Lizard facts and fallacies

StoryImage( ‘/Images/Story//Auto-img-119203967328107.jpg’, ‘Photo by Dr. Robert A. Hedeen’, ‘The harmless gecko lizard has adhesive pads on the tips of its toes to help it capture insects.‘);

Editor’s note: Long-time outdoors columnist Dr. Robert A. Hedeen passed away Oct. 4 (see related article in section A). Prior to his passing, he had compiled a number of columns for publication. Those columns will appear in print until all have been published.

Lizards belong to the class Reptilia of vertebrate animals and are characterized by having a skin that is covered with scales and is impervious to water loss. Their eggs are covered by a leathery shell that also prevents loss of water, and they have a three-chambered heart. Included in this class are the lizards, snakes, turtles and crocodilians.

On the evolutionary tree of the vertebrates, the reptiles are one limb higher than the amphibians, which includes frogs, toads, salamanders and similar creatures. The great advantages reptiles had over amphibians are the watertight skin and eggshells, which allowed them to roam far and wide about the landscape and occupy a variety of ecological niches. Amphibians are forever closely linked to water because they lack these two attributes. As a matter of fact, when reptiles first evolved millions of years ago, they almost drove the amphibians to extinction.

A lizard is sometimes viewed as the prototype of reptiles, but many are unaware of the diversity exhibited by this group. The following will describe some peculiar attributes of some lizards of which most individuals are at least vaguely familiar:

Horned Frog: This mascot of Texas Christian University (TCU) is not a frog at all but a lizard with menacing protective horns protruding from its head and body. If this native of the Southwest were 100 times larger, it could be taken for a living dinosaur. Many tales have developed about this strange looking lizard, one of which is that it can squirt blood from its eyes. As a matter of fact, this is a true but very rare occurrence. It seems if this gentle creature is picked up, its blood pressure rises rapidly, and capillaries in the corners of the eyes may rupture and blood is ejected a few inches.

If you ever wanted to try your hand at hypnotizing something, the horned frog is a good subject. If the animal is stroked gently between its eyes, it will usually lapse into a deep sleep that may last for hours.

Gila Monster: There are some 3,000 species of lizards described, and only two are known to be venomous: the Gila monster and the Mexican poisonous lizard. The monster is found in the Southwestern U.S., and its cousin is confined to south of the border into Central America. The Gila monster is a chunky beast and may attain a length of 2 feet. Its pebbled scales are flecked with orange, black and yellow and have earned it the name of the beaded lizard. The venom of this animal is quite potent, and a few human deaths from its bite have been recorded. The few fatalities result from the fact the lizard is not aggressive, and it does not have hollow fangs for the instant injection of venom. Rather, the venom flows slowly, and the beast must chew on its prey for a considerable time before a lethal dose is administered. They have the reputation, however, of hanging on to a victim with the tenacity of a bulldog.

Dragons of Komodo: Early in the 1900s, the civilized world was stunned to learn that huge dragon-like lizards existed on the island of Komodo in what is now Indonesia. These creatures reportedly emitted smoke and steam from their mouths and routinely included a native on their menu for dinner. They were described as being 20 feet in length. This was all pure fiction as they certainly do not breathe out smoke and steam, and the largest one ever known was just a bit more than 10 feet in length. A zoologist studied them at close range for some time, and though he approached them within a few feet, they gave no sign of attacking him. He reported they sometimes fed on wild pigs and small goats, and it is not inconceivable that they might attack a human if cornered or provoked. The few remaining “dragons” are protected by the Indonesian government.

American Chameleons: There are no true chameleons in the United States, although I have seen lizards called chameleons sold at carnivals. True chameleons are found only in Africa and Asia, with one species in Spain. A chameleon is a strange-looking lizard. It is flattened from side to side and has bulging eyes, each of which can move independently of the other. It has a protrudable tongue that is longer than its body with which it adeptly catches insects. A true chameleon has the ability to change its color to match the backdrop of its environment.

The American “chameleon” is not a chameleon at all but usually a rather common lizard called the Caroline anole. The anole has a limited ability to change color. It is usually green in color, but sometimes can change to a brown. If an anole is placed on a white background, it will not change color, and frequently will not change from green to brown or brown to green. Factors such as light, temperature and the emotional state of the animal seem to dictate its ability to change.

Lizards are a diverse group of reptiles that show extreme evolutionary diversity, which enables them to adapt to almost any environment, except the very cold.

from the Oct. 10, 2007, issue

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