No abstract

Carbon stable isotope (delta(13)C) analysis can be used to infer the origin and to estimate the flow of nutrient resources through animals and across ecological compartments. These applications require knowledge of the rates at which carbon is incorporated into animal tissues and diet-to-tissue discrimination factors (Delta(13)C). Studies of carbon dynamics in terrestrial vertebrates to date have focused almost solely on endothermic animals; ectotherms such as reptiles have received little attention. Here we determined carbon incorporation rates and Delta(13)C in tissues of prairie lizards (Sceloporus undulatus consobrinus) and collared lizards (Crotaphytus collaris). The smaller lizard, S. undulatus, had carbon retention times of 25 and 61 d in plasma and red blood cells (RBC), respectively, compared with 44 and 311 d for the larger C. collaris. Liver, muscle, and skin carbon retention times for S. undulatus were 21, 81, and 94 d. Growth contributed 9%-19% of the carbon incorporated into these tissues. This contribution is similar to endotherms measured at comparable developmental stages. Mean Delta(13)C for plasma (-0.2 per thousand +/- 0.4 per thousand Vienna Pee Dee Belemnite Standard) and RBCs (-1.3 per thousand +/- 0.8 per thousand) were similar to values reported for other vertebrates. Carbon incorporation rates for these ectotherms, however, are seven times slower than in similarly sized adult endotherms. Although a limited comparison with data for warm-water fishes suggests comparable incorporation rates between aquatic and terrestrial ectotherms, this study highlights the lack of experimental data for isotope dynamics in ectotherms across a range of temperatures, body sizes, and developmental stages.

SUMMARY Obtaining population-level life history data such as egg and clutch size in reptiles has most often required that individuals be sacrificed. This prevents a reexamination of individuals over intra-annual and inter-annual time scales,limiting insight into the effects of varying environmental conditions on reproductive output. Here, we test the use of a laptop-sized portable ultrasound imaging system as a nondestructive means for quantifying reproductive investment in five species of lizards with a range of body sizes,forms and life histories. Ultrasound scans produced egg counts that were accurate for clutch sizes of two to seven eggs, and provided good estimates(within 5.5±1.69 eggs, mean ± s.e.m., relative error 21%) for clutch sizes of between 18 and 41 eggs. Egg measurements using virtual calipers produced average egg volumes that deviated from actual volumes by 0.09±0.01 cm3 (relative error 25.9%), and estimated clutch volumes that differed from actual volumes by 1.03±0.26 cm3(relative error 29.5%). We also monitored development in five lizard species and found that changes in follicle and egg size and degree of embryonic development can be measured over periods of just a few days.

SUMMARY Jumping is a common form of locomotion for many arboreal animals. Many species of the arboreal lizard genus Anolis occupy habitats in which they must jump to and from unsteady perches, e.g. narrow branches, vines, grass and leaves. Anoles therefore often use compliant perches that could alter jump performance. In this study we conducted a small survey of the compliance of perches used by the arboreal green anole Anolis carolinensis in the wild (N=54 perches) and then, using perches within the range of compliances used by this species, investigated how perch compliance (flexibility) affects the key jumping variables jump distance, takeoff duration, takeoff angle, takeoff speed and landing angle in A. carolinensis in the laboratory (N=11). We observed that lizards lost contact with compliant horizontal perches prior to perch recoil, and increased perch compliance resulted in decreased jump distance and takeoff speed, likely because of the loss of kinetic energy to the flexion of the perch. However, the most striking effect of perch compliance was an unexpected one; perch recoil following takeoff resulted in the lizards being struck on the tail by the perch, even on the narrowest perches. This interaction between the perch and the tail significantly altered body positioning during flight and landing. These results suggest that although the use of compliant perches in the wild is common for this species, jumping from these perches is potentially costly and may affect survival and behavior, particularly in the largest individuals.

Summary1. Animals in the wild must navigate habitats that vary in structure and complexity. For arboreal animals, perch compliance (flexibility) is a common and variable characteristic, but the effects of perch compliance on arboreal behaviour and locomotion, specifically jumping, have only been examined for primates in the wild. 2. In this study, we observed jumping behaviour of green anole lizards (Anolis carolinensis) at a site with perches ranging from highly compliant palm leaflets to sturdy trunks and branches. We measured the characteristics, including compliance, of perches found throughout this habitat, those generally used by the green anole and those used for jumping within this population. We then compared the characteristics of these perch types to better understand how green anoles interact with compliant perches in the wild. 3. We found that green anoles used perches ranging across all compliances found in the habitat, but they selectively jumped from relatively non-compliant perches. Green anoles also tended to jump farthest from relatively sturdy, low-lying perches. Therefore, green anoles avoided the most compliant perches when jumping, likely due to the performance costs associated with compliant perch use. 4. In addition, we discovered that generally, perches become more compliant as they become narrower, but variance in compliance for a given diameter does not allow for the use of diameter as a proxy for compliance in this type of habitat. Thus, studies of compliance effects on small animal movement should include direct measurements of perch compliance. 5. We assert that perch compliance is an important habitat characteristic that influences behaviour and performance in green anoles, and likely many other small jumping animals.