Casey Gilman

Creating Gecko‐Like Adhesives for “Real World” Surfaces

DOI: 10.1002/adma.201306259 world” surfaces which have large scale roughness. To generate high forces on millimeter and centimeter length scales, geckos posess a unique sub-surface morphology of stiff tendon tissue integrated directly into the skin, creating lamellar fl aps referred to as scansors. These scansors enable a “draping” property for the skin, allowing the gecko to generate strong forces over macroscopic length scales. [ 9,26,27 ] “Draping” is characterized by the ability to conform while maintaining in-plane stiffness. [ 26,28 ]

Foils of flexion: the effects of perch compliance on lizard locomotion and perch choice in the wild

Summary 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. 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. 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. 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. 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.

Capital Breeding and Allocation to Life-History Demands Are Highly Plastic in Lizards

The use of stored resources to fuel reproduction, growth, and self-maintenance in the face of uncertain nutrient availability is a tactic common to many organisms. The degree to which organisms rely on stored resources in response to varied nutrients, however, is not well quantified. In this study, we used stable isotope methods to quantify the use of stored versus incoming nutrients to fuel growth and egg and fat body development in lizards under differing nutrient regimes. We found that the degree of capital breeding is a function of an individual’s body condition. Furthermore, given sufficient income, lizards in poor condition can allocate simultaneously to storage, growth, and reproduction and “catch up” in body size and reproductive allocation to better-conditioned animals. Using natural variation in the δ13C of environmental nutrient pulses, we also found a high degree of variation in capital breeding in a lizard community. These findings demonstrate that capital breeding in lizards is not simply a one-way flow of endogenous stores to eggs but is a function of the condition state of individuals and seasonal nutrient availability. We use our findings to comment on capital breeding in lizards and the utility of the capital-income concept in general.

Total recoil: perch compliance alters jumping performance and kinematics in green anole lizards (Anolis carolinensis).

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.

Geckos as Springs: Mechanics Explain Across-Species Scaling of Adhesion

One of the central controversies regarding the evolution of adhesion concerns how adhesive force scales as animals change in size, either among or within species. A widely held view is that as animals become larger, the primary mechanism that enables them to climb is increasing pad area. However, prior studies show that much of the variation in maximum adhesive force remains unexplained, even when area is accounted for. We tested the hypothesis that maximum adhesive force among pad-bearing gecko species is not solely dictated by toepad area, but also depends on the ratio of toepad area to gecko adhesive system compliance in the loading direction, where compliance (C) is the change in extension (Δ) relative to a change in force (F) while loading a gecko’s adhesive system (C = dΔ/dF). Geckos are well-known for their ability to climb on a range of vertical and overhanging surfaces, and range in mass from several grams to over 300 grams, yet little is understood of the factors that enable adhesion to scale with body size. We examined the maximum adhesive force of six gecko species that vary in body size (~2–100 g). We also examined changes between juveniles and adults within a single species (Phelsuma grandis). We found that maximum adhesive force and toepad area increased with increasing gecko size, and that as gecko species become larger, their adhesive systems become significantly less compliant. Additionally, our hypothesis was supported, as the best predictor of maximum adhesive force was not toepad area or compliance alone, but the ratio of toepad area to compliance. We verified this result using a synthetic “model gecko” system comprised of synthetic adhesive pads attached to a glass substrate and a synthetic tendon (mechanical spring) of finite stiffness. Our data indicate that increases in toepad area as geckos become larger cannot fully account for increased adhesive abilities, and decreased compliance must be included to explain the scaling of adhesion in animals with dry adhesion systems.

Respiratory Biology during Gravidity in Crotaphytus collaris and Gambelia wislizenii

Abstract During gravidity lizards experience a striking decrease in lung volume as a result of lung compression by eggs growing within the body cavity. In order to understand the effect of this decrease in lung volume on the respiratory biology of gravid egg-laying lizards, we measured changes in total lung volume, resting and postexercise expired volume, minute volume, respiratory frequency, and carbon dioxide production rate during reproduction in the Collared Lizard, Crotaphytus collaris, and the Leopard Lizard, Gambelia wislizenii. We found that compression of the lungs by shelled eggs resulted in an average 48% (range: 26–70%) decrease in total lung volume compared to the same postlaying C. collaris females, and an average 38% (range: 29–46%) decrease in G. wislizenii. CO2 production rates were altered significantly during reproduction in female C. collaris and were 58% higher in females carrying late-stage follicles, compared to after laying. Despite the remarkable reduction in lung volume in both of these species and the increase in CO2 production rates in C. collaris, no ventilation parameters changed over the course of reproduction. The highly distensible body cavities of C. collaris and G. wislizenii appear to be able to accommodate both growing eggs and adequate lung volumes for normal respiratory function during gravidity.

Effects of Surface Diameter on Jumping Kinematics and Performance in Two Arboreal Gecko Species (Correlophus ciliatus and Rhacodactylus auriculatus)

Abstract Jumping is one of the most common modes of locomotion for animals, and animals in the wild often jump off a range of substrates. We tested the effects of varying surface diameter (1 and 5 cm) on jumping performance and kinematics in two species of arboreal geckos (Rhacodactylus auriculatus and Correlophus ciliatus). Both are medium-sized (~10–15 g) geckos that readily jump off a range of diameters. We filmed maximal jumps with a Photron high-speed camera at 500 frames · s−1. We found that diameter had little impact on either jumping performance (distance) or kinematics (takeoff angle and speed, landing angle, jump duration), but mass had a positive effect on both jump distance and takeoff speed in C. ciliatus. Further, C. ciliatus exhibited higher takeoff velocities and tended to have greater jump distances compared to R. auriculatus. The factors causing this among-species difference are unclear, but differences in both tail morphology and how these species use their tails could partly explain this difference. Our study confirms other studies, which show that lizards are scarcely affected by diameter in terms of jumping, and we discuss some of the reasons for why lizards are able to effectively overcome this environmental challenge.

Fat seals forage most efficiently

![Figure][1] Northern elephant seals are truly impressive divers. During months-long migrations, they spend most of their time underwater, diving hundreds of meters down into the sea. Whats even more impressive is that these animals are breath-hold divers. This means that they must empty

Boxfish don't swim the straight and narrow

![Figure][1] Agile though awkward looking, coral reef-dwelling boxfish are aptly named for their unusual box-like shape, which is made up of many fused bony plates. This boxy shell, along with the toxins some boxfish secrete, works well as a defense against predation. However, the shell

Arboreal locomotion: aye, there's the rub!

![][1] A surprisingly diverse array of animals, from spiders to mammals, have adhesive structures on their feet that allow them to run along vertical surfaces, climb high in the canopy, or hang upside down to await their prey. Lizards, particularly geckos, have received a lot of