Snakes are a remarkably diverse and successful group today, but their evolutionary origins are obscure. The discovery of snakes with two legs has shed light on the transition from lizards to snakes, but no snake has been described with four limbs, and the ecology of early snakes is poorly known. We describe a four-limbed snake from the Early Cretaceous (Aptian) Crato Formation of Brazil. The sn...

Animals moving through arboreal habitats face several functional challenges, including fitting onto and moving on cylindrical branches with variable diameters and inclines. In contrast to lizards and primates, the arboreal locomotion of snakes is poorly understood, despite numerous snake species being arboreal. We quantified the kinematics and performance of corn snakes (Elaphe guttata) moving ...

The Flint Hills region of Kansas and Oklahoma encompasses the largest, contiguous tallgrass prairie in North America and is an important conservation area for many tallgrass-prairie species. We conducted a radiotelemetry study with the use of temperature-sensitive transmitters to characterize the spatial ecology of two species of snakes within a portion of this contiguous grassland. We monitore...

BACKGROUND Humans in various cultures have feared snakes, provoking an aversion and persecution that hinders conservation efforts for these reptiles. Such fact suggests that conservation strategies for snakes should consider the interactions and perceptions of the local population towards these animals. The aim of this study was to investigate students' perception of snakes and if attitudes and...

Three experiments explored the issue of selective associations in the observational conditioning of fear. Experiment 1 results indicated that observer rhesus monkeys acquired a fear of snakes through watching videotapes of model monkeys behaving fearfully with snakes. In Experiment 2, observers watched edited videotapes that showed models reacting either fearfully to toy snakes and nonfearfully...

We present a new software package for interactive segmentation of 3D images by geodesic snakes, with manual editing. Several variants of level set snakes are incorporated, including both gradientmagnitude based snakes as well as region-competition snakes. A complete segmentation pipeline, including image preprocessing, bubble initialization and parameter control, is provided in an intuitive use...

Sexual selection and mating systems profoundly influence the behavior and psychology of animals. Using their own studies of green anacondas (Eunectes murinus) and reviewing other recent studies, the authors conclude that incomplete data derived from a few well-studied snake species have led to general acceptance of polygyny as the dominant mating system in snakes. New data on behavior, paternit...

The infrared (IR) receptors in the pit organ of crotaline snakes are very sensitive to temperature. The sensitivity to IR radiation is much greater in crotaline snakes than in boid snakes because they have a thermosensitive membrane suspended in a pair of pits that comprise the pit organ. The vasculature of the pit membrane, which is located near IR-sensitive terminal nerve masses, the IR recep...

Trace element concentrations in banded water snakes, Nerodia fasciata, and representative prey items from a site polluted by coal combustion wastes were compared with concentrations in conspecifics from a nearby reference site. Water snakes accumulated high concentrations of trace elements, especially arsenic (As) and selenium (Se), in the polluted habitat. In addition to being exposed to conta...

Regional control of blood flow is often suggested as a mechanism for fine thermoregulatory adjustments in snakes. However, the flow of blood to different body regions at various temperatures has never been visualized to confirm this mechanism. We used (99m)technetium-labelled macroaggregated albumin ((99m)Tc-MAA), a radioactive tracer, to follow the flow of blood through the bodies of garter sn...