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Non?native fish and bullfrogs (Lithobates catesbeianus) are frequently cited as contributing to the decline of ranid frogs in the western United States, so we hypothesized that non?native species, habitat, or a combination of these relate to the probability of local extinction for northern red?legged frogs (Rana aurora) in Oregon, USA. We also hypothesized that the probability of colonization relates to land use, wetland size, or riparian forest. In a 5?yr study, we found no support for an effect of non?native species on northern red?legged frogs. Instead, probability of local extinction decreased with the extent of emergent vegetation and riparian forest. This finding suggests that managers consider the role of habitat when confronting non?native species problems.

We examined diet of introduced Bullfrogs (Rana catesbeiana) and three native frog species (R. limnocharis, R. nigromaculata and Bufo bufo gargarizans) co-occurring at a group of ponds on Daishan Island, east of China, to gain insight into the nature of potential interactions between Bullfrogs and native frog species. For postmetamorphic Bullfrogs, aquatic prey items dominated volumetrically. Prey size, diet volume and volumetric percentage of native frogs in diet increased with Bullfrog body size. The number and volumetric percentage of native frogs in the diet were not different for female and male Bullfrogs, and both were higher for adults than for juveniles. Diet overlap between males and juveniles was higher than that between males and females and between females and juveniles. Diet overlap with each native frog species of male Bullfrogs was lower than that of female Bullfrogs and juvenile Bullfrogs. We did not exam effects of Bullfrogs on native frogs but our results suggest that the primary threat posed by juvenile Bullfrogs to native frogs on Daishan Island is competition for food while the primary threat posed by male Bullfrogs is direct predation. Female Bullfrogs may threaten native frogs by both competition and predation. These differences among Bullfrog groups may be attributed to differences in body size and microhabitat use.

Revisiting historical amphibian sites can provide a relatively fast assessment of amphibian status in a region. Between 2000 and 2003 we repeatedly surveyed historically documented sites for two species of concern in the northern Great Basin: the western toad (Bufo boreas), and the Columbia spotted frog (Rana luteiventris). Both of these species have experienced population declines in other parts of their ranges but their status was relatively unknown in our study area. We estimate that B. boreas occupies 49.5% (34.1% - 65.0%) of 34 historical sites and that R. luteiventris occupies 52.9% (43.5% - 62.3%) of its 30 historical sites. B. boreas was more likely to be detected at human-altered sites while R. luteiventris was more likely to be detected at sites that were deeper than other sites in our study. B. boreas was detected at three of 41 (7.3%) potential sites (located near historic sites) while R. luteiventris was detected at six of 16 (37.5%). At 187 randomly selected sites, B. boreas was detected at one and R. luteiventris at three sites. Given that the number of historical sites available for resurveys was small, these results should be interpreted with caution. Moreover, a species can shift its distribution away from historical sites due to habitat succession or metapopulation dynamics without necessarily declining. We suggest that there is sufficient evidence to conclude that B. boreas and R. luteiventris have declined in and around the northern Great Basin. However, relatively high occupancy of Potential Sites by R. luteiventris suggests they may not have declined as much as B. boreas in the region we surveyed.

In summer 2007, we hand captured individual amphibians in Denmark and sampled them for B. dendrobatidis. We found B. dendrobatidis on individuals from both species sampled and at 2 of the 4 study areas we examined. One of the positive results was for an adult of Rana kl. esculenta captured in Vestamager. The other positive result was for a juvenile of Rana temporaria captured in Egense.

Chytridiomycosis (infection by the fungus Batrachochytrium dendrobatidis) has been associated with amphibian declines in at least four continents. We report results of disease screens from 210 pond-breeding amphibians from 37 field sites in Oregon and Washington. We detected B. dendrobatidis on 28% of sampled amphibians, and we found >=1 detection of B. dendrobatidis from 43% of sites. Four of seven species tested positive for B. dendrobatidis, including the Northern Red-Legged Frog (Rana aurora), Columbia Spotted Frog (Rana luteiventris), and Oregon Spotted Frog (Rana pretiosa). We also detected B. dendrobatidis in nonnative American Bullfrogs (Rana catesbeiana) from six sites in western and central Oregon. Our study and other recently published findings suggest that B. dendrobatidis has few geographic and host taxa limitations among North American anurans. Further research on virulence, transmissibility, persistence, and interactions with other stressors is needed to assess the potential impact of R. dendrobatidis on Pacific Northwestern amphibians.

