Each year, as the warmth of summer turns into the cool of autumn and the cold of winter, snakes disappear from the Canadian landscape. For several months of the year, winter weather at high latitudes is much too cold for snakes to be active in the open and they must seek subterranean shelter to hibernate. This long period underground is one during which these animals are subject not only to the possibility of mortality, but also to lost opportunity for activities such as foraging and the acquisition of resources for reproduction. Winter is thus a major constraint on the life histories of temperate-zone snakes. Short, cool summers further restrict their foraging and reproductive opportunities. In apparent response to this challenge, most high-latitude snake species are viviparous, counter to what is seen in warmer climes. Viviparity allows gravid females to “manipulate” the developmental temperature of their progeny, via behavioral thermoregulation, until those offspring are independent, an option not open to oviparous species. However, viviparity also has costs, not least of which is a pronounced reduction in feeding during pregnancy, which means that the post-partum female has only a short time before winter to make up the reserves (“capital”) that she spent on reproduction and will need for future reproduction; therefore, reproduction in consecutive years is not always possible. Evidently, the demographic costs of viviparity are outweighed by its advantages, but what remains unexplained is how some oviparous species manage to persist at high latitudes. Demographic advantages of oviparous over viviparous species, due to shorter “pregnancy” of the former, are not apparent from limited temperate-zone studies. More likely, cool-climate oviparous species also reproduce successfully by taking advantage of the thermal heterogeneity of the environment, especially by thermoregulating precisely while gravid and/or by careful selection of nest sites.

Habitat destruction and alteration is a major cause of population declines; thus, habitat restoration is essential for preventing species extinctions. Habitat restoration, however, may be hindered by an inadequate understanding of species' habitat requirements. Habitat structure may play a major role in influencing the biotic interactions among species. Pond-breeding amphibians are one group that has experienced loss and alteration of critical habitats. Vegetation structure in wetland environments may be important to amphibian larvae if its presence mediates biotic interactions, such as competition, which can affect growth and survival to metamorphosis. Despite the potential importance of habitat structure and competition, few studies have examined these factors simultaneously. In a full-factorial pond mesocosm experiment, we tested for the effects of variation in habitat structure and density of a larger tadpole competitor (Rana pipiens, northern leopard frog) on development and survival of three species of larval amphibians: Bufo americanus (American toad), Hyla versicolor (gray treefrog), and Ambystoma maculatum (spotted salamander). Survival of Bufo was greater in mesocosms with live or artificial cattails than in those lacking vegetation. Although responses varied among species, our data suggest that time to metamorphosis, survival, and species evenness can be influenced by both aquatic habitat structure and competition, whereas size at metamorphosis is affected primarily by competition. Our study is the first to demonstrate that vegetation structure alone can affect the expression of metamorphic traits for some anuran species.

I used paint to manipulate the coloration of first-year collared lizard males in the field to test whether conspicuous coloration increases risk of predation and/or aggression from dominant same-sex conspecifics, or resulted in decreased activity as a consequence of either or both increased attention from predators or socially dominant conspecifics. First-year collared lizard males are a good system for this study because their coloration is less developed than that of older males, they may suffer significant predation pressure, and instead of defending territories, they use stealthy tactics to avoid aggression from older socially-dominant males. To test these potential costs, I enhanced the coloration of first-year males in a conspicuous group by painting them similar to older territorial males, used brown paint similar to that of conspecific females to alter coloration in an inconspicuous group, and painted a control group with water. I then recorded census and focal observation data on these males for 40 d to examine survivorship, receipt of aggression by dominant males, and two indices of their activity; the number of censuses when first-year males were emergent, and their rates of travel. Both rates of predation and the frequency of aggressive acts received from territorial males were low overall and did not differ among the three treatment groups. Moreover, males in the three treatment groups did not differ in either the number of censuses when they were sighted or their rates of travel. These results are not consistent with the hypothesis that conspicuous coloration increases risk of predator attack or aggression from dominant conspecific males, suggesting that other costs may explain the observation that conspicuous coloration develops gradually in first-year collared lizard males.

Chicken turtles (Deirochelys reticularia) were studied at Dry Bay, a Carolina bay wetland in South Carolina, USA, between 1994 and 2005. A total of 461 individual turtles was marked from 1993–1998. Minimum ages at maturity for males and females were 2 and 5 yr, respectively. All females reproduced each year, and 60% of reproductive females produced two clutches per season. Clutch size averaged 9.8 eggs, and both clutch and egg size increased with body size. Hatchlings averaged 29.2 mm PL, and body sizes were similar among years. Yearling survivorship varied from 7.0–43.0% (mean = 20.4%) among years. The highest survivorship of a hatchling cohort to age 5 was 0.21. Survivorships of juveniles and adults while in terrestrial refugia were higher than survivorships while in aquatic habitats. No adult females survived a 2-yr drought (2001–2003), and the bay was repopulated by mature males and juvenile females (most from the 1998 hatchling cohort) that had survived the extended drought in terrestrial refugia. Three of those juvenile females matured and produced eggs in 2004. The traits of early maturity, high susceptibility to predation, and shortened longevity characteristic of chicken turtles are consistent with predictions for species that live in seasonally fluctuating and highly unpredictable aquatic habitats.

