Northern Pacific Rattlesnakes (Crotalus oreganus oreganus) have a range that extends from southern California into British Columbia. This subspecies is common in relatively warm and arid regions, but also occurs in habitats that are neither warm nor arid. We hypothesized that the presence of suitable microhabitat conditions can compensate for a less suitable macroclimate, allowing C. o. oreganus to exist in less suitable regions. We developed environmental niche models for C. o. oreganus at two spatial scales: (1) northern California and western Oregon, and (2) the northern California coast. These models explored macroclimatic suitability of northern, coastal California relative to other regions within the range of C. o. oreganus. The models revealed that the three most northern and coastal counties of California have a significantly less suitable macroclimate relative to the rest of each study area. Next, we used paired resource selection functions to determine microhabitat differences between rocky outcrops used as hibernacula and outcrops that are unoccupied by rattlesnakes despite similarities. Our analysis indicated selection for outcrops with more deep crevices, less vegetative cover, and slopes facing due south (180° from North). Additionally, we mapped landslides near hibernacula, which revealed that hibernacula commonly occurred within the head-scarps of landslides. We suggest that because landslide triggers (e.g., heavy rainfall and earthquakes) occur frequently along California's north coast, more rocky outcrops are created that are suitable as hibernacula. The relatively high abundance of these suitable outcrops compensates for the marginal macroclimate, allowing C. o. oreganus to occur in the region.

The local spatial distribution of individual animals is often described in terms of home range (HR), whereas territory traditionally refers to an area defended for exclusive use. The size of the HR is considered an important indicator of the behavioral characteristics of an animal, and it can be influenced by factors such as sex, body size, population density, and social behavior. In polymorphic species, morphs may differ in space use, and they may be characterized by different reproductive strategies. The aim of this study is to quantify space use in a population of the lizard Liolaemus xanthoviridis (Iguania: Liolaemini) and its relationship with body size, sex, and color polymorphism. At a single locality in Argentina (Bahía Isla Escondida, Chubut), over four summer seasons (2012–2015) we marked 156 lizards and recorded body measurements, sex, dorsal and ventral color patterns, and the spatial location of each individual. Our results showed that HR size differed significantly between sexes and was significantly associated with body sizes in males, but not with dorsal coloration and ventral melanism. Moreover, males of L. xanthoviridis have a high percentage of overlap in their HRs. The absence of a relationship between HR size and dorsal coloration or ventral melanism suggests the absence of multiple reproductive strategies within each sex. Because females of L. xanthoviridis seem to be territorial, but not males, we propose that they may be interacting in a system of dominance hierarchies, a hypothesis that needs behavioral testing.

Ecological studies strive to identify factors that explain patterns of species distribution and abundance. In lizards, competition and predation are major forces influencing distribution and abundance, but there is also increasing evidence pointing at the influence of habitat structure and prey abundance. Our work explored the latter further by quantifying the effects of vegetation and prey abundance on occupancy and abundance (i.e., estimated probability of detecting more than two individuals) of two sympatrically occurring species in the northern karst belt of Puerto Rico. We hypothesized that Anolis cristatellus would occur in trunk–ground substrates and Anolis krugi on grass–bush substrates according to their ecomorphological classification. We also hypothesized that prey abundance, a component of habitat quality, would have a positive and strong effect on occupancy and abundance. Anolis cristatellus exhibited high occupancy rates (>0.80), influenced by mid-story tree size. A. cristatellus abundance fluctuated over time, with highest probability of detecting two or more individuals in January–March and July–September when prey abundance transitioned from low to high levels. Occupancy of A. krugi was positively influenced by sapling density and prey abundance. Prey abundance exerted a stronger influence on occupancy, but its influence on abundance was negative and strong. Biological interactions and the type of understory substrates may explain the negative relationship. Our study supported predicted relationships between ecomorphology and habitat, but also showed that higher prey abundance may not always translate to higher local abundance. We shed light on these interactions, knowledge needed to advance anole conservation in the advent of land use and climate change.

The negative effects of roads on wildlife have been well studied, and their mitigation is considered of critical importance to conservation. Mitigation of these threats commonly incorporates exclusion fencing and landscape connectivity structures, but the mechanics of mitigation success and species-specific responses are poorly understood. Eastern Gartersnakes (Thamnophis sirtalis sirtalis) are an ubiquitous species and frequently victims of road mortality, so we conducted a “willingness to utilize” (WTU) experiment to understand snake behavior when interacting with ecopassages. Snakes were exposed to newly installed ecopassages at Presqu'ile Provincial Park (10 m long × 0.5 m wide × 0.32 m tall). Naïve snakes and snakes with ecopassage experience were introduced to one of two arena options: 1) a completely closed-in arena, only allowing snakes to enter the ecopassage, or 2) a similar arena with two exits allowing snakes to bypass the ecopassage, more reflective of a real-life scenario. All snakes entered the ecopassage when given no other option. When given options to bypass the ecopassage, at least 59% of snakes still chose to enter the ecopassage, regardless of trial design or prior ecopassage experience, suggesting that in general, there is neither aversion nor attraction to ecopassages. Most snakes made their choice within 30 sec and neither temperature nor traffic affected crossing duration; however, experienced snakes crossed the ecopassage faster than naïve snakes. This study shows the use of a common mitigation structure by a widespread species and supports how these mitigation efforts are ultimately increasing our ability to successfully mitigate negative road-effects.

