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Agricultural intensification, starting during the Second World War, precipitated declines in all seven native species of amphibians in Britain. Problems in the United Kingdom (U.K.) therefore predated recognition of global amphibian declines and were due to relatively simple causes, notably habitat modification and destruction. Pesticides, acid rain, ultraviolet radiation, climate change, and disease have thus far proved relatively minor issues. Amphibian conservation started in the 1970s, initially with status surveys, but by the 1980s research into habitat requirements and proactive management was underway, particularly for the rare Bufo calamita (Natterjack Toad). The relatively widespread Triturus cristatus (Great Crested Newt) was given the same legal protection as B. calamita in 1981 due largely to declines elsewhere in Europe. This protection has become problematic for conservationists on account of the many sites with this newt that regularly come under threat from development. Additional difficulties identified in the 1990s included serious impacts of road mortality on Bufo bufo (Common Toad) and inbreeding in urban populations of this species and of Rana temporaria (Common Frog). A previously unrecognized rare native, the “northern clade” of Pelophylax (formerly Rana) lessonae (Northern Pool Frog) became extinct in the early 1990s but was reintroduced in the 2000s. In the past 4 decades conservation efforts have stabilized, although not increased, the U.K. B. calamita population, but some of the widespread species are still declining, albeit at a slower rate than in the postwar period. Effective methods for amphibian conservation are now available and the outstanding question is whether there will be sufficient funding to make greater gains in future.
Ponds are an ephemeral feature of the landscape but their large-scale loss can have profound implications for biodiversity and the persistence of amphibian populations. We quantified rates of pond loss throughout Ireland over a period of approximately 125 yr. Environmental parameters and perceived risk factors associated with the current occurrence and density of the Common Frog, Rana temporaria, were also analyzed. The numbers of farmland ponds declined by 54% between 1887–1913 and 2005–11, with most ponds and the greatest losses in the East, coincident with agricultural intensification and human habitation. The decline of pond numbers was significant but, at approximately 0.5% per annum, was substantially less than losses recorded in other European countries. Losses were coincident with major changes to the agricultural landscape including extensive land drainage. However, losses of pond and natural wetland habitats throughout Ireland may have been partially or wholly mitigated by a synchronous expansion of artificial field margin ditches associated with drainage projects during the mid-20th Century. The ecology of the Common Frog in Ireland was similar to its ecology elsewhere and it appears largely unaffected by pollution and disturbance. Consequently, the conservation status of the frog in Ireland was judged “favorable” and should remain so for the foreseeable future.
Survival is an important component of population growth rate. We use data from a 9-yr mark-recapture study to estimate annual and monthly survival probabilities of adult salamanders (Salamandra salamandra). Monthly survival probability was 0.98–0.99 and did not differ between summer and winter. Annual survival probability was 0.86. These estimates are similar to estimates for other salamander species. While other studies on Salamandra salamandra concluded that this species shows high movement rates, our results suggest very low movement rates.
Die Überlebenswahrscheinlichkeit ist eine wichtige Komponente der Wachstumsrate einer Population. Wir benutzen Daten einer Fang-Wiederfang-Studie, welche neun Jahre dauerte, um monatliche und jährliche Überlebenswahrscheinlichkeiten von adulten Feuersalamandern (Salamandra salamandra) zu schätzen. Die monatliche Überlebenswahrscheinlichkeit war 0.98-0.99 und war im Sommer und Winter gleich. Die jährliche Überlebenswahrscheinlichkeit war 0.86. Diese Schätzwerte sind vergleichbar mit denjenigen von andern Salamanderarten. Während andere Studien an Salamandra salamandra zum Schluss kamen, dass diese Art viel umher wandert, deuten unsere Ergebnisse auf sehr tiefe Wanderraten hin.
We studied a population of Aesculapian Snakes (Zamenis longissimus) living close to a 1,000-m stretch of busy road located in northwestern Bohemia. We monitored the extent of road mortality and related behavioral characteristics. A large number of snakes regularly inhabited the road's embankment during monitoring in June and September. Some individuals were observed to stay in exactly the same spot continuously for several days. Snakes were active starting between 0800 and 0900 h in the morning and ending by 1900 h in June and 1800 h in September. Activity was greatest during the morning. The most frequent type of observed behavior was related to thermoregulation. The snakes did not react visibly to passing traffic. The Aesculapian Snakes' activity was higher, and started at lower temperatures, in June than in September. The mean body temperature of the Aesculapian Snakes was 24.3°C. On average, it was higher than the ambient air temperature until the ambient air temperature exceeded 27.8°C. We detected very little road mortality of adult snakes. Even though they used the road embankments and adjacent stone abutment walls frequently, they virtually never ventured onto the surface of the road. To cross the road they generally used the culverts under it. Juvenile snakes ventured onto the road frequently and their road mortality was high.
