The costs of an aquatic life are likely to be strongly influenced by an animal's buoyancy, which can be measured as specific gravity (SG). The shells of chelonians are negatively buoyant, and the tendency to sink is opposed by air in the lungs. Turtles can therefore regulate buoyancy by adjusting residual lung volume, but must do so within the constraint of a relatively fixed body volume set by the rigid shell. Emydids have been reported to effect changes in lung volume with reciprocal changes in the volume of water stored in the urinary bladder and, perhaps, for rapid short-term adjustments, the cloacal bursae. We examined buoyancy control in two species, the eastern painted turtle Chrysemys picta (Emydidae), which has well-developed cloacal bursae, and the common musk turtle Sternotherus odoratus (Kinosternidae), which lacks bursae. We measured SG in captive turtles, then manipulated SG by attaching either weights or floats, and measured SG again at 4 h and 24 h after attachment. Initial SG was consistently and significantly higher in bottom-walking Sternotherus (1.03) than in more free-swimming Chrysemys (1.01). Both species compensated nearly completely for weights up to 6% of body mass by decreasing weight in water (reflecting higher lung volumes); compensation in both species was mostly complete at 4 h. Both species also compensated for attached floats (buoyant forces equivalent to up to 4% of body mass in Sternotherus and at least 7% in Chrysemys) by decreasing lung volume. Lung volume changes (gauged by underwater weight) were not matched by changes in stored water volume (gauged by body mass in air) in Sternotherus and only partially matched in Chrysemys. Changes in lung volume did not affect surfacing frequency. Small differences in buoyancy regulation between species reflect differences in natural history and, presumably, morphology, but neither the mechanisms of chronic lung-volume maintenance nor the function of cloacal bursae are clear.

Males in group-breeding salamander species sometimes deposit spermatophores on top of other spermatophores during mating. Several adaptive hypotheses have been proposed to explain this behavior: a tactic used by males, making sperm from other males unavailable to females thereby reducing the intensity of sperm competition, or that females more easily find and obtain sperm from stacked spermatophores which are elevated from the substrate. I tested the following hypotheses in the small-mouthed salamander, Ambystoma texanum: (1) males adjust spermatophore capping behavior in the presence of a competitor; (2) males stack on top of spermatophores belonging to competitors more often than expected at random; (3) females pick up sperm from stacked spermatophores relative to single spermatophores more often than expected at random; and (4) females distinguish spermatophores they obtain sperm from with respect to the identity of the depositing male. I found that males stack spermatophores more often in the presence of a competitor and that they are more likely to stack their spermatophores onto those belonging to their competitor. I found no evidence that females obtain sperm preferentially from stacked spermatophores or that females discriminate between spermatophores deposited by different males. I found males behaviorally interacted more frequently with their competitors than with females during mating trials in the lab, suggesting a mechanism males may use to preferentially stack their spermatophores on those belonging to their competitor. My results are consistent with the hypothesis that male spermatophore stacking is used to prevent sperm from rivals being available to females.

Females of some temperate-zone snake species appear to exhibit thermophilic behavior during gestation, resulting in differential habitat use between gravid and nongravid individuals. We investigated thermoregulation of 13 female cottonmouths (Agkistrodon piscivorus) near their northwestern range limit in southwestern Missouri during mid-summer. Mean preferred body temperature (23.4 C) and preferred body temperature range (T_set, 20.0–26.5 C) measured in a laboratory thermal gradient were lower than those reported for most snake species. Physical models demonstrated that T_set consistently was available to snakes during the study period, although the frequency of availability varied among habitats. The relatively high thermal quality of the environment (based on T_set availability) allowed snakes to achieve field body temperatures (T_b) closely matching laboratory preferences. Gravid females exploited the thermal environment more efficiently than nongravid females by preferentially occupying the most thermally favorable microhabitats. Accordingly, gravid females consistently maintained higher T_b than nongravid females, demonstrating a functional link between habitat use and thermoregulation. Differences in T_b between gravid and nongravid females were greatest at low ambient temperatures, highlighting their different thermoregulatory strategies. Maintenance of low T_b in nongravid females is consistent with an energy conservation strategy benefiting reproductive investment.

