The ecological role of anuran larvae is usually defined as a primary consumer. Recent studies have shown, however, that some grazing–rasping species consume animal matter on a regular basis. We investigated zoophagy in two species of Spade-foot Toads (Pelobates cultripes and Pelobates varaldii). The larvae of both species showed no specific morphological adaptations for macrophagy but are very large and inhabit invertebrate-rich ponds under prolonged summer drought conditions. We hypothesized that both species would consume animals having high nutritional value, and that there would be no difference between the two species in terms of the animals consumed, because tadpoles are broad dietary generalists. We also hypothesized that the consumption of animals would vary during development based on the size limitations of the oral cavity. Examination of the intestinal contents of P. varaldii and P. cultripes indicated that they had consumed a wide range of invertebrates, as predicted. Differences in the composition of animals between the two species might be attributable to variability in the composition of invertebrate assemblages among ponds. We provide the first evidence of consumption by taxa within Pelobates of aquatic species of Insecta (Coleoptera, Diptera, Ephemeroptera, and Odonata), Collembola (Sminthuridae and Poduridae), large Branchiopoda (Anostraca, Notostraca, and Spinicaudata), and Gastropoda (Physidae and Planorbidae). We also found a correlation between the diversity of animals consumed and the ontogenetic variation in size in both Pelobates species. These findings support the hypothesis that grazing–rasping tadpoles have an omnivorous role in aquatic trophic webs.

Cane Toads (Rhinella marina) are introduced pests and have successfully invaded many locations. Their highly plastic reproductive activity might be one of the factors facilitating invasions. Previous studies of the reproductive cycle of this species collected toads from breeding areas, thus biasing samples to breeding individuals. To examine how toad reproductive condition changed through time, and its relationship to observed levels of breeding activity, we sampled toads from nonbreeding habitat over 2 yr, while observing breeding behavior at the nearest pond. Female and male toads were collected and dissected each month, and body mass, gonadal volume, and fat body mass were recorded. Mean gonadal volume of both female and male toads decreased over the breeding season and increased when toads were not breeding. Female reproductive condition was classified into early, middle, or late stages of egg development. The proportion of females with late-stage eggs slowly increased until the point in the breeding season when males started calling, and then decreased. The fat body mass cycle was roughly opposite to the gonadal cycle. The seasonal cycle in toad reproductive condition was correlated with rainfall, indicating that rainfall is one of the causes of variation in the timing of their reproduction. We suggest the highest capture rates of large females with fully mature eggs in traps would be obtained in the late dry to early wet seasons, up to the time when males start calling.

Habitat loss and degradation appear to be the primary drivers of amphibian declines. Given the losses of native prairie and prairie wetlands, it is essential to understand the habitat conditions that support amphibian species in remaining prairie ecosystems. In this study, we combine wetland surveys, geographic information systems (GIS), and hierarchical statistical modeling to assess anuran occupancy relationships with wetland and landscape factors. We surveyed 141 wetlands with repeated sampling for amphibian breeding activity (calling, eggs, tadpoles, metamorphs) in the Sheyenne National Grasslands—one of the largest contiguous prairies on the North American continent. Overall we observed evidence of seven amphibian species breeding in the Sheyenne National Grasslands. Species with ubiquitous distributions (Boreal Chorus Frogs) or species that occurred infrequently (Canadian Toads and Great Plains Toads) had little variance in occupancy. However, Northern Leopard Frogs, Wood Frogs, and Gray Treefrogs exhibited occupancy relationships with wetland and landscape variables. Our results establish a baseline understanding of current prairie amphibian–habitat relationships. Furthermore, they indicate that integrating local and landscape variables into occupancy models that account for spatial autocorrelation can provide a better understanding of amphibian ecology, and can inform conservation and restoration programs.