The pathogen Batrachochytrium dendrobatidis (Bd) has been associated with amphibian declines in multiple continents, including western North America. We investigated Bd prevalence in Oregon spotted frog (Rana pretiosa), a species that has declined across its range in the Pacific Northwest. Polymerase Chain Reaction analysis of skin swabs indicated that Bd was prevalent within populations (420 of 617 juvenile and adults) and widespread among populations (36 of 36 sites) where we sampled R. pretiosa in Oregon and Washington. We rarely detected Bd in R. pretiosa larvae (2 of 72). Prevalence of Bd in post-metamorphic R. pretiosa was inversely related to frog size. We found support for an interactive effect of elevation and sampling date on Bd: prevalence of Bd generally increased with date but this effect was more pronounced at lower elevations. We also found evidence that the body condition of juvenile R. pretiosa with Bd decreased after their first winter. Our data indicate that some Oregon spotted frog populations are currently persisting with relatively high Bd prevalence, but the risk posed by Bd is unknown.

Several western ranid frogs possess a unique strategy of breeding communally over a short temporal window and reusing oviposition sites between years. However, little is published on the characteristics of oviposition sites selected by these explosive breeders. The Columbia spotted frog (Rana luteiventris) is native to northwestern North America and is of conservation concern in the southern portions of its range. As part of a study examining relationships between livestock grazing and R. luteiventris habitat, we assessed characteristics of the species’ oviposition sites in 25 fishless ponds in northeastern Oregon. Oviposition sites were generally in shallow water (25 cm) close to shore and tended to be in the northeastern portion of ponds. Oviposition sites were found more frequently over heavily vegetated substrates and in areas of less substrate slope and shade than random points in littoral zones. We did not quantify temperature differences within ponds but the patterns we documented are consistent with preferential use of warmer microhabitats for oviposition.

We compared behavioral responses of three Pacific Northwest anuran larvae from different hydroperiods to water born cues of native and introduced predators. Two native anurans (Pacific treefrog, Pseudacris regilla and northern red-legged frog, Rana aurora aurora) and introduced bullfrogs (Rana catesbeiana) responded to water conditioned by native redside shiners (Richardsonius balteatus) by increasing refuge use. The two native anuran larvae differed in their response to introduced predator cues. Rana a. aurora, which occur in temporary and permanent waters, responded to both introduced bluegill sunfish (Lepomis macrochirus) and introduced crayfish (Procambarus clarkii). Pseudacris regilla, which occur primarily in temporary ponds, did not respond to water born cues from either introduced predator. The broader responses of R. a. aurora may indicate greater behavioral plasticity or more exposure to novel predators than experienced by P. regilla. Larvae of introduced R. catesbeiana responded strongly to cues from two fish native to the Pacific northwest, but did not alter behavior in response to any of five potential predators with which they co-occur in their native range. Fish that occur with R. catesbeiana in their native range generally find bullfrog tadpoles unpalatable. This pattern suggests that bullfrog larvae can recognize cues of novel predators that may find them palatable, which could contribute to their success as an invasive species in the region.

The distribution of the Oregon Spotted Frog (Rana pretiosa) has shrunk markedly and more than 2/3 of known populations are located along the Cascade Range in central Oregon. Despite the conservation concern, little is known about how habitat attributes and stressors such as invasive species influence R. pretiosa populations. We used egg mass counts to study R. pretiosa habitat relationships at oviposition sites and breeding ponds. Oviposition sites were in shallow water above gradually sloping substrates that supported moderate or dense herbaceous vegetation. Sixty-one per cent of occupied breeding ponds had fewer than 20 egg masses. We found strong support for two predictors of egg mass count: positive effect of other R. pretiosa breeding sites nearby and a negative effect of non-native fish having access to preferred R. pretiosa overwintering habitat. We found moderate support for effects of emergent and submergent vegetation coverage (positive) and of ponds being located in the Klamath Basin (negative). Maintaining and restoring overwintering habitats that are free of non-native game fish is likely to benefit R. pretiosa. Further work on movement ecology is needed to improve our understanding of habitat connectivity and the effects of site isolation on the persistence of R. pretiosa in Oregon.

