Frog Habitat Research Articles

Sex, health status and habitat alter the community composition and assembly processes of symbiotic bacteria in captive frogs

BackgroundFrogs are critical economic animals essential to agricultural ecosystem equilibrium. However, Meningitis-like Infectious Disease (MID) often affects them in agricultural settings. While frog-associated microbiota contribute to elemental cycling and immunity, the effects of frog sex and health on gut bacteria remain understudied, and the relationship between frog habitat and soil microbes is unclear. We aimed to determine how frog sex, health status and habitat influence symbiotic bacteria and community assembly mechanism to provide guidance for sustainable frog farming and conservation.ResultsWe employed 16S rRNA sequencing to investigate gut microbiota differences in relation to frog sex and health status. We also compared symbiotic communities in frog-aggregation, native and soybean soil on the farm. Results showed that gut bacterial β-diversity and taxonomy were markedly influenced by frog sex and health. Healthy frogs had more robust gut bacterial metabolism than frogs infected with MID. Cooccurrence network analysis revealed that healthy female frogs had more complex microbial network structure than males; however, diseased males showed the greatest network complexity. The assembly mechanism of gut bacteria in male frogs was dominated by deterministic processes, whereas in female frogs it was dominated by stochastic processes. Among symbiotic bacteria in frog habitat soils, deterministic processes predominantly shaped the community assembly of soybean soil. In particular, soybean soil was enriched in pathogens and nitrogen functions, whereas frog-aggregation soil was markedly increased in sulphur respiration and hydrocarbon degradation.ConclusionOur study reveals that sex mainly alters the interaction network and assembly mechanism of frog intestinal bacteria; MID infection significantly inhibits the metabolic functions of intestinal bacteria. Furthermore, diverse frog habitat soils could shape more symbiotic bacteria to benefit frog farming. Our findings provide new horizons for symbiotic bacteria among frogs, which could contribute to sustainable agriculture and ecological balance.

A NEW SPECIES OF FROG FROM NORTHEASTERN COLOMBIA (GENUS ELEUTHERODACTYLUS: LEPTODACTYLIDAE)

A new species of frog from the Eleutherodactylus nigrovittatus group is described from cloud forests in northern Santander. The new species is most similar to E. nigrovittatus of the Amazon basin but is equally closely related to the Andean E. latens and E. mantipus found on the Central and Western cordilleras. Based on a phylogenetic analysis, the primitive habitat for frogs of this species group is páramo with subsequent downward movement.

Conservation of frog habitats for land consolidation projects in paddy field areas

Conservation of frog habitats for land consolidation projects in paddy field areas

Can road stormwater ponds be successfully exploited by the European green frog (Pelophylax sp.)?

Stormwater ponds (“SWPs”) are artificial roadside structures, conceived to retain and clean polluted runoff water, before its release to the environment. SWPs were not designed as suitable habitats for wildlife. However, SWPs in Europe are frequently used as breeding sites by amphibians, especially by the European green frog (Pelophylax sp.). Yet, the potential long-term effects of pollutants within SWPs on the populations of this species are unknown. In this study, we investigated the suitability of SWPs as a habitat for European green frogs living in Alsace, NE France, a region with a highly modified landscape that mainly consists of croplands with few natural wetlands remaining. We compared various biological indicators of individual health in 709 green frogs belonging to different life history stages, living in 9 semi-natural ponds (SNPs) and in 25 SWPs. There were no differences between these two pond types for most of the indicators investigated. However, juveniles had a lower body condition (−124%) in SWPs, while adults were 8.3% larger and 41.4% heavier in SWPs. Based on these results, we suggest that SWPs are not a suitable habitat for the development of European green frogs (i.e. juveniles), but may serve as a substitute habitat for adults in a highly modified landscape with few natural wetlands remaining. SWPs may especially act as relay sites, allowing frogs to colonize relict wetlands.

