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At least 37 records · Page 2Linked to original sources
USGS2005

Evidence of decline for Bufo boreas and Rana luteiventris in and around the northern Great Basin

A method is described for the analysis of polychlorinated biphenyl (PCB) compounds in tissue samples. Cleanup by hexane-aceto-nitrile partitioning and Florisil column chromatography are performed on samples before oxidative treatment to convert DDE to DCBP. PCB components are then determined semi-quantitatively by TLC. No prior separation of PCB from chlorinated pesticides is required. The lower limit of sensitivity is 0.2 ?g.

Alytes↗
USGS2017

Between hot rocks and dry places: The status of the Dixie Valley toad

In Dixie Valley, Nevada, an isolated population of toads has been the subject of proactive conservation measures by the Nevada Department of Wildlife and the U.S. Fish and Wildlife Service since 2008 due to concerns about potential habitat degradation resulting from exploitation of nearby geothermal energy resources. These toads appear to belong within the Anaxyrus boreas species group but are commonly referred to as Dixie Valley toads (DVTs). The DVT is currently confined to an extremely narrow habitat range (370 ha) that is geographically isolated from any other A. boreas population. In this study, genetic variations in mitochondrial genes and 11 microsatellite loci were used to assess the affinities of DVTs in relation to members of the A. boreas species group. We compared results from DVTs with previously published data spanning much of the range of A. boreas in the United States and new data from a nearby toad population within Dixie Valley. Data from both mitochondrial DNA and microsatellites placed DVTs inside the A. boreas species group. In particular, DVTs fell into a cluster of A. boreas from Washington and California, along with other species from the A. boreas species group, namely A. nelsoni, A. canorus, and A. exsul. Genetic differentiation of DVTs was lowest between A. boreas populations in Washington and California. However, allele frequencies were significantly different between DVTs and all other populations, including a nearby locality within Dixie Valley. This genetic differentiation, along with the DVT's geographical isolation and restricted habitat, warrants recognition of the DVT as a distinct management unit.

Nevada↗
USGS2003

Effects of ultraviolet radiation on toad early life stages

Background Exposure to harmful levels of ultraviolet-B radiation (UVB), a component of solar radiation, has been suggested as a potential cause of amphibian declines. Methods We measured solar radiation (UVB, ultraviolet-A, and visible) wavebands in breeding ponds of Bufo boreas (boreal toad, a montane species that has undergone severe population declines) and Bufo woodhousii (Woodhouse’s toad, a plains toad that has not experienced declines) and examined tolerances of these species to simulated solar UVB exposures in the laboratory. Results We found larvae of both species to be tolerant of simulated solar UVB in excess of solar UVB levels observed in their breeding ponds. B. boreas tadpoles were more tolerant of simulated solar UVB exposure than B. woodhousii tadpoles, possibly because of greater amounts of photoprotective melanin in B. boreas skin. Conclusions UVB levels observed in B. boreas habitats do not currently appear to constitute a threat to the survival of these animals; however, long-term (>1 month) exposure to UVB levels comparable to levels associated with the water interface appears to reduce survival in B. woodhousii tadpoles. Therefore, future increases in surface and water column UVB radiation in bufonid habitats might pose significant survival risks to B. boreas or B. woodhousii populations.

Environmental Science and Pollution Research↗
USGS1998

Effects of ultraviolet radiation on boreal toads in Colorado

Field exposures of Bufo boreas embryos to fractions of ambient UV-B radiation at two sites in Rocky Mountain National Park, Colorado, USA, were conducted to evaluate UV-B as a possible cause of recent severe declines of this species. There were no differences in hatching success of B. boreas embryos exposed to 0–100% of ambient UV-B radiation at either study site, results that are different from those of recent studies in Oregon that found increased mortality of B. boreas embryos exposed to ambient UV-B. The reasons for these differing results are not apparent, and several possible explanations exist, including differences in experimental design, presence or absence of a pathogenic fungus, and geographic genetic variation. Bufo boreas embryos were probably not receiving higher doses of UV-B radiation during the experiments in Oregon compared to the experiments in this study. Results of this study do not support UV-B radiation alone as the cause of the decline of B. boreas during the past 20 yr in the southern Rocky Mountains, but UV-B cannot be dismissed because of the contradictory results from other studies.

