False positive errors are a significant component of many ecological data sets, which in combination with false negative errors, can lead to severe biases in conclusions about ecological systems. We present results of a field experiment where observers recorded observations for known combinations of electronically broadcast calling anurans under conditions mimicking field surveys to determine species occurrence. Our objectives were to characterize false positive error probabilities for auditory methods based on a large number of observers, to determine if targeted instruction could be used to reduce false positive error rates, and to establish useful predictors of among-observer and among-species differences in error rates. We recruited 31 observers, ranging in abilities from novice to expert, that recorded detections for 12 species during 180 calling trials (66,960 total observations). All observers made multiple false positive errors and on average 8.1% of recorded detections in the experiment were false positive errors. Additional instruction had only minor effects on error rates. After instruction, false positive error probabilities decreased by 16% for treatment individuals compared to controls with broad confidence interval overlap of 0 (95% CI: -46 to 30%). This coincided with an increase in false negative errors due to the treatment (26%; -3 to 61%). Differences among observers in false positive and in false negative error rates were best predicted by scores from an online test and a self-assessment of observer ability completed prior to the field experiment. In contrast, years of experience conducting call surveys was a weak predictor of error rates. False positive errors were also more common for species that were played more frequently, but were not related to the dominant spectral frequency of the call. Our results corroborate other work that demonstrates false positives are a significant component of species occurrence data collected by auditory methods. Instructing observers to only report detections they are completely certain are correct is not sufficient to eliminate errors. As a result, analytical methods that account for false positive errors will be needed, and independent testing of observer ability is a useful predictor for among-observer variation in observation error rates.

Monitoring of natural resources is crucial to ecosystem conservation, and yet it can pose many challenges. We developed an amphibian monitoring program as a means for examining ecological conditions in Yellowstone and Grand Teton National Parks. Annual surveys for amphibian breeding occupancy were conducted over a 4-yr period (2006 – 2009) at two scales: catchments (portions of watersheds) and individual wetland sites. Catchments were selected in a stratified random sample with habitat quality and ease of access serving as strata. All known wetland sites with suitable habitat were surveyed within selected catchments. Changes in breeding occurrence of tiger salamanders, boreal chorus frogs and Columbia-spotted frogs were assessed using multi-season occupancy estimation. Numerous a priori models were considered within an information theoretic framework including those with catchment and site-level covariates. Habitat quality was the most important predictor of occupancy. Boreal chorus frogs demonstrated the greatest change (increase) in breeding occupancy at the catchment level. Tiger salamander breeding occurrence increased slightly and Columbia-spotted frogs decreased slightly over the 4-yr period. Larger changes for all 3 species were detected at the finer site-level scale. Use of covariates (e.g., connectivity of sites) offered improvements over simpler models, and may improve understanding of the dynamic processes occurring among wetlands within this ecosystem. Our results suggest monitoring occupancy at two spatial scales within large study areas such as ours is feasible and informative.

Sensitivity analysis is a useful tool for the study of ecological models that has many potential applications for patch occupancy modeling. I use the rich foundation of existing methods for Markov chain models to demonstrate new methods for sensitivity analysis of the equilibrium state dynamics of occupancy models. Estimates from three previous studies are used to illustrate the utility of the sensitivity calculations: a joint occupancy model for a prey species, its predators, and habitat used by both; occurrence dynamics from a well-known metapopulation study of three butterfly species (Hanski 1994); and golden eagle occupancy and reproductive dynamics (Martin et al. 2009a). I show how to deal efficiently with multistate models and how to calculate sensitivities involving derived state variables and lower level parameters. In addition, I extend methods to incorporate environmental variation by allowing for spatial and temporal variability in transition probabilities. The approach used here is concise and general and can fully account for environmental variability in transition parameters. The methods can be used to improve inferences in occupancy studies by quantifying the effects of underlying parameters, aiding prediction of future system states, and identifying priorities for sampling effort.

