Across a breadth of animal taxa, early-life environmental variation has been demonstrated to have lasting effects on later-life traits, including brain morphology. Here, we use Plains Spadefoot Toads (Spea bombifrons) to evaluate how larval diet type and amount influence later-stage, juvenile brain size and the relative sizes of brain regions. We specifically investigate whether developmental plasticity in brain morphology mirrors previously documented interspecific variation with relation to nutritional restriction and carnivory. Our findings demonstrate, contrary to expectation, that exposure to dietary restriction during the larval stage causes an increase in relative juvenile brain size. However, consistent with our predictions, consuming a prey-based shrimp diet during the larval stage results in relatively larger juvenile telencephalons, an intraspecific response that parallels an interspecific pattern in frogs where more-carnivorous species possess relatively larger telencephalons. Our results demonstrate that early-life dietary restriction and early-life diet type can generate changes in juvenile brain size and morphology in ways that may influence later-life behaviors and fitness. Further, our study suggests that intraspecific and environmentally induced changes in brain morphology can mirror interspecific divergence in brain morphology, supporting a role for developmental plasticity in promoting evolutionary change.

An individual's behavioral tendencies (i.e., personality or temperament) can influence its interactions with the environment and thus have important ecological and evolutionary consequences for animal populations. Boldness, defined as an individual's tendency to engage in risk-taking activities, is a phenotypically variable trait linked with numerous behavioral and fitness outcomes in free-ranging animals. We examined variation and repeatability of boldness and other behavioral characteristics in two wild Eastern Box Turtle (Terrapene carolina carolina) populations using radiotelemetry, and assessed fitness correlates of boldness over multiple years. We observed large amounts of among-individual variation and within-individual consistency (i.e., repeatability) of boldness as measured by their head emergence latency following a standardized confinement assay. Individuals were also consistent in several in-field behaviors including movement rate, home range size, and date of emergence from overwintering refuges. Individuals with shorter head emergence latencies (i.e., bolder turtles) had larger home ranges, emerged earlier from overwintering dormancy, and experienced moderately lower survival compared with shy individuals. Boldness did not affect time spent within the thermal preference range, somatic growth rates, or the frequency of mating or same-sex aggressive encounters. Boldness and its effects on in-field behaviors differed between sexes and populations, and the relationship between boldness and survival was temporally variable. Our results suggest possible intrinsic behavioral types in T. c. carolina and highlight the importance of long-term and multipopulation studies when examining ecological and evolutionary processes that shape personality phenotypes in turtles.

Environmental perturbations such as chemical spills often have immediate and obvious effects on the health of ecosystems and individual organisms. However, the long-term effects of such perturbations are less evident and often less well-understood. In July 2010, a ruptured pipeline spilled diluted bitumen into the Kalamazoo River in Michigan, USA, ultimately oiling 56 km of the river channel. During spill cleanup operations, the most common vertebrate species rescued from the oiled river channel was the Northern Map Turtle (Graptemys geographica), of which over 2000 individuals were captured, cleaned of oil, and released. We returned to areas along the 2010 spill gradient to determine whether turtles from locations that had experienced different magnitudes of oiling in 2010 differed in baseline stress levels or immune functioning in 2020, which was 10 yr after the oil spill. In 2020, we collected blood samples from 100 individual Northern Map Turtles along the 2010 spill gradient and subsequently quantified the heterophil:lymphocyte ratio, bactericidal capacity, and natural antibody agglutination. We found no correlation between turtles' 2020 capture locations relative to the origin of the 2010 oil spill and either mean stress level (heterophil:lymphocyte ratio) or immune functioning (bactericidal capacity and natural antibody agglutination ability). Thus, we found no evidence that Northern Map Turtles sampled along a gradient of oil exposure resulting from the 2010 Kalamazoo River oil spill experienced long-term effects on physiological stress levels or immune functioning. Importantly, our sampling did not include any individuals that may have died during 2010–2020 from poor health after the oil spill and therefore is biased toward healthy turtles remaining in the population. Interestingly, we found that a subset of turtles known to have been oiled in 2010 actually had higher natural antibody titers than turtles sampled from a control site that presumably had never been exposed to oil. We cannot exclude the possibility of other long-term effects of the oil spill on the Map Turtle population, such as decreased reproductive output. We recommend that long-term monitoring of populations and ecosystems be included in spill mitigation plans to track the recovery of populations and ecosystems over time and to document any effects that may become evident only years after the spill event.

Enforced winter inactivity affects life histories of cool-climate squamates in two ways: (1) a trade-off between oviparity and viviparity favoring the predominance of viviparity in cool climates; (2) reduction in frequency of reproduction in females. In this study we determined annual variation in reproductive traits in a cool-climate population of a viviparous lizard (Elgaria coerulea), as well as year-to-year patterns of breeding (versus skipping reproduction) of individual adult females. We collected reproductive data during a mark–recapture study in southeastern British Columbia, Canada. Gravid females were captured in the field and subsequently gave birth under seminatural conditions in the laboratory, whereupon the resulting newborns were measured. There were no differences in snout–vent length (SVL), relative tail length, or age of gravid females among years. Only head width, mass, and condition of newborns varied among years. Most litters consisted of >80% live young, and the proportion of live young in a litter increased with newborn condition and SVL. Litter size increased with maternal SVL, and mean newborn SVL was highest with medium-sized maternal relative tail length. Most females (87%) did not reproduce annually but had one or more years between reproductive events. There was no effect of year on whether a given female was reproductive, but larger females and females with intact tails were more likely to be pregnant in any year. The possible consequences of skipping reproduction in a given year include trading off immediate investment in offspring against increased growth in the current year and higher potential future reproductive output. Testing such hypotheses will be challenging but would contribute significantly to our understanding of the evolution of reproductive effort in both squamates in particular, and animals in general.

