Imperiled Species Research Articles

Creating a systematic prioritization of stream reaches for conservation of aquatic species

AbstractHuman impacts on aquatic ecosystems have resulted in systemic declines of global freshwater species abundance and richness. Conservation and governmental groups worldwide have designated protected areas to preserve the remaining diversity. The biodiversity hotspot approach, which designates areas based on high levels of species richness, has been useful for identifying areas to protect both terrestrial and aquatic species. However, for freshwater species, additional approaches are warranted to identify specific stream reaches for protection and/or restoration. To address this issue, we present a methodology to create a Gridded River Identification System (GRIS) for river segments based on 30 arc‐second grids (~0.9 km) using the USGS National Hydrography High Resolution Dataset. To demonstrate the utility of this approach, we obtained occurrence data for six imperiled freshwater mussel species in Texas and created ensemble species distribution models (ESDMs) based on climate and topographical variables. Predicted occupancies were overlayed onto the GRIS in Texas. The predicted occupancies were rank ordered from 1 to 5, with 1 being the lowest probability of occupancy and 5 being the greatest. The rank‐ordered segments were then used to identify reaches for conservation and restoration activities. Our approach is novel and widely applicable to other freshwater species so long as distribution information is available. The GRIS can also be easily developed for stream systems outside of the current study area. Future studies could build upon our framework by incorporating additional taxa data and projected changes in climate and land use.

Evaluating long‐term introduction success of the Florida scrub endemic Crotalaria avonensis (Fabaceae) using a decade of demographic data

Introductions are a critical tool in the recovery of many imperiled species, yet adequate evaluation and development of best practices has lagged. Importantly, long‐term post‐introduction data are typically lacking, as well as suitable comparisons to wild populations to provide a baseline against which to assess performance. Here, we report on three experimental introductions of Crotalaria avonensis (Fabaceae), a federally endangered perennial herb that is narrowly endemic to scrub of the Lake Wales Ridge in peninsular Florida, U.S.A. We synthesize 10 years of post‐introduction monitoring at both the introduced and a nearby, protected wild population to (1) develop best practices for conservation, and (2) evaluate the success of the introduction. First, our study identified best practices that included using transplants propagated from stem cuttings, as well as several factors that may increase seed germination such as habitat choice, seed burial, and litter addition. Second, during the 10 years following the introduction, population density in the introduced population was higher than in a nearby protected, wild population, and a comparison of vital rates revealed that this result was due to relatively high clonal and seedling recruitment rates in the introduced population. Furthermore, the source population, which occurred on unprotected lands, precipitously declined during this time period, further highlighting the importance of safeguarding plants from that population. We report that a new, growing population of C. avonensis has been established to date, with important implications for the species' conservation as well as how introductions are evaluated.

Size-mediated competitive interactions between an invasive and an imperiled crayfish may explain extirpation of the imperiled species

Size-mediated competitive interactions between an invasive and an imperiled crayfish may explain extirpation of the imperiled species

Seasonal variation in thermal tolerance and hypoxia tolerance of a threatened minnow and a non-imperilled congener: a cautionary tale for surrogate species in conservation.

Freshwater organisms face multiple threats to their ecosystems, including warming associated with climate change and low dissolved oxygen (environmental hypoxia), which are both increasing in frequency and extent in freshwater systems. Understanding tolerance thresholds for these environmental stressors as well as the plasticity of responses is the key for informing the conservation of imperilled species. Direct measurement of imperilled species can be difficult, and the use of surrogate (non-imperilled but closely related) species has been proposed as a remedy, but the degree to which surrogate data are representative of the imperilled species has not been widely validated. In this study, we measured physiological performance of two species: one federally listed as Threatened in Canada (Pugnose Shiner, Miniellus anogenus) and a non-imperilled congener (Blackchin Shiner, Miniellus heterodon). Hypoxia tolerance (critical oxygen tension and loss of equilibrium) and upper thermal tolerance (CTmax) were measured streamside over a period of 5 months. We found that the Threatened Pugnose Shiner had lower tolerance to both elevated temperature and hypoxia than the non-imperilled Blackchin Shiner. The species also differed in their responses to environmental dissolved oxygen (DO). CTmax of Pugnose Shiner had a positive relationship with DO such that CTmax was lowered when environmental DO was low, whereas there was no effect of DO on CTmax of Blackchin Shiner. Blackchin Shiner also showed plasticity of hypoxia tolerance in response to changes in environmental DO, while Pugnose Shiner showed little plasticity. We conclude that Pugnose Shiner may be more sensitive to heat waves and hypoxia associated with climate change. We also assert that researchers should be cautious when using surrogate species to inform tolerance limits of imperilled species and highlight the value of measuring imperilled species directly when possible.

