For their survival from hatching or birth, snakes depend on their ability to eat other animals. Thus, ontogeny and reproduction occur only if eating other animals is successful. Determining the degree to which feeding is successful must be studied at a variety of levels. I briefly review past and recent studies of feeding mechanics, focusing on those clades I have observed, and outline some features of feeding that puzzle me. The questions arise partly from unusual features of snakes, but the answers, when found, might have broader potential application. The questions focus primarily on how cells and tissues perform behaviors that are extreme in either space or time. When they become available, I anticipate that the answers will reveal aspects of evolutionary processes underlying the differentiation of species-specific or clade-specific traits. In the process, I reflect on how studies of feeding have paralleled some patterns of scientific progress, and how current fads might either inhibit or promote that progress.

Chytridiomycosis is a skin infection caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), that has been responsible for amphibian declines and extinctions worldwide. Chytridiomycosis increases the permeability of amphibian skin leading to low plasma ion levels and loss of physiological homeostasis. Because temporary increases in cutaneous salt loss and water uptake occur during sloughing, potentially exacerbating the effects of Bd infection, avoiding water while sloughing might help to alleviate these effects, and could contribute to intra- and interspecific differences in pathophysiology. Furthermore, because the amount of time an infected individual spends in contact with water could affect the severity of ion loss, we questioned whether amphibian behavior is altered in response to infection with Bd. This project utilized continuous infrared video footage of captive Australian Green Tree Frogs (Litoria caerulea) as a method of behavioral analysis, to determine whether infection with Bd altered the duration of water contact, activity levels, and the location of sloughing events. We found that although frogs became less active once infected, there was no change in the duration of time spent in contact with water. Infected frogs showed a decrease in the proportion of sloughing events occurring in contact with water as the experiment progressed. Our study is novel in that it provides insight into the behavioral effects of chytridiomycosis, demonstrating that Bd infection can induce behaviors that might alter disease progression.

Nesting in sea turtles involves a series of behavioral stages in which females ascend a coastal beach, move sand to bury and conceal eggs, and return to the sea. We created a partial ethogram of nesting stages in Green Sea Turtles (Chelonia mydas) from a central Florida Atlantic beach. We documented nesting stages through both in-person data collection and use of night-vision video-recording equipment for coding behaviors at a later date. The video-recorded footage allowed precise measurement of stage durations and descriptions of action patterns without observer effects. Using these methods, we recorded nesting behavior in 14 Green Sea Turtles, from which we measured limb and body movements, described nine modal action patterns, and identified seven distinct nesting stages—ascent, body pitting, digging, egg laying, covering, camouflaging, and descent. During body pitting and camouflaging stages, we found an inverse relationship between front flipper and rear flipper stroke rates. In body pitting, front flipper stroke rate decreased from start to finish, whereas rear flipper stroke rate increased over the duration of the stage. The inverse of this stroke rate pattern occurred during the camouflaging stage. Our work adds new detail to previous descriptions of Green Sea Turtles' nesting behavior, including a distinct transition between body pitting and digging. We compared our ethogram to previous studies on Green Sea Turtles' nesting behavior and propose these descriptions as a way to inform studies that test hypotheses concerning behavioral differences that might exist among populations, within populations over time, or between groups exposed to human disturbance or varied anthropogenic factors.

The two extant clades of turtles, Pleurodira and Cryptodira, can be distinguished by the fact that the pelvic elements of pleurodire turtles are extensively sutured to both the carapace and plastron whereas the pelvic elements of cryptodire turtles are not. Pleurodire shells are also generally flatter than those of cryptodires. These distinctive features could potentially contribute to differences in the strength of the shell in these two clades, but quantitative assessments are lacking. We asked the following questions: How do the sutured pelvic elements of Pelomedusa subrufa (Pleurodira) affect the strength of the turtle's shell? Does the height of the turtle shell affect shell strength? Are there differences in the strength of the shells of pleurodires and cryptodires living in the same geographic regions? We developed finite element models of pleurodire and cryptodire shells and used them to assess the effects of various morphologies and loading regimes on shell stress. The pleurodire model without pelvic elements had higher maximum and average stresses for all load cases, and thus lower strength, than the model with pelvic elements, showing that sutured pelvic elements increase the strength of the shell. Increases in shell height increased shell strength. No differences in strength were found between pleurodire and cryptodire species living in the same geographic regions, indicating that the two clades might be evolving in response to the same selective pressures or requirements, but doing so in different ways. Overall, pleurodires and cryptodires are both able to increase the strength of their shells, but the morphological characteristics that they use to do so differ between the clades.