Introduced American bullfrogs (Rana catesbeiana) have become widely established in the Pacific Northwest over the last century, and are thought to be an important predator of native amphibians throughout the western USA. The northern red-legged frog (Rana aurora aurora) and Oregon spotted frog (Rana pretiosa) historically co-occurred in portions of the Pacific Northwest now invaded by R. catesbeiana, but R. pretiosa has declined more severely than R. a. aurora. We investigated whether microhabitat and behavioral differences that facilitate sympatric coexistence of the natives predict which species is more susceptible to predation by introduced R. catesbeiana. Our laboratory experiments demonstrate that R. catesbeiana adults prefer aquatic microhabitats, R. pretiosa juveniles are more aquatic than R. a. aurora, and that adult R. catesbeiana consume more R. pretiosa than R. a. aurora juveniles. Mean and maximum jump distances of R. pretiosa were shorter than equally-sized R. a. aurora, and the difference between these two species increased with larger frog sizes. Our examination of field survey data indicates that R. pretiosa co-occur with R. catesbeiana less frequently than R. a. aurora. We conclude that R. catesbeiana is a greater threat to survival of R. pretiosa than to R. a. aurora, and suggest that microhabitat use and escape abilities of native ranid frogs may be linked to this asymmetrical effect. Analysis of behavioral and microhabitat differences among related native species may be a useful tool in predicting the effects of introduced predators on amphibians, and can assist in developing conservation priorities for these species.

Despite concern about the conservation status of amphibians in western North America, few field studies have documented occurrence patterns of amphibians relative to potential stressors. We surveyed wetland fauna in Oregon’s Willamette Valley and used an information theoretic approach (AIC) to rank the associations between native amphibian breeding occurrence and wetland characteristics, non-native aquatic predators, and landscape characteristics in a mixed urban-agricultural landscape. Best predictors varied among the 5 native amphibians, and were generally consistent with life history differences. Pacific tree frog (Pseudacris regilla) and long-toed salamander (Ambystoma macrodactylum) occurrence was best predicted by the absence of non-native fish. Northern red-legged frog (Rana aurora) and northwestern salamander (Ambystoma gracile) were most strongly related to wetland vegetative characteristics. The occurrence of rough-skinned newts (Taricha granulosa), a migratory species that makes extensive use of terrestrial habitats, was best predicted by greater forest cover within 1 km. The absence of non-native fish was a strong predictor of occurrence for 4 of the 5 native species. In contrast, amphibians were not strongly related to native fish presence. We found little evidence supporting negative effects of the presence of breeding populations of bullfrog (Rana catesbeiana) on any native species. Only the 2 Ambystoma salamanders were associated with wetland permanence. Northwestern salamanders (which usually have a multi-year larval stage) were associated with permanent waters, while long-toed salamanders were associated with temporary wetlands. Although all the species make some use of upland habitats, only one (rough-skinned newt) was strongly associated with surrounding landscape conditions. Instead, our analysis suggests within wetland characteristics best predict amphibian occurrence in this region. We recommend that wetland preservation and mitigation efforts concentrate on sites lacking non-native fish for the conservation of native amphibians in the Willamette Valley and other western lowlands.

A species account for Rana cascadae.

