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Papers & Reports Amphibian dynamics in constructed ponds on a wildlife refuge: developing expected responses to hydrological restoration
Authors: Blake R Hossack
Date: 2016 | Outlet: Hydrobiologia
Management actions are based upon predictable responses. To form expected responses to restoration actions, I estimated habitat relationships and trends (2002‒2015) for four pond-breeding amphibians on a wildlife refuge (Montana, USA) where changes to restore historical hydrology to the system greatly expanded (≥8 times) the flooded area of the primary breeding site for western toads (Anaxyrus boreas). Additional restoration actions are planned for the near future, including removing ponds that provide amphibian habitat. Multi-season occupancy models based on data from 15 ponds sampled during 7 years revealed that the number of breeding subpopulations increased modestly for Columbia spotted frogs (Rana luteiventris) and was stationary for long-toed salamanders (Ambystoma macrodactylum) and Pacific treefrogs (Pseudacris regilla). For these three species, pond depth was the characteristic that was associated most frequently with occupancy or changes in colonization and extinction. In contrast, a large decrease in colonization by western toads explained the decline from eight occupied ponds in 2002 to two ponds in 2015. This decline occurred despite an increase in wetland area and the colonization of a newly-created pond. These changes highlight the challenges of managing for multiple species and how management responses can be unpredictable, possibly reducing the efficacy of targeted actions.
Papers & Reports Large-scale recovery of an endangered amphibian despite ongoing exposure to multiple stressors
Authors: Roland A Knapp; Gary M Fellers; Patrick M Kleeman; David AW Miller; V T Vredenburg; Erica B Rosenblum; Cheryl J Briggs
Date: 2016-10-03 | Outlet: Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.1600983113
Amphibians are one of the most threatened animal groups, with 32% of species at risk of extinction. Given this, is the disappearance of a large fraction of the Earth’s amphibians inevitable, or are some declining species more resilient than is generally assumed? We address this question in a species that is emblematic of many declining amphibians, the endangered Sierra Nevada yellow-legged frog (Rana sierrae). Based on >7,000 frog surveys conducted across Yosemite National Park over a 20-year period, we show that after decades of decline and despite ongoing exposure to multiple stressors including introduced fish, the recently emerged disease chytridiomycosis, and pesticides, R. sierrae abundance increased 7-fold during the study and at a rate of 11% per year. These increases occurred in hundreds of populations throughout Yosemite, providing a rare example of amphibian recovery at an ecologically relevant spatial scale. Results from a laboratory experiment indicate that these increases may be due in part to reduced frog susceptibility to chytridiomycosis. The disappearance of nonnative fish from numerous water bodies following cessation of stocking also contributed to the recovery. The large-scale increases in R. sierrae abundance we document suggest that when habitats are relatively intact and stressors are reduced in their importance by active management or species’ adaptive responses declines of some amphibian may be partially reversible, at least at a regional scale. Other studies conducted over similarly large temporal and spatial scales are critically needed to provide insight and generality about the reversibility of amphibian declines at a global scale.
Papers & Reports Estimating occurrence and detection probabilities for stream-breeding salamanders in the Gulf Coastal Plain
Authors: J Y Lamb; Hardin J Waddle; C P Qualls
Date: 2017-03 | Outlet: Journal of Herpetology 51:102-108
Large gaps exist in our knowledge of the ecology of stream-breeding plethodontid salamanders in the Gulf Coastal Plain. Data describing where these salamanders are likely to occur along environmental gradients, as well as their likelihood of detection, are important for the prevention and management of amphibian declines. We used presence/absence data from leaf litter bag surveys and a hierarchical Bayesian multispecies single-season occupancy model to estimate the occurrence of five species of plethodontids across reaches in headwater streams in the Gulf Coastal Plain. Average detection probabilities were high (range = 0.432-0.942) and unaffected by sampling covariates specific to the use of litter bags (i. e., bag submergence, sampling season, in-stream cover). Estimates of occurrence probabilities differed substantially between species (range = 0.092-0.703) and were influenced by the size of the upstream drainage area and by the maximum proportion of the reach that dried. The effects of these two factors were not equivalent across species. Our results demonstrate that hierarchical multispecies models successfully estimate occurrence parameters for both rare and common streambreeding plethodontids. The resulting models clarify how species are distributed within stream networks, and they provide baseline values that will be useful in evaluating the conservation statuses of plethodontid species within lotic systems in the Gulf Coastal Plain.