Distribusi Cacing Trematoda Saluran Pencernaan Katak Dari Berbabgai Lokasi Persawahan Di Kabupaten Lombok Timur

Trematode worms have been found in various types of frogs which cause disease in frogs or toads can be a reservoir for these worms. Lombok Island has many rice fields which are habitat for frogs. Frogs that live in this environment allow direct contact with various types of Trematodes. The purpose of this study was to determine the type and distribution of Trematoda worms found in the digestive tract of frogs in the rice fields of East Lombok Regency. A cross-sectional survey study using purposive sampling methods on frogs in three rice fields in East Lombok Regency was carried out in February 2020. Worms were collected from the digestive tract of frogs and fixed with 70% warm alcohol, cleaned with alcohol, and examined under a microscope. A total of 64 frog samples were taken in three rice fields, East Lombok Regency. A sample examination was carried out at the Equin Clinical Center Skill laboratory Faculty of Veterinary Medicine of Mandalika University of Education. The results showed that Mesocoelium spp was distributed among frogs in three rice fields in East Lombok Regency, with a prevalence of 45% in Pringgabaya Village, 50% in Suele Village, and 53.57% in Tanjung Teros Village.

ACTIVE SEASON AND PRE-OVERWINTERING MICROHABITAT USE BY OREGON SPOTTED FROGS (RANA PRETIOSA) AND AMERICAN BULLFROGS (LITHOBATES CATESBEIANUS [RANA CATESBEIANA]) AT CONBOY LAKE NATIONAL WILDLIFE REFUGE, WASHINGTON

Conboy Lake National Wildlife Refuge (CLNWR) in Washington State supports one of the largest remaining populations of federally listed Oregon Spotted Frogs (OSF; Rana pretiosa). Invasive American Bullfrogs (Lithobates catesbeianus [Rana catesbeiana]), implicated in amphibian declines, are also abundant at CLNWR. Owing to the likely negative effect of this aquatic invader on the highly aquatic OSF, bullfrog control strategies are needed. One method is to limit habitat used by bullfrogs while retaining or enhancing OSF habitat, but for such an approach to be implemented, the 2 species must partition habitat sufficiently. We used radiotelemetry to characterize OSF and bullfrog active-season and pre-overwintering habitat in the human-engineered ditch system at CLNWR. We tracked 12 OSF and 10 bullfrogs from mid-to-late summer, recorded data on frog location and habitat, and analyzed movement patterns, niche breadth, and spatial differences between species. Based on minimum convex polygons, bullfrogs overlapped extensively with OSF habitat space in the ditch system. During the active season, niche analyses also showed extensive overlap in the species' vegetation associations, with selected exceptions at the microhabitat scale. However, each species used distinct pre-overwintering habitats. The small differences in active-season microhabitats and pre-overwintering habitats, and our relatively narrow study conditions, create uncertainty about these species' habitat use in a broader context. Nonetheless, these results underscore the challenge of managing an invasive species that is both a habitat generalist and congener and expose the need for further research to guide management approaches to favor OSFs at CLNWR.

Water Temperature and Availability Shape the Spatial Ecology of a Hot Springs Endemic Toad (Anaxyrus williamsi)

Desert amphibians are limited to exploiting ephemeral resources and aestivating or to inhabiting scarce refuges of permanent water, such as springs. Understanding how amphibians use these resources is essential for their conservation. Dixie Valley Toads (Anaxyrus williamsi) are precinctive to a small system of cold and hot springs in the Dixie Valley, Nevada, USA. The toads have been petitioned for listing under the US Endangered Species Act, and information about how they use terrestrial and aquatic resources will help managers to conserve the toads and identify threats like geothermal energy development that might affect these toads. We used radiotelemetry to study the seasonal home ranges, movements, and habitat associations of Dixie Valley Toads in autumn 2018 and spring 2019. We found that toads were very closely associated with water in both seasons, with most observations occurring in water, especially for males in spring and all toads in the autumn. Even when found in terrestrial habitat, toads were a median distance of 4.2 m (95% credible interval = 3.3–5.3) from water; 95% of the time in spring and autumn, toads were within 14 m of water. Dixie Valley Toad habitat selection indicated a similar pattern, with selection in both spring and autumn for locations closer to water and for warmer water and substrates than at nearby available locations. In autumn, toads also avoided bare ground and terrestrial graminoids. Dixie Valley Toads selected brumation sites in, over (within dense vegetation), or near water, often near springs where water depths and temperatures are likely stable through the winter. The reliance of Dixie Valley Toads on water in spring, autumn, and during brumation suggests that alteration to historical flows and water temperatures are likely to affect the toads. Changes to the hydrothermal environment when toads are brumating could be particularly detrimental, potentially killing inactive toads.