Green Frogs (genus Pelophylax) and Brown Frogs (genus Rana) differ because of behavioral reasons. Green Frogs in the adult stage are associated strongly with aquatic environment, and the Brown Frogs, apart from reproduction, spend most of their lives in the terrestrial environment. The aim of this study was to investigate the helminth fauna of these frogs from Lower Silesia (Poland) and update data on occurrence of parasites in these hosts. During faunistic investigations, 116 frogs were subjected to parasitological studies. Adult stages of all helminth groups were present in the examined frogs. The highest species richness of helminths was observed in Rana arvalis, whereas the lowest species richness occurred in Pelophylax lessonae. In the examined material, we were able to identify Nematotaenia dispar in R. arvalis. Additionally, we recorded Icosiella neglecta and Hedruris androphora in Green Frogs. The parasite communities of Green Frogs were dominated by digeneans, but terrestrial amphibians (Brown Frogs), by nematode species (i.e., Cosmocerca ornata, Oswaldocruzia filiformis, and Rhabdias bufonis).
Dispersal and vicariance are the principal mechanisms responsible for the formation of biogeographic patterns, driven or maintained by the role of past and current barriers to dispersal. Southwest Portugal harbors a rich endemic fauna and flora where strongly differentiated taxa can be observed, suggesting ancient isolating mechanisms acted in this region. In this study, we used information from two partial mitochondrial sequences, combined with information from microsatellite loci and amplification success, to investigate biogeographic patterns of genetic divergence in populations of Pleurodeles waltl in Portugal. Our results demonstrate genetic differentiation at different time frames creating distinct populations in southwest Portugal, which might have arisen following isolation by a large river estuary and mountainous barriers. Habitat destruction associated with agricultural intensification raises conservation concerns over the unique biodiversity in this region.
Stream ecosystems are particularly sensitive to urbanization, and tolerance of water-quality parameters is likely important to population persistence of stream salamanders. Forecasted climate and landscape changes may lead to significant changes in stream flow, chemical composition, and temperatures in coming decades. Protected areas where landscape alterations are minimized will therefore become increasingly important for salamander populations. We surveyed 29 streams at three national parks in the highly urbanized greater metropolitan area of Washington, DC. We investigated relationships among water-quality variables and occupancy of three species of stream salamanders (Desmognathus fuscus, Eurycea bislineata, and Pseudotriton ruber). With the use of a set of site-occupancy models, and accounting for imperfect detection, we found that stream-water temperature limits salamander occupancy. There was substantial uncertainty about the effects of the other water-quality variables, although both specific conductance (SC) and pH were included in competitive models. Our estimates of occupancy suggest that temperature, SC, and pH have some importance in structuring stream salamander distribution.
We demonstrate novel direct effects of an invasive plant metabolite on embryo development in the native Western Chorus Frog (Pseudacris triseriata) and a model organism, African Clawed Frog (Xenopus laevis). European buckthorn (Rhamnus cathartica) exhibits aggressive growth in amphibian breeding sites and releases the secondary metabolite, emodin, into soil and water. Emodin is known to have several deleterious, bioactive properties in mammals and birds, but its effects on amphibians have not been assessed. We used the FETAX (Frog Embryo Teratogenesis Assay–Xenopus) protocol to assess the effect of emodin on amphibian development in X. laevis, and modified the assay with P. triseriata to determine whether effects were consistent in a native species occurring within the range of the invasive R. cathartica. We detected and quantified emodin at amphibian breeding ponds that were infested heavily with buckthorn and have experienced recent declines in amphibian diversity and abundance. The X. laevis assay demonstrated significant embryo mortality and malformation in the presence of a gradient of concentrations of emodin including those detected in the environment. Teratogenicity indices (TI) >2 indicate the strong development-disrupting potential of emodin in amphibians. The P. triseriata assay produced similar patterns of embryo mortality and malformation as observed in the X. laevis assay. However, P. triseriata were more sensitive to emodin than X. laevis with TIs >40. Such effects may contribute to amphibian declines through depressed hatching success and poor larval survival and may represent an unrecognized impact of invasive plants more generally.
