southern California to evaluate the current distribution and status of the species. Surveys were conducted during 2000–2009 at 150 unique streams and lakes within the San Gabriel, San Bernardino, San Jacinto, and Palomar mountains of southern California. Only nine small, geographically isolated populations were detected across the four mountain ranges, and all tested positive for the amphibian chytrid fungus Batrachochytrium dendrobatidis. Our data show that when R. muscosa is known to be present it is easily detectable (89%) in a single visit during the frog's active season. We estimate that only 166 adult frogs remained in the wild in 2009. Our research indicates that R. muscosa populations in southern California are threatened by natural and stochastic events and may become extirpated in the near future unless there is some intervention to save them.

Context. With the flow of many of the world’s rivers regulated such that water can be diverted for agriculture and human consumption, basic ecological information on the current status of key biota in significant floodplain wetlands and their response following inundation is needed. The maintenance of natural habitat to ensure amphibian survival is gaining increasing recognition, given the ongoing decline of anuran populations. Information on longevity, time required to emerge from the water and to reach sexual maturity, all provide important information about the required timing, frequency and duration of environmental water allocations to ensure successful recruitment among populations of southern bell frogs (Litoria raniformis Keferstein, 1867). Aims. The aims of this research were to establish the longevity of southern bell frogs in the Coleambally Irrigation Area (CIA) in the Riverina region of New South Wales, Australia, and to evaluate the capacity for southern bell frog tadpoles to survive and successfully metamorphose following an extended overwintering period. Methods. Skeletochronology studies were carried out using toe-clips taken from adult and juvenile frogs captured in irrigation channels and rice fields over two rice-growing seasons. For the metamorphosis assay, southern bell frog tadpoles were held back in their development by low temperatures and low food allocation for 290 days, before temperatures and food allocation were increased adequately to allow metamorphosis to occur. Key results. The study indicated that skeletochronological examination of toe-bones was a useful technique for establishing the age structure of southern bell frogs in this region. The oldest animals in the population were found to be 4–5 years old, although the majority of frogs were typically 2–3 years old. Also, the metamorphosis assay indicated that successful metamorphosis was the exception rather than the rule if tadpole development was held back by low food ration and low temperatures. Conclusions. If southern bell frogs reach sexual maturity only after 2 years, and the oldest animals observed in the field are 4 or 5 years old, then there is a very narrow window of opportunity – two to three seasons – for each individual to successfully breed. Implications. The implications for environmental flow management are that habitats for key species identified for protection such as the endangered southern bell frog will need water every 1–2 years to enable each cohort to breed and maintain the wild populations. The extent of the environmental flows needs to be adequate to ensure that water persists long enough for critical biological events such as anuran metamorphosis to occur during the spring and summer months.

The green and golden bell frog (Litoria aurea) is an Australian hylid, which was once common with a relatively continuous distribution. Historically, this distribution extended from northern New South Wales (NSW), as far as Ballina, to East Gippsland in Victoria; with inland populations as far west as Bathurst and Tumut. Today the species is reported to have disappeared from 80% of its former range and remaining populations are mostly fragmented and typically restricted to the coastline, extending from Yuraygir National Park (northern NSW) to East Gippsland. In this thesis, I report a comprehensive study designed to identify the phylogeographic and conservation genetic parameters of L. aurea. In doing so, I also investigate evolutionary relationships within the ???bell frog??? species group. In this study, microsatellite and mitochondrial DNA (mtDNA) markers are employed. The development of species-specific microsatellite markers and the collection of samples was a substantial component of the study. These markers and samples should prove useful for future studies of L. aurea and perhaps more generally the ???bell frogs???. Initially, a large-scale assessment of genetic structure and diversity in L. aurea using microsatellite markers was undertaken. Twenty-one locations were sampled from throughout the species range covering 1000 kilometres of the east coast of Australia. Levels of allelic diversity and heterozygosity were high (uncorrected mean alleles/locus and HE: 4.8-8.8 and 0.43-0.8 respectively) compared to other amphibian species and significant differences among sampled sites were recorded. Despite recent population declines, no sites displayed a genetic signature indicative of a population bottleneck. Significant genetic structuring (overall FST = 0.172) was detected throughout the