Many animal taxa perform stereotyped displays during ritualized contests over territory and mates. Such displays facilitate assessment of an opponent's prowess and reduce the probability of physical injury. Color patterns likewise can serve as indicators of an individual's body condition. Male San Cristóbal Lava Lizards (Microlophus bivittatus) of the Galápagos Islands possess a black epaulet on each shoulder that contrasts with their surrounding body coloration. We created robots with the appearance of conspecific males to explore the potential function(s) of the epaulets in a series of four experiments. Our experiments focused on epaulet presence/absence, body location, and location relative to the axis of body motion (pectoral versus pelvic girdle) during pushups. Paired trials were conducted with adult males and females using a robot that performed M. bivittatus signature displays and that differed on its two sides in epaulet attributes. We quantified two kinds of bobbing displays in subjects: signature displays and two-bob displays. We also computed a composite response (CR) score, in which point values were assigned to types of nonbobbing displays and display combinations according to the apparent level of subject aggression. Results of Experiment 1 showed that males (but not females) performed more signature displays to the side of the robot with the epaulet present than to the side with the epaulet absent, suggesting that epaulets serve a signaling function. Composite response scores did not differ between treatments for either sex. In Experiment 2 neither males nor females performed more bobbing displays to an enlarged epaulet than to an epaulet reduced in size. However, males exhibited greater CR scores to the enlarged epaulet, suggesting that epaulet size or conspicuousness is important to its function. In Experiment 3 neither sex produced more bobbing displays to an epaulet on the robot's shoulder than to one on its hip. Yet, males accumulated significantly larger CR scores in response to the shoulder epaulet than to the hip epaulet, indicating that males were aware of normal epaulet location. Finally, in Experiment 4, where our robot performed hindlimb rather than forelimb pushups, subjects failed to exhibit more bobbing displays in response to a shoulder epaulet than to a hip epaulet. CR scores also did not differ between treatments for either sex, perhaps due to the striking abnormality of hindlimb-driven bobbing displays. Although the function of M. bivittatus epaulets remains elusive, these markings clearly are salient to male conspecifics.

Human land transformation alters features of the landscape that may favor or eliminate biodiversity. Understanding habitat use among species in human-affected ecosystems can inform the management of habitats and conservation of species. The Trans-Mexican Volcanic Belt in central Mexico is a biological hot spot for lizard species diversity that is under considerable anthropogenic pressures including grazing, agriculture, urbanization, and climate change. Here, we used species-occupancy modeling to (1) identify habitat characteristics that are essential to predicting the presence of Sceloporus torquatus and S. grammicus lizards, (2) determine if disturbance predicts species occupancy, and (3) determine which features, if any, predict our ability to detect each species in the wild. We found that S. torquatus lizards were more likely to be present in areas with large boulders and abundant refuges, whereas S. grammicus lizards were more common in forests with leaf litter. Human disturbance and urban disruption did not predict the occupancy of either species, with lizards making use of artificial as well as natural refuges in human settlements as well as protected areas. Although we found only weak evidence that habitat and climate predicted detection probabilities, Sceloporus lizards (particularly S. grammicus) were somewhat more easily detected in high humidity, perhaps because of generally higher activity levels. Our results emphasize the importance of understanding the detailed physical characteristics that allow each species to persist, even in disturbed habitats. This can better inform conservation efforts so that resources are allocated to ensure that these characteristics, like rocks and trees, are readily available in both pristine and human-modified areas.

Sampling biases resulting from capture methodology or animal behavioral responses can significantly skew our understanding of population size and structure. Behavioral responses to passive sampling with traps, such as trap-happy or trap-shy responses, can be accounted for in analyses using individual covariates but they require detailed understanding of the underlying behavioral mechanisms. We used a field experiment to investigate the impact of trap escape on capture rates and determine what traits influence trap escape rates between and within two species of semiaquatic snakes, Liodytes pygaea and Nerodia fasciata. We found that L. pygaea escaped significantly more often than did N. fasciata, smaller L. pygaea escaped at significantly higher rates than did larger conspecifics, and individual capture history significantly influenced escape rates in N. fasciata. Our findings highlight understudied sources of inter- and intraspecific capture heterogeneity in a common sampling technique, and we urge researchers to consider method-specific sampling biases when attempting to produce population parameter estimates for species that are difficult to detect.

We described a new species of Dendrophryniscus from the Mantiqueira Mountains, a mountain range in the Atlantic Forest in the state of Minas Gerais, Brazil. Dendrophryniscus cuca sp. nov. is known only from its type locality, the private Protected Area Chapada͂o da Serra Negra, municipality of Santa Bárbara do Monte Verde. The new species is morphologically distinguished from its congeners mainly by the combination of the following characters: medium size for the genus, longitudinal set of granules posterior to the corner of mouth, fingers neither fringed nor webbed, and presence of nuptial pads in males. Molecular analysis of the 16S mitochondrial DNA indicates a genetic distance range from 2.39% (D. brevipollicatus) to 17.92% (D. carvalhoi). Individuals were found in bromeliads, and we described a male–male amplexus with the presence of release vibrations, but calling activity was not observed. This is the fourth endemic anuran species of the Serra Negra da Mantiqueira, part of the Mantiqueira mountain range (Serra Negra da Mantiqueira), highlighting the importance of the region for the Neotropical herpetofauna.