We studied diet and size-related dietary patterns among American Crocodiles (Crocodylus acutus) in marine habitats of coastal Belize (1996–1997). Prey items recovered from crocodile (N = 97) stomach contents included insects, mollusks, crustaceans, fish, amphibians, reptiles, birds, and mammals. Based on an overlapping group analysis of percent occurrence, we concluded that hatchlings and small juveniles feed largely on insects and crustaceans, larger juveniles broaden their diet to include fish and nonfish vertebrates, subadults consume increasing amounts of crustaceans with lesser amounts of insects and nonfish vertebrates, and adults subsist primarily on marine crustaceans. Dietary diversity was uniformly low across all size classes but greatest among small and large juveniles. Conversely, hatchlings, subadults, and adults had the most specialized (least diverse) diet owing to reliance upon a limited selection of prey, largely insects (hatchlings) or crustaceans (subadults and adults). Dietary overlap was greatest between adjacent size classes and lowest between the largest and smallest size classes. The high prevalence of freshly ingested prey among all size classes indicates frequent, regular feeding by C. acutus in coastal habitats, perhaps driven by the relatively small size of frequently consumed prey such as crabs. Because crabs have a blood salt content equivalent to the external medium and comprise a large portion of the diet, these prey likely impose a high osmoregulatory burden on C. acutus inhabiting hyperosmotic coastal environments. Contrary to earlier assertions that salt glands in C. acutus lack the excretory capacity to balance salt and water, we suggest populations in coastal Belize rely on these glands in addition to behavioral strategies to maintain osmotic homeostasis.

Crocodilians show a broad plateau of thermal independence for sustained activity. It has been hypothesized that this reflects a performance breadth necessary for carrying out ecologically important behaviors across a range of ambient temperatures. Here, we swam Saltwater Crocodiles (Crocodylus porosus) in a thermally controlled flume at 23, 28, and 33°C and recorded oxygen consumption (VO₂) before and after swimming activity. Ambient temperature altered spontaneous VO₂ in a positively linear manner, but there was no significant difference in the distance the crocodiles would swim voluntarily. Excess postexercise oxygen consumption (EPOC) increased 10-fold between swimming trials at 28 and 33°C, and the anaerobic debt took 3 times longer to clear at the higher temperature. The results show that, although C. porosus demonstrated a broad thermal breadth for swimming performance, a higher degree of anaerobic metabolism was required to sustain activity at the upper limits of the thermal plateau. Why crocodiles should choose to sustain an anerobic debt rather than reduce their swimming activity when exposed to high experimental temperatures is perplexing, but the study findings provide a physiological rationale for some of the diel and seasonal activity patterns observed in wild crocodilians.

The harvest and incubation of American Alligator (Alligator mississippiensis) eggs is an important component to the commercial alligator harvest industry in the southeastern United States. As a result, various methodologies have been used to monitor alligator populations including abundance counts, stress quantification, and nesting surveys. Past studies have dismissed the importance of egg shape in crocodilians, Squamates, and turtles and deemed egg shape in birds and other amniotes as similar, in relation to functionality. The complexity of crocodilian eggs has been examined, and both turtle and Squamate eggs have been regarded recently as physiologically more intricate than bird eggs. This study introduces a physiological approach to monitor alligator populations in freshwater and low salinity environments by quantifying egg shape in correlation with varying salinity. We introduce a fractional semilandmark-shape template method to quantify egg shape within a geometric morphometric framework. This approach is beneficial because it allows for the quantification of shape for curved structures, such as eggs, which lack homologous landmarks. The results from this study suggest that alligator egg shape is correlated with varying salinity levels, such that variation in alligator egg shape at low salinities changes in gradient-like fashion, whereas salinities high enough to be deemed stressful result in reversion back to a low salinity egg shape or desiccation. This study elucidates a correlation that can be implemented in management and breeding techniques and opens the door to in-depth physiological examination of the system.