Chytrid infections exhibit historical spread and contemporary seasonality in a declining stream-breeding frog.

Species with extensive geographical ranges pose special challenges to assessing drivers of wildlife disease, necessitating collaborative and large-scale analyses. The imperilled foothill yellow-legged frog (Rana boylii) inhabits a wide geographical range and variable conditions in rivers of California and Oregon (USA), and is considered threatened by the pathogen Batrachochytrium dendrobatidis (Bd). To assess drivers of Bd infections over time and space, we compiled over 2000 datapoints from R. boylii museum specimens (collected 1897-2005) and field samples (2005-2021) spanning 9° of latitude. We observed a south-to-north spread of Bd detections beginning in the 1940s and increase in prevalence from the 1940s to 1970s, coinciding with extirpation from southern latitudes. We detected eight high-prevalence geographical clusters through time that span the species' geographical range. Field-sampled male R. boylii exhibited the highest prevalence, and juveniles sampled in autumn exhibited the highest loads. Bd infection risk was highest in lower elevation rain-dominated watersheds, and with cool temperatures and low stream-flow conditions at the end of the dry season. Through a holistic assessment of relationships between infection risk, geographical context and time, we identify the locations and time periods where Bd mitigation and monitoring will be critical for conservation of this imperilled species.

Interactive effects of sedimentary turbidity and elevated water temperature on the Pugnose Shiner (Miniellus anogenus), a threatened freshwater fish.

High turbidity and elevated water temperature are environmental stressors that can co-occur in freshwater ecosystems such as when deforestation increases solar radiation and sedimentary runoff. However, we have limited knowledge about their combined impacts on fish behaviour and physiology. We explored independent and interactive effects of sedimentary turbidity and temperature on the swimming activity and both thermal and hypoxia tolerance of the Pugnose Shiner (Miniellus anogenus, formerly Notropis anogenus), a small leuciscid fish listed as Threatened under Canada's Species at Risk Act (SARA). Fish underwent a 15-week acclimation to two temperatures (16°C or 25°C) crossed with two turbidities (~0 NTU or 8.5 NTU). Swimming activity was measured during the first 8weeks of acclimation. Fish in warm water were more active compared to those in cold water, but turbidity had no effect on activity. Behavioural response to hypoxia was measured after 12weeks of acclimation, as the oxygen level at which fish used aquatic surface respiration (ASR). Fish in warm water engaged in ASR behaviour at higher oxygen thresholds, indicating less tolerance to hypoxia. Turbidity had no effect on ASR thresholds. Finally, thermal tolerance was measured as the critical thermal maximum (CTmax) after 13-15weeks of acclimation. Acclimation to warm water increased fish CTmax and Tag (agitation temperature) but reduced the agitation window (°C difference between Tag and CTmax) and thermal safety margin (°C difference between the acclimation temperature and CTmax). Furthermore, fish in warm, turbid water had a lower CTmax and smaller thermal safety margin than fish in warm, clear water, indicating an interaction between turbidity and temperature. This reduced thermal tolerance observed in Pugnose Shiner in warm, turbid water highlights the importance of quantifying independent and interactive effects of multiple stressors when evaluating habitat suitability and conservation strategies for imperilled species.

Ground spiders (Chelicerata, Araneae) of an urban green space: intensive sampling in a protected area of Rome (Italy) reveals a high diversity and new records to the Italian territory.

