The majority of studies of amphibian sociobiology focuses on breeding individuals. However, adults certainly interact when not breeding and may do so subtly and in natural habitats that are inaccessible to direct observation. We conducted three laboratory experiments to explore social interactions among non-breeding, adult long-toed salamanders (Ambystoma macrodactylum columbianum), which reside in terrestrial burrows in nature. In substrate discrimination tests, salamanders preferred areas that bore chemical cues indicative of occupancy by a conspecific relative to clean areas (Experiment 1). However, only females discriminated occupant sex, preferring to associate with chemical cues derived from males (Experiment 2). When provided with a partner, salamanders spent more time in cohabitation in an artificial burrow than residing alone (Experiment 3). Our data suggest that, in nature, non-breeding adults may be social rather than territorial; conspecifics may aggregate rather than exclude one another. However, males and females may experience different kinds of benefits and costs to sociality outside of the breeding season, perhaps as a function of sex differences in energetic requirements for future reproduction.

Gestation length varies among populations of common geckos on the South Island of New Zealand, from annual reproductive cycles at a relatively warm site at Alexandra to biennial cycles at a cool site at Macraes. We compared the effect of warm and cool thermal regimes on the length and success of gestation between geckos from Macraes and Alexandra. To assess the likelihood of geckos experiencing these temperatures in the wild, we compared the laboratory thermal regimes with data available for field microhabitat temperatures, body temperatures (T_b), and selected temperatures (T_sel) of pregnant females. Temperature had a profound effect on the length and success of pregnancy; geckos from both populations under the cool regime had longer pregnancies that were less successful in producing developed neonates than geckos under the warm regime. Though no viable young were produced under the cool regime, there were qualitative differences in outcome of pregnancies between populations; all geckos from Alexandra (warm site) aborted pregnancies early on, whereas several from Macraes (cool site) produced fully developed embryos after extremely long gestation periods (up to 440 days). Under the warm regime, populations appeared to differ in the rate of embryogenesis and in neonatal growth rate (both in g/day, with individuals from the Macraes population having the highest rates). Though temperatures of both thermal regimes overlapped with common microhabitat temperatures for both populations in most seasons of embryogenesis, maximum field T_b and T_sel for pregnant females were generally higher than in the laboratory regimes, at least for certain times of day in warm weather. The prolonged embryogenesis exhibited by geckos under the warm regime and the poor success of pregnancy under the cool regime demonstrate the necessity of thermoregulation by pregnant females for successful reproduction, particularly at Macraes. Our study describes complex but significant plasticity in the thermal sensitivity of female reproduction in a viviparous gekkonid lizard.

Many amphibian populations have declined and others are at risk. Developmental stability analysis (DSA) has been proposed as an “early warning system” because it may detect environmental or genetic stress before they lead to population declines. Deviations from perfect symmetry (fluctuating asymmetry or FA) may indicate stress. We experimentally evaluated the efficacy of DSA to detect sublethal acid stress in the salamander Ambystoma maculatum. Our results indicate that traditional fitness correlates, such as size at metamorphosis, were affected by pH stress and revealed pond-specific responses to pH treatments. Fluctuating asymmetry was not correlated with pH stress, suggesting that pH stress did not disrupt aspects of the developmental program that enforce symmetry. Furthermore, FA was altered through preservation, changed through time, and differed in fore and hind limbs. Conclusions about developmental stability depended on whether traits were analyzed separately or with a composite index. Finally, we found that measurement error frequently differed among treatments, such as among pH treatments and between live and preserved groups. In such cases, measurement error must be partitioned out of each FA mean square term in order to make valid comparisons. Any amphibian monitoring program should incorporate a variety of techniques appropriate to the species being investigated and should consider including measures of traditional fitness correlates, which may provide more sensitive indicators of changing levels of environmental stress than does DSA.