Colorado↗
USGS2016

A model to inform management actions as a response to chytridiomycosis-associated decline

Decision-analytic models provide forecasts of how systems of interest will respond to management. These models can be parameterized using empirical data, but sometimes require information elicited from experts. When evaluating the effects of disease in species translocation programs, expert judgment is likely to play a role because complete empirical information will rarely be available. We illustrate development of a decision-analytic model built to inform decision-making regarding translocations and other management actions for the boreal toad (Anaxyrus boreas boreas), a species with declines linked to chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd). Using the model, we explored the management implications of major uncertainties in this system, including whether there is a genetic basis for resistance to pathogenic infection by Bd, how translocation can best be implemented, and the effectiveness of efforts to reduce the spread of Bd. Our modeling exercise suggested that while selection for resistance to pathogenic infection Decision-analytic models provide forecasts of how systems of interest will respond to management. These models can be parameterized using empirical data, but sometimes require information elicited from experts. When evaluating the effects of disease in species translocation programs, expert judgment is likely to play a role because complete empirical information will rarely be available. We illustrate development of a decision-analytic model built to inform decision-making regarding translocations and other management actions for the boreal toad ( Anaxyrus boreas boreas ), a species with declines linked to chytridiomycosis caused by Batrachochytrium dendrobatidis ( Bd ). Using the model, we explored the management implications of major uncertainties in this system, including whether there is a genetic basis for resistance to pathogenic infection by Bd , how translocation can best be implemented, and the effectiveness of efforts to reduce the spread of Bd . Our modeling exercise suggested that while selection for resistance to pathogenic infection by Bd could increase numbers of sites occupied by toads, and translocations could increase the rate of toad recovery, efforts to reduce the spread of Bd may have little effect. We emphasize the need to continue developing and parameterizing models necessary to assess management actions for combating chytridiomycosis-associated declines. by Bd could increase numbers of sites occupied by toads, and translocations could increase the rate of toad recovery, efforts to reduce the spread of Bd may have little effect. We emphasize the need to continue developing and parameterizing models necessary to assess management actions for combating chytridiomycosis-associated declines.

EcoHealth↗
USGS1997

Survey and assessment of amphibian populations in Rocky Mountain National Park

We conducted surveys in Rocky Mountain National Park, Colorado for amphibians in 1987-1994. Four species, Ambystoma tigrinum, Bufo boreas, Pseudacris maculata, and Rana sylvatica , were recorded. Pseudacris maculata was the most widely distributed and abundant species in the Park. Two populations of E maculata were estimated to contain 161 and 136 breeding males in 1988. There was no evidence of a decline of A. tigrinum or R. sylvatica , but these species were found at relatively few locations. We did not detect Rana pipiens , which had been known previously from 3 locations in the Park. We found 7 breeding populations of B. boreas , which has declined recently elsewhere in the southern Rocky Mountains, but all but 2 of these populations were small and may not reproduce annually. At least one of these small populations is thought to have been extirpated. Estimated numbers of males in the 2 large populations, which are 6.4 km apart in the same drainage, were stable or increasing slightly from 1992 to 1995, averaging 189 and 239 individuals. Current and known locations of amphibians did not differ in elevation, size, lake type, presence of shallow water or emergent vegetation on the north shore, or presence of trout. Water chemistry at amphibian breeding sites was variable, but pH decreased significantly with increasing elevation. Causes of declines of B. boreas and R. pipiens are not known. Populations of B. boreas in the North Fork of the Big Thompson River are critically important to the conservation of this species in the Rocky Mountains.

Colorado↗
USGS2001

Moss and lichen cover mapping at local and regional scales in the boreal forest ecosystem of central Canada

Mosses and lichens are important components of boreal landscapes [Vitt et al., 1994; Bubier et al., 1997]. They affect plant productivity and belowground carbon sequestration and alter the surface runoff and energy balance. We report the use of multiresolution satellite data to map moss and lichens over the BOREAS region at a 10 m, 30 m, and 1 km scales. Our moss and lichen classification at the 10 m scale is based on ground observations of associations among soil drainage classes, overstory composition, and cover type among four broad classes of ground cover (feather, sphagnum, and brown mosses and lichens). For our 30 m map, we used field observations of ground cover-overstory associations to map mosses and lichens in the BOREAS southern study area (SSA). To scale up to a 1 km (AVHRR) moss map of the BOREAS region, we used the TM SSA mosaics plus regional field data to identify AVHRR overstory-ground cover associations. We found that: 1) ground cover, overstory composition and density are highly correlated, permitting inference of moss and lichen cover from satellite-based land cover classifications; 2) our 1 km moss map reveals that mosses dominate the boreal landscape of central Canada, thereby a significant factor for water, energy, and carbon modeling; 3) TM and AVHRR moss cover maps are comparable; 4) satellite data resolution is important; particularly in detecting the smaller wetland features, lakes, and upland jack pine sites; and 5) distinct regional patterns of moss and lichen cover correspond to latitudinal and elevational gradients. Copyright 2001 by the American Geophysical Union.

