We evaluated morphometric variation and reproductive effort in Trachemys callirostris callirostris females from nine populations in the Mompos Depression of northern Colombia. Two hypotheses were evaluated: (1) phenotypes of nesting females co-vary according to geographic distances among sites and/or specific environmental conditions at each site, and (2) female body size influences their reproductive potential and offspring characteristics. Populations were shown to differ in both mean female body size and body shape, with differences more related to local habitat characteristics than to geographic distances among sites. Larger females occurred in sites with higher annual precipitation and lower hunting pressure. Female size was highly correlated with clutch size and mass. Although habitat characteristics affected female size, habitat alone was not a predictor of reproductive potential. Specific habitat conditions and hunting both influence female phenotypes in this region and thereby also influence key demographic parameters, which have clear conservation implications for this highly exploited species.

Species of pond-breeding salamanders in the Great Lakes region often coexist with unisexual (all-female) populations that compete with larvae and are sexual parasites on adult males. We evaluated the effects of interactions with the larvae from unisexual salamander (Ambystoma laterale-complex) populations on blue-spotted (A. laterale) and small-mouthed salamander (A. texanum) larvae. We coupled observations in natural ponds with mesocosm and laboratory approaches to investigate the roles of competition, predation, microhabitat partitioning, and behavior on the coexistence of these populations. Unisexual salamander larvae increased mortality, reduced growth, and were observed to attack and bite small-mouthed and blue-spotted salamander larvae in mesocosms. Unisexual larvae were competitively superior to blue-spotted salamander larvae, but competitively equal to small-mouthed salamander larvae. Laboratory experiments confirmed field observations that both species increased their use of refuges in the presence of unisexual larvae and that this behavior resulted in niche partitioning. Blue-spotted salamander larvae were less active in the presence of unisexuals; however, small-mouthed larvae increased activity and use of refuges in the presence of larger intraguild predators. The hypothesis that microhabitat partitioning and altered activities minimize the effects of competition and predation was supported.

Several aspects of escape behavior are predictable by escape theory based on expected costs due to predation risk and escaping. Although the function of pursuit-deterrent signaling is to dissuade predators from attack, relatively little is known about relationships between specific components of escape and the signaling behavior. I studied effects of the risk factor distance from refuge on flight initiation distance, distance fled, probability of entering refuge, and the distance between predator (an approaching human) and prey when pursuit-deterrent display begins (display distance) in the Cuban curly-tailed lizard (Leiocephalus carinatus). I also investigated whether starting distance (distance between predator and prey when approach begins) affects escape behaviors. As predicted by escape theory, flight initiation distance and distance fled were greater and refuge entry was less probable at greater distance from refuge, indicating that qualitative predictions of escape theory apply to pursuit deterrent signalers. Starting distance did not affect escape behaviors, presumably because it did not affect perceived risk, but might do so at a faster approach speed. Display distance and flight initiation distance were identical in the data set analyzed, but individuals sometimes perform tail displays prior to fleeing. Interspecific variation in the timing of pursuit-deterrent displays is discussed, as are possible reasons for observed differences in the effect of starting distance.

It has long been accepted that amphibians can skip breeding in any given year, and environmental conditions act as a cue for breeding. In this paper, we quantify temporary emigration or nonbreeding probability for mole and spotted salamanders (Ambystoma talpoideum and A. maculatum). We estimated that 70% of mole salamanders may skip breeding during an average rainfall year and 90% may skip during a drought year. Spotted salamanders may be more likely to breed, with only 17% avoiding the breeding pond during an average rainfall year. We illustrate how superpopulations can be estimated using temporary emigration probability estimates. The superpopulation is the total number of salamanders associated with a given breeding pond. Although most salamanders stay within a certain distance of a breeding pond for the majority of their life spans, it is difficult to determine true overall population sizes for a given site if animals are only captured during a brief time frame each year with some animals unavailable for capture at any time during a given year.

We examined the terrestrial-nonbreeding ecology of a migratory salamander Salamandrella keyserlingii (Hynobiidae) inhabiting wetlands, using a large grid of 160 pitfall traps without drift fences near a breeding fen, during the April–May breeding and June–October nonbreeding seasons (1995–1997). Activity of salamanders near the fen was heaviest during September over three consecutive years, providing evidence for fall immigrations toward terrestrial hibernacula, unrelated to mating. The number of September immigrants was positively correlated with precipitation on the preceding day. More than 90% of all breeding immigrations (172/189, 1996–1997) occurred with air temperature at 0000 h ≥ 2 C. The number of breeding immigrants was positively correlated with air temperature at 0000 h or 0400 h on the same day and precipitation on the preceding day. Males began their breeding immigration earlier than females in 1997, but simultaneous movements of male and female immigrants occurred in 1996. Larger males emerged earlier from hibernation in 1996, but emergence was size-independent in 1997. Breeding immigrants chose a directional heading toward the fen. Within each sex or age class, there was no difference in body size between individuals associated with two riparian vegetation regions, forest and marsh. Whereas males and juveniles preferred a wet marsh area compared to a dry forest habitat, females did not exhibit a habitat preference except that females emigrated farther from the fen than males. Sex ratios during the terrestrial phase varied with a female-biased ratio of 1.28 through a male-biased ratio of 4.61.

