Because of ectothermy and the high permeability of their skin, the thermal biology and water balance of anuran amphibians are highly influenced by variations in environmental temperature and water availability. Seasonal variation in these climatic variables are often followed by concurrent adjustments in frogs' thermal biology and water balance. We investigated seasonal variation in the thermal biology and water balance of snouted treefrogs, Scinax fuscovarius (Anura, Hylidae), a midsize nocturnal treefrog with continuous activity throughout the year. We measured body temperature when active in the field (T_field), thermal preference (T_pref) in a thermal gradient in the laboratory, and the minimum and maximum critical temperatures (CT_min and CT_max, respectively). Regarding water balance, we measured rates of evaporative water loss (EWL) and the skin resistance (R_s) to evaporation at three temperatures (15, 25, and 358C), dehydration tolerance, and rates of water uptake (WU), both at 258C. Measurements were carried out in the middle of the hot and wet spring–summer and the cold and dry autumn–winter. We found that T_field, T_pref, dehydration tolerance, and WU were higher in the hot–wet compared to the cold–dry season. Evaporative water loss rates increased with experimental temperature but did not vary seasonally. There was no seasonal variation in thermal tolerance for either CT_max or CT_min. Our data show that S. fuscovarius experience seasonal adjustments in some parameters of their thermal biology and water balance, but not in others. This variation may reflect different levels of plasticity among the sampled variables and quite likely functional compromises between body temperature regulation and water balance.

Freshwater turtles are one of the most endangered vertebrate groups, with an estimated 60% of species threatened. The influence of environmental factors on the life cycles of most turtle species is poorly understood, including triggers for nesting movements. Although temperature and rainfall have been identified as triggers for nesting in some species, it is unknown if and how reductions in rainfall arising from climate change may disrupt reproductive movement. We aimed to determine the environmental factors that trigger nesting movements of Southwestern Snake-necked Turtles (Chelodina oblonga) in south-western Australia, a global biodiversity hotspot undergoing severe climatic drying. A citizen science program was implemented to monitor nesting behavior over a 4-yr period. Generalized linear mixed models (GLMM) were used to identify the environmental variables that best explained the number of female turtles exhibiting nesting movements. Daily nesting movements were significantly associated with decreasing average air pressure, consistent with seasonal cold frontal weather systems that bring the majority of annual rainfall to the region. The effect of rainfall on turtle nesting movements varied depending on the spatial scale of modelling. Our results indicate that the projected reductions in frequency of cold fronts and rainfall in southwestern Australia may disrupt nesting movements. This could reduce recruitment success of this turtle and further increase the need for adaptive management to improve conservation of the species. The study highlights the need for further research on the impacts of climate change on environmental triggers of nesting of freshwater turtles in drying regions.

Sexual dimorphism in lizards is broadly attributed to intrasexual differences in morphology that affect fitness. In the lizard family Cordylidae, commonly known as girdled lizards, sexual dimorphism is common. Differences in morphological traits (e.g., body and head size) between females and males are useful for describing sexual dimorphism, and examining other traits (e.g., scar frequencies and color) is useful for understanding the selective pressures driving sexual dimorphism in cordylids. Recent morphological studies in Cordylidae reveal sexual dimorphic biases where males have larger heads, but either sex may have larger bodies. In this study, we examined body size, head dimensions, and other traits that commonly differ between sexes to identify sexually dimorphic traits and understand selective pressures in the Namibian endemic cordylid Namazonurus pustulatus (Herero Nama Lizard). We measured 224 field and 10 museum specimens within the known distribution of N. pustulatus. Our results indicate that females were larger in snout–vent length (SVL), axilla-to-groin length, and mass, but males were larger in head width and head length. Allometric growth in juvenile head dimensions was greater than that in adults. Segmented regression analyses indicated a change in growth rate of approximately 68.3–70.0 mm SVL, which we associated with sexual maturity. Adults of both sexes were larger at low elevations (1200–1700 m above sea level) than adults at high elevations (2000–2500 m above sea level), but there was no difference in head height. Epidermal glands (generation glands and femoral pores) scaled with SVL. No differences in scar frequencies were identified, but frequencies were higher than any other cordylid species recorded to date. We attributed larger female size to fecundity selection and larger male head size to sexual selection. This work establishes the first detailed biometric characteristics of the species, fills the missing literature gap of sexual dimorphism information from a species in the Namazonurus clade, and is the first to examine sexual dimorphism in a Namibian endemic cordylid.

Predicting the probability of species occurrence based on environmental variables across landscapes makes it possible to determine suitable habitats and constitutes an important tool for identifying priority areas for conservation. Sand Dune Lizards (Liolaemus multimaculatus) are endemic to the temperate coastal dunes from Argentina and were recently classified as Endangered by the International Union for Conservation of Nature. We studied the influence of landscape metrics on this lizard's distribution and built predictive distribution maps from habitat suitability models. Additionally, we analyzed the representation of suitable habitats within natural protected areas (NPAs). We conducted lizard surveys in two successive seasons and obtained landscape metrics from thematic maps in two circular landscape units. All information collected was compiled into a Geographical Information System (GIS). The relationships between lizard presence or absence and the landscape metrics were analyzed using Generalized Linear Models, and the results were transferred using GIS to habitat suitability maps. Digitalized NPAs were overlapped on these maps to estimate the representation of suitable habitats. Within the main habitat categories of the sand dunes, L. multimaculatus was found exclusively in active dunes, which means that these habitats are of vital importance for this species. The habitat suitability models indicated that (1) patch size of active dunes and distance to the coastline were the main drivers of the distribution of this species, and (2) homogeneous landscapes composed of active dunes and low or null percentages of semi-fixed and forested dunes were the preferred habitat. The predictive maps showed that highly suitable habitats encompass <5% (2059.7 ha) of total active dunes and had a linear distribution near the coastline and far away from areas modified by human activities. Currently, only 19.8% (408.8 ha) of highly suitable habitats fall within NPAs boundaries. The high habitat association of the species and the very small remaining suitable habitat warrants urgent conservation measures, which can be supported by habitat suitability models based on landscape metrics.