Journal of Geophysical Research D: Atmospheres↗
USGS2021

Thermal conditions predict intraspecific variation in senescence rate in frogs and toads

Variation in temperature is known to influence mortality patterns in ectotherms. Even though a few experimental studies on model organisms have reported a positive relationship between temperature and actuarial senescence (i.e., the increase in mortality risk with age), how variation in climate influences the senescence rate across the range of a species is still poorly understood in free-ranging animals. We filled this knowledge gap by investigating the relationships linking senescence rate, adult lifespan, and climatic conditions using long-term capture–recapture data from multiple amphibian populations. We considered two pairs of related anuran species from the Ranidae ( Rana luteiventris and Rana temporaria ) and Bufonidae ( Anaxyrus boreas and Bufo bufo ) families, which diverged more than 100 Mya and are broadly distributed in North America and Europe. Senescence rates were positively associated with mean annual temperature in all species. In addition, lifespan was negatively correlated with mean annual temperature in all species except A. boreas . In both R. luteiventris and A. boreas , mean annual precipitation and human environmental footprint both had negligible effects on senescence rates or lifespans. Overall, our findings demonstrate the critical influence of thermal conditions on mortality patterns across anuran species from temperate regions. In the current context of further global temperature increases predicted by Intergovernmental Panel on Climate Change scenarios, a widespread acceleration of aging in amphibians is expected to occur in the decades to come, which might threaten even more seriously the viability of populations and exacerbate global decline.

Proceedings of the National Academy of Sciences↗
USGS1981

U-Th-Pb systematics of some granitoids from the northeastern Yilgarn Block, Western Australia and implications for uranium source rock potential

The Mount Boreas‐type granite and spatially associated syenitic granitoid of Western Australia yield Pb‐Pb ages of 2370 ± 100 Ma and 2760 ± 210 Ma, respectively. Th‐Pb ages, although less precise, are concordant with these ages, and therefore the apparent ages are interpreted to be the crystallisation ages for these two units. U‐Pb ages are variable and for the most part anomalously old, which suggests a Cainozoic uranium loss. However, this loss is generally small (< 3 μ g/g); therefore, neither granitoid in its fresh state provides a good source for nearby calcrete‐hosted uranium deposits. The possibility remains that the Mount Boreas‐type granite that has been completely weathered during the Tertiary could have been a source for the calcrete‐type uranium deposits in W.A. Although the Mount Boreas‐type granite is highly fractionated, it does not bear a strong geochemical imprint of a sedimentary precursor. This feature contrasts it with apparently fresh granitoids from other parts of the world that have lost large amounts of uranium (∼ 20 μ g/g ) and are associated with large roll‐type and other low temperature‐type uranium deposits.

Journal of the Geological Society of Australia↗
USGS2022

Changes in stream chemistry in the east-central Adirondack region of New York State, 2010–2018