Low desiccation and thermal tolerance constrains a terrestrial amphibian to a rare and disappearing microclimate niche

Drier and hotter conditions caused by climate change threaten species that exist close to their physiological limits, as well as those with limited ability to move. Habitat specialists may also be particularly vulnerable if they have specific abiotic requirements. Here we assess whether thermal and hydric constraints can explain the highly restricted and declining distributions of the critically endangered terrestrial-breeding frog, Geocrinia alba. We also evaluate the species’ vulnerability to climate change based on the similarity of current microclimatic conditions to their physiological limits. We found that G. alba had low thresholds of thermal and desiccation tolerance relative to other anuran species. The estimated thermal optimum (Topt) and critical thermal maxima (CTmax) were 23.3°C and 29.6°C, respectively, and adult frogs had an absorption threshold (AT, the lowest water potential at which water can be absorbed from a substrate) of −50 kPa, the lowest recorded for an amphibian. Comparing environmental conditions and water loss in the field using agar models showed that riparian habitats where frogs occur provide a unique microclimate in the landscape, offering significantly lower desiccation risk during extreme summer conditions compared to immediately adjacent riparian and terrestrial habitats. Monitoring of microclimate conditions within occupied frog habitats over 2 years showed that in extreme dry and hot years the AT was exceeded at six of eight sites, and Topt was exceeded at two of eight sites. Given their specific physiological limits, the apparent rarity of suitable microclimates and a regional drying–warming trend, we suggest that G. alba occupies a potentially disappearing niche and may be indicative of other habitat specialists that rely on ephemeral drainages. More broadly, this study highlights that desiccation thresholds may tightly constrain amphibian distributions and need to be considered along with thermal tolerance thresholds when predicting the impacts of climate change.

Relationship Between Spatial Pattern of Farmland Management and Frog Habitats during Non-Irrigation Season

Relationship Between Spatial Pattern of Farmland Management and Frog Habitats during Non-Irrigation Season

Can models of percutaneous absorption based on in vitro data in frogs predict in vivo absorption?

The primary aim of in vitro testing of chemicals delivered via the percutaneous route is to predict the absorption that would ensue if exposure occurred in live animals. While there is mounting evidence that in vitro diffusion studies in mammalian skin can provide valid information regarding likely in vivo absorption, little is known whether such a correlation exists between in vitro diffusion testing and in vivo blood levels in amphibians. The current study used previously-reported in vitro absorption data for caffeine, benzoic acid, and ibuprofen across isolated skin from the cane toad (Rhinella marina) to produce a series of linear mixed-effect models of the absorption parameters flux and permeability coefficient (Kp). Models investigated the relative impacts of animal weight, physicochemical characteristics of the applied chemical (logP or molecular weight), and site of application. The top models were then used to predict the flux, Kp and serum concentrations of the same three model chemicals. Finally, the absorption of these chemicals was determined in live cane toads, and results compared to the model predictions. LogP and site of application were included in all top models. In vivo absorption rates were lower than predicted for all chemicals, however, the models provided reasonable predictions of serum concentration, with factors of difference (FOD) ranging from 2.5–10.5. Ibuprofen, the chemical with the highest relative lipophilicity, had the poorest predictive performance, consistently having the highest FOD for all predictions. This report presents the first models of percutaneous absorption in an amphibian. These models provide a basic method to establish the approximate in vivo absorption of hydrophilic and moderately-lipophilic chemicals through frog skin, and could therefore be used to predict absorption when formulating such chemicals for treatment of disease in frogs, or for risk-assessments regarding chemical pollutants in frog habitats.

