Sex ratio is a key demographic characteristic indicative of the condition of populations. Despite over 70 yr of study, researchers have not fully evaluated morphological characteristics that differentiate sex in Jemez Mountains Salamanders (Plethodon neomexicanus; federally endangered). Populations of this endemic salamander, which are distributed in north-central New Mexico, have undergone declines in the past two decades. We assessed morphological characters of 160 preserved P. neomexicanus specimens, evaluated our ability to infer sex in the field, and tested our ability to determine sex on a subset of preserved specimens. In preserved salamanders with body length (i.e., postcloaca snout–vent length, SVLp) ≥ 55 mm, females exhibited greater total length, trunk length, tail length, and cloaca length, and males exhibited greater precloacal tail width, head length, head width, and head height. We documented weakly female-biased size dimorphism. Females with SVLp ≥ 52 mm had cloacal rugae, whereas males with SVLp ≥ 51 mm had distinct papillose tissue in the cloaca and a cloacal cleft. In an evaluation of 30 preserved specimens, we correctly inferred sex in 97% of salamanders by cloacal characters alone. Of 29 adult salamanders captured in the field, we confidently inferred the sex of 27 individuals (16 females, 11 males) with SVL ≥ 44 mm. Thus, sex of most individuals can be correctly inferred in the field by cloacal characters. This information will aid researchers in better understanding population trajectories of this endangered species.

The lizard genus Teius is widely distributed in lowland areas to the east of the Andes in southern South America and includes three species: Teius teyou, T. oculatus, and T. suquiensis. All three Teius species are broadly similar in morphological characters, the dorsal coloration pattern being the best feature to distinguish them. Furthermore, T. suquiensis are parthenogenetic, whereas the other two are bisexual. We applied 2D geometric morphometric methods on head morphology to measure and compare variability between these clonally and sexually reproductive lizards and to assess form variability among populations within the parthenogenetic species. We studied 181 adult females of the three species from across a wide range of their distributions. Geometric morphometrics successfully separated them in the morphospace. The three Teius presented similar head size; hence, the differences found are related to shape. Teius teyou has a shorter snout and a narrower posterior area of the head whereas T. oculatus has a longer snout and a wider posterior area of the head, and T. suquiensis shows an intermediate phenotype. Levels of morphological variability among the species were similar and independent of reproductive mode. Differences in head size and shape among populations were observed within T. suquiensis, despite its clonal inheritance. The observed variability might be explained by populations that are composed of different clonal lineages, populations that showed different responses to varying local environmental factors, or both. Additional morphological studies considering genetic diversity and habitat characteristics may clarify the factors that promote morphological variability in the genus, especially in the parthenogenetic species.

Geographic variation in reproductive phenology can reveal how life history is shaped by the environment. For amphibians, the timing of reproduction has downstream consequences on other life history traits such as larval period and size at metamorphosis. Two-lined Salamanders (Eurycea bislineata species complex) are widespread across the eastern United States and Canada and exhibit dramatic geographic variation in reproductive morphology, reproductive behavior, and larval life history, and thus make compelling models for studying these processes. Here, we compile courtship and nesting records from citizen science data, published literature, museum records, field notes, and social media to describe the geographic variation of reproductive phenology in the E. bislineata species complex. We demonstrate that the date of oviposition is negatively correlated with mean annual temperature and examine how this may interact with the timing of other seasonal behaviors such as migration and overwintering. Finally, we discuss how these geographic patterns may influence the evolution of reproductive tactics through differences in the spatial and temporal clustering of courtship opportunities in terrestrial and aquatic environments.

As resource extraction moves north across the globe, wetland ecosystems in Canada are increasingly degraded because of disturbances associated with anthropic activities, including timber harvesting, hydroelectric development, and mining. These activities may particularly affect amphibian species that depend on certain wetland types for breeding, such as peatland and beaver ponds. We assessed the influence of pond and landscape-level characteristics on amphibian use of 50 ponds in northern Quebec, Canada in 2018 and 2019. Using acoustic recorders and visual counts, we estimated occupancy of calling males and abundance of metamorphosed individuals and egg masses of three amphibian species: Wood Frogs (Lithobates sylvaticus), Mink Frogs (Lithobates septentrionalis), and Spring Peepers (Pseudacris crucifer). We quantified the influence of variables such as pond type, area, fish presence, acidity, and landscape features on occupancy and abundance. We found no effect of explanatory variables on the probability of occupancy of calling males of the three species. Detection probability of Spring Peeper choruses increased with air temperature. The abundance of Mink Frog metamorphosed individuals decreased with increasing pond area and increased with water pH. Wood Frog reproductive effort, quantified as egg mass abundance, was more than four times greater in beaver ponds than in peatland ponds. Our survey results provide a reference to guide management decisions regarding conservation of amphibian assemblages in increasingly disturbed wetlands of northern Canada.