Detection has been a long-standing challenge to monitoring populations of cryptic herpetofauna, which often have detection probabilities that are closer to zero than to one. Burmese Pythons (Python bivittatus [=Python molurus bivittatus]), a recent invader in the Greater Everglades Ecosystem of Florida, are cryptic snakes that have long periods of inactivity. In addition, management actions such as removal of every python encountered create challenges for estimating population size and quantifying effects of management using traditional statistical approaches. We used Bayesian analysis of data collected from 59 visual surveys (144 person-surveys) covering a total distance of 485.6 km (1,185.1 person-km) and radiotelemetry to estimate detection probability for Burmese Pythons. These estimates can improve interpretation of encounter and removal data. We found that detection probability ranged from 0.0001 to 0.0146 depending on whether effort units accounted for total human effort across multiple surveyors and statistical method used. On the basis of our surveys, detection probabilities for Burmese Pythons are therefore likely <0.05, but factors such as the number of searchers or time of day may improve detection probability. Traditional capture–recapture or visual surveys are, however, unlikely to yield accurate information on Burmese Python population size or trends across time without cost-prohibitive effort. Consequently, novel methods development to monitor or measure Burmese Python populations, including techniques better equipped to handle very low detection, are critically needed for informative and reliable inferences about population size or the management effects of python removal.

Knowledge on long-term population trends in crocodilians is essential to assess the effectiveness of conservation areas and to guide sustainable management practices. We studied changes in population size of spectacled (Caiman crocodilus) and black caimans (Melanosuchus niger) over a period of 17 yr at Mateococha, a black-water lake located in Cuyabeno Wildlife Reserve, western Amazonia, Ecuador. Using standardized spotlight counts and two mark–recapture surveys, we estimated the population abundance, body size structure, and sex ratio in 1994, 2004, and 2011. The maximum number of C. crocodilus recorded in 1994 (147 individuals; 33 individuals/kilometer [ind/km] of lakeshore) declined by 2004 to 94 individuals (21.1 ind/km) and by 2011 to 63 individuals (14.2 ind/km). The number of M. niger recorded was low but constant (5–7 individuals; 1.1–1.6 ind/km) throughout the study, suggesting that factors causing the decline in C. crocodilus were not related to the M. niger population trend. Large C. crocodilus adults (total length 150–220 cm) were frequent in 1994 but became rare in 2004 and 2011. The sex ratio of captured C. crocodilus was male-biased during all periods. The causes of the population decline are unknown, but available evidence suggests that illegal hunting and habitat degradation are likely culprits despite the protected status of the Cuyabeno Reserve. Our findings question the effectiveness of protected areas to ensure long-term survival of caiman populations in Ecuador.

Common Kraits, Bungarus caeruleus, cause thousands of fatalities annually in Asia. Here, we aimed to examine stomach contents of preserved kraits to determine their most favored prey animals that might attract them to residences where they bite sleeping people, even under mosquito nets. We examined freshly killed B. caeruleus and those preserved in collections maintained in hospitals and museums during July 2016 to October 2018 to identify contents of their stomachs and intestines. Among 61 examined B. caeruleus, three kraits consumed frogs, three consumed snakes, one consumed a bird, and five consumed rodents. This is the first comprehensive study of the food spectrum of B. caeruleus for Nepal and the third study worldwide. Unlike previous findings, we found the snakes mainly feeding on nonsnake prey animals. Most snakes having empty stomachs and a few specimens with freshly eaten prey animals indicated their entry into dwellings in search of prey animals was because of food stimuli. Findings of partly digested rodents, frogs, snakes, and avian prey (which are commonly found in houses in the lowlands of Nepal) further support food stimuli to be an important factor driving B. caeruleus to residential areas, where they often cause envenomation (69% of total specimens involved in snakebite, n = 42). Our findings can be extrapolated to understand the feeding ecology of B. caeruleus distributed in residential areas and to formulate effective prevention strategies against their bites. Implementing effective and practicable prevention strategies lessens the fear of snakes. This consequently minimizes unnecessary killing of snakes, which in turn contributes to biodiversity conservation.