Decreased acidic deposition occurred through the 2010s, extending the long-term decrease begun in the early 1980s. The overall decline has resulted in rates of acidic deposition in the Adirondack region that are similar to those estimated for the early 1900s. This achievement increased attention on the issue of acidic deposition recovery and raised the question of how the low deposition levels of the 2010s were affecting the Adirondack region of New York State, where past acidic deposition effects were among the highest in the United States. This report presents stream resampling results of the East-Central Adirondack Stream Survey (ECASS), the Adirondack high-elevation stream sampling program, and the first five years of stream chemistry measurements in the Boreas River Long-Term Monitoring Watersheds. In addition, a regional comparison of stream chemistry between ECASS and the Western Adirondack Stream Survey (WASS) is presented. The primary objective of these stream resampling programs was to evaluate changes in stream chemistry during the 2010s to evaluate ongoing recovery of acidic deposition within the Adirondack region. Streams in the ECASS region (19,658 km 2 ) were sampled during spring snowmelt in 2011, 2017, and 2018; summer baseflow in 2010 and 2017; and late autumn in 2011 and 2017. ECASS stream sampling results for snowmelt in 2018 are also compared with WASS stream sampling results during snowmelt of the same year to provide a spatial assessment of stream chemistry for the entire Adirondack region. In addition, high-elevation streams were sampled in 2010-2011 and 2017 during spring snowmelt and summer baseflow, and three streams in the Boreas River watershed were sampled biweekly from 2014 through 2019. Streams were selected for sampling from the approximately 200 streams sampled originally in both the ECASS and WASS. The original ECASS and WASS streams were randomly selected from the populations of accessible streams within their respective regions. For the study reported here, subsets of streams were selected from the two original groups using a random stratified design based on the stream chemistry of the original ECASS and WASS. ECASS data are presented only for streams that were sampled in each of the seasonal surveys, which was 59, 48, and 61 streams for spring snowmelt, summer baseflow, and autumn surveys, respectively. WASS data are presented for 60 streams and high-elevation data are presented for 11 streams sampled during summer baseflow and 12 streams sampled during spring snowmelt. Overall, mean values of chemical measurements did not indicate large changes between 2010-2011 and 2017-2018 in the ECASS snowmelt, summer baseflow, or autumn surveys. Minimal acidification was observed in mean values measured in any of the surveys. Mean values of acid-neutralizing capacity (ANC) remained above 80 microequivalents per liter (µeq L -1 ), mean pH remained above 6.37, and inorganic monomeric aluminum (Al i ) remained below 1.0 micromoles per liter (µmol L -1 ), with the exception of the mean value of 1.2 µmol L -1 in the 2017 autumn survey. However, in the 2017 and 2018 snowmelt samplings 15% and 10% of the streams, respectively, had Al i concentrations above 1.0 µmol L 1 , the concentration above which is toxic to fish. Based on the estimated total length of headwater streams in the ECASS region of 11,494 km, the 10% of ECASS streams that experienced harmful Al i concentrations (Al i >1.0 µmol L -1 ) during the 2018 snowmelt survey equated to a total length of 1,091 km of headwater stream length in the region. During both summer baseflow and snowmelt sampling, high-elevation streams were less acidic in 2017 than in 2010-2011. However, in 2017 the mean Al i concentration during snowmelt was 2.6 µmol L -1 , a value that reflected low to moderate toxicity to brook trout. Concentrations of Al i in 9 out of the 12 streams were above 1.5 µmol L -1 , which exceeds the value which impairs fish communities. Greater dilution of calcium (Ca 2+ ) concentrations than sulfate (SO 4 2- ) concentrations during snowmelt was a contributing factor to the more acidic stream water measured during snowmelt than summer baseflow. Comparison of 2018 ECASS and WASS snowmelt chemistry under the current low levels of acidic deposition indicated that the spatial pattern of acidification effects on stream chemistry is largely driven by inherent Ca 2+ availability tied to spatial variations in geologic factors that control acid buffering more effectively in the ECASS region than the WASS region. The higher degree of acidification in the WASS region than the ECASS region is likely to extend into the future as a result of the relatively high dissolved organic carbon (DOC) concentrations in the WASS. Pronounced increasing trends in DOC and similarly pronounced decreasing trends in Ca 2+ and nitrate (NO 3 - ) were observed in the streams of all three Boreas River watersheds. These strong increasing DOC trends occurred in streams during a period with little or no indication of further chemical recovery from acidic deposition. The strong DOC trends in Durgin Brook and Balsam Brook, which are streams that are unlikely to have ever experienced more than minimal acidification, suggest the need for further investigation to expand our understanding of the mechanisms behind the increasing DOC trends.

New York↗
USGS2018

Host-pathogen metapopulation dynamics suggest high elevation refugia for boreal toads

Emerging infectious diseases are an increasingly common threat to wildlife. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis ( Bd ), is an emerging infectious disease that has been linked to amphibian declines around the world. Few studies exist that explore amphibian- Bd dynamics at the landscape scale, limiting our ability to identify which factors are associated with variation in population susceptibility and to develop effective in situ disease management. Declines of boreal toads ( Anaxyrus boreas boreas ) in the Southern Rocky Mountains are largely attributed to chytridiomycosis but variation exists in local extinction of boreal toads across this metapopulation. Using a large-scale historic dataset, we explored several potential factors influencing disease dynamics in the boreal toad- Bd system: geographic isolation of populations, amphibian community richness, elevational differences, and habitat permanence. We found evidence that boreal toad extinction risk was lowest at high elevations where temperatures may be sub-optimal for Bd growth and where small boreal toad populations may be below the threshold needed for efficient pathogen transmission. In addition, boreal toads were more likely to recolonize high elevation sites after local extinction, again suggesting that high elevations may provide refuge from disease for boreal toads. We illustrate a modeling framework that will be useful to natural resource managers striving to make decisions in amphibian- Bd systems. Our data suggest that in the southern Rocky Mountains high elevation sites should be prioritized for conservation initiatives like reintroductions.

Ecological Applications↗