Lizard facts for kids
Quick facts for kids Lizards
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| Clockwise from top left: veiled chameleon (Chamaeleo calyptratus), rock monitor (Varanus albigularis), common blue-tongued skink (Tiliqua scincoides), Italian wall lizard (Podarcis sicula), giant leaf-tailed gecko (Uroplatus fimbriatus), and legless lizard (Anelytropsis papillosus) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | Lepidosauria |
| Order: | Squamata |
| Groups included | |
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| Range of the lizards, all species. | |
| Cladistically included but traditionally excluded taxa | |
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| Synonyms | |
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Sauria Macartney, 1802 |
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A lizard is a type of reptile that belongs to a large group called squamates. This group includes all squamates except snakes and amphisbaenians. There are over 7,000 different kinds of lizards! They live on every continent except Antarctica and on many oceanic island chains.
The term "lizard" describes a group that is not a true family in biology (it's called paraphyletic). This means some lizards are actually more closely related to snakes than they are to other lizards. Lizards come in many sizes. Some chameleons and geckos are only a few centimeters long. The biggest lizard is the Komodo dragon, which can be 3 meters (about 10 feet) long!
Most lizards have four legs and move with a strong side-to-side wiggle. Some lizards, called "legless lizards," have lost their legs over time and look like snakes. A few lizards, like the Draco from forests, can even glide through the air. Lizards often protect their territory. Males might fight other males and use bright colors to attract mates or scare off rivals. Most lizards eat meat. Many smaller species are sit-and-wait predators that eat insects. The Komodo dragon can eat large mammals like water buffalo.
Lizards have many ways to protect themselves from predators. These include venom, camouflage, reflex bleeding, and the amazing ability to drop and regrow their tails.
Contents
Lizard Anatomy
Size: From Tiny to Giant
Lizards come in a huge range of sizes. The smallest are only a few centimeters long. Examples include chameleons like Brookesia micra and geckos like Sphaerodactylus ariasae. The largest living lizard is the Komodo dragon. It can grow to almost 3 meters (10 feet) long. Most lizards are quite small animals.
What Makes a Lizard Unique?
Lizards usually have round bodies, heads on short necks, four legs, and long tails. However, some species are legless. Lizards and snakes both have a special movable bone in their jaw called a quadrate bone. This helps them open their mouths very wide. This bone is different from the more rigid skulls of rhynchocephalians (like the tuatara). Some lizards, like chameleons, have prehensile tails. These tails can grip branches, helping them climb.
Like other reptiles, lizards have skin covered in overlapping scales. These scales are made of keratin, which is the same material as your fingernails. This tough skin protects them and helps them save water. This is why lizards can live in very dry deserts. Lizards shed their skin as they grow. Unlike snakes, which shed their skin in one piece, lizards shed theirs in several pieces. Their scales can also be spiky for display or protection. Some lizards even have bone plates called osteoderms under their scales.
Lizards have different kinds of teeth depending on what they eat. Their diets can include meat, insects, plants, nectar, or snails. Most species have teeth that are all similar and suited to their diet. But some have different teeth, like sharp cutting teeth in the front and crushing teeth in the back. Most lizards have teeth attached to the side of their jawbone (pleurodont). However, agamids and chameleons have teeth attached to the top of their jawbone (acrodont).
A lizard's tongue can stick out of its mouth and is often long. In some lizards, like monitor lizards, the tongue is forked. They use it to sense their surroundings. They flick it out to pick up tiny particles from the air. Then they bring it back to a special organ inside their mouth that helps them "smell" or "taste" their environment. Geckos use their tongues to clean their eyes because they don't have eyelids. Chameleons have very long, sticky tongues that shoot out quickly to catch insects.
Three types of lizards—geckos, anoles, and chameleons—have special pads under their toes. These pads help them stick to surfaces. The pads have millions of tiny hair-like structures called setae. These setae create a strong grip using a special force called van der Waals force. No sticky liquid is needed! Chameleons also have toes that are split into two groups on each foot. This helps them grip branches like birds.
