Geckos are small to average sized 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. There are an estimated 2,000 different species of geckos worldwide, with many in existence still yet to be found.The name stems from the Indonesian/Javanese word gekok, imitative of its cry. The Malay word for gecko is 'cicak'. All geckos, excluding the Eublepharinae family, have no eyelids and instead have a transparent membrane which they lick to clean. Many species will, in defense, expel a foul-smelling material and feces onto their aggressors. There are also many species that will drop their tails in defence, a process called autotomy. Many species are well known for their specialized toe pads that enable them to climb smooth and 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 insects (pests).
Geckos come in various colours and patterns. Some are subtly patterned, and somewhat rubbery looking, while others can be brightly coloured. Some species can change colour to blend in with their environment or with temperature differences. Some species are parthenogenic, the females capable of reproducing without copulating with a male. This improves the gecko's ability to spread to new islands.
Gecko toes: setae and van der Waals forces
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 spatula tipped setae
on gecko footpads demonstrate that the attractive forces that hold geckos to surfaces are van der Waals interactions
between the finely divided setae and the surfaces themselves.Every square millimetre of a gecko's footpad contains about 14,000 hair-like setae. Each seta has a diameter of 5 micrometres. Human hair varies from 18 to 180 micrometre, so a human hair could hold between 3 to 30 setae. Each seta is in turn tipped with between 100 and 1,000 spatulae. Each spatula is 0.2 micrometres long (200 billionths of a metre), or just below the wavelength of visible light.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 and is dramatically reduced under water, suggesting a contribution from capillarity
. The setae on the feet of geckos are also self cleaning and will usually remove any clogging dirt within a few steps. Teflon
, which is specifically engineered to resist van der Waals forces, is the only known surface to which a gecko cannot stick.Geckos' toes seem to be "double jointed", but this is a misnomer. Their toes actually bend in the opposite direction from our 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, this peeling action alters the angle of incidence between millions of individual setae and the surface, reducing the van der Waals force. Geckos' toes operate well below their full attractive capabilities for most of the time. This is because there is a great margin for error depending upon the roughness
of the surface, and therefore the number of setae in contact with that surface. If a typical mature gecko had every one of its setae
in contact with a surface, it would be capable of holding aloft a weight of : each spatula can exert an adhesive force of . Each seta can resist , which is equivalent to 10 atmospheres of pull.. This means a gecko can support about eight times its weight hanging from just one toe on smooth glass. The setae also have a self-cleaning action, such that each step progressively removes any clogging micro particles.
A gecko partly preserved in Burmese amber
for 100 million years, is by many ten of millions of years the oldest fossil gecko found. The preserved foot and partial tail show that gecko feet in the Lower Cretaceous
already possessed the tiny lamellae, or sticking toe setae; counting them convinced paleontologists that the fossil was a juvenile. It had a striped skin pattern that probably served as camouflage.
The amber, which was mined in the isolated Hukawng Valley, Myanmar, began its existence as tree sap, in which the unlucky lizard was caught. The new species has been given the name Cretaceogekko.
Gekkonidae is divided into five subfamilies, containing numerous genera
of gecko species
. Many geckos are kept as pets and will eat various kinds of insects
and sometimes fruit
. Not all species of geckos change their sexes in different seasons. Geckos are found (rarely) in the Galápagos Islands
Common species of gecko
- Bibron's gecko, Pachydactylus bibroni — Native to Southern Africa, this hardy arboreal gecko is relatively common as a pet.
- Crested gecko, Rhacodactylus ciliatus — Believed extinct until rediscovered in 1994. Gaining in popularity as a pet.
- Crocodile gecko or Moorish gecko, Tarentola mauritanica — very strong and heavily built for their size usually growing up to 15 cm (6 in). They are commonly found in the Mediterranean region from the Iberian Peninsula and southern France to Greece and northern Africa. Their most distinguishing characteristic is their pointed head and spiked skin with their tail resembling that of a crocodile's.
- Cyrtopodion brachykolon; commonly known as "bent-toed gecko", found in north-western Pakistan.
- Gargoyle gecko, Rhacodactylus auriculatus — commonly known as the New Caledonian bumpy gecko or gargoyle gecko. Geckos are the perfect classroom pet.
