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1290 record(s) found.
Papers & Reports Estimating occurrence, prevalence, and detection of amphibian pathogens: insights from occupancy models
Authors: Brittany A Mosher; Adrianne B Brand; A N Wiewel; David AW Miller; M J Gray; D L Miller; Evan HC Grant
Date: 2019 | Outlet: Journal of Wildlife Diseases
Understanding the distribution of pathogens across landscapes and within host populations is a common aim of wildlife managers. Despite the need for unbiased inferences about these parameters to plan effective management interventions, many researchers fail to account for imperfect pathogen detection and instead report only raw data, which may lead to improper management. We demonstrate analyses of ranavirus detection data in the Patuxent Research Refuge using an occupancy modeling approach, which yields unbiased estimates of pathogen occurrence and prevalence. To improve inference and reporting of pathogen and disease parameters, we describe our approach in-text and provide a written tutorial on how to fit these models using the freely available software Program PRESENCE. In our case study, ranavirus prevalence was underestimated up to 30% if imperfect detection was ignored. After accounting for imperfect detection, estimates of ranavirus prevalence in larval wood frogs (Lithobates sylvaticus) were higher than in larval spotted salamanders (Ambystoma maculatum). In addition, we found that the odds of detecting ranavirus in tail samples were 6.7 times higher than detecting ranavirus in liver samples. We discuss how this information can be used to design ranavirus surveillance studies. Our tutorial provides a clear guide for practitioners and researchers wishing to make unbiased inference in a variety of host-pathogen systems.
Papers & Reports Compounding effects of climate change reduce population viability of a montane amphibian
Authors: Amanda M Kissel; Wendy J Palen; Maureen E Ryan; Michael J Adams
Date: 2018-12-27 | Outlet: Ecological Applications
Anthropogenic climate change presents challenges and opportunities to the growth, reproduction, and survival of individuals throughout their life cycles. Demographic compensation among life-history stages has the potential to buffer populations from decline, but alternatively, compounding negative effects can lead to accelerated population decline and extinction. In montane ecosystems of the US Pacific Northwest, increasing temperatures are resulting in a transition from snow-dominated to rain-dominated precipitation events, reducing snowpack. For ectotherms such as amphibians, warmer winters can reduce the frequency of critical minimum temperatures and increase the length of summer growing seasons, benefiting post-metamorphic stages, but may also increase metabolic costs during winter months, which could decrease survival. Lower snowpack levels also result in wetlands that dry sooner or more frequently in the summer, increasing larval desiccation risk. To evaluate how these challenges and opportunities compound within a species? life history, we collected demographic data on Cascades frog (Rana cascadae) in Olympic National Park in Washington state to parameterize stage-based stochastic matrix population models under current and future (A1B, 2040s and 2080s) environmental conditions. We estimated the proportion of reproductive effort lost each year due to drying using watershed-specific hydrologic models, and coupled this with an analysis that relates 15-years of R. cascadae abundance data with a suite of climate variables. We estimated the current population growth (λs) to be https://0.98 (95% CI: 0.97-0.99), but predict that λs will decline under continued climate warming, resulting in a 62% chance of extinction by the 2080s because of compounding negative effects on early and late life history stages. By the 2080s, our models predict that larval mortality will increase by 17% as a result of increased pond drying, and adult survival will decrease by 7% as winter length and summer precipitation continue to decrease. We find that reduced larval survival drives initial declines in the 2040s, but further declines in the 2080s are compounded by decreases in adult survival. Our results demonstrate the need to understand the potential for compounding or compensatory effects within different life history stages to exacerbate or buffer the effects of climate change on population growth rates through time.
