Venoms function primarily for prey capture. All snakes are carnivorous, and must subdue living animals for food. Therefore, they have evolved three methods of catching and subduing their food. The snake seizes its prey, grasps it with its teeth and swallows it whole, usually alive. One method of subduing larger prey is through the use of constriction.
Constrictors grasp the prey with their mouths, and throw loops of their body around the prey.
The third important way that snakes subdue prey is through envenomation. Venoms are modified digestive juices, produced in the mouth by modified salivary glands. Venoms contain a cocktail of enzymes that break down cellular structures and interfere with critical functions such as circulation, ventilation and the transmission of nervous impulses. Envenomated prey usually expire by the combined simultaneous failure of several life-supporting systems.