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Amphibian conservation efforts commonly assume populations are tied to waterbodies that collectively function as a metapopulation. This assumption is rarely evaluated, and there is a need to understand the degree of connectivity among patches to appropriately define, manage, and conserve biological populations. Our objectives were to quantify local persistence, colonization, and recruitment (metademographic rates) in relation to habitat attributes, evaluate the influence of the spatial arrangement of patches on landscape-scale population dynamics, and estimate the scale at which metapopulation dynamics are occurring for Oregon spotted frog (Rana pretiosa). We collected R. pretiosa detection/non-detection data and habitat information from 93 sites spread throughout the species’ extant range in Oregon, USA, 2010–2018. We developed a spatial multistate dynamic occupancy model to analyze these data. The proportion of sites occupied by R. pretiosa was relatively stable despite regular turnover in site occupancy. Connectivity was greatest when the distance between sites was within 4.49–7.70 km, and the results suggested that populations within 1 km are at the appropriate spatial scale for effective population management. Rana pretiosa metademographic rates were strongly tied to water availability, vegetation characteristics, and beaver dams. Our analysis provides critical information to identify the appropriate spatial scale for effective population management, estimates the distance at which populations are connected, and quantifies the effects of hypothesized threats to species at a landscape scale. We believe this model will prove to be useful to inform conservation and management strategies for multiple species.

Conboy Lake National Wildlife Refuge (CLNWR) in Washington State supports one of the largest remaining populations of federally listed Oregon Spotted Frogs (OSF; Rana pretiosa). Invasive American Bullfrogs (Lithobates catesbeianus [Rana catesbeiana]), implicated in amphibian declines, are also abundant at CLNWR. Owing to the likely negative effect of this aquatic invader on the highly aquatic OSF, bullfrog control strategies are needed. One method is to limit habitat used by bullfrogs while retaining or enhancing OSF habitat, but for such an approach to be implemented, the 2 species must partition habitat sufficiently. We used radiotelemetry to characterize OSF and bullfrog active-season and pre-overwintering habitat in the human-engineered ditch system at CLNWR. We tracked 12 OSF and 10 bullfrogs from mid-to-late summer, recorded data on frog location and habitat, and analyzed movement patterns, niche breadth, and spatial differences between species. Based on minimum convex polygons, bullfrogs overlapped extensively with OSF habitat space in the ditch system. During the active season, niche analyses also showed extensive overlap in the species' vegetation associations, with selected exceptions at the microhabitat scale. However, each species used distinct pre-overwintering habitats. The small differences in active-season microhabitats and pre-overwintering habitats, and our relatively narrow study conditions, create uncertainty about these species' habitat use in a broader context. Nonetheless, these results underscore the challenge of managing an invasive species that is both a habitat generalist and congener and expose the need for further research to guide management approaches to favor OSFs at CLNWR.

Land use alteration such as livestock grazing can affect water quality in habitats of at-risk wildlife species. Data from managed wetlands are needed to understand levels of exposure for aquatic life stages and monitor grazing-related changes afield. We quantified spatial and temporal variation in water quality in wetlands occupied by threatened Oregon spotted frog (Rana pretiosa) at Klamath Marsh National Wildlife Refuge in Oregon, United States (US). We used analyses for censored data to evaluate the importance of habitat type and grazing history in predicting concentrations of nutrients, turbidity, fecal indicator bacteria (FIB; total coliforms, Escherichia coli (E. coli), and enterococci), and estrogenicity, an indicator of estrogenic activity. Nutrients (orthophosphate and ammonia) and enterococci varied over time and space, while E. coli, total coliforms, turbidity, and estrogenicity were more strongly associated with local livestock grazing metrics. Turbidity was correlated with several grazing-related constituents and may be particularly useful for monitoring water quality in landscapes with livestock use. Concentrations of orthophosphate and estrogenicity were elevated at several sites relative to published health benchmarks, and their potential effects on Rana pretiosa warrant further investigation. Our data provided an initial assessment of potential exposure of amphibians to grazing-related constituents in western US wetlands. Increased monitoring of surface water quality and amphibian population status in combination with controlled laboratory toxicity studies could help inform future research and targeted management strategies for wetlands with both grazing and amphibians of conservation concern.