Evaluating the effects of red imported fire ants (Solenopsis invicta) on juvenile Houston Toads (Bufo [=Anaxyrus] houstonensis) in Colorado County, TX.

The spread of invasive species is considered a major threat to biodiversity, second only to habitat loss. Red Imported Fire Ants (Solenopsis invicta) are a globally invasive species with negative impacts reported on native invertebrate and vertebrate species. Federally endangered Houston Toads (Bufo [=Anaxyrus] houstonensis), endemic to Texas, are among the vertebrates reportedly negatively impacted by Red Imported Fire Ants (RIFA). Threats posed by RIFA to Houston Toads needed to be explicitly characterized. Large-scale chemical treatments to suppress RIFA and facilitate brood survival in Attwater’s prairie-chickens (Tympanuchus cupido attwateri) at the Attwater Prairie Chicken National Wildlife Refuge (APCNWR) afforded us an opportunity to experimentally examine the influence of RIFA abundance on juvenile Houston Toad growth and survival. We also sought to examine whether juvenile Houston Toads could grow and survive in a vegetation type similar to a historic species locality. We conducted a terrestrial mesocosm experiment to test whether the application of bait-driven suppressant decreased counts of RIFA relative to untreated sites. We examined whether counts of native ant and non-ant native invertebrates were higher in response to potential decreases in RIFA. We compared growth and survival rates in juvenile Houston Toads among treated and untreated sites, expecting juvenile growth and survival to be higher in response to potentially decreased RIFA counts and increased native invertebrate counts. We saw lower counts of RIFA in treated prairies, but we also observed a decrease in native ant counts possibly due to chemical treatment. Therefore, the application of bait-driven suppressant may not affect RIFA alone. We saw no difference in counts of non-ant invertebrates among treated and untreated sites. Juvenile Houston Toads did not differ in growth and survival among treated and untreated sites. We recognize that the lack of a relationship between juvenile growth and survival with a treatment effect, and therefore RIFA abundance, may be limited to APCNWR. We encourage additional experimental studies to elucidate RIFA impacts at other sites. We extrapolated apparent survival estimates from our study to one year. These appear comparable to juvenile survivorship required in simulations for Houston Toad population persistence and on this basis, we recommend that APCNWR be re-evaluated as a reintroduction site for Houston Toads. We also recommend further studies to potentially broaden the regulatory definition of Houston Toad habitat beyond the current restrictive view of canopied forest alone. Such studies would need to examine the utility of native grasslands as dispersal corridors/upland habitat for juvenile Houston Toads. Our findings emphasize the utility of experimental studies in directly examining the influence of perceived threats to imperiled species and the role of such clarifications in adapting recovery efforts.

Land use impacts poison frog chemical defenses through changes in leaf litter ant communities

ABSTRACT Much of the world’s biodiversity is held within tropical rainforests, which are increasingly fragmented by agricultural practices. In these threatened landscapes, there are many organisms that acquire chemical defenses from their diet and are therefore intimately connected with their local food webs. Poison frogs (Family Dendrobatidae) are one such example, as they acquire alkaloid-based chemical defenses from their diet of leaf litter ants and mites. It is currently unknown how habitat fragmentation impacts chemical defense across trophic levels, from arthropods to frogs. We examined the chemical defenses and diet of the Diablito poison frog (Oophaga sylvatica), and the diversity of their leaf litter ant communities in secondary forest and reclaimed cattle pasture. Notably, this research was performed in collaboration with two high school science classrooms. We found that the leaf litter of forest and pasture frog habitats differed significantly in ant community structure. We also found that forest and pasture frogs differed significantly in diet and alkaloid profiles, where forest frogs contained more of specific alkaloids and ate more ants in both number and volume. Finally, ant species composition of frog diets resembled the surrounding leaf litter, but diets were less variable. This suggests that frogs tend to consume particular ant species within each habitat. To better understand how ants contribute to the alkaloid chemical profiles of frogs, we chemically profiled several ant species and found some alkaloids to be common across many ant species while others are restricted to a few species. At least one alkaloid (223H) found in ants from disturbed sites was also found in skins from pasture frogs. Our experiments are the first to link anthropogenic land use changes to dendrobatid poison frog chemical defenses through variation in leaf litter communities, which has implications for conservation management of these threatened amphibians.