Previous research suggests that female red-backed salamanders (Plethodon cinereus) in Virginia court biennially whereas males court annually. Therefore, males may face a choice to court either gravid or nongravid females. Because gravid females represent an immediate insemination opportunity (whereas nongravid females do not), male red-backed salamanders may be under selection to be able to distinguish the reproductive status of conspecific females. We conducted an experiment to determine if males could discriminate between gravid and nongravid conspecific females through volatile chemical signals. Focal males were allowed to establish territories in testing arenas for 5 d and then were exposed to three treatments in a randomized order: volatile chemical signals from gravid females, nongravid females, and a control (blank filter paper). Randomization tests revealed that focal males exhibited significantly more aggressive behavior when they were exposed to volatile chemical signals from nongravid females than when they were exposed to those from gravid females and the control. We infer that male red-backed salamanders can determine the reproductive status of conspecific females through volatile chemical signals, which may influence their social associations.

Animal life history strategies evolve in response to a range of selective pressures, and often are tightly linked to sensory cues. Squamate reptiles possess well-developed chemosensory systems, which evolved early in their history and remain highly conserved. However, chemosensory abilities are secondarily reduced in primarily visual agamid and chameleonid lizards, which casts doubt on the ubiquity of reliance on chemosensory cues among squamates. Diurnal geckos from New Zealand avoid predators using visual crypsis and are primarily ambush foragers; reliance on visual cues may be a product of strong avian predation pressure and minimal influence from mammals and snakes for the past 80 my. We used New Zealand's diurnal geckos to test the role of local adaptation versus evolutionary conservatism in defining chemosensory systems. Specifically, we tested whether Marlborough green geckos, Naultinus manukanus, use chemoreception to detect and behaviorally respond to (1) food, (2) opposite-sex conspecifics, and (3) native reptilian predators (tuatara, Sphenodon punctatus). Chemosensory cues mediated gecko interactions with all three stimuli tested: (1) the scent of fruit induced greater exploratory behavior, (2) male geckos responded to scent of female conspecifics by increasing lingual sampling and activity, and (3) tuatara fecal cues (but not skin secretions) elicited characteristic antipredator freeze behavior in geckos. Neither the primarily visual life history strategies nor the reduced range of predators of New Zealand's diurnal geckos appears to have reduced their chemosensory abilities relative to other noniguanid squamate reptiles. Instead, our findings support the notion that chemosensory traits remain highly conserved.

Predators use characteristics such as pattern and shape in forming search images of prey, thereby influencing the evolution of prey morphology. In lizards, sit-and-wait foraging species are thought to have body shapes that enhance their ability to remain cryptic to predators. Structurally complex habitats provide more opportunities for prey to avoid detection, thus predator foraging efficiency is predicted to be higher in structurally simple habitats. I used clay lizard models to test whether predation varies among lizards with different body shapes and whether predation varies among habitats in the Brazilian Cerrado with different structural characteristics. Predator attack frequency was highest in the most structurally complex habitat, but the probability of being attacked was higher in more open microhabitats. Attack frequencies did not significantly differ among the four lizard model shapes. Lizards and birds were the main attackers of models and attacks were primarily directed toward the models' heads. My results demonstrate that predator-prey interactions are largely influenced by the environmental context and scale, and that body shape alone does not efficiently promote crypsis.

A new arboreal species of Rhinella is described from the humid montane forest of Manu National Park in the Cordillera Oriental of southern Peru. The new species can be distinguished from all known Rhinella by a unique combination of external and osteological characters as well as by molecular data. The new toad is compared to R. arborescandens and R. veraguensis with respect to external characters. On the basis of morphological and molecular data, the new taxon is closely related to R. chavin, R. nesiotes, and R. festae. Although DNA data indicate that a member of the R. veraguensis group (R. nesiotes) is its sister taxon, the new species is not closely related to other members of this species group (e.g., R. veraguensis). In addition, DNA data indicate that the R. veraguensis group as it currently is defined is paraphyletic. Until additional studies are completed on the phylogeny of these South American toads, we refrain from assigning the new taxon to a species group.

Se describe una nueva especie arborícola del género Rhinella de los bosques montanos húmedos del Parque Nacional del Manu en la Cordillera Oriental del sur del Perú. La nueva especie se distingue del resto de las especies del género Rhinella por una combinación de características externas y osteológicas así como por datos moleculares. Esta nueva especie se compara con R. arborescandens y R. veraguensis respecto a las características morfológicas externas y osteológicas.

A new species of Sibon in the S. annulatus species group is described from the Mosquitia region of northeastern Honduras. The new species differs from all other members in the group in ventral and dorsal coloration. Within this group, the new species appears to be most closely related to S. dimidiatus and S. miskitus.

We describe a new species of Anolis from a high elevation locality in Department of San Martin, Peru. A single hatchling from this population was described by Ernest Williams and Russel Mittermeier and referred to Phenacosaurus ( =  Anolis) orcesi in 1991. Our recent collections document consistent differences between this population and A. orcesi, including a larger female dewlap and greater number of loreal scales in the new species. The new species may exist in a narrow altitudinal range along the eastern Andean slope of Northern Peru.

We analyzed variation among Hylodes with nuptial tubercles using morphometrics, vocalization, and external morphology. We identified three species: Hylodes phyllodes from the Serra do Mar, State of São Paulo, and southern portion of the State of Rio de Janeiro; a new species from Ilha Grande, municipality of Angra dos Reis; and a new species from the Serra dos Órgãos, municipality of Guapimirim. The new species are both from the state of Rio de Janeiro, southeastern Brazil.

A new species of aquatic snake in the genus Pseudoeryx is described from the Lake Maracaibo Basin in northwestern Venezuela. The new species differs from P. plicatilis, the only other species in the genus, by having a nuchal band, a distinctive ventral coloration, the relative size of the genial plates and having different maxillary dentition. This discovery further supports paleogeographic reconstructions of the course of a proto-Orinoco/Amazon river.