Current management strategies for the control and suppression of the American Bullfrog (Lithobates catesbeianus = Rana catesbeiana Shaw) and other invasive amphibians have had minimal effect on their abundance and distribution. This study evaluates the effects of carbon dioxide (CO2) on pre- and prometamorphic Bullfrog larvae. Bullfrogs are a model organism for evaluating potential suppression agents because they are a successful invader worldwide. From experimental trials we estimated that the 24-h 50% and 99% lethal concentration (LC50 and LC99) values for Bullfrog larvae were 371 and 549 mg CO2/L, respectively. Overall, larvae that succumbed to experimental conditions had a lower body condition index than those that survived. We also documented sublethal changes in blood chemistry during prolonged exposure to elevated CO2. Specifically, blood pH decreased by more than 0.5 pH units after 9 h of exposure and both blood partial pressure of CO2 (pCO2) and blood glucose increased. These findings suggest that CO2 treatments can be lethal to Bullfrog larvae under controlled laboratory conditions. We believe this work represents the necessary foundation for further consideration of CO2 as a potential suppression agent for one of the most harmful invaders to freshwater ecosystems.
The Northern Prairie Skink (Plestiodon septentrionalis) is listed as endangered and very little is known about habitat use in this semi-fossorial lizard. Much of the research to date has occurred on provincial park lands and federal military lands. This project aimed to define Prairie Skink habitat characteristics on exurban private land, which is defined as low-density rural residential developments, 5 to 20 acres (2 to 8 ha) in size. Prairie Skink presence data were collected using visual encounter surveys in three habitat types found on eight exurban properties in southwestern Manitoba: mowed lawn, gardens–flower beds, and native prairie. At each capture site, and at three other randomly selected sites within 10 m of each capture site, we recorded percent cover of grasses, forbs, small shrubs, bare ground, litter, and cover material. To measure thermal habitat characteristics we placed iButton® temperature loggers in each of the three habitat types. Prairie Skinks were found most commonly in native prairie and were significantly more likely to be found in areas with more artificial cover material. The number of Prairie Skink captures increased significantly as cover abundance per acre increased. Vegetation height was the most important factor moderating temperature among the habitat types. Cover may also be important on properties with minimal heterogeneity in the vegetation structure. Suitable Prairie Skink habitat exists on exurban land, specifically remnant prairie and with an abundance of artificial cover material. This type of habitat could become more important as habitat conversion continues throughout the Prairie Skink's range.
Basic information on species distribution and abundance is often lacking, even for common species. The historically abundant Mountain Yellow-legged (Rana sp.) and Pacific Treefrog (Pseudacris sp.) species complexes occur sympatrically and are exposed to similar threats. We evaluated the status of these species complexes on national forest lands in the Sierra Nevada, California as part of a long-term bioregional amphibian monitoring program. To determine occupancy and abundance indices, we surveyed all lentic and a sample of lotic habitats in 208 small watersheds (2–4 km2) selected using an unequal probability design where watersheds occupied previously had a higher likelihood of being selected. For Rana sp., results corroborated other assessments that the taxon has declined substantially. We found breeding activity in an estimated 0.04 (SE = 0.01) of watersheds rangewide, 0.47 (SE = 0.04) of watersheds with locality data from 1990–2001, and 0.02 (SE = 0.03) of watersheds with locality data prior to 1990. Less than 10% of the watersheds contained large numbers of frogs (>500 tadpoles or 100 adults subadults). In contrast, treefrogs were still distributed widely, with breeding occurring in an estimated 0.25 (SE = 0.01) of watersheds rangewide and 0.95 (SE = 0.02) of watersheds where the taxon was assumed to have occurred historically. The status of Rana sp. is consistent with broad-scale predictions that highly aquatic, specialized anuran species have an increased extinction risk. The delayed recognition of the severity of Rana sp. declines underscores the value of an early warning monitoring system for all species including common ones.
