Caudal luring is a behavior used by many ambush-foraging snakes that increases their encounter rate with prey. In this study, we used the dusky pigmy rattlesnake, Sistrurus miliarius barbouri, in a series of trials involving prey and measured the frequency and duration of caudal luring. This behavior varied ontogenetically, with adults never performing caudal luring. Juveniles that lured for longer durations were more successful in attracting prey. Males and females caudal lured in equal frequency but females took longer time periods to achieve a similar level of foraging success. Because the tails are sexually dimorphic in this species, we suggest that the longer tail of the male may be a more effective luring device. This is the first quantification of a sex difference in caudal luring, and the results suggest important differences in foraging ecology among males and females.

The largest remaining green turtle (Chelonia mydas) population in the Atlantic is potentially threatened by the resurgence of a commercial artisanal green turtle fishery in Nicaragua. Nicaragua is the site of the principal feeding ground for adults from the Tortuguero, Costa Rica, rookery. Little is known about the life history parameters of this population away from the nesting beach. To better understand the potential impact of harvesting in Nicaragua on the Tortuguero population, we estimated survival rates of adult females tagged on the nesting beach at Tortuguero, and a mixed group of large juveniles and adults tagged at turtle fishing sites in Nicaragua. Based on band recovery analysis, large juvenile and adult green turtles tagged at Nicaragua turtle fishing sites have a very low annual survival probability, 0.55. Adult females tagged on the nesting beach, which may forage at a broad range of Caribbean feeding grounds, had an annual survival probability of 0.82. These survival rate estimates are likely too low to sustain the population and have important implications for the future of the Tortuguero rookery.

Prey animals may enhance their fitness by avoiding predators, but unnecessary responses to predators that pose little threat may be maladaptive. Dietary cues from predators may be used by prey individuals to identify “dangerous” predators (i.e., those that have been feeding on conspecific prey), and consequently to minimize needless reactions to cues from innocuous animals. We tested for the presence of diet-mediated antipredator responses in a terrestrial system involving wandering garter snake predators (Thamnophis elegans) and amphibian prey (spotted frogs, Rana luteiventris; long-toed salamanders, Ambystoma macrodactylum; and Pacific tree frogs, Pseudacris regilla). Wild-caught prey were exposed to cues from predators fed heterospecific (worm) versus conspecific diets in two-sided behavioral arenas, and patterns of selection for particular sides of the arena were assessed. We found that none of the amphibian prey species responded to differences in the diet of their predator, but two species avoided cues associated with injured conspecifics. These results suggest that some amphibians lack the capacity to distinguish between “dangerous” and “safe” predators, possibly due to historically low levels of predation, or because their predators possess the ability to break down or mask cues allowing for such discrimination. However, given that our experimental protocol tested for a single metric of predation risk reduction (i.e., behavioral avoidance), further analyses will be required to determine whether diet-dependent antipredator behavior is largely absent from this predator-prey system.

Rattlesnake predatory behavior is defined by a strike and then release of rodent prey. Poststrike, the released envenomated prey dashes off and dies. Therefore, the snake must relocate the prey relying largely upon chemosensory cues emitted by the struck prey. Assessing these poststrike chemosensory cues is important to the snake as these cues may contain significant information about the effectiveness of the preceding strike and hence the likelihood that trailing the odor left by the envenomated prey will allow successful recovery of the prey. One possible cue in this scent trail is concentration of the distinctive odor generated in the prey during envenomation. To test this, we presented snakes with different poststrike choices of low and high prey-odor concentrations. We found that although rattlesnakes could trail each concentration level, they preferred the high odor concentrations. These results imply that rattlesnakes respond to concentration levels, not just to a threshold level of prey odor. This adjustment to different odor concentrations is not accomplished by varying rate of tongue flicks (RTFs). Based on this study and previous work, we propose a behavioral mechanism by which rattlesnakes assess the chemosensory quality of a poststrike prey odor trail.

