AbstractAmphibians can obtain their colour from a combination of several different pigment and light reflecting cell types called chromatophores, with defects in one or several of the cells leading to colour abnormalities. There is a need for better recording of colour abnormalities within wild amphibian populations, as this may provide baseline data that can be used to determine changes in environmental conditions and population dynamics, such as inbreeding. In this study, we provide records of several types of chromatophore deficiencies, including those involving iridophores, xanthophores and melanophores, among two Australian tree frog species; the green and golden bell frog, Litoria aurea, and the eastern dwarf tree frog, L. fallax. We explore these colour abnormalities in terms of the chromatophores that have likely been affected and associated with their expression, in combination with typical colour phenotypes, colour variations and colour changes for these species. We intend for our photographs to be used as a visual guide that addresses the need for more accessible information regarding the physical manifestation of different chromatophore defects among amphibians.

It is vital to identify habitats used by each life stage of a species to formulate effective conservation management and restoration guidelines. For the threatened green and golden bell frog, Litoria aurea, it is currently recommended that, to prevent waterbody shading, managed or constructed habitat for the species should not include trees. Shading has been reported to prevent adults from sun basking, reduce breeding activity, and lower water temperatures, which may impede tadpole growth and development and provide optimum conditions for the amphibian chytrid pathogen, Batrachochytrium dendrobatidis. However, the complete exclusion of trees, which are naturally present in L. aurea habitat, warrants evidence that supports this recommendation. In the present study, we used a multi-year dataset on an L. aurea population on Kooragang Island, NSW, Australia to determine the occurrence of tree use by post-metamorphic individuals. These data included information on nearly 12 500 individuals captured from 86 waterbodies across 8 consecutive breeding seasons. We found that tree use by juveniles, adult males, and adult females was widespread and common, occurring both during the day and night, with more than one out of every 20 individuals captured in trees. Our findings suggest that trees are a potentially important attribute of the terrestrial component of wetland habitats occupied by L. aurea. We hypothesize that trees may (i) create microhabitat for foraging and/or increased diversity of prey species, (ii) provide refuge from predators, and (iii) allow sun basking off the ground, thereby offering protection against the chytrid fungus while removing them from chytrid-prevalent environments such as water and moist soils. We call for the careful reconsideration of tree exclusion within L. aurea habitat and further research into the benefits of allowing trees to grow near waterbodies to accommodate the ecological needs of this threatened species.

Fences have been widely used to exclude, manage, or monitor both native and invasive amphibian populations. Given that fences are artificial barriers that impact animal movements within the landscape, it is critical they do not allow for unwanted movement or lead to unintended animal welfare risks. We have carried out a literature review to identify features that have been used for amphibian fences, as well as aspects of fence design, installation, and maintenance that have limited their effectiveness. We also describe our own application of adaptive management to amphibian exclusion fences, in which we detected flaws and improved features, and monitored the effectiveness of these changes. Based on an exploration of the literature and our experiences, we found several key attributes to fences that must be considered when created for amphibians, including height, lip barriers, underground barriers, support frameworks, gates, seams, clearance zones, and moisture refuges. We found that studies commonly do not detail all of these aspects of their fences, and that few openly describe flaws in the design, installation, and subsequent maintenance of their fences. This is potentially concerning because it may limit chances to make improvements to fence designs that are specific for amphibians. We subsequently provide considerations and recommendations for each key fence attribute, along with maintenance and monitoring advice. These take into account intended fence purpose, desired fence permeability, and project constraints for a variety of amphibian types, life histories, and developmental stages. They are intended to be used by managers to assist in designing an effective fence for their target species. Some of our recommendations to reduce animal welfare risks are to minimise the use of: (1) fence materials that could cause abrasion injuries, (2) dry substrates that could lead to desiccation, (3) geofabrics that could lead to entanglement, and (4) fence aprons that animals could easily become trapped under. This is likely to be a valuable guide for practitioners who are required to install amphibian fences and for policy makers who prescribe fences for mitigation. This guide is applicable for projects managing threatened native species, as well as invasive species, such as the cane toad (Rhinella marina).