species range, but was relatively low compared to previous amphibian studies that used microsatellites. In addition, some areas sampled within continuous habitat showed evidence of weak genetic structuring (data subset FST = 0.034). Next, relationships among extant bell frogs (Litoria aurea species-group) were investigated, using mitochondrial ND4 nucleotide sequence data. Analyses supported a clade comprised of the temperate members of the species-group, L. aurea, L. cyclorhyncha, L. moorei, and L. raniformis but failed to support the inclusion of the tropical bell frog L. dahlii in this group. Relationships among the four members of the bell frog clade correlated with geographical distribution: the south-western Australian bell frogs (L. cyclorhyncha, L. moorei) and the south-eastern Australian bell frogs (L. aurea, L. raniformis) were reciprocally monophyletic. Results also indicated that divergence of these two lineages occurred during the late Miocene, which was consistent with results of previous studies and with more general assertions that much of the major differentiation and radiation of the Australian biota predated the Quaternary. Following this, intraspecific phylogeography of L. aurea using two mitochondrial genes COI and ND4 was investigated. I examined extant populations from throughout the species??? range, sequencing 263 individuals from twenty-six locations. Recent evolutionary history, as well as the current population structure of L. aurea, was inferred from the resulting pattern of genetic variation amongst haplotypes, in conjunction with demographic and population analyses. Results indicated that there were no phylogeographic divisions within L. aurea, despite a general consensus that amphibians are highly structured. However, I did still detect significant structure amongst extant populations (FST = 0.385). Overall, patterns of haplotype relatedness, high haplotypic diversity (mean h = 0.547) relative to low nucleotide diversity (mean Pi= 0.003), and mismatch distribution analysis supported a Pleistocene expansion hypothesis with continued restricted dispersal and gene flow. Taken together, the results of this thesis indicate that L. aurea is a species with relatively weak population and phylogeographic structure compared to other amphibians. The data provide no support for the existence of distinct evolutionary lineages within L. aurea, implying that there are no historically isolated populations that should be viewed as separate evolutionarily significant units. Nevertheless, remaining populations are still significantly structured but not all populations are genetically distinct. Low phylogeographic structure, coupled with evidence for recent gene flow among many sites would permit ???well managed??? intervention to mediate gene flow amongst currently isolated populations, and I provide some guidelines for the implementation of such conservation strategies. However, there is no evidence to suggest that supplementation through artificial immigration is at this time necessary given current levels of genetic variation within populations. In the short-term, conservation management in L. aurea should focus on the protection of local populations and habitat to promote population connectivity to ensure processes that maintain adaptive diversity and evolutionary potential are conserved. Preservation of the species??? natural range and the maintenance of dense networks of suitable habitat, in conjunction with maximising local carrying capacity and reproductive output, as well as minimising known threats, are key to securing the long-term persistence of the green and golden bell frog.

The micro frog, Microbatrachella capensis (Boulenger, 1910), is a Critically Endangered anuran found in fragmented marshland habitats along the southern coast of the Western Cape Province of South Africa. The genetic diversity between and within the remaining populations (Kenilworth, Grootwitvlei, Kleinmond, Lamloch, Hagelkraal, and Buffeljacht/Ratelrivier) of Microbatrachella capensis in the Western Cape Province of South Africa was assessed, sampling 12 specimens from each population. Genetic diversity was determined from an analysis of mitochondrial DNA sequences obtained from the ND2 gene region/locus. A phylogeographic analysis of the populations of micro frogs sampled was used to determine the current genetic structure and the history of the species. The analysis divided the six populations of the species into two lineages. The variation within the populations ranged from two to six haplotypes per population. Nested clade analysis inferred allopatric fragmentation for three out of the five significant clades. The division of the lineages into two geographical units, the absence of gene flow and the allopatric fragmentation indicates long-term isolation, around 1.09-1.52 my ago. The isolation and fragmentation of the populations is postulated to be due to historical sea level fluctuations that occurred in Southern Africa during the Quaternary Period. Allopatric fragmentation and lack of gene flow among populations within the two major lineages are due to recent habitat destruction through development. The recognition that the species contains two evolutionarily significant units, corresponding to Agulhas and western lineages, will aid future conservation efforts to save this species.
Dissertation (MInstAgrar)--University of Pretoria, 2005.