Microsatellite markers were used to investigate the mating system of the Estuarine Crocodile (Crocodylus porosus). Three-hundred and eighty-six hatchlings from 13 clutches from a wild Northern Territory population, and 364 hatchlings from 21 clutches from a captive North Queensland population, were sampled. All samples were genotyped across five microsatellite loci. Multiple paternity was found in 69% of clutches in the wild population compared to 38% of clutches in the captive population. Up to three possible fathers were indicated in some clutches. Shared paternity was suggested by the presence of a common paternal genotype within two clutches in the wild population and among up to three clutches from a large shared pen in the captive population. The probability of detecting multiple paternity at all loci was high; 95% in the wild population and 98% in the captive population. There was no evidence of increased hatching success in the clutches that indicated multiple paternity compared to single paternity clutches in either population (P = 0.43 to P = 0.67). It is unknown whether the occurrence of multiple paternity in C. porosus is a result of multiple mating within the same breeding season or of sperm stored from matings in a previous season. These results suggest the genetic mating system for C. porosus is not polygynous but more likely promiscuous, and there is no evidence of dominant alpha males who control paternity in large areas.

Populations of Saltwater Crocodiles (Crocodylus porosus) have been monitored in the Northern Territory since the species' protection. This monitoring relies on standardized spotlight surveys in which crocodiles are counted and classified by estimated total length (TL). Although the accurate estimation of TL is important for analyses, often crocodiles are submerged and their TL is estimated from their heads, which may be visible above the water surface. With some variation, it is generally thought that TL of a crocodile is seven times the length of the animal's head. This study examined the ratio of TL to head length (HL) from morphological measurements of 2,755 Saltwater Crocodiles caught in various locations in the Northern Territory. The results showed that the generic ratio for crocodiles ranging from 38 to 503 cm was 7.01. The ratio increased logistically from 6.7 to 7.1 for crocodiles in the 120–420-cm size range in TL in 30-cm intervals. We suggest that TL can be reliably estimated from HL at least for crocodiles in 120–420 cm in the wild, with the use of the generic and size-specific ratios calculated for the various size classes at every 30 cm. The size-specific estimation for animals <120 cm or >420 cm was not possible because of limited sample sizes in these crocodile size ranges, although a few reliable records suggest that a ratio increasingly becomes larger and 1:8 should be used for crocodiles >510 cm in TL.

The Siamese Crocodile (Crocodylus siamensis) is critically endangered and, until a decade ago, few remaining wild populations were known to exist. Described here are the first in-depth surveys for C. siamensis in Laos with new field data on ecology and conservation. Small breeding populations of C. siamensis are confirmed to persist in Laos. During surveys between 2003 and 2008, C. siamensis was recorded in 13 sites of six river systems, where at least 36 individuals (1–11 per site) were documented. In all sites, crocodile densities and recruitment rates were extremely low. Eight nests were recorded—among the first wild nests of C. siamensis to be reported. Perennial, thickly vegetated floodplain lakes are critical dry-season refugia and breeding habitats for C. siamensis in Laos. Opportunistic collection of crocodiles by local communities was observed, and at all sites there is increasing degradation of floodplain lakes for agriculture or economic development. National crocodile records were compiled and indicate that, historically, C. siamensis was widespread in lowland riverine and palustrine habitats of Laos, with most records from Central and South Laos in the Mekong Plain. These records also suggest that a severe range decline has occurred over the past century, although most wetlands remain unsurveyed for crocodiles. Crocodylus siamensis is probably now extirpated from the Lao Mekong and many other wetlands. Remnant C. siamensis populations in Laos are of global importance. All documented breeding sites, and most confirmed national records, are in rural lands outside the national protected area system, and conservation efforts will require community-based approaches.