Comme l'extraction des ressources se déplace vers le nord de la planète, les écosystèmes des milieux humides du Nord canadien sont de plus en plus dégradés en raison des perturbations associées aux activités anthropiques, notamment la récolte du bois, le développement hydroélectrique et les activités minières. Ces activités peuvent affecter particulièrement les espèces d'amphibiens qui dépendent de certains types de milieux humides pour la reproduction, comme les étangs de tourbières et les étangs de castors. Nous avons évalué l'influence des caractéristiques au niveau de l'étang et du paysage sur l'utilisation par les amphibiens de 50 étangs du nord du Québec, Canada, en 2018 et 2019. À l'aide d'enregistreurs acoustiques et de décomptes visuels, nous avons estimé l'occupation des mâles chanteurs et l'abondance des individus métamorphosés et des masses d'œufs de trois espèces d'amphibiens: la Grenouille des bois (Lithobates sylvaticus), la Grenouille du Nord (Lithobates septentrionalis) et la Rainette crucifère (Pseudacris crucifer). Nous avons quantifié l'influence des variables de l'étang telles que le type d'habitat, la superficie de l'étang, la présence de poissons, le pH de l'eau et les variables du paysage sur l'occupation et l'abondance. Nous n'avons trouvé aucun effet des variables explicatives sur la probabilité d'occupation des mâles chanteurs des trois espèces. La probabilité de détection des chorales des Rainettes crucifère augmentait avec la température de l'air. L'abondance des individus métamorphosés de Grenouilles du Nord diminuait avec l'augmentation de la superficie des étangs et augmentait avec le pH de l'eau. L'effort reproducteur de la Grenouille des bois, quantifié par l'abondance de masses d'œufs, était plus de quatre fois supérieur dans les étangs de castors que dans les étangs de tourbières. Les résultats de notre étude constituent une référence pour orienter les décisions de gestion concernant la conservation des assemblages d'amphibiens dans les milieux humides de plus en plus perturbés du nord du Canada.

Since the 1980s, there has been rapid and ongoing hypothesized climate-related range expansion in native Green Treefrogs (Hyla cinerea) northward and eastward in Illinois, Kentucky, and Indiana, United States. Because anuran leg length is positively correlated with locomotor function, longer legs have been shown to facilitate dispersal of invasive anuran populations undergoing biological invasion. These recent range-expansion populations of H. cinerea provide an ideal opportunity to test if a native frog species exhibits similar changes in dispersal-related traits to those found in invasive species. We tested if individuals on the front end of this expansion exhibit significant differences in femur length when compared with frogs collected from the historical-range distribution. We predicted that frogs found at the expansion edge would have longer femur lengths than their counterparts located in historical parts of the range. We found that relative to snout–vent length (SVL), the femur lengths (FL) of H. cinerea from expanded ranges were on average significantly larger than those of frogs from the historical range. This suggests that native expanded-range populations of this species have undergone changes in FL. Rapid shifts in morphological traits of a native species, H. cinerea, in expanded-range populations, appear to mimic morphological trade-offs observed for invasive species of anurans.

Associations among behavioral and morphological traits are of interest to biologists because they imply functional relationships at the behavior/morphology interface. We investigated the association between escape behavior and aposematic versus cryptic coloration in two species of Neotropical frogs, namely, Craugaster fitzingeri and Oophaga pumilio. Craugaster fitzingeri is cryptically colored, whereas O. pumilio is an aposematically colored “Poison Dart Frog.” Specifically, we predicted that the cryptic C. fitzingeri would exhibit faster and directionally more erratic escape behavior than the aposematic O. pumilio. We tested this hypothesis by measuring escape speed and variation in turning angles of frogs in their natural habitat. Results indicated that C. fitzingeri has faster and directionally less predictable escape behavior than O. pumilio. Two evolutionary mechanisms may have linked escape behavior and coloration. One possibility is that aposematism in the dendrobatid lineage has relaxed selection and enabled a reduction in speed and unpredictability of escape behavior. A second possibility is that aposematic coloration has actively favored reduction in escape behavior, i.e., slow directionally predictable movements may enhance warning display and increase the efficacy of the aposematic signal.

