The internal organs of reptiles are similar to those of birds and mammals. In contrast to birds and mammals, reptiles are cold-blooded. They warm or cool themselves by moving to warmer or cooler locations. Most become dormant under cold conditions. The reptile's senses of sight, smell, and hearing are similar to those of other vertebrates, though the levels of development of these senses vary among reptile groups.
Snakes lack ears and can detect only ground vibrations or airborne vibrations of low frequency.
Snakes and lizards have a specialized, chemically sensitive organ, called Jacobson's organ, located in the roof of their mouths. These animals can detect the presence of chemicals in their surroundings by flicking their tongues out and in rapidly, pressing the tongue against the organ with each retraction. Heat-sensitive organs line the lips of some boas and pythons and are also located on the sides of the heads of pit vipers. Thus, because the pit vipers can sense infrared radiation, they can detect and strike their prey even in total darkness. How Snakes Move Locomotion.