Anoles, Iguanas, and Relatives: Iguanidae
ANOLES, IGUANAS, AND RELATIVES: IguanidaeCAPE SPINYTAIL IGUANA (Ctenosaura hemilopha): SPECIES ACCOUNTS
COMMON CHUCKWALLA (Sauromalus obesus): SPECIES ACCOUNTS
GREEN ANOLE (Anolis carolinensis): SPECIES ACCOUNTS
Iguanids (ee-GWA-nids) range in size from 4 to 72 inches (10 centimeters to 2 meters). They have many different body types. There are, for example, the squat, toadlike horned lizards small enough to fit in the palm of a hand; the slim, long-tailed anoles (uh-NOH-lees); and the large marine iguanas. A typical iguanid has a long tail and four legs, with five-clawed toes on each leg. Some have body colors or body patterns that match their surroundings. They may display bright colors during the mating season. Some iguanids have scales, throat fans, crests along the back, and fringes on the toes. Certain iguanids have the ability to lose the tail or part of the tail, to distract or fool a predator (PREH-duh-ter), an animal that hunts them for food. Their teeth are placed in grooves within the jaw, rather than in sockets, or holes.
Iguanids live in a variety of habitats. They usually are terrestrial, living on land. A few are arboreal, living in trees. Many prefer arid, or dry, areas. These desert dwellers often seek territories, or home areas, with at least some vegetation, rocks, or other cover to provide escape routes from predators, or animals that hunt them for food. Other iguanids seek wooded areas, including rainforests. An unusual habitat is that of the marine iguana, which lives by the ocean.
Iguanids feed on insects, spiders, and smaller lizards. A few species, such as the desert iguana and the chuckwalla, eat leaves, fruits, and flowers. The marine lizard eats (AL-jee), plantlike organisms that live mainly in water.
BEHAVIOR AND REPRODUCTION
Iguanids are cold-blooded, which means that their body temperature varies with the outside weather. At night, when it is cool, many species sleep in burrows. In the morning, iguanids emerge from their burrows and rest in the sun to warm up. They are often seen stretched out on a rock. It is necessary for them to raise their body temperature to prepare for the day's activities of feeding, perhaps breeding, and escaping ever-present predators. All iguanids are diurnal (die-UR-nuhl), meaning that they are active during the daytime. If the temperature grows too warm, these lizards find a shady spot so that they do not become overheated.
Iguanids have many predators, among them, snakes, birds, cats, rats, and wild dogs. When a predator approaches, some species remain still and blend into the surroundings. Others are quick runners and dash off almost immediately. They hide under rocks or between thick leaves and bury themselves in sand. A few species use special tactics to avoid their predators. The common chuckwalla fixes itself into a crack between rocks and then puffs up, making itself nearly impossible to remove. Horned lizards puff up too, which makes their spines stand up even higher. Biting predators will avoid the sharp spines. The zebra-tailed lizard keeps changing direction when it runs, as a way to confuse its pursuer. Other lizards squirm under the sand, so they cannot be seen.
THIS LIZARD WALKS ON WATER
Brown basilisk lizards are sometimes called "Jesus" lizards. When escaping a predator, they may appear to walk upright on water. These lizards have a fringe of scales on their hind toes. These fringes temporarily trap a bubble of air beneath the lizards' feet, which keeps them from sinking if they run quickly enough across ponds or streams.
Iguanids have lively mating behavior. Body movements include head bobbing, pushups, and open-mouth displays. Some species inflate their chests and throats and extend their dewlaps, or throat flaps, showing bright colors. They might also curl their tails or even show bright body colors.
After courtship, mating takes place. Most iguanids are oviparous (oh-VIH-puh-rus), meaning that they lay eggs. From one to sixty eggs may be laid at one time, and egg laying may take place once or as many as four times a year. The young hatch from the eggs in one to two months. A few iguanids, such as the blue spiny lizard and the short-horned lizard, give birth to live young. Usually, the parents do not care for them. The young must find their own shelter and food immediately after birth. A few species, such as the rhinoceros iguana, will protect their egg groups for a short while. They may guard the nests with threatening body displays or even physical attacks.
