1/8 GEKKONIDAE: GENERAL NOTES Geckos Standing’s Day Gecko Phelsuma standing PHYLUM / SUBPHYLUM Chordata / Vertebrata CLASS Reptilia ORDER / SUBORDER Squamata / Lacertilia FAMILY / SUBFAMILY Gekkonidae / 5 Subfamilies (see Chart) GENUS / SPECIES 100+ Genera / 1,000+ Species Well-known gekkonids include: Flying Gecko, House Gecko, Knob-tailed Gecko, Mediterranean Gecko, Mourning Gecko, Standing’s Day Gecko*, Tokay Gecko. (*: PZ) PZ gekkonids include: Standing’s Day Gecko. GEOGRAPHIC RANGE Worldwide in tropical, subtropical and some warm temperate areas. Can range as far north as the southwestern U.S., southern Europe and southern Siberia. To the south, can reach Stewart Island in New Zealand and approach the southern tip of South America. Few species live in North America, Europe or temperate Asia. HABITAT Desert, forest, savanna, grassland. Most live in arid and semiarid habitats in Africa and Australia and in forested parts of S.E. Asia and Madagascar. Most common at lower elevations, but can be found up to 12,000’ in the Himalayas. TOURING HIGHLIGHTS - The feet are one of the most striking and varying aspects of the morphologic characteristics of geckos. Eublepharines and some gekkonines and diplodactylines have slender digits with well-developed claws, but many species have expanded pads on the base and or tips of the toes that permit adhesion to smooth surfaces. These pads may be distal (at the tips of the toes) and fan-shaped (Pteyodactylus) or leaf-shaped (Phyllodactylus) or they may be basal (at the base of the toes) and arranges in single (Gekko) or divided (Hemidactylus) rows. The first digits of the hands and feet may be reduced in size, but it is never lost entirely. Gekkonidae: General Notes 2/8 - The toes of the gecko have developed a special adaptation that allows them to adhere to most 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 millimeter of a gecko's footpad contains about 14,000 hair-like setae. Each seta has a diameter of 5 micrometers. Human hair varies from 18 to 180 micrometers, so a human hair could hold between 3 and 36 setae. Each seta is in turn tipped with between 100 and 1,000 spatulae. Each spatula is 0.2 micrometers long (200 billionths of a meter), 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 has very low 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 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, 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 2.5 oz. gecko had every one of its setae in contact with a surface, it would be capable of holding aloft a weight of 290 lb.: each spatula can exert an adhesive force of 10 nanonewtons (0.0010 mgf). Each seta can resist 10 milligrams-force (98 N), which is equivalent to 10 atmospheres of pull. This means a gecko can support about 8X its weight hanging from just one toe on smooth glass. - Geckos are unique among lizards in their vocalizations, making chirping sounds in social interactions with other geckos. - In the Mourning Gecko (Lepidodactylus lugubris) and a few other species, there are no males. Such unisexual species have arisen from the hybridization of two bisexual parental species and, once established, reproduce clonally by parthenogenesis. - Most geckos lay eggs but the geckos of New Zealand and one species in New Caledonia are live-bearing (viviparous) and possess a simple placenta. These species always produce twins which may gestate for 4-14 months. SURVIVAL STATUS AND / OR CONSERVATION - IUCN: 31 species (Extinct, 3 species; Extinct in the Wild, 1 species; Critically Endangered, 1 species; Endangered, 3 species; Vulnerable, 15 species; Lower Risk/Near Threatened, 8 species). - CITES II: the especially brightly colored and attractive geckos of the genus Phelsuma are popular in the pet trade. - Population estimates exist for very few geckos and the conservation status of most species is unknown. - Many geckos live in desert areas that are affected little by humans or, like some tropical species, actually exploit human habitation for their own use. Gekkonidae: General Notes 3/8 - Many island-dwelling geckos with restricted distributions, however, are imperiled by habitat destruction, particularly deforestation, and by the introduction of rats, cats and other predatory mammals. ENEMIES AND / OR DEFENSE - Enemies: spiders, introduced exotic species (rats, stoats). - Defense: geckos use vocalizations, in combination with bites and