NNTRC Snakes

Scientific Name

Crotalus oreganus helleri

Common Name 

Northern Pacific Rattlesnake

Physical Characteristics

Length, 24-48 in. (60-120 cm). Dark brown or black ground color. Along the back are darker somewhat oval blotches that are bordered by a lighter cream color.

Geographic Range (USA, México)

Western half of Southern California southward through Baja California del Norte to the northern edge of Baja California del Sur.

Map button button

Desert scrub and rocky outcrops.


Rats, mice, and small rodents.


Hemorrhagic toxins, resulting in tissue damage and edema. However, neurotoxins are present in some populations causing paralysis of the muscles of swallowing and respiration.


Once considered a subspecies of the Crotalus viridis complex. Recent molecular analysis suggests it is a separate species and Douglas et al. (2003) has elevated it to full species status. The Southern Pacific Rattlesnake can be aggressive and will usually stand its ground when encountered.

This page was last updated on: February 12, 2016