We investigated the attributes of shelters used by Eastern Hellbenders (Cryptobranchus alleganiensis alleganiensis) in two 500-m stretches of the French Broad River basin in North Carolina during June 2010. We quantified attributes at each Hellbender shelter and at a corresponding unoccupied shelter located <25 m away to determine whether the attributes selected differed from those available in the surrounding environment. We identified 41 Hellbender shelters, each occupied by a single animal. Hellbenders selected shelters that had larger cover rocks and deeper cavities than the unoccupied shelters. No other attributes differed between occupied and unoccupied shelters, and there were no significant relationships between total length of Hellbenders and size of the cover rock or cavity depth. All Hellbender shelters were formed by large rocks with flat bottoms. Most had a single entrance that was oriented downstream and a cavity floor consisting of sand and gravel. Shelters were generally located in shallow, fast-flowing water with <10% of their surface area embedded in the substrate. Our results suggest that Hellbenders prefer shelters with attributes that maximize cavity space. Larger cavities likely provide greater protection from predators and greater concealment from sunlight. In addition, larger cavities allow more space for Hellbenders to rock back and forth to maximize oxygen uptake through their skin during periods of low flow when oxygen levels drop.

The Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) is a large, completely aquatic salamander native to the eastern United States. Hellbender populations have experienced numerical declines and range contractions over a large geographic area, but few demographic data are available to allow biologists to diagnose specific causes of the declines. We estimated survival of Hellbenders in Indiana using radio telemetry. We monitored 21 adult eastern Hellbenders during July 2008–October 2009 and documented three mortalities. Using a known-fate model, we estimated annual survival as 0.804 (±0.089 SE). This estimate is lower than expected for a long-lived species and signals the continued decline of Hellbenders in Indiana. Estimates of survivorship such as this provide baseline data for translocation programs and are useful in parameterizing population models.

The Western Lesser Siren, Siren intermedia nettingi, is a fully aquatic, paedomorphic salamander. The foraging ecology of S. i. nettingi is poorly understood in part because of its nocturnal, benthic nature. We examined sensory mediation of S. i. nettingi foraging behavior focusing on how chemical and visual stimuli may be used to find prey. Specifically, sirens were observed in a test chamber that gave them the option of associating with a control stimulus or either a visual or a chemical prey stimulus. Our paired t-tests indicate a significant difference between the treatment and control groups for chemical stimuli but not for visual stimuli, and this is confirmed by our one-sample t-tests that indicated a significant difference from 50% for chemical but not for visual stimuli. These results suggest that Western Lesser Sirens use chemical cues over visual cues when foraging. Our results are logical considering that sirens have noticeably reduced eyes and are thought to be nocturnal foragers. This study contributes to the limited natural history knowledge of an amphibian species that is often a top predator in the aquatic systems in which it is found.

Eastern Hellbender (Cryptobranchus alleganiensis alleganiensis) populations are experiencing drastic declines range-wide. Effective conservation strategies require understanding the environmental factors underlying population occurrence within the stream networks that Eastern Hellbenders inhabit. We contrasted habitat elements between historically occupied and apparently unoccupied sites throughout the Susquehanna River Basin in New York, an area that represents the northernmost segment of the species' range. Historically occupied sites contained larger rocks and less soft sediment than unoccupied sites. Regional-scale predictive models of Eastern Hellbender distribution in Pennsylvania indicated that specific geologic features—loamy till, clayey to loamy till, and mixed origin sand and gravel deposits—as well as extensive forest cover were the strongest predictors of Eastern Hellbender occurrence. We conclude that occurrence is dependent on isolated and uncommon geological features that cause the species' distribution to be highly patchy and that stream sedimentation is a major threat to this species in its northern range. Our research also indicates that predictive modeling can be useful in examining drivers of Eastern Hellbender distribution and targeting regions for population surveys and habitat conservation.