How Lizards Function
Movement and Locomotion
Most lizards have four legs and move by wiggling their bodies from side to side. This body bending makes it hard for them to breathe well while running fast. This limits how long they can run. This is known as Carrier's constraint. Some lizards can run on two legs. A few can even stand on their hind legs and tail when they are still.
Several small lizards, like those in the Draco group, can glide. Some can glide as far as 60 meters (about 200 feet), losing only 10 meters (about 33 feet) in height. Some species, like geckos and chameleons, can stick to vertical surfaces, including glass and ceilings. The common basilisk lizard can even run across water!
Lizard Senses
Lizards use their senses of sight, touch, olfaction (smell), and hearing just like other vertebrates. How much they rely on each sense depends on where they live. For example, skinks that live mostly underground use smell and touch a lot. Geckos rely on their sharp vision to hunt and judge distances. Monitor lizards have excellent vision, hearing, and smell.
Some lizards use their senses in unusual ways. Chameleons can move their eyes in different directions at the same time. This means one eye can look forward while the other looks backward! Lizards don't have outer ears like humans. Instead, they have a round opening where you can see their eardrum. Many lizards use their hearing to detect predators early and quickly run away.
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Like snakes and many mammals, all lizards have a special smelling organ called the vomeronasal organ. They use it to detect pheromones, which are chemical signals. Monitor lizards touch their tongue to this organ to "smell" their surroundings. Their tongue is only for gathering information, not for eating.
Some lizards, especially iguanas, have a light-sensing organ on top of their heads called the parietal eye. This is a very old feature in reptiles, also found in the tuatara. This "eye" can't form images, but it can sense changes in light and dark and detect movement. This helps them spot predators coming from above.
Lizard Venom
Until 2006, people thought only the Gila monster and the Mexican beaded lizard were venomous. But now we know that several types of monitor lizards, including the Komodo dragon, also produce strong venom in their mouth glands. For example, lace monitor venom can make an animal lose consciousness quickly and cause a lot of bleeding. This is because it lowers blood pressure and stops blood clotting. Lizards produce nine types of toxins that are also found in snakes. These toxins could be used to create new medicines.
Scientists have found genes linked to venom toxins in the saliva glands of many lizards. This includes species that were thought to be non-venomous, like iguanas and bearded dragons. This suggests that these venom genes might have first appeared in the common ancestor of lizards and snakes about 200 million years ago. This group is called the Toxicofera. However, many of these genes are "housekeeping genes" found in all cells. So, they might just be early versions of venom genes.
Breathing
Recent studies (from 2013 and 2014) on the lungs of the savannah monitor and green iguana found something amazing. They have a special breathing system where air moves in a loop through their lungs. This was thought to only happen in archosaurs (like crocodilians and birds). This discovery might mean that this type of breathing is a very old trait in diapsids (a group of reptiles that includes lizards, snakes, crocodiles, and birds).
Lizard Reproduction and Life Cycle
Most lizard species are egg-laying. The female lays her eggs in a safe place, like a nest, a crack, or simply on the ground. The number of eggs can vary a lot. Some females lay just a few large eggs, while others lay dozens of small ones. The total weight of the eggs can be anywhere from 4-5% to 40-50% of the female's body weight.
Most lizard eggs have leathery shells that allow water to pass through. However, species living in dry areas have harder, calcified shells to keep water inside. Inside the eggs, the baby lizards get their food from the yolk. Parents usually don't care for their eggs or young. The female often leaves the eggs after laying them. But some species do protect their eggs. For example, the female prairie skink keeps her eggs moist by breathing on them. This helps the babies grow. In lace monitors, the young hatch after about 300 days. The mother returns to help them get out of the termite mound where the eggs were laid.
