Elaborate visual signals play a crucial role in communication between many breeding animals, often evolving through female mate choice and male–male competition. Neotropical Yellow Toads (Incilius luetkenii) exhibit a temporary elaborate visual trait during their brief annual mating events, transitioning from a drab, female-like brown coloration to a vibrant lemon-yellow. They engage in scramble competition, where males physically compete with both lone and amplectant males for access to females. Previous studies suggest that male color may serve as a sex identification signal in the toads' large breeding aggregations, and that females do not appear to choose males based on color. In this study we investigated whether variation in male coloration functions as an intrasexual signal during male–male interactions. Using realistic robotic model toads in a two-choice arena, we addressed two questions. First, do male Yellow Toads respond differently to a lone male versus a male in amplexus with a female when both males are the same color? Secondly, do male Yellow Toads respond differently to two amplectant males varying in the brightness of their yellow coloration? Males approached the amplectant pair nearly twice as often as the lone male, although this pattern was not statistically significant. Males did not exhibit a differential reaction to bright amplectant males versus dull amplectant males. Therefore, variation in male yellow color and the presence of a female do not appear to influence male–male competitive behavior. Overall, this study contributes to our understanding of temporary color change in vibrantly colored anuran species.

Reptiles and amphibians are disproportionately threatened among vertebrates but are lagging behind other vertebrate taxa with regards to conservation plans. As the need to triage data-limited species becomes ever more necessary, calls for conservation priorities to be based on evolutionary considerations are increasing. Although there now exists a large body of literature documenting insight that theory can provide to conservation, complex life cycles of many reptiles and amphibians prevents a simple transference of management principles derived from other vertebrate taxa. Thus, there is a need for a set of principles that acknowledges the unique ecology and diversity of herpetofauna. Here we present 10 key principles from evolutionary ecology that can provide rules of thumb to guide management of reptiles and amphibians. Broadly, we identify five landscape-related principles and five life-history–related principles that account for novel ways in which reptiles and amphibians are shaped by the environments they inhabit. When considered in combination they can be useful in providing a holistic view of a species' status. We hope this paper facilitates identification of species that are in critical need of management intervention and provides a guide for managers and conservation scientists to proactively mitigate extinction risk.

Effective management of rare wildlife species requires a clear understanding of population dynamics based on robust estimates of demographic parameters, yet these data are lacking for many taxa, including the federally and State-of-California threatened Alameda Whipsnakes (Masticophis lateralis euryxanthus, AWS). Alameda Whipsnakes are colubrids found over a limited geographical area at the margins of the densely populated San Francisco Bay Area region. Despite their threatened status, little has been published about the population dynamics of this species. Our main objective was to develop age and growth relationships and growth rates for the AWS. We completed a five-year capture-recapture study targeting a population in the Los Vaqueros Reservoir watershed in Contra Costa County, California, USA, and applied and compared the fit of three classic growth models (von Bertalanffy, logistic, and Gompertz) to length-at-age data. We also assessed growth rates of AWS across ages, and estimated female size and age at reproductive maturity. We found no evidence of sexual dimorphism in our sample. The logistic growth model produced biased results and was ignored. In a leave-one-out information criterion (LOOIC) model comparison of the von Bertalanffy and Gompertz models, the Gompertz model had 100% of the weight. Predicted age for the largest observed individual under this model was 8.3 years. As expected, predicted annual growth rates declined with age, specifically, from 0.61 mm/day at small sizes to 0.01 mm/day at large sizes. The model-predicted age of the smallest gravid female was 2.2 years. The new information about the AWS reported here is an important starting point for future efforts to understand the life history and quantify the population dynamics of this rare snake.

The tympanic middle ear (TME) is a complex morphological adaptation that facilitates auditory reception in multiple clades of tetrapods, including anurans. Despite its utility, it has been partially or completely lost at least 38 times in anurans, and there is no clear explanation for how or why this loss occurred. We used micro-CT scans and 3D segmentation to catalog presence/absence and shape of the columella throughout the Central American toad genus Incilius. We found that the TME has been lost multiple times in Incilius and our outgroup Rhinella, with at least one regaining event. Absence of the columella and the different shapes of the columella both have high phylogenetic signal. Incilius species have a different distribution of columella shapes than many other genera of anurans that have been surveyed, including more blade-shaped columellae than found in other genera and one species with vestigial remnants of a columella. The columella shape most common in Incilius, a blade, may be derived from the rod shape also found in many other bufonids; the adaptive significance of this trait remains unknown. This study succeeds in providing a fine-scale review of earlessness and columellar morphology in Incilius, but the processes underlying the patterns we observe remain unclear.

Sympatric species are expected to differ in resource use in order to avoid competition, leading to niche partitioning in natural communities. Invasive species can disrupt community structure, but these impacts are often difficult to measure. In this study, we used stable isotope analysis of carbon and nitrogen to investigate dietary niche partitioning of freshwater turtle assemblages at three sites in the Middle Rio Grande Basin of New Mexico. We sampled four turtle species common to the region, including Painted Turtles (Chrysemys picta), Spiny Softshells (Apalone spinifera), Common Snapping Turtles (Chelydra serpentina), and invasive Red-Eared Sliders (Trachemys scripta elegans). We found that species composition at the study site with the most anthropogenic influence, the Rio Grande Nature Center in the urban population center of Albuquerque, was dominated by invasive T. s. elegans, while study sites in more remote areas (Sevilleta and Bosque del Apache National Wildlife Refuges) primarily consisted of native species. Furthermore, we observed high overlap in niche space among turtle species at the Rio Grande Nature Center, but evidence consistent with niche partitioning at the other two sites. We found higher nitrogen levels in the more carnivorous A. spinifera and C. serpentina compared to other species. We also found evidence for an ontogenetic shift toward a less carnivorous diet in T. s. elegans. Our study provides valuable baseline information about understudied turtle assemblages within the Middle Rio Grande region and suggests there is potential for competition between invasive T. s. elegans and native turtle species in New Mexico.

