Observations on the Winter Activities of Desert Reptiles

There was an error published in J. Exp. Biol. 218,[440][441][442][443][444][445][446][447][448][449][450] In Fig. 5 of this paper, there was a mistake in the theoretical calculation of the average slip angle, b s . The corrected calculations show that b s rises more sharply for low mean relative curvatures and approaches 90 deg. This change does not affect the conclusions set forth in the original paper, and shows better agreement with the experimental findings.The corrected figure is reproduced below:The authors apologise for any inconvenience this may have caused. b s ) with changing mean relative curvature (kl s ), average number of undulations along the body ( j), body length to width ratio (L/w) and effective friction. Force relationships were established from empirical drag data in loosely packed (LP) media. The color of the curves and experimental data correspond to different j (where dark blue is j=0, dark red is j=5). Solid curves are predictions for an undulatory swimmer with a L/w=7.1 and body-particle friction, m s , of 0.17. The dotted-dashed curves show the theoretical predictions with L/w=33.5 and m s =0.17. The dashed curves are the predictions for L/w=33.5 and half the tangential force (which occurs when there is a 50% decrease in body-particle friction, i.e. ABSTRACT Squamates classified as 'subarenaceous' possess the ability to move long distances within dry sand; body elongation among sand and soil burrowers has been hypothesized to enhance subsurface performance. Using X-ray imaging, we performed the first kinematic investigation of the subsurface locomotion of the long, slender shovel-nosed snake (Chionactis occipitalis) and compared its biomechanics with those of the shorter, limbed sandfish lizard (Scincus scincus). The sandfish was previously shown to maximize swimming speed and minimize the mechanical cost of transport during burial. Our measurements revealed that the snake also swims through sand by propagating traveling waves down the body, head to tail. Unlike the sandfish, the snake nearly followed its own tracks, thus swimming in an approximate tube of self-fluidized granular media. We measured deviations from tube movement by introducing a parameter, the local slip angle, β s , which measures the angle between the direction of movement of each segment and body orientation. The average β s was smaller for the snake than for the sandfish; granular resistive force theory (RFT) revealed that the curvature utilized by each animal optimized its performance. The snake benefits from its slender body shape (and increased vertebral number), which allows propagation of a higher number of optimal curvature body undulations. The snake's low skin friction also increases performance. The agreement between experiment and RFT combined with the relatively simple properties of the granular 'frictional fluid' make subarenaceous swimming an attractive system to study functional morphology and bauplan evolution.

Section: Methodsmentioning

confidence: 99%

Locomotor benefits of being a slender and slick sand-swimmer

Sharpe

Koehler

Kuckuk

et al. 2014

“…We collected lizards at Wrights Point (43.437°N, 118.928°W, 1318m elevation), a large lava outcrop 20km south of Burns, OR, USA, at the northern edge of the Great Basin Desert. In more southern populations, Uta are active year round and females regularly produce multiple clutches of eggs (Cowles, 1941;Sinervo and Doughty, 1996;Tinkle, 1967). The latitude and altitude of this population typically limit Uta activity to a short growing season from April to October; females lay one or two clutches of eggs depending on their size/age (Nussbaum et al, 1983;Zani, 2005) and seasonal conditions (Zani and Rollyson, 2011).…”

Section: Study Organism and Study Sitementioning

confidence: 99%

Effects of night-time warming on temperate ectotherm reproduction: potential fitness benefits of climate change for side-blotched lizards

Clarke

Zani

2012

SUMMARYTemperate ectotherms, especially those at higher latitudes, are expected to benefit from climate warming, but few data yet exist to verify this prediction. Furthermore, most previous studies on the effects of climate change utilized a model of uniform annual change, which assumes that temperature increases are symmetric on diurnal or seasonal time scales. In this study, we simulated observed trends in the asymmetric alteration of diurnal temperature range by increasing night-time temperatures experienced by female lizards during their ovarian cycle as well as by the resulting eggs during their incubation. We found that higher night-time temperatures during the ovarian cycle increased the probability of reproductive success and decreased the duration of the reproductive cycle, but did not affect embryo stage or size at oviposition, clutch size, egg mass or relative clutch mass. Furthermore, higher incubation temperatures increased hatchling size and decreased incubation period but had no effect on incubation success. Subsequent hatchlings were more likely to survive winter if they hatched earlier, though our sample size of hatchlings was relatively small. These findings indicate that higher night-time temperatures mainly affect rate processes and that certain aspects of life history are less directly temperature dependent. As our findings confirm that climate warming is likely to increase the rate of development as well as advance reproductive phenology, we predict that warmer nights during the breeding season will increase reproductive output as well as subsequent survival in many temperate ectotherms, both of which should have positive fitness effects. Supplementary material available online at

“…small rock outcrops never appear to be hibernacula), access to crevices >1m deep (in some instances, this is by multiple cracks while in others there appears to be one small entrance) and potential for winter sun to penetrate those crevices to some degree (cracks shaded by other rocks or facing generally north do not appear to be used). While U. stansburiana can be active year-round at low elevations in the south (Cowles, 1941), in the north their activity is restricted to a relatively short favorable growing season from late March or early April through October (~200days) (Nussbaum et al, 1983). Thus, lizards must survive an unfavorable season of ≥150days by retreating ≥1m into deep cracks and crevices in the cliffs on which they live.…”

Section: Study Organism and Study Sitementioning

confidence: 99%

Glycogen, not dehydration or lipids, limits winter survival of side-blotched lizards (Uta stansburiana)

Zani

Irwin

Rollyson

et al. 2012

SUMMARYClimate change is causing winters to become milder (less cold and shorter). Recent studies of overwintering ectotherms have suggested that warmer winters increase metabolism and decrease winter survival and subsequent fecundity. Energetic constraints (insufficient energy stores) have been hypothesized as the cause of winter mortality but have not been tested explicitly. Thus, alternative sources of mortality, such as winter dehydration, cannot be ruled out. By employing an experimental design that compared the energetics and water content of lizards that died naturally during laboratory winter with those that survived up to the same point but were then sacrificed, we attempt to distinguish among multiple possible causes of mortality. We test the hypothesis that mortality is caused by insufficient energy stores in the liver, abdominal fat bodies, tail or carcass or through excessive water loss. We found that lizards that died naturally had marginally greater mass loss, lower water content, and less liver glycogen remaining than living animals sampled at the same time. Periodically moistening air during winter reduced water loss, but this did not affect survival, calling into question dehydration as a cause of death. Rather, our results implicate energy limitations in the form of liver glycogen, but not lipids, as the primary cause of mortality in overwintering lizards. When viewed through a lens of changing climates, our results suggest that if milder winters increase the metabolic rate of overwintering ectotherms, individuals may experience greater energetic demands. Increased energy use during winter may subsequently limit individual survival and possibly even impact population persistence.