About 20% of lizard species give viviparity (live birth). This is common in Anguimorphs. These species give birth to babies that look like tiny adults. The embryos get food from a structure similar to a placenta. A small number of lizards can reproduce without a male. This is called parthenogenesis (reproduction from unfertilized eggs). These species are all female and reproduce by themselves. This happens in several types of whiptail lizards. Parthenogenesis has also been seen in species that usually reproduce sexually. For example, a female Komodo dragon in captivity laid eggs even though she hadn't been near a male for over two years.
The sex of baby lizards can sometimes be decided by temperature. This is called temperature-dependent sex determination. Lower temperatures during egg incubation often produce more females, while higher temperatures produce more males. However, some lizards have sex chromosomes (like humans). Both male (XY and XXY) and female (ZW) sex chromosomes can be found in lizards.
Aging in Lizards
As the painted dragon lizard Ctenophorus pictus gets older, its bright breeding colors fade. Scientists have studied this. They found that this fading is likely due to a gradual loss of the lizard's natural ability to fight damage in its body as it ages. This damage is often linked to DNA damage.
Lizard Behavior
Daily Life and Body Temperature
Most lizards are active during the day. However, some, especially geckos, are active at night. Lizards are ectotherms. This means they can't make their own body heat. They need to warm up by basking in the sun to become fully active. Being able to control their body temperature helps lizards deal with changes in the environment and even climate warming.
At high altitudes, the Podarcis hispaniscus lizard has darker skin on its back. This helps it absorb more heat and protects it from strong UV radiation. Their ability to control their body temperature also helps them stay at the perfect temperature for moving around easily.
Protecting Their Territory
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Most social interactions among lizards happen between lizards that are ready to breed. Protecting a territory is common, especially for lizards that wait for prey (sit-and-wait hunters). Male lizards set up and protect areas that have resources like good basking spots, food, nesting sites, and safe places to hide from predators. They defend these areas from other males. The type of place a lizard lives affects how its territory is set up. For example, rock lizards have territories on top of rocky areas. Some species might gather in groups. This helps them watch out for danger and reduces the risk of being caught by a predator, especially for young lizards. Fights between males often happen over territory or mates. These fights can include displays, special body poses, push-ups, chasing, grappling, and biting.
How Lizards Communicate
Lizards use signals to attract mates and to scare away rivals. They use visual displays like body postures, puffing themselves up, doing push-ups, showing bright colors, opening their mouths wide, and wagging their tails. Male anoles and iguanas have dewlaps. These are flaps of skin under their throats that come in different sizes, colors, and patterns. Expanding the dewlap, along with head-bobs and body movements, adds to their visual signals. Some lizards have deep blue dewlaps and use ultraviolet signals that humans can't see. Blue-tongued skinks will flash their blue tongues to threaten others. Chameleons are famous for changing their complex color patterns when they communicate. They show brighter colors when they are aggressive and darker colors when they give up.
Several gecko species have bright colors. Some will tilt their bodies to show off their colors. In some species, brightly colored males become dull when no rivals or females are around. While males usually display, females in some species also communicate this way. In the bronze anole, females often use head-bobs to communicate. The speed and frequency of these bobs change with their age and territory status. Chemical signals called pheromones are also important. Males usually send signals to rivals, while females send them to potential mates. Lizards can often recognize other lizards of the same species by their scent.
Lizards don't use sounds as much as other animals. Hissing, a common reptile sound, is mostly made by larger lizards as a threat, often with an open mouth. Some groups, especially geckos, snake-lizards, and some iguanids, can make more complex sounds. They have developed special body parts for making sounds independently. These sounds are used for finding mates, defending territory, and when they are in danger. They include clicks, squeaks, barks, and growls. The male tokay gecko's mating call sounds like "tokay-tokay!". Tactile communication involves lizards rubbing against each other, either during courtship or in a fight. Some chameleon species communicate by vibrating the surface they are standing on, like a tree branch or leaf.