Papers & Reports Life history plasticity does not confer resilience to environmental change in the mole salamander (Ambystoma talpoideum)
Authors: Courtney L Davis; David AW Miller; Susan C Walls; William J Barichivich; Jeffrey W Riley; Mary E Brown
Date: 2017-03 | Outlet: Oecologia 183(3):739-749.
Plasticity in life history strategies can be advantageous for species that occupy spatially or temporally variable environments. We examined how phenotypic plasticity influences responses of the mole salamander, Ambystoma talpoideum, to disturbance events at the St. Marks National Wildlife Refuge (SMNWR), FL, USA from 2009 to 2014. We observed periods of extensive drought early in the study, in contrast to high rainfall and expansive flooding events in later years. Flooding facilitated colonization of predatory fishes to isolated wetlands across the refuge. We employed multistate occupancy models to determine how this natural experiment influenced the occurrence of aquatic larvae and paedomorphic adults and what implications this may have for the population. We found that, in terms of occurrence, responses to environmental variation differed between larvae and paedomorphs, but plasticity (i.e. the ability to metamorphose rather than remain in the aquatic environment) was not sufficient to buffer populations from declining as a result of environmental perturbations. Drought and fish presence negatively influenced occurrence dynamics of larval and paedomorphic mole salamanders and, consequently, contributed to observed short-term declines of this species. Overall occurrence of larval salamanders decreased from https://0.611 in 2009 to https://0.075 in 2014 and paedomorph occurrence decreased from https://0.311 in 2009 to https://0.121 in 2014. Although variation in selection pressures has likely maintained this polyphenism previously, our results suggest that continued changes in environmental variability and the persistence of fish in isolated wetlands could lead to a loss of paedomorphosis in the SMNWR population and, ultimately, impact regional persistence in the future.
Papers & Reports Extinction Debt as a Driver of Amphibian Declines: an Example with Imperiled Flatwoods Salamanders
Authors: Raymond D Semlitsch; Susan C Walls; William J Barichivich; Katherine M O'Donnell
Date: 2017-01-11 | Outlet: Journal of Herpetology 51(1):12-18.
A comprehensive view of population declines and their underlying causes is necessary to reverse species’ loss. Historically, in many cases, a narrow view may have allowed species’ declines to continue, virtually undetected, for long periods of time (perhaps even decades). We suggest that extinction debt is likely responsible for numerous (and perhaps most) amphibian declines and that this perspective should be incorporated into the structure of amphibian research and management. Extinction debt, originally proposed to explain changes in species richness following environmental disturbance, may also refer to the proportion of populations of an individual species that is expected to eventually be lost due to habitat change. A conservation framework to address extinction debt focuses research on threats at the individual, population, and metapopulation levels. This approach will help enhance, restore, and protect specific processes and habitats at the proper scale by directing management to the most vulnerable level and stage of a species. We illustrate this approach using Flatwoods Salamanders, Ambystoma cingulatum and Ambystoma bishopi, which occurred historically throughout the Coastal Plain of the southeastern USA but have experienced a > 85% loss of populations in recent years. Reversal of these losses is possible only if conservation and recovery efforts encompass individual, population, and metapopulation levels. We illustrate our framework by outlining actions that could be taken at each of these levels to help guide conservation and management of amphibians with complex life cycles.
Papers & Reports Species interactions and the effects of climate variability on a wetland amphibian metacommunity
Authors: Courtney L Davis; David AW Miller; Susan C Walls; William J Barichivich; Jeffrey W Riley; Mary E Brown
Date: 2016-10-02 | Outlet: Ecological Applications 27(1):285-296.