A relatively large amount of variation occurs in the reproductive ecology of tropical snakes, and this variation is generally regarded as being a consequence of seasonality in climate and prey availability. In some groups, even closely related species may differ in their reproductive ecology; however, in others it seems to be very conservative. Here we explore whether characters related to reproduction are phylogenetically constrained in a monophyletic group of snakes, the subfamily Dipsadinae, which ranges from Mexico to southern South America. We provide original data on reproduction for Leptodeira annulata, Imantodes cenchoa, and three species of Sibynomorphus from southern, southeastern and central Brazil, and data from literature for other species and populations of dipsadines. Follicular cycles were seasonal in Atractus reticulatus, Dipsas albifrons, Hypsiglena torquata, Leptodeira maculata, L. punctata, Sibynomorphus spp. and Sibon sanniola from areas where climate is seasonal. In contrast, extended or continuous follicular cycles were recorded in Dipsas catesbyi, D. neivai, Imantodes cenchoa, Leptodeira annulata, and Ninia maculata from areas with seasonal and aseasonal climates. Testicular cycles also varied from seasonal (in H. torquata) to continuous (in Dipsas spp., Leptodeira annulata, L. maculata, N. maculata and Sibynomorphus spp.). Most dipsadines are small (less than 500 mm SVL), and females attain sexual maturity with similar relative body size than males. Sexual dimorphism occurred in terms of SVL and tail length in most species, and clutch size tended to be small (less than five eggs). Combat behavior occurs in Imantodes cenchoa, which did not show sexual size dimorphism. Reproductive timing, for both females and males, varied among species but in general there were no differences between the tribes of Dipsadinae in most of the reproductive characteristics, such as mean body size, relative size at sexual maturity, sexual size and tail dimorphism, duration of vitellogenesis or egg-carrying in oviducts.

Interspecific competition between closely-related and ecologically similar species may limit geographic ranges and fine-scale sympatry, especially when one species is aggressive toward another species. Throughout Ohio, two closely-related salamander species, Plethodon cinereus and P. electromorphus, can be found in similar habitats. While the distributions of the two species generally overlap through much of this region, a finer-scale examination of their distributions indicates that many areas within the zone of sympatry contain only one or the other species. This geographic pattern suggests that the two species are interacting. In this study, we examined the behavioral responses of individuals from allopatric populations of both species to provide an initial understanding of their interactions. This study represents interactions between ‘novel’ biotic stimuli, as individuals from allopatry have not previously encountered members of the congeneric species. We found that allopatric populations of P. electromorphus exhibited all typical behaviors recorded in other Plethodon species and that both species from Ohio exhibited aggressive behavior. We found that when animals were tested in intraspecific trails, P. cinereus was more aggressive than P. electromorphus and that P. electromorphus was more submissive than P. cinereus. However, these two species did not differ in behavior during interspecific trials, except that P. electromorphus spent more time in escape behavior (EDGE). Therefore, we conclude that P. electromorphus likely would act submissively if encountering P. cinereus for the first time in the field. These results imply that P. electromorphus may not be able to expand its range into areas occupied by P. cinereus, and, in turn, P. cinereus may be able to successfully expand its range into areas presently occupied by P. electromorphus.

We quantified within-population variation in the seasonal abundance of free-living adult trombiculid mites and infestation of collared lizards by parasitic mite larvae at the Arcadia Lake Dam in Edmond, OK, U.S.A. Lizards on one of two habitat patches (front) harbored many more larval mites, and were more rapidly re-infested after mites were removed experimentally. Although female and male lizards and males displaying alternative social tactics had different activity rates, they harbored similar numbers of parasites, which is inconsistent with the hypothesis that the degree of ectoparasitism is positively related to host activity. Heavy mite infestation of front patch lizards was related to greater exposure to vegetation/soil surrounding this habitat patch, and perhaps more favorable physical conditions there for mite reproduction and development. The abundance of free-living adult mites on the rock substrata occupied by collared lizards was temporally dissociated from infestation of lizards by mite larvae. Free-living adult mites were abundant in May, but declined precipitously in June shortly after larvae began to appear on lizards. Larval parasites remained until lizards entered hibernacula in late summer. There was no effect of marked differences in larval mite load on any of the behavioral, and most of the life-historical variables that we measured. The exception was growth rate. First-year males grow faster than any of the other social classes in this population, and their rates were reduced on the front habitat patch suggesting a growth cost of heavy parasitism at a time when lizards exhibit maximal growth.