Urbanisation is a rapidly growing global phenomenon leading to habitat destruction, fragmentation and degradation. However, urban areas can offer opportunities for conservation, particularly through the presence of green spaces which can even provide important habitats for imperilled species. Spiders, which play crucial roles in ecosystem functioning, include many species that can successfully exploit urban environments. Placed in the middle of the Mediterranean global biodiversity hotspot, Italy possesses an exceptionally rich spider fauna, yet comprehensive data on urban spider communities are still limited. More information on urban spiders in Italy would be extremely beneficial to support conservation efforts, especially in central and southern Italy, where knowledge on the spider fauna is largely incomplete. The current study focused on the spider diversity of a large protected area (Appia Antica Regional Park) in urban Rome, Italy. A total of 120 spider species belonging to 83 genera and 28 families were identified, with 70 species being new records to the Province of Rome, 39 to the Latium Region and two (Pelecopsisdigitulus Bosmans & Abrous, 1992 and Palliduphantesarenicola (Denis, 1964)) to Italy.Forty-one species were recorded during autumn/winter sampling and 107 in spring/summer. The spider fauna recorded from the study area included about 37% of the total spider fauna known from the Province of Rome, 28% of that of the Latium Region and 7% of the entire Italian territory. The most represented families in terms of species richness were Gnaphosidae and Linyphiidae, which accounted for more than 40% of the sampled fauna. Lycosidae were the most abundant family (29% of captured individuals), followed by Zodariidae (16% of captured individuals), Linyphiidae (13% of captured individuals) and Gnaphosidae (7.5% of captured individuals). From a biogeographical point of view, most of the collected species belonged to chorotypes that extend for large areas across Europe and the Mediterranean. The research highlights the role of urban green spaces as refuges for spiders and the importance of arachnological research in urban areas as sources of information on spider biodiversity at larger scales.

Why new scientific information is important for native fish conservation: A case study from the humpback chub (Gila cypha) in the Grand Canyon, U.S.A.

Abstract Habitat descriptions found in critical habitat designations and recovery plans are important for protecting endangered species. However, in order to protect critical habitat, it is necessary to update descriptions of habitat use when range shifts occur or new studies change the understanding of habitat use. This study examined the habitat use of a threatened desert fish to determine whether current habitat use matched the descriptions in recovery documents. Recovery documents describe humpback chub (Gila cypha) as being dependent on rocky, canyon‐bound habitats during all life stages, but recent surveys found humpback chub in open, silt‐laden habitats, suggesting this species may be able to occupy a wider range of habitats. Hoop net catch data from a long‐term monitoring project in the Colorado River were used to compare catches of two size classes: juvenile/subadult (<200 mm total length [TL]) and adult humpback chub (≥200 mm TL). Catch information was analysed on an individual net scale and on a geological segment scale using generalized linear mixed models. There was no difference in juvenile/subadult humpback chub catch between hoop nets set in rocky habitat compared with habitat with only fine sediment. Humpback chub catch for all life stages in a river segment characterized by silt banks exceeded or was not significantly different from catch in rocky segments. This case study demonstrates the importance of revisiting habitat descriptions, sampling in areas outside known or expected habitat and incorporating new data related to range expansion or habitat changes in recovery strategies to better describe and protect habitats that can support imperilled species.

English

Abstract Comprehensive surveys are critical to conserve and monitor crayfish communities, imperiled species, and detect crayfish invasions. The Missouri portion of the North Fork White River drainage (MONFWR) was never comprehensively surveyed, but adjacent drainage surveys suggested it could harbor species of conservation concern (SOCC). We surveyed the MONFWR to determine crayfish species richness, distributions of potential SOCC, and potential invasive species. We included recent sampling of the Arkansas portion of the drainage for a more holistic assessment of the entire drainage. We examined potential changes in crayfish communities after three decades at 22 previously sampled MONFWR locations. We also collected the first habitat association data for the endemic, Faxonius longidigitus. We detected eight taxa; none that were not known from the drainage. Faxonius neglectus chaenodactylus and Cambarus hubbsi were SOCC; F. n. chaenodactylus was common and abundant in the MONFWR; C. hubbsi was detected at only one site in Arkansas. Faxonius neglectus neglectus and Faxonius virilis were each detected only once and are likely introduced. Intermittent streams harbored diversity and abundance rivaling perennial segments. We observed no notable temporal differences between 22 historical and current samples. Faxonius longidigitus, detected at few sites in low numbers, was associated with deeper waters and larger substrates.