Disentangling the role that multiple interacting factors have on species responses to shifting climate poses a significant challenge. However, our ability to do so is of utmost importance to predict the effects of climate change on species distributions. We examined how populations of three species of wetland breeding amphibians, which varied in life history requirements, responded to a six-year period of extremely variable in precipitation. This interval was punctuated by both extensive drought and heavy precipitation and flooding, providing a natural experiment to measure community responses to environmental perturbations. We estimated occurrence dynamics using a discrete hidden Markov modeling approach that incorporated information regarding habitat state and predator-prey interactions. This approach allowed us to measure how metapopulation dynamics of each amphibian species was affected by interactions among weather, wetland hydroperiod, and co-occurrence with fish predators. The pig frog, a generalist, proved most resistant to perturbations, with both colonization and persistence being unaffected by seasonal variation in precipitation or co-occurrence with fishes. The ornate chorus frog, an ephemeral wetland specialist, responded positively to periods of drought owing to increased persistence and colonization rates during periods of low-rainfall. Low probabilities of occurrence of the ornate chorus frog in long-duration wetlands were driven by interactions with predators due to low colonization rates when fishes were present. The mole salamander was most sensitive to shifts in water availability. In our study area, this species never occurred in short-duration wetlands and persistence probabilities decreased during periods of drought. At the same time, negative effects occurred with extreme precipitation because flooding facilitated colonization of fishes to isolated wetlands and mole salamanders did not colonize wetlands once fishes were present. We demonstrate that the effects of changes in water availability depend on interactions with predators and wetland type and are influenced by the life history of each of our species. The dynamic species occurrence modeling approach we used offers promise for other systems when the goal is to disentangle the complex interactions that determine species responses to environmental variability.
Papers & Reports Influence of climate drivers on colonization and extinction
Authors: Andrew M Ray; W R Gould; Blake R Hossack; A Sepulveda; D Thoma; Debra A Patla; R Daley; Robert Al-Chokhachy
Date: 2016 | Outlet: Ecosphere 7:1-21
Freshwater wetlands are particularly vulnerable to climate change. Specifically, changes in
temperature, precipitation, and evapotranspiration (i.e., climate drivers) are likely to alter flooding regimes of wetlands and affect the vital rates, abundance, and distributions of wetland-dependent species. Amphibians may be among the most climate-sensitive wetland-dependent groups as many species rely on shallow or intermittently flooded wetland habitats for breeding. Here, we integrated multiple years of high-resolution gridded climate and amphibian monitoring data from Grand Teton and Yellowstone National Parks to explicitly model how variations in climate drivers and habitat conditions affect the occurrence and breeding dynamics (i.e., annual extinction and colonization rates) of amphibians. Our results showed that models incorporating climate drivers outperformed models of amphibian breeding dynamics that were exclusively habitat based. Moreover, climate-driven variation in extinction rates, but not colonization rates, disproportionately influenced amphibian occupancy in monitored wetlands. Long-term monitoring from national parks coupled with high-resolution climate data sets will be crucial to describing population dynamics and characterizing the sensitivity of amphibians and other wetland-dependent species to climate change. Further, long-term monitoring of wetlands in national parks will help reduce uncertainty
surrounding wetland resources and strengthen opportunities to make informed, science-based
decisions that have far-reaching benefits.
temperature, precipitation, and evapotranspiration (i.e., climate drivers) are likely to alter flooding regimes of wetlands and affect the vital rates, abundance, and distributions of wetland-dependent species. Amphibians may be among the most climate-sensitive wetland-dependent groups as many species rely on shallow or intermittently flooded wetland habitats for breeding. Here, we integrated multiple years of high-resolution gridded climate and amphibian monitoring data from Grand Teton and Yellowstone National Parks to explicitly model how variations in climate drivers and habitat conditions affect the occurrence and breeding dynamics (i.e., annual extinction and colonization rates) of amphibians. Our results showed that models incorporating climate drivers outperformed models of amphibian breeding dynamics that were exclusively habitat based. Moreover, climate-driven variation in extinction rates, but not colonization rates, disproportionately influenced amphibian occupancy in monitored wetlands. Long-term monitoring from national parks coupled with high-resolution climate data sets will be crucial to describing population dynamics and characterizing the sensitivity of amphibians and other wetland-dependent species to climate change. Further, long-term monitoring of wetlands in national parks will help reduce uncertainty
surrounding wetland resources and strengthen opportunities to make informed, science-based
decisions that have far-reaching benefits.