Distribution mapping of specialized amphibian species in rare, ephemeral habitats: Implications for the conservation of threatened “acid” frogs in south‐east Queensland

AbstractThe acid frogs of eastern Australia are a highly specialized group of threatened species endemic to acidic coastal wetlands of southern Queensland and New South Wales. The distribution of these species overlaps with areas of increasing development where land‐use intensification poses a significant threat. Successful conservation of these species requires that areas of high conservation value for acid frogs are properly identified and protected, particularly in south‐east Queensland which supports important populations of all four acid frog species: Litoria olongburensis, Litoria freycineti, Crinia tinnula, and the Queensland‐endemic Litoria cooloolensis. Species distribution modeling using rigorously vetted species occurrence data was used to identify areas of potential acid frog habitat with >89% predictive power for all species. Key predictor variables for acid frog species occurrence included: soil sandiness, vegetation, presence and/or type of wetland, and soil clay content. All species' predicted distributions occurred primarily in coastal regions, overlapping with densely human‐populated areas. Our modeling and analysis of species' distributions highlight local government areas where protection of wallum habitat is most important for the conservation of acid frogs, as well as areas of higher conservation value providing habitat for multiple acid frog species.

Demography, Habitat, and Movements of the Sierra Nevada Yellow-Legged Frog (Rana sierrae) in Streams

The Sierra Nevada Yellow-Legged Frog (Rana sierrae) has generally been viewed as a lake species, but it has increasingly been found in streams, including in the northern part of its range where it is particularly at risk. Developing effective conservation strategies has been hindered by a lack of knowledge of its basic ecological requirements in stream habitats. To address this information gap, we investigated the demography, habitat use, and movements of stream populations of this federally endangered species. We conducted capture–mark–recapture of adults, quantitatively described stream channel and riparian vegetation characteristics, and collected habitat use data at four northern Sierra Nevada mountain streams, counted egg masses at three central Sierra Nevada streams, and radio-tracked individuals at three central and southern Sierra Nevada streams. Stream populations in the northern range were very small with maximum abundances of <15 individuals, and apparent survival probability ranged from 0.57–0.81. In contrast, one southern Sierra Nevada stream had a large count of 547 adults. Egg mass counts ranged from 22–104 per stream. We found frogs in diverse headwater streams ranging from perennial to intermittent flow regimes, pool versus riffle dominated, and low to high channel gradient, and they used diverse microhabitats within these streams. In these stream habitats, frogs moved little over four-day survey periods but were capable of moving longer distances of up to 1248 m over the summer. Conservation and management of the at-risk R. sierrae are most likely to be effective when built on comprehensive quantitative information on basic ecological requirements in all habitats used by the species.

Berudu (Amphibia: Anura) di Taman Wisata Air Terjun (TWAT) Kembang Soka, Kulon Progo, Daerah Istimewa Yogyakarta Pada Musim Kemarau

Kembang Soka Waterfall Tourism Park in Java, Indonesia, is a potential habitat for frogs and toads (Anurans), as it contains a wide variety of water sources. To date, research on the diversity of Anura in the park has been limited to adult individuals. As such, the diversity of larvae is unknown. This study aimed to determine the diversity of Anuran tadpoles and their habitat in Kembang Soka Waterfall Tourism Park. Several surveys were carried out during the dry season of July–October 2018, with a total of five breeding sites surveyed. Three species of tadpoles were recorded: Leptobrachium hasseltii, Limnonectes kuhlii, and Phrynoidis aspera. The tadpoles of L. hasseltii had the greatest abundance, and were found in almost all breeding sites. Conversely, the tadpoles of L. kuhlii and P. aspera were only found in two of the breeding sites.  Key words: tadpoles, diversity, dry season, Kembang Soka Waterfall Tourism Park.

