Snakes are ectotherms, meaning that a snake regulates its body temperature by taking heat from or giving off heat to the environment. Because their body temperature is affected by environmental temperatures and varies with surrounding conditions, snakes become inactive during very hot seasons (aestivation) and very cold seasons (hibernation). Snakes may go for several weeks without eating because of frequent periods of inactivity.
Because they are cold-blooded, snakes must rely on behavior to regulate their body temperature. During the hot part of the day, snakes move to shaded areas, and on cool days they sun themselves on rocks or in warm open areas. Snakes often seek out paved roads where they are attracted by the heat from the road surface.
Because snakes have backbones, they are classified in the same group (vertebrates) as fish, mammals, birds, and people. The snake's skeletal system is unique. Snake bones are very light and highly movable. The lower jaws and skull are connected by a piece of stretchy material (ligament). This allows the snake to open its mouth very wide and move each jaw independently. Thus, a snake can swallow prey much larger than its head by “walking” its mouth around the food from side to side in a forward movement.
Snakes are very specialized animals. They do not have legs, ears, or eyelids. There are no “walking” snakes. Often the sex organs of a snake may protrude from the anal plate area and are confused with legs.
They use their forked tongues to smell. The tongue is constantly flicking to pick up airborne particles and odors. Once these aromas are detected, the snake inserts its tongue into two holes in the top of its mouth (Jacobson's organ), where the smells are interpreted by its brain. If the snake detects food and it is hungry, it will pursue the animal.
Contrary to popular belief, snakes are not slimy. In fact, they feel dry to the touch. The snake's scales and skin help keep it from losing moisture from its body. Snakes shed their skin and eye covering together.
When threatened, many snakes produce a unique scent from musk glands located near the anus. Copperbelly water snakes smell like skunks, while rat snakes and copperheads smell like cucumbers.
When people encounter a snake, they often corner it. Then the snake will hiss loudly, open its mouth in a threatening manner, coil up, and strike at the individual-or bluff by advancing toward the intruder. These behaviors, designed to scare off the intruder, lead to a common misconception that snakes charge or attack people. In most cases, a snake reacts only if it feels threatened. Usually it crawls away if it can reach cover safely. One exception is the male black racer, which may chase after larger animals, including humans, when it is defending its breeding territory.