Papers & Reports Multistate occupancy modeling improves understanding of amphibian breeding dynamics in the Greater Yellowstone Area
Authors: W R Gould; Andrew M Ray; Larissa L Bailey; D Thoma; R Daley; K Legg
Outlet: Ecological Applications
Papers & Reports Identifying management-relevant research priorities for responding to disease-associated amphibian declines
Authors: Evan HC Grant; Michael J Adams; Robert N Fisher; Daniel A Grear; Brian J Halstead; Blake R Hossack; Erin Muths; Katherine LD Richgels; Robin E Russell; Kelly L Smalling; Hardin J Waddle; Susan C Walls; C Le White
Date: 2018-10 | Outlet: Global Ecology and Conservation
A research priority can be defined as a knowledge gap that, if resolved, identifies the optimal course of conservation action. We (a group of geographically distributed and multidisciplinary research scientists) used tools from nominal group theory and decision analysis to collaboratively identify and prioritize information needs within the context of disease-associated amphibian decline, in order to develop a strategy that would support US management agency needs. We developed iterated influence diagrams to create and assess a unified research strategy. We illustrated a transparent process for identifying specific knowledge gaps in amphibian disease ecology relevant to environmental management, and then constructed a research plan to address these uncertainties. The resulting priorities include a need to: (1) understand the drivers of the community-disease relationship, (2) determine the mechanisms by which exposure to contaminants influence disease outcomes, (3) identify elements of terrestrial and aquatic habitats that stabilize host-pathogen dynamics, (4) discuss how metapopulations may be managed to reduce the speed and intensity of disease outbreaks, and (5) define the relationship between habitat management and the environmental and host microbiomes. Along with identifying research priorities for disease management, we present the details of the process used to develop a consensus plan for addressing disease-related declines in amphibians on federally managed lands of the United States.
News & Stories Exploring the amphibian exposome in an agricultural landscape using telemetry and passive sampling
Authors: J E Swanson; Erin Muths; Clay L Pierce; S Dinsmore; M Vandever; Michelle L Hladik; Kelly L Smalling
September 11, 2018
USGS and Iowa State University scientists quantified Northern Leopard frog exposure to pesticides in aquatic and terrestrial habitats using a novel combination of radio telemetry and passive sampling techniques to better understand factors affecting frog health and survival in agricultural landscapes. The results of this newly published research can inform conservation strategies by providing information about when and where the frogs are most likely exposed to pesticides. This unique approach can be utilized in other land-use settings and with other amphibian species to better understand if contaminant exposure affects growth, development, fitness, and survival.
Full article is available here: https://www.nature.com/articles/s41598-018-28132-3
News & Stories Collaborative ARMI work first step in status assessment for cave salamander
Authors: Evan HC Grant; Adrianne B Brand
September 11, 2018
As part of a partnership with the USFWS, WV Division of Natural Resources, and The Nature Conservancy, Northeast ARMI staff and a USGS Water Resources hydrologist conducted a field survey in late August for the WV spring salamander, a rare amphibian with known range limited to a single cave in WV. This work is an important contribution of the status assessment for the species, which has been proposed for listing under the Endangered Species Act. Species identification is made via morphological traits, but these may be imperfect, and thus misidentification is highly likely. ARMI is developing models that can accommodate this misidentification error, which will be used to improve the precision and reduce the bias in estimates of population status. In addition to field surveys, USGS ARMI will contribute morphologic and genetic analyses, and water quality assessment to identify and characterize potential threats, to address information needs for the USFWS listing decision, due in 2020.
Papers & Reports Time-to-detection Occupancy Modeling: An Efficient Method for Analyzing the Occurrence of Amphibians and Reptiles
Authors: Brian J Halstead; Patrick M Kleeman; Jonathan P Rose
Date: 2018-11-27 | Outlet: Journal of Herpetology 52:416-425
Occupancy models provide a reliable measure of species distributions while accounting for imperfect detectability. The cost of accounting for false absences is that occupancy surveys typically require repeated visits to a site or multiple-observer techniques. More efficient methods of estimating detection probabilities would allow more sites to be surveyed for the same effort, resulting in more information about the ecological processes leading to occupancy. Time-to-detection surveys allow the estimation of detection probability based on a single site visit by one observer, and therefore might be an efficient technique for herpetological occupancy studies. We evaluated the use of time-to-detection surveys to estimate the occupancy of pond-breeding amphibians at Point Reyes National Seashore, California, USA, including variables that affected detection rates and the probability of occurrence. We found that detection times were short enough and occupancy high enough to reliably estimate the probability of occurrence of three pond-breeding amphibians at Point Reyes National Seashore, and that survey and site conditions had species-specific effects on detection rates. In particular, relative abundance was negatively related to the time to initial detection of all species, and pond area was positively related to time to initial detection for Sierran Treefrogs (Hyliola sierra) and Rough-skinned Newts (Taricha granulosa). Rough-skinned newt time to initial detection also was affected by date, with lowest initial detection time in early summer. California Red-legged Frog (Rana draytonii) time to detection was lowest in ponds with a mean depth of 0.6 m, and higher in shallower and deeper ponds. Probability of occurrence of Sierran Treefrogs and Rough-skinned Newts was negatively related to the presence of fish and pond area. Rarely detected species required constraints on priors to fit time-to-detection models. Time-to-detection surveys can provide an efficient method of estimating detection probabilities and accounting for false absences in occupancy studies of reptiles and amphibians.
