Geckos are fast moving creatures, easily zipping about. Their natural charm also is reflected here.

An ectotherm is an organism in which internal physiological sources of heat are of relatively small or of quite negligible importance in controlling body temperature. Such organisms rely on environmental heat sources, which permit them to operate at very economical metabolic rates.

All geckos shed their skin at fairly regular intervals, with species differing in timing and method. Leopard geckos shed at about two- to four-week intervals. The presence of moisture aids in the shedding. When shedding begins, the gecko speeds the process by detaching the loose skin from its body and eating it. For young geckos, shedding occurs more frequently, once a week, but when they are fully grown, they shed once every one to two months.

Like other reptiles, geckos are ectothermic, producing very little metabolic heat. Essentially, a gecko's body temperature is dependent on its environment. Also, to accomplish their main functions—such as locomotion, feeding, reproduction, etc.—geckos must have a relatively elevated temperature.

Shedding or molting[edit]

 

Video of leopard gecko shedding skin

All geckos shed their skin at fairly regular intervals, with species differing in timing and method. Leopard geckos shed at about two- to four-week intervals. The presence of moisture aids in the shedding. When shedding begins, the gecko speeds the process by detaching the loose skin from its body and eating it. For young geckos, shedding occurs more frequently, once a week, but when they are fully grown, they shed once every one to two months.

Adhesion ability[edit]

 

Close-up of the underside of a gecko's foot as it walks on vertical glass

 

Gecko on window pane

About 60% of gecko species have adhesive toe pads that allow them to adhere to most surfaces without the use of liquids or surface tension. Such pads have been gained and lost repeatedly over the course of gecko evolution. Adhesive toepads evolved independently in about 11 different gecko lineages and were lost in at least 9 lineages.

The spatula-shaped setae arranged in lamellae on gecko footpads enable attractive van der Waals' forces (the weakest of the weak chemical forces) between the β-keratin lamellae/setae/spatulae structures and the surface. These van der Waals interactions involve no fluids; in theory, a boot made of synthetic setae would adhere as easily to the surface of the International Space Station as it would to a living-room wall, although adhesion varies with humidity.

A recent study suggests that gecko adhesion is in fact mainly determined by electrostatic interaction (caused by contact electrification), not van der Waals or capillary forces.

The setae on the feet of geckos are also self-cleaning and usually remove any clogging dirt within a few steps.  Teflon, which has very low surface energy, is more difficult for geckos to adhere to than many other surfaces.

Gecko adhesion is typically improved by higher humidity, even on hydrophobic surfaces, yet is reduced under conditions of complete immersion in water. The role of water in that system is under discussion, yet recent experiments agree that the presence of molecular water layers (water molecules carry a very large dipole moment) on the setae, as well as on the surface, increase the surface energy of both, therefore the energy gain in getting these surfaces in contact is enlarged, which results in an increased gecko adhesion force. Moreover, the elastic properties of the b-keratin change with water uptake.

Gecko toes seem to be "double jointed", but this is a misnomer and is properly called digital hyperextension. Gecko toes can hyperextend in the opposite direction from human fingers and toes. This allows them to overcome the van der Waals force by peeling their toes off surfaces from the tips inward. In essence, by this peeling action, the gecko separates spatula by spatula from the surface, so for each spatula separation, only some force necessary. (The process is similar to removing Scotch Tape from a surface.)

Geckos' toes operate well below their full attractive capabilities most of the time because the margin for error is great depending upon the surface roughness, and therefore the number of setae in contact with that surface.

 

Uroplatus fimbriatus clinging to glass

Use of small van der Waals force requires very large surface areas; every square millimeter of a gecko's footpad contains about 14,000 hair-like setae. Each seta has a diameter of 5 μm. Human hair varies from 18 to 180 μm, so the cross-sectional area of a human hair is equivalent to 12 to 1300 setae. Each seta is in turn tipped with between 100 and 1,000 spatulae. Each spatula is 0.2 μm long (one five-millionth of a meter), or just below the wavelength of visible light.

The setae of a typical mature 70 g (2.5 oz) gecko would be capable of supporting a weight of 133 kg (293 lb): each spatula can exert an adhesive force of 5 to 25 nN. The exact value of the adhesion force of a spatula varies with the surface energy of the substrate to which it adheres. Recent studies  have moreover shown that the component of the surface energy derived from long-range forces, such as van der Waals forces, depends on the material's structure below the outermost atomic layers (up to 100 nm beneath the surface); taking that into account, the adhesive strength can be inferred.

Apart from the setae, phospholipids—fatty substances produced naturally in their bodies—also come into play. These lipids lubricate the setae and allow the gecko to detach its foot before the next step.

The origin of gecko adhesion likely started as simple modifications to the epidermis on the underside of the toes. This was recently discovered in the genus Gonatodes from South America. Simple elaborations of the epidermal spinules into setae have enabled Gonatodes humeralis to climb smooth surfaces and sleep on smooth leaves.

Biomimetic technologies designed to mimic gecko adhesion could produce reusable self-cleaning dry adhesives with many applications. Development effort is being put into these technologies, but manufacturing synthetic setae is not a trivial material design task.

Gecko skin does not generally bear scales, but appears at a macro scale as a papillose surface which is made from hair-like protuberances developed across the entire body. These confer superhydrophobicity, and the unique design of the hair confers a profound antimicrobial action. These protuberances are very small, up to 4 microns in length, and tapering to a point. Gecko skin has been observed to have an anti-bacterial property, killing gram-negative bacteria when it comes in contact with the skin.

The Mossy Leaf-tailed Gecko of Madagascar, U. sikorae, has coloration developed as camouflage, most being grayish brown to black or greenish brown with various markings meant to resemble tree bark; down to the lichens and moss found on the bark. It also has flaps of skin, running the length of its body, head and limbs, known as the dermal flap, which it can lay against the tree during the day, scattering shadows, and making its outline practically invisible.