The Reptiles and Amphibians of Arizona

Online Field Guide to The Reptiles and Amphibians of Arizona

Western Rattlesnake (Crotalus oreganus) Arizona
Crotalus oreganus abyssus, Coconino County, AZ

C. o. concolor Coconino Co., AZ

C. o. lutosus Mohave Co., AZ

WESTERN RATTLESNAKE Crotalus oreganus

Venomous

DESCRIPTION: A medium to large (up to 1,650 mm or 63″ in total length excluding rattle) rattlesnake with highly variable coloration and large dorsal blotches. Coloration can be straw-yellow, tan, pink, salmon, gray, gray-brown, off-white, cream, or olive. The dorsal blotches are usually dark-edged with centers that are only moderately darker than the background color. The blotches narrow and become more like bands near the tail. Dark gray or black rings often mark the tip of the tail. A dark line runs from behind the eye to the corner of the mouth. Blotches can be very faded in adults and some older specimens lack body markings entirely. Young are usually pale gray or tan with dark, distinct dorsal blotches and facial markings. The pupils are vertically elliptical and the dorsal scales are keeled. The neck is slender and the head is broad and triangular. On the end of the tail is a rattle composed of a series of loosely interlocking keratinous sections. A new section is added each time the snake sheds its skin.

DISTRIBUTION: This snake is found in extreme northwestern Arizona. It occurs in the upper Grand Canyon, Marble Canyon, Glen Canyon and associated side canyons as well as on the Arizona Strip (the portion of Arizona north of the Colorado River). Elevation ranges from 1,900′ to ca. 8,000′.

HABITAT: Found in a variety of biotic communities in Arizona including Mohave Desertscrub, Great Basin Desertscrub, Great Basin Grassland, and Great Basin conifer Woodland. It inhabits steep and rocky canyons and their tributaries, rolling foothills, high plains, and plateaus.

BEHAVIOR: Diurnal and crepuscular in spring and fall. Nocturnal during the warmest part of summer. It hibernates during the cold months of late fall and winter. Like the other “pit-vipers” (members of the subfamily Crotalinae) this snake uses heat sensing pits (one on each side of the face between the eye and nostril) to detect warm-blooded predators and prey.

DIET: The Western Rattlesnake feeds on rats, squirrels, mice, lizards, and birds. It uses venom injected through long, hollow, retractable fangs to kill and begin digesting its prey.

REPRODUCTION: Young are born in summer.

SUBSPECIES FOUND IN AZ:
GRAND CANYON RATTLESNAKE Crotalus oreganus abyssus. This subspecies reaches a maximum size of 24″ to 40″. The dorsal blotches are usually faded in adults. Some adults lack body markings entirely. Coloration is usually light tan, yellowish tan, or light gray brown; less commonly pink or reddish brown. Some individuals show muted facial markings including dark bars with light colored edges that extend back from the eye to the corner of the mouth. Young are distinctly blotched and have prominent head and facial markings. This snake’s range is entirely within the Grand Canyon and related upriver canyons into Glen Canyon.
MIDGET FADED RATTLESNAKE Crotalus oreganus concolor. This subspecies reaches a maximum size of 16″ to 26″. The dorsal blotches are usually faded in adults. The centers of the blotches are the same color as (or only slightly darker than) the base color. Base coloration ranges from light pinkish tan to light gray. Muted facial markings include dark bars with light colored edges that extend back from the eye to the corner of the mouth. Young have prominent blotches and distinct head and facial markings. The Midget Faded Rattlesnake once inhabited a small portion of northern Arizona. This snake’s historic range in Arizona is now submerged by Powell Reservoir.
GREAT BASIN RATTLESNAKE Crotalus oreganus lutosus. This subspecies reaches a maximum size of 30″ to 54″. Its dorsal blotches are usually clearly defined with dark edges and lighter centers. Coloration is variable and ranges from off white to shades of yellow, tan, gray, light purple-gray, or light pinkish gray. Facial markings include dark bars with light colored edges that extend back from the eye to the corner of the mouth. This snake is found on the Arizona Strip (Northwestern AZ in Mohave and Coconino Counties).

REMARKS: This rattlesnake is capable of delivering large amounts of potent venom. If encountered it should be left alone. A large percentage of envenomations occur when a snake is handled or abused.

By Thomas C. Brennan

Bartlett. 2000. Snakes of North America: Western
Region. Gulf Publishing Co. Houston, TX

Brennan, T. C., and A. T. Holycross. 2006. A Field Guide to Amphibians and Reptiles in Arizona. Arizona Game and Fish Department. Phoenix, AZ

Brennan, T. C., and A. T. Holycross. 2004 Crotalus oreganus concolor. Geographic Distribution. Herpetological Review 35(2).

Fowlie. 1965. The Snakes of Arizona. Azul Quinta Press, Fallbrook, California

Lowe, Schwalbe, Johnson. 1986. The Venomous Reptiles of Arizona. Nongame Branch
Arizona Game and Fish Department. Phoenix, AZ

Stebbins. 1985. Western Reptiles and Amphibians. Houghton Mifflin. New York, NY

Western Rattlesnake (Crotalus oreganus) Arizona Range Map

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