Sexual dimorphism in body size is often accompanied by shape dimorphism. Shape dimorphism may be selected directly, or may be an indirect result of selection for size dimorphism. To determine whether shape differences are likely to have been directly influenced by selection, the indirect effects of size dimorphism on shape can be removed statistically, the approach of most previous studies, or, alternatively, we can examine the patterns of shape dimorphism in species that are not size dimorphic. Here I describe sexual shape dimorphism in adults and neonates of a lizard that is not dimorphic in body length, the eastern water skink (Eulamprus quoyii). In this species, snout–vent length is not significantly different between adult or neonate males and females, but there are significant shape differences between sexes in both adults and neonates. For a given body length, adult males have wider heads, longer limbs, shorter trunk length (the distance between the forelimb and the hindlimb), and greater mass than females. In addition, head width, forelimb length and mass increase significantly more rapidly with body length in adult males than in females, whereas the rate of change of hindlimb length and trunk length with length is not significantly different in males and females. The shape of the body is more similar in neonates than adults, but female neonates have significantly longer trunks than males. The intersexual shape difference in neonate E. quoyii suggests that, although growth rate differences among body parts are the main source of differences in shape between adults, the difference between male and female interlimb lengths is present initially. Shape differences present at birth that are preserved until adulthood are less common than growth differences as a source of adult shape differences. The intersexual shape differences among adult E. quoyii are similar to those reported for species that are sexually size dimorphic, suggesting that selective forces have influenced body shape in similar ways in both size dimorphic and nondimorphic species, and that allometric relationships alone may not be responsible for shape differences between males and females in size dimorphic species.

In June 2002, we studied the natural history of Ameiva ameiva and sympatric anoles, Anolis aeneus and A. richardii, in an altered habitat on Grenada to test three predictions regarding intraspecific interactions in Ameiva, intrageneric interactions between anoles, and interfamilial interactions between Ameiva and anoles. Our data generally supported our first prediction that characteristics of an insular population of A. ameiva would essentially mirror those described for other insular populations of West Indian congeners, were less supportive of our second prediction that structural habitat use and diets would indicate interspecific resource partitioning between anoles, and strongly supported our third prediction that anoles would spend less time on the ground when Ameiva were active. Based on tests that indicated that Ameiva were predators of anoles, we suggest that predator-avoidance is the most parsimonious explanation for the apparent adjustments in foraging strategy.

In streams, reach-scale physical habitat (i.e., pool, run, riffle, cascade; hereafter mesohabitat) is viewed as an important control on the distribution of organisms. However, there is limited understanding of stage-specific mesohabitat associations in species with complex life histories and of associated causes and population-level implications of these distribution patterns. In intensive field surveys, I found that larvae and adults of the stream salamander Gyrinophilus porphyriticus (Plethodontidae) displayed similar associations with pools and riffles. However, larvae were negatively associated with cascades and adults were negatively associated with runs. Adults had no effect on the survival, growth, or activity of larvae in a controlled experiment, suggesting that stage-specific negative associations were not a function of intraspecific interactions. These negative mesohabitat associations may be related to the size-distribution of interstitial spaces in cascades and runs, which were biased against larval and adult body sizes, respectively. My results indicate that incorporating reach-scale habitat structure in sampling programs is critical for accurate assessments of stream amphibian populations, and that perturbations altering reach-scale habitat structure may differentially affect life history stages of G. porphyriticus.

Salamanders of the Pseudoeurycea bellii complex are widespread in México north and west of the Isthmus of Tehuantepec. They are the largest terrestrial plethodontids and have distinctive color patterns consisting of a general black ground color with strikingly bold red-orange marks in different patterns on the dorsal surface. At present three species are recognized: P. bellii (widespread, with two subspecies), P. gigantea (restricted to a small area of eastern México), and P. naucampatepetl (known only from the vicinity of the type locality in west-central Veracruz). A phylogenetic analysis based on two mitochondrial genes (cytochrome b and 16S RNA) finds support for three main clades, one including P. gigantea and P. naucampatepetl, another including the Oaxacan samples, and a third including P. bellii. New morphological data, DNA sequences, and limited allozymic information provide evidence that the Oaxacan clade comprises two species. The name P. boneti is resurrected from synonymy and applies to northern Oaxacan populations, while a new species is described from extreme western Oaxaca at elevations lower than have been recorded elsewhere for members of the complex.

