WHIPTAIL LIZARDS, TEGUS, AND RELATIVES: Teiidae

PHYSICAL CHARACTERISTICS

The whiptail lizards, tegus, and other members of this family have long, thin bodies with long legs and narrow heads with noticeable eyes and long, forked tongues. Their tails often stretch one-and-a-half times as long as the rest of their bodies and sometimes more. Some are camouflaged in drab browns, but others are colored in bright greens, reds, and blues. Their overall size may be small or large, depending on the species. In some, the adults are less than 5 inches (12 centimeters) long from the tip of the head to the end of the tail, while other species when full-grown are 4 feet 3 inches (1.3 meters) long from head to tail. In most cases, the males are a bit bigger than the females.

GEOGRAPHIC RANGE

Species of this family live only in the Western Hemisphere, from the United States south through Mexico and Central America to South America. Some species also make their homes on many islands of the Caribbean.

HABITAT

Whiptail lizards, tegus, and other members of this family tend to live in places that have some open areas where they can sunbathe, or bask. Even those that live in seemingly thick forests can find many openings in the tree cover and sit where the sunshine warms the ground. Usually, the larger species tend to make their homes in shadier habitats, while their young and the smaller species live in the sunniest, most open areas. When they aren't basking or looking for food, most species stay underground in burrows. Many make their own burrows, but some move into other animals' burrows instead. A few species live near streams and wetlands and often go for a swim. The Paraguayan caiman lizard, for instance, is an excellent swimmer that glides through the water with its powerful tail.

DIET

Most of the whiptails, tegus, and other members of this family will eat nearly any type of insect they find, and some large species will also eat fruit. The tegus eat fruit, too, but will also eat eggs, as well as living or dead animals. The Caiman lizards eat mostly snails, which they find while swimming in streams and swamps. Larger species, such as the giant ameivas that grow to be about 2 feet (61 centimeters) long, will eat small vertebrates (VER-teh-brehts), which are animals with backbones. They will also eat fruit that has fallen to the ground from plants and trees.

The lizards in this family usually hunt for their food with their keen eyesight or with their good sense of smell. Some species can pick up odors especially well and can even find insects that are buried underground.

BEHAVIOR AND REPRODUCTION

The majority of these species spend their nights in burrows, then crawl out on sunny mornings to bask. Once they are warm, they begin running here and there looking for things to eat. When they get too hot, they find some shade, and when they start to get cold, they soak up the rays in a sunny spot. Often, many individuals will live in the same area, and they usually get along very well. When breeding season starts, however, the males will fight over the females.

NO BOYS ALLOWED

Some species, like the lizard known as the desert grassland whiptail, are all females. Scientists believe that these whiptail lizards actually came about when two different species mated and had young, called hybrids (HIGH-brihds). The hybrids formed a new species of only females. In other species, a female and male must mate to produce young, but in all-female species, the female can produce young by herself. This is called parthenogenesis (PAR-thih-no-JEH-neh-sis). The mother's babies are all identical copies, or clones, of herself. Besides the whiptail family of lizards, seven other families of lizards and snakes have some all-female species.

All of the females lay eggs, rather than giving birth to babies. Some species lay only one or two eggs, while others lay thirty or more. The largest species have the most eggs, and the smallest species, the least. In addition, the larger older females usually lay more eggs than smaller younger females of the same species. For instance, a female six-lined racerunner may lay only one or two eggs her first year but three or four her second year. Most females lay their eggs in underground burrows, rotting logs, leaf piles, or some other slightly moist place. Some species drag leaves and other plant bits into their burrows and build nests for the eggs. The females stay with their eggs until they hatch.

Some species in this family are all female—they have no males and do not need them to have babies. The females give birth to young that are clones, which are perfect copies, of themselves.

WHIPTAIL LIZARDS, TEGUS, THEIR RELATIVES, AND PEOPLE

Some people hunt these lizards for their meat, fat, and/or skin, and others capture them for the pet trade.

CONSERVATION STATUS

According to the World Conservation Union (IUCN), two species are Extinct, which means they are no longer in existence. In addition, two are Critically Endangered and face an extremely high risk of extinction in the wild, and one is Vulnerable and faces a high risk of extinction in the wild. The IUCN also describes two species as Data Deficient, which means that scientists do not have enough information to make a judgment about the threat of extinction. The U.S. Fish and Wildlife Service also lists two species as Threatened or likely to become endangered in the foreseeable future. Many of the at-risk species naturally have low numbers because they only live on small islands. In this case, habitat destruction and/or collection can wipe out whole populations and possibly entire species.

SIX-LINED RACERUNNER (Cnemidophorus sexlineatus): SPECIES ACCOUNTS

Physical characteristics: The six-lined racerunner is a handsome and speedy little lizard. Its body is brown to green and has six thin yellow stripes that flow down the body from head to tail. Each stripe is separated from the next with a wide brown to black band of color. In addition, a lighter brown to gray stripe runs down the center of its back. In some populations, the head and neck are brownish, but in others they are yellowish green. Juveniles have blue or blue-green tails. Adults reach about 2.1 to 2.9 inches (5.5 to 7.5 centimeters) in length from their snout to the vent. Including the tail, they can grow to 3.3 inches (8.5 centimeters) in length. Females are usually a bit larger than males.

Geographic range: This lizard lives mainly in the southeastern quarter of the United States but also in a few areas of northern midwestern states.