Papers & Reports Aquatic macroinvertebrate community response to wetland mitigation in the Greater Yellowstone Ecosystem
Authors: L K Swartz; Blake R Hossack; Erin Muths; R L Newell; W H Lowe
Date: 2019 | Outlet: Freshwater Biology 64: 942-953
Papers & Reports Effects of Persistent Energy-related Brine Contamination on Amphibian Abundance in National Wildlife Refuge Wetlands
Authors: Blake R Hossack; Kelly L Smalling; Chauncey W Anderson; Todd Preston; I M Cozzarelli,; R K Honeycutt
Date: 2018 | Outlet: Biological Conservation 228:36–43
Papers & Reports Estimating the probability of movement and partitioning seasonal survival in an amphibian metapopulation
Authors: Erin Muths; Larissa L Bailey; Brad A Lambert; S Schneider
Date: 2018-12 | Outlet: Ecosphere
Movement of individuals has been described as one of the best studied, but least understood concepts in ecology. The magnitude of movements, routes, and probability of movement, has significant application to conservation. Information about movement can inform efforts to model species persistence and is particularly applicable in situations where specific threats (e.g., disease) may depend on the movement of hosts and potential vectors. We estimated the probability of movement (breeding dispersal and permanent emigration) in a metapopulation of 16 breeding sites for boreal toads (Anaxyrus boreas boreas). We used a multi-state mark-recapture approach unique in its complexity (16 sites over 18 years) to address questions related to these movements and variation in resident survival. We found that individuals had a 1-2% probability of dispersing in a particular year and that approximately 10-20% of marked individuals were transient and observed in the metapopulation only once. Resident survival probabilities differed by season, with 71-90% survival from emergence from hibernation through early post-breeding and > 97% survival from mid/late active season through hibernation. Movement-related probabilities are needed to predict species range expansions and contractions, estimate population and metapopulation dynamics, understand host-pathogen and native-invasive species interactions, and to evaluate the relative effects of proposed management actions.
News & Stories Invasive crayfish wreck havoc on amphibians in southern California, and now its clear they also increase mosquito larvae.
Authors: Gary Bucciarelli; D Suh; A Davis; D Roberts; D Sharpton; H B Shaffer; Robert N Fisher; Lee B Kats
August 20, 2018
Previous work by ARMI scientists have shown the important impact of invasive crayfish (Procambarus clarkii) on endangered and threatened amphibian species in southern California (https://onlinelibrary.wiley.com/doi/abs/10.1111/cobi.13198 ). New published research has shown that these non-native predators may increase disease vectors (e.g. mosquitoes) through predation on native predators of these vectors such as dragonfly nymphs (https://www.usgs.gov/center-news/invasive-crayfish-increase-number-mosquitoes-southern-california-mountains). This work has also been highlighted in a recent National Geographic report on the study (https://www.nationalgeographic.com/animals/2018/08/swamp-crayfish-crawfish-mosquitoes-disease-animals/).
Papers & Reports Late-season movement and habitat use by Oregon Spotted Frog (Rana pretiosa in Oregon, USA
Authors: Christopher A Pearl; Brome McCreary; Jennifer C Rowe; Michael J Adams
Date: 2018-09-27 | Outlet: Copeia
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 9 sites from 4 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 specialized distinctive habitats such as springs, interstices in lava rock, and semi-terrestrial beaver channels. Distance between first and last tracking location was <250 m for 84.5% (49/58) of frogs, ranged up to 1145 m, and was greater for frogs in ditch habitats than those not in ditches. DistinctiveSpecialized features like springs or semi-terrestrial retreats can host multiple frogs and may represent particularly valuable wintering habitat for R. pretiosa in some sites in their Oregon range.
Papers & Reports CO-OCCURENCE OF CHIRICAHUA LEOPARD FROGS (LITHOBATES CHIRICAHUENSIS) WITH SUNFISH (LEPOMIS SPP.)