Studies of the distribution of elusive forest wildlife have suffered from the confounding of true presence with the uncertainty of detection. Occupancy modeling, which incorporates probabilities of species detection conditional on presence, is an emerging approach for reducing observation bias. However, the current likelihood modeling framework is restrictive for handling unexplained sources of variation in the response that may occur when there are dependence structures such as smaller sampling units that are nested within larger sampling units. We used multilevel Bayesian occupancy modeling to handle dependence structures and partition sources of variation in occupancy of sites by terrestrial salamanders (family Plethodontidae) within and surrounding an earlier wildfire in western Oregon, USA. Comparison of model fit favored a spatial N-mixture model that accounted for variation in salamander abundance over models that were based on binary detection/non-detection data. Though catch per unit effort was higher in burned areas than unburned, there was strong support that this pattern was due to a higher probability of capture for individuals in burned plots. Within the burn the odds of capturing an individual given it was present were 2.06 times the odds outside the burn, reflecting reduced complexity of ground cover in the burn. There was weak support that true occupancy was lower within the burned area. While the odds of occupancy in the burn were 0.49 times the odds outside the burn among the five species, the magnitude of variation attributed to the burn was small in comparison to variation attributed to other landscape variables and to unexplained, spatially autocorrelated random variation. While ordinary occupancy models may separate the biological pattern of interest from variation in detection probability when all sources of variation are known, the addition of random effects structures for unexplained sources of variation in occupancy and detection probability may often more appropriately represent levels of uncertainty.

Prevalence of the pathogen Batrachochytrium dendrobatidis (Bd), implicated in amphibian population declines worldwide, is associated with habitat moisture and temperature, but few studies have varied these factors and measured the response to infection in amphibian hosts. We evaluated how varying humidity, contact with water, and temperature affected the manifestation of chytridiomycosis in boreal toads Anaxyrus (Bufo) boreas boreas and how prior exposure to Bd affects the likelihood of survival after re-exposure, such as may occur seasonally in long-lived species. Humidity did not affect survival or the degree of Bd infection, but a longer time in contact with water increased the likelihood of mortality. After exposure to ~10^6 Bd zoospores, all toads in continuous contact with water died within 30 d. Moreover, Bd-exposed toads that were disease-free after 64 d under dry conditions, developed lethal chytridiomycosis within 70 d of transfer to wet conditions. Toads in unheated aquaria (mean = 15°C) survived less than 48 d, while those in moderately heated aquaria (mean = 18°C) survived 115 d post-exposure and exhibited behavioral fever, selecting warmer sites across a temperature gradient. We also found benefits of prior Bd infection: previously exposed toads survived 3 times longer than Bd-naïve toads after re-exposure to 106 zoospores (89 vs. 30 d), but only when dry microenvironments were available. This study illustrates how the outcome of Bd infection in boreal toads is environmentally dependent: when continuously wet, high reinfection rates may overwhelm defenses, but periodic drying, moderate warming, and previous infection may allow infected toads to extend their survival.

1. Altered global climates in the 21st century pose serious threats for biological systems and practical actions are needed to mount a response for species at risk.<br />
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2. We identify management actions from across the world and from diverse disciplines that are applicable to minimizing loss of amphibian biodiversity under climate change. Actions were grouped under three thematic areas of intervention: (i) installation of microclimate and microhabitat refuges; (ii) enhancement and restoration of breeding sites; and (iii) manipulation of hydroperiod or water levels at breeding sites.<br />
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3. Synthesis and applications. There are currently few meaningful management actions that will tangibly impact the pervasive threat of climate change on amphibians. A host of potentially useful but poorly tested actions could be incorporated into local or regional management plans, programmes and activities for amphibians. Examples include: installation of irrigation sprayers to manipulate water potentials at breeding sites; retention or supplementation of natural and artificial shelters (e.g. logs, cover boards) to reduce desiccation and thermal stress; manipulation of canopy cover over ponds to reduce water temperature; and, creation of hydrologoically diverse wetland habitats capable of supporting larval development under variable rainfall regimes. We encourage researchers and managers to design, test and scale up new initiatives to respond to this emerging crisis.