Escape theory predicts flight initiation distance (FID), distance between predator and prey when escape begins, for factors affecting costs of fleeing and not fleeing. Starting distance (SD), distance between predator and prey when approach begins, appears to affect FID for some species and risk levels, but not others. I predicted that in an active forager under low risk FID would appear to increase as SD increases due to (1) inclusion of SDs shorter than optimal FID and (2) spontaneous movements not motivated by escape. I predicted that FID and SD are unrelated at low risk when SDs shorter than optimal FID and spontaneous movements are excluded. When I approached the lizard Aspidoscelis exsanguis, an active forager, all predictions were confirmed. Effects of short SD and spontaneous movement might account for relationships between FID and SD in some birds and lizards. Nevertheless, as a predator approaches, costs of monitoring may increase, as may assessed risk and risk-averse errors due to shorter available assessment time. Risk-aversion might account for restriction of the relationship between FID and SD to high risk levels in an ambushing lizard species, for which spontaneous movements are far less frequent than for active foragers such as A. exsanguis. Although FID and SD are unrelated in A. exsanguis, SD and the related alert distance can provide valuable insights into risk assessment in other taxa having escape movements distinct from other movements. Present findings emphasize the importance of distinguishing between escape and other movements that may be initiated during approaches. A previously untested prediction of escape theory is that escape begins immediately when a prey detects an approaching predator closer than optimal FID, leading to the prediction of a slope of 1.0 between FID and SD. This prediction was confirmed for SDs less than 1.5 m.

The structure and composition of forest-floor anuran diversity in the biologically rich rain forests of southern Western Ghats were studied. The study was carried out in the relatively undisturbed rain-forest tract of Kalakad-Mundanthurai Tiger Reserve. A quadrat search method was used to estimate species richness and density of the forest floor anuran community. Sample locations were distributed across three distinct watersheds in the reserve. In total, we captured 509 individuals belonging to 20 species. The density of anurans was 149 individuals ha⁻¹ on the rain-forest floor, and along streams their densities exceeded 300 individuals ha⁻¹. Total diversity across all watershed locations was partitioned into within and among watershed components, corresponding to alpha and beta diversity. We found high levels of species turnover (high β diversity) among watersheds, a process that may partly explain the high species richness and large number of endemic anuran species known to occur in the rain forests of the Western Ghats. Anurans density was low and comparable to other studies conducted in South-East Asian forests. A re-examination of the reports on anuran densities revealed that Central American anuran densities were an order of magnitude higher than South Asian and South American anuran densities. Existing hypotheses do not adequately explain the differences in anuran densities in different parts of the world.

We describe a new species of anole of the Norops schiedei group from western Guatemala. A distinctive suite of characters distinguish it from the remaining species of the group (e.g., prenasal scales fused to circumnasal; most midventral scales weakly keeled; all scales in prefrontal depression strongly keeled; scales comprising supraorbital semicircles about same size as scales between semicircles; all keels on dorsal surface of head oriented nearly longitudinally; hemipenis large and bilobate).

A new species of Cyrtodactylus is described from Lore-Lindu National Park, Sulawesi Island, Indonesia. It is distinguished from all other Cyrtodactylus by a unique suite of scalation characters and a distinctive color pattern. The new species is the fourth Cyrtodactylus known from the island of Sulawesi and one of two new species found in 2004. These recent discoveries suggest that the diversity of the herpetofauna in Wallacea, a poorly studied biological “hotspot,” may be far richer than previously thought.

A new species of Uraeotyphlus (Amphibia: Gymnophiona: Uraeotyphlidae) of the malabaricus group is described from a type series of 21 specimens from the Western Ghats of southernmost Tamil Nadu, peninsular India. Three additional specimens are referred to the species. The new species differs from other species of the malabaricus group in its combination of total number of annuli, length of the tail (as measured by number of post-anal annuli), and numbers of teeth. By virtue of its sample size and precise locality data, the new species represents the best-known member of the recently described but poorly-known malabaricus-group of Uraeotyphlus. The malabaricus group likely includes additional unrecognized species, but increased sample sizes and better locality data are required to assist the interpretation of available material.

A distinctive new species of rattlesnake is described from the western versant of the Sierra Madre del Sur of Guerrero, Mexico. This long-tailed rattlesnake cannot be confused with any other species of rattlesnake and is most similar to Crotalus stejnegeri and C. lannomi. The Guerrero species possesses a strikingly distinct color pattern and differs from all other rattlesnakes in aspects of lepidosis. Mexico continues to be the origin of newly discovered species that provide important insights into the evolution or ecology of particular groups. A few examples from recent decades include Exiliboa placata, a monotypic, relictual dwarf boa (Bogert, 1968), Rhadinophanes monticola, a monotypic, highland colubrid (Myers and Campbell, 1981), and Pseudoeurycea aquatica, the only aquatic bolitoglossine salamander (Wake and Campbell, 2001).