Search Results

Papers & Reports Effects of experimental warming and nutrient enrichment on wetland communities at the Arctic’s edge
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Authors: Davenport JM, Fishback L, Hossack BR | Date: 2020-09 | Outlet: Hydrobiologia
The disproportionate effects of warming for high-latitude, freshwater ecosystems has been well documented, but in some areas, changes have been further impacted by human-subsidized increases of waterfowl. To gain insight into how predicted changes in temperature and nutrient inputs might affect ecosystem function, we conducted a mesocosm experiment in the Canadian Subarctic with three levels of simulated goose enrichment and warming to measure changes in size and survival of larval wood frogs and boreal chorus frogs and primary productivity (phytoplankton and periphyton biomass). Our results highlight that the consequences of these rapid changes are non-linear and even non-intuitive, with species-specific consumer and ecosystem responses that depend on the magnitude of temperature and nutrient changes as well as community composition.
Field research at Yosemite toad breeding site - Dana Meadows, Yosemite National Park
Field research at Yosemite toad breeding site - Dana Meadows, Yosemite National Park
Sadinski W
Papers & Reports Climate’s cascading effects on disease, predation, and hatching success in Anaxyrus canorus, the threatened Yosemite toad
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Authors: Sadinski W, Gallant A L, Cleaver J E | Date: 2020-09-01 | Outlet: Global Ecology and Conservation | Format: .PDF
The U.S. Fish and Wildlife Service listed Anaxyrus canorus, the Yosemite toad, as federally threatened in 2014 based upon reported population declines and vulnerability to global-change factors. A. canorus lives only in California’s central Sierra Nevada at medium to sub-alpine elevations. Lands throughout its range are protected from development, but climate and other global-change factors potentially can limit populations. A. canorus reproduces in ultra-shallow wetlands that typically hydrate seasonally via melting of the winter snowpack. Lesser snowpacks in drier years can render wetland water volumes and hydroperiods insufficient to allow for successful breeding and reproduction. Additionally, breeding and embryogenesis occur very soon after wetlands thaw when overnight temperatures can be below freezing. Diseases, such as chytridiomycosis, which recently decimated regional populations of ranid species, also might cause declines of A. canorus populations. However, reported studies focused on whether climate interacts with any pathogens to affect fitness in A. canorus have been scarce. We investigated effects of these factors on A. canorus near Tioga Pass from 1996 to 2001. We found breeding subpopulations were distributed widely but inconsistently among potentially suitable wetlands and frequently consisted of small numbers of adults. We occasionally observed small but not alarming numbers of dead adults at breeding sites. In contrast, embryo mortality often was notably high, with the majority of embryos dead in some egg masses while mortality among coincidental Pseudacris regilla (Pacific treefrog) embryos in deeper water was lower. After sampling and experimentation, we concluded that freezing killed A. canorus embryos, especially near the tops of egg masses, which enabled Saprolegnia diclina (a water mold [Oomycota]) to infect and then spread through egg masses and kill more embryos, often in conjunction with predatory flatworms (Turbellaria spp.). We also concluded exposure to ultraviolet-B radiation did not play a role. Based upon our assessments of daily minimum temperatures recorded around snow-off during years before and after our field study, the freezing potential we observed at field sites during embryogenesis might have been commonplace beyond the years of our field study. However, interactions among snow quantity, the timing of snow-off, and coincidental air temperatures that determine such freezing potential make projections of future conditions highly uncertain, despite overall warming trends. Our results describe important effects from ongoing threats to the fitness and abundance of A. canorus via reduced reproduction success and demonstrate how climate conditions can exacerbate effects from pathogens to threaten the persistence of amphibian populations.
Southern California slender salamander ([I]Batrachoseps major[/I]).
Southern California slender salamander (Batrachoseps major).