News & Stories ARMI scientists Blake Hossack (NOROCK), Brent Sigafus (SBSC) and Erin Muths (FORT), and ARMI post doc Thierry Chambert traveled to Sonora, Mexico, to survey for Sonoran Tiger Salamanders in May 2016
Authors: Erin Muths; Blake R Hossack; Brent H Sigafus
June 23, 2016
ARMI scientists Blake Hossack (NOROCK), Brent Sigafus (SBSC) and Erin Muths (FORT), and ARMI post doc Thierry Chambert traveled to Sonora, Mexico, to survey for Sonoran Tiger Salamanders in May. Reports existed of the presence of this salamander in Sonora, but the spatial extent of its range is unknown. The Sonoran Tiger Salamander is federally endangered in the US and is found only in the San Rafael Valley in southern Arizona. The identification of additional populations in nearby Sonora has implications for multiple conservation concerns including population biology, genetics, and disease. Data collected about its presence and abundance across the border will contribute to the identification of management objectives and subsequent implementation of conservation actions. The surveys were a collaborative effort with logistical support from Naturalia (http://www.naturalia.org.mx/) that included the expertise of Naturalia employees Daniel Toyos and Ramon Babuca. The trip also benefitted from assistance from Guillermo Molina (Instituto Tecnológico Superior De Cananea), Julio Lemos Espinal (UNAM), and students David Hurtado and Aline Estrella. Jim Rorabaugh contributed much to the trip by sharing knowledge of the Sonoran system gained from his previous expeditions focused on salamanders in Mexico. The effort was based at Rancho Los Fresnos, a Naturalia property located north of the town of Cananea and adjacent to the US–Mexico border. The group sampled a variety of sites on Rancho Los Fresnos, as well as surrounding ranches and locations to the south of Cananea. Tiger salamanders reside primarily in man-made or modified earthen stock tanks. These habitats were seined for salamanders and water samples were collected to test for environmental DNA (eDNA) from salamanders, invasive American bullfrogs, federally-threatened (USA) Chiricahua leopard frogs, and pathogens that cause amphibian diseases. Buccal swabs were collected from captured salamanders for genetic analyses (there is uncertainty in determining the difference among closely related salamanders in the field); and skin swabs were collected to test for disease (both Batrachochytrium salamandrivorans and B. dendrobatidis). This ongoing project has already produced one publication (Hossack et al. 2016. Notes on the Distribution of Tiger Salamanders (Presumed Ambystoma mavortium stebbinsi) in Sonora, Mexico. Herpetological Review 47(2): 177-180), and another is in preparation (Hossack et al. Informing recovery of an imperiled, endemic salamander: coupled dynamics and test of drought-mediated coexistence with invasive predators).
Papers & Reports Survival estimates for reintroduced populations of the Chiricahua Leopard Frog (Lithobates chiricahuensis)
Authors: P E Howell; Blake R Hossack; Erin Muths; Brent H Sigafus; Richard Chandler
Date: 2016 | Outlet: Copeia. 104.4: 824-830.
Global amphibian declines have been attributed to a number of factors including disease, invasive species, habitat degradation, and climate change. Reintroduction is one management action that is commonly used with the goal of recovering imperiled species. The success of reintroductions varies widely and evaluating their efficacy requires estimates of population viability metrics, such as underlying vital rates and trends in abundance. Although rarely quantified, assessing vital rates for recovering populations provides a more mechanistic understanding of population growth than numerical trends in population occupancy or abundance. We used three years of capture-mark-recapture data from three breeding ponds and a Cormack-Jolly-Seber model to estimate annual apparent survival for reintroduced populations of the federally-threatened Chiricahua Leopard Frog (Lithobates chiricahuensis) at the Buenos Aires National Wildlife Refuge (BANWR), in the Altar Valley, Arizona, USA. To place our results in context, we also compiled published survival estimates for other ranids. Average apparent survival of Chiricahua Leopard Frogs at BANWR was https://0.27 (95% CI [https://0.07, 0.74]) and average individual capture probability was https://0.02 (95% CI [0, 0.05]). Our apparent survival estimate for Chiricahua Leopard Frogs is lower than for most other ranids, and is not consistent with recent research that showed metapopulation viability in the Altar Valley is high. We suggest that low apparent survival may be indicative of high emigration rates. We recommend that future research should estimate emigration rates so that actual, rather than apparent, survival can be quantified to improve population viability assessments of threatened species following reintroduction efforts.