The ability to predict amphibian breeding across landscapes is important for informing land management decisions and helping biologists better understand and remediate factors contributing to declines in amphibian populations. We built geospatial models of likely breeding habitats for each of four amphibian species that breed in Yellowstone National Park (YNP). We used field data collected in 2000–2002 from 497 sites among 16 basins and predictor variables from geospatial models produced from remotely sensed data (e.g., digital elevation model, complex topographic index, landform data, wetland probability, and vegetative cover). Except for 31 sites in one basin that were surveyed in both 2000 and 2002, all sites were surveyed once. We used polytomous regression to build statistical models for each species of amphibian from (1) field survey site data only, (2) field data combined with data from geospatial models, and (3) data from geospatial models only. Based on measures of receiver operating characteristic (ROC) scores, models of the second type best explained likely breeding habitat because they contained the most information (ROC values ranged from 0.70 to 0.88). However, models of the third type could be applied to the entire YNP landscape and produced maps that could be verified with reserve field data. Accuracy rates for models built for single years were highly variable, ranging from 0.30 to 0.78. Accuracy rates for models built with data combined from multiple years were higher and less variable, ranging from 0.60 to 0.80. Combining results from the geospatial multiyear models yielded maps of ‘‘core’’ breeding areas (areas with high probability values for all three years) surrounded by areas that scored high for only one or two years, providing an estimate of variability among years. Such information can highlight landscape options for amphibian conservation. For example, our models identify alternative areas that could be protected for each species, including 6828–10 764 ha for tiger salamanders, 971–3017 ha for western toads, 4732–16 696 ha for boreal chorus frogs, and 4940–19 690 ha for Columbia spotted frogs.

Variation in the occurrence and abundance of species across landscapes has traditionally been attributed to processes at fine spatial scales (i.e., local conditions), but processes that operate across larger spatial scales such as seasonal migration or dispersal are also important. Recognition of the importance of processes that operate at broad, as well as fine, scales is growing. We evaluated hypothesized relationships between the probability of occupancy in wetlands by wood frogs (Lithobates sylvaticus) and boreal chorus frogs (Pseudacris maculata) during the breeding season and attributes of the landscape measured at three spatial scales in Rocky Mountain National Park, Colorado. We also used cost-based buffers and least-cost distances to derive estimates of landscape attributes at the broader spatial scales represented by seasonal movement and dispersal. Occupancy by breeding wood frogs was associated positively with the amount of streamside habitat adjacent to a wetland and associated negatively with the cost-based distance to the nearest occupied wetland. Occupancy by boreal chorus frogs was associated positively with the number of neighboring, occupied wetlands. We found little evidence that occupancy was correlated with fine-scale attributes measured at the wetlands.

The Mole Salamander displays geographic variation in egg deposition mode, as well as other reproductive traits. Such variation suggests the potential for genetic differentiation within this species, yet no subspecies are currently recognized. We provide additional information on the timing and mode of oviposition in A. talpoideum to aid in further understanding the geographic scope of variation in this species’ reproductive traits. In 2009, we sampled 15 ponds at St. Marks National Wildlife Refuge, Wakulla County, Florida, USA for larval and paedomorphic A. talpoideum. During a period of heavy rainfall, we observed an adult metamorphosed female A. talpoideum and a newly-deposited egg mass on 2 and 3 April 2009, respectively. To our knowledge, our observation of a new egg mass on 3 April is the latest reported date of new oviposition for this species on the Coastal Plain. In contrast to populations in the Atlantic Coastal Plain, where females deposit eggs singly, our observation also reveals that individuals of A. talpoideum in the panhandle region of Florida produce egg masses, similar to populations of this species in western parts of its range (Mississippi and Louisiana). This observation suggests that the faunal break between populations that lay eggs singly, versus those that produce egg masses, is much farther east than has been previously reported and closer to the likely geographic point of separation between populations of the two egg-laying modes. Additional information on egg-laying mode and other reproductive characteristics in Gulf and Atlantic Coastal Plain populations would be insightful for understanding the extent of geographic variation in reproduction and would help pinpoint the location of a faunal break between populations of the two egg laying modes in this species.