Authors: P E Howell; Brent H Sigafus; Blake R Hossack; Erin Muths
Outlet: Southwestern Naturalist 64:69-72
Invasive species are a major threat to the persistence of native species, particularly in systems where ephemeral aquatic habitats have been converted to or replaced by permanent water and predators such as fish have been introduced. Within the Altar Valley, Arizona, USA, the invasive American bullfrog (Lithobates [=Rana] catesbeianus) has been successfully eradicated to help recover Chiricahua leopard frogs (Lithobates chiricahuensis). However, other non-native predators including sunfish (Lepomis spp) are present in some permanent water bodies. During four consecutive years (2014-2017) we detected both the federally-threatened Chiricahua leopard frog and sunfish at one permanent water body in the Altar Valley. This suggests that despite the potential negative effect of predatory fish on amphibians, there may be conditions where the Chiricahua leopard frog may be able to co-occur with this non-native predator. A better understanding of rare situations of co-occurrence with non-native predators may contribute to our understanding of why co-occurrence happens in some but not all systems and whether conservation strategies can be developed in situations where complete eradication of non-native predators is infeasible.
Papers & Reports Twenty-nine years of population dynamics in a small-bodied montane amphibian
Authors: Erin Muths; R D Scherer; Staci M Amburgey; P. Stephen Corn
Outlet: Ecosphere
Identifying population declines before they reach crisis proportions is imperative given the current global decline in vertebrate fauna and the associated challenges and expense of recovery. Understanding life-histories and how the environment influences demography are critical aspects of this challenge, as is determining the biological relevance of covariates that are best supported by data. We used 29 years of data on chorus frogs at two sites to estimate demographic parameters, examine life-history, assess weather-related covariates, and determine the magnitude of process variation in target parameters. Average estimates of survival probabilities were https://0.51 (SE=0.04) and https://0.43 (SE=0.04), and average estimates of recruitment probabilities were https://0.64 (SE=0.07) and https://0.44 (SE=0.04). Process variation accounted for  76% of the total temporal variation in both parameters at one pond and in survival probability alone at the other, suggesting that the covariates in our top models were explaining predominantly process rather than sampling variation. Estimates of population growth rates indicated a declining population at one pond (i.e., negative population growth rates in 15 of 18 years) and comparisons with historical estimates suggested declines in survival probability at the other. The amount of deviance explained was low, providing little support for the influence of covariates on target parameters, despite model selection support. Synthesis and applications: This analysis illustrates the value of disentangling components of variance when assessing demographic drivers and highlights the need for adequate demographic information in assigning conservation labels.
Papers & Reports The relative efficiency of native and non-native aquatic species as predators of potential disease vectors: Invasive crayfish enhance the survival of mosquitoes
Authors: Gary Bucciarelli; D Suh; A Davis; D Sharpton; D Roberts; H B Shaffer; Robert N Fisher; Lee B Kats
Date: 2018-08-06 | Outlet: Conservation Biology
The introductions of non-native predators often reduce biodiversity and affect natural predator-prey relationships. However, non-native predators may increase the abundance of potential disease vectors (e.g. mosquitoes) indirectly through competition or predation cascades. The Santa Monica
Mountains, situated in a global biodiversity hotspot, is an area of conservation concern due to climate change, urbanization, and the introduction of non-native species. We examined the effect that non-native crayfish (Procambarus clarkii) have on an existing native predator, dragonfly nymphs (Aeshna sp.) and their mosquito larvae (Anopheles sp.) prey. We used laboratory experiments to compare the predation efficiency of both predators, separately and together, and field data on counts of dragonfly nymphs and mosquito larvae sampled from 13 local streams. We predicted a lower predation efficiency of crayfish compared to native dragonfly nymphs as well as a reduced efficiency of dragonfly nymphs in the presence of crayfish. Dragonfly nymphs were an order of magnitude more efficient mosquito predators compared to crayfish and dragonfly
nymphs suffered reduced efficiency in the presence of crayfish. Analyses of field count data showed that populations of dragonfly nymphs and mosquito larvae were strongly correlated with crayfish presence in streams, such that sites with crayfish tended to have fewer dragonfly
nymphs and more mosquito larvae. Under natural conditions, it is likely that crayfish reduce the abundance of dragonfly nymphs and their predation efficiency, and thereby, directly and indirectly, lead to higher mosquito populations and a loss of ecosystem services related to disease vector control.