IGUANIDS AND PEOPLE
Iguanids do not interact with people in the wild. Habitat destruction from the clearing of forests and commercial land development can wipe out the places where the lizards hide and breed. Too much collecting for the legal and illegal pet trade causes problems for some species. Certain mammals (such as dogs and cats) that enter their territory along with humans can kill the lizards. In some areas people use larger lizards as food.
The World Conservation Union (IUCN) lists two types of iguanids as Extinct, meaning that none remains alive. Six species are Critically Endangered, which means that they face an extremely high risk of extinction in the wild. Four species are Endangered, which means that they are less endangered but still face a very high risk of extinction. These ten species might soon disappear from Earth. Twelve iguanids are Vulnerable, that is, they face threats that put them at high risk of extinction and they could vanish unless they are protected. One iguanid is Near Threatened, meaning that there is a risk that they will be threatened with extinction. There is not enough information to judge the status of seventeen other species. Attempts are being made to gather the eggs of endangered and threatened iguanids from the wild and raise the young in protected sites, such as zoos.
Physical characteristics: Cape spinytail iguanas are gray-brown, large, stocky, wrinkled lizards. They have a ridged, long tail and a crest of scales along the top of the back. Males have a larger crest than do females. An adult can reach 3 feet (1 meters) in length from the head to the tip of the tail.
Geographic range: Cape spinytail iguanas are found in northwestern Mexico, including the state of Sonora, and the islands of the Gulf of California.
Habitat: Cape spinytail iguanas live in areas with many rocky crevices, or cracks; these areas often also have trees.
Diet: Cape spinytail iguanas eat flowers, fruits, and leaves. They feed only during the day.
Behavior and reproduction: Cape spinytail iguanas are territorial, protecting their dwelling areas. If threatened, they usually run into rocky crevices. If such a hiding place is not available, they can fight with their jaws and legs. These lizards usually live in groups. Each group has a dominant male, one who acts as leader. There are also less-strong males and several females. After mating, females lay twenty-four or more eggs in a group. The eggs hatch in about three months.
Cape spinytail iguanas and people: These iguanas are sold in the pet trade.
Conservation status: Cape spinytail iguanas are not threatened. ∎
Physical characteristics: Chuckwallas are large, big-bellied lizards that can weigh up to 2 pounds (1 kilograms) and can reach a length of 16 inches (40.6 centimeters). They have a thick tail that is as long as the head and body together. The tail narrows to a blunt point at the end. Chuckwalla skin feels like sandpaper. There are folds of loose skin on the sides of the neck and body. Adult males have a black head, shoulders, and legs. The body color is red or gray, with yellow toward tail. Females and young have gray and yellow bands.
Geographic range: Chuckwallas are found in the United States.
Habitat: Chuckwallas live in rocky deserts with plenty of hiding places.
Diet: Chuckwallas feed on leaves, flowers, and fruits.
Behavior and reproduction: The chuckwalla is cold-blooded; their body temperature changes with the environment. Chuckwallas spend cool desert nights in burrows, which tend to remain warm. In the morning, when the sun comes up, they come out of their burrows. To warm up, chuckwallas bask, or stretch out, in the sun. They place their bodies sidewise to the sun, to warm them up more quickly. They bask until they reach a temperature of 100°F (38°C). Then they begin searching for food. If the surrounding temperature becomes too hot, chuckwallas hide under rocks or bushes until the weather cools down.
When disturbed, the chuckwalla hides in a rock crevice. It begins gulping air. The loose skin folds around its neck and the sides of its body puff up, until the chuckwalla becomes larger. For the moment, it is jammed in the rock crevice, and this makes it almost impossible for a predator to pull it out. If, however, a predator does manage to grab a chuckwalla by the tail, the tail separates from the body and wriggles. This distracts the predator, letting the chuckwalla escape. A new tail grows back.
Chuckwallas make a combination of movements to defend a territory or attract a mate: head bobbing, open-mouth displays, and body pushups. In the summer, females place five to ten eggs in rock crevices. The eggs hatch two months later, in early fall.
Chuckwallas and people: Chuckwallas are sold in the pet trade and sometimes are eaten as food.
