Snakes exhibit a complex repertoire of defensive responses, shifting from one tactic to another depending upon conditions at the time of encounter with a potential predator. Standardized laboratory trials, controlling factors such as time of day, temperature, and type of encounter, can be used to test predictions about the form of this context dependency. We studied two sympatric species of elapid snakes from southeastern Australia. Although similar in body sizes, habitat use, and nocturnality, small-eyed snakes (Cryptophis nigrescens) are wide foragers (and hence, encounter predators under cool conditions at night in relatively open areas), whereas broad-headed snakes (Hoplocephalus bungaroides) lie in ambush for long periods within sun-warmed rocky retreat sites (and hence, encounter predators mostly when the snake is warm, and within its retreat). Based on those differences, we predicted that small-eyed snakes would be thermal generalists; that is, temperature would exert relatively little effect on the snakes' locomotor abilities, alertness, and preparedness to flee from threat. Broad-headed snakes would be likely to utilize tactics other than fleeing, and to increase response intensity substantially at higher temperatures. Both species were predicted to exhibit more intense responses at night, and when warm. Data from our laboratory trials supported these predictions: (1) antipredator behaviors of small-eyed snakes were less sensitive to thermal variation than were those of broad-headed snakes, (2) both species relied primarily on fleeing, but broad-headed snakes were more likely to adopt retaliatory behavior than were small-eyed snakes, and (3) both species responded more intensely at night and when warm. These results are consistent with the broader theory that snakes flexibly adjust their antipredator tactics to local conditions.

We studied the reproductive cycle of Sceloporus grammicus from two localities in Hidalgo, Mexico: La Estanzuela (LE) and Tilcuautla (TIL) of the Municipality of Mineral del Chico and San Agustín Tlaxiaca, respectively. Males were larger than females in both populations, with males having larger snout–vent lengths (SVLs), heads, and limbs than females. Males from LE reached sexual maturity at a larger SVL (42.2 mm) than males from TIL (38.9 mm). Females from LE reached sexual maturity at a smaller SVL (41.6 mm) than females from TIL (44.6 mm). Reproductive activity of both sexes from both populations was asynchronous. Testicular recrudescence at LE occurred May–July, reaching maximum activity August–October, and showing regression November–December, whereas in TIL, recrudescence occurred May–June, reaching maximum activity July–October, and showing regression November–December. Vitellogenesis occurred May–October in both populations, with ovulation occurring November–December. Embryonic development was observed November–March in both populations. Hatchlings from LE and TIL first appeared in March. Mean litter size for both populations was similar (LE, 4.75; TIL, 4.66) and increased with female SVL. Reproduction of S. grammicus for both populations was different from other montane populations but similar to populations from low elevations.

Horned lizards are difficult to detect because of their cryptic coloration and behavior, but often flee from approaching predators and use specialized behavioral, morphological, and physiological defenses at close quarters. Escape theory predicts that flight initiation distance (predator–prey distance when escape begins) increases as predation risk increases. We predicted that, despite relying on crypsis, Texas horned lizards (Phrynosoma cornutum) would have greater flight initiation distances when approached rapidly than slowly and when approached directly than indirectly. Flight initiation distance was greater for rapid than slow and direct than indirect approach, verifying the predictions for prey that do not rely exclusively on crypsis, forgoing escape. Effect size was larger for approach speed than for directness of approach, in part because the difference between minimum bypass distances was small (0.0 m for direct and 0.6 m for indirect approaches). We also investigated responses to a shadow passing over a lizard, which might be a cue to imminent risk. When a model accipiter passed overhead, lizards were much more likely to move and jump if and when the model cast a shadow directly on them than if the shadow passed nearby without falling on them. Some lizards fled when the shadow fell on them. We interpret these novel findings as indicating that P. cornutum assess themselves as being in immediate peril when suddenly covered by a shadow. They reacted primarily by immediate flight or jumping, possibly reflecting preparation to use alternative defensive strategies at close quarters or to delay escape while further assessing risk. Thus, although Texas horned lizards rely strongly on crypsis, they make escape decisions based on degree of predation risk.

Gopherus polyphemus has experienced severe population declines, especially in the western portion of its range. As a consequence, G. polyphemus may have experienced population bottlenecks that resulted in a decrease in genetic diversity and an accumulation of deleterious alleles. The importance of genetic diversity has been well-documented for several fitness parameters (e.g., survival, disease resistance, growth and developmental rates, and developmental instability). Western populations of G. polyphemus in south Mississippi (USA) have lower hatching success (16.7–48%) than that found in eastern populations (67–97%). Even under laboratory conditions, approximately 40% of the eggs still failed to hatch, suggesting that intrinsic (egg quality) factors may be affecting development. Using nine microsatellite loci, we genotyped individuals from four populations in south Mississippi and one eastern population (Fort Benning, GA) and compared several genetic diversity indices (e.g., allelic richness, expected heterozygosity, and percent polymorphic loci) with published data from populations in the eastern portion of the range, such as populations east of the Mobile and Tombigbee rivers. We found significantly lower genetic diversity in the four Mississippi populations than in the eastern populations. However, these findings only demonstrate that these populations have low genetic diversity, and establishing any causal relationship between low genetic diversity (or other intrinsic factors; e.g., female condition) and reduced reproductive success should be further investigated.