Papers & Reports Phenotypic plasticity in developmental rate is insufficient to offset high tadpole mortality in rapidly drying ponds
Authors: Staci M Amburgey; M A Murphy; W C Funk
Date: 2016-06 | Outlet: Ecosphere 2016, 00(00):e01386. 10.1002/ecs2.1386
Habitat suitability is strongly regulated by seasonal conditions and stochastic processes, and
this is especially important in temporary aquatic systems that contain organisms with complex life cycles.
We investigated the potential for phenotypic plasticity in timing of and size at metamorphosis to mitigate
effects of altered habitat conditions, specifically shortened hydroperiod (duration of water in ponds)
and altered predator-prey dynamics, in the pond-breeding boreal chorus frog (Pseudacris maculata). We
simulated reduced hydroperiod and concentrated predator cue in the laboratory to understand potential
benefits and costs of plasticity. Tadpoles developed faster in response to the combined effects of reduced
hydroperiod and increased concentration of predator cue, potentially due to reduced conspecific density.
In contrast, there was no effect of reduced hydroperiod or predator cue on size at metamorphosis. Alone,
this result suggests that phenotypic plasticity may allow P. maculata to escape the negative effects of rapidly
drying ponds. However, tadpole survival was significantly lower in reduced hydroperiod treatments
relative to all other treatments, suggesting that even if plasticity acts as a buffer against reduced hydroperiod
by facilitating metamorphosis, heightened mortality may offset benefits of this rapid response. Our
results add to previous studies of plastic responses in amphibians by disentangling the costs and benefits
of plasticity in habitats with multiple, simultaneous stressors. We show that while plasticity may accelerate
metamorphosis, similar, heightened levels of mortality are experienced regardless of plasticity. This
implies that plasticity may not completely buffer populations against the effects of altered habitat conditions,
such as those that occur with climate change or urbanization.
this is especially important in temporary aquatic systems that contain organisms with complex life cycles.
We investigated the potential for phenotypic plasticity in timing of and size at metamorphosis to mitigate
effects of altered habitat conditions, specifically shortened hydroperiod (duration of water in ponds)
and altered predator-prey dynamics, in the pond-breeding boreal chorus frog (Pseudacris maculata). We
simulated reduced hydroperiod and concentrated predator cue in the laboratory to understand potential
benefits and costs of plasticity. Tadpoles developed faster in response to the combined effects of reduced
hydroperiod and increased concentration of predator cue, potentially due to reduced conspecific density.
In contrast, there was no effect of reduced hydroperiod or predator cue on size at metamorphosis. Alone,
this result suggests that phenotypic plasticity may allow P. maculata to escape the negative effects of rapidly
drying ponds. However, tadpole survival was significantly lower in reduced hydroperiod treatments
relative to all other treatments, suggesting that even if plasticity acts as a buffer against reduced hydroperiod
by facilitating metamorphosis, heightened mortality may offset benefits of this rapid response. Our
results add to previous studies of plastic responses in amphibians by disentangling the costs and benefits
of plasticity in habitats with multiple, simultaneous stressors. We show that while plasticity may accelerate
metamorphosis, similar, heightened levels of mortality are experienced regardless of plasticity. This
implies that plasticity may not completely buffer populations against the effects of altered habitat conditions,
such as those that occur with climate change or urbanization.
Papers & Reports Mitigating amphibian chytridiomycosis in nature
Authors: T WJ Garner; Benedikt R Schmidt; An Martel; Frank Pasmans; Erin Muths; A C Cunningham; C Weldon; Matthew C Fisher; Jaime Bosch
Date: 2016-10 | Outlet: Phil. Trans.R.Soc.B 371: 20160207. dx.doi.org/10.1098/rstb.2016.0207
Amphibians across the planet face the threat of population decline and extirpation caused by the disease chytridiomycosis. Despite consensus that the fungal pathogens responsible for the disease are conservation issues, strategies to mitigate their impacts in the natural world are, at best, nascent. Reducing risk associated with the movement of amphibians, non-amphibian vectors and other sources of infection remains the first line of defence and a primary objective when mitigating the threat of disease in wildlife. Amphibian-associated chytridiomycete fungi and chytridiomycosis are already widespread, though, and in this article we discuss options for mitigating the threats once disease emergence has occurred in wild amphibian populations.
