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Countless species of animals—big game, birds, bats, insects, amphibians, reptiles, and fish—migrate to reach suitable habitats to feed, reproduce, and raise their young. Animal migrations developed over millennia commonly follow migration corridors—unique routes for each species—to move among seasonal habitats. Changes along those corridors, whether from human development (buildings, roads, dams) or from natural disturbances (for example, climate change, drought, fire, flooding, or invasive species), can make them harder to navigate. The U.S. Geological Survey’s Ecosystems Mission Area provides science that assists land managers in mapping, enhancing, protecting, and reconnecting migration corridors critical for diverse fish and wildlife populations that migrate, such as Odocoileus hemionus (mule deer) and Antilocapra americana (pronghorn), trout and salmon, salamanders, tortoises, bats, and Danaus plexippus (monarch butterflies).

Protected areas like national parks are essential elements of conservation because they limit human influence on the landscape, which protects biodiversity and ecosystem function. The role of national parks in conservation, however, often goes far beyond limiting human influence. The U.S. National Park Service and its system of land units contribute substantively to conservation by providing protected lands where researchers can document trends in species distributions and abundances, examine characteristics important for generating these trends, and identify and implement conservation strategies to preserve biodiversity. We reviewed the contribution of U.S. national parks to amphibian research and conservation and highlight important challenges and findings in several key areas. First, U.S. national parks were instrumental in providing strong support that amphibian declines were real and unlikely to be simply a consequence of habitat loss. Second, research in U.S. national parks provided evidence against certain hypothesized causes of decline, like UV-B radiation, and evidence for others, such as introduced species and disease. However, describing declines and identifying causes contributes to conservation only if it leads to management; importantly, U.S. national parks have implemented many conservation strategies and evaluated their effectiveness in recovering robust amphibian populations. Among these, removal of invasive species, especially fishes; conservation translocations; and habitat creation and enhancement stand out as examples of successful conservation strategies with broad applicability. Successful management for amphibians is additionally complicated by competing mandates and stakeholder interests; for example, past emphasis on increasing visitor enjoyment by introducing fish to formerly fishless lakes had devastating consequences for many amphibians. Other potential conflicts with amphibian conservation include increasing development, increased risk of introductions of disease and exotic species with increased visitation, and road mortality. Decision science and leveraging partnerships have proven to be key components of effective conservation under conflicting mandates in national parks. As resource managers grapple with large-scale drivers that are outside local control, public-private partnerships and adaptive strategies are increasing in importance. U.S. national parks have played an important role in many aspects of identifying and ameliorating the amphibian decline crisis and will continue to be essential for the conservation of amphibians in the future.

Protected areas like national parks are essential elements of conservation because they limit human influence on the landscape, which protects biodiversity and ecosystem function. The role of national parks in conservation, however, often goes far beyond limiting human influence. The U.S. National Park Service and its system of land units contribute substantively to conservation by providing protected lands where researchers can document trends in species distributions and abundances, examine characteristics important for generating these trends, and identify and implement conservation strategies to preserve biodiversity. We reviewed the contribution of U.S. national parks to amphibian research and conservation and highlight important challenges and findings in several key areas. First, U.S. national parks were instrumental in providing strong support that amphibian declines were real and unlikely to be simply a consequence of habitat loss. Second, research in U.S. national parks provided evidence against certain hypothesized causes of decline, like UV-B radiation, and evidence for others, such as introduced species and disease. However, describing declines and identifying causes contributes to conservation only if it leads to management; importantly, U.S. national parks have implemented many conservation strategies and evaluated their effectiveness in recovering robust amphibian populations. Among these, removal of invasive species, especially fishes; conservation translocations; and habitat creation and enhancement stand out as examples of successful conservation strategies with broad applicability. Successful management for amphibians is additionally complicated by competing mandates and stakeholder interests; for example, past emphasis on increasing visitor enjoyment by introducing fish to formerly fishless lakes had devastating consequences for many amphibians. Other potential conflicts with amphibian conservation include increasing development, increased risk of introductions of disease and exotic species with increased visitation, and road mortality. Decision science and leveraging partnerships have proven to be key components of effective conservation under conflicting mandates in national parks. As resource managers grapple with large-scale drivers that are outside local control, public-private partnerships and adaptive strategies are increasing in importance. U.S. national parks have played an important role in many aspects of identifying and ameliorating the amphibian decline crisis and will continue to be essential for the conservation of amphibians in the future.

