Search ARMI Database

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.

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.

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.

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.

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.

Effective conservation of rare species requires an understanding of how potential threats impact population dynamics. Unfortunately, information about population demographics prior to threats (i.e., baseline data) is lacking for many species. Perturbations, caused by climate change, disease or other stressors can lead to population declines and heightened conservation concerns. A dearth of baseline information challenges our ability to anticipate and respond to agents of population decline. Boreal toads (Anaxyrus boreas boreas) have undergone rangewide declines due mostly to the amphibian chytrid fungus Batrachochytrium dendrobatidis (Bd), with only a handful of sizable populations remaining in the southern Rocky Mountains USA, very few of which are disease-free

Ontogenetic niche shifts (ONS) are important drivers of population and community dynamics, but they can be difficult to identify for species with prolonged larval or juvenile stages, or species that inhabit continuous habitats. Most studies of ontogenetic niche shifts focus on single transitions among discrete habitat patches at local scales. However, for species with long larval or juvenile periods, affinity for particular locations within connected habitat networks may differ among cohorts. The resulting spatial patterns of distribution can result from a combination of landscape-scale habitat structure, position of a habitat patch within a network, and local habitat characteristics – all of which may interact and change as individuals grow. We estimated such spatial ONS for spring salamanders (Gyrinophilus porphyriticus), which have a larval period that can last four years or more. Using mixture models to identify larval cohorts from size-frequency data, we fit occupancy models for each age class using two measures of the branching structure of stream networks, three measures of stream network position. Larval salamander cohorts did indeed have different responses to the position of a site within the network, and the strength of these responses depended on the basin-wide spatial structure of the stream network. The isolation of a site had a stronger effect on occupancy in watersheds with more isolated headwater streams, while the catchment area, which is associated with gradients in stream habitat, had a stronger effect on occupancy in watersheds with more paired headwater streams. Our results show that considering the spatial structure of habitat networks can provide new insights on ontogenetic niche shifts in long-lived species.

We present the first regional trends in anuran occupancy, based on North American Amphibian Monitoring Program (NAAMP) data from thirteen years (2001 to 2013) collected in eight states of the southeastern United States. NAAMP is a long-term monitoring program in which observers collect anuran calling observation data at fixed locations along random roadside routes. We assessed occupancy trends for 14 species. We found that the probability of occurrence for calling anurans within breeding habitats along roads in the southeast declined over the last thirteen years, though none of the 14 species analyzed showed a regional decline with credible intervals that did not include zero. We also assessed state level trends for 107 species/state combinations; of these, 16 showed a decline and 11 showed an increase in occupancy.

Native to the southeastern United States, Southern Watersnakes (Nerodia fasciata) are known from two sites in California, but their ecological impacts are poorly understood. We investigated the ecology of Southern Watersnakes in Machado Lake, Harbor City, Los Angeles County, California, including an assessment of control opportunities. We captured 306 watersnakes as a result of aquatic trapping and hand captures. We captured snakes of all sizes (162–1063 mm snout–vent length [SVL], 3.5–873.3 g), demonstrating the existence of a well-established population. The smallest reproductive female was 490 mm SVL and females contained 12–46 postovulatory embryos (mean = 21). Small watersnakes largely consumed introduced Western Mosquitofish (Gambusia affinis), while larger snakes specialized on larval and metamorph American Bullfrogs (Lithobates catesbeianus) and Green Sunfish (Lepomis cyanellus). Overall capture per unit effort (CPUE) in traps declined with time during an intensive 76-d trapping bout, but CPUE trends varied considerably among traplines and it is unlikely that the overall decline in CPUE represented a major decrease in the snake population size. Although we found no direct evidence that Southern Watersnakes are affecting native species in Machado Lake, this population may serve as a source for intentional or unintentional transportation of watersnakes to bodies of water containing imperiled native prey species or potential competitors.

Most research on the effects of wildfires on water quality in streams has focused on suspended sediment and nutrients in streams and water bodies, and relatively little research has examined the effects of wildfires on trace elements. The purpose of this study was two-fold: 1) to determine the effect of the 2009 Station Fire in the Angeles National Forest northeast of Los Angeles, CA on trace element concentrations in streams, and 2) compare trace elements in post-fire stormflow water quality to criteria for aquatic life to determine if trace elements reached concentrations that can harm aquatic life. Pre-storm and stormflow water-quality samples were collected in streams located inside and outside of the burn area of the Station Fire. Ash and burned soil samples were collected from several locations within the perimeter of the Station Fire. Filtered concentrations of Fe, Mn, and Hg and total concentrations of most trace elements were elevated as a result of the Station Fire. In contrast, filtered concentrations of Cu, Pb, Ni, and Se and total concentrations of Cu were elevated primarily due to storms and not the Station Fire. Total concentrations of Se and Zn were elevated as a result of both storms and the Station Fire. Suspended sediment in stormflows following the Station Fire was an important transport mechanism for trace elements. Cu, Pb, and Zn primarily originate from ash in the sediment. Fe primarily originates from burned soil in the sediment. As, Mn, and Ni originate from both ash and burned soil. Filtered concentrations of trace elements in stormwater samples affected by the Station Fire did not reach levels that were greater than criteria established for aquatic life. Total concentrations for Fe, Pb, Ni, and Zn were detected at concentrations above criteria established for aquatic life.