News & Stories New Research Confirms Continued, Unabated and Large-Scale Amphibian Declines: Local Action Key to Reversing Losses
Authors: Evan HC Grant
May 24, 2016
LAUREL, Md. -- New U.S. Geological Survey-led research suggests that even though amphibians are severely declining worldwide, there is no smoking gun – and thus no simple solution – to halting or reversing these declines.
“Implementing conservation plans at a local level will be key in stopping amphibian population losses, since global efforts to reduce or lessen threats have been elusive,” said Evan Grant, a USGS research wildlife biologist who led the study published in Scientific Reports today. “This research changes the way we need to think about amphibian conservation by showing that local action needs to be part of the global response to amphibian declines, despite remaining questions in what is causing local extinctions.”
Amphibian declines are a global phenomenon that this new research demonstrates has continued unabated in the United States since at least the 1960's, and which are occurring even in protected national parks and refuges. Scientists have broadly linked declines to environmental factors like climate, human influence such as land-use change, and contaminants and disease, but have not been able to use actual scientific data on a large scale to discern causes of the ongoing disappearance of amphibian populations.
The new study is the first to test this linkage at a continental scale, and finds that the presence and intensity of the four main threats – human influence, disease, pesticide application, and climate change varies substantially across the US. The causes of the declines are more variable – and more locally driven – across the United States than had been assumed.
For example, the research provides evidence that the average decline in overall amphibian populations is 3.79 percent per year, which supports previous USGS-led research findings from 2013 that showed a similar rate of loss, though the new research finds that the decline rate is more severe in some regions, such as the West Coast and the Rocky Mountains. If this rate remains unchanged, these species would disappear from half of the habitats they occupy in about 20 years.
"Losing 3 or 4 percent of amphibian populations might not sound like a big deal but small losses year in and year out quickly lead to dramatic and consequential declines,” said USGS ecologist Michael Adams, a study coauthor and the lead for the USGS Amphibian Research and Monitoring Initiative, which studies amphibian trends and causes of declines.
David Miller, a professor at Penn State University and the lead biometrician in the study, summarized the extent of the effort.
"This study involved a truly comprehensive and collaborative effort to bring together data from researchers across the United States,” Miller said. “We combined nearly half a million actual observations of 84 species across 61 study areas to answer questions about the causes of wide-scale amphibian declines.”
The research, “Quantitative evidence for the effects of multiple drivers on continental-scale amphibian declines,” was led by Evan Grant, USGS; David Miller, Penn State University; Erin Muths, USGS; and 22 others. The study was published in the open-access journal Scientific Reports. Read the full text version here: http://www.nature.com/articles/srep25625
News & Stories Amphibians in the news
Authors: Robert N Fisher
May 24, 2016
This week, our very own eccentric biologist, Robert Fisher, gave an interview on KPCC about amphibian declines in Southern California.
The follow up article was posted online. You can view it here: http://www.scpr.org/news/2016/05/23/60926/california-s-amphibians-threatened-by-climate-chan/
Elsewhere, Evan Grant communicated with VOA News, Field and Stream magazine, and UPI.com in hope of reaching out to the public on the current state of Amphibians.
