This large-sized rattlesnake can be found from central California up to southwestern Canada. They occur in grasslands and forests favoring drier habitats; but are still absent from fully arid deserts.

The northern Pacific rattlesnake has a diet consisting primarily of mammals and birds as adults and lizards, shrews, and newborn rodents as juveniles. The mean litter size of this rattlesnake is 5.5 with larger females having more babies born at a time.

Because of the shift from smaller, "longer" prey as juveniles to larger, more robust prey as adults, the venom of the northern Pacific rattlesnake changes too! The venom of a juvenile is more toxic than that of an adult, and the venom of an adult rattlesnake here causes more hemorrhaging. However, it's important to know that juvenile rattlesnakes can control the output of their venom.

C. o. oreganus is one of the larger subspecies, reaching up to 64in (162.6cm). In terms of coloration, they tend to be light tan or brown with dark brown spots and have dark brown on top of their head. Their dark head is an especially good characteristic to distinguish them from other rattlesnakes nearby.

This species is threatened by road mortality, and human persecution--including destruction of their communal den sites they use to safely overwinter.