- Gold dust day gecko (Phelsuma laticauda laticauda (Boettger, 1880) (syn. Pachydactylus laticauda Boettger, 1880)) is a diurnal subspecies of geckos. It lives in northern Madagascar and on the Comoros.
- Golden Gecko, Gekko ulikovskii — native to the warm rainforests of Vietnam.
- House Gecko, Hemidactylus frenatus — A species that thrives around man and human habitation structures in the tropics and subtropics world wide.
- Indo-Pacific gecko, Hemidactylus garnotii — Also known as a fox gecko because of its long, narrow snout. This species is found in houses throughout the tropics. This gecko may eat leafcutter ants.
- New Caledonian giant gecko, Rhacodactylus leachianus — first described by Cuvier in 1829, is the largest of the Rhacodactylus geckos.
- Leopard gecko, Eublepharis macularius — The most common gecko kept as a pet is the leopard gecko, which does not have toe pads with setae, but rather claws. These enable it to more easily climb on rough surfaces like tree bark. This gecko cannot climb the glass of a terrarium. The leopard gecko tends to be docile and calm. This gecko can eat butterworms, cockroaches, crickets, mealworms, waxworms, superworms, and pink mice.
- Mediterranean gecko, Hemidactylus turcicus — residential and wild, introduced species (USA).
- Mourning gecko, originally an East Asian and Pacific species, Lepidodactylus lugubris is equally at home in the wild as in residential neighborhoods. Found in Hawaii, it may have been an early Polynesian introduction. A parthenogenic species. There is a report from Hawaii of someone having seen a larger gecko of this type eating a smaller one (or rather, running away from view with a smaller gecko halfway out of its mouth) on two occasions.
- Ptychozoon, — a genus of arboreal gecko from Southeast Asia, known as Flying Geckos or Parachute Geckos, has wing-like flaps from the neck to the upper leg, to help it conceal itself on trees and provide lift while jumping.
- Stump-toed gecko, Gehyra mutilata (Peropus mutilatus) — This gecko, commonly referred to as a Gheckl, can vary its color from very light to very dark to blend into a background. At home in the wild as well as in residential neighborhoods.
- Tree gecko, Hemiphyllodactylus typus — Tree geckos are forest dwellers.
- Tokay gecko, Gekko Gecko — a large, common, Southeast Asian gecko known for its aggressive temperament, loud mating calls, and bright markings.
- Western banded gecko, Coleonyx variegatus — Native to southwestern United States and northwest Mexico.
- Dwarf gecko, Sphaeordactylus Ariasae — native to the Caribbean islands, and the world's smallest lizard
Geckos in pop culture
- In the past few years, geckos have entered into the consciousness of the USA as the advertising icon for the insurance company GEICO, whose advertisements feature an animated anthropomorphic gecko (of the Phelsuma genus) that speaks with an East London accent.
- The current mascot of SUSE Linux distribution is a gecko called Geeko, also known as the "SUSE Lizard", but is a Chameleon for the shape.
- The logo of the car builder Wiesmann is a gecko.
- Gex is an anthropomorphic, wise-cracking gecko and the protagonist of the GEX series.
- The Pokémon Treecko, and its evolved forms Grovyle and Sceptile are based on the gecko, and so is the Neopet Techo.
- Fallout 2 features mutated geckos as low-level enemies, with more powerful variants appearing later in the game. There is also a town called Gecko, and gecko skins can be harvested.
- A gecko called Geronimo features in the book My Family and Other Animals by the celebrated naturalist Gerald Durrell.
- Edgar, a character from the webcomic Pandect is an Ace of Blue and White geckos. He is possibly a piebald blue gecko.
- In the book Spud, the narrator's friend (who dies of malaria) is named Gecko (due to the fact that he's always sick).
Film and television
- The horror film Aberration featured mutated geckos.
- In the animated film Madagascar, there is a dancing Gecko used as the King Lemur's new crown
- The design of the Malaysian superhero Cicak Man is based on the gecko; cicak is Malay for gecko.
- In the sitcom Frasier episode The First Temptation Of Daphne, Martin and Frasier use a gecko to catch a cricket in Frasier's apartment.
- Forbes, Peter (4th Estate, London 2005) 'The Gecko's Foot - Bio Inspiration: Engineered from Nature' ISBN 0-00-717990-1 in H/B