Baja California Rattlesnake

Baja California Rattlesnake, Crotalus enyo

Baja California Rattlesnake, Crotalus enyo. Snake photographed along the shoreline at Bahía Santa Rosalillita, Baja California, September 2015. Photograph courtesy of Barry Mastro, Escondido, California.

Baja California Rattlesnake, Crotalus enyo. Snake photographed within the confines of the Arizona-Sonora Desert Museum, Tucson, Arizona, February, 2022.

The Baja California Rattlesnake, Crotalus enyo, is a member of the Viperidae family of Pit Vipers. The Viperidae family consists of three hundred fifty members placed in three genera. Members of the Viperidae family are venomous and are commonly known as vipers. They are characterized by a head that is distinct from the body and a single pair of long, hollow, venom-injecting fangs that can be folded against the top of the mouth (tipped inward) when their mouth is closed. There are twenty-nine species in the Crotalus genus. The Baja California Rattlesnake is known in Mexico as Serpiente de Cascabel de Baja California.

Baja California Rattlesnakes vary in coloration between tan, pale brown, dark brown, grayish brown, or silvery gray depending on the individual snake. The anterior sides of their body are darker than their posterior sides. They typically have 28 to 42 blotches along their dorsal side that are reddish to yellowish brown with black edges. The blotches near their midbodies are more hexagonal in shape, whereas the blotches near their heads and anterior portions are subrectangular. Their ventral sides are cream in color and can be heavily spotted with gray or brown and they have transverse pale bands across their supraocular scales. Their rattles are made up of 4 to 8 rings of specialized scales. The proximal regions of their rattles are black, while the distal ends of their rattles are light brown in color. The Baja California Rattlesnake can measure up to 89.8 cm (35.4 inches) in length and displays sexual dimorphism with males typically growing larger than females. However, both male and female juveniles range from 20.6 cm (8.1 inches) to 22 cm (8.7 inches) in length. Juveniles are also born with similar coloration to adults. Adults have 23 to 27 rows of dorsal scales on their midbodies while the number of central and subcaudal scales differs between the sexes. Males typically possess 159 to 168 ventral scales and 22 to 28 subcaudal scales whereas females possess 161 to 177 ventral scales and 18 to 23 subcaudal scales.

Baja California Rattlesnakes have a polygynous mating system and they identify potential mates by releasing and detecting sex-specific pheromones. Male snakes compete aggressively with other males for access to females, however this competition is non-violent. Competitive behaviors include hissing and aggressive posturing. Baja California Rattlesnakes mate every other year with a breeding season in early spring. Females are ovoviviparous, which means the eggs hatch internally and females give birth to live young. Gestation periods are two to five months and clutch size ranges between two and nine, with larger females producing larger clutches. Newborn Baja California Rattlesnakes are precocial and reach maturity at different times depending on their sex. Females reach sexual maturity after four to six years while males reach sexual maturity after seven to thirteen years. Females show no parental involvement once their young is born and males exhibit no parental care beyond the act of mating. In captivity, the Baja California Rattlesnake can live up to seventeen years. While there is limited information regarding the lifespan of wild Baja California Rattlesnakes, another species in their genus, Timber Rattlesnakes (Crotalus horridus), can live sixteen to twenty-two years in the wild. It is likely that Baja California Rattlesnakes have similar life spans in the wild. 

Baja California Rattlesnakes are crepuscular and hunt nocturnally. During the day they primarily remain hidden among rocks and vegetation, but they will emerge to bask in sun-exposed areas such as rocks or bare patches of ground. They are mobile and social, typically living in small groups. In the winter when temperatures are low, they brumate to conserve energy. While Baja California Rattlesnakes are venomous, they mostly strike at prey and will only strike at predators that are not deterred by their rattles. They primarily feed on small mammals and lizards, but they will sometimes consume arthropods as well. They eat prey dead or alive, as long as they can swallow them whole. In turn, the Baja California Rattlesnake serves as prey for mammals such as bobcats, coyotes, and wild boars. They are also preyed upon by birds of prey such as red-tailed hawks and turkey vultures.

Baja California Rattlesnakes are endemic to the Baja California peninsula. Their range extends from the southern tip of the peninsula to as far north as the San Quintin Valley in central Baja California, Mexico. In addition, they can be found on several islands off the coast of the Baja California peninsula,  both in the Gulf of California and the Pacific Ocean. They inhabit arid lowlands and montane regions including deserts, canyons, and sand dunes. Typically, they live in areas where they can shelter in rocky outcrops or under vegetative cover. They use old mammal burrows or hollow spaces under rocks, logs, and plants to conceal themselves from predators and prey.


The Baja California Rattlesnake may be confused with the Southern Speckled Rattlesnake, Crotalus mitchellii, because they are both found on the Baja California peninsula. These species can be differentiated visually. Southern Speckled Rattlesnakes have dark and light rings that surround their thick tail and considerably contrast their lighter ash-gray tail color. In addition, their body is marked with a vague pattern of dark speckled bands.

From a conservation perspective, the Baja California Rattlesnake is currently considered to be of Least Concern with a stable population. Their exact population numbers are difficult to evaluate because they typically avoid human activity and are not often encountered. Currently, they are facing habitat fragmentation and habitat loss in the northern part of their range from increased agricultural development. The Baja California Rattlesnake has been observed around human dwellings and if encountered, EXTREME CAUTION should be used. While they are considered to be moderately venomous, a bite from a fully-grown snake may result in severe envenomation that can cause pain, swelling, nausea, vomiting, an even shock and multiple organ damage. Before it strikes, the Baja California Rattlesnake is known to display sufficient warning and aggression signs that indicate it wants to be left alone.