Their stories can be viewed here: http://www.voanews.com/content/mht-unabated-amphibian-decline-found-to-have-myriad-causes/3342617.html
Here: http://www.fieldandstream.com/blogs/field-notes/new-research-confirms-large-scale-amphibian-die-off
And here: http://www.upi.com/Science_News/2016/05/23/Amphibians-in-continued-global-decline/8341464025350/
Update: One more article to add to the flurry of recent amphibian updates: http://www.natureworldnews.com/articles/22906/20160525/are-amphibians-about-to-go-extinct-the-amphibian-crisis-is-worse-than-you-think.htm
Papers & Reports Using spatial capture-recapture to elucidate population processes and space-use in herpetological studies
Authors: David J Muñoz; David AW Miller; C Sutherland; Evan HC Grant
Outlet: Journal of Herpetology xx:xxx-xxx
Papers & Reports INFORMING RECOVERY OF THE ENDANGERED SONORAN TIGER SALAMANDER: 10-YEAR TRENDS IN OCCUPANCY OF SALAMANDERS, INVASIVE PREDATORS, AND THEIR CO-OCCURRENCE
Authors: Blake R Hossack; R K Honeycutt; Thierry C Chambert; Brent H Sigafus; T R Jones,; J A Sorensen; James C Rorabaugh; Erin Muths
Outlet: Unpublished Report (see https://doi.org/10.1016/j.biocon.2017.03.004)
The Sonoran Tiger Salamander (Ambystoma mavortium stebbinsi) occurs in a single valley that spans the USA-Mexico border and was listed as federally-endangered in 1997. The listing was driven by a variety of threats, including small geographic range and threats from invasive predators. The recovery plan for this subspecies requires scientifically-credible estimates of changes in occurrence of the Sonoran Tiger Salamander and invasive predators before further evaluation of the listing status. The recent completion of a 10-year (2004–2013) monitoring program, coordinated by the Arizona Game and Fish Department and the U.S. Fish and Wildlife Service, generated data sufficient to estimate (1) trends in breeding site occupancy by the Sonoran Tiger Salamander, (2) trends in occupancy of introduced predators, and (3) probability of co-occurrence between Sonoran Tiger Salamanders and invasive predators. We used Bayesian hierarchical models to estimate annual probabilities of occupancy and co-occurrence, after adjusting for imperfect detection. Our analyses showed that pond-level occupancy of Sonoran Tiger Salamanders increased by an estimated 2.2% (95% credible interval [CI] = 0.4%–3.8%) per year. Occupancy of invasive predators decreased by an estimated 0.7% (95% CI = −2.4%–0.7%) per year. In ponds with water, presence of invasive predators reduced salamander occupancy by 23.01% (95% CI = 8.72–43.73) across the 10-yr monitoring program. These results will assist in evaluating the status of the Sonoran Tiger Salamander and prioritizing management actions that are supported by defensible estimates.
Papers & Reports Climate-mediated competition in a high-elevation salamander community
Authors: E A Dallalio; Adrianne B Brand; Evan HC Grant
Outlet: Journal of Herpetology xx:xxx-xxx
The distribution of the federally endangered Shenandoah salamander (Plethodon shenandoah) is presumed to be limited by competition with the red-backed salamander (Plethodon cinereus). In particular, the current distribution of P. shenandoah is believed to be restricted to warmer and drier habitats because of interspecific interactions. These habitats may be particularly sensitive to climate change, though the influence of competition may also be sensitive to temperature and relative humidity. We investigated the response of P. shenandoah to competition with P. cinereus under four climate scenarios in 3-dimensional mesocosms. The results suggest that although climate change may alleviate competitive pressure from P. cinereus, warmer temperatures may also significantly influence the persistence of the species across its known range.
Papers & Reports Potential Interactions Among Disease, Pesticides, Water Quality and Adjacent Land Cover in Amphibian Habitats in the United States
Authors: William A Battaglin; Kelly L Smalling; Chauncey W Anderson; Daniel L Calhoun; T Chestnut; Erin Muths
Date: 2016-05-24 | Outlet: Science of the Total Environment 320-332
To investigate interactions among disease, pesticides, water quality and adjacent land cover we collected samples of water, sediment, and frog tissue from 21 sites in 7 States in the United States (US) representing a variety of amphibian habitats. All samples were analyzed for > 90 pesticides and pesticide degradates, and water and frogs were screened for the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd) using molecular methods. Pesticides and pesticide degradates were detected frequently in frog breeding habitats (water and sediment) as well as in frog tissue. Fungicides occurred more frequently in water, sediment, and tissue than was expected based upon their limited use relative to herbicides or insecticides. Pesticide occurrence in water or sediment was not a strong predictor of occurrence in tissue, but pesticide concentrations in tissue were correlated positively to agricultural and urban land, and negatively to forested land in 2-kilometer buffers around the sites. Bd was detected in water at 45% of sites, and on 34% of swabbed frogs. Bd detections in water were not associated with differences in land use around sites, but sites with detections had colder water. Frogs that tested positive for Bd were associated with sites that had higher total fungicide concentrations in water and sediment, but lower insecticide concentrations in sediments relative to frogs that were Bd negative. Bd concentrations on frog swabs were positively correlated to dissolved organic carbon, and total nitrogen and phosphorus, and negatively correlated to pH and water temperature.