Playa La Flor in Nicaragua is one of the few remaining beaches where Olive Ridley Sea Turtles (Lepidochelys olivacea) nest in arribadas. In this study, we present data on the status of the nesting population of L. olivacea on Playa La Flor from 1998 to 2006. Furthermore, in 2004 we established six plots (6 m × 6 m) on a 400-m section of the nesting beach to measure the levels of illegal egg take, clutch hatching success, and hatchling production. The total number of turtles nesting at Playa La Flor increased from 1998 to 2006 where arribadas ranged in size from 167 to 60,816 turtle encounters. In August 2004, 45% of the clutches laid during the arribada were taken illegally from the study plots, whereas these levels were lower during the arribadas occurring from September to November. In 2004, clutch hatching success and hatchling production were higher in plots located high on the beach compared with plots that were closer to or below the high-tide line. Clutch hatching success and hatchling production were higher in the September arribada than during other arribadas within the same year. The lower hatching success and hatchling production of nests laid during later arribadas might be explained by increased nest density, and overlapping clutches in the study plots could lead to an increase in microbial load, O₂ demand, and CO₂ production. If manipulating clutches is warranted on Playa La Flor, managers should target clutches that are at the highest risk of drowning, are in areas of high nest density, and are deposited during the larger arribadas that occur later in the nesting season. The location of clutches to be moved/removed might change between years, even on the same beach.

Testudinid turtles, comprising a single family with a fairly uniform shell morphology but a wide range of body sizes, present a unique opportunity for testing hypotheses regarding the evolution of shell size, shape, and functional performance. Here, we apply geometric morphometric methods and finite element models to test two hypotheses regarding the coevolution of size, shape, and mechanical performance (shell strength). First, we predicted that larger turtles will tend to have shell shapes distinct from those of smaller turtles. Second, we predicted that the shell shapes (independent of size) of smaller turtles will be stronger than those of larger turtles to compensate for the reduction in strength that accompanies a decrease in size. We used multivariate phylogenetic comparative methods to assess the significance of the relationship between shell size and shell shape, and used finite element analysis to assess the mechanical behavior of tortoise shells. We detected a relationship between shell shape and size—the shells of larger tortoise species had larger carapaces relative to plastrons, larger vertebral and pleural scutes relative to marginal scutes, and more vertically oriented marginal scutes. We did not detect a relationship between size-independent shell strength and size, however, and the direction of the trend was the opposite of what we predicted (larger tortoises tended to possess stronger shells than smaller tortoises). This is consistent with larger tortoise species having more highly domed carapaces than smaller species. Future studies should focus on the effect that additional functional factors (such as righting ability or heat exchange), and their interactions, might have on the selective pressures that affect the evolutionary path of tortoises.

Many factors can contribute to geographic color variation, including natural selection, sexual selection, and genetic drift. In squamates, phenotypic plasticity can also play an important role in color variation because color can change during maturation, across seasons, and over short time scales in response to environmental stimuli. Here, we quantify geographic color variation and assess the contribution of physiological plasticity (rapid color change) in populations of Eastern Collared Lizards (Crotaphytus collaris). First, we quantified the dorsal coloration of four geographically distinct populations of C. collaris: two putatively melanistic populations on lava flows, and two typically colored populations from the surrounding desert. Second, we quantified the degree of physiological color change occurring in response to stress and temperature, two factors known to affect reptile coloration over short time scales. We found that populations differed in overall coloration, but that only one of the two lava-flow populations was darker than its neighboring population. Both lava-flow populations exhibited less contrast with their respective substrates than the desert populations. All populations exhibited some physiological color change, but the degree of color plasticity was narrower than the differences in color across populations. Future studies on the genetics of coloration will be necessary to understand the specific mechanisms contributing to color variation in C. collaris, but our results indicate that natural selection for background matching likely plays a role in this system.