Zoology and Entomology
unrestricted

The Pyrenean frog (Rana pyrenaica) is a Pyrenees endemic species, mostly distributed between Navarra and Aragón, and recently was described in few streams of France. The typical habitat of the species is mountain streams. It is cataloged as an Endangered, by IUCN, however we not know some aspects about it biology, natural history, as well as the current populations stats and precise distribution range. In this thesis we were done an intensive fieldwork that has allowed us collect data of distribution and density population, genetics, special connectivity and the real populations status of rana pirenaica (Rana pyrenaica) populations. About conservation status, we have increased the known distribution range of the species with new localities, even if the species was disappeared in many historical localities, for not known reasons. The estimated population size is low in many localities, so local extinctions probabilities is higher. The rana pirenaica is genetically homogeneous, both using mitochondrial genomes and nuclear marker (SNPs), and has suffered a bottleneck with subsequent geographical expansion since the Last Glacial Maximum. The differences between western and east populations cores are minimal for Mitochondrial DNA, and there has been a recent gene flow between populations through the pre-Pyrenees. In Nuclear genes is observed a population division during the Holocene in five or six genetically differentiation cores. The landscape genetics analyses suggest that big rivers and pronounced unevenness have acted as barriers that allowed this differentiation, and exist an effectiveness separation between the species eastern and western cores. The lethal amphibian fungi Batrachoquitrium dendrobatidis was massively detected throughout the occurrence area of R. pyrenaica, even though the fungi impact on the specie is not known. The forecast climate models predict that growth chytrid conditions will be better in high elevation under Global Change scenarios, that high elevation populations of many amphibians’ species may be affected. The obtained data confirmed rana pirenaica as an Endangered species. A series of management measures of in situ conservation is proposed, as well as conservation unities in the whole distribution area. This work has made possible identify management measures for these species as well as assessing their current conservation status, which we hope will help the conservation of the species in Navarra and Aragón and especially in the Ordesa and Monte Perdido National Park, which is the only one that harbors Pyrenean frog populations.
La rana pirenaica (Rana pyrenaica) es una especie endémica de los Pirineos, que se distribuye principalmente entre Navarra y Aragón, y habita en ríos de montaña. Ha sido catalogada por la IUCN como una especie en Peligro de Extinción, si bien se desconocen muchos aspectos de su biología, historia natural, así como el estado actual de sus poblaciones y distribución precisa. En esta tesis se ha realizado un trabajo de campo intenso que nos ha permitido recabar datos de distribución y densidad poblacional, genética, conectividad espacial y estado de las poblaciones de la rana pirenaica (Rana pyrenaica). En cuanto al estado de conservación, hemos incrementado el área de distribución conocida de esta especie con nuevas localidades, si bien varias poblaciones históricas han desaparecido por causas desconocidas. El tamaño poblacional estimado es bajo en muchas localidades, por lo que la probabilidad de extinción local es elevada. La rana pirenaica es muy homogénea genéticamente, tanto empleando genomas mitocondriales como con marcadores nucleares (SNPs), y ha sufrido un cuello de botella con posterior expansión geográfica desde la última glaciación. Las diferencias entre el núcleo oriental y occidental son mínimas en ADN mitocondrial, y ha existido un flujo genético reciente entre poblaciones a través del pre-Pirineo. En genes nucleares se observa una división poblacional durante el Holoceno en 5 o 6 núcleos genéticamente diferenciados. Los análisis de genética del paisaje sugieren que los principales ríos y desniveles pronunciados han actuado como barreras que permitieron esta diferenciación, y existe una separación efectiva entre el núcleo oriental y occidental de la especie. Se ha detectado la presencia masiva del hongo Batrachoquitrium dendrobatidis en todo el área de distribución de rana pirenaica, si bien su impacto en la especie es desconocido. Los modelos de clima futuro predicen que las condiciones de crecimiento del quítrido serán mejores en altitudes mayores bajo escenarios de cambio global, de forma que las poblaciones de altitud de muchas especies de anfibios se podrán ver afectadas. Los datos obtenidos confirman a rana pirenaica como en Peligro de Extinción. Se proponen una serie de medidas de gestión para la conservación in situ de la especie, así como unidades de gestión en toda el área de distribución. Este trabajo ha permitido identificar medidas de gestión de estas especies así como valorar su situación actual de conservación, las cuales esperamos que sirvan de ayuda a la gestión de la especie en Navarra y Aragón y especialmente en el Parque Nacional de Ordesa y Monte Perdido que es el único que alberga poblaciones de rana pirenaica.