Chris Brown, U.S. Geological Survey
Papers & Reports Changes in capture rates and body size among vertebrate species occupying an insular urban habitat reserve
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Authors: Stanley TR, Clark RW, Fisher RN, Rochester CJ, Root SA, Lombardo KJ, Ostermann-Kelm SD | Date: 2020-06-29 | Outlet: Conservation Science and Practice 2020;e245. | Format: .PDF
Long-term ecological monitoring provides valuable and objective scientific information to inform management and decision making. In this paper we analyze 22 years of herpetofauna monitoring data from the Point Loma Ecological Conservation Area (PLECA), an insular urban reserve near San Diego, California. Our analysis showed that counts of individuals for one of the four most common terrestrial vertebrates declined, whereas counts for other common species increased or remained stable. Two species exhibited declines in adult body length, whereas biomass pooled over the five most common species increased over time and was associated with higher wet season precipitation. Although the habitat and vegetation at PLECA have remained protected and intact, we suspect that changes in arthropod communities may be driving changes in the abundance, growth, and development of insectivorous lizards. This study underscores the value of long-term monitoring for establishing quantitative baselines to assess biological changes that would otherwise go undetected.

E Muths
Papers & Reports Effects of Snowpack, Temperature, and Disease on Demography in a Wild Population of Amphibians
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Authors: Muths E, Hossack BR, Grant EHC, Pilliod DS, Mosher BA | Date: 2020-06 | Outlet: Herpetologica | Format: .PDF
Understanding the demographic consequences of interactions among pathogens, hosts, and weather conditions is critical in determining how amphibian populations respond to disease and in identifying site-specific conservation actions that can be developed to bolster persistence of amphibian populations. We investigated population dynamics in Boreal Toads relative to abiotic (fall temperatures and snowpack) and biotic (the abundance of another anuran host and disease) characteristics of the local environment in Wyoming, USA. We used capture-recapture data and a multi-state model where state is treated as a hidden Markov process to incorporate disease state uncertainty and assess our a priori hypotheses. Our results indicate that snowpack during the coldest week of the winter is more influential to toad survival, disease transition probabilities, and the population-level prevalence of the amphibian chytrid fungus (Batrachochytrium dendrobatidis) in the spring, than temperatures in the fall or the presence of another host. As hypothesized, apparent survival at low (i.e., <25 cm) snowpack (0.22 [CI: 0.15–0.31]) was lower than apparent survival at high snowpack (90.65 [CI: 0.50–0.78]). Our findings highlight the potential for local environmental factors, like snowpack, to influence disease and host persistence, and demonstrate the ecological complexity of disease effects on population demography in natural environments. This work further emphasizes the need for improved understanding of how climate change may influence the relationships among pathogens, hosts, and their environment for wild animal populations challenged by disease.
Juvenile California newt ([I]Taricha torosa[/I]) from southern California.  The larval stage is very sensitive to rainfall and water availability.
Juvenile California newt (Taricha torosa) from southern California. The larval stage is very sensitive to rainfall and water availability.
USGS
Papers & Reports Amphibian responses in the aftermath of extreme climate events
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Authors: Bucciarelli G M, Clark M, Delaney K S, Riley S P D, Shaffer H B, Fisher R N, Honeycutt R L, Kats L B | Date: 2020-02-25 | Outlet: Scientific Reports 10:3409 | Format: .PDF
Climate change-induced extinctions are estimated to eliminate one in six known species by the end
of the century. One major factor that will contribute to these extinctions is extreme climatic events.
Here, we show the ecological impacts of recent record warm air temperatures and simultaneous peak
drought conditions in California. From 2008–2016, the southern populations of a wide-ranging endemic
amphibian (the California newt, Taricha torosa) showed a 20% reduction to mean body condition and
significant losses to variation in body condition linked with extreme climate deviations. However,
body condition in northern populations remained relatively unaffected during this period. Range-wide
population estimates of change to body condition under future climate change scenarios within the
next 50 years suggest that northern populations will mirror the loss of body condition recently observed
in southern populations. This change is predicated on latter 21st century climate deviations that
resemble recent conditions in Southern California. Thus, the ecological consequences of climate change
have already occurred across the warmer, drier regions of Southern California, and our results suggest
that predicted climate vulnerable regions in the more mesic northern range likely will not provide
climate refuge for numerous amphibian communities.