Demographic data are essential to determine the probability that species will persist over time. Unfortunately, demographic studies are rarely part of the initial evaluation of potentially threatened or endangered species. Here, we studied the population dynamics of a poorly known knob-scaled lizard species (Xenosaurus sp.) from México with the use of a population matrix modeling approach. We measured annual fecundity and survival over three consecutive years (2001–2004) and used these data to generate transition matrices. From these matrices we estimated annual variability in finite population growth rate (λ), stable stage structure, and the relative importance of the life-cycle components for λ (elasticity values). In 2 of the 3 yr population growth rates indicated a tendency toward population increase (λ_01–02  =  1.20 and λ_02–03  =  1.14), whereas in 1 of the 3 yr population growth rate indicated population decrease (λ_03–04  =  0.78). The negative population trend observed during 2003–2004 was explained by warmer and drier environmental conditions that caused the lowest observed survival rates in all size classes. We examined this annual demographic variability using stochastic simulations. This allowed us to project population trends under hypothetical scenarios with increasing frequency of unfavorable years, manifest through reduced survival, fecundity, or both. Our simulations revealed that small increases in the frequency of harsh annual conditions vastly increased extinction risk in this species. Given the highly restricted geographic distribution of this species and its susceptibility to extinction, we recommend that it be given a high priority for conservation.

The Amolops monticola group contains approximately 12 morphologically similar species distributed across much of mainland Southeast Asia. Approximately half of the species in the group were described only during the past 6 yr, and several have been erroneously placed in the genus Odorrana. A molecular phylogenetic analysis is performed using three mitochondrial and two nuclear genes sequenced from eight of the 12 putative members of the group. The group is shown to be monophyletic within the genus Amolops. The Indochinese species A. daorum is removed from the synonymy of A. mengyangensis, is shown to be a member of the genus Amolops and not Odorrana, and is found to be paraphyletic with respect to A. iriodes. A newly discovered population in northwestern Laos is described as a new species on the basis of its morphological and molecular distinctiveness.

A new species of medium-sized Sphenomorphus is described from the biogeographically enigmatic island of Palawan in the western Philippines. This species represents only the third skink in the genus Sphenomorphus found on Palawan Island. The new species is compared with other Sphenomorphus found on Palawan and with phenotypically similar species in the genus from throughout its range. To aid in future identification of Sphenomorphus specimens from Palawan, we provide a key to the species from this island.

We describe a new species of Sibon from the Reserva Forestal La Fortuna, Chiriquí Province, Panama. The new species is distinguished from all species presently assigned to Sibon by having 17 rows of dorsal scales at midbody and 15 rows one head length anterior to cloaca (vs. 13 or 15 rows of dorsal scales at midbody without reduction on posterior portion of body in all other species of Sibon), and dorsal scale rows that change orientation from the sides of body toward middorsum (vs. maintaining more or less the same orientation). A key to the Lower Central American species of Sibon is provided.

We describe a new species of Liotyphlops (Serpentes: Anomalepididae) from Ilha de São Sebastião, municipality of Ilhabela, São Paulo state, southeastern Brazil. The new species represents the first record of the genus throughout most of the Atlantic Coastal Forest in São Paulo state. Liotyphlops caissara sp. nov. is related to L. albirostris and L. wilderi, but it can be distinguished from the first species by having a different number of body scales, and from the latter by having a distinct number of supralabials. The new species also differs markedly in color pattern by having continuous pale cream color throughout the venter.

A new alligator lizard is described from the Chihuahuan Desert in southwestern Tamaulipas, Mexico. This lizard appears to be most closely related to the smooth-scaled, relatively small-bodied alligator lizards Gerrhonotus lugoi, from the Cuatro Ciénegas Basin of central Coahuila, and G. parvus, from the central part of Nuevo León, but differs from these species, especially G. parvus, in a number of morphological characters. We tentatively place our new species in the genus Gerrhonotus alongside G. lugoi and G. parvus, but concede that future research is needed to ascertain the phylogenetic placement of these smooth-scaled gerrhonotine lizards.

The genus Pseudoleptodeira is composed of two species (P. latifasciata and P. uribei) that inhabit tropical dry lowlands of western México, and the genus has undergone poor taxonomic stability. It was described for the enigmatic P. latifasciata (formerly Hypsiglena), and much later a new form P. uribei was described from the town of Chamela in Jalisco, Mexico. At the time P. uribei was described, it was questioned whether it simply represented a color morph of P. latifasciata; very few additional specimens have since been reported. Considering results of both morphological and molecular analyses from newly presented material, we revise the taxonomic status of P. uribei. Several morphological characters of P. uribei, including grooved fangs, loreal scale wider than high, immaculate ventral scales, and sublateral scale row reduction are shared with the genus Leptodeira, but not with P. latifasciata. Molecular analyses of 1429 base-pairs (bp) of mitochondrial (cyt b, nad 4, and tRNAs His Ser) and 4150 bp of nuclear (ZEB2, NTF3, FSHR, and DNAH3) sequence data independently confirm “P. uribei” as a member of the genus Leptodeira. The results of Bayesian and parsimony phylogenetic analyses place “P. uribei” sister to Leptodeira frenata. We propose the new combination Leptodeira uribei and restrict Pseudoleptodeira to P. latifasciata.