Conservation status: Chuckwallas are not threatened with extinction. ∎
Physical characteristics: Green anoles are slim lizards with narrow, pointed heads and long, thin tails that can be twice as long as the rest of the animal. Body sizes range in length from 5 to 8 inches (12.7–20.3 centimeters). The body color can vary from shades of brown to shades of green. Males are larger than females. Both males and females have dewlaps, or throat fans, but the male dewlap is much larger. Dewlaps can inflate, or enlarge. An inflated dewlap is reddish-pink. Green anoles are sometimes called "chameleons" (kuh-MEEL-yuns), owing to their ability to change color, but they are not true chameleons.
Geographic range: The green anole is the only anole that inhabits the United States. These anoles are also found in Cuba and on Caribbean islands.
Habitat: The green anole lives on the ground but suns itself in small trees and shrubs, on vines and tall grasses, and within palm fronds. It likes vertical surfaces, or ones that stand upright, such as fence posts and walls.
Diet: The green anole hunts and eats small insects and spiders and laps water from leaves.
Behavior and reproduction: Green anoles are active in the daytime. If they are grabbed or threatened, their tails can fall off. A new tail will grow, but the new tail usually does not match the previous one in color or size.
During the breeding, or mating, season, males court females by facing them. They bob their heads up and down, and expand, or make larger, the bright pink dewlap under the throat. Next, the male may approach the female with a stiff-legged walk. If the female accepts the male, she stays still and arches her neck. If she does not accept him, she runs away. After mating, female lays single eggs every two weeks, for a total of about ten eggs per breeding season. She places the eggs in warm, moist spots, such as leaf litter. Young appear in five to seven weeks.
Green anoles and people: Green anoles are popular pets.
Conservation status: Green anoles are common in the southeastern United States. ∎
FOR MORE INFORMATION
Arnosky, Jim. All about Lizards. New York: Scholastic, 2004.
Bartlett, Richard D., and Patricia Pope Bartlett. Lizard Care from A to Z. Hauppauge, NY: Barron's Educational Series, 1997.
Bartlett, Richard D., and Patricia Bartlett. Anoles: Facts & Advice on Care and Breeding. Hauppauge, NY: Barron's Educational Series, 2001.
Behler, John L. The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf, 1979.
Claybourne, Anna. The Secret World of Lizards. Chicago: Raintree Publishers, 2003.
Conant, R., J. T. Collins, I. H. Conant, T. R. Johnson, and S. L. Collins. A Field Guide to Reptiles & Amphibians of Eastern & Central North America. Boston: Houghton Mifflin, 1998.
Lamar, William. The World's Most Spectacular Reptiles & Amphibians. Tampa, FL: World Publications, 1997.
Uchiyama, Ryu. Reptiles and Amphibians. San Francisco: Chronicle Books, 1999.
"Amazing Lizards!" National Geographic (March 1978): 8–11.
"Color These Animals before They Change." National Geographic (March 1980): 10–15.
Hazen-Hammond, S. "Horny Toads Enjoy a Special Place in Western Hearts." Smithsonian 25 (1994): 82–86.
Hughes, Catherine D. "Where Am I?" National Geographic Kids (July/August 2004): 32–35.
"Iguanas." Ranger Rick (August 1996): 8–9.
"Marine Iguanas." Ranger Rick (November 2003): 18–20.
"Shrinking Iguanas." National Geographic (September 2000).
"Anoles." Melissa Kaplan's Herp Care Collection. http://www.anapsid.org/anole.html (accessed on July 31, 2004).
"Glossary of Iguana Terms." Green Iguana Society. http://www.greenigsociety.org/glossary.htm (accessed on August 3, 2004).
"Green Anole." Texas Parks and Wildlife. http://www.tpwd.state.tx.us/nature/wild/reptiles/anole/ (accessed on July 31, 2004).
"Green Anole Care Sheet." AOL Hometown. http://members.aol.com/Mite37/TPFGA.html (accessed on July 31, 2004).
"Marine Iguanas." Galápagos Geology on the Web. http://www.geo.cornell.edu/geology/GalápagosWWW/MarineIguanas.html (accessed on August 3, 2004).