Mountains, situated in a global biodiversity hotspot, is an area of conservation concern due to climate change, urbanization, and the introduction of non-native species. We examined the effect that non-native crayfish (Procambarus clarkii) have on an existing native predator, dragonfly nymphs (Aeshna sp.) and their mosquito larvae (Anopheles sp.) prey. We used laboratory experiments to compare the predation efficiency of both predators, separately and together, and field data on counts of dragonfly nymphs and mosquito larvae sampled from 13 local streams. We predicted a lower predation efficiency of crayfish compared to native dragonfly nymphs as well as a reduced efficiency of dragonfly nymphs in the presence of crayfish. Dragonfly nymphs were an order of magnitude more efficient mosquito predators compared to crayfish and dragonfly
nymphs suffered reduced efficiency in the presence of crayfish. Analyses of field count data showed that populations of dragonfly nymphs and mosquito larvae were strongly correlated with crayfish presence in streams, such that sites with crayfish tended to have fewer dragonfly
nymphs and more mosquito larvae. Under natural conditions, it is likely that crayfish reduce the abundance of dragonfly nymphs and their predation efficiency, and thereby, directly and indirectly, lead to higher mosquito populations and a loss of ecosystem services related to disease vector control.
Papers & Reports Regional variation in drivers of connectivity for two frog species (Rana pretiosa and R. luteiventris) from the U.S. Pacific Northwest
Authors: Jeanne M Robertson; M A Murphy; Christopher A Pearl; Michael J Adams; M I Páez-Vacas; S M Haig; David S Pilliod; A Storfer; W C Funk
Date: 2018-07-16 | Outlet: Molecular Ecology
Comparative landscape genetics has uncovered high levels of variability in which landscape factors affect connectivity among species and regions. However, the relative importance of species traits vs. environmental variation for predicting landscape patterns of connectivity is unresolved. We provide a test with a landscape genetics study of two sister taxa of frogs, the Oregon spotted frog (Rana pretiosa) and the Columbia spotted frog (R. luteiventris) in Oregon and Idaho, USA. Rana pretiosa is relatively more dependent on moisture for dispersal than R. luteiventris, so if species traits influence connectivity, we predicted that connectivity among R. pretiosa populations would be more positively associated with moisture than R. luteiventris. However, if environmental differences are important drivers of gene flow, we predicted that connectivity would be more positively related to moisture in arid regions. We tested these predictions using eight microsatellite loci and gravity models in two R. pretiosa regions and four R. luteiventris regions (n = 1,168 frogs). In R. pretiosa, but not R. luteiventris, connectivity was positively related to mean annual precipitation, supporting our first prediction. In contrast, connectivity was not more positively related to moisture in more arid regions. Various temperature metrics were important predictors for both species and in all regions, but the directionality of their effects varied. Therefore, the pattern of variation in drivers of connectivity was consistent with predictions based on species traits rather than on environmental variation.
Papers & Reports Pre-publication communication of research results
Authors: Michael J Adams; Reid N Harris; Evan HC Grant; M J Gray; Maria-Richetta C Hopkins; S A Iverson; R Likens; Mark Mandica; Deanna H Olson; A Shepack; Hardin J Waddle
Date: 2018-08-11 | Outlet: EcoHealth
Until publication, communication of provisional scientific findings beyond participants in the study is typically limited. This practice helps assure scientific integrity. However, a dilemma arises when a provisional finding has urgent societal consequences that may be exacerbated by delay. This dilemma may be particularly pronounced when a discovery concerns wildlife health, which could have implications for conservation, public health, or domestic animal health. Eleven researchers suggest that common concerns about directed prepublication communication largely stem from misperceptions and that none should cause a delay in the communication of time-sensitive provisional findings to appropriate authorities. Instead, they suggest that rapid communication of a provisional discovery could be beneficial, such as in the example they use involving the potential discovery of the amphibian fungal pathogen Bsal that is currently causing salamander die-offs in Europe.