Lizard Ecology
Where Lizards Live
Lizards are found all over the world, except in the far north and Antarctica, and some islands. They can live from sea level up to 5,000 meters (about 16,400 feet) high. They prefer warm, tropical climates but can adapt to almost any environment. Lizards live in many different places. Most live on the ground, but others live in rocks, on trees, underground, and even in water. The marine iguana is specially adapted to live in the sea.
What Lizards Eat
Most lizard species are predators. They mainly eat small, ground-dwelling invertebrates, especially insects. Many lizards are sit-and-wait predators. They wait patiently for prey to come by. Others are more active hunters. Chameleons eat many types of insects, like beetles, grasshoppers, and winged termites, as well as spiders. They catch prey by being very still and then ambushing them. A chameleon will sit on a branch, perfectly still, with only its eyes moving. When an insect lands, the chameleon focuses its eyes, moves slowly towards it, and then shoots out its long, sticky tongue to grab the prey. Geckos eat crickets, beetles, termites, and moths.
Termites are an important food source for some lizards. Since termites are social insects, they can be found in large numbers in one spot. Ants are a major part of the diet for some lizards, especially lacertas and Horned lizards. Because ants are small and have hard shells, ant-eating lizards need to eat a lot of them. These lizards have larger stomachs than even plant-eating lizards. Some species of skink and alligator lizards eat snails. Their strong jaws and molar-like teeth are perfect for breaking snail shells.
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Larger lizards, like monitor lizards, can eat bigger prey. This includes fish, frogs, birds, mammals, and other reptiles. They might swallow prey whole or tear it into smaller pieces. They also eat bird and reptile eggs. Gila monsters and beaded lizards climb trees to find eggs and young birds. Even though they are venomous, these lizards use their strong jaws to kill prey. Mammals they eat usually include rodents and rabbits. The Komodo dragon can even kill prey as big as a water buffalo. Komodo dragons are also great scavengers. A single dead animal can attract several dragons from 2 kilometers (about 1.2 miles) away. A 50 kg (110 lb) dragon can eat a 31 kg (68 lb) carcass in just 17 minutes!
About 2% of lizard species are herbivores, meaning they eat plants. This includes many iguanids. Adult plant-eating lizards eat flowers, leaves, stems, and fruit. Young lizards of these species eat more insects. Plant parts can be hard to digest. As young iguanas grow, they eat poop from adult iguanas. This helps them get the right microbes in their gut to digest plants. Perhaps the most plant-eating lizard is the marine iguana. It dives 15 meters (about 50 feet) underwater to find algae, kelp, and other marine plants. Some lizards that mainly eat insects also eat fruit, which is easy for them to digest.
How Lizards Avoid Predators
Lizards have many ways to protect themselves from predators. These include running, climbing, using venom, camouflage, dropping their tails, and reflex bleeding.
Camouflage
Lizards use different camouflage methods to blend in. Many lizards have patterns that break up their outline, making them harder to see. In some species, like Aegean wall lizards, individuals have different colors. They choose rocks that best match their own color to hide from predators. The Moorish gecko can change color to blend in. If a light-colored gecko is placed on a dark surface, it will darken within an hour to match. Chameleons usually change colors for communication, not camouflage. But some species, like Smith's dwarf chameleon, do use active color change to hide. The flat-tail horned lizard's body is colored like its desert home. It is also flat and has white scales along its edges to make its shadow as small as possible.
Tail Dropping (Autotomy)
Many lizards, including geckos and skinks, can drop their tails. This is called autotomy. The detached tail, which is sometimes brightly colored, keeps wiggling after it falls off. This distracts the predator while the lizard escapes. Lizards can partially regrow their tails over several weeks. About 326 genes are involved in regrowing lizard tails. The fish-scale gecko Geckolepis megalepis can even shed patches of its skin and scales if it's grabbed!