Papers & Reports A three-pipe problem: dealing with complexity to halt amphibian declines
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Authors: Converse S, Grant EHC | Outlet: Biological Conservation
Natural resource managers are increasingly faced with threats to managed ecosystems that are largely outside of their control. Examples include land development, climate change, invasive species, and emerging infectious diseases. All of these are characterized by large uncertainties in timing, magnitude, and effects on species. In many cases, the conservation of species will only be possible through concerted action on the limited elements of the system that managers can control. However, before an action is taken, a manager must decide how to act, which is ? if done well ? not easy. In addition to dealing with uncertainty, managers must balance multiple potentially competing objectives, often in cases when the management actions available to them are limited. Guidance in making these types of challenging decisions can be found in the practice known as decision analysis. We demonstrate how using a decision-analytic approach to frame decisions can help identify and address impediments to improved conservation decision making. We demonstrate the application of decision analysis to two high-elevation amphibian species. An inadequate focus on the decision-making process, and an assumption that scientific information is adequate to solve conservation problems, must be overcome to advance the conservation of amphibians and other highly threatened taxa.

Papers & Reports A statistical forecasting approach to metapopulation viability analysis
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Authors: Howell PE, Hossack BR, Muths E, Sigafus BH, Chenevert-Steffler A, Chandler RB | Date: 2020 | Outlet: Ecological Applications 2020:e02038
Conservation of at-risk species is aided by reliable forecasts of the consequences of environmental change and management actions on population viability. Forecasts from conventional population viability analysis (PVA) are made using a two-step procedure in which parameters are estimated, or elicited from expert opinion, and then plugged into a stochastic population model without accounting for parameter uncertainty. Recently-developed statistical PVAs differ because forecasts are made conditional on models that are fitted to empirical data. The statistical forecasting approach allows for uncertainty about parameters, but it has rarely been applied in metapopulation contexts where spatially-explicit inference is needed about colonization and extinction dynamics and other forms of stochasticity that influence metapopulation viability. We conducted a statistical metapopulation viability analysis (MPVA) using 11 years of data on the federally-threatened Chiricahua leopard frog to forecast responses to landscape heterogeneity, drought, environmental stochasticity, and management. We evaluated several future environmental scenarios and pond restoration options designed to reduce extinction risk. Forecasts over a 50-yr time horizon indicated that metapopulation extinction risk was <8% for all scenarios, but uncertainty was high. Without pond restoration, extinction risk is forecasted to be 5.6% (95% CI: 0?60%) by year 2060. Restoring six ponds by increasing hydroperiod reduced extinction risk to 1.0% (0 ? 11%) in year 2060. We found little evidence that drought influences metapopulation viability when managers have the ability to maintain ponds that hold water throughout the year and are free of invasive species. Our study illustrates the utility of the spatially explicit statistical forecasting approach to MPVA in conservation planning efforts.
Post-storm remains of an [I]Amphiuma means[/I].
Post-storm remains of an Amphiuma means.
Jamie Barichivich
Papers & Reports Seeking shelter from the storm: Conservation and management of imperiled species in a changing climate.
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Authors: Walls SC, Barichivich WJ, Chandler J, Meade AM, Milinichik M, O'Donnell KM, Owens ME, Peacock T, Reinman J, Wetsch OE | Date: 2019-05-30 | Outlet: Ecology and Evolution 9(12): 7122-7133. | Format: URL
Climate change is anticipated to exacerbate the extinction risk of species whose persistence is already compromised by habitat loss, invasive species, disease, and other stressors. In coastal areas of the southeastern United States, many imperiled vertebrates are vulnerable to hurricanes, which climate models predict to become more severe in the 21st century. Despite this escalating threat, explicit adaptation strategies that address hurricane threats, in particular, and climate change more generally, are largely underrepresented in recovery planning and implementation. Our purpose herein is to provide a basis for stronger emphasis on strategic planning for imperiled species facing the increasing threat of catastrophic hurricanes. Our reasoning comes from observations of short-term environmental and biological impacts of Hurricane Michael, which impacted the Gulf Coast of the southeastern USA in October 2018. During this storm, St. Marks National Wildlife Refuge, located along the northern Gulf of Mexico?s coast in the panhandle region of Florida, experienced storm surge that was 2.3 to 3.3 m above sea level. Storm surge pushed sea water into some ephemeral freshwater ponds used for breeding by the federally-threatened Frosted Flatwoods Salamander (Ambystoma cingulatum). After the storm, specific conductance across all ponds varied from 80 to 23,100 ?S/cm,compared to 75 to 445 uS/cm in Spring 2018. For those overwashed wetlands that were measured in both Spring and Fall 2018, post-hurricane conductance observations averaged nearly 100 times greater than in the previous Spring, setting the stage for varying population responses across this coastal landscape. Importantly, we found live individual flatwoods salamanders at both overwashed and non-overwashed sites, although we cannot yet assess the demographic consequences of this storm. We outline actions that could be incorporated into climate adaptation strategies and recovery planning for imperiled species, like A. cingulatum, that are associated with freshwater coastal wetlands in hurricane-prone regions.