Animals in high predation environments tend to react to predators more quickly and effectively compared to animals in low predation environments. Because antipredator behavior can be increased by predator introductions and decreased by predator losses, we examined whether populations occurring outside of a predator's range are associated with behavioral changes. Genetic evidence indicates that Side-blotched Lizards (Uta stansburiana) radiated into the northern portions of their range relatively recently and rapidly. As such, Uta populations exist in the presence or absence of various predators. We studied four populations of Uta in Oregon and Nevada to test for behavioral differences among populations that co-occur with different predators. We measured several behavioral traits thought to be associated with predator exposure and used predation-pressure estimates for each population to show that movement and display behavior vary among sites but tend to be negatively affected by predation environment. However, an important determinant of these relationships is the estimate of predation pressure itself. These results suggest that conspicuous behavior in lizards is reduced in the face of increased predation pressure but that variation among populations may obscure this pattern.

Few data exist that quantify evasive behavior in postmetamorphic anurans. On the basis of our casual observations that Oregon Spotted Frogs (Rana pretiosa) from one of two different populations appeared to exhibit a more pronounced evasive response, we used a pseudopredator stimulus to quantify the evasive response of juveniles from the two populations. We drew test animals from a pool of animals for each population that were captive-reared under identical conditions. Using latency to initial response, we compared the distribution of response times between the two populations at two sequential intervals over the rearing period. In both experiments, the Conboy Lake population had shorter latency-to-response times than the Black River population. However, we also found that latency-to-response times were shorter during the second test interval than during the first test interval for each population. The basis of population differences in response times may reside in differences in the predator set influencing each population, contaminants differentially influencing the Black River population in a negative manner, or some combination of both. Explanation for the faster latency-to-response times in the second experiment is unclear since both maturation and the length of the captive rearing interval may contribute to the effect, but they are confounded in this study.

According to kin selection theory, competition among monoclonal animals must be lower than between unrelated individuals. Thus, we propose that home range and core area overlap in parthenogenetic lizards will be broader than female range overlap in similar gonochoristic species. To test this hypothesis, we examined home range locations and space use of parthenogenetic Armenian Rock Lizards (Darevskia armeniaca) and compared them with home range locations and space use of gonochoristic species. We demonstrated that parthenogenetic Rock Lizards have a total range structure typical of insectivorous lizards, consisting of a sally zone, a home range, and one or more core areas. Some core areas contained activity centers, associated strongly with key basking sites and shelters. Provisional residents were found within the same range for 1 or 2 years, whereas wanderers visited study sites for 1 or 2 weeks per season. Settlement structure varied greatly among years. Home ranges, core areas, and even activity centers and basking sites of parthenogenetic females overlapped extensively, unlike in females of nonparthenogenic species. Monoclonal origins and high level of relatedness within unisexual species are possible explanations of the extended range overlap among parthenogenetic females.

Nocturnal activity is important for many animals, but difficulty in documenting that activity has hampered efforts to understand factors that influence when animals are active at night. We used automated radiotelemetry to provide the first detailed tests of the hypothesis that the nocturnal activity of free-ranging snakes should be influenced by temperature, moon phase, and prey abundance by using data for Ratsnakes (Pantherophis spp.) from Texas and Illinois. Ratsnakes exhibited some nocturnal behavior throughout their active season in both Texas and Illinois, although snakes were much more active at night in Texas than in Illinois. Texas snakes transitioned from primarily diurnal activity to primarily nocturnal activity over this snake's active season, whereas Illinois snakes were always most active in the middle of the day. For both populations, nocturnal activity was positively related to temperature but unrelated to moon phase. Ratsnakes in Texas exhibited a stepwise increase in nocturnal activity in mid-summer, independent of temperature and coincident with the shift in their diet to almost exclusively mammals active at night. Given the ability of snakes in both populations to be active at night when temperatures allow, warming climates could lead to an increase in nocturnal activity, with consequences for both the snakes and the species on which they prey.