Few ecologists would dispute that exposure to high levels of ultraviolet-B radiation (UV-B) is detrimental to organisms. It is well established that UV-B has been a critical factor shaping the physiology (Blum et al. 1949, Hansson 2000), behavior (Pennington and Emlet 1986, van de Mortel and Buttemer 1998), and distribution (Williamson et al. 2001, Leavitt et al. 2003) of many aquatic species. Recently, increasing UV-B caused by stratospheric ozone depletion has stimulated much research on the UV-B sensitivity of a wide variety of taxa, and has been found to cause direct mortality (Calkins and Thordardottir 1980, reviewed by Siebeck et al. 1994), elevate developmental abnormalities (Ankley et al. 2002), increase susceptibility to disease (Little and Fabacher 1994, Kiesecker and Blaustein 1995), and change the strength of species interactions (Sommaruga 2003). Increasing levels of UV-B have also been invoked as an explanation for the decline of some amphibian species, and support for this hypothesis has been extrapolated from many laboratory experiments and field studies at individual sites that indicate ambient or enhanced levels of UV-B can increase mortality of embryos and larvae (but see Licht 2003). This has been an especially attractive hypothesis for amphibian populations in alpine environments where direct anthropogenic impacts such as habitat modification are limited and ambient levels of UV-B are high (Blaustein and Wake 1990, Blaustein et al. 1994, Alford and Richards 1999). However, for all the attention UV-B has received in the context of declining amphibian populations, there is little evidence linking the physiological sensitivity of individuals to actual population dynamics (Licht 2003).

Increased exposure to ultraviolet-B (UV-B) radiation has been proposed as a major environmental stressor leading to global amphibian declines. Prior experimental evidence from the US Pacific Northwest (PNW) has established the embryonic sensitivity of at least 4 amphibian species to UV-B and has been central to the amphibian decline literature. However, these results have not been expanded to address population-scale effects and natural landscape variation in UV-B transparency of water at amphibian breeding sites; necessary links to assess the importance of UV-B for amphibian declines. We quantified the UV-B transparency of 136 potential amphibian breeding sites to establish the pattern of UV-B exposure across two montane regions in the PNW. Our data suggest that 85% of sites are naturally protected by dissolved organic matter (DOM) in pond water, and that only a fraction of breeding sites are likely to experience UV-B intensities exceeding levels associated with elevated egg mortality. Thus, the spectral characteristics of natural waters mediate the physiological effects of UV-B on amphibian eggs in all but the clearest sites. These data imply that UV-B is unlikely to cause broad amphibian declines across the landscape of the American Northwest.

Most research to assess amphibian declines has focused on local-scale projects on one or a few species. The Amphibian Research and Monitoring Initiative (ARMI) is a national program in the United States mandated by congressional directive and implemented by the U.S. Department of the Interior (specifically the U.S. Geological Survey, USGS). Program goals are to monitor changes in populations of amphibians across U.S. Department of the Interior lands and to address research questions related to amphibian declines using a hierarchical framework of base-, mid- and apex-level monitoring sites. ARMI is currently monitoring 83 amphibian species (29% of species in the U.S.) at mid- and apex-level areas. We chart the progress of this 5-year-old program and provide an example of mid-level monitoring from 1 of the 7 ARMI regions.

Age distribution information can be an important part of understanding the biology of any population. Age estimates collected from the annual growth rings found in tooth and bone cross sections, often referred to as Lines of Arrested Growth (LAGs), have been used in the study of various animals. In this manual we describe in detail all necessary steps required to obtain estimates of age from anuran bone cross sections via skeletochronological assessment. We include comprehensive descriptions of how to fix and decalcify toe specimens (phalanges), process a phalange prior to embedding, embed the phalange in paraffin, section the phalange using a microtome, stain and mount the cross sections of the phalange and read the LAGs to obtain age estimates.

Tailed frogs (Ascaphus spp.) oviposit in cryptic locations in streams of the Pacific Northwest and Rocky Mountains. This aspect of their life history has restricted our understanding of their reproductive ecology. The recent split of A. montanus in the Rocky Mountains from A. truei was based on molecular differentiation, and comparisons of their ecology are limited. Our objectives were to provide a range-wide summary of information on Ascaphus oviposition,compare some aspects of the reproductive ecology of the 2 species, and examine geographic variation in their reproductive traits. Reproductive ecology of the 2 species differed. Ascaphus truei had smaller clutches, oviposited later in the summer, and had a longer duration of oviposition than A. montanus. A greater number of communal oviposition sites were attributed to A. montanus. These ecological differences support the recent taxonomic revision of Ascaphus and suggest that different management strategies may be necessary for each species where conservation is a priority.

