Man and animal possess many tools for communication. Eyes, ears, nose can be all used. Visual communication is useful when the distance between animals is small. Many animals produce sounds, some of them modulated by vocal cords. Sounds may be carried far in air and water. Scent spores produced by glands can persist for long period of time.

Communication in all its forms is important to survive: a warning for other species or individuals from the same sex. In order to be able to recognize individuals from the other sex in the light of reproduction.

Many reptiles produce sounds that humans do not recognize as speech. Snakes and chelonians do not have an outer ear, they do not hear the sounds as we do, but feel vibrations in their surroundings. Crocodilians are very vocal. The males will roar in the reproductive season, the young will make a variety of sounds to attract their mothers. When in danger they produce panic sounds.

Almost all snakes and many lizards use their tongue to analyze the scent of the environment through their Jacobson's organ.

An interesting phenomenon is the ability of color changes in chameleons. The skin is covered with a transparent layer. Below this are two well demarcated layers of red and yellow pigment containing chromatophore cells. Iridophores are found in a layer under the chromatophores, and are responsible for the metallic looking greens, blues and gold colors seen in some species as well the silver coloration. In the basis of the epidermis melanin containing cells are present. To change the color of the skin the chromatophore either shrink or expand, thus expressing different colors. A stressed chameleon will send the melanin to the surface and renders the skin darker.

Different species of chameleons possess different basal colors. The layers of the skin are hormonally influenced. In male chameleons when another male needs to be impressed or a female to be attracted it will express its most vivid colors.

Other lizards may exhibit some color changes (e.g., blackening of the lower jaw and throat in bearded dragons). Males [sic] to impress other males or in time of stress. Male iguanas will express an orange color in the reproductive season.

Many owners of pet reptiles think they communicate with the animals. Many reptiles are so used to their caretakers that they don't stress anymore, a snake that keeps his normal curled up posture when the owner opens the enclosure.

When people keep these kinds of animals it is of course very important to be able to recognize the communicative behavior of the species they have.

Normally when possible a frightened reptile will try to escape.

A stressed chameleon will show more dark colors. An angry, stressed bearded dragon will show a black beard. Iguanas that are forced into a stressed state will show off defensive behavior. The animal will make itself as big as possible, extend its dewlap, and lift its tail. When another iguana or the humans don't understand this communication meaning get out of my way and grasp the animal a next step in defense it provoked. The animal will bite, whack with his tail, scratch and rotate its body along the length axis to try to escape.

Monitor lizards may hiss when they are provoked. When this is not understood they will bite.

Many snake species may show different signs of communication. It is easily recognized in rattlesnakes. When approached they will vigorously rattle their tail that is composed of segments of keratin that fit loosely inside one another. They keep their body in a curled up position with the mouth and thus fangs ready to strike. Some species of non-venomous snake mimic these sounds. Snakes are also capable of making hissing sounds.

The grass snake (Natrix natrix) doesn't have very many weapons to defend itself. When attacked, and a veterinarian catching an animal from the enclosure is experienced as danger by the animal, it will act like it is dead. It rolls on its back and lets some red-stained fluid coming out of the mouth.

Many snakes will empty their cloaca and cloacal sacs when in panic.

Chelonians predominantly will pull themselves back in the shell protecting their softer parts. But a number of species are not that shy and will start biting when handled.

Veterinarians treating the reptiles should recognize the species brought in and have a thorough knowledge of the normal behavior of these animals.