Geckos are small to moderately large lizards belonging to the family Gekkonidae which are found in warm climates throughout the world. Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos. Geckos are unusual in other respects as well. Geckos have no eyelids and instead have a transparent membrane which they lick to clean. A few species have the ability to shoot an irritating liquid out of the end of its tail. They are also known to have the ability to change the colour of their skins although they have not mastered it like the chameleons and can only go pale. Many species have specialized toe pads that enable them to climb smooth vertical surfaces and even cross indoor ceilings with ease. These antics are well-known to people who live in warm regions of the world where several species of geckos make their home inside human habitations. These species (for example the House gecko) become part of the indoor menagerie and are seldom really discouraged because they feed on insect pests.
Most geckos are tan to dark grey, subtly patterned, and somewhat rubbery looking. Some species can change color to blend in with their surroundings or with temperature differences. However others can be brightly colored.
Some species are parthenogenic, the females capable of reproducing without copulating with a male. This improves the geckos’ ability to spread to new islands.
The toes of the gecko have attracted a lot of attention, as they adhere to a wide variety of surfaces, without the use of liquids or surface tension. Recent studies of the setae on gecko footpads demonstrates that the attractive forces that hold geckos to surfaces are van der Waals interactions between the finely divided setae and the surfaces themselves. That these kinds of interactions involve no liquids (or no gases) is important; 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. [Wikipedia]