Geckos are gaining popularity as exotic pets, and there are over 1,500 species of these lizards worldwide. The Crested Gecko and the Leopard Gecko are the most popular species for pets, but others are also becoming better known and admired.Geckos come in a wide range of sizes, with the smallest gecko being the Jaragua Sphaero at just under an inch. It is also the smallest reptile in the world. The largest geckos still in existence today are the New Caledonian Giant Gecko at 14 inches and the Tokay Gecko at up to 15 inches. The New Caledonian Giant Gecko has an odd appearance with loose-looking skin, while the Tokay has a bite that can last several minutes or even an hour.Geckos are vocal and communicate through barks, chirps, clicks, and hisses, which can be for defense or social behavior. They can also walk up walls and glass aquarium tanks thanks to microscopic hairs on the pads of their feet that can fit into small openings. The Leopard Gecko has claws instead of pads, making it easier for climbing trees.The Leopard Gecko gets its name from its colorings and markings resembling those of a leopard. The sex of their newborns is determined by the temperature at which incubation occurs. Geckos can also drop their tails as a defense mechanism, but the Crested Gecko cannot grow its tail back.Geckos store fat in their tails to survive lean times, and the regenerated tails do not look the same as the original ones, with duller colors and markings and a stubbier appearance.