The California Red-legged Frog (Rana draytonii) is a threatened species in the United States that has undergone population declines, especially in southern California. Due to the lack of information on the status of Mexican populations, we surveyed for the presence of R. draytonii in Baja California and assessed possible threats to population persistence. The two-year study (2013−2014) extended from the U.S.-Mexican border to the southern end of the species distribution in the Sierra San Pedro Mártir. We found R. draytonii at six of 15 historical sites, none of five proxy sites and four of 24 additional sites sites. All 10 occupied sites are confined to three watersheds within the Sierra San Pedro Mártir (two sites at Arroyo San Rafael, two sites at Arroyo San Telmo, and six sites at Arroyo Santo Domingo). Capture rates ranged from 1–11 individuals per visit, with the exception of La Grulla, where the average was 68. Rana draytonii was absent from 9 historical sites, including the highest elevation site at La Encantada and numerous drainages in low-lying coastal areas, suggesting the species is in decline in Baja California. The main threats identified across the study area include presence of exotic animal species, water diversion, and cattle grazing. Management of the remaining populations and local education is needed to prevent further declines.

eSummary(1) Biological monitoring programs are increasingly relying upon large volumes of citizenscience data to improve the scope and spatial coverage of information, ch a l l en g i n g thescientific commun i ty to develop design and model - b ase d approaches to improve inference.(2) Recent statistical models in ecology have be en develope d to accommodate false-negativeerrors, although recent work points to false positive errors as equally important sources ofbias. This is of particular concern for the success of any m o n i t or i n g program given rates assmall as 3% could lead to th e overestimation of the occurrence of rare events by as much as50%, and even small false positive r a t es can severely b i as estimates of occurrence dynamics.(3) We present an int eg ra t ed , comput at i o n al l y efficient Bayesian hierar chical model tocorrect for fal se positi ve and negative error s in detection/no n -d et ec ti o n data. Our modelcombines ind ependent, a u x i l i ar y data sources with field observations to i m p r ove t h eestimation of false positive rate s, when a subset of field observatio n s cannot be validated aposteriori or assumed as per fe ct . We evaluated the performance of the model across arange of occurren ce rates, false positive and negative errors, and quantity of auxil i ar y data.(4) Th e mode l perfor m ed well under all simulated scenario s, and we were able t o identifycritical auxiliary data characteristics which resul t ed in improved infer en ce. We applied ourfalse positive m odel to a large-scale, citizen -sci e n ce monitor i n g program for anurans in theNortheastern U.S., using auxiliary data from an experiment d esi g n ed to estimate falsepositive er r o r rates. Not correcting for false positive ra t es resulted in biased estimates ofoccupancy in 4 of the 10 anu r a n species we an a l y zed , leadin g to an overestima t i on of theaverage number of occupi ed survey routes by as much as 70%.Conclusions. The framework we present for da ta collecti o n and analysis is able toefficiently pr ovide reliable inference for occurrence patterns using data from acitizen-science monitorin g program . However, our approach is ap p l i ca b le to data generatedby any type of research and monit or i n g program , independent of skill level or scale, when effort i s placed on obtaining independent info rma t i on on false positive rates

A newly identified fungal pathogen, <i>Batrachochytrium salamandrivorans</i> (<i>Bsal</i>), is responsible for mass mortality events and severe population declines in European salamanders. The eastern USA has the highest diversity of salamanders in the world and the introduction of this pathogen is likely to be devastating. Although data is inevitably limited for new pathogens, disease risk assessments utilize best available data to inform management decisions. Using characteristics of <i>Bsal</i> ecology, spatial data on imports and pet trade establishments, and salamander species diversity, we identify high risk areas with both a high likelihood of introduction and severe consequences for local salamanders. We predict that the Pacific coast, southern Appalachian Mountains, and mid-Atlantic regions will have the highest relative risk from <i>Bsal</i>. Management of invasive pathogens becomes difficult once they are established in wildlife populations; therefore, import restrictions to limit pathogen introduction and early detection through surveillance of high risk areas are priorities for preventing the next crisis for North American salamanders