Most translocation efforts are unsuccessful, often for unknown reasons. We assessed factors linked with population persistence for 25 years of translocations of the federally threatened Chiricahua Leopard Frog. Local features were paramount, including habitat, predators, and restoration history. Timing and life stages stocked affected persistence, but rearing environment did not. Two or more translocations produced an approximate 4-yr increase in predicted population persistence.

In Focus: Valenzuela-Sanchez, A., Azat, C., Cunningham, A. A., Delgado, S., Bacigalupe, L. D., Beltrand, J., Serrano, J. M., Sentenac, H., Haddow, N., Toledo, V., Schmidt, B. R., & Cayuela, H. (2022). Interpopulation differences in male reproductive effort drive the population dynamics of a host exposed to an emerging fungal pathogen. Journal of Animal Ecology, XX, XXXX-XXXX. Understanding the nuances of population persistence in the face of a stressor can help predict extinction risk and guide conservation actions. However, the exact mechanisms driving population stability may not always be known. In this paper, Valenzuela-Sanchez et al. (2022) integrate long-term mark-recapture data, focal measurements of reproductive effort, a population matrix model, and inferences on life history variation to reveal differences in demographic response to disease in a susceptible frog species (Rhinoderma darwinii). Valenzuela-Sanchez et al. found that demographic compensation via compensatory recruitment explained the positive population growth rate in their high disease prevalence population whereas the low disease prevalence population did not compensate and thus had decreasing population growth. Compensatory recruitment was likely due to the high probability of males brooding, and the high number of brooded larvae in the high prevalence population compared to low prevalence and disease-free populations. Valenzuela-Sanchez et al. also document faster generation times in the high prevalence population, which may indicate a faster life history that may be contributing to the population’s ability to compensate for reduced survival. Lastly, the authors find a positive relationship between disease prevalence and the number of juveniles in a given population that suggest a possible prevalence threshold when increased reproductive effort may occur. Altogether, their study provides novel support for increased reproductive effort as the pathway for compensatory recruitment leading to increasing population growth despite strong negative effects of disease on adult survival. Their results also caution the overgeneralization of the effects of stressors (e.g., disease) on population dynamics, where context-dependent responses may differ among host populations of a given species.

Increased salinity (sodium chloride; NaCl) is a prevalent and persistent
contaminant that negatively affects freshwater ecosystems. Although
most studies focus on effects of salinity from roads salts (primarily
NaCl), high-salinity wastewaters from energy extraction (wastewaters)
could be more harmful because they contain NaCl and other toxic
components. Many amphibians are sensitive to salinity and their eggs
are thought to be the most sensitive life history stage. However, there
are few investigations with salinity that include eggs and larvae
sequentially in long-term exposures. We investigated the relative effects
of wastewaters from a large energy reserve, the Williston Basin (USA),
and NaCl on northern leopard (Rana pipiens) and boreal chorus
(Pseudacris maculata) frogs. We exposed eggs to salinity and tracked
responses through larval stages (for 24 days). Wastewaters and NaCl
reduced hatching and larval survival, growth, development, and activity
while also increasing deformities. Chorus frog eggs and larvae were
more sensitive to salinity than leopard frogs suggesting species-specific
responses. Contrary to previous studies, eggs of both species were less
sensitive to salinity than larvae. Our ecologically relevant exposures
suggest that accumulating effects can reduce survival relative to starting
experiments with unexposed larvae. Alternatively, egg casings of some
species may provide some protection against salinity. Notably, effects of
wastewaters on amphibians were predominantly due to NaCl rather than
other components. Therefore, findings from studies with other sources of
increased salinity (e.g., road salts) could guide management of
wastewater-contaminated ecosystems, and vice versa, to mitigate
effects of salinization.