A reliable method for the confirmation of sex in Geocrinia frogs is currently unavailable. A captive colony of Geocrinia frogs was used to determine whether fecal steroid analysis could be used as a noninvasive method of sex diagnosis in mature frogs. Linear discriminate analysis, using measured concentrations of fecal hormones, also was applied to establish whether a reliable model could be developed to verify the sex of juvenile frogs. Fecal samples were collected over a 3-month period from all frogs in 2010, and again from 12 frogs in 2011. Samples were pooled for each individual and tested for testosterone metabolites (TMs) and estrone conjugate metabolites (EMs) using enzyme immunoassays. Mature male frogs had higher (P < 0.01) mean TM : EM ratios than those of mature females, with mature male and female ratio ranges being 100% distinct. Mature female frogs had higher (P < 0.01) mean EM concentrations than those of mature males, but EM concentrations overlapped between the sexes in 18.7% of cases. There was no statistical difference (P = 0.28) between mature males and females in mean or range of TM concentration, with overlap between the sexes in 75% of cases. Juveniles had hormone values similar to those recorded for mature male and female frogs. Generated discriminate rules were able to distinguish (100%) between mature males and females and correctly classified the sex of 75% of the juvenile frogs. It was concluded that fecal steroid analysis offers a promising, noninvasive approach to sex identification in Geocrinia frogs.

Valley fills associated with mountaintop-removal mining bury stream headwaters and affect water quality and ecological function of reaches below fills. We quantified relative abundance of streamside salamanders in southern West Virginia during 2002 in three streams below valley fills (VFS) and in three reference streams (RS). We surveyed 36 10- × 2-m stream transects, once in summer and fall, paired by order and structure. Of 2,343 salamanders captured, 66.7% were from RS. Total salamanders (adults plus larvae) were more abundant in RS than VFS for first-order and second-order reaches. Adult salamanders had greater abundance in first-order reaches of RS than VFS. Larval salamanders were more abundant in second-order reaches of RS than VFS. No stream width or mesohabitat variables differed between VFS and RS. Only two cover variables differed. Silt cover, greater in VFS than RS first-order reaches, is a likely contributor to reduced abundance of salamanders in VFS. Second-order RS had more boulder cover than second-order VFS, which may have contributed to the higher total and larval salamander abundance in RS. Water chemistry assessments of our VFS and RS reported elevated levels of metal and ion concentrations in VFS, which can depress macroinvertebrate populations and likely affect salamander abundance. Valley fills appear to have significant negative effects on stream salamander abundance due to alterations in habitat structure, water quality and chemistry, and macroinvertebrate communities in streams below fills.

Research that investigates the impact of invasive plants on reptiles, particularly snakes, is sparse. Butler's Gartersnake (Thamnophis butleri) is a rare snake, endemic to the upper midwestern United States. Little research has focused on the habitat selection of this snake, which is often sympatric with the Common Gartersnake (Thamnophis sirtalis). The highly invasive wetland grass Phalaris arundinacea (reed canarygrass [RCG]) has become established or dominant throughout much of the geographic distributions of these snakes. The impacts of this invasive grass on the habitat selection of T. butleri and T. sirtalis have not previously been examined. During 2 yr of drift fence surveys at three survey sites and five habitats sampled in southeastern Wisconsin, we captured 243 adult T. butleri and 311 adult T. sirtalis. Thamnophis sirtalis was found more often in RCG than T. butleri, which appeared to have more specific habitat needs and most often occurred in upland habitats, particularly grassland, rather than wetlands. These findings have important regulatory and conservation implications for the globally rare T. butleri. For example, our data support the importance of upland habitat protection as part of conservation strategies for T. butleri. In addition, management of wetland habitat for this species must consider the impact of RCG and direct habitat restoration strategies accordingly.