Monitor lizards (Varanidae) are ecologically important components of the Australian fauna and are abundant in Quaternary fossil deposits like those in Naracoorte Caves (South Australia). However, the narrow range of morphological variation in varanids makes identification of their fossil remains difficult. Here we explore use of geometric morphometrics (GM) to assess fossil affinities of varanid cranial material. Five fossils from Naracoorte's Fossil Chamber (Victoria Fossil Cave), represented by two parietals and three dentaries, were included in the GM analysis. Fossils were compared to the parietals and dentaries of reconstructed X-ray computed tomography specimens belonging to modern species that are currently found in the area: Varanus gouldii, Varanus rosenbergi, and Varanus varius. Both dentaries and parietals belonging to these species were consistently distinguished using GM analytical methods, across a range of sizes from immature to large adults. Our sample of fossils were all unambiguously classified as V. varius. The presence of V. varius during the Middle Pleistocene is consistent with forest and woodland environments reconstructed from previous paleoecology and geochemical research for the region. Our results highlight the potential of modern GM methods in identifying Pleistocene fossil material based on comparisons with modern species. Consequently, our paleoecology interpretations and understanding of relationships between changing environments and species distributions over time are greatly improved, with strong implications for species conservation.

Social network analyses are sparse, despite having great potential to illuminate intricate details of wildlife behavioral ecology and to inform basic conservation practices. Using social interactions recorded during 1 year of 5-second interval photography, we conducted social network analyses of Gopher Tortoises (Gopherus polyphemus). G. polyphemus are charismatic and declining mid-sized tortoises that are habitat specialists endemic to the southeastern United States. We also conducted a simultaneous radio-telemetric study of tortoises contained within our study population to ascertain whether home range location is consistent with membership in distinct tortoise social network communities. We found strong statistical support for the presence of nonrandom social networks that were derived from male-female mating relationships. The most parsimonious social network included two distinct “cliques” that were spatially segregated. Each clique contained a similar number of males and females. Understanding this basic aspect of tortoise behavior should be key in basic population biology, not only of turtles but also other reptiles. Our results should influence protocols for successful conservation of this keystone species.

Access to subterranean refugia, such as animal burrows, can affect the ecology and life history of wildlife in an array of habitat types. Subterranean refugia are commonly used for thermal refuge, for shelter from predators, or as suitable locations for nesting and/or brooding offspring; because of this, refugia can potentially impact rates of survivorship and recruitment. In southwestern Florida, Burmese pythons (Python bivittatus), an established and highly impactful invasive species, have been observed using subterranean refugia on numerous occasions. Because python management is an utmost priority in Florida, understanding the potential implications of this behavior is key to mitigating python impacts on native wildlife. We used 29 radio-telemetered Burmese pythons to investigate the extent to which pythons used subterranean refugia in the southwestern portion of their Florida range. We explored spatiotemporal patterns of refuge use and quantitatively assessed how python sex, reproductive season, and habitat type affected the probability of using different types of refugia. We observed pythons using four types of refugia, including Gopher Tortoise burrows, Nine-banded Armadillo burrows, and natural and anthropogenic ground-based cavities. Pythons used these refugia for seeking thermal refuge, aggregating, breeding, and nest brooding, and they were most likely to use refugia during their breeding and nesting seasons. Nine python nests, representing 71% of those discovered during the study, were oviposited and brooded in Gopher Tortoise or Nine-banded Armadillo burrows. Implications of this behavior warrant further assessment and incorporation into management strategies as they may affect Burmese python recruitment, survival, and dispersal.

Global climatic fluctuation has significantly impacted biodiversity by shaping adaptations across numerous species. Pleistocene climate changes notably affected species' geographic distributions and population sizes, especially fostering post-glacial expansions in temperate regions. Evolutionary theory suggests spatial sorting of morphological traits associated with dispersal in recently expanded species. However, evidence of predicted intraspecific trait variation is scant. We investigated intraspecific trait variation in five lizard species along a forest-savanna gradient affected by Pleistocene climate. Lizards serve as an ideal group to test these ideas due to climate's known influence on their morphological traits linked to essential functions like feeding and locomotion. We assessed two hypotheses: (i) niche variation and (ii) spatial sorting. For the niche variation hypothesis, we predicted increased intraspecific variability in head dimensions with distance from stable areas. For spatial sorting, we anticipated larger hind limb sizes with increased distance from stable areas. We gathered data on five quantitative traits from 663 samples across species. There was no evidence supporting either hypothesis across the five species. Limited sample sizes, challenges in habitat modeling, or other factors might explain this lack of support. Nonetheless, our study illuminates complexities in exploring trait variation within species. The data collected here, although inconclusive, represent a crucial test for evolutionary theory.