There is a paucity of empirical results regarding many aspects of the movement ecology and upland habitat use and preferences of the Eastern Spadefoot Toad (Scaphiopus holbrookii), an ephemeral, wetland-breeding anuran that is rare throughout a number of states in the northern portion of its range. We radio-tracked 45 adult Eastern Spadefoots in a coastal dune ecosystem at Cape Cod National Seashore, Massachusetts, United States and assessed a number of attributes related to the upland movement ecology and habitat preferences of this species. The mean maximum distance that we found for each of the 19 successfully tracked individuals, immediately post-breeding from the breeding wetlands, was 130.4 ± 28.0 m with a range of 3 – 449 m. Paired logistic regression results indicated that individuals selected areas closer to deciduous shrub edges and areas with greater percent cover of 1) ground-running pitch pine (Pinus rigida) branches at a 1-m scale, 2) deciduous shrubs at a 1-m scale, and 3) reindeer lichen (Cladonia sp.) at a 5-m scale compared to randomly selected locations. We recorded surface activity during 22/24 (∼91.7%) nocturnal survey nights and during 77/127 (∼60.6%) toad-nights; the presence of rainfall was the only significant predictor (positive) of surface activity. Our results provide an assessment of upland movement patterns and habitat preferences that will help guide the development and implementation of effective conservation and management strategies for this regionally rare species.
Ocean temperature is a key determinant of the distribution and phenology of marine life, particularly poikilotherms. We examined effects of ocean temperature on nesting phenology and fecundity for Loggerhead Sea Turtles (Caretta caretta) in the northern Gulf of Mexico using long-term nesting survey data from northwest Florida. The first clutch of the year was deposited earlier when sea surface temperature in months prior to the nesting season was warmer and this resulted in a longer nesting season. Nest abundance and clutch size were associated with the monthly mean temperature just prior to the nesting season, with higher fecundity occurring in warmer years. Higher nest success was associated with higher February temperature and lower May temperature. Median nest date was not associated with monthly temperature prior to the nesting season. Our results provide further details about the impacts of the thermal environment on Loggerhead Sea Turtle life history and suggest that altered ocean temperatures may affect phenology and fecundity of marine poikilotherms.
Understanding amphibian habitat associations allows us to assess the impacts of environmental change on amphibian populations. We studied the habitat associations of five anurans in the Chihuahuan Desert of southern New Mexico, USA. We used amphibian call surveys at 36 ephemeral water bodies and recorded an index of abundance for each species. We used GIS to identify vegetation communities (e.g., creosote bush, grassland, mesquite) within a buffer zone around each water site. We used ordinal logistic regression, Akaike's information criterion (AICc), and canonical correspondence analysis to elucidate relationships between an index of anuran abundance and habitat variables. Creosote bush, mesquite, and grasses dominate the landscape in our study region. We detected Anaxyrus debilis (Green Toad) and Spea multiplicata (New Mexico Spadefoot Toad) most frequently (>70% of water bodies observed). Anaxyrus cognatus (Great Plains Toad), Scaphiopus couchii (Couch's Spadefoot Toad), and Spea bombifrons (Plains Spadefoot Toad) were detected at about half of water bodies studied. Anaxyrus cognatus, Spea bombifrons, and Sp. multiplicata tended to co-occur at breeding sites. Anaxyrus cognatus and Sp. bombifrons were more common in mesquite habitat. Succulent desert scrub, though not common, seemed to affect Sc. couchii positively and A. debilis negatively. Spea multiplicata was more generalistic and did not show strong habitat associations. We did not find evidence that shrub encroachment has had negative impacts on the amphibian community in our study system and may even have had positive effects on anurans, especially A. cognatus and Sp. bombifrons.
Amphibian road mortality is a conservation concern that is receiving increased attention by the conservation community, especially given the increasing number of studies quantifying numbers of individuals that are run over by vehicles during seasonal migrations to and from breeding wetlands and during nonmigratory activity bouts on roadways. In this study we assess the activity patterns of Fowler's Toads (Anaxyrus fowleri) on an 800-m long road segment at Cape Cod National Seashore, Massachusetts, United States, over the course of an 11-wk period during the upland activity season of this species. Our results indicated that a large number of individuals were active on this road segment, even during nonrainy nights, and that some individuals spent extended periods of time on the road segment within a given night and were present on the road segment during multiple nights throughout the study duration. These findings suggest that amphibian road mortality may not be limited to seasonal migrations to and from breeding wetlands, and our results provide indirect evidence that A. fowleri individuals may be employing roadways as migration corridors, for hydro–thermo regulatory purposes, or for foraging purposes. These extended activity rates on roadways, both within and among nights, increase road-mortality risk and provide added support for conservation actions such as temporary road closure events to reduce amphibian road-mortality rates.