Invasive species pose a significant threat to global biodiversity, prompting the need for novel management strategies. We investigated the effect of pond placement in preventing colonization by Gambusia holbrooki, an invasive fish impacting amphibians, including the threatened green and golden bell frog (Litoria aurea). Because Gambusia moves between aquatic systems during surface flow events, we aimed to determine whether constructing ponds on elevated plots devoid of fish was less likely to be colonized due to the absence of two‐way water connectivity with sources from below. Over eight consecutive years, we monitored Gambusia presence at 50 ponds within an industrialized area of Kooragang Island, New South Wales, Australia, home to one of the largest extant subpopulations of L. aurea. This included 24 constructed ponds, 19 of which were on elevated plots, along with 26 historic ponds already present prior to the study. None of the ponds constructed on elevated plots were ever colonized by Gambusia during the study period, while most (three out of five) constructed at lower elevation and historical ponds (25 out of 26) were. Our findings indicate that the elevated plots acted as plateau safe havens, with elevation difference rather than proximity to Gambusia sources the key driver preventing colonization. These plateaus are now functioning as some of the only Gambusia‐free breeding habitat for L. aurea in this area. This research highlights the role of landscape topography and intentional pond placement in safeguarding newly constructed wetlands from invasive fish, providing insights for wetland conservation and biodiversity protection.

There is a large body of research literature on assessment in health professions education. However, there is an even larger body of literature on assessment in the broader field of higher and professional education. This chapter investigates some foundational and emerging ideas in the education research literature on assessment that may be useful to health professions educators. It first covers basic ideas from educational assessment: standards-based approaches; the multiple roles of assessment; and the aligning of assessment with learning outcomes. It then addresses some new "big ideas" in assessment research: new perspectives on feedback; the development of students' capabilities in dealing with feedback; and the promotion of academic integrity. Throughout, links are made between those ideas and how they may work in health professions education. We hope it will provide both a useful foundation for investigating other chapters on assessment within this text, as well as a prompt to pursue some new concepts from the broader field of education.

Temporary freshwater lenses can form in saline environments after rainfall, providing essential resources for species including drinking water and dispersal routes. However, there is limited indication that these lenses can also be used for breeding. Herein, we provide evidence of the green and golden bell frog, Litoria aurea, performing breeding activities, including calling and amplexus, in tidal mangrove creeks on Kooragang Island, NSW, Australia. Our findings suggest that these creeks intermittently phase into a low salinity state after the influx of fresh water from rainfall, forming temporary freshwater lenses that can be exploited before the creeks revert to a saline state. These lenses had salinities (1.4 ppt and 4.5 ppt) within the tolerance limit of L. aurea tadpoles, although we are unsure whether oviposition took place and offspring survival to metamorphosis was achieved. It is possible that anthropogenic disturbances to hydrology on Kooragang Island have benefited L. aurea by restricting tidal influences in mangrove creeks, prolonging the duration of freshwater lenses.

The deliberate movement of wildlife is an accepted mitigation measure to manage the impact of anthropogenic activities. A presumption is that moved individuals settle at recipient sites that possess appropriate habitat. However, translocations have a low rate of success, with many projects unable to identify the cause of failure. We studied the translocation of a threatened amphibian, the green and golden bell frog, Litoria (=Ranoidea) aurea, over short distances within a metapopulation in Australia. Individuals were removed from a fenced area of contaminated habitat earmarked for remediation (donor site) and translocated to nearby ponds (recipient sites) to maintain the breeding population in-situ and allow future natural recolonisation once remediation was completed. The distance between recipient and donor site significantly influenced the chance of translocated frogs being detected back at the fenceline, with the return rate dropping from 35% to 5% when the recipient site was moved from 50 to 400 m away. Additionally, translocated frogs exhibited heightened movement from the recipient site when compared to non-translocated frogs. This is one of only a few artificial movement studies of amphibians, with implications for the management of populations undergoing translocation. Our work shows the potential dangers of using translocation to remove individuals from land development and presuming this avoids impacts to threatened species. We recommend monitoring the return of translocated amphibians to donor sites and disturbances to movement behaviour induced by translocation, in order to predict the likely effectiveness of amphibian translocations for mitigating the ecological impacts associated with land development.