Papers & Reports Managing the trifecta of disease, climate, and contaminants: Searching for robust choices under multiple sources of uncertainty
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Authors: Smalling, KL, Eagles-Smith, CA, Katz, RA, Grant, EHC | Date: 2019-05-30 | Outlet: Biological Conservation 236: 153-161 | Format: .PDF
Amphibian populations are exposed to multiple stressors, with potential for synergistic effects. These synergies can increase uncertainty in our ability to characterize the effects of each stressor and to understand the degree to which their effects interact to impact population processes. This uncertainty challenges our ability to identify appropriate management alternatives. Finding solutions that are robust to these uncertainties can improve management when knowledge is absent or equivocal and identify critical knowledge gaps. Bayesian Belief Networks (BBNs) are probabilistic graphical models that explicitly account for various sources of uncertainty and are used increasingly by environmental practitioners because of their broad applicability to ecological risk assessments. BBNs allow the user to: 1) generate a conceptual model to link actions to outcomes, 2) use a variety of source data (empirical or expert opinion), 3) explore robust management strategies under uncertainty, 4) use sensitivity analysis to identify opportunities for developing new management actions, and 5) guide the design of data collection for monitoring to improve management decisions. BBNs contribute considerably to environmental research and management because they are transparent and treat uncertainty explicitly. Because of the high level of uncertainty in stressor response, we developed a BBN to conceptually evaluate the effects of potential management actions on amphibian populations exposed to disease, environmental contaminants, and increasingly frequent and severe droughts
Papers & Reports Timing of first and last calls and median calling peaks for Pseudacris crucifer, and of the first call for Hyla chrysoscelis/versicolor, at six wetlands in the St. Croix National Scenic Riverway from 2008-2012
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Authors: Sadinski W, Roth M | Date: 2018-09-06 | Outlet: U.S. Geological Survey data release, https://doi.org/10.5066/F7CR5SBH.
To better understand relations of annual calling phenophases for Pseudacris crucifer, and of the first calls of the season for Hyla chrysoscelis/versicolor, to the timing of the start of the calling season, we compared these dynamics for six wetlands in the St. Croix National Scenic Riverway from 2008 to 2012. We installed an acoustic recorder at each site prior to the start of each calling season and programmed it to record for five minutes at the top of every hour until late summer. We then used the Songscape option in Songscope software to generate annual summaries of all acoustic files recorded at each site. We created contour plots of the summarized median dB values across bandwidths in each recording and then assessed individual calls and calling peaks by visually examining these plots to identify first (and last) calls via the unique call signatures for these two species. We examined individual five-minute recordings aurally and visually as necessary when sound images represented on the contour plots were confounded and to ensure that the calling peaks described below were dates when calling activity was relatively intense. We also determined the daily median dB levels for frequencies across 2900 to 3200 Hz during 2100 to 2300 h, the bandwidth that typically encompassed the primary energy peak in P. crucifer calls and a time period during which P. crucifer typically called most consistently throughout their calling season. We did this for each day from the date when P. crucifer first called during each year to the date when they last called during each year. Because calling activity could vary from one hour to the next, we integrated the area under the curve for the daily median dB levels from 2900 to 3200 Hz during 2100 to 2300 h. We removed dates when overlapping sounds from storms or other sources rendered comparisons to calls of P. crucifer inaccurate. We used the resultant set of integrands to represent the relative sound intensity (as an indicator of calling activity) for P. crucifer across those hours for each date. We then used these integrands to determine the three highest peak calling dates for this species and used the median of those three dates as the overall median peak date for each site in each year.