defecation, to deter predators. - Defense: many geckos have cryptic coloration or outline-concealing skin folds and flaps to avoid detection. - Defense: a few geckos, such as the Namib Day Gecko (Rhoptropus afer) can outrun most predators. - Defense: tail autotomy is common. Threatened geckos lure predators to attack the tail, which continues to wriggle after it is shed, distracting the predator and allowing the gecko to escape. The loss of the tail usually carries with it a significant energetic cost, but, in the Marbled Gecko (Christinus marmoratus), tail loss has the immediate benefit of increased running speed. - Defense: certain geckos, mostly island species, can shed large portions of their body skin if they are grasped by predators and they can regrow skin over the large wounds. - Defense: members of 2 genera of diplodactyline geckos (Strophurus and Eurydactylodes) can ooze or squirt a sticky fluid from their tails that can entangle the mouth parts of such predators as spiders. PHYSICAL - Configuration: small to medium size, stocky, flattened bodies with large heads. - Size: average 1.2”-3.5” (range 0.6”-10”) snout-vent length. The smallest gecko, the Jaragua Sphaero (Sphaerodactylus ariasae), discovered in 2001, averages only 0.63” in snout-vent length. The New Caledonian Giant Gecko (Rhacodactylus leachianus) reaches 10”. - Color: often drab. Browns and grays are the most common colors and diffuse patters of chevrons or crossbars characterize many species. In diurnal forms, such as the Malagasy Day Gecko (Phelsuma), bright greens, yellows, reds and blues may be encountered. - Skin/Scales: usually covered with small granules, with or without larger keeled tubercles (enlarged scales with a raised ridge) intermixed. Many species have loose, velvety skin made up of minute granular scales, whereas others have a dorsal surface with clusters of pronounced tubercles surrounded by smaller scales. Abdominal scales are often large, plate- like and overlapping. - Body: stout, shortened and somewhat flattened. - Head: large, diamond-shaped. - Eyes: large, set laterally on a sloping forehead. All geckos, excluding the Eublepharinae subfamily, have no eyelids and, instead, like snakes, have a transparent membrane, a clear, protective covering over the eyes, which they lick to clean with their protrusible notched tongue. The pupils of common nocturnal species are vertical and are often lobed in such a manner that they close to form four pinpoints. A feature of nocturnal geckos in which they differ from most other vertebrates, is that they only have cones in their retinas and their pupils are narrow and vertical to block out light. Other geckos have round pupils. - Ears: auditory openings are generally round to oval in shape. - Snout: short, blunt. Gekkonidae: General Notes 4/8 - Jaws: large, hard, shiny nasal and chin shields cover the margins of the jaws and nasal area and contrast markedly with the dull and velvety head and body scales. - Tongue: wide, flat with a notch in its leading edge and frequently used for licking the face and eyes. - Dentition: typically pleurodont and the teeth are numerous. They range from small, conical, homodont and pleurodont, occurring on the dentary, maxilla and premaxilla. The anterior teeth are generally larger than the posterior teeth. Palatine teeth are absent. - Tail: may be long and tapering, short and blunt, or even globular. The tail serves in many species as an energy storehouse on which the animal can draw during unfavorable conditions. The tail may also be extremely fragile and, if detached, is quickly regenerated in its original shape. It is prehensile in some species. - Limbs: well-developed, with larger hind limbs than forelimbs. Geckos have well-developed, pentadactylic limbs with complex modifications to toe shape. Some rock-dwelling and arboreal species have pad-like toes with complex subdigital lamellae, although others retain primitive claw-like toes without laterally expanded pads. Some terrestrial forms also share lamellar specialization, whereas others have simple toes. The individual lamellae are actually compound pads made up of microscopic projections or setae which take hold on the substratum. - Feet: Most geckos have feet modified for climbing. The pads of their long toes are covered with small plates that are in turn covered with numerous tiny, hair-like processes that are forked at the end.