Dietary studies are important for understanding predator–prey relationships and species interactions because they provide information on the trophic resources available to predators and their potential impact on prey populations. We relied on stomach contents of museum specimens and literature records to examine ontogenetic (size-related), sexual, seasonal, and geographic variation in the feeding habits of Sidewinders, Crotalus cerastes. Sidewinders fed primarily on lizards and slightly less frequently on mammals; birds and snakes were rarely consumed. The vast majority of C. cerastes consumed single prey items ingested head-first. Juvenile and adult female Sidewinders consumed lizards and mammals with similar frequency. We observed an ontogenetic shift in feeding patterns of adult male C. cerastes because they included more mammals in their diets, compared with juvenile males. Sidewinders are classic ambush (sit-and-wait) predators and, as predicted by theory, actively foraging lizards and mammals comprise a considerable fraction of their prey. We documented seasonal shifts in the feeding patterns of Sidewinders, with snakes consuming a greater proportion of lizards during early spring and autumn, and a greater percentage of mammals during late spring and summer. This dietary shift likely results from seasonal changes in the activity patterns of C. cerastes, because individuals can be diurnally active during early spring and autumn but are predominantly nocturnal during late spring and summer. Adult male and female Sidewinders from the Mojave and the Sonoran deserts consumed similar proportions of lizards and mammals. Our findings regarding the trophic habits of C. cerastes contribute to our understanding of the ecology of terrestrial, venomous predators.

Lifetime reproduction is a fundamental demographic variable for all vertebrate species, but rarely has been examined in snakes. In the southeastern Adirondack Mountains of New York, I used a capture–recapture method over a 36-yr period to study the lifetime reproductive biology of Crotalus horridus in a metapopulation of communal overwintering dens. These longitudinal data allowed analysis of the following parameters for many females throughout their reproductive lives: age and size at first reproduction, reproductive cycle length, duration and frequency of reproduction, body mass changes, and fecundity. Within the metapopulation, first reproduction occurred at a mean age of 9.6 yr, mean length of reproductive cycles was 4.2 yr, mean reproductive life span was 9.6 yr, and average fecundity was 7.7 offspring per litter. Nonviable offspring were observed in 20% of field litters. Although several female snakes produced multiple broods (as many as seven litters over spans as long as 32 yr), most females reproduced only once—the mean number of lifetime reproductive events was 1.7 efforts per female. During their gravid year, most females lost 2–3% of their initial mass, but gains and losses as great as 15–20% indicate feeding during gestation. Microgeographic differences were evident within the metapopulation and might be correlated with (1) resource levels that could influence growth rates, or (2) human encounters that could influence survival rates. Conserving C. horridus in its northern range depends on recognizing the importance of a suite of reproductive constraints—late age of maturity, long reproductive cycles, and low number of lifetime efforts—that clearly influence the viability and persistence of local populations.

I describe a new species of reed frog (Hyperolius: Hyperoliidae) from the island of Príncipe in the Gulf of Guinea archipelago. The new species is within the Hyperolius cinnamomeoventris species complex, which includes four described species: H. cinnamomeoventris, H. veithi, H. molleri, and H. thomensis. The new species is sexually monochromatic (males and females have green dorsal coloration) and is thus distinguished from H. cinnamomeoventris, which is sexually dichromatic, and from H. veithi, in which both males and females are tan with yellow dorsolateral lines. The new species is smaller in size than H. thomensis, and differs in coloration from H. molleri and H. thomensis by lacking a black contour along the edges of the green/yellow band of coloration that extends down the dorsal side of the thigh, by lacking red/orange coloration on the dorsal and ventral sides of the thigh, and in the mitochondrial 16s and cytochrome-b genes. Furthermore, previous work indicates that the new species is distinct from H. molleri and H. thomensis in analyses of genome-wide single-nucleotide polymorphisms. This new species is the third endemic amphibian described from this small oceanic island. The type material for the closely related H. molleri and H. thomensis was destroyed or lost; therefore, I designate neotype material for these two species to enable the description of the new species.

The Palawan Pleistocene Aggregate Island Complex, a western Philippines island group, possesses a complex geologic history and numerous endemic vertebrates. On the basis of multiple unique morphological features, bolstered by genetic data supporting divergent lineages, we describe the first Philippine endemic species of Lygosoma from Palawan and Cuyo islands. This new semifossorial species is phenotypically similar to Lygosoma quadrupes, a widespread Southeast Asian scincid lizard. We recognize the Palawan lineage as a new species, the second member of the L. quadrupes species complex, and comment on its ecology and conservation status. This new species increases species-level diversity in the genus to 31, including 19 species distributed across Southeast Asia.