The emerging amphibian pathogen Batrachochytrium salamandrivorans (Bsal) is a severe threat to global urodelan (salamanders, newts, and related taxa) biodiversity. Bsal has not been detected, to date, in North America, but the risk is high because North America is one of the global hotspots for urodelan biodiversity. The North American and United States response to the discovery of Bsal in Europe was to take a risk-based approach to preventive management actions, including interim regulations on importation of captive salamanders and a large-scale surveillance effort. Risk-based approaches to decision-making can extend to adaptive management cycles by periodically incorporating new information that reduces uncertainty in an estimate of risk or to assess the effect of mitigation actions which reduce risk directly. Our objectives were to evaluate the effects of regulatory action on the introduction of Bsal to the U.S., quantify how a large-scale surveillance effort impacted consequence risk, and to combine other new information on species susceptibility to re-evaluate Bsal risk to the U.S. Import regulations effectively reduced import volume of targeted species, but new research on species susceptibility suggests the list of regulated species was incomplete regarding Bsal reservoir species. Not detecting Bsal in an intensive surveillance effort improved confidence that Bsal was not present, however, the overall risk-reduction impact was limited because of the expansive area of interest (conterminous United States) and limited time frame of sampling. Overall, the preventive actions in response to the Bsal threat did reduce Bsal risk in the U.S. and we present an updated risk assessment to provide information for adaptive decision-making.

Wetland creation is a common practice to mitigate for the loss of natural wetlands. However, there is still uncertainty about how effectively created wetlands replace habitat provided by natural wetlands. This uncertainty is due in part because post-construction monitoring of biological communities, and vertebrates especially, is rare and typically short-term (< 5 years). We estimated occupancy of 4 amphibian species in 8 created mitigation wetlands, 7 impacted wetlands, and 7 reference wetlands in the Greater Yellowstone Ecosystem in Wyoming, USA. Mitigation wetlands were created to replace wetland habitat that was lost during road construction and ranged in age from 1 to 10 years when sampled. Impacted wetlands were natural wetlands partially filled by road construction and were adjacent to a highway. We sampled for amphibian larvae during 6 summers from 2013 to 2020 and used multi-species occupancy models that estimated detection and occupancy of each of 4 amphibian species to determine how amphibian responses changed over time, especially in mitigation wetlands. Occupancy did not differ between impacted and reference wetlands for any of the 4 amphibian species. Western Toads (Anaxyrus boreas) were most common (although briefly) in created wetlands, and occupancy of Columbia Spotted Frogs (Rana luteiventris), Western Tiger Salamanders (Ambystoma mavortium), and Boreal Chorus Frogs (Pseudacris maculata) was lower in created wetlands than in impacted or reference wetlands. Wetland area was positively associated with occupancy for all 4 species and wetland vegetation cover was positively associated with Boreal Chorus Frog and Columbia Spotted Frog occupancy; these results emphasize the importance of design characteristics when planning mitigation wetlands. The link between wetland age and occupancy was complex and included threshold and quadratic relationships for three of the four species, but only Boreal Chorus Frog occupancy was still increasing slowly at the end of our study. Our results indicate created wetlands did not attain the suitability of impacted and natural wetlands for local amphibians, even several years after construction. The complicated relationships between wetland age and species-specific occupancy illustrate the importance of long-term monitoring in describing population responses to the construction of wetlands as mitigation for wetland loss.