Habitat: This lizard commonly makes its home in sandy areas that have lots of sun but also some shady spots where it can cool off or hide from predators (PREH-duh-ters), or animals that hunt it for food.

Diet: They eat a variety of insects, spiders, and land snails.

Behavior and reproduction: After spending the night in their burrows, these lizards come out in the morning after the sun has warmed the ground. They bask to heat up their bodies and then spend much of the rest of the day looking for food. They are extremely fast lizards for their size and quickly dart into burrows, clumps of grass, shrubby undergrowth, or some other hiding spot when they feel even slightly threatened. They can run almost 18 miles (28 kilometers) an hour. During the breeding season, the chin and chest in some males (those from the western part of the species' range) turn a bluish white, while the females' undersides remain all white. They mate in spring to early summer. Females usually lay one to six eggs, which hatch in early to mid-summer. Some females have a second clutch, or batch of eggs, later in the year. They provide no care for the eggs or the young.

Six-lined racerunners and people: Other than occasionally collecting one for a pet, people generally leave this lizard alone.

Conservation status: This species is not considered endangered or threatened. ∎

CROCODILE TEGU (Crocodilurus lacertinus): SPECIES ACCOUNTS

Physical characteristics: The tail of a crocodile tegu is very long and stretches twice as long as the rest of its body. It also has pointy scales that stand up in a row like those on a crocodile's tail. Adults are mostly greenish brown or brown with a whitish or yellow underside. Their legs have some orange spots. Adults grow to about 19.7 inches (50 centimeters) in length from head to tail.

Geographic range: They are found in South America in the area surrounding the Amazon and Orinoco rivers.

Habitat: Crocodile tegus wander in the woods and swim in streams.

Diet: They eat almost any insect or spider they can find on land or in the water.

Behavior and reproduction: With its crocodilelike tail, the crocodile tegu is an excellent swimmer. Females lay eggs. Scientists know little about its other behaviors or its reproduction.

Crocodile tegus and people: Humans and crocodile tegus rarely see or bother one another in the wild.

Conservation status: This species is not considered endangered or threatened. ∎

FOR MORE INFORMATION

Books

Badger, D. Lizards: A Natural History of Some Uncommon Creatures— Extraordinary Chameleons, Iguanas, Geckos, and More. Stillwater, MN: Voyageur Press, 2002.

Cogger, H. G., and R. G. Zweifel, eds. Reptiles and Amphibians. New York: Smithmark, 1992.

Degenhardt, W. G., C. W. Painter, and A. H. Price. Amphibians and Reptiles of New Mexico. Albuquerque: University of New Mexico Press, 1996.

Fitzgerald, L. A., J. M. Chani, and O. E. Donadio. "Tupinambis Lizards in Argentina: Implementing Management of a Traditionally Exploited Resource." In Neotropical Wildlife Use and Conservation, edited by J. G. Robinson and K. H. Redford. Chicago: University of Chicago Press, 1996.

Harding, J., and J. Holman. Michigan Turtles and Lizards. Lansing: Michigan State University Museum, 1990.

Lamar, W. The World's Most Spectacular Reptiles and Amphibians. Tampa, FL: World Publications, 1997.

Mattison, Chris. Lizards of the World. New York, NY: Facts on File, 1989.

Palmer, W. M., and A. L. Braswell. Reptiles of North Carolina. Chapel Hill: University of North Carolina Press, 1995.

Pianka, E. R., and L. J. Vitt. Lizards: Windows to the Evolution of Diversity. Berkeley: University of California Press, 2003.

Pough, F. H., R. M. Andrews, J. E. Cadle, M. L. Crump, A. H. Savitzky, and K. D. Wells. Herpetology. 2nd ed. Upper Saddle River, NJ: Prentice Hall, 2001.

Wright, J. W., and L. J. Vitt. Biology of Whiptail Lizards, Genus Cnemidophorus. Norman: Oklahoma Museum of Natural History, 1993.

Web sites

"Great Basin Whiptail." California Living Museum. http://www.calmzoo.org/stories/storyReader$81 (accessed on November 5, 2004).

"Lizards of Wisconsin: Special Tricks." Environmental Education for Kids, Wisconsin Department of Natural Resources. http://dnr.wi.gov/org/caer/ce/eek/critter/reptile/lizardsOfWisconsin5.htm (accessed on November 5, 2004).

McFarlane, B. "Cnemidophorus sexlineatus." Animal Diversity Web, University of Michigan Museum of Zoology. http://animaldiversity.ummz.umich.edu/site/accounts/information/Cnemidophorus_sexlineatus.html (accessed on November 5, 2004).

"Prairie Racerunner." Environmental Education for Kids, Wisconsin Department of Natural Resources. http://www.dnr.state.wi.us/org/caer/ce/eek/critter/reptile/prairieracerunner.htm (accessed on November 5, 2004).

"Six-Lined Racerunner." Davidson College Biology Department. http://www.bio.davidson.edu/Biology/herpcons/Herps_of_NC/lizards/Cne_sex.html (accessed on November 5, 2004).

"Unisexual Whiptail Lizards." American Museum of Natural History. http://www.amnh.org/exhibitions/expeditions/treasure_fossil/Treasures/Unisexual_Whiptail_Lizards/lizards.html?50 (accessed on November 5, 2004).