Amphibians are suffering extinctions and range contractions globally. This is caused by numerous factors and most of them are related to human activities. The overall aim of this thesis was to make a significant contribution to the conservation of the endemic amphibian Leiopelma hochstetteri through research. This was achieved by focusing in two of the main conservation issues for this species, the need for standardised and robust monitoring techniques to detect trends and changes in populations, and the determination of the prevalence of chytridiomycosis, caused by the amphibian chytrid fungus (Batrachochytrium dendrobatidis). Two populations of the Auckland Region were selected for this study, one on the mainland (Waitakere Ranges) and the only known offshore island population of this species (Great Barrier Island). For both study sites different monitoring methods were used to obtain some population parameters. Site occupancy models of MacKenzie et al. (2002) gave reliable site-specific estimations of occupancy and detection probability using covariate information and presence-absence data collected from 50 sites in the Waitakere Ranges and four repeated visits during 2008. Elevation and distance searched were found to have an important effect on occupancy levels, while time taken to search the site was important variable determining detection probabilities. Also, parameters were estimated for three age classes separately. Statistical models were used to infer abundance from occupancy analysis, and results were compared with the distribution of relative abundances obtained from repeated transect counts and an established sight/re-sight criterion. In addition, the use of surrogate measures for relative abundance was explored. Detection probability and the distance to first frog found were found to have a significant correlation with relative abundance. These measures can be used to infer relative abundance in future site occupancy surveys. Two surveys and a pilot site occupancy survey were conducted on Great Barrier Island, and presence of frogs was confirmed atthe northern block, and in a small seepage in the central block. No new locations were found. Waitakere Ranges and Great Barrier Is. populations were tested for the presence of chytridiomycosis, and all frogs sampled tested negative (n = 124) which means that if present chytridiomycosis prevalence is lower than 5% with a 95% confidence interval. This and previous evidence suggests that L. hochstetteri may be resistant or immune to the disease. However, to confirm this additional studies are needed.

Amphibians globally are declining with roughly a third facing extinction due primarily to threats linked to human impacts. One way in which this is being combated is by captive breeding programs. Nordens Ark in Sweden, in collaboration with other organizations, is attempting to breed one of the most threatened frogs for future reintroduction to the wild. The mountain chicken (Leptodactylus fallax) has unique characteristics related to its reproduction which make it challenging to breed successful offspring. Using Nordens Ark’s data on environmental conditions within breeding enclosures, this study attempts to determine which extrinsic factors are having the most influence on reproduction, in order to increase the success of the captive breeding program. Multiple linear regression analysis and model simplification using Stepwise regression and Akaike information criterion (AIC) were performed in order to determine which explanatory variables had the most influence in relation to foam nests. A reduced model with significant values for explanatory variables was deemed the best model based on the dataset. Of the 14 environmental variables tested, minimum temperature after nest construction had the most influence on foam nest length. When compared to wild habitats, temperatures within enclosures may be too high or lack seasonal cyclical patterns. Barometric pressure and humidity also had influence on foam nests, but the relationships between these environmental conditions is difficult to parse. Food supplements were also a significant factor and suggest that lack of vitamins or nutrients can have a negative effect on reproductive success. Ensuring the optimal conditions can be difficult for captive breeding programs, especially as amphibians are under-represented and face biases in conservation and research.