Traditional methods for identifying individual amphibians in capture-mark-recapture (CMR) studies have been primarily confined to post-metamorphic stages, using artificial markers that come with a variety of limitations. An alternative that may open CMR studies to earlier life stages involves the use of a species' natural external markers in photo-based identification. In this study, we investigated whether it was possible to distinguish tadpoles of the threatened green and golden bell frog (Litoria aurea) at the individual level based on tail venation patterns. We collected photographs of the tails of captive-raised tadpoles using a smartphone over a 4-week period. This photo-library was used to create an electronic survey where participants were asked to detect matches for query tadpoles from small image pools. We found that most participants agreed on a match for each query, with perfect consensus achieved for most queries (83%). We detected a 14% decline in perfect consensus when participants were asked to match images of tadpoles separated by longer time intervals, suggesting that it is more difficult to visually identify recapture events of L. aurea tadpoles over extended periods due to changes to tail appearance. However, consensus was obtained by participants for all queries, with all matches verified as being correct by the primary researcher. The strength of agreement among participants with no prior experience in matching tadpole tails suggests that there is sufficient inter-individual variation in this feature for individuals to be manually identified. We thus propose that photo-identification is likely to be a valid, non-invasive technique that can be used for short-term studies on tadpole populations that display tail venation. This offers an alternative to artificial markers that may not allow for individual identification, while also opening up tadpole monitoring programmes to citizen scientists who can be recruited online to process image data from home.

Understanding amphibian population dynamics is integral to mitigating severe declines that are occurring due to threats such as habitat removal and chytrid-induced disease. Few studies have focused on sex-specific population dynamics, despite the potential for these processes to alter colonisation and population turn-over in newly created habitats. Here, we investigate sex-specific population dynamics in the threatened green and golden bell frog (Litoria aurea) using intensive capture-recapture methods in a newly created wetland complex and control sites. As hypothesised, females took longer to reach maturity compared to males. The length of female maturation was 3.9 times greater than that of males (428.68 days +/- 107.6 SD and 110.16 days +/- 20.59 SD, respectively). This resulted in a one-year delay in female population size increase compared to the male population. The operational sex ratio (OSR) in the second year of monitoring in the created wetlands had the most disproportionate male bias out of any year and any site (12/1 male/female, male proportion = 0.92 +/- 0.89-0.94 95% CI). In the third year, the OSR had become less male biased (2.6/1, male proportion = 0.72 +/- 65-0.78 95% CI), likely attributed to the maturing of the females produced in the first year breeding events. We did not find any evidence that survival or detection probability influenced the observed OSRs in the created wetlands. Based on survival rates of each sex, we estimate that males are 77 times more likely to reach sexual maturity compared to females. We postulate that the combination of chytrid-induced disease and sex-biased maturation rates may be a driver of declines, especially in populations with limited recruitment. We encourage future research into investigating sex-specific population dynamics of amphibians, especially relating to reintroduction ecology and disease.

