Black diamond rattlesnake, Black (diamond) rattler, Gray diamond-back, Mountain rattler, Pacific rattler, San Diegan rattler
The Southern Pacific rattlesnake (Crotalus helleri) is a pit viper species or subspecies that is known for its regional variety of dangerous venom types. It is sometimes considered a subspecies of the Northern Pacific rattlesnake (Crotalus oreganus).
The color pattern of this snake consists of a pale brown, gray-brown, or yellowish brown ground color overlaid with a series of large, dark brown dorsal blotches that may or may not have pale centers. The blotches are more diamond shaped and are bordered by light scales. The tail rings are not clearly defined. In juveniles, the end of the tail is bright orange, but this turns brown as the snakes mature. In adults, the base of the tail and the first segment of the rattle are brown. The postocular stripe is moderate to very clearly defined. In juveniles, this stripe is bordered above by a pale stripe, but as the snakes mature this turns to drab yellow or brown. A conspicuous pale crossbar is sometimes present across the supraoculars, after which the head is a uniform dark color. In some older snakes, the head is mostly dark with almost no trace of the supraorbital crossbar, or none at all.
Southern Pacific rattlesnakes are found in the United States in southern California, and in Mexico in northern Baja California, west of the desert. In they occur from the counties of San Luis Obispo and Kern, and south through the counties of Santa Barbara, Ventura, Los Angeles (including Santa Catalina Island and the foothills.), southwestern San Bernardino, Orange, western Riverside, San Diego, and extreme western Imperial. From there their range extends south through Baja California. These rattlesnakes try to avoid very arid areas and usually inhabit mountain forests, rocky areas, hillsides, canyons, chaparral, shrubby coastal dunes, grasslands, and agricultural areas.
Southern Pacific rattlesnakes spend most of their time on the ground but may sometimes climb in trees or shrubs. They hunt by night using their heat-sensing organs to locate prey. During cold months of the year, they typically hibernate in caves, abandoned mammal burrows, or crevices. Southern Pacific rattlesnakes are generally solitary creatures but females may gather in groups near their hibernation sites.
Some populations of the Southern Pacific rattlesnake have a neurotoxic venom that is very similar to the extremely dangerous Mojave rattlesnake (the "Mojave Green") toxin in the way it attacks the nervous system. Other populations can have hemotoxic and myotoxic venom that is more typical among rattlesnakes and though less dangerous, can also can give a fatal bite. In a survey of various populations of Crotalus in California, every sampled specimen with disabling neurotoxic venom had originated near Idyllwild, California, in the San Jacinto Mountains. Scientists considered the intraspecific variety of venom types "medically significant" while hypothesizing that evolutionary pressures, driven by regional habitat differences and the associated challenges of hunting prey in each, could have been behind the variation of venom types in Southern Pacific rattlesnake, and that cross-breeding with the Mojave rattlesnake, which is geographically separated from neurotoxic Crotalus populations, was unlikely.
Southern Pacific rattlesnakes are carnivores and prey on small mammals, reptiles, amphibians, birds and their eggs.
Southern Pacific rattlesnakes breed in spring right after hibernation. Females are ovoviviparous. And after abouth 3 months after mating they give birth to 9-10 live, well-developed snakelets. They are born with fangs and can defend themselves and hunt prey. They are independent right after birth and don’t require parental care.
Southern Pacific rattlesnakes are not considered threatened at present but they suffer from habitat loss and are often persecuted by humans.
Presently, the Southern Pacific rattlesnake is not included in the IUCN Red List and its conservation status has not been evaluated.