Many amphibian populations are rapidly disappearing throughout the world. An important issue for ecologists is why some amphibian species are more susceptible to decline than others. Here I present five experiments that compare the performance of an endangered (Rana sevosa) and a common (Rana sphenocephala) frog in changing habitats, to determine why these two species differ in their persistence. I include additional studies investigating the habitat requirements and behavior of R. sevosa. I found that habitat change in the form of canopy closure over breeding ponds negatively affects both species, making them smaller as tadpoles and at metamorphosis. The magnitude of size differences was greater for R. sevosa and this species was less likely to survive in closed canopy ponds. Larval survival was not affected in R. sphenocephala and this is likely a key reason for the persistence of this species in habitats where R. sevosa has been extirpated. The introduction of fish to breeding ponds would also differentially affect the two species. R. sevosa did not display behavioral defenses to the threat of fish predation while R. sphenocephala did. R. sevosa displayed a preference for certain characteristics in its habitat including open canopy ponds, grassy terrestrial habitats and an abundance of burrows. An association with the chemical cues of burrow making organisms suggests that these organisms may be important for R. sevosa. Therefore, specialized habitat requirements and behaviors which may be contributing to its decline. I found some evidence of asymmetric competition in the larval stage with R. sevosa negatively affecting R. sphenocephala. It does not appear that larval competition with R. sphenocephala has contributed to the decline of R. sevosa. The primary difference between the two species was in responses to habitat change. R. sevosa appears to be rigid in its habitat requirements and behavior and its inability to respond and adapt to change is a key component of its rarity. By contrast R. sphenocephala showed an ability to cope with habitat changes. Conservation of R. sevosa will require suitable management of the aquatic and terrestrial habitats, primarily through the instigation of an appropriate fire regime.

Amphibian populations have undergone unprecedented declines in recent decades. Many of these declines are due to the spread of the cutaneous fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes the disease chytridiomycosis. The Panamanian golden frog (Atelopus zeteki) has not been seen in the wild since Bd spread through western Panama. In response to initial declines, golden frogs were collected from wild populations and placed in captive colonies with the goal of future reintroductions. An understanding of this species' natural defense mechanisms against Bd is needed for reintroduction to be successful. Previous studies indicate that cutaneous bacteria are an important defense mechanism for some amphibians and applying antifungal bacteria to the skin of Bd-susceptible amphibians (probiotic therapy) can prevent chytridiomycosis. Therefore, the goals of my dissertation were to characterize the bacterial community of A. zeteki and determine if probiotic therapy could be used to prevent chytridiomycosis in this species. I initially characterized the bacterial community of wild and captive golden frogs using samples collected prior to the initial declines and after approximately eight years in captivity. I found that the community structure of the microbiota was significantly different between wild and captive frogs; however, the offspring of the original captive frogs still shared 70% of their microbial community with wild frogs. Then, I characterized the Bd-inhibitory properties of 484 bacteria isolated from 11 species of free-living Panamanian amphibians. I found a large proportion of bacteria (75.2%) had the ability to inhibit Bd and this trait was widely distributed among bacterial taxa, although there was also significant variation within bacterial genera in their ability to inhibit Bd growth. I then experimentally tested the ability of four of these isolates to prevent chytridiomycosis in captive golden frogs. None of them successfully prevented infection; however, there were several frogs that cleared infection and this was correlated with composition of the bacteria initially present on their skin. Overall these results demonstrate that the structure of microbial communities of A. zeteki are important to host health and building on this might provide the best hope for reintroducing this iconic species back to its native habitat.
Ph. D.