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Individuals within amphibian populations are commonly identified using artificial marking techniques, such as toe clipping and microchipping. However, many species in this group may be strong candidates for visual identification from photographs given intraspecific variability in skin features. We investigated the potential for dorsal skin patterns to be used as natural markers for the photo-identification of both juveniles and adults of the green and golden bell frog (Litoria aurea). This is a threatened species that has come under intense population monitoring using capture-mark-recapture procedures primarily involving the use of artificial markers, with no apparent investigation of the potential for natural markers to be used instead. We collected photographs of marked individuals to determine the level of intraspecific variability in dorsal patterning within a population. This photo-database was subsequently used to create an online survey in which participants were asked to match separate images of query frogs from small image pools by comparing dorsal patterns. Photographs were taken on a smartphone device under field conditions to test whether this technique could be applied to the study of wild populations with little cost or expertise required. We showed that dorsal patterns are clear and distinct among L. aurea individuals and easily visualised from field-acquired images to detect recapture events by eye with a low error rate. While an overwhelming majority of adults possessed dorsal patterning that can be easily distinguished by eye, juveniles often showed a complete absence of patterning, suggesting that photo-identification may be more effective for adult stages. Nevertheless, we highlight the feasibility of collecting visual information on the natural markings of a threatened anuran, providing evidence that it may be used as a supplementary form of identification alongside more traditional techniques, highlighting a potential direction for the future monitoring of this species.

Amphibians have declined due to multiple impacts including invasive fish and the disease chytridiomycosis caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd). Wetland restoration can be used to increase amphibian populations. However the design of created wetlands must account for threats such as Bd and introduced fish. There have been no attempts on a landscape level to manage these threats with habitat design. Here we monitored the green and golden bell frog (Litoria aurea) in 2.6 ha of constructed wetlands designed to enhance breeding and increase survival through passive mitigation of Bd and exotic fish. We compared the fecundity, adult population sizes, introduced fish occupancy, Bd prevalence and survival rates of frogs in created wetlands (CW) to three control sites to determine if and why the habitat design was successful. Monitoring involved weekly capture-recapture during the austral spring and summer for three L. aurea breeding seasons. We hypothesised that (1) if the CWs were successful in passively limiting fish colonisation, a larger number of breeding events would be detected compared to control sites which are known to be widely colonised by introduced fish. (2) If the wetlands were successful in passively mitigating Bd, then we would observe an equal or greater survival rate and equal to or lower Bd prevalence compared to control wetlands. We observed a 3.3-fold increase in adult population size in CW from season 1 to 2, and the population increased further in season 3.We found strong support for hypothesis (1) and weak support for (2). Based on these results, we conclude that this design was beneficial shortly after their formation primarily due to fish exclusion, but further study is required to determine if these benefits extend long-term. Future amphibian restoration studies are needed to improve the design of wetlands to enhance suppression of Bd.

Recent research has revealed that impacts of some invasive species are chronic. Invasive cane toads Rhinella marina have apparently caused rapid and severe population-level declines of the Endangered northern quoll Dasyurus hallucatus across tropical Australia; however, more targeted, quantitative impact data are needed to disentangle this from other threats such as fire regimes, disease, feral cats and dingos. Moreover, repeatable counts before, during, after and long after toad invasion are needed in order to determine if short-term impacts are chronic vs. transitory. We used game cameras to monitor 2 quoll populations and their prey over a 5 yr period spanning the invasion of the toxic cane toads in 2 gorges in northwestern Australia. We predicted severe declines in quolls with the toad invasion, and predatory release of 2 prey species of quolls, a rodent and a smaller marsupial. Quolls declined quickly upon arrival of toads, becoming undetectable in one gorge and barely detectable in the other. Identification of individuals via unique spot patterns confirmed that the declines in detection rates were due to changes in relative abundance rather than decreases in activity. Despite quoll declines we found no evidence of mesopredator release; small mammals generally declined as toads arrived. Our research confirmed rapid population-level declines of quolls, and possibly smaller mammals, associated with arrival of invasive cane toads. Importantly, our surveys provide a baseline for future surveys to determine whether these short-term impacts are chronic or transitory, and whether recovery requires assistance from managers.

We investigated predator–prey interactions between cane toads (Rhinella marina) and native water rats (Hydromys chrysogaster), where toads are novel prey. We show that wild water rats preferentially targeted larger toads, and consumed specific non-toxic organs only. Rats either rapidly learned these behaviours, or adapted them from hunting native frogs.

