Southern Pacific Rattlesnake

The southern Pacific rattlesnake is a thick-bodied pit viper species known for its dangerous venom. It is also one of the largest rattlesnakes. The specific name, helleri, is in recognition of American zoologist Edmund Heller. Its venom varies substantially between populations, depending on their habitats.

Scientific Classifications

  • Suborder:Serpentes
  • Family:Viperidae
  • Genus:Crotalus
  • Species:C. helleri

Conservation Status

Not EvaluatedNE

Not Evaluated

Data DeficientDD

Data Deficient

Least ConcernLC

Least Concern

Near ThreatenedNT

Near Threatened





Critically EndangeredCR

Critically Endangered

Extinct in the wildEW

Extinct in the wild




Southern Pacific Rattlesnake Photo


The adults are 24-55 in (61-139 cm) long.

Color and Appearance

The ground color is gray-brown, pale brown, or yellowish-brown, with a series of big, dark-brown dorsal blotches that may or may not have pale centers. The markings are more diamond-shaped as opposed to the northern Pacific rattlesnake’s more hexagonal ones. They are bordered with light scales. The tail rings are not prominent. The tail’s base and the rattle’s first segment are brown. The postocular stripe is moderately to very clearly defined.

Juvenile Southern Pacific Rattlesnake

The juveniles have bright orange tail ends that change into brown as the snakes mature. Their postocular stripe has a pale stripe above it that turns brown or drab yellow as they mature. Sometimes, a well-defined pale crossbar is present across the supraoculars, after which the head is of a uniformly dark color. In some of the older snakes, the head is mostly dark with no trace of the crossbar.

Are They Dangerous to Humans 

When alarmed, the snake produces its characteristic rattling sound to warn its attacker. If threatened or cornered, it can deliver a strike across a distance of a third to half the length of its body. Some populations of the snake have an extremely dangerous neurotoxic venom, similar to that of the Mojave rattlesnake, in the way it attacks the nervous system. Others have a myotoxic and hemotoxic venom that is more typical of rattlesnakes. Despite being less dangerous, it can lead to fatal bites.

Southern Pacific Rattlesnakes at a Glance

Southern Pacific Rattlesnake Range


It range includes southwestern California extending south into Baja California, Mexico.


It can be found in various areas, including mountain forests, grasslands, agricultural fields, coastal dunes, rocky deserts, and hillsides. In the northern end of their range, they hibernate in ledges and rock crevices.


Predation, disease, and accidents limit its lifespan to only a few years. In protected environments, however, it can live for 10-20 years.

Crotalus helleri


It is preyed upon by coyotes, roadrunners, and birds of prey.


The nocturnal hunter eats birds, insects, frogs, lizards, other snakes, and small mammals, including rats, mice, rabbits, ground squirrels, and hares.


Southern Pacific Rattlesnake Baby

Ovoviviparous (gives birth to live young from eggs that hatch inside the body)

Around 90 days after mating in spring, the well-developed young are born in groups of 4-12. They are 7-10 inches long and dangerous for their short fangs capable of injecting venom.

Similar Species

Western Diamondback Rattlesnake

The western diamondback rattlesnake, Crotalus atrox, has black and white rings around its tail and is less likely to bite than its southern Pacific cousin.


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