Snakes
Snakes are predators found in nearly every habitat on Earth. Their skinny bodies help them hunt in crevices, burrows and nests. Species such as the boa constrictor can also climb trees and swim. Some species such as the western diamondback rattlesnake track prey with heat sensors called pit organs. Snakes such as king cobras kill their prey with their deadly venom while constrictors such as green anacondas crush their prey to death in their giant coils.
Lizards
Like snakes, lizards are found in most parts of the world. They are distinguished from snakes by the presence of ear openings, movable eyelids and less flexible jaws. Most have four limbs but the so-called glass snake and worm lizard are legless. All species of lizards dwell on land, but many are adapted for climbing trees and swimming. The iguanas from the Galapagos Islands are the only marine species of lizard. Some species such as chameleons change colors in different environments. Komodo dragons are the heaviest lizards in the world and can reach 10 feet in length and weigh 200 pounds. They are only found on Komodo, Rinca, Flores, Montang, Gili and Padar islands in Indonesia. Gila monsters and the other beaded lizards of North America are the only poisonous lizards.
Turtles
Turtles are distinguished from other reptiles by their protective shells. Turtle shells take many forms. The bony parts of the shell are covered by either scaly plates or leathery skin. Aquatic species such as the green sea turtle or the common snapping turtle have streamlined shells while land-dwelling species such as the desert tortoise have dome-shaped shells. Turtles lay large numbers of eggs to make up for high infant mortality rates. They eat worms, crustaceans, plants and fish.
Crocodilians
Crocodilians include alligators, caimans, crocodiles and gavials. They are carnivorous with powerful jaws, clawed feet, conical teeth, muscular tails and long bodies covered in heavily armored skin. They are primarily found in tropical and subtropical swamps, lakes and rivers, although some species spend some time in saltwater. They spend most of their time in the water, waiting for prey. Some species include the Mississippi alligator, the Nile crocodile and the saltwater crocodile and the Indian gavial. Mississippi alligators are primarily found in the Southeastern United States. Nile crocodiles are found in swamps, lakes and rivers across much of Africa. Saltwater crocodiles are found in both salty and fresh water in northern Australia, India and Southeast Asia. Although they average about 17 feet, specimens as large as 23 feet are not unknown. Gavials are an extremely rare creature found only in the rivers of India and Nepal.
Tuatara
Tuatara are found only in New Zealand. The the Cook's Strait tuatara and Brother's Island tuatara are the only known representatives of the order Sphenodontia which first appeared about 250 million years ago. They range about 15 to 24 inches in length, have gray, olive or reddish skin, a crest down the head and another down the back. Although they resemble lizards, they have some distinctive features. For example, they have a unique form of hemoglobin, a distinctive pattern of openings in their skulls and their males lack an organ used exclusively for intercourse. Tuatara are primarily nocturnal but will come out during the day for sunlight. They eat insects, lizards, frogs, small tuatara and eggs. They can live for 100 years.