Since the Permian, Earth's aquatic ecosystems have been ecologically dominated by numerous lineages of predatory amniotes. Many of these groups evolved elevated ridges of enamel that run down the apical-basal axis of their teeth, referred to here as apicobasal ridges. This trait is commonly used as a taxonomic tool to identify fossil species and higher groupings, but the function of the ridges and their associated ecological significance are poorly understood. Here, we aim to clarify the phylogenetic distribution of apicobasal ridges among amniotes and to examine how the morphology of apicobasal ridges varies across species. We show that these ridges have evolved independently numerous times and are almost exclusively found in aquatic-feeding species. Ridge morphology varies, including tall, pronounced ridges, low, undulating ridges and interweaving ridges. Their internal structure also varies from tooth crowns with locally thickened enamel to undulating enamel-dentine interface. We assess the relative merits of different hypothetical functions of the ridges and propose that although apicobasal ridges might provide some strengthening of the tooth, their morphology and pattern of evolution do not indicate that this is their primary function. Instead, we suggest that apicobasal ridges serve to increase the efficiency of puncture, grip and/or removal.

Plastic responses may allow individuals to survive and reproduce in novel environments, and can facilitate the establishment of viable populations. But can novel environments reveal plasticity by causing a shift in a behavior as fundamental and conspicuous as daily activity? We studied daily activity times near the invasion front of the cane toad (Rhinella marina), an invasive species that has colonized much of northern Australia. Cane toads in Australia are nocturnal, probably because diurnal activity would subject them to intolerably hot and dry conditions in the tropical savannah during the dry season. Our study can demonstrate, however, that upon reaching novel environments some toad populations became diurnal. Sandstone gorges offered cane toads novel, deeply shaded habitat. Gorges with an east-west axis (day-long northern shadow), narrow gorges and narrow sections of gorges contained toads that were primarily diurnal, while gorges with a north-south axis, wide gorges and wide sections of gorges contained mainly nocturnal toads. For example, remote camera data (1314 observations of toad activity times over 789 trap days) revealed strictly nocturnal activity at four ‘exposed’ sites (99% of 144 observations over 179 days), compared to mostly diurnal activity at a ‘shaded’ site (78% of 254 observations). Visual encounter surveys confirmed that diurnal activity occurred exclusively at shaded sites, while most nocturnal activity occurred at exposed sites. The close proximity of diurnal and nocturnal toads (4–7 km) provided compelling evidence for the abovementioned physical factors as the proximate cause of the behavioral dichotomy, and for a novel (deeply shaded gorges) environment causing the shift to diurnal activity.

Ecomechanical measures of performance such as bite force may function as an indirect measure of niche. This study proposes that allometric changes in performance may contribute to niche separation, especially in a group where the specific mechanism(s) remains unclear. We surveyed the bite force and morphology of 5 wild caught, sympatric skink species in the Kimberley region of Western Australia. Skinks were collected from trapline fences, weighed, photographed, and maximum bite force was measured with a piezoresistive force sensor. Morphological metrics were derived from photographs of the dorsum. Normalized morphological traits indicate interspecific variability in form, particularly in forelimb length, which may be a result of habitat separation. Bite force showed strong, significantly positive, allometric scaling against most morphological traits. Tail length was the only morphological trait that scaled isometrically. Allometric changes in bite force may increase dietary breadth, allowing larger skinks to supplement their diet with larger, more durable prey. This study reveals that ecologically relevant traits may be explained by allometric differences coupled with size variation. Future work should focus on (1) an increase in sample size, (2) long-term measurement of diet selection, and (3) accessibility of prey items to our focal animals.

