Kingsnakes use constriction to kill their prey and tend to be opportunistic in their diet; they eat other snakes (ophiophagy), including venomous snakes. Kingsnakes also eat lizards, rodents, birds, and eggs. The common kingsnake is known to be immune to the venom of other snakes and does eat rattlesnakes, but it is not necessarily immune to the venom of snakes from different localities.

Kingsnakes such as the California kingsnake can exert twice as much constriction force relative to body size as rat snakes and pythons. Scientists believe such strong coils may be an adaptation to snake and other reptile prey, which can sustain lower blood-oxygen levels before asphyxiating

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