San Diego Management & Monitoring Program

Red Diamond Rattlesnake
Crotalus ruber


Animalia Chordata Reptilia Squamata Viperidae
Kingdom Phylum Subphylum Class Order Suborder Family

Current distribution rangewide

Ranges from near Pioneertown and Morongo valley of San Bernadino County and southeastern Los Angeles County south through Baja California, including several islands in the Gulf of California such as Angel de la Guarda, Pond, San Marcos, Danzante, Moserrate, and San Jose islands [1;2]. Elevational range extends from near sea level to about 1500 m but usually below 1200 m [1;3].

Known Populations in San Diego County

Within Conserved Lands, occurrences have been found in MU 3 (Marron Valley Mitigation Bank, Otay Ranch Preserve, Mount Miguel Open Space, near Boulder Creek in Cleveland National Forest), MU 4 (Sycamore Canyon and Goodan Ranch), and MU 10 (Cleveland National Forest).

List status


Habitat affinities

Occupies habitats with heavy brush associated with large rocks or boulders [1]. Cacti are important habitat features as well as rocks [4]. Frequently observed in chamise- and red shank-dominated associations. Preference for coastal sage scrub, rocky hillsides, and desert slope scrub [3]. Occupies a wide array of habitats including desert slopes, rocky canyons, and coastal foothills [2].

Taxonomy and genetics

Three subspecies used as pattern classes: C. r. exsul, C. r. lucasensis (San Lucan diamond), and C. r. ruber [2]. C. r. ruber forms a natural taxonomic group with C. lorenzoensis of isla San lorenzo and C. catalinensis on Isla Santa Catalina [2;5].

Seasonal activity

Typically emerge from over-winter locations in late February [4]. Active from spring to fall, but peak activity is from March to June [1;6, cited in 7]. Generally diurnal during the spring and nocturnal during warmer months [2].

Life history/ reproduction

Courtship and copulation seen April to May [1;4;6, cited in 7]. Gestational denning in June to September, and all recorded births in September [4]. Young are live born from mid-August to October. Litters range from 5 to 13, with an average of 8 young [1;6, cited in 7]. Longevity in wild is unknown though a snake was observed to have lived over 14 years in captivity [8, cited in 3].

Diet and foraging

Feeds on small mammals such as rabbits, ground squirrels, pocketmice, wood rats, lizards, and occasionally birds [1;6, cited in 7;9]. Capture prey by either waiting for prey or actively searching ground, rocky areas, and off the ground in bushes [7].


Relative restricted movement, never occurring more than 300 m linear distance from their winter dens [4].


Habitat loss due to urban and agricultural development [3;4;10] especially affecting the coastal populations in California [4;11, cited in 9].

Red Diamond Rattlesnake sources