Abstract: In oviparous reptiles with no parental care, the choice of nest site is a mother's final investment in her offspring. Although linkages between nest site choice, egg temperatures, and embryonic success have been well studied, much less is known about analogous linkages with soil moisture encompassing developing embryos. Most ground-nesting reptiles nest at depths <25 cm, with the deepest nests <1.0 m deep. Recently, however, the nests of two species of monitor lizards (Varanus panoptes and V. gouldii) have been discovered at depths of 2.3-3.0 m, suggesting that nesting at extreme depths in these species is an adaptive response to the lack of sufficient soil moisture at shallower depths. Herein, we examine this idea with V. panoptes, specifically predicting that deeper nests in a desert ecosystem compared with those in a savannah ecosystem are attributable to differences in the magnitude of rainfall. We excavated a communal nesting warren to a depth of 4 m and identified 11 fresh nests and 99 hatched nests. Mean nest depth in the present study was greater than that in savannah. However, nests were shallower than those of V. gouldii in the same general location, possibly because of local heterogeneity in soil moisture. Hatchlings excavated their own emergence burrows rather than following the burrows of their mothers, despite relatively great distances through resistant soils. Collectively, deep nesting creates energetic challenges for mothers and hatchlings, suggesting an adaptive function for the behavior.

Numerous studies investigate morphology in the context of habitat, and lizards have received particular attention. Substrate usage is often reflected in the morphology of characters associated with locomotion, and, as a result, claws have become well-studied ecomorphological traits linking the two. The Kimberley predator guild of Western Australia consists of 10 sympatric varanid species. The purpose of this study was to quantify claw size and shape in the guild using geometric morphometrics, and determine whether these features correlated with substrate use and habitat. Each species was assigned a Habitat/substrate group based on the substrate their claws interact with in their respective habitat. Claw morphometrics were derived for both wild caught and preserved specimens from museum collections, using a 2D semilandmark analysis. Claw shape significantly separated based on Habitat/substrate group. Varanus gouldii and Varanus panoptes claws were associated with sprinting and extensive digging. Varanus mertensi claws were for shallow excavation. The remaining species' claws reflected specialization for some form of climbing, and differed based on substrate compliance. Varanus glauerti was best adapted for climbing rough sandstone, whereas Varanus scalaris and Varanus tristis had claws ideal for puncturing wood. Phylogenetic signal also significantly influenced claw shape, with Habitat/substrate group limited to certain clades. Positive size allometry allowed for claws to cope with mass increases, and shape allometry reflected a potential size limit on climbing. Claw morphology may facilitate niche separation within this trophic guild, especially when considered with body size. As these varanids are generalist predators, morphological traits associated with locomotion may be more reliable candidates for detecting niche partitioning than those associated directly with diet.

Dating back to 255Mya, a diversity of vertebrates created mysterious deep helical burrows, often called Daimonelix (devil's corkscrews). A consensus function for these unique structures has not been reached, but the recent discovery of deep helical nesting burrows created by (extant) monitor lizards provides a unique opportunity to interpret Daimonelix and morphologically similar fossil burrows. We excavated a communal nesting warren of the Sand Monitor (Varanus gouldii) to test hypotheses for nesting and emergence behavior. First, we hypothesized that the nests of V.gouldii (in desert) would be deeper than those of the closely related V.panoptes (in savannah), because lower annual rainfall in the former (similar to 350mm vs. similar to 1000mm) increases the threat of egg desiccation during the extremely long, dry season incubation period (similar to 8months). Second, we predicted that hatchlings would follow the nesting burrows of their mothers during emergence, because excavating their own emergence burrows would be energetically prohibitive due to the extreme depth and soil hardness. We excavated the warren to a depth of 4m, finding 97 nests. As predicted, nest depth in V.gouldii (mean=3.0m, N=73) was significantly greater than in V.panoptes (mean=2.3m, N=52) from a previous study, and represents the deepest excavated ground nests of any vertebrate in the world. Contrary to our hypothesis, hatchlings ignored their mothers' nesting burrows, instead remarkably excavating their own emergence burrows. The communal nesting warrens and deep burrows of V.gouldii must have profound implications for the energetics of mothers and hatchlings, and perhaps for the social biology of the species. Although the function of the helix itself remains elusive, our results support the hypothesis that the extreme deep burrowing of Palaeocastor, Diictodon and other extinct animals was a response to arid conditions rather than temperature.