We examined seasonal reproductive patterns of the Del Norte Salamander, Plethodon elongatus, in mixed conifer and hardwood forests of northwestern California and southwestern Oregon. Seasonal size differences in reproductive structures suggested that maximum spermatogenic activity occurred during the late summer, with spermatozoa transfer to the vasa deferentia occurring in the fall through spring. Maximum development of mature follicles occurred during the winter; however, follicular growth occurred year-round and was asynchronous among individuals. Courtship and mating probably occurred in late fall through early spring, with egg deposition from spring into early summer. Reproduction for females was not annual, and patterns suggested that the reproductive cycle was biennial or less frequent. In contrast, evidence indicated annual reproduction in males. Gravid females contained an average of 10 mature follicles.

Quasipaa verrucospinosa, the Granular Spiny Frog, is a discoglossid frog endemic to Vietnam and known only from its original description. We report the discovery of three populations of this species and describe the reproductive, fat body, and liver mass cycles for males and females. Results showed that males reached sexual maturity at 98.36 mm snout–vent length (SVL) and an age of nine months. Females reached sexual maturity at 109.45 mm SVL and an age of 11 months. Testes of males began to increase in volume in late June, and maximal testicular activity occurred from September to December. Testis size began to decrease in January and was smallest in April. Histological analyses revealed that sperm were not present throughout the year, indicating discontinuous reproductive activity for adult males. Reproductive females were observed only during the main rainy season months, indicating that females reproduce seasonally. The gonads of females began to increase in volume in July and maximal egg production occurred during the main rainy season (September to December). Females started to lay their eggs in July, and there were significant differences among mean clutch size and numbers of oviductal eggs or yolked follicles, vitellogenic follicles, and nonvitellogenic follicles. Clutch size was correlated significantly with female SVL and varied between seasons and months. The results of multiple regression analyses indicated that precipitation, but not temperature, was associated positively with testicular and ovarian volume.

Field observations and lab studies were carried out on the Rough-tailed Gecko (Cyrtopodion scabrum) in the Suez Canal Zone to assess sexual size dimorphism, activity, habitat selection, growth rate, diet, and reproduction. Cyrtopodion scabrum showed no significant sexual difference in body size and head shape characters. The lizard's maximum activity was in autumn and the minimum in winter, with peaks of daily activity during the first 3 h following sunset; air temperature was a major factor controlling daily and seasonal activity of C. scabrum. Lizards were solitary and had small home ranges. They occupied all available substrates and assumed different positions at heights ranging from 5 to 500 cm above the ground. The greatest rate of growth occurred in spring, and growth ceased altogether during winter. Lizards with the smallest snout–vent length had the highest growth rate. A total of 14 arthropod orders were recorded in the diet of C. scabrum; dipterans and hymenopterans dominated in number and volume, respectively. Cyrtopodion scabrum showed evidence of a sit-and-wait foraging mode. Males and females both ate prey of similar numbers and sizes; however, lizard stomachs were filled with food in spring more than any other season, which may indicate the lizard's increased need for energy for reproduction. The reproductive season extended from March through September. Peak reproductive activity for both sexes was in June and July. Female C. scabrum deposited single-egg clutches more commonly than two-egg clutches and displayed communal nesting, which was previously unrecorded for the species.

A deep understanding of the processes affecting the population dynamics of living organisms requires fine-scale analyses of basic demographic parameters such as stage-specific survival and growth rates. In this study we estimated survival, detection, and transition rates (growth) for different stages of the life cycle of a Knob-scaled Lizard of the genus Xenosaurus. We also examined potential sources of variation for these parameters by means of a multiple-model inference framework. Our capture–mark–recapture data revealed that survival rates were homogeneous among stage classes but markedly different between the rainy and dry seasons. Contrary to our expectation, survival probability was higher during dry months. Detection probability varied considerably among stage classes and through time. Consistent with theoretical predictions, the rate at which lizards moved from a particular stage class to the following (transition rates) varied among stage classes, with the fastest rates observed in yearlings and the slowest in adults. Also consistent with our predictions, we found a tendency toward faster transition rates during rainy months. We discuss the potential causes and implications of the patterns of variation observed in these key demographic parameters.