Plethodon stormi and Plethodon elongatus are two closely related species of plethodontid salamanders that are restricted to the Klamath Province of northwestern California and southwestern Oregon. Discovery of three localities south of the Klamath River, in the Scott River drainage, not assignable to either P. elongatus or P. stormi, motivated closer examination of this complex. We describe molecular (mitochondrial DNA) and morphological variation among specimens collected from the three newly discovered populations and compare these to populations of P. elongatus and P. stormi from Siskiyou County, California and Jackson and Josephine Counties, Oregon. Analyses of mitochondrial sequence data from the ATPase 6 and cytochrome b genes recovered clades corresponding to P. elongatus, P. stormi and the Scott River populations. Multivariate analyses indicate that Scott River drainage animals are morphologically distinct from P. elongatus and P. stormi. Because both genetic and morphological data indicate that the Scott River populations are distinctive, we provide a description of a new species, Plethodon asupak, to reflect the evolutionary history of this group and facilitate species management.

We describe a new species of leptodactylid frog of the genus Physalaemus from the lowlands of western Ecuador. It belongs to the P. pustulosus species group and differs from other group members in its smaller size, skin texture, tadpole characters, and advertisement call. The new species has wide variation in size and color pattern both at the intra- and inter-population levels. This variation matches that observed in P. montubio and P. randi, and render difficult its diagnosis on the basis of morphological features. A phylogenetic analysis of morphological characters shows that the new species belongs to a clade distributed west of the Andes in Ecuador and northern Peru, sister to (P. petersi P. pustulosus). A phylogeny based on mtDNA shows that P. montubio and P. randi form a clade sister to (P. coloradorum P. sp. nov.). The calls of these three species have two components with different acoustic features that arguably match the frequency sensitivity of the ear of conspecific females, in a manner similar to the complex calls of P. pustulosus. The new species occurs in two predominantly dry regions, the Lowland Deciduous Costa Forest, and the Lowland Semideciduous Costa Forest.

A new species of the Eleutherodactylus nigrovittatus Group is described from five localities, at elevations of 1800–2760 m in cloud forests in the Cordillera Oriental in central Peru (Distrito de Paucartambo, Departamento de Pasco). The new species is assigned to the Eleutherodactylus nigrovittatus Group, and differs from all described species therein by having a combination of smooth skin on the venter, undilated discs on the digits, Finger I and Finger II of variable length (slightly shorter, slightly longer or of equal length), Toe III and Toe V of variable length (slightly shorter, slightly longer or of equal length), and a snout–vent length up to 48.8 mm in females. In life, dorsum is tan with dark brown blotches, venter flesh to pale gray with small gray blotches, and posterior surfaces of thighs tan. The new species occurs sympatrically with E. lacrimosus, E. peruvianus, E. platydactylus, and Eleutheodactylus cf. rhabdolaemus. Phrynopus lucida and P. nebulanastes are changed to Eleutherodactylus based on morphological and osteological characters and are assigned to the Eleutherodactylus nigrovittatus Group.

A new species of Atractus is described from grasslands of the State of Rio Grande do Sul, southern Brazil. The new species is distinguished from all congeners by the combination of a single postocular, long loreal, six supralabials, generally six infralabials, 17 dorsal scales rows, six or seven maxillary teeth, and a dorsal color pattern in preservative uniformly grayish-brown with a creamish-white temporal region. Comparisons of the new species are made with all other Atractus species, and its affinities with A. reticulatus and allied species are suggested based on the morphology of the hemipenis.