Many amphibians use multiple habitats across seasons. Information on seasonal habitat use, movement between seasonal habitat types, and habitats that may be particularly valuable is important to conservation and management. We used radio-telemetry to study late-season movement and habitat use by Oregon Spotted Frog (Rana pretiosa) at nine sites from four populations along the Cascade Mountains in Oregon. Movement rates declined with date and were the lowest at the end of tracking in December and January. Frogs across our sites used vegetated shallows in late summer and early fall. In fall, frogs used a range of habitat types, and at several sites moved to distinctive habitats such as springs, interstices in lava rock, and semi-terrestrial beaver channels. Distance between first and last tracking location was

Livestock grazing is an important land use in the western USA and can have positive or negative effects on amphibians. Columbia Spotted Frog (Rana luteiventris) often use ponds that provide water for cattle. We conducted a long-term manipulative study on US Forest Service land in northeastern Oregon to determine the effects of full and partial exclosures that limited cattle access to ponds used by frogs. We found weak evidence of a short-term increase in abundance that did not differ between full and partial exclosures and that diminished with continuing exclusion of cattle. The benefit of exclosures was small relative to the overall decline in breeding numbers that we documented. This suggests that some protection can provide a short-term boost to populations.

Biological invasion potential can be strongly influenced by abiotic factors such as temperature, water availability, and solar radiation. Invasive species that possess phenotypically plastic traits can mediate impacts from these stressors, but may be unable to recognize and respond to dangerous levels in a novel environment. Understanding potential constraints on appropriate trait responses induced by abiotic stressors can aid in the management and control of important invaders. Our study explored tolerance and plastic trait response to UV-B radiation in an invasive anuran, the American bullfrog (Lithobates catesbeianus Shaw, 1802). We experimentally quantified larval mortality rates and color change responses across two larval size classes. In a second experiment, we investigated the potential for a correlated color change and behavioral (refuge use) response in the small size class. We predicted that individuals would respond to stressful and potentially harmful UV-B exposure rates with darkening of body coloration, and when refuge was available, a correlated defense strategy utilizing both color change and refuge. We found an increase in larval mortality across both size classes at UV-B exposure rates typical to both low and high elevation aquatic breeding sites (1012µW/cm 2 and 20-24µW/cm 2 , respectively). Only bullfrog larvae in the small size class exhibited a darkening in body color when exposed to high UV-B treatments. Although this smaller size class did exhibit color plasticity, individuals did not correlate changes in body coloration with changes in refuge use. These results suggest ontogenetic differences (estimated by size class) in plastic color response to UV-B stress as well as constraints on behavioral use of refuge. These findings are important in understanding differences in bullfrog occupancy of breeding habitats across an elevational gradient, particularly in Oregon’s Cascade Mountain Range, where bullfrog distributions are currently limited at elevations above 1000m.

The success of restoration in attaining wildlife conservation goals can be strongly dependent on both site-scale and landscape-scale habitat characteristics, particularly for species with complex life cycles. Wetland management activities typically target plant communities, and bottom-up responses in higher trophic levels may be dependent on spatially explicit habitat use. We surveyed plant and amphibian assemblages at 26 sites enrolled in the Wetlands Reserve Program (WRP) in the Willamette Valley, Oregon to determine the relative influence of plant management, non-native species, and surrounding landscape on amphibian counts across multiple life history stages. Explanatory variables negatively associated with native anuran counts included percent invasive plant cover, non-native fish presence, invasive bullfrog counts, and area of urban land cover. In addition, native anurans were positively associated with WRP site age, suggesting that the benefits of restored wetlands may increase over time. This study emphasized the importance of adaptive approaches to maintaining diverse communities in restored habitats by considering impacts of synergistic stressors in a multi-invader context. Although invasive plant management provided indirect benefits to native amphibians, the most effective way to enhance native amphibian populations may be through eliminating the strong top-down forces exerted by non-native vertebrates.