Sceloporus (S. aenus and S. scalaris) are oviparous sibling lizard species inhabiting high mountain zones (>2700 m) in central México. Females of these species lay their eggs in soil mounds left by burrowing gophers (Pappogeomys). Numerous abiotic factors can affect site selection and subsequent development of the lizard embryos, but little is known of the relationship between the optimal physical and chemical variables of the surrounding soil that allow development and successful hatching of the eggs, especially in high-elevation environments. We hypothesized that soil parameters and temperature drive site selections by females seeking nest locations favorable to embryonic development. We recorded differences in the abiotic parameters of soil mounds between dry and rainy seasons, irrespective of whether the mounds contained eggs. Statistical analyses revealed that an environment of high relative humidity and stable temperatures necessary for mound selection as a nesting site were associated with intermediate moisture content, high organic matter content, high values of cation exchange capacity, and relatively high porosity of the soil substrate. Collectively, these values of abiotic soil traits prevent sudden changes in temperature and humidity at the nest depth, providing conditions that promote successful development and hatching. Understanding the relative importance of these abiotic factors in nest site selection by Sceloporus should contribute to an understanding of the adaptations of oviparous reptiles that reproduce in different environments.

Metachrosis, or color change, in reptiles is used for thermoregulation, crypsis, and many other purposes. The mechanism and function of metachrosis remain unknown for many species, however, especially snakes. Anecdotal observations suggest that some snake species, including rattlesnakes, undergo varying degrees of color change when captured and confined. A possible explanation for this color change is the increase in plasma levels of the primary stress hormone, corticosterone (CORT). In this study, we implanted Southern Pacific Rattlesnakes (Crotalus helleri) with either CORT or sham silastic implants and photographed them under standardized lighting in a curtained box at the time of implant and 2 and 4 wk postimplant. We quantified light value (brightness or darkness) of the dark and light bands of the subjects' tails and examined the relationships of these variables to baseline CORT levels (CORT level at time of capture) as well as CORT levels after 1 h of acute confinement stress. CORT-treated snakes had higher baseline CORT than control snakes, but treatment had no direct effect on color. Regardless of treatment group, baseline CORT was positively correlated with lighter light bands, but had no relationship with the dark bands. Additionally, the magnitude of the CORT increase during acute stress was related to greater increase in contrast between light and dark bands. Defensive behavior was negatively correlated with contrast. We discuss potential reasons for the relationship between stress, defensive behavior, and color change.

Anthropogenic disturbances often present novel habitat features to which the members of an existing population must adapt. We examined the effects of disturbance and habitat fragmentation on the movements of Northern Pacific Rattlesnakes (Crotalus o. oreganus) from 2006 through 2012 in southern British Columbia, Canada. We radio-tracked 44 adult male rattlesnakes through shrub-steppe, grassland, and dry forest habitats that varied from highly disturbed and fragmented to near pristine with little human interaction. Sources of disturbance were primarily associated with tourism (golf course, campground, hiking trails, roads, parking lots, vineyards, condominium complex). After accounting for interyear variation and daily temperature, rattlesnakes in undisturbed areas had larger home ranges (100% minimal convex polygon) and longer home-range lengths compared to individuals frequenting minimally to highly disturbed areas. Contrary to our predictions, snakes in highly disturbed sites did not move greater total distances, display elevated movement frequencies, higher movement rates, and/or more convoluted movement patterns.

Despite large-scale population decline and geographic range contraction, Timber Rattlesnakes (Crotalus horridus) continue to occupy sites across much of eastern North America, including a diversity of habitat types. Here, our objective was to examine the influence of intrinsic and extrinsic factors on the movement and activity range of Timber Rattlesnakes in the Coastal Plain of southeastern Virginia. To do so, we analyzed the movements of 54 radio-implanted snakes over a period of 17 yr, with individuals being tracked for 1–6 yr, amounting to more than 14,000 snake locations. Consistent with previous studies, our results showed strong sexual differences in movements, with average daily and annual movements of males exceeding those of females. Mean annual movements of males were approximately 1.8 times greater than those of females, with a peak in male movements in late summer, associated with mate searching. Similarly, all estimates of activity ranges (using minimum convex polygon and kernel methods) were larger for males, with overall activity ranges approximately three times greater than for females. Gravid females had somewhat smaller movements and activity ranges than nongravid females, with early-season movements of gravid individuals to the birthing site, followed by shorter movements within that site, interpreted as serving a thermoregulatory function. The number of locations and body mass (of males) also appeared as significant factors in some models, although sex was the dominant factor in all models.