Coastal dry tropical forests in Florida and the Caribbean in peril: A review

AbstractCoastal dry tropical forests (CDTFs) are important yet vulnerable ecosystems. In this paper, we highlight the special conservation issues facing CDTFs by focusing on one variant of the type, those that occupy limestone substrate in the northeastern Caribbean. Our analysis draws largely from the coastal terrestrial broadleaf forests of the northern Bahamas, the Florida Keys, and southwestern Puerto Rico. Based on the surveys of storm surge recorded during major hurricanes during the last 50 years, we define CDTFs as coastal terrestrial broadleaf forests on ground surfaces elevated up to 5 m above sea level and occurring within 5 km of the coast. These forests are not only threatened by land‐use change from urbanization but also climate‐driven sea level rise (SLR) and hurricanes, which have degraded them and reduced their extent. CDTFs are distinguished from other dry tropical forests by the occasional influence of marine water incursion during periodic storms, requiring species common to these forests to have some level of salt tolerance despite experiencing well‐drained, fresh water conditions during most of their life span. With precipitation being the sole freshwater source for most CDTFs, SLR and the resulting salinization in the rooting zone subjects these forests to increasingly stressful conditions. Hence, even a modest rise in sea level can push numerous imperiled and endangered species and coastal terrestrial broadleaf communities to the edge of their tolerance, causing a decline in extent or their complete disappearance. Outside of protected areas, rapid urbanization has fragmented these forests and reduced their extent, which in turn have modified the interaction between rising seas and forest function. This work emphasizes the need for refined risk assessments to be completed and for conservation measures to be enforced so that resources can be directed appropriately to prevent further loss of CDTFs.Abstract in Spanish is available with online material.

Prioritizing Imperiled Native Aquatic Species for Conservation Propagation

Abstract Native aquatic species are in decline, and hatcheries can play an important role in stemming these losses until larger ecological issues are addressed. However, as more federal and state agencies face budget uncertainty and the number of imperiled species increases, it is necessary to develop a tool to prioritize species for conservation propagation. Our objective was to create prioritized lists of aquatic species that may benefit from conservation propagation for five states in the United States. Biologists developed an influence diagram and provided information for multiple attributes affecting prevalence of species. The influence diagram and information for each species was used in a Bayesian belief network to generate a score to prioritize propagation of a species and the feasibility of propagation. When all taxa were ranked together within a state, mussels, amphibians, and a crustacean were included among fishes in the top species that may benefit from propagation. We recognize that propagation is one tool for conservation of imperiled species and that additional factors will need to be addressed to ensure species persistence. Nevertheless, we contend our quantitative approach provides a useful framework for prioritizing conservation propagation.

Hawksbill and green turtle niche overlap in a marine protected area, US Virgin Islands

Studying how species interact with their environment and other co-occurring species are 2 main aspects of ecology. For marine turtles, ocean currents drive migratory routes and may determine the location of surrounding foraging grounds. As a result, circumglobal species like the hawksbill turtle Eretmochelys imbricata and green turtle Chelonia mydas adapt to diverse foraging habitats and employ varied feeding strategies. Dietary specializations may reduce competition for available food and space resources between co-occurring hawksbill and green turtles in US Virgin Island shallow reef habitats. This study analyzed isotopic data from immature hawksbill (n = 49; range: 18.7-49.8 cm straight carapace length [SCL]) and green turtles (n = 225; range: 24.1-69.4 cm SCL) to examine foraging niche. We used nitrogen stable isotope (δ15N) values as an indicator of trophic positioning and carbon stable isotope (δ13C) values as a habitat variable. Turtles were hand-captured across an 8 yr period (2012-2019), which facilitated the distinction of isotopic patterns in both the environment and among individual turtles. Understanding variations in habitat, community dynamics, and dietary consumption allowed us to utilize a 5 point framework to translate isotopic space to foraging niche. We found that the site’s relatively stable environmental conditions allow for isotopic overlap between hawksbill and green turtles despite the specialized feeding strategies each species employs. We also underscore the need to evaluate species-specific tissue turnover estimates as evidenced by the influence of tropical storms on recaptured turtle isotopic signatures. These findings inform our understanding of resource use for these imperiled species at our study site and are useful for future global isotopic comparisons.