Many declines of amphibian populations have been associated with chytridiomycosis, a disease caused by the aquatic fungus Batrachochytrium dendrobatidis (Bd). Despite the relatively high prevalence of chytridiomycosis in stream amphibians globally, most surveys in North America have focused primarily on wetland-associated species, which are frequently infected. To better understand the distribution and prevalence of Bd in headwater amphibian communities, we sampled 452 tailed frogs (Ascaphus truei and Ascaphus montanus) and 304 stream salamanders (seven species in the Dicamptodontidae and Plethodontidae) for Bd in 38, first- to third-order streams in five montane areas across the United States. We tested for presence of Bd by using PCR on skin swabs from salamanders and metamorphosed tailed frogs or the oral disc of frog larvae. We detected Bd on only seven individuals (0.93%) in four streams. Based on our study and results from five other studies that have sampled headwater- or seep-associated amphibians in the United States, Bd has been detected on only 3% of 1,322 individuals from 21 species. These results differ strongly from surveys in Central America and Australia, where Bd is more prevalent on stream-breeding species, as well as results from wetland-associated anurans in the same regions of the United States that we sampled. Differences in the prevalence of Bd between stream- and wetland-associated amphibians in the United States may be related to species-specific variation in susceptibility to chytridiomycosis or habitat differences.

The dynamic geological and climatic history of northwestern North America has made it a focal region for phylogeography. We conducted a range-wide phylogeographic analysis of the spotted frog complex (Rana luteiventris and R. pretiosa) across its range in northwestern North America to understand its evolutionary history and the distribution of clades to guide conservation of R. pretiosa and Great Basin R. luteiventris, both candidates for listing under the U.S. Endangered Species Act. Mitochondrial DNA sequence data from a segment of the cytochrome b gene were obtained from 308 R. luteiventris and R. pretiosa from 98 sites. Phylogenetic analysis revealed one main R. pretiosa clade and 3 main R. luteiventris clades, 2 of which overlapped in southeastern Oregon. The 3 R. luteiventris clades were separated from each other by high levels of sequence divergence (average of 4.75–4.97%). Two divergent clades were also uncovered within the Great Basin. Low genetic variation in R. pretiosa and the southeastern Oregon clade of R. luteiventris highlights their vulnerability to extinction.

Ultraviolet-B radiation (UV-B, 280 nm to 320 nm wavelengths) doses were estimated for 1024 wetlands in six National Parks; Acadia (Acadia), Glacier (Glacier), Great Smoky Mountains (Smoky), Olympic (Olympic), Rocky Mountain (Rocky), and Sequoia/Kings Canyon (Sequoia/Kings). Estimates were made using ground-based UV-B data (Brewer spectrophotometers), solar radiation models, GIS tools, field characterization of vegetative features, and quantification of DOC concentration and spectral absorbance. UV-B dose estimates were made for the summer solstice, at a depth of 1 cm in each wetland. Mean dose across all wetlands and parks was 19.3 Whr*m-2 (range of 3.4 to 32.1 Whr*m-2). Mean dose was lowest in Acadia (13.7 Whr*m-2) and highest in Rocky (24.4 Whr*m-2). Doses were significantly different among all parks. These wetland doses correspond to UV-B flux of 125.0 W*cm-2 (range of 21.4 to 194.7 W*cm-2) based on a day length, averaged among all parks, of 15.5 hr. Dissolved organic carbon (DOC), a key determinant of subsurface UV-B flux, ranged from 0.6 (analytical detection limit) to 36.7 mg carbon * l-1 over all wetlands and parks, and reduced potential maximal UV-B doses at 1 cm depth by 1 to 87 %. DOC concentration, as well as its effect on dose, was lowest in Sequoia/Kings, and highest in Acadia (DOC was equivalent in Acadia, Glacier, and Rocky). Landscape reduction of potential maximal UV-B doses ranged from zero to 77 %, and was lowest in Sequoia/Kings. These regional differences in UV-B wetland dose illustrate the importance of considering all aspects of exposure in evaluating the potential impact of UV-B on aquatic organisms.