Crotalus viridis eat small mammals, ground nesting birds, amphibians, and reptiles, including sometimes other snakes. They locate their prey by using their tongue to sense in airborn chemicals given off by the prey. Then they rapidly strike out at them, biting them with their fangs, then letting them go quickly. Venom is released from their fangs when the snakes strike. It works to immobilize the prey, which the snake then tracks and eats. The venom also works to destroy tissue and help with the digestion of bulkier prey.

Their venom is very deadly. Crotalus viridis use from 20-55% of their stored venom when they bite a small mammal such as a mouse. This is approximately 300 times the amount of venom needed to kill that animal. Venom is stored in glands which are connected to the hollow fangs. Venom is the means used to kill the prey, as the bite of the fangs alone would not usually result in death. The fangs are covered by thin tissue and fold back against the roof of the mouth when the mouth is closed.

During early spring and late fall when the weather is warm, Crotalus viridis hunts during the day. When the weather gets hotter, Crotalus viridis tends to seek shelter during the day and wait until night when it is cooler to hunt. (Greene, 1997; Jacobs, 1999; Kardong et. al., 1998; Kardong, 1996; Melli, 1999; Reptiles and Amphibians of North Dakota, 1999)