Las asociaciones entre rasgos conductuales y morfológicos son de interés para los biólogos porque implican relaciones funcionales en la interfase comportamiento/morfología. Investigamos la asociación entre el comportamiento de escape y la coloración aposemática versus críptica en dos especies de ranas neotropicales: Craugaster fitzingeri y Oophaga pumilio. Las ranas C. fitzingeri tienen colores crípticos, mientras que las O. pumilio tienen colores aposemáticos como las “ranas dardo venenoso”. Específicamente, predijimos que las crípticas C. fitzingeri exhibirían un comportamiento de escape más rápido y en dirección más errática que las aposemáticas O. pumilio. Probamos esto midiendo la velocidad de escape y la variación en los ángulos de giro de las ranas en su hábitat natural. Los resultados indicaron que C. fitzingeri tiene un comportamiento de escape más rápido y direccionalmente menos predecible que O. pumilio. Dos mecanismos evolutivos pueden haber vinculado el comportamiento de escape y la coloración. Una posibilidad es que el aposematismo en el linaje dendrobátido haya relajado la selección y permitido una reducción en la velocidad y la imprevisibilidad del comportamiento de escape. Una segunda posibilidad es que la coloración aposemática haya favorecido activamente una reducción en el comportamiento de escape, es decir, los movimientos lentos y direccionalmente predecibles pueden mejorar la visualización de advertencia y aumentar la eficacia de la señal aposemática.

Animals that frequently encounter toxins often develop mechanisms of toxin resistance over evolutionary time. Both predators that consume toxic prey and organisms in physical contact with a toxin in their environment may experience natural selection for resistance. Based on observations that Pacific Chorus Frogs (Pseudacris regilla) sometimes eat and mistakenly amplect tetrodotoxin (TTX)-defended Taricha newts, we predicted that P. regilla may possess TTX resistance. We compared amino acid sequences of domain IV of the muscle voltage-gated sodium channel gene SCN4A (Na_V1.4) in populations of P. regilla that are sympatric and allopatric with Taricha. We identified a single substitution in Na_V1.4 of P. regilla at a conserved site in the pore loop where TTX binds. Although the role of this site in TTX resistance has not been functionally assessed, both allopatric and sympatric P. regilla had this substitution, along with several other reptiles and amphibians, suggesting that it may be unrelated to TTX exposure from Taricha. Thus, there is no conclusive evidence that P. regilla possesses TTX resistance encoded by amino acid substitutions in this domain. California occurrence data from the last 50 yr indicate that Taricha activity peaks in January while the activity of P. regilla peaks in April, with times where the species may come into contact. However, P. regilla may not be exposed to levels of TTX from Taricha high enough to select for mutations in Na_V1.4. Other unidentified mechanisms of TTX resistance could be present in P. regilla and other species sympatric with toxic newts.

Los animales que están expuestos frecuentemente a toxinas suelen desarrollar mecanismos de resistencia a las mismas a lo largo de su historia evolutiva. Tanto los depredadores que consumen presas tóxicas como los organismos en contacto físico con una toxina o contaminante en su entorno pueden experimentar presiones de selección natural hacia mecanismos de resistencia. Observaciones de campo han reportado a las ranas coro del Pacífico (Pseudacris regilla) comiendo y amplexando por error a salamandras del género Taricha que secretan tetrodotoxina (TTX). Por lo tanto, surge la hipótesis de que P. regilla podría poseer resistencia al TTX. Probamos esta hipótesis comparando las secuencias de aminoácidos del gen del canal de sodio voltaje dependiente muscular SCN4A (NaV1.4), que es una proteína diana de la TTX, en poblaciones de P. regilla que son simpátricas y alopátricas con Taricha. Identificamos una única sustitución en NaV1.4 de P. regilla en un sitio conservado en el ploop del poro donde se une la TTX. Aunque el papel de este sitio en la resistencia a la TTX no ha sido evaluada funcionalmente, tanto las P. regilla alopátricas como en las poblaciones simpátricas tenían esta sustitución, junto con varios otros reptiles y anfibios, lo que sugiere que esta sustitución no está relacionada con la exposición a la TTX. Por lo tanto, no hay pruebas concluyentes de que P. regilla posee resistencia a la TTX debida a cambios aminoacidícos en el dominio IV. Por otro lado, los datos de ocurrencia en California de los últimos 50 años indican que la actividad de Taricha alcanza su máximo en enero, mientras que la actividad de P. regilla alcanza su máximo en abril, con algunos momentos en los que las especies se superponen en actividad y pueden entrar en contacto. Sin embargo, es posible que P. regilla no esté expuesta a niveles de TTX de Taricha lo suficientemente altos como ejercer una presión de selección que fije mutaciones en el canal de sodio. No obstante, otros mecanismos no identificados para adquirir resistencia al TTX podrían estar presentes en P. regilla y otras especies simpáticas a las salamandras tóxicas.