Larval anurans are known for having diverse diets, but there have been relatively few studies examining their assimilation of natural foods or how they cope with variation in available resources. In our study, we estimated assimilation of food resources of two species of larval anurans that were presented with benthic substrates from a set of natural ponds. Assimilation was measured during a week-long experiment during which we renewed substrates and collected feces daily. Larvae of wood frogs (Rana sylvatica) and spring peepers (Pseudacris crucifer) were given benthic substrates from ponds shaded by deciduous forest vegetation as well as from unshaded ponds. We measured organic content in the foregut of tadpoles and from their feces. Estimates of assimilation efficiency were lower than those reported for tadpoles consuming artificial food. Both species experienced reduced assimilation efficiency on closed canopy food resources, but did not differ in their abilities to assimilate organic matter from either type of food resource. However, wood frogs processed more food during the experiment. Our results suggest that natural variation in composition of food resources among ponds could have important effects on tadpole performance and provide some support for interspecific differences in food utilization consistent with relative patterns of performance and distribution.

We describe the prey, seasonal patterns of feeding, and coelomic fat mass storage in a tropical population of the diamondback watersnake (Nerodia rhombifer werleri) and relate these data to the reproductive cycle of the studied population. Snakes were collected on the Papaloapan River, nearby lagoons, and as road kill near Tlacotalpan, Veracruz, Mexico in 1987. Diet and feeding frequency were determined by stomach content analysis of preserved snakes. The diet consisted primarily of fish (seven identified species belonging to six families). Of the adults examined, 21% of the 95 males and 32.5% of the 77 females contained food. In all age and sex classes of snakes, the feeding frequency did not differ between the wet and dry seasons. For adult males and adult females, coelomic fat mass was higher in February, March, and April than in other months. The variation in mass of the fat bodies was greater in adult females than in adult males. In females, low fat reserves may account for the low frequency of reproduction and the small litter sizes found in our studied population. In males, low fat reserves are correlated with decreased size of the diameter of the seminiferous tubules and the sexual segment of the kidney.

Terrestrial, and especially arboreal, snakes can generally span a greater distance than aquatic snakes, which have a relatively short saccular lung. Thus, we hypothesize that the saccular lung provides structural support when snakes form a cantilever. Without subsequent study, the saccular lung has long been proposed as a support for a snake's body, especially to help span gaps. To test this hypothesis, we determined whether the pressure in the saccular lung was significantly elevated when the snake was spanning a gap. Further, we reduced pressure in the lung to zero to determine whether this manipulation reduced the cantilever ability of the snake.

The pressure in the saccular lung increased significantly as a snake neared its maximal cantilever distance. However, when we prevented the pressure in the saccular lung from rising above atmospheric pressure, the snake's maximal cantilever distance was not affected. Therefore, the pressure increase in the saccular lung as the snake approached its maximal spanning distance was probably caused by the contraction of skeletal muscles needed to support the body. We conclude that the saccular lung does not help snakes span gaps. We discuss whether the saccular lung helps support the body or maintain posterior body form.

Fossils of a spectacularly large (ca. 500 mm SVL) iguanid lizard were found in late Quaternary sediments on Fiji's main island Viti Levu. The lizard is distinct from the living Fiji iguanas, Brachylophus, by the presence of a parietal foramen located in the frontal bone, an anterior inferior alveolar foramen in the splenial, the possession of autotomic fracture planes in the caudal vertebrae, and much larger size. Like Brachylophus, this lizard appears to be basal among Iguanidae, but its relationship is unresolvable with the evidence available. This giant iguana probably became extinct in Fiji soon after the first human colonization about 3000 yr ago.

We describe a new species of Cnemidophorus from a Cerrado enclave in southwestern Amazonia, Rondônia state, Brazil. This species is apparently endemic to Cerrado enclaves in the vicinity of the city of Vilhena, a region under intensive anthropic pressure due to the expansion of soybean plantations. A discriminant analysis indicated that femoral pores and scales around the tail are the best discriminators among Brazilian species of Cnemidophorus. A naïve Bayesian network constructed with categorical (mostly coloration) variables indicated that the new species had high conditional probabilities of dorsolateral fields absent, vertebral field spotted, and paravertebral lines absent. The analyses revealed clear distinctions between species of Cnemidophorus that range north and south of the the Amazon River. The new species may have evolved as a result of vicariance, following the isolation of peripheral enclaves of Cerrado in southwestern Amazonia after the late Pleniglacial. The restricted range in small areas, under extreme human pressure around Vilhena, makes this species one of the most critically endangered elements of the Brazilian herpetofauna.