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Reptiles
There are nearly 800 species of gecko. These lizards are found worldwide except in the northern latitudes. They are especially diverse in the tropical regions. The name "gecko" probably refers to their calls which are produced by clicking the broad tongue against the roof of the mouth. Most geckos have well-developed vocal cords, and many species, including the tokay and the talkative gecko, have an elaborate vocal repertoire. Some species produce a series of modulated clicks, which vary according to the social situation, such as territorial defense and mating. The sole of a gecko's foot has ridges (not suction cups) for gripping tiny irregularities, enabling geckos to run up and down vertical surfaces and even to run upside-down across ceilings. Several species of tree-dwelling geckos have prehensile tails. Most species are active at night so their color and skin patterns are relatively undistinguished. The few that are active during the day are much more brightly colored and strikingly patterned. Some of these forms have adult males that are more colorful than adult females (sexual dichromatism). Those geckos that are active at night have very large eyes, and the shape of the pupil varies according to different light intensities. The pupil is reduced to a very narrow vertical slit in direct sun and to a large, round opening in very low light levels. Most species eat insects. A few will eat small mammals and birds. There are some that eat nectar and sweet exudate (secretions) from tree bark. In recent years people in the Texas area may have seen the small, translucent Mediterranean gecko (Hemidactylus turcicus). This is an introduced species which is thought to have been a stowaway on ships coming into U.S. ports. It is common to see these lizards stationed near an outdoor light source, waiting for insects. They are beneficial to us not only because they eat small flying insects, but they eat cockroach eggs, too! The San Antonio Zoo exhibits the fat-tailed gecko, sand gecko, day gecko, and leaf-tailed gecko.
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