Military training in the Canadian Pacific: Taking aim at critical habitat or sufficient mitigation of noise pollution impacts?

The Canadian Department of National Defence (DND) has approved the resumption of military activities within ‘Whiskey Hotel’, a 330 km2 area in the Strait of Juan de Fuca that overlaps the critical habitat of endangered Southern Resident Killer Whales in the northeast Pacific Ocean. Multiple Canadian and United States defense organizations use the area for training. The renewal of small-arms training follows a three-year cessation self-imposed by DND to allow a third-party consultant to investigate the risk in-air and underwater training noises pose to marine mammals. Here, we summarize the findings and limitations of the commissioned report and discuss the broader implications for mitigating aquatic noise pollution. The report evaluated the potential for marine mammals to experience injury, behavioral disturbances, and acoustic masking, and proposed mitigation measures (e.g., avoidance zones) to limit impacts. However, the narrow scope of the commissioned report prevented the investigation of the potential effects on non-mammalian taxa and the inclusion of vessel noise generated during training. Resuming military activities within the habitats of imperiled species is contentious among stakeholders. Nevertheless, the DND’s approach to examining noise pollution employs at least two of the precautionary principle’s four components, and their decision to commission a third-party investigation and implement mitigation strategies represents a framework rarely applied when evaluating the impacts of pollutants. The importance of this approach is magnified given the absence of federal underwater noise regulations, the pending development of Canada’s Ocean Noise Strategy, and multiple nations seeking to balance industrial and military activities with environmental stewardship.

DNA metabarcoding reveals consumption of diverse community of amphibians by invasive wild pigs (Sus scrofa) in the southeastern United States

Invasive wild pigs (Sus scrofa) are one of the most widespread, destructive vertebrate species globally. Their success can largely be attributed to their generalist diets, which are dominated by plant material but also include diverse animal taxa. Wild pigs are demonstrated nest predators of ground-nesting birds and reptiles, and likely pose a threat to amphibians given their extensive overlap in wetland use. DNA metabarcoding of fecal samples from 222 adult wild pigs culled monthly from 2017 to 2018 revealed a diverse diet dominated by plant material, with 166 plant genera from 56 families and 18 vertebrate species identified. Diet composition varied seasonally with availability for plants and was consistent between sexes. Amphibians were the most frequent vertebrate group consumed and represented the majority of vertebrate species detected, suggesting amphibians are potentially vulnerable to predation by wild pigs in our study region. Mammal, reptile, and bird species were also detected in pig diets, but infrequently. Our results highlight the need for research on the impacts of wild pigs on amphibians to better inform management and conservation of imperiled species.

The Influence of Tide, Wind, and Habitat on the Abundance and Foraging Rate of Three Species of Imperiled Plovers in Southwest Florida, USA.

Piping Plover (Charadrius melodus), Snowy Plover (Charadrius nivosus), and Wilson's Plover (Charadrius wilsonia) are imperiled species that overlap in both their range and habitat outside the breeding season. The purpose of this research was to document the abundance of these species at a barrier island in Southwest Florida, USA, and to examine the influence of tide and wind on both their abundance and foraging. We walked ~700 m surveys through tidal mudflat and adjacent beach semiweekly at 0730-1030 from 24 September 2021-4 March 2022. During these 38 surveys, Piping Plovers were the most abundant of the three species, and the average number counted was 34 (SD 17.3) compared with 11 (SD 6.3) Snowy Plovers and 14 (SD 14.1) Wilson's Plovers. All of the species were more likely to be found on the mudflats during low tides and the beach during high tides. Our findings suggest the high densities of Piping, Snowy, and Wilson's Plover are due to a mudflat habitat that provides high availability of prey, a beach habitat that provides a relatively safe location to roost, and the context of the barrier island, which is surrounded by other suitable habitats. While each species used the barrier island's habitats slightly differently, the high densities of all three species present an opportunity to have a large conservation impact by protecting this dynamic area.