The documented decline of amphibian populations over the past two decades has increased attention towards amphibian conservation. Much of this attention has been focused on testing hypotheses as to the causal factors of these declines, however providing convincing data to support any of these hypotheses has proved difficult. The testing of these hypotheses and the implementation of endangered species recovery programs has been restricted by a lack of knowledge of the ecology and population demography of amphibian species that have suffered dramatic declines. This thesis presents aspects of the research phase of the recovery program for the Southern Corroboree Frog, Pseudophryne corroboree, a species that declined to very low numbers during the early 1980's. In particular, this research aimed to determine the distribution, abundance, population dynamics and demography of this rare species. A complete reassessment of the conservation status of P. corroboree was undertaken and the nature of the persistence of this species across the landscape was analysed. Temporal trends in abundance and its relationship with population size were also investigated. Early life-history survivorship and recruitment to metamorphosis were studied at the scale of individual nest sites and populations, and the adult male population age structure and annual mortality were investigated using skeletochronology. The shout/response survey technique was used to survey and monitor the number of breeding male P. corroboree during this study. This method was found to provide consistent results when the surveys were conducted over a short (two week) period during the peak breeding season in January. Neither time of day, nor the number of males present at a pool, was found to influence the level of responsiveness of male P. corroboree to the shout/response technique. Variation in the number of responding males to the shout/response technique through the breeding season, assessed at a single site over two seasons, was unimodal with the peak responding period occurring during the last two weeks of January during both the 1998 and the 1999 breeding seasons. A systematic survey covering 213 sites across the entire historic distribution of P. corroboree found this species to be persisting at 79 sites. The majority of these sites were in the northwestern portion of the species former range, around the Jagungal Wilderness area, while no extant sites were found in the south-eastern portion of the species former range in the Smiggin Holes and Perisher Blue ski resorts area. The overall abundance of males at persistent sites was extremely low, with 92 percent of sites having fewer than ten responding males. Only one site was found to support greater than fifty responding males. A logistic regression analysis found the persistence of P. corroboree to be associated with increased number of pools within a site, decreased distance to nearest extant population and geographic position (latitude and longitude) in the landscape. While annual variation was observed in the number of breeding males for individual sites, there was no overall trend for an increase or decrease in the number of males, regardless of population size. The average annual extinction rate for local populations was five percent during this study, with those populations becoming extinct having very few breeding males (between one and three) during the previous season. Embryonic and tadpole survivorship was monitored for individual nests at three sites across three years. Recruitment to metamorphosis for P. corroboree was characterised by high variation in survivorship between nest sites, populations and years, while overall recruitment for nest sites was skewed towards lower survivorship. Average nest survivorship to metamorphosis across all sites and years was ten percent but the skewed nature of this survivorship meant that the majority of nest sites attained very low or no survivorship. The low proportion of nest sites that did attain high survivorship provided the greatest contribution to overall recruitment. The levels of embryonic and tadpole mortality observed in this study would be providing a considerable contribution to the regulation of current population sizes. The greatest level of early life-history mortality was observed during the late autumn/winter egg and tadpole stage, with high survivorship during the summer and early autumn egg stage and the post-winter tadpole stage. The estimated sex ratio for seven populations, based on the number of eggs within male nest sites, indicated that for most populations, regardless of population size, there was a greater proportion of females to males. In general, the estimated sex ratio of smaller populations showed greater annual variation and had a lower average number of females to males than the single large population. Tadpole surveys conducted across remnant populations during both 1998 and 1999 found recruitment to metamorphosis to be very low for the majority of populations. A third of all populations during both years attained no recruitment to metamorphosis, with those populations that did attain recruitment typically having fewer than 20 tadpoles. While sites with more frogs generally recruited more tadpoles, there was no strong relationship between population size and the number of tadpoles recruited per male at the scale of either pool or site. There was also no significant difference in recruitment levels between the two years. Tadpole surveys across breeding pools within the single large population also found very low tadpole abundance. There was no strong relationship between the number of male frogs at a pool and the number of tadpoles per male and there was no significant difference in tadpole abundance between the two years. Based on the low density of males at pools and sites (typically less than five), and the skewed nature of nest survivorship identified from monitoring individual nest sites, it seems likely that both deterministic and stochastic factors are influencing recruitment levels in remnant populations of P. corroboree. This study determined that adult male P. corroboree could be accurately aged using the technique of skeletochronology, and this technique was used to determine the adult male population age structure for three populations. The results indicated that adult male P. corroboree can reach sexual maturity from metamorphosis in three years, but the majority of individuals take four years. The oldest individual identified in this study was nine years old from metamorphosis. The adult male age structure at the single large site showed very little annual variation, whereas the two smaller populations showed highly pulsed age structures from one year to the next. The size of adult males was found to be a poor predictor of age. Annual adult male survivorship, calculated by following cohorts from one year to the next, was 55 percent. Based on this calculation of annual adult male survivorship, it seems likely that the initial decline in P. corroboree involved increased levels of adult mortality. The results of this study indicate that the persistence of. corroboree in the wild is precarious in the short-term. For this reason, it is recommended that efforts be undertaken to secure this species ex situ. Attempts to increase population numbers in the wild would greatly benefit from determining the factor(s) that have caused the decline in this species, however, failure to do so should not preclude field experimental management aimed at developing technique to increase the size of remnant populations. This is because it is likely that small population stochasticity is contributing to the current regulation of population size and it is possible that the factors that caused the decline in this species cannot be removed from the environment.