The geographic isolation of conspecific populations can produce a diversification of signals through genetic drift, which may be reinforced by selection if populations (or sibling species) come into secondary contact. As conspicuous visual signals, bobbing displays of lizards have been described for numerous genera, and differences in display structure have been documented between some isolated conspecific populations. Although bobbing display structure has been detailed for several Galápagos Lava Lizard species (Microlophus sp.), intraspecific populations on different islands also exhibit various degrees of display structure divergence. In the present study, our goal was to determine if Microlophus bivittatus on San Cristóbal Island and a population on its adjacent islet of Isla Lobos possess differences in bobbing display structure. Interestingly, adult males on Isla Lobos exhibit gigantism compared to those on San Cristóbal, and the two populations have been isolated by the sea for several thousand years. We predicted that bobbing display speed would scale inversely with body size, such that displays would be detectably slower and longer in the supersized Isla Lobos males than those in the smaller San Cristóbal males. To test this prediction, we elicited displays from subjects by using a conspecific-mimicking robot. We measured two displays from 16 subjects in each population by using conventional unit-based variables as well as Fourier transform-based variables. After determining correlations among display variables, we tested for differences in uncorrelated display unit durations between Isla Lobos and San Cristóbal males. We then quantified within-subject, among-subject, and between-population variance for all variables by using nested ANOVAs and tested if variance differed between study populations at any level. Next, we used principal component analysis to create a small number of normally distributed variables (i.e., the principal components) from our original variables. These principal components then were used as inputs for discriminant function analysis to classify displays to populations. Comparisons of display unit durations supported our prediction only for the initial bob in displays, which was longer in Isla Lobos males than in San Cristóbal males. Nevertheless, when we considered multiple variables collectively, discriminant function analyses classified displays to the correct population at a level significantly greater than chance in all four unit-based analyses and three of four discrete Fourier transform-based analyses. Finally, supported by data on sexual size dimorphism and genetic differences between pairs of M. bivittatus populations (F_ST), our results indicate that divergence in bobbing display structure can occur relatively quickly if populations are sufficiently isolated.

Renewal of the epidermal tissues is often assumed to be the primary function of ecdysis in snakes. The semiannual replacement of the skin maintains a barrier against the external environment, with the timing and frequency of this renewal process considered to be a function of growth. As snakes eat and grow, they are forced to shed to accommodate the increase in body size, relating the resource environment to rates of growth and patterns of shed. It has also been suggested that shedding occurs in response to changing abiotic conditions or as a mechanism of semiochemical signaling. Resolution of the causal mechanism(s) that dictates patterns of ecdysis, and its relative importance at the population level, requires a working knowledge of when and how often snakes shed. To date, descriptions of patterns of the timing and frequency of shed events have been limited to laboratory studies and field observations of limited scope. We used 25 yr of radiotelemetry observations of Timber Rattlesnakes (Crotalus horridus) to describe the frequency and timing of shedding at the population level. We found that the frequency of shed events was approximately even between males and females, but that male frequency was related to body condition, whereas female frequency was correlated to reproductive condition. Further evaluation revealed that the timing of shed events in lower body condition males was randomly distributed throughout the year; timing in higher body condition males clustered around the mating season. Timing in females related to reproductive condition, with gravid females shedding early in the year and nongravid females shedding close to the peak in male–female courtship. Our study indicates that shedding patterns in males are coupled to the resource environment and offer support for shedding as a growth function, but in females shedding may be more tightly coupled to reproduction, serving alternate or additional roles in adult female snakes.

Reintroduction of species at sites where populations have been extirpated has become a common technique in wildlife conservation. To track progress towards reintroduction success, effective postrelease monitoring is needed to document vital rates of individuals and the corresponding impact on population trajectories. We assessed growth and body size in Eastern Indigo Snakes (Drymarchon couperi) using a data set from multiple projects across the species' distribution, including free-ranging wild snakes, snakes reared in captive-breeding programs, and snakes released at two reintroduction sites. We used these data to fit a von Bertalanffy growth model in a Bayesian framework to quantify differences in growth among three broad categories of snakes (wild, captive, and reintroduced), while accounting for measurement error across various projects. We also compared changes in body mass of captive-born individuals from four captive rearing facilities. Asymptotic snout–vent length across all groups was 185 cm (95% credible interval = 177–194 cm) for males and 157 cm (95% credible interval = 153–161 cm) for females. Reintroduced snakes had a higher growth coefficient than either captive or wild snakes (e.g., captive females = 1.20 [1.06–1.35] d^–1; wild females = 1.22 [0.95–1.49] d^–1; reintroduced females = 1.62 [1.21–2.05] d^–1), indicating that current captive-breeding and rearing efforts for indigo snakes produce similar or faster growth trends compared to wild populations. Furthermore, daily changes in juvenile body weight relative to body size were similar in three of the four captive rearing facilities (mean for females at Orianne Center for Indigo Conservation = 0.57 [0.48–0.65]; Zoo Atlanta = 0.55 [0.37–0.72]; Welaka National Fish Hatchery = 0.55, [0.36–0.73]; Auburn University = 0.39 [0.21–0.58]). Long-term project success for indigo snake reintroductions will depend on continuing to implement best practices in an adaptive management framework.