Signaling plays a critical role in social behavior, particularly in polygynous systems where males compete with rival males and use signals to attract mates. We quantified visual signals and social behavior in two previously unstudied species of chameleons in Madagascar, Furcifer labordi and F. verrucosus. Females of both species displayed distinct color patterns that signaled either nonreceptivity or potential sexual receptivity. Nonreceptive females rejected all male courtship. Potentially receptive F. verrucosus females mainly allowed males to attempt copulation, whereas potentially receptive F. labordi females were selective. We found that the fleshy, paddle-like rostral appendage in F. labordi was used only during courtship, whereas other studies showed that hard, keratinized appendages were used for male combat. During male-male contests, F. labordi had much more physically intense encounters, possibly to assess opponent quality more accurately since adult male F. labordi were significantly more size-matched than adult male F. verrucosus. Our study elucidated the role of social signals in these species, illustrated the atypical social behavior of chameleons compared to other lizards, and provided testable hypotheses to further delineate sexual selection in this understudied group. Sexual selection, especially intersexual selection, appears more likely in F. labordi than in F. verrucosus.

Sexual size dimorphism (SSD) is widespread in a variety of vertebrate taxa, and its presence has been associated with a range of evolutionary and ecological factors. Turtles, as a lineage, have been shown to include species that exhibit both forms of SSD—male-biased (male larger) and female-biased (female larger)—as well as species that do not exhibit SSD (male size ≅ female size). Previous work has suggested that factors affecting the direction and magnitude of SSD in turtles may include habitat preference and fecundity; these correlations, however, have not been tested in a phylogenetic context. To provide a framework for evaluating potential correlates with the magnitude and direction of SSD in turtles, we examined the phylogenetic distribution of SSD in this clade. Published sources were surveyed for data on the direction and magnitude of SSD, carapace length, clutch size, egg size, and preferred habitat (terrestrial vs. nonterrestrial). Phylogenies were compiled from multiple published sources to develop a phylogeny for all taxa (n = 82) for which SSD data were assembled. The phylogenetic distribution of SSD was then evaluated using parsimony-based methods. These analyses indicated that the ancestral condition for extant turtles was female-biased SSD. Phylogenetic analyses conducted on subsets of the data (concentrated-changes tests, independent contrasts) indicated that changes in SSD state were not correlated with changes in habitat preference. Both male and female carapace length were found to be correlated with traits related to fecundity (egg size, clutch size), but the degree of dimorphism was not found to be correlated with these traits. A significant negative correlation between egg size and clutch size was also evident in turtles, as predicted by life-history theory.

Despite the high species richness of the family Chelidae (side-necked turtles) in South America, few demographic studies are available for a neotropical chelid turtle. Here we report data from a long-term (1993–2006) study of Hydromedusa maximiliani. Population size was estimated for two periods (1993–1994 and 2003–2006) by the Jolly-Seber capture-mark-recapture method and the demographic parameters were estimated by Cormack-Jolly-Seber model. The population size estimates showed values that increased over the study period (from 235 to 318 individuals in a 250 ha area), although this result must be viewed with caution despite the large confidence intervals of the estimates. Significantly fewer individuals of intermediate body sizes (80–100 mm plastron length) were present in the 1993–1994 period compared to the 2003–2006 period. The population was female biased with male:female ratio of 1∶2. Survival rate (ϕ) was considerably higher for adult females than for males. The estimated annual population growth rate (λ) was 1.012, and the estimated temporal process variance, the variation in the population growth rate, was practically null. These demographic parameters indicate a healthy population, probably reflecting the protected status of the study area.

A new species of forest frog of the genus Platymantis is described from an elevation of 140 m in the Taft Forest Reserve in eastern Samar Island, Philippines. It is assigned to the Platymantis guentheri Species Group, a group of primarily arboreal species, and is distinguished from these and other congeners by features of its external morphology and its preferred terrestrial, limestone microhabitat. Several striking morphological characters include a large body (34.2–39.1 mm SVL for 9 males and 44.3–49.8 mm SVL for 9 females), greatly expanded finger and toe discs, large eyes, spotted flanks, and sparsely-distributed, salmon-colored dorsal dermal tubercles. The new species represents the second largest Philippine Platymantis, the third terrestrial species in the P. guentheri Group, and the only known species of Platymantis from the Mindanao Faunal Region with a preference for forested, karst habitats.

A new species of fanged frog (genus Limnonectes) is described from Davao Del Norte Province, eastern Mindanao Island, Philippines. The new species can be diagnosed on the basis of external morphology, with notable diagnostic features being its moderately large size (79.6 and 84.3 mm SVL for two males and 69.3 mm SVL for the single available female specimen), the possession of white-tipped dorsal asperities, arrangement of asperities into distinct circular clusters throughout the skin of the dorsum, a completely visible tympanum, fully webbed feet, and moderately large odontoid processes of the lower jaw. Discovery of the new species emphasizes the degree to which the biodiversity of the Mindanao Faunal Region currently is misunderstood.