1. The increasing frequency and severity of drought has the potential to exacerbate existing global amphibian declines. However, interactions between drought and coincident stressors, coupled with high interannual variability in amphibian abundances, can mask the extent and underlying mechanisms of drought-induced declines. The application of dynamic occupancy modeling to longitudinal monitoring data estimates the effect of specific variables on population change, providing key insights into potential management strategies for drought resilience.
2. We synthesized a decade (2009 – 2019) of amphibian survey data from multiple monitoring programs across the California Bay Area and used occupancy modeling to estimate the influence of drought, invasive species, and land use on species’ persistence and colonization probabilities. The geographic and temporal scale of our dataset, consisting of 2574 surveys of seven species in 473 ponds, allowed us to quantify regional trends for an entire community of pond-breeding amphibians.
3. An extreme drought from 2012 – 2015 resulted in losses of breeding sites, with 51% of ponds drying in 2014 compared to <10% in non-drought years. Pond drying reduced persistence rates, and nearly every species exhibited reduced occupancy during the drought, with some species (American bullfrogs and California newts) declining by > 25%. Drought reduced occupancy via additional mechanisms beyond habitat loss; for example, lower spring precipitation (an important cue for breeding) was associated with reduced colonization.
4. During drought, native species’ persistence was higher in permanent relative to temporary ponds, even though these sites were also more likely to contain invasive fish and bullfrogs, which generally reduced native amphibian occupancy. Many of these permanent ponds dried during the worst year of drought, leading to extirpations of invasive species that appeared long-lasting. In contrast, native species rebounded quickly with returning rains and showed evidence of full recovery.
5. Synthesis and applications: Despite experiencing one of most severe droughts in a millennium, native species displayed high resilience. Due to longer recovery times by non-native relative to native species, drought presents a valuable management opportunity to remove invaders from key refugia, and we highlight the value of maintaining hydroperiod diversity to promote the persistence of multiple species.

We describe biotic and abiotic factors that interact with field work to contribute to gradients in human-mediated herpetofaunal pathogen transmission (i.e., translocation) risk between sites. Using biotic and abiotic criteria, we identify site conditions that correspond to high risk for pathogen import [to a site] or high risk for pathogen export [from a site] for implementation of enhanced between-site biosecurity procedures to forestall human-mediated pathogen transmission. Our field-site criteria are based on seven contexts of the pathogen (occurrence, habitat), host(s) (occurrence, habitat, species richness), and geography (distance/topography, geopolitical land use) (Table 1). We do not provide an explicit decision tree because site contexts can be complex, and single contexts may be weighted heavily in some biosecurity decisions, warranting case-by-case decisions. A more conceptual decision tree (Fig. 1) about pathogen export or import can be more flexibly applied as site context vary. Our aim is to provide a rapid process to develop a qualitative narrative to support decisions for between-site herpetological disease biosecurity.

North America’s protected lands harbor significant biodiversity and provide habitats where species threatened by a variety of stressors in other environments can thrive. Yet disease, climate change, and other threats are not limited by land management boundaries and can interact with conditions within protected landscapes to affect sensitive populations. We examined the population dynamics of a boreal toad (Anaxyrus boreas) metapopulation at a wildlife refuge in northwestern Montana over a 16-year period (2003-2018). We used robust design capture-recapture models to estimate male population size, recruitment, and apparent survival over time and in relation to the amphibian chytrid fungus, Batrachochytrium dendrobatidis. We estimated female population size in years with sufficient captures. Finally, we examined trends in male and female toad body size and condition. We found no evidence of an effect of disease or time on male toad survival but detected a strong negative trend in recruitment of new males to the population. Estimates of male and female abundance decreased dramatically over time. Body size of males and females was inversely related to estimated population size, consistent with reduced recruitment to replace adults, but body condition of adult males was only weakly associated with abundance. Together, these results describe the demography of a near-extinction event, and point to dramatic decreases in the recruitment of new individuals to the breeding population as the cause of this decline. We surmise that processes related to the restoration of historical hydrology within the refuge adversely affected amphibian breeding habitat, and that these changes interacted with disease, life history, and other factors to restrict the recruitment of new individuals to the breeding population over time. Our results point to challenges in understanding and predicting drivers of population change and highlight that current metrics for assessing population status can have limited predictive ability.

