A 3-foot-long (1 meter) green iguana appeared one day when Will Jenkins was relaxing with his family in Costa Rica. Jenkins quickly grabbed his camera.

Lizards are reptiles. There are over 4,675 species of lizard, according to the San Diego Zoo. Others sources say there are about 6,000 species. Included in this large number are lizards with four legs, some with two legs and some with no legs at all; lizards with frills, horns or wings; and lizards in nearly every color imaginable.

Size

Lizards generally have small heads, long bodies and long tails. With so many species of lizard, it's understandable that they come in a wide variety of sizes. The largest lizard is the Komodo dragon. It grows up to 10 feet (3 meters) long and weighs up to 176 lbs. (80 kilograms). The smallest lizard is the tiny dwarf gecko, which grows to 0.6 inches (1.6 centimeters) long and weighs .0042 ounces (120 milligrams).

Habitat

Lizards are found all over the world in almost every type of terrain. Some live in trees; others prefer to live in vegetation on the ground, while others live in deserts among rocks. For example, the Texas horned lizard is found in the warm areas with little plant cover in southern North America. The northern fence lizard, on the other hand, likes to live in cool pine forests in northern North America.

Komodo dragons have long, forked tongues that they use to help smell and taste. Shutterstock) (Image credit: Sergey Uryadnikov

Habits

Most lizards are active during the day. Lizards are cold-blooded animals, which means they rely on their environment to help warm their bodies. They use the heat of the sun to raise their body temperatures and are active when their bodies are warm. The sun also helps lizards produce vitamin D. Their days are spent sun-bathing on rocks, hunting for food or waiting for food to come their way.

Some lizards are territorial, while others can easily live with dozens of other lizards of many different species. Other than mating times, most lizards are not social, though. There are some exceptions. For example, the desert night lizard lives in family groups, according to research by the University of California.

A lizard's scaly skin does not grow as the animal ages. Most lizards shed their skin, or molt, in large flakes. Lizards also have the ability to break off part of their tails when a predator grabs it.

Diet

Many lizards are carnivores, which means they eat meat. A typical diet for a lizard includes ants, spiders, termites, cicadas, small mammals and even other lizards. Caiman lizards eat animals with shells, such as snails.

Other lizards are omnivores, which means they eat vegetation and meat. One example of an omnivore lizard is Clark's spiny lizard. These lizards like fruits, leaves and vegetables.

Some lizards are herbivores and only eat plants. The marine iguana, which lives in the Galapagos Islands, eats algae from the sea. Iguanas and spiny-tailed agamids also eat plants.

Offspring

Many lizards lay eggs while others bear live young. For example, frilled lizards lay eight to 23 eggs, according to National Geographic, while some skinks have live young. The gestation for a lizard egg can last up to 12 months.

Most baby lizards are self-sufficient from birth and are able to walk, run and feed on their own. The young reach maturity at 18 months to 7 years, depending on the species. Some lizards can live up to 50 years.

A wild brown basilisk (Basiliscus vittatus), photographed in Guatemala. The animal is nicknamed Jesus lizard for its ability to run across water. (Image credit: Ana Balcarcel)

Classification/taxonomy

Here is the classification of lizards according to Integrated Taxonomic Information System (ITIS):

Kingdom: Animalia Subkingdom: Bilateria Infrakingdom: Deuterostomia Phylum: Chordata Subphylum: Vertebrata Infraphylum: Gnathostomata Superclass: Tetrapoda Class: Reptilia Order: Squamata Suborders: Amphisbaenia, Autarchoglossa, Gekkota, Iguanias, Serpentes

The suborder Dibamidae, with the genera Anelytropsis and Dibamus, may also be included, though ITIS says these categories have "uncertain position."

Conservation status

Lizards vary in their conservation status, much like their traits vary. Many, according to the International Union for Conservation of Nature's Red List of Threatened Species, are endangered or critically endangered, meaning they may be close to extinction. Some lizards that are critically endangered include Campbell's alligator lizard, St. Croix Ameiva, Frost's arboreal alligator lizard, Be’er Sheva fringe-fingered lizardand the Doumergue's fringe-fingered lizard.

Other facts

Frill neck lizards have a large, round collar of skin that pops up when they are trying to intimidate attackers.

The green basilisk lizard can run on water at about 5 feet (1.5 m) per second for 15 feet (4.5 m), or more according to National Geographic. Their special feet give them more surface area to hold them up and as they run, they create air bubbles that keep them afloat.

Chameleons' tongues are longer than their bodies, and their eyes can look in two different directions at once.

You can shine a light in a banded gecko's ear and the light will come out the other side, according to the American Museum of Natural History.

Two species — the Mexican beaded lizard of western Mexico and the Gila monster of the southwestern United States and northwestern Mexico, are venomous, according to Encyclopedia Britannica.

Additional resources