Productivity of warm deserts is highly correlated with rainfall. We analyzed body size data from a 35-yr study of Coachella Fringe-Toed Lizards, Uma inornata, to reveal precipitation-related differences among years both in growth and in the length–mass relationship (LMR). The LMR is a linear function enabling comparison of regression coefficients among groups. Adult male U. inornata were significantly larger and their maximum size differed substantially from that of females. Comparing regression coefficients of LMR between sexes revealed equal slopes, although intercepts differed slightly but significantly. We treated the sexes independently to test for seasonal and rainfall differences. Comparing seasonal differences among adults revealed that slopes were not parallel. Regression coefficients predicted that individuals weighed more in spring than in fall, which we attribute to winter rainfall. This was corroborated by recapture data. LMR slopes for extreme dry, extreme wet, and typical rainfall years were parallel, but the elevation for typical years differed significantly from both dry and wet years: they were heavier in typical years. Growth was slower in dry years than in wet or typical years. Differences in growth rates affect time to maturity. We used the production relation model of juvenile growth to estimate time to minimum reproductive size. Time to maturity is doubled during dry years in comparison with wet years (542 vs. 288 d for females, 400 vs. 200 d for males). Together, delayed maturity and predicted future increases in drought frequency and intensity imply conservation concerns for this protected species.

The trajectory of biological research may be affected by historical factors (such as locations of influential researchers) as well as by underlying biological dimensions (such as species diversity and location of potential study taxa). Such influences on research focus can be clarified by examining the topics of published papers. Based on 93,816 scientific papers published on snake biology since 1804 (from Web of Science), we found a nonrandom distribution of research output among snake clades, fields of research, and geographic locations and strong changes through time in overall research effort as well as in the foci of that work. Snakes have been the subject of more scientific papers than other lineages of reptiles, but research on turtles has been increasing faster, and research effort per species has been higher for smaller reptile lineages. Studies on systematics and taxonomy dominated snake research until the mid-20th century, when the field was overtaken by studies of venoms, ecology, morphology, and physiology. Colubrids and Vipers have been the most intensively studied taxa, reflecting a concentration of research on continents (Europe and the Americas) where these taxa are diverse and abundant. Research effort on Vipers (Viperidae) increased around 1920, reflecting advances in antivenom and radiotelemetry technology. Blindsnakes (Scolecophidia) and smaller families remain relatively neglected in absolute terms. The numbers of papers per species are 10-fold greater for North American and European snakes than those in most other regions. We attribute these nonrandom patterns to temporal and spatial variation in research priorities, methods, and availability of scientific infrastructure.

The ability to identify individuals is essential for determining population demographics of a species, but traditional marking techniques, such as passive integrated transponder tags, are often limited to individuals that meet minimum size thresholds. Visible implant elastomer (VIE) and visible implant alpha (VI Alpha) tags are promising methods for marking small-bodied individuals. However, the efficacy and health effects of VIE and VI Alpha tags are not established for many, increasingly imperiled, herpetofauna. Over a 12-mo period, we examined tag retention, tag readability, VIE tag color readability, and effects on growth and body condition of VIE and VI Alpha tags in larval Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis), a species of conservation concern. We observed 100% retention of VIE tags and 80% retention of VI Alpha tags over 1 yr. Readability degraded over time for both tag types but was consistently higher for VIE relative to VI Alpha tags. Degradation in readability over time increased our reliance on a 450-nm-wavelength VI light to read VIE tags but had more severe implications for VI Alpha codes, which were illegible after 4 mo. Pink- and green-colored VIE tags performed similarly well and we found that neither VIE nor VI Alpha tags negatively affected growth or body condition of larval hellbenders. Our findings collectively suggest that VI Alpha tags are an unviable tagging method, but VIE tags were safe and effective for identifying unique larval hellbenders up to 1 yr.