Effects of forest management on private lands in West Virginia on Cerulean Warblers (Setophaga cerulea) and the avian community

The USDA Natural Resources Conservation Service (NRCS) supports private lands conservation projects across the United States to benefit imperiled focal wildlife species using conservation practices to restore habitat. The Cerulean Warbler Appalachian Forestland Enhancement Project (CWAFEP) was initiated in 2015 to help stabilize or reverse Cerulean Warbler population declines by using forest management to create or enhance breeding habitat on private lands in Appalachian focal areas. We evaluated Cerulean Warbler occupancy on CWAFEP sites treated using NRCS conservation practices to inform adaptive management strategies. We also assessed associated forest focal species’ occupancy and species richness of avian guilds to evaluate the effects of conservation practice implementation on the avian community. We conducted point count surveys at 194 locations on 21 private properties enrolled in the CWAFEP in West Virginia during May – July 2019 and 2020. We compared occupancy among four treatments: reference, pre-treatment, 1-year post-treatment, and 2 – 4 years post-treatment sites. To examine how vegetation structure changes among treatments affected occupancy, we also collected and included vegetation variables. Cerulean Warbler occupancy estimates were not different among treatments, suggesting that post-treatment study sites surveyed did not achieve their goal of increasing Cerulean Warbler occupancy. Cerulean Warbler occupancy decreased by 91 % as elevation increased from 200 to 800 m and increased by 397 % as sapling cover increased from 0 to 100 %. Occupancy for three forest focal species (Blue-gray Gnatcatcher, Eastern Wood-pewee, and Scarlet Tanager) and species richness of four avian guilds also were not different among treatments. Thus, Cerulean Warbler occupancy and selected avian community demographics were not related to recent conservation practice implementation in the short-term (1 – 4 years post-treatment), but there are opportunities to improve NRCS conservation practice implementation for more effective Cerulean Warbler conservation. We suspect that the lack of differences in occupancy and species richness estimates was due to site selection related to ecoregion, small treatment areas, and challenges associated with private lands conservation efforts resulting in insufficient reduction in basal area. If NRCS conservation practices implemented through CWAFEP are going to help reverse Cerulean Warbler population declines, CWAFEP sites need to achieve the recommended basal area range of ∼ 9.2 – 20.7 m 2/ha (40 – 90 ft2/ac) during contract implementation. Our conclusions are critical to updating our knowledge for Cerulean Warbler best management practices and informing future regional conservation implementation.

Oxygen consumption of sexually mature adult, first‐feeding larval, and yearling Pacific Lampreys

AbstractObjectiveThe Pacific Lamprey Entosphenus tridentatus is considered a first food of Native American tribes, such as the Confederated Tribes of the Umatilla Indian Reservation. Populations of this imperiled species have declined such that harvest for traditional use is limited. As a result, propagation and culture of Pacific Lampreys have been initiated to supply animals for restoration and recovery efforts. These efforts require transport and periodic holding of both adults and larvae under static (no‐flow) conditions. Hence, guidelines for ensuring an adequate oxygen supply are needed for all life stages of this species.MethodsWe measured oxygen consumption rates of mature adults, first‐feeding larvae, and yearlings under static conditions at 12–15°C. In addition, we recorded indicators of stress during hypoxia for adults and estimated routine respiration rates during and after larval feeding.ResultAdults exhibited surprisingly high metabolic rates when at rest in static chambers. At 12°C, a single adult typically reduced dissolved oxygen levels in 10 L to <2 mg/L in just 90 min (oxygen consumption rates of 100–200 mg/kg/h). Adults often started to climb the walls of open chambers when dissolved oxygen levels approached 2 mg/L, allowing them to raise their branchiopores into air. Larvae remained quiescent, even when oxygen levels dropped below 1 mg/L, and costs of feeding increased routine respiration by 22–56%.ConclusionBased on these observations, we recommend that adult Pacific Lampreys always be transported in aerated containers and with access to air at the top of the tank. Although larvae exhibited hypoxia tolerance, care should be taken to ensure adequate oxygen availability, particularly during and immediately after feeding.