While many amphibian species around the world are experiencing catastrophic declines, we have little understanding of the population dynamics of the majority of species. Estimating demographic parameters can help us understand the spatial and temporal dynamics of healthy populations, assess how populations may be impacted by threats, and interpret the recovery of diminished populations. Capture–mark–recapture (CMR) techniques represent a powerful approach for estimating such vital rates, but they have been used rarely in studies of tropical amphibians. We use 5 yr of mark–recapture data (2000–2004) to estimate survival probabilities and abundances of the stream-breeding frog species Espadarana (Centrolene) prosoblepon prior to the arrival of Batrachochytrium dendrobatidis, the amphibian chytrid fungus. We estimated these parameters for male E. prosoblepon on four streams (Cascada, Guabal, Loop, and Silenciosa) in Parque Nacional Omar Torríjos in central Panama. Across all streams and years, mean annual survival probability was 0.46 (0.41–0.52, 95% CI). Abundance varied among streams, with larger population sizes on Loop (78 ± 12 SE) and Cascada (64 ± 4) and smaller population sizes on Guabal (28 ± 3) and Silenciosa (30 ± 2), but showed little difference among years. Streams with different abundances had similar survival rates, and we suggest that availability of overhanging vegetation—used for oviposition and male territories—limits population size. These are the first survival and abundance estimates that exist for this species. They provide a critical baseline for comparison to other healthy populations and for evaluating recovery in sites infected with the amphibian chytrid fungus.

Bone pathology provides a window to environment and predation, allowing confident comparison of fossils and subfossils with their modern descendents. Exclusive of modern contaminated environments, the frequency of bone disease in frogs does not seem to have changed in the Holocene. Injuries were either quite rare or rarely survived. Associated fractures, however, were frequently infected. Infections appear to have been from a chronic granulomatous disease, apparently fungal in origin. The disorders reported in these fossil bones are identical to those recognized in modern frogs, validating comparison of character and frequency of bone pathology through geological time, as has been documented previously for reptiles and mammals.

Although tail autotomy often has an immediate survival benefit, tail loss may subsequently hinder locomotion and the ability to escape from predators. Maximal locomotor performance can be reduced after tail autotomy in the plethodontid salamander Desmognathus quadramaculatus. The loss of a large proportion of the tail length (>60%) is costly for this semiaquatic species in terms of a reduction in maximal swimming performance (i.e., burst speed is about 50% less after such autotomy). However, the minimal amount of tail loss that causes a significant reduction in swimming performance (i.e., the “critical tail autotomy” for locomotion) is unknown. I examined the effect of partial tail loss (either 15% or 30% of tail length) on burst swimming performance. After the loss of about 15% of tail length in one experimental group (N = 15), burst speeds for individuals were not significantly different from preautotomy burst speeds. After the loss of about 30% of tail length in a second experimental group (N = 15), burst speeds for individuals were significantly less than preautotomy burst speeds. These results indicate that the critical tail autotomy for reduction of maximal swimming performance is between 15% and 30% of tail length. About 50% of individuals in the field (N = 69) experienced tail autotomy and most (80%) of these individuals lost more than 30% of their tails. This study shows that tail autotomy often results in a reduction in maximal swimming performance and thus a locomotor cost for individuals of this species.

We collected plasma samples from adult males in a natural population of Plains Gartersnakes (Thamnophis radix) to characterize seasonal variation in testosterone. As in other New World temperate zone natricines, testosterone was high during spring emergence, declined as courtship and mating progressed, and then increased in late summer and fall. Based on patterns seen in this and other studies, we suggest that the rapidity with which testosterone decreases following spring emergence may be associated with the length of the mating season; and that it decreases rapidly in species and populations in which the mating season is brief and more slowly in species and populations in which mating occurs over an extended period. Testosterone showed a clear, positive association with body condition in adult male Plains Gartersnakes. Whether this association translates into greater reproductive success warrants further investigation. Because we collected blood samples multiple times from individual males within years, we were also able to demonstrate significant individual variation in seasonal testosterone profiles, although how this might relate to individual variation in reproductive behavior is unknown. Given their phylogenetic, ecological, and geographic diversity, New World natricine snakes represent a rich resource for studying hormonal associations with reproductive patterns.