West Indian rock iguanas (genus Cyclura) represent the most endangered group of lizards in the world, with most taxa restricted to few or single islands. In addition to distribution and availability of resources, factors influencing optimal use of insular space in these large vertebrates may include a combination of social, ontogenetic, and long-term demographic factors. Life stage-specific dispersal and habitat use patterns have previously been characterized in Cyclura, but assessments across the lifespan are lacking. This study evaluates shifting patterns of movement in a single taxon, Cyclura nubila caymanensis. We used mark–recapture and radio tracking simultaneously to assess age- and sex-dependent variation in spatial ecology. Evidence for prolonged site fidelity among adults was consistent with territoriality-modulating space use in this long-lived taxon. Over 5–10 yr, some females were never resighted or recaptured outside of an 80-m perimeter. A notable exception was that gravid females migrated 1.17 ± 0.91 km to utilize coastal areas during the nesting season. In contrast, neonates dispersed farther (2.32 ± 2.26 km) and their trajectories were often nonlinear. Radio-tracked brother–sister pairs exhibited no tendency to disperse together during their first 4 wk, settling into final known locations at pairwise distances of 2.16 ± 1.74 km. Annual net displacement remained high over the first 1–3 yr of life. Our data are consistent with studies of related taxa wherein individual spatial requirements vary with population density and island size. Notably, panmixis of small island iguana populations appears largely driven by pre-reproductive movements.

We quantified and compared movement and microhabitat use of Eastern Copperheads (Agkistrodon contortrix) in fragmented and unfragmented habitats to determine the effects of fragmentation on movement and habitat use. We used thread bobbins to track movement and calculate straight-line distance (SLD) moved, total distance (TDM) moved, and occupied area for individual snakes. Microhabitat use was characterized by quantifying number of trees, woody vegetation stems, herbaceous vegetation stems, percent grass coverage, and percent canopy coverage at each location a snake was observed, and at an equal number of randomly selected locations. Neither SLD nor TDM differed between fragmented and unfragmented habitats. Overall average SLD moved was 24.1 m and TDM was 39.6 m over 48 h. Although SLD and TDM did not differ between sites, mean occupied area ± standard error was significantly greater at the unfragmented (2,310.9 ± 272.7 m) compared with the fragmented site (1,025.9 ± 314.9 m). Microhabitat features were similar between the fragmented and unfragmented sites, and herbaceous vegetation and high canopy cover were associated with locations where snakes were observed at both sites. It is likely that Eastern Copperheads can persist in a variety of habitats in the southeastern United States because their preferred microhabitat features are widely distributed and common in both fragmented and unfragmented environments, demonstrating that they retain characteristics of a habitat specialist within heterogeneous environments suitable for generalists.

Genetic differentiation plays an integral role in species persistence. However, it remains challenging to quantify the ways in which the degree of isolation affects animal populations. The Common Toad (Bufo bufo) is a species of conservation concern, particularly in the UK, where populations have undergone large-scale declines. There are two types of isolation that are relevant to toad population persistence. These are: 1) isolation by distance (IBD), where populations that are further apart become more isolated with time; and 2) isolation by barrier (IBB), where the presence of barriers to movement can isolate populations. Both IBB and IBD are relevant to Common Toad survival, and thus conservation, in fragmented landscapes typical of farmlands. We collected Common Toad genetic material from eight different breeding ponds amongst the rural farmland landscapes of Oxfordshire, England to test the effect of IBD and IBB on toad genetic differentiation. We detected no significant effect of IBD (range 2–22 km between breeding ponds) on Common Toad genetic differentiation at this scale. We did, however, identify a significant and positive relationship between IBB and Common Toad genetic differentiation. Breeding populations were more genetically different with increasing barrier distance. The lack of a relationship between IBD and toad genetic differentiation could suggest that Common Toads are not as philopatric as previously thought, with reduced availability of suitable breeding ponds possibly driving more migrants to disperse greater distances and thereby possibly improving genetic mixing of the metapopulation.

The transition from species in allopatry to sympatry, that is, the co-occurrence zone, allows for investigation of forces structuring range limits and provides evidence of the evolutionary and population responses of competing species, including mechanisms facilitating co-occurrence (e.g., character displacement). The Shenandoah Salamander (Plethodon shenandoah), an endangered plethodontid, is limited to three mountaintops in Shenandoah National Park, Virginia, USA. This species' distributional limits are attributed to competitive exclusion by the Red-Backed Salamander (Plethodon cinereus). Recent work showed range overlap between these species is greater than previously thought, requiring investigation of species morphology, behavior, and demographic measures in single-species and co-occurrence zones that might facilitate such overlap. We analyzed individual characteristics from 2 yr of transect surveys to see whether traits differed within and outside co-occurrence zones. Measures showed species- and zonal-specific differences, but we found limited support for character displacement. Both species were larger in the co-occurrence zone, indicating larger salamanders might better compete for resources or that symmetric competition restricts dispersal or recruitment processes at the co-occurrence zone. Microhabitat use also differed by species across transects, with Red-Backed Salamanders using more rock microhabitats in the co-occurrence zone, potentially because of competition for microclimates that minimize physiological stress. The lack of strong evidence of differentiation in situ at the range edge suggests weaker character displacement and potentially weaker competition than previously thought, with other factors contributing to the range limits of Shenandoah Salamanders.