The effects of timber harvest on amphibians can be complex and persist for years postharvest, but overall they are poorly understood. We examined how timber harvest has impacted two pool-breeding species, Spotted Salamander (Ambystoma maculatum) and Wood Frog (Lithobates sylvaticus), across the Canaan Valley National Wildlife Refuge, West Virginia, USA. We surveyed Spotted Salamanders and Wood Frogs at 49 pools from 2004 to 2016. Pools in recently harvested tracts tended to be smaller and less likely to hold water than pools in unharvested tracts for the duration of the breeding period. For both species, mean egg mass abundance was lower in harvested tracts than in the unharvested tracts, and over time declined substantially for Wood Frogs. Similarly, occupancy rates were lower in harvested sites for the duration of the study for both species. Occupancy rates declined over time for both species across all sites; this decline was steeper for Wood Frogs in harvested sites. Our results show the importance of long-term landscape-level studies when evaluating the effects of habitat disturbance. Understanding how forest loss and degradation impact pool-breeding amphibians will help to develop better management targets and mitigate compounding factors of decline to promote survival of these species.

Bokermannohyla treefrogs produce a rich array of acoustic signals in their vocal repertoires. Here we report and describe for the first time the vocalizations of B. caramaschii, a species lacking vocal slits. We also extend the known vocal repertoire of B. gouveai by describing a previously unreported note type and revisiting intraspecific variation based on an increased sample of recorded males. The advertisement call of both species is composed of two types of multipulsed notes with emphasized sound energy at low frequencies (<1 kHz). We discuss the possible implications of lack of vocal slits for production of vocal sounds by B. caramaschii. Furthermore, we address inconsistencies in the previous call description of B. gouveai and reassess the species' acoustic variation based on an increased sample size of topotypes. Lastly, we provide the first overview of the advertisement call diversity within Bokermannohyla, recognizing major temporal patterns of their calls.

Many organisms respond to environmental change by altering the timing of various life-cycle events. Understanding an organism's phenology, therefore, is crucial for predicting the effects of anthropogenic impacts such as climate change. Nevertheless, collecting adequate data to test hypotheses in secretive species is difficult, especially for rare behaviors. We integrated data from online citizen science platforms, published literature, and unpublished studies to clarify the seasonal timing of copulation in Terrapene ornata, a behavior that is rarely observed. We identified 132 copulation events involving an estimated 256 individual turtles: 19 instances from 5,465 photo-vouchered observations, 78 from 11 publications, and 35 from radiotracking 267 turtles for 8 yr across five sites. Copulations in T. ornata occurred in every month from April to October, with the fewest records in April and October. We found no copulation records in two months of purported aboveground activity (March and November), suggesting that mating in the wild may not occur at any time during the active season. The frequency of reproductive events exhibited multimodality with evident peaks in May and September. Records from the northern portion of the species' range were most frequent in the spring, whereas southern records were most frequent in the fall. Our approach generated a large number of empirical records for a rare behavior in a secretive species across vast spatial scales, which would not have been possible using any of the individual data sources alone.

Knowledge of the extraordinary species richness of Australian desert lizards has expanded as new approaches integrating morphological and genetic data reveal unsuspected differentiation. The genus Ctenophorus is a major arid zone radiation and the most species-rich Australian agamid clade. The monophyletic C. maculatus complex, the sand dragons, occupy most sandy arid and semiarid habitats across southern Australia. Published molecular data on nominal C. maculatus complex species, C. fordi, C. femoralis, and C. maculatus, suggested undescribed species presence, supported by dorsal color pattern and male throat and chest patch variation. We provide additional morphological data from all candidate species, recognizing a total of 11 species. Four taxa are elevations of subspecies to species, and four taxa are newly described species. Ctenophorus maculatus complex species vary interspecifically in sexual size dimorphism and dichromatism, with a mating system of nonterritorial males, contrasting with some other territorial Ctenophorus species. The diversity and high local abundance of these lizards make them a potential model group for furthering understanding of interactions between natural selection and sexual selection leading to speciation.