Short Communication: Habitat and population characteristics of the endemic Java Tree Frog (Rhacophorus margaritifer) in Ranca Upas, West Java, Indonesia

Abstract. Nilawati TS, Hernawati, Taufik RA. 2019. Short Communication: Habitat and population characteristics of the endemic Java Tree Frog (Rhacophorus margaritifer) in Ranca Upas, West Java, Indonesia. Biodiversitas 20: 1644-1649. The Java tree frog (Rhacophorus margaritifer) is one of the endemic frogs of Indonesia. Ranca Upas forest, West Java, Indonesia is one of the habitats of this species which is threatened by the extension of the ​​campground and tourism area. The aim of this study was to identify the habitat and population characteristics of Rhacophorus margaritifer in Ranca Upas forest. Data was collected through Capture-Mark-Release-Recapture method in every 100 m distance of a 300 m transect, along the river. The captured frogs were tagged using modified shoelaces. Habitat characteristics were analyzed descriptively and quantitatively, population number was estimated by the Schnabel method, and population distribution was calculated using the Morisita distribution index. The results showed that R. margaritifer habitat was at an altitude of 1630-1670 m asl with 16.6 oC average air temperature and 90.8% air humidity. The habitat was near river with clear water and mud substrate at 14.8 oC water temperature, 0.068 m/s water velocity, and neutral acidity. Furthermore, three species of plants, namely Strobilanthes crispus, Curculigo capitulata, and Cyathea sp. were identified to be very often used by R. margaritifer. Population abundance of R. margaritifer was estimated to be 286 individuals, with 5 individuals /100m2 density and it showed a clumped disp.ersion. Average size of frogs found in the study area was 40 mm Snout to Vent Length (SVL) and the range was 36 to 65 mm. This showed that the location is dominated by young frogs and the study area is a good habitat for R. margaritifer.

The influence of land cover and within-pool characteristics on larval, froglet, and adult wood frogs along a rural to suburban gradient

Urbanization is known to extirpate many species, but far less is known about how suburbanization may affect amphibian populations. We studied wood frogs (Lithobates sylvaticus) to test the effects of site characteristics (within-pool conditions and land cover indicative of suburbanization within 1000 m) and larval morphology on newly emerged froglets and post-breeding males across a suburbanization gradient in 15 pools in greater Bangor, Maine, USA. We raised field-captured larvae in microcosms and examined froglet morphology and locomotor performance at emergence and one month post-emergence. Larval mass was positively correlated with 50% of froglet responses (survival, size, and locomotor performance) but was negatively associated with adult size. Among site characteristics, egg density had the most salient influence with negative effects on larval survival and morphology as well as on 11 of 14 froglet responses. Vegetation, hydrology, and suburban-associated cover near pools also influenced froglet performance, and hydrology and suburban-associated cover was associated with larger and smaller adult morphology. However the influence of suburban-associated cover on froglet performance and adult morphology was small compared to that of within-pool characteristics. Specifically, our findings support the idea that within-pool conditions experienced by larvae can influence terrestrial stages with potentially life-long consequences. Nevertheless, in suburban landscapes where there is evidence of population declines, it is likely that suburbanization has the greatest impact on populations via direct effects on terrestrial stages. We encourage planners to maintain high-quality habitat for aquatic and terrestrial stage wood frogs in suburbanizing landscapes to avoid extirpation.