Papers & Reports Pharmaceuticals, Hormones, Pesticides, and other Bioactive Contaminants in Water, Sediment, and Tissue from Rocky Mountain National Park, 2012-2013
Authors: William A Battaglin; Paul M Bradley; L Iwanowicz; Celeste A Journey; Vicki S Blazer
Date: 2018-06-05 | Outlet: Science of the Total Environment 643:651-673
Pharmaceuticals, hormones, pesticides, and other bioactive contaminants (BCs) are commonly detected in surface water and bed sediment in urban and suburban areas, but these contaminants are understudied in remote locations. In Rocky Mountain National Park (RMNP), Colorado, USA, BCs may threaten the reproductive success and survival of native aquatic species, benthic communities, and pelagic food webs. In 2012-2013, 67 water, 57 sediment, 63 fish, 10 frog, and 12 quality-control samples (8 water and 4 sediment) were collected from 20 sites in RMNP. Samples were analyzed for 369 parameters including 149 pharmaceuticals, 22 hormones, 137 pesticides, and 61 other chemicals or conditions to provide a representative assessment of BC occurrence within RMNP. Results indicate that BCs were detected in water and/or sediment from both remote and more accessible locations in RMNP. The most commonly detected BCs in water were caffeine, camphor, para-cresol, and DEET; and the most commonly detected BCs in sediment were indole, 3-methyl-1H-indole, para-cresol, and 2,6-dimethyl-naphthalene. Some detected contaminants, including carbaryl, caffeine, and oxycodone, are clearly attributable to direct local human input, whereas others may be transported into the park atmospherically (e.g., atrazine) or have local natural sources (e.g., para-cresol). One or more pharmaceuticals were detected in at least 1 sample from 15 of 20 sites. Most of the 29 detected pharmaceuticals are excreted primarily in human urine, not feces. Elevated net estrogenicity was observed in 18% of water samples, and elevated vitellogenin in blood was observed in 12% of male trout, both evidence of potential endocrine disruption. Hormone concentrations in sediment tended to be greater than concentrations in water. Most BCs were observed at concentrations below those not expected to pose adverse effects to aquatic life. Results indicate that even in remote locations aquatic wildlife can be exposed to pharmaceuticals, hormones, pesticides, and other bioactive contaminants.
Papers & Reports Quantifying climate sensitivity and climate driven change in North American amphibian communities
Authors: David AW Miller; Evan HC Grant; Erin Muths; Staci M Amburgey; Michael J Adams; M B Joseph; Hardin J Waddle; P TJ Johnson; Maureen E Ryan; Benedikt R Schmidt; Daniel L Calhoun; Courtney L Davis; Robert N Fisher; David E Green; Blake R Hossack; Tracy A. Rittenhouse; Susan C Walls; Larissa L Bailey; Sam S Cruickshank; Gary M Fellers; Thomas A Gorman; C A Haas; Ward Hughson; David S Pilliod; S J Price; Andrew M Ray; Walt J Sadinski; D Saenz; William J Barichivich; Adrianne B Brand; Cheryl S Brehme; Rosi G Dagit; Katy S Delaney; Brad M Glorioso; Lee B Kats; Patrick M Kleeman; Christopher A Pearl; Carlton J Rochester; Seth PD Riley; Mark F Roth; Brent H Sigafus
Date: 2018-08 | Outlet: Nature Communications
We quantified the response of amphibian communities to climatic variability across the United States and Canada using more than 500,000 observations for 81 species across 86 study areas. We estimated the relationships between annual variation in climate variables and local colonization and persistence probabilities across more than 5000 surveyed sites. This allowed us to estimate sensitivity to change in five climate variables. Climate sensitivity differs greatly among eco-regions and depends on local climate, species life-history, and phylogeny. Local species richness was especially sensitive to changes in water availability during breeding and changes in winter temperature. These results allowed us to ask whether changing climate explains strong overall rates of decline in species richness observed in our data set. We found that recent change in the climate variables we measured does not explain why North American amphibian richness is rapidly declining, but does explain why some populations decline faster than others. 
News & Stories 1000 Critically Endangered Mountain Yellow-legged Frogs released back into Los Angeles County!
Authors: Robert N Fisher; Adam R Backlin; Elizabeth A Gallegos
June 27, 2018
The USGS has been leading the recovery efforts for the Southern Mountain Yellow-legged Frogs (Rana muscosa) since 2000, in partnership with the USFWS, California Department of Fish and Wildlife, US Forest Service, Los Angeles Zoo, San Diego Zoo Global, and other partners. On June 26 and 27, 2018, 1000 tadpoles produced from captive frogs raised at the Los Angeles Zoo were released into the San Gabriel Mountains National Monument for the first time. These were placed into two different watersheds. More releases are scheduled for later in the summer, but this is a pivotal step in the recovery of this species back onto federal lands within its historic habitats.
Los Angeles Times news story at this link: http://www.latimes.com/local/california/la-me-rare-frog-release-20180627-story.html