Populations of the western spadefoot (Spea hammondii) in southern California occur in one of the most urbanized and fragmented landscapes on the planet and have lost up to 80% of their native habitat. Orange County is one of the last strongholds for this pond-breeding amphibian in the region, and ongoing restoration efforts targeting S. hammondii have involved habitat protection and the construction of artificial breeding ponds. These efforts have successfully increased breeding activity, but genetic characterization of the populations, including estimates of effective population size and admixture between the gene pools of constructed artificial and natural ponds, has never been undertaken. Using thousands of genome-wide single-nucleotide polymorphisms, we characterized the population structure, genetic diversity, and genetic connectivity of spadefoots in Orange County to guide ongoing and future management efforts. We identified at least 2, and possibly 3 major genetic clusters, with additional substructure within clusters indicating that individual ponds are often genetically distinct. Estimates of landscape resistance suggest that ponds on either side of the Los Angeles Basin were likely interconnected historically, but intense urban development has rendered them essentially isolated, and the resulting risk of interruption to natural metapopulation dynamics appears to be high. Resistance surfaces show that the existing artificial ponds were well-placed and connected to natural populations by low-resistance corridors. Toad samples from all ponds (natural and artificial) returned extremely low estimates of effective population size, possibly due to a bottleneck caused by a recent multi-year drought. Management efforts should focus on maintaining gene flow among natural and artificial ponds by both assisted migration and construction of new ponds to bolster the existing pond network in the region.

1. Fragmentation within urbanized environments often leads to a loss of native species diversity; however, variation exists in responses among-species and among-populations within species.
2. We aimed to identify patterns in species biogeography in an urbanized landscape to understand anthropogenic effects on vertebrate communities and identify species that are more sensitive or resilient to landscape change.
3. We investigated patterns in species richness and species responses to fragmentation in southern Californian small vertebrate communities using multispecies occupancy models and determined factors associated with overall commonness and sensitivity to patch size for 45 small vertebrate species both among and within remaining non-developed patches.
4. In general, smaller patches had fewer species, with amphibian species richness being particularly sensitive to patch size effects. Mammals were generally more common, occurring both in a greater proportion of patches and a higher proportion of the sites within occupied patches. Alternatively, amphibians were generally restricted to larger patches but were more ubiquitous within smaller patches when occupied. Species range size was positively correlated with how common a species was across and within patches, even when controlling for only patches that fell within a species’ range. We found sensitivity to patch size was greater for more fecund species and depended on where the patch occurred within a species’ range. While all taxa were more likely to occur in patches in the warmer portions of their ranges, amphibians and mammals were more sensitive to fragmentation in these warmer areas as compared to the rest of their ranges. Similarly, amphibians occurred at a smaller proportion of sites within patches in drier portions of their ranges. Mammals occurred at a higher proportion of sites that were also in drier portions of their range while reptiles did not differ in their sensitivity to patch size by range position.
5. We demonstrate that taxonomy, life history, range size, and range position can predict commonness and sensitivity of species across this highly fragmented yet biodiverse landscape. The impacts of fragmentation on species communities within an urban landscape depend on scale, with differences emerging among and within species and populations.

Batrachochytrium salamandrovorans (Bsal) is a fungal pathogen that can cause the emerging infectious disease Bsal chytridiomycosis in some amphibians, and is currently causing dramatic declines in European urodeles. To date, Bsal has not been detected in North America but has the potential to cause severe declines in naïve hosts if introduced. Therefore, it is critical that wildlife managers are prepared with effective management actions to combat the fungus. Research has been initiated to identify strategies; however, managers need guidance to prepare for an outbreak until results are available. Here, we conducted a workshop with participants of a Bsal symposium to describe the expected effect of eleven management actions that could be implemented for Bsal in three salamander communities in the northwestern, northeastern, and southeastern United States. Participants expected variation in the proposed management actions to decrease pathogen transmission and increase host survival, but also expected that the selection of a management action may depend on the specific membership of the amphibian community. Collectively, this assessment will help refine research and modeling priorities in an effort to mitigate the risk of Bsal to native U.S. amphibians.

Introduced species often disrupt established food webs, but some native predators can come to rely on introduced prey. Understanding the net effects of the non-natives on imperiled predators is crucial for planning conservation measures. The invasive American bullfrog (Lithobates catesbeianus) can be prey, predator, and competitor for the critically endangered San Francisco garter snake (Thamnophis sirtalis tetrataenia). We examined the seasonal prey use of a San Francisco garter snake population that co-occurs with American bullfrogs to examine intraguild predation between these species. Juvenile and adult snakes mainly consumed native anurans instead of American bullfrogs, and this diet pattern peaked in spring, a critical foraging period for the snakes. In spring, large adult American bullfrogs also foraged heavily on native anurans and displayed a high degree of diet overlap with San Francisco garter snakes. Invasive American bullfrogs are detrimental to San Francisco garter snakes mainly through seasonal competition rather than reciprocal predation. Removal of invasive species provided further evidence that eliminating American bullfrogs can benefit San Francisco garter snakes by reducing predation pressure on their shared amphibian prey. Better understanding the interactions of invasive species with native species of conservation concern informs management practices and improves conservation outcomes.

