ZOO TALES: Lizards Abound at N.C. Zoo
For the lizard lover, few places in the area can compare to the North Carolina Zoo, with nine species -- six of which zoo visitors can view daily. Six of the species are located in the Sonora Desert exhibit, which maintains an environment conducive to lizards.
The Sonora desert collection alone contains geckos, Gila monsters, collared and crevice spiny lizards, desert iguanas and chuckwallas. Others are whiptails and beaded dragons. The last is not normally exhibited but used for animal programming and encounters with visitors.
Lizards are reptiles of the order Squamata, with nearly 5,000 species, making them the largest group of reptiles. Reptiles are classified as those air-breathing, cold-blooded vertebrates whose skin is covered in scales rather than hair or feathers. (Vertebrates are those animals with backbones or spinal columns.)
Generally, reptiles are represented by four orders: Crocodilia (crocodiles and alligators, primarily), Sphenodontia (New Zealand's tuataras), Testudines (turtles and tortoises) and Squamata (lizards, snakes and "worm-lizards").
They can be found on mountain tops, in the oceans and in deserts and forests, ranging in every continent except Antarctica. North Carolina is home to 12 species of lizards.
Lizards are marvelous creatures; some have tongues longer than their entire body, and some can even run on water -- with fringed toes; no miracles here.
They encompass about 40 families (the third hierarchal grouping in the biological classification's eight major naming ranks). They come in a tremendously large variety of colors, appearance and size. Size can range from just a few centimeters (the Caribbean gecko) to nearly nine feet (the Komodo dragon), but most species weigh less than half a pound.
Most are egg layers (oviparous), with little or no other embryonic development from the mother; however, the embryo of a few of the species develops inside the body of the mother (viviparous). Some are even able to regenerate tails.
Like humans, most lizards have eyelids that clean and protect their eyes when they blink. But a few that can't blink -- like some geckos -- have a clear membrane that shields their eyes from dirt and bright sun. Iguanas see in color, which allows them to communicate with each other and determine males from females -- helpful in the mating process.
One of the most noticeable features of lizards is the tongue, which varies greatly among the species. In general, it is mobile and forward-thrusting. Taste buds are poorly developed, so the protrusion of the tongue is primarily for bringing scent particles to the taste organs. In some species, however, it can be used as a projectile for food gathering.
Almost all lizards are carnivorous (feeding on animal tissue), though most are so small that insects are their primary prey. Some, however, are herbivorous (feeding on plant material) or omnivorous (feeding on both plants and animals). A few, such as the Komodo dragon, are so large that they can prey on some vertebrates, including boars.
One of the less-developed senses in lizards is hearing. They don't have ears like most mammals but instead have ear openings on their outer skin and eardrums just below the surface of their skin that catch sound. In reptiles like lizards, that lack a tympanic membrane in the ear, what would be the middle-ear cavity is divided into two chambers. This inner sinus is filled with fluid. (In snakes, the sinus is filled with air.) We don't have a lot of data on lizard hearing, but it is thought that their hearing comes from the movement of the perilymphatic fluid itself.
Most lizard species are harmless to humans, and only their largest species pose threat of death. The Komodo dragon, found in Indonesia, for example, has been known to stalk, attack and kill humans, but this is abnormal. The venom of the Gila monster and bearded lizard (the only truly venomous lizards in the world) is not usually deadly, but they can inflict extremely painful bites because of their powerful jaws.
The impact of lizards on humans is positive; because of their abundance, they play important roles in food chains and some benefit humans by controlling insect populations. They're abundant in most parts of the world, but -- as is the case in so many other species -- humans have caused a decline in the numbers of species, through needlessly killing them and through habitat destruction.
But zoo visitors can see their beauty and learn about their many benefits.
Tom Gillespie works for the public affairs office of the N.C. Zoo.
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