Data were collected from a range of locations and amphibian habitats and represent some of the first field-collected information aimed at understanding the interactions between pesticides, land use, and amphibian disease. These interactions are of particular interest to conservation efforts as many amphibians live in altered habitats and may depend on wetlands embedded in these landscapes to survive.
Data were collected from a range of locations and amphibian habitats and represent some of the first field-collected information aimed at understanding the interactions between pesticides, land use, and amphibian disease. These interactions are of particular interest to conservation efforts as many amphibians live in altered habitats and may depend on wetlands embedded in these landscapes to survive.
Papers & Reports First Estimates of the Probability of Survival in a Small-bodied, High Elevation Frog or, how Historical Data Can Be Useful
Authors: Erin Muths; R Scherer; Staci M Amburgey; T Matthews; A Spencer; P. Stephen Corn
Date: 2016-06 | Outlet: Canadian Journal of Zoology, doi: 10.1139/cjz-2016-0024
In an era of shrinking budgets yet increasing demands for conservation, the value of existing (i.e., historical) data is elevated. Lengthy time-series on common, or previously common, species are particularly valuable and may be available only through the use of historical information. We provide first estimates of the probability of survival and longevity (https://0.67-0.79; 5-7 yr) for a subalpine population of a small-bodied, ostensibly common amphibian, the boreal chorus frog, using historical data and contemporary, hypothesis-driven information-theoretic analyses. We also test a priori hypotheses about the effects of color morph (as suggested by early reports) and of drought (as suggested by recent climate predictions on survival). Using robust mark-recapture models, we find some support for early hypotheses regarding the effect of color on survival, but we find no effect of drought. The congruence between early findings and our analyses highlights the usefulness of historical information by providing raw data for contemporary analyses and context for conservation and management decisions.
Papers & Reports Quantitative evidence for the effects of multiple drivers on continental-scale amphibian declines
Authors: Evan HC Grant; David AW Miller; Benedikt R Schmidt; Michael J Adams; Staci M Amburgey; Thierry C Chambert; Sam S Cruickshank; Robert N Fisher; David E Green; Blake R Hossack; P TJ Johnson; M B Joseph; Tracy A. Rittenhouse; Maureen E Ryan; Hardin J Waddle; Susan C Walls; Larissa L Bailey; Gary M Fellers; Thomas A Gorman; Andrew M Ray; David S Pilliod; S J Price; D Saenz; Erin Muths
Date: 2016-05-23 | Outlet: Scientific Reports xx:xxx-xxx
Since amphibian declines were first proposed as a global phenomenon over a quarter century ago, the conservation community has made little progress in halting or reversing these trends. The early search for a "smoking gun" was replaced with the expectation that declines are caused by multiple drivers. While field observations and experiments have identified factors leading to increased local extinction risk, evidence for effects of these drivers is lacking at large spatial scales. Here, we use observations of 389 time-series of 83 species and complexes from 61 study areas across North America to test the effects of 4 of the major hypothesized drivers of declines. While we find that local amphibian populations are being lost from metapopulations at an average rate of 3.79% per year, these declines are not related to any particular threat at the continental scale; likewise the effect of each stressor is variable at regional scales. This result - that exposure to threats varies spatially, and populations vary in their response - provides little generality in the development of conservation strategies. Greater emphasis on local solutions to this globally shared phenomenon is needed.
Papers & Reports Re-evaluating geographic variation in life-history traits of a widespread Nearctic amphibian
Authors: J M Davenport; Blake R Hossack
Date: 2016 | Outlet: Journal of Zoology 299: 304-310
Animals from cold environments are usually larger than animals from warm environments, which often produces clines in body size. Because variation in body size can lead to trade-offs between growth and reproduction, life-history traits should also vary across climatic gradients. To determine if life-history traits of wood frogs (Rana sylvatica) vary with climate, we examined female and male body length, clutch size, and ovum size from 37 locations across an unprecedented 32° of latitude. In conflict with recent research, body size and ovum size decreased in cold climates and at higher latitudes. Clutch size did not vary with climate or latitude, but reproductive effort (clutch size:female size) did, suggesting selection for a life-history traits that favors maximizing propagule number over propagule size in cold climates. With accelerating climate change that will expose populations to novel environmental conditions, it is important to identify the limits of adaptation, which can be informed by greater understanding of variation in life-history traits.