Escape, Playing Dead, and Reflex Bleeding
Many lizards try to escape danger by running to a safe place. For example, wall lizards can run up walls and hide in holes or cracks. Horned lizards use different defenses for different predators. They might play dead to trick a predator that has caught them. They might try to outrun a rattlesnake, which doesn't chase prey. But they will stay still, relying on their camouflage, if a Masticophis whip snake is around, as these snakes can catch fast prey. If caught, some lizards, like the greater short-horned lizard, puff themselves up. This makes them hard for a narrow-mouthed predator like a whip snake to swallow. Finally, horned lizards can squirt blood from a pouch under their eyes at cat and dog predators. The blood can shoot about 2 meters (6.5 feet) and tastes bad to these attackers.
Lizard Evolution
Ancient Lizards: Fossil History
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The closest living relatives of lizards are rhynchocephalians. This was once a large group of reptiles, but now only one species remains: the tuatara of New Zealand. Some reptiles from the Early and Middle Triassic period, like Sophineta and Megachirella, might be early ancestors of squamates (lizards and snakes). They might be more closely related to modern lizards than rhynchocephalians are. However, scientists are still debating this. The oldest lizards that everyone agrees on are from the Middle Jurassic period. Their remains have been found in Europe, Asia, and North Africa. Lizards became much more diverse in their shapes and ways of life during the Cretaceous period.
Mosasaurs were giant marine reptiles. They likely evolved from an extinct group of water lizards called aigialosaurs in the Early Cretaceous. Dolichosauridae is a family of Late Cretaceous water lizards that were closely related to mosasaurs.
Lizards and Humans
How Humans Interact with Lizards
Most lizard species are not harmful to humans. Only the largest lizard, the Komodo dragon, which can be 3.3 meters (10.8 feet) long and weigh up to 166 kg (366 lb), has been known to stalk, attack, and sometimes kill humans. For example, an eight-year-old Indonesian boy died from blood loss after an attack in 2007.
Many types of lizards are kept as pets. These include bearded dragons, iguanas, anoles, and geckos (like the popular leopard gecko). Monitor lizards such as the savannah monitor and tegus like the Argentine tegu and red tegu are also popular pets.
Green iguanas are eaten in Central America. They are sometimes called "chicken of the tree" because they rest in trees and are said to taste like chicken. Spiny-tailed lizards are eaten in Africa. In North Africa, Uromastyx species are called dhaab or 'fish of the desert' and are eaten by nomadic tribes.
Lizards like the Gila monster produce toxins that can be used in medicine. Gila toxin helps lower blood sugar. This substance is now made in labs for use in a medicine called exenatide (Byetta), which treats diabetes. Another toxin from Gila monster saliva has been studied for use as a drug to treat Alzheimer's disease.
Lizards in Culture
Lizards appear in myths and folktales all over the world. In Australian Aboriginal mythology, Tarrotarro, the lizard god, separated humans into male and female. He also gave people the ability to create art. A lizard king named Mo'o is found in stories from Hawaii and other parts of Polynesia. In the Amazon, the lizard is seen as the king of animals. Among the Bantu people of Africa, the god UNkulunkulu sent a chameleon to tell humans they would live forever. But the chameleon was slow, and another lizard brought a different message: that human life is limited. A popular story in Maharashtra tells how a common Indian monitor lizard, with ropes attached, was used to climb the walls of a fort during the Battle of Sinhagad. In the Bhojpuri-speaking regions of India and Nepal, children believe that touching a skink's tail three (or five) times with their shortest finger brings money.
In many cultures, lizards share symbols with snakes, especially as a sign of new life or resurrection. This might be because they regularly shed their skin. The image of lizards on Christian candle holders probably refers to this same idea. According to Jack Tresidder, in ancient Egypt and the Classical world, lizards were seen as good symbols, linked with wisdom. In African, Aboriginal, and Melanesian folklore, they are connected to cultural heroes or ancestors.
See also
In Spanish: Lacertilia para niños