While shell diseases may be often encountered in captive aquatic turtles maintained in less than optimum conditions, cases of nonulcerating shell disease in wild populations are rare. We discovered lesions on the carapace of individual Kinosternon flavescens (Yellow Mud Turtle) adapted to a highly aquatic existence in the artificial ponds of a cattle ranch in the Chihuahuan Desert of west Texas. Because the carapacial lesions seemed to represent a continuum of a single process, we followed the gross changes in the lesions on turtles over a 13-yr period, testing the hypothesis that we were seeing a progressive shell disease. We confirmed our working hypothesis as we observed Arnoldiella chelonum, a common, filamentous alga, protruding from enlarged pores in newly formed shell and growing under translucent shell lamellae. As the disease advanced, our gross and histological studies revealed that algae were found between more of the shell lamellae, eventually culminating with sloughing of lamellae. Erosion of lamellae led to a localized but complete loss of portions of the scute and exposure of underlying bone. We provide data on the occurrence of this condition among the marked population and progression of the lesions to more-severe forms in individual turtles. Studies of specimens in research collections provided evidence of our observed disease process in K. flavescens across time and throughout the distribution of the species in Texas. We suggest that, by capitalizing on permanent artificial water sources, K. flavescens has serendipitously allowed A. chelonum to invade and damage the nonliving portion of the shell.

Multiple mating is common in Sea Turtles, and previous studies have suggested that levels of multiple paternity are higher in larger rookeries compared with smaller rookeries. As a result, smaller rookeries may be more vulnerable to the loss of genetic variation than would larger rookeries. The critically endangered Kemp's Ridley Sea Turtle (Lepidochelys kempii) has a single high-density rookery (∼5,000 females) in Rancho Nuevo, Mexico, where high levels of multiple paternity were reported (81% of nests). A secondary nesting colony was re-established on Padre Island National Seashore, Texas, USA, in the early 1980s and, by 2010, 140 nests were found along the entire Texas coast. The relatively small size of the Texas rookery led us to predict low levels of multiple paternity compared with Rancho Nuevo, and we tested our hypothesis by genotyping 158 hatchling tissue samples from 25 nests on South Padre Island (SPI) at 14 microsatellite loci. Full sibship reconstruction indicated that multiple paternity occurred in 47.6% of nests, a value that is significantly lower than the 81% of nests in Rancho Nuevo. Genetic diversity on SPI was high (H_O = 0.80) and similar to Rancho Nuevo, although there was a genetic signal of a population bottleneck at SPI. Multiple paternity, small geographic range, and extensive movements by individuals probably act to maintain high genetic variation in this species, despite severe population declines.

We describe a new species of Amphisbaena from the Caatinga of northeastern Brazil. The new taxon is identified mainly by having 216–239 body annuli, 13–17 caudal annuli without autotomic site, 4–8 (usually six) precloacal pores without a median hiatus, 18–24 dorsal and 18–24 ventral segments at a midbody annulus, 4 supralabials, 3 infralabials, and postmalar row present. The continued discovery of new amphisbaenians from Caatinga highlights the insufficient current knowledge regarding the diversity of this group in this semiarid region.

The geology of the Pleistocene, and particularly the Last Glacial Maximum approximately 26.5 ka, is a critical driver of species present-day distributions and levels of genetic diversity in northern regions. Using mitochondrial DNA sequence data, we tested several predictions relating to the postglacial recolonization of the northern United States and southern Canada by Mudpuppies (Necturus maculosus). Our analyses revealed a significant split between western and eastern lineages, with the divide corresponding to the location of the Mississippi River. Our data support the presence of one or more Mississippian glacial refugia, with subsequent expansion and diversification of a western cluster into the upper Midwest and an eastern cluster into the eastern Great Lakes and New England. As predicted in cases of postglacial colonization, each of these clusters contains a single widespread and common haplotype along with numerous low-frequency, closely related haplotypes. Given recent conservation concerns about amphibians in general, and Mudpuppies specifically, we discuss our results in light of species conservation. Knowledge of a species' genetic diversity allows for informed management and facilitates decisions that preserve local adaptation and evolutionary potential.