Habitat disturbance from stream culverts can affect aquatic organisms by increasing sedimentation or forming barriers to movement. Land managers are replacing many culverts to reduce these negative effects, primarily for stream fishes. However, these management actions are likely to have broad implications for many organisms, including amphibians in small streams. To assess the effects of culverts on movement and survival of Dicamptodon aterrimus, the Idaho giant salamander, we used capture-mark-recapture surveys and measured sediment in 9 streams with 3 culvert types: unimproved culverts, improved culverts, and no culverts. We predicted culverts would increase stream sediment levels, limit movement, and reduce survival of D. aterrimus. We also determined the effect of sediment levels on survival of salamanders, because although sediment is often associated with distribution and abundance of stream amphibians, links with vital rates remain unclear. To estimate survival, we used a spatial Cormack-Jolly-Seber (CJS) model that explicitly incorporated information on movement, eliminating bias in apparent survival estimated from traditional (i.e., non-spatial) CJS models caused by permanent emigration beyond the study area. To demonstrate the importance of using spatial data in studies of wildlife populations, we compared estimates from the spatial CJS to estimates of apparent survival from a traditional CJS model. Although high levels of sediment reduced survival of salamanders, culvert type was unrelated to sediment levels or true survival of salamanders. Across all streams, we documented only 15 movement events between study reaches. All movement events were downstream, and they occurred disproportionately in 1 stream, which precluded measuring the effect of culvert design on movement. Interestingly, although movement was low overall, the variance among streams was high enough to bias estimates of apparent survival compared to true survival. Our results suggest that where sedimentation occurs from roads and culverts, survival of D. aterrimus could be reduced. Though culverts clearly do not completely block downstream movements of D. aterrimus, the degree to which culvert improvements affect movements under roads in comparison to unimproved culverts remains unclear, especially for rare, but potentially important, upstream movements.

Conservation of imperiled species often requires knowledge of vital rates and population dynamics. However, these can be difficult to estimate for rare species and small populations. This problem is further exacerbated when individuals are not available for detection during some surveys due to limited access, delaying surveys and creating mismatches between the breeding behavior and survey timing. Here we use simulations to explore the impacts of this issue using four separate boreal toad (Anaxyrus boreas boreas) populations, representing combinations of logistical access (accessible, inaccessible) and breeding behavior (synchronous, asynchronous). We examine the bias and precision of survival and breeding probability estimates generated by survey designs that differ in effort and timing for these populations.

Decision-analytic models provide forecasts of how systems of interest will respond to management. These models can be parameterized using empirical data, but sometimes require information elicited from experts. When evaluating the effects of disease in species translocation programs, expert judgment is likely to play a role because complete empirical information will rarely be available. We illustrate development of a decision-analytic model built to inform decision-making regarding translocations and other management actions for the boreal toad (Anaxyrus boreas boreas), a species with declines linked to chytridiomycosis caused by Batrachochytrium dendrobatidis (Bd).

Adaptive management provides a useful framework for managing natural resources in the
face of uncertainty. An important component of adaptive management is identifying clear,
measurable conservation objectives that reflect the desired outcomes of stakeholders. A common
objective is to have a sustainable population, or metapopulation, but it can be difficult to quantify
a threshold above which such a population is likely to persist. We performed a Bayesian
metapopulation viability analysis (BMPVA) using a dynamic occupancy model to quantify the
characteristics of two wood frog (Lithobates sylvatica) metapopulations resulting in sustainable
populations, and we demonstrate how the results could be used to define meaningful objectives
that serve as the basis of adaptive management. We explored scenarios involving
metapopulations with different numbers of patches (pools) using estimates of breeding
occurrence and successful metamorphosis from two study areas to estimate the probability of
quasi-extinction and calculate the proportion of vernal pools producing metamorphs. Our results
suggest that >50 pools are required to ensure long-term persistence with approximately 16% of
pools producing metamorphs in stable metapopulations. We demonstrate one way to incorporate
the BMPVA results into a utility function that balances the trade-offs between ecological and
financial objectives, which can be used in an adaptive management framework to make optimal,
transparent decisions. Our approach provides a framework for using a standard method (i.e.,
PVA) and available information to inform a formal decision process to determine optimal and
timely management policies.

Cold environments at high elevation and high latitude are often viewed as resistant to biological invasions. However, climate warming, land use change and associated increased connectivity all increase the risk of biological invasions in these environments. Here we present a summary of the key discussions of the workshop ‘Biosecurity in Mountains and Northern Ecosystems: Current Status and Future Challenges’ (Flen, Sweden, 1-3 June 2015). The aims of the workshop were to (i) increase awareness about the growing importance of species expansion – both non-native and native – at high elevation and high latitude with climate change, (ii) review existing knowledge about invasion risks in these areas, and (iii) encourage more research on how species will move and interact in cold environments, and the consequences for animal and human health and wellbeing. The diversity of potential and actual invaders reported at the workshop and the likely interactions between them create major challenges for managers of cold environments. However, since these cold environments have experienced fewer invasions when compared with many warmer, more populated environments, prevention has a real chance of success, especially if it is coupled with prioritisation schemes for targeting invaders likely to have greatest impact. Communication and co-operation between cold environment regions will facilitate rapid response and maximise use of limited research and management resources.