Biodiversity loss is a major threat to the integrity of ecosystems and is projected to
worsen, yet the path to successful conservation remains elusive. Decision support
frameworks (DSFs) are increasingly applied by resource managers to navigate the
complexity, uncertainty, and differing socio-ecological objectives inherent to
conservation problems. Most published conservation research that uses DSFs focuses
on analytical stages (e.g., identifying an optimal decision), making it difficult to assess
and learn from previous examples in a conservation practice context. Here, we (1)
evaluate the relationship between the application of decision science and the resulting
conservation outcomes, and (2) identify and address existing barriers to the application
of DSFs to conservation practice. To do this, we develop a framework for evaluating
conservation initiatives using decision science that emphasizes setting attainable
goals, building momentum, and obtaining partner buy-in. We apply this framework to a
systematic review of amphibian conservation decision support projects, including a
follow-up survey of the pertinent conservation practitioners, stakeholders, and
scientists. We found that all projects identified optimal solutions to reach stated
objectives, but positive conservation outcomes were limited when implementation
challenges arose. Further, we identified multiple barriers (e.g., dynamic and
hierarchical leadership, scale complexity, limited resource availability) that can inhibit
the progression from decision identification to action implementation (i.e., ‘decision-implementation gap’), and to successful conservation outcomes. Based on these results, we provide potential actionable steps and avenues for future development of DSFs to facilitate the transition from decision to action and the realization of conservation successes.

Populations of pond-breeding amphibians often have boom and bust patterns in recruitment, with large numbers of individuals metamorphosing in some years and few or none in other years. Environmental processes, such as pond freezing and drying, and biological factors (e.g., disease and predator community) can influence survival of early life stages and the probability of complete reproductive failure for amphibian populations. We used multi-state occupancy models to estimate probability of breeding and successful metamorphosis (the complements of reproductive failure), and explored environmental and biological factors influencing these processes.We applied both static and dynamic multistate occupancy modeling techniques to ten years (2001-2010) of boreal toad (Anaxyrus boreas boreas) data from 116 sites, and tested relationships between these probabilities and the presence of a pathogen (Batrachochytrium dendrobatidis), elevation, hydrology, relative snowpack in a given year, and the presence of trout (Onchorhyncus spp., Salvelinus fontinalis, and Salmo trutta). The probability of breeding at a site was influenced by elevation, with higher-elevation sites more likely to support breeding. The probability of metamorphosis, given breeding, was influenced by an interaction between hydrology and relative annual snowpack. The probability of metamorphosis was higher at ephemeral sites in years of relatively high snowpack, while at permanent sites, years of low snowpack lead to higher probabilities of metamorphosis. Across all sites, the probability of metamorphosis was high (0.75) for years with median snowpack levels at sites with recent breeding attempts, but lower (0.25) at newly colonized sites. Our results suggest that boreal toads are well-adapted to their current habitat, with both ephemeral and permanent sites likely to support breeding in years of median snowpack. However shifts in precipitation patterns or temperatures may have negative impacts on this species.

The conservation of biological resources relies on the successful management of ecological and physiological research data. The Western Ecological Research Center of the U.S. Geological Survey is working with researchers, land managers and decision makers from non-government organizations, and city, county, state and federal resource agencies to develop data management methods. Access to the most current and applicable research data available in making sound decisions to conserve species diversity is foundational. We sought to accomplish several goals in developing the data management strategy used in the Multi-Taxa database (MTX). Data persistence and availability are primary goals of well-developed databases. By documenting and sharing the structure and definitions of MTX, we hope to further the successful management of these crucial data.

We used five years of capture mark-recapture data to estimate annual apparent survival of post-metamorphic bullfrogs in a population on the Buenos Aires National Wildlife Refuge in their invaded range in Arizona, U.S.A.