Ranaviruses are emerging as serious pathogens across ectothermic taxa, recently causing mass die-offs including entire chelonian populations. Amphibians may serve as reservoirs for chelonian infections. To assess this idea and determine whether chelonians in the Midwest are infected with (or at risk for) ranavirus infections, we tested for presence of ranavirus infections among sympatric larval amphibians (N = 135) and Eastern Box Turtles (Terrapene carolina carolina, N = 132) earlier and later in the Box Turtle active season (between May and October 2009) in south-central Indiana. Three larval amphibians (2.2%; one Ambystoma sp. and two unidentifiable anuran larvae) and four Box Turtles (3.0%) tested positive for a ranavirus. Ranavirus infections were found in both early-season pond breeders (anurans) and then later-season pond breeders (salamanders), spanning the Box Turtle active period, but we did not detect mass die-offs. The majority (75%) of our ranavirus-positive Box Turtles were found later in the season. This represents the first documented case of ranavirus infection among a Box Turtle population in the Midwest and one of the few studies reporting ranaviruses across wild sympatric taxa. Our results suggest that ranaviruses persist sublethally in both larval amphibians and individual Box Turtles, allowing them to serve as reservoirs for this disease. Future studies should include sampling of all sympatric herpetofauna and investigate prevalence and persistence of the viruses to understand better the risks of cross-contamination.
The colubrid snake Rhadinaea cuneata (Veracruz Graceful Brown Snake) was known previously from three individuals. In 2011 we collected two additional specimens in Yohualapa Cave, southeast Puebla, México. We provide the first description of color pattern of this species in life as well as additional natural history information.
La serpiente colúbrida Rhadinaea cuneata (Veracruz Graceful Brown Snake) era conocida previamente sólo de tres individuos. En el 2011, se recolectaron dos nuevos ejemplares en la cueva Yohualapa, localizada en el sureste de Puebla, México. Se provee la primera descripción del patrón de coloración de esta especie en vivo, así como información adicional acerca de su historia natural.
We studied the population-genetic structure of the Diamondback Terrapin (Malaclemys terrapin pileata) in Louisiana and used data from previous studies to compare our results with rangewide patterns of genetic diversity. We analyzed blood plasma to examine the contaminant load in Louisiana terrapins in the wake of the 2010 Deepwater Horizon oil spill. Using 16 polymorphic microsatellite loci, we tested for genetic structure to infer site fidelity, connectivity, and gene flow among terrapins in Louisiana estuaries. We found no evidence for population structure within Louisiana, even among sites up to 120 km apart. Comparing our Louisiana samples to data from previous studies using four loci, we found relatively low genetic diversity in Louisiana and other Gulf Coast terrapins. Based on their genetic similarity, our results support previous recommendations that two Gulf Coast subspecies be grouped into one management unit. The low genetic diversity we observed in Gulf Coast populations may be attributable to anthropogenic pressures, including massive overharvesting events in the early 20th century, from which populations have never fully recovered. Chemical analysis of plasma revealed low concentrations of contaminants, although analyses of other tissue types might have yielded a better estimate of oil contaminant sequestration for this species. Although our observed contaminant levels align roughly with levels of oiling at sampled sites, background levels as well as further analysis using more appropriate matrices (liver or fat) are needed to more accurately assess the impact of the 2010 Deepwater Horizon oil spill on the health of Gulf Coast terrapin populations.
Restoration efforts are ongoing to protect the threatened California Red-Legged Frog (Rana draytonii) from further decline, but conserving species that have aquatic and terrestrial life stages can be challenging. For example, although it is clear that aquatic habitat must be protected for breeding, less is known about the importance of terrestrial habitat. Food web linkages remain largely unknown for this species yet would offer insight on the source of prey items and, thus, the importance of each type of habitat. We used three methods to analyze food web linkages for the California Red-Legged Frog: 1) stable isotopes collected from frogs and key species in their ecosystem; 2) stomach contents sampled from live frogs in the wild; and 3) stomach contents sampled from museum specimens. The stable isotope mixing model found 99.7% of R. draytonii diet came from terrestrial prey. Wet and dry season stomach content samples flushed from captured frogs had 90% terrestrial prey, and museum specimens contained 82% terrestrial prey. These data suggest that conservation efforts should protect riparian and upland habitats adjacent to aquatic habitats in addition to aquatic habitats.
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