The poison of rattlesnakes is used to catch prey, and to protect the snakes. Some people think rattlesnakes go around biting everything in sight, just to be "mean." But this is not true. They only use their posion to catch their food-----or when they feel they are in danger.
Rattlesnake poison is called venom. The venom is made in special glands inside a rattler's head, and it is injected into prey through hollow fangs. The snakes can control the amount of enom that they put into prey. They usually inject just enough venom to kill the prey quickly.