Invasive species capable of recognizing potential predators may have increased establishment rates in novel environments. Individuals may retain historical predator recognition and invoke innate responses in the presence of taxonomically or ecologically similar predators, generalize antipredator responses, or learn to avoid risky species in novel environments. Invasive amphibians in aquatic environments often use chemical cues to assess predation risk and learn to avoid novel predators via direct experience and/or associated chemical cues. Ontogeny may also influence recognition; experience with predators may need to occur at certain developmental stages for individuals to respond correctly. We tested predator recognition in invasive American bullfrog (Lithobates catesbeianus) tadpoles that varied in experience with fish predators at the population and individual scale. We found that bullfrog tadpoles responded to a historical predator, largemouth bass (Micropterus salmoides), only if the population was locally sympatric with largemouth bass. Individuals from a population that did not co-occur with largemouth bass did not increase refuge use in response to either largemouth bass chemical cues alone or chemical cues with diet cues (largemouth bass fed bullfrog tadpoles). To test whether this behavioral response was generalized across fish predators, we exposed tadpoles to rainbow trout (Oncorhynchus mykiss) and found that tadpoles could not recognize this novel predator regardless of co-occurrence with other fish species. These results suggest that environment may be more important for predator recognition than evolutionary history for this invasive species, and individuals do not retain predator recognition or generalize across fish predators.

With the ongoing crisis of biodiversity loss and limited resources for conservation, the concept of biodiversity hotspots has been useful in determining conservation priority areas. However, there has been limited research into how temporal variability in biodiversity may influence conservation area prioritization. To address this information gap, we present an approach to evaluate the temporal consistency of biodiversity hotspots in large marine ecosystems. Using a large scale, public monitoring dataset collected over an eight year period off the US Pacific Coast, we developed a methodological approach for avoiding biases associated with hotspot delineation. We aggregated benthic fish species data from research trawls and calculated mean hotspot thresholds for fish species richness and Shannon’s diversity indices over the eight year dataset. We used a spatial frequency distribution method to assign hotspot designations to the grid cells annually. We found no areas containing consistently high biodiversity through the entire study period based on the mean thresholds, and no grid cell was designated as a hotspot for greater than 50% of the time-series. To test if our approach was sensitive to sampling effort and the geographic extent of the survey, we followed a similar routine for the northern region of the survey area. Our finding of low consistency in benthic fish biodiversity hotspots over time was upheld, regardless of biodiversity metric used, whether thresholds were calculated per year or across all years, or the spatial extent for which we calculated thresholds and identified hotspots. Our results suggest that static measures of benthic fish biodiversity off the US West Coast are insufficient for identification of hotspots and that long-term data are required to appropriately identify patterns of high temporal variability in biodiversity for these highly mobile taxa. Given that ecological communities are responding to a changing climate and other environmental perturbations, our work highlights the need for scientists and conservation managers to consider both spatial and temporal dynamics when designating biodiversity hotspots.

The salamander chytrid fungus (Batrachochytrium salamandrivorans [Bsal]) is causing massive mortality of salamanders in Europe. The potential for spread via international trade into North America and the high diversity of salamanders has catalyzed concern about Bsal in the U.S. Surveillance programs for invading pathogens must initially meet challenges that include low rates of occurrence on the landscape, low prevalence at a site, and imperfect detection of the diagnostic tests. We implemented a large-scale survey to determine if Bsal was present in North America designed to target taxa and localities where Bsal was determined highest risk to be present based on species susceptibility and geography. Our analysis included a Bayesian model to estimate the probability of occurrence of Bsal given our prior knowledge of the occurrence and prevalence of the pathogen. We failed to detect Bsal in any of 11,189 samples from 594 sites in 223 counties within 35 U.S. states and one site in Mexico. Our modeling indicates that Bsal is highly unlikely to occur within wild amphibians in the U.S. and suggests that the best proactive response is to continue mitigation efforts against the introduction and establishment of the disease and to develop plans to reduce impacts should Bsal establish.