Story Behind the Science
Lizard history can be traced back 200 million years. Their appearance is commonly associated with dinosaurs, which technically are not considered reptiles. Dinosaurs were most likely warm-blooded creatures and are thought to have evolved into birds. Lizards and other reptiles, however, are cold-blooded animals (also known as ectotherms).
Reptiles are a very diverse family and can be separated into four groups: turtles and tortoises, lizards and snakes, crocodiles and alligators and the tuatara. The tuatara group can be traced back to ancient reptiles. Lizards, like many other reptiles, have dry, scaly skin that doesn’t grow with their bodies. As a result, they “molt,” or shed, their skin as they grow. Lizards tend to molt in flakes, whereas snakes shed their skin in a single piece.
One in five reptiles is threatened with extinction, and more than two dozen lizards are considered endangered. Many more of these animals are classified as vulnerable. The greatest threat to lizards and reptiles is habitat loss and destruction as a result of forests being cut down, wetlands being drained and oil spills, among other dangers. Also, the pet and souvenir trade has resulted in many lizards and reptiles being captured and sold for their skins, which can be used to make wallets, handbags and other fashion products.
Other than threats as a result of human productivity, lizards and other reptiles face many natural predators like larger reptiles, carnivorous mammals, birds of prey and many more. Lizards have developed several methods of defending themselves if attacked by a predator. The most common method is running away, though some lizards stay still or play dead. Some predators may be deterred from attacking if they think their prey is already dead. Many lizards have the ability to camouflage and blend in with their surroundings.
One very unique method of self-defense for lizards is breaking off their tails. Some species, like the glass lizards, geckos and skinks, have very fragile tails that are easily broken. Once the tail breaks off, it wriggles around for a short period of time, hopefully long enough to distract the predator from its fleeing lizard prey. These lizards can then re-grow their tails, which may grow back shorter and thicker.
Did You Know?
- Lizards can communicate with one another by bobbing their heads.Learn More »
- Komodo dragons are the largest species of lizard that live on land.Learn More »
- Lizards smell with their tongues. They flick out their tongues, much like snakes do, to detect scents.Learn More »
- Snakes don’t have eyelids. They can’t close their eyes, not even while they’re sleeping.Learn More »
- Snakes may look slimy, but their skin is actually dry, smooth and shiny. Their scales are made up of keratin, similar to human fingernails.Learn More »
- Some turtles and tortoises can live to be more than 100 years old.Learn More »
|Compare & Contrast||Lizards||Reptiles|
|How many species?||Over 4,675||8,240|
|Where do they occur?||Lizards can be found on every continent except Antarctica, in all but the most extreme cold temperatures or in deep oceans. Most live on the ground, though some make their homes in trees, burrows or water.||Worldwide except Antarctica and in all habitats besides tundra and polar ice|
|What do they eat?||Most lizards eat insects, spiders, scorpions or plants, but others eat smaller mammals, birds, amphibians and other reptiles.||The majority of reptiles are carnivores that eat whole prey or insects, but some are herbivores, which eat plants. Larger reptiles like crocodiles can eat fish, turtles, pigs, monkeys, deer and even buffalo.|
|Do they have predators?||Some common predators of lizards include birds of prey, snakes and carnivorous mammals.||Reptiles have many predators, some of which include larger birds, mammals and reptiles. Predators vary depending on size. For example, some baby turtles are commonly eaten by coyotes, wild dogs, ravens and gila monsters.|