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Chytridiomycosis is an amphibian disease linked with population declines worldwide, yet there is little information about its effects on the demography of infected populations. We used capture-recapture data from two infected populations and one uninfected population of boreal toads (Bufo boreas) in the Rocky Mountains, U.S.A. to examine a priori hypotheses about the effect of the amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd) on survival probability (Φ) and population growth rate (). Bd-positive toads had lower average annual Φ than Bd-negative individuals at sites where Bd was detected suggesting that chytridiomycosis may reduce survival by 31-42% in wild boreal toads. Bd-negative toads at infected sites had comparable survival probabilities as Bd-negative toads at the uninfected site, further supporting observed differences. Model results indicated weak evidence that environmental covariates (particularly cold temperatures during the breeding season) influenced toad survival. The diseased populations were declining by 5 - 7% per year over the 6 years of this study whereas the Bd-free population had comparatively stable ( ≈ 1) population growth. Our data suggest that Bd is a low-level chronic mortality factor in these toad populations rather than an acute factor causing rapid population declines. These results show how some amphibian populations may be coexisting with the amphibian chytrid fungus and highlight the importance of quantitative assessments of survival in wildlife populations challenged with disease.

Aim
The introduction of non-native species into aquatic environments has been linked with local extinctions and altered distributions of native species. We investigated the effect of non-native salmonids on the occupancy of two native amphibians, the long-toed salamander (Ambystoma macrodactylum) and Columbia spotted frog (Rana luteiventris), across three spatial scales: water bodies, small catchments and large catchments.

Location
Mountain lakes at >1500 m elevation were surveyed across the northern Rocky Mountains, USA.

Methods
We surveyed 2267 water bodies for amphibian occupancy (based on evidence of reproduction) and fish presence between 1986 and 2002 and modelled the probability of amphibian occupancy at each spatial scale in relation to habitat availability and quality and fish presence.

Results
After accounting for habitat features, we estimated that A. macrodactylum was 2.3 times more likely to breed in fishless water bodies than in water bodies with fish. Ambystoma macrodactylum also was more likely to occupy small catchments where none of the water bodies contained fish than in catchments where at least one water body contained fish. However, the probability of salamander occupancy in small catchments was also influenced by habitat availability (i.e. the number of water bodies within a catchment) and suitability of remaining fishless water bodies. We found no relationship between fish presence and salamander occupancy at the large-catchment scale, probably because of increased habitat availability. In contrast to A. macrodactylum, we found no relationship between fish presence and R. luteiventris occupancy at any scale.

Main conclusions
Our results suggest that the negative effects of non-native salmonids can extend beyond the boundaries of individual water bodies and increase A. macrodactylum extinction risk at landscape scales. We suspect that niche overlap between non-native fish and A. macrodactylum at higher elevations in the northern Rocky Mountains may lead to extinction in catchments with limited suitable habitat.

Information on amphibian responses to fire and fuel reduction practices is critically needed due to potential declines of species and the prevalence of new, more intensive fire management practices in North American forests. The goals of this review are to summarize the known and potential effects of fire and fuels management on amphibians and their aquatic habitats, and to identify information gaps to help direct future scientific research. Amphibians as a group are taxonomically and ecologically diverse; in turn, responses to fire and associated habitat alteration are expected to vary widely among species and among geographic regions. Available data suggest that amphibian responses to fire are spatially and temporally variable and incompletely understood. Much of the limited research has addressed short-term (1–3 years) effects of prescribed fire on terrestrial life stages of amphibians in the southeastern United States. Information on the long-term negative effects of fire on amphibians and the importance of fire for maintaining amphibian communities is sparse for the majority of taxa in North America. Given the size and severity of recent wildland fires and the national effort to reduce fuels on federal lands, future studies are needed to examine the effects of these landscape disturbances on amphibians. We encourage studies to address population-level responses of amphibians to fire by examining how different life stages are affected by changes in aquatic, riparian, and upland habitats. Research designs need to be credible and provide information that is relevant for fire managers and those responsible for assessing the potential effects of various fuel reduction alternatives on rare, sensitive, and endangered amphibian species.

We assessed the diversity and phylogeny of Saprolegniaceae on amphibian eggs from the Pacific Northwest, with particular focus on Saprolegnia ferax, a species implicated in high egg mortality. We identified isolates from eggs of six amphibians with the internal transcribed spacer (ITS) and 5.8S gene regions and BLAST of the GenBank database. We identified 68 sequences as Saprolegniaceae and 43 sequences as true fungi from at least nine genera. Our phylogenetic analysis of the Saprolegniaceae included isolates within the genera Saprolegnia, Achlya and Leptolegnia. Our phylogeny grouped S. semihypogyna with Achlya rather than with the Saprolegnia reference sequences. We found only one isolate that grouped closely with S. ferax, and this came from a hatchery-raised salmon (Idaho) that we sampled opportunistically. We had representatives of 7–12 species and three genera of Saprolegniaceae on our amphibian eggs. Further work on the ecological roles of different species of Saprolegniaceae is needed to clarify their potential importance in amphibian egg mortality and potential links to population declines.

A GIS facilitates the organization and visualization of data, and can give biologists a better understanding of their landscapes, as well as identify data gaps. The objective of this paper was to introduce how to use a GIS to design and undertake amphibian surveys. Using Yellowstone National Park as an example, we used GIS to select sampling areas using randomized techniques, and to select watersheds within these areas. Within these watersheds, we then used GIS to visualize potential amphibian pond breeding habitats for field sampling. Results from this sampling effort were then organized as a GIS layer depicting the distribution and abundance of amphibian breeding populations. The GIS layer created from these data has become the baseline for comparisons with future surveys.

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.