Feral-horse impacts on corroboree frog habitat in the Australian Alps

Context Introduced herbivores can have a substantial impact on native plants and animals, particularly in ecosystems that do not share a recent evolutionary history with similar herbivore species. The feral horse, Equus caballus, has a widespread but patchy distribution in Australia, with large populations present in national parks in the Australian Alps. There are few peer-reviewed studies of the impacts of feral horses on ecosystems in this region. However, impacts could be substantial, particularly in wetland and riparian environments that are focal points for horse activity and sensitive to trampling and physical disturbance. Aims In the present study, we used replicated horse exclosures to investigate the effects of feral horses on breeding habitat of the critically endangered northern corroboree frog, Pseudophryne pengilleyi, in the Australian Alps. Methods Pseudophryne pengilleyi constructs nests and lays eggs in dense litter surrounding small, seasonally flooded wetland pools. In 2010, we sampled the litter depth adjacent to pools at eight long-term P. pengilleyi monitoring sites. In 2011, horse exclosures were established at each of the eight sites, such that less than half of the wetland area was inside the exclosure. In 2015, we measured litter depth surrounding pools inside and outside the exclosures, as well as at three additional sites where feral horses were absent. Key results We found that the pool-edge litter was 1.9 times deeper in areas without horses (inside horse-exclosure plots and horse-free sites) than in areas accessible to horses (unfenced areas in horse-occupied sites). Conclusions Our study has presented experimental evidence that horse grazing and trampling reduce breeding-habitat quality for P. pengilleyi, which could result in reduced reproduction success. Implications Ensuring the persistence of high-quality habitat is crucial for the conservation of P. pengilleyi, particularly given the severity of the decline of this species associated with chytrid fungus. Our results have provided direct evidence of a negative feral-horse impact on the habitat of a threatened animal species in the Australian Alps.

Effects of skin region and relative lipophilicity on percutaneous absorption in the toad Rhinella marina.

Owing to the dynamic interaction between frog skin and the environment, xenobiotics in frog habitats are of particular concern, and knowledge of percutaneous absorption in frog skin is necessary for risk-mitigation purposes. Baseline transdermal kinetics in adult aquatic and arboreal frog species have recently been reported; however, there is little information regarding absorption kinetics in adult terrestrial species. The present study investigated the in vitro absorption kinetics of 3 model chemicals-caffeine, benzoic acid, and ibuprofen-through different skin regions in the terrestrial toad Rhinella marina. Caffeine flux was consistently higher than that of the other 2 chemicals (p < 0.001), whereas the fluxes of the moderately and highly lipophilic chemicals (benzoic acid and ibuprofen) were similar, regardless of skin region. When considering individual chemicals, caffeine demonstrated increased flux through the ventral pelvic skin compared with the ventral thoracic or dorsal skin regions. Flux did not differ between skin regions for either benzoic acid or ibuprofen. These findings have implications for management of environmental contamination in frog habitats, as many environmental xenobiotics are of moderate to high lipophilicity and would be expected to be equally absorbed from all skin surfaces in terrestrial toads. Environ Toxicol Chem 2019;38:361-367. © 2018 SETAC.

Multi-scale effects of land cover and urbanization on the habitat suitability of an endangered toad

Habitat degradation, entwined with land cover change, is a major driver of biodiversity loss. Effects of land cover change on species can be direct (when habitat is converted to alternative land cover types) or indirect (when land outside of the species habitat is altered). Hydrologic and ecological connections between terrestrial and aquatic systems are well understood, exemplifying how spatially disparate land cover conditions may influence aquatic habitats, but are rarely examined. We sought to quantify relative effects of land cover at two different but interacting scales on habitat suitability for the endangered arroyo toad (Anaxyrus californicus). Based on an existing distribution model for the arroyo toad and available land cover data, we estimated effects of land cover along streams and within entire watersheds on habitat suitability using structural equation modeling. Relationships between land cover and habitat suitability differed between scales, and broader, watershed-scale conditions influenced land cover along the embedded stream networks. We found anthropogenic development and forest cover at the watershed-scale negatively impacted habitat suitability, but development along stream networks was positively associated with suitability. The positive association between development along streams and habitat suitability may be attributable to increased spatial heterogeneity along urbanized streams, or related factors including policies designed to conserve riparian habitats amidst development. These findings show arroyo toad habitat is influenced by land cover across multiple scales, and can inform conservation of the species. Furthermore, our methodology can help elucidate similar dynamics with other taxa, particularly those reliant on both terrestrial and aquatic environments.