I have something to show you. I just got it by overnight delivery.” My student’s face was a blaze of eagerness. From his backpack, he pulled out a small box. Seconds later, magically cupped in his hands was a tiny, neon lime green frog with black eyes. This was hardly the fare for a usual student–teacher appointment. But Blake Klocke is no ordinary university student, though he appears so—the same blue jeans and backpack uniform, laptop at the ready. The difference is not his red hair and freckles, but his amphibian excitement. On his laptop, he displayed for me dozens of frog-related book-marked websites, which he explained aglow with enthusiasm. He had been raising frogs since he was nine, being part of a rescue train across the world of hobbyists who have been keeping the genetic strains of frogs alive in their homes as they are being extinguished in the wilds. Zoos don’t have the space or the avid visiting publics to care about these small, diverse members of the living community, so without the care of personal frog lovers like Blake in raising captive-bred endangered amphibians, our world would have lost these strands of life’s web. The black-eyed tree frog is a critically endangered Central American species that is decreasing so rapidly that scientists predict it will be reduced by 80% in the wild in ten years by the life-sucking, zombie-like Chytrid fungus that is wiping out full populations. “Once my frogs have young, I can get you some so you can raise your own,” Blake offered, ready to convert me to the simple joys of amphibian care. Blake has experienced this excitement from his youth on, and his outdoors adventures have created a love in him that will carry him far— far beyond the lakes and wetlands near Eagan, Minnesota, where he first started catching tadpoles. This finding the “drama in the bush” is just what Leopold had been advocating in his classes, radio talks to young farmers, and writings about the sport of amateur naturalist studies.

Some days, now that I have crested 50, I find myself surprised to be, of all things, a science reporter on a daily newspaper in a small but sophisticated city and immersed every day in a world of stem cells, radio-collared bald eagles, flakes of Martian meteorites, and strange deer diseases. I can't imagine a place I'd rather be at this point in my life, though sometimes the haphazard way I got here, the serendipitous nature of it all, makes my head spin—not to mention the fearful task of trying to make something called “proteomics” understandable for an audience that has maybe a minute and a half to read what I've written. After all, I made a terrible mess of the frog I was supposed to dissect in high school all those years ago. And trying to figure out exactly what Mendel was doing with all of those pea plants drove me nuts. Math? Well, suffice it to say that my problems with algebra and equations are what drove me to a career in journalism. Still, here I am, settled in Madison, Wisconsin, in the upper Midwest of America, carrying around business cards that identify me as science and environment reporter for the Wisconsin State Journal. In a recent, typical week, I researched and wrote a column about robotics, pounded out a quick news feature about why the human body gets cold in winter, made pesky phone calls to state officials about why they aren't enforcing the state's new pollution law, and churned out news briefs on everything from clouds of ionized hydrogen in the solar system to a pollution permit hearing for a local manufacturing plant. Between assignments, I had time to give a talk about science writing to a local high school biology class and to win one of the ongoing games of Scrabble in the cubicle at the newspaper where I make my workday home. Not a day goes by that I don't worry about losing this good job. That's because full-time science reporters on small to mid-sized daily newspapers in this country are an endangered species.

The management and recovery of threatened and endangered amphibians on Department of Defense (DoD) lands relies on an understanding of their distribution and abundance. Fortunately, most anuran species can be surveyed acoustically using vocalizations during the breeding season. This work demonstrated the use of subsurface passive acoustic monitoring (SPAM) to survey for rare underwater-calling, at-risk anuran species on DoD installations. We evaluated the performance of SPAM relative to traditional passive acoustic monitoring (PAM) (microphone) and human manual calling survey (MCS) methods. Results showed that SPAM outperformed PAM and MCS in validation experiments where calls were generated underwater; SPAM was less successful than PAM and MCS in the field demonstration. Most leopard frog calls were apparently produced in air despite previous reports of extensive underwater-calling behavior. This project highlights how acoustic information can help address a data gap in the ecology of at-risk species, which can help refine future survey methodology and management efforts. Ultimately, the utility of SPAM for underwater-calling species will depend on the focal species, the landscape where it occurs, and technological considerations available to the surveyor. SPAM is more expensive than traditional methods but, in some situations, may be the only way to effectively detect species.