We describe a new species of Stenocercus from the Andes of Ecuador that previously was erroneously assigned to S. guentheri due to its general phenotypic similarity with this species. Based on phylogenetic analyses of mitochondrial DNA sequence data, we show that the new species is not nested within S. guentheri but is actually sister to S. festae. The new species can be distinguished from other Stenocercus by the combination of the following characters: imbricate scales on posterior surface of thighs, smooth ventrals, a posthumeral mite pocket consisting of a shallow depression with a wide opening (more distinct in adult specimens), small scales on occipitoparietal region, supraoculars of similar size, 62–83 scales around midbody, and no black midventral stripe or black transverse band on the ventral surface of neck in adult males.

Describimos una especie nueva de Stenocercus de los Andes de Ecuador, que debido a similitud morfológica estaba erróneamente asignada a S. guentheri. En base a análisis filogenéticos de datos de secuencias de ADN mitocondrial, demostramos que la especie nueva no está anidada dentro de S. guentheri y es la especie hermana de S. festae. La especie nueva se puede diferenciar de otras especies de Stenocercus por la combinación de los siguientes caracteres morfológicos: escamas imbricadas en la superficie posterior de los muslos, ventrales lisas, bolsillo posthumeral poco profundo con una abertura ancha (más marcado en adultos), región occipitoparietal con escamas pequeñas, supraoculares de tamaño homogéneo, 62–83 escamas alrededor del cuerpo, franja medio ventral negra o banda transversal negra en el cuello ausentes.

A new species of Tantilla is described from Refugio de Vida Silvestre Texíguat in northern Honduras. The new species is allocated to the Tantilla taeniata group, which currently contains 20 of the 63 species in the genus, but it differs from all congeners on the basis of its dorsal body pattern and scutellation. The new species has a pale mid-dorsal stripe composed of narrow spots, confined to the mid-dorsal row, and a lateral coloration of pale spots on each of rows 1, 2, and 4 with dark brown pigment on the lateral edges of the ventrals. The new species appears to have no close affinities within the T. taeniata group. Refugio de Vida Silvestre Texíguat is one of the most important cloud and premontane rain forest reserves in eastern nuclear Central America with respect to evolution, species endemism, and conservation. Nonetheless, areas of this reserve are seriously imperiled, especially on the leeward side due to continuing illegal logging and forest clearing for subsistence agriculture.

Una nueva especie de Tantilla es descrita para el Refugio de Vida Silvestre Texíguat en el Norte de Honduras. Se le asigna al grupo de T. taeniata, que actualmente contiene 20 de las 63 especies en el género, pero difiere de todos los congéneres en el patrón de coloración y conteo de escamas. El patrón dorsal del cuerpo de la nueva especie consiste en una línea dorso central pálida confinada a la hilera dorso central, compuesta por manchas estrechas y una coloración lateral de manchas pálidas en cada una de las hileras 1, 2 y 4 con pigmento marrón oscuro en los bordes laterales de las escamas ventrales. La nueva especie parece no tener ninguna relación dentro del grupo de T. taeniata. El Refugio de Vida Silvestre Texíguat es una de las reservas más importantes de bosque lluvioso premontano y bosque nublado en Centro América Nuclear Oriental con respecto a la evolución, el endemismo de especies y la conservación. Sin embargo, las áreas de esta reserva se encuentran en peligro, especialmente en el lado de sotavento debido a la continua tala ilegal y tala para la agricultura de subsistencia.