Broad-Scale Assessment of Methylmercury in Adult Amphibians.

Mercury (Hg) is a toxic contaminant that has been mobilized and distributed worldwide and is a threat to many wildlife species. Amphibians are facing unprecedented global declines due to many threats including contaminants. While the biphasic life history of many amphibians creates a potential nexus for methylmercury (MeHg) exposure in aquatic habitats and subsequent health effects, the broad-scale distribution of MeHg exposure in amphibians remains unknown. We used nonlethal sampling to assess MeHg bioaccumulation in 3,241 juvenile and adult amphibians during 2017-2021. We sampled 26 populations (14 species) across 11 states in the United States, including several imperiled species that could not have been sampled by traditional lethal methods. We examined whether life history traits of species and whether the concentration of total mercury in sediment or dragonflies could be used as indicators of MeHg bioaccumulation in amphibians. Methylmercury contamination was widespread, with a 33-fold difference in concentrations across sites. Variation among years and clustered subsites was less than variation across sites. Life history characteristics such as size, sex, and whether the amphibian was a frog, toad, newt, or other salamander were the factors most strongly associated with bioaccumulation. Total Hg in dragonflies was a reliable indicator of bioaccumulation of MeHg in amphibians (R2 ≥ 0.67), whereas total Hg in sediment was not (R2 ≤ 0.04). Our study, the largest broad-scale assessment of MeHg bioaccumulation in amphibians, highlights methodological advances that allow for nonlethal sampling of rare species and reveals immense variation among species, life histories, and sites. Our findings can help identify sensitive populations and provide environmentally relevant concentrations for future studies to better quantify the potential threats of MeHg to amphibians.

Assessing the illegal hunting of native wildlife in China.

Illegal harvesting and trading of wildlife have become major threats to global biodiversity and public health1-3. Although China is widely recognized as an important destination for wildlife illegally obtained abroad4, little attention has been given to illegal hunting within its borders. Here we extracted 9,256 convictions for illegal hunting from a nationwide database of trial verdicts in China spanning January 2014 to March 2020. These convictions involved illegal hunting of 21% (n = 673) of China's amphibian, reptile, bird and mammal species, including 25% of imperilled species in these groups. Sample-based extrapolation indicates that many more species were taken illegally during this period. Larger body mass and range size (for all groups), and proximity to urban markets (for amphibians and birds) increase the probability of a species appearing in the convictions database. Convictions pertained overwhelmingly to illegal hunting for commercial purposes and involved all major habitats across China. A small number of convictions represented most of the animals taken, indicating the existence of large commercial poaching operations. Prefectures closer to urban markets show higher densities of convictions and more individual animals taken. Our results suggest that illegal hunting is a major, overlooked threat to biodiversity throughout China.

BatTool: projecting bat populations facing multiple stressors using a demographic model

Bats provide ecologically and agriculturally important ecosystem services but are currently experiencing population declines caused by multiple environmental stressors, including mortality from white-nose syndrome and wind energy development. Analyses of the current and future health and viability of these species may support conservation management decision making. Demographic modeling provides a quantitative tool for decision makers and conservation managers to make more informed decisions, but widespread adoption of these tools can be limited because of the complexity of the mathematical, statistical, and computational components involved in implementing these models. In this work, we provide an exposition of the BatTool R package, detailing the primary components of the matrix projection model, a publicly accessible graphical user interface (https://rconnect.usgs.gov/battool) facilitating user-defined scenario analyses, and its intended uses and limitations (Wiens et al., US Geol Surv Data Release 2022; Wiens et al., US Geol Surv Softw Release 2022). We present a case study involving wind energy permitting, weighing the effects of potential mortality caused by a hypothetical wind energy facility on the projected abundance of four imperiled bat species in the Midwestern United States.