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Thursday, September 2, 2010

Poisonous Snakes Of The Southwest


Rattlesnakes are the most common poisonous snakes in New Mexico and throughout the Southwest. The primary way to distinguish a rattlesnake from other snakes is the presence of a rattle, a series of horny rings formed of keratin that scrape against each other in pulses to cause a rattling sound.

Some nonpoisonous snakes, such as bull snakes, coach-whips, and rat snakes, behave like rattlesnakes when confronted. This behavior may include hissing loudly or vibrating the tail. If the tail is in contact with dry leaves or grass, these snakes may be mistaken for rattlesnakes.

Most rattlesnakes have triangular or “spade-shaped” heads (wide at the back and attached to a narrow neck). Many other harmless snakes can flatten their heads when threatened and may look like rattlesnakes.

New Mexico has seven species of rattlesnakes that vary in size, color, and other characteristics. The color of a rattlesnake’s scales often matches the environment; brown, gray, green, red, pink, or yellow.

Rock Rattlesnake

The Rock Rattlesnake are found in isolated mountain ranges in Southern New Mexico. This snake may be found in pine-oak forests, but mostly inhabits mountains with rugged, rocky terrain. It is variable in color and may be brown-black, greenish, or gray.


Western Diamondback

The Western Diamondback Rattlesnake is found throughout much of New Mexico, and is the species most often seen. It lives in flat plains and rocky canyons, from grassland deserts to pine-oak forests. The western diamondback is one of the largest of all rattlesnake species and the largest found in New Mexico (up to 6 ft long). Their color is most often gray-brown, although color often depends on the matching background color—many New Mexico snakes have a reddish to pinkish-gray color. This species has black and white rings on its tail, so it is commonly called the “coon-tail” rattlesnake.


Western Prairie Rattlesnake

The Western (Prairie) Rattlesnake is distributed across New Mexico, much of the western U.S., and into Canada. In eastern New Mexico, it is often called “sand rattler” and lives in a variety of habitats, from grassland desert to pine-oak forest. This species is generally more active after dark, except at high altitudes. Western prairie rattlesnakes are often greenish-gray or pale brown, with a series of light-colored rings on the tail that darken with maturity.

Mojave Rattlesnake

The Mojave Rattlesnake is found in extreme Southern New Mexico, although it is more common in southern California Nevada, Arizona and Texas and is more widely distributed in the Chihuahua Desert than the Mojave Desert. It lives in desert or low grassland habitats, often on flat terrain. The Mojave rattlesnake is often greenish-gray or olive green, with a white belly. Its venom is highly potent.

Black-tailed Rattlesnake

The Black-tailed Rattlesnake is distributed in southwestern and central New Mexico. It lives mostly in rocky mountainous areas, and is found occasionally in lower desert habitats. It is often colored a greenish or steel gray (but can be sulphur yellow or rust), with a dark brown or black tail. Generally considered mild mannered, this rattlesnake can nonetheless be quick to rattle and raise its head. It has been seen several feet off the ground in trees.


The Massasauga is distributed across southern, central, and eastern New Mexico where it occupies desert grassland, often in very sandy areas. This snake is relatively small (less than 4 ft long) and pale brown, and generally has pairs of spots on its head. Although not usually fatal to humans, bites from this species can be extremely painful.

Ridged-nose Rattlesnake

The Ridged-nose Rattlesnake is listed by the U.S. Fish and Wildlife Service as a threatened species in New Mexico. It inhabits only a small part of the southwestern boot heel of the state, living in pine-oak woodlands, open grassy hillsides, and humid canyon bottoms. Its color is reddish brown, yellowish brown, or gray. Ridge-nose rattlesnakes are generally active day or night and tend to have a mild temperament.


North American Sidewinder

The venomous Sidewinder is also called the "Horned Rattlesnake." It is unique because of its sideways form of locomotion with its body moving in an S-shaped curve.


Mojave and Sonoran deserts of southeastern California, western Arizona, southern Nevada and extreme southwestern Utah to Mexico.

This Sidewinder is light in color- tan, cream, pink, gray or sandy, with darker patches on its back of gray, yellow or tan. Mature adults grow 18 to 32 inches in length. It also has a dark eye strip extending back along its head.

The Sidewinder has rough, keeled scales, which aid in its unique sidewinding locomotion. Its supraoculars (triangular projections over each eye) are pointed and upturned giving them a horn-like appearance -thus its nickname, the Horned Rattlesnake.

Arizona Coral Snake (Sonoran Coral Snake)
(photo by Dr. Brendan P. O'Connor)

Coral Snake

The Arizona coral snake (also called the Sonoran Coral Snake) is found in extreme southwest Catron County and western Hidalgo and Grant counties. Although coral snakes rarely bite, their venom is highly poisonous and they should not be handled. The Arizona coral snake has a black nose and is brightly colored with broad alternating rings of red and black, separated by narrower rings of white or yellow. These markings encircle the body, although they are less bright on the belly.

In New Mexico, other snakes with similar markings are the New Mexico milk snake, Arizona mountain king snake, and the long-nosed snake. The narrower red bands are bordered by black on the New Mexico milk snake and Arizona mountain king snake, while the Arizona coral snake has broad red bands with yellow borders. The long-nosed snake is pale compared to the Arizona coral snake, with stripes that do not extend around the body and white spots on the side of the snake’s black bands.

An easy way to determine whether a red, yellow, and black snake is a coral snake is to remember that red touches yellow on a coral snake, and red touches black on non-poisonous species.

American Copperhead

Like all pit vipers, the American Copperhead is generally an ambush predator: it takes up a promising position and waits for suitable prey to arrive. One exception to ambush foraging occurs when copperheads feed on insects such as caterpillars and freshly molted cicadas. In the southern United States, they are nocturnal during the hot summer months, but are commonly active during the day during the spring and fall.

Like most North American viperids, these snakes prefer to avoid humans and, given the opportunity, will leave the area without biting. However, unlike other viperids they will often "freeze" instead of slithering away, and as a result many bites occur from people unknowingly stepping on or near them.

This tendency to freeze likely evolved because of the extreme effectiveness of their camouflage. When lying on dead leaves or red clay they can be almost impossible to notice. They will frequently stay still even when approached closely, and will generally strike only if physical contact is made.

Cottonmouth Snake
The Cottonmouth is found in the eastern United States from Virginia, south through the Florida peninsula and west to Arkansas, eastern and southern Oklahoma, and east and central Texas. A few records exist of the species being found along the Rio Grande in Texas, but these are thought to represent disjunct populations, now possibly eradicated.

The broad head is distinct from the neck, the snout blunt in profile with the rim of the top of the head extending forwards slightly further than the mouth. The body has a heavy build and a tail that is moderately long and slender.

Though the majority of specimens are almost or even totally black, (with the exception of head and facial markings) the color pattern may consist of a brown, gray, tan, yellowish olive or blackish ground color, which is overlaid with a series of 10-17 crossbands that are dark brown to almost black.

These crossbands, which usually have black edges, are sometimes broken along the dorsal midline to form a series of staggered half bands on either side of the body. These crossbands are visibly lighter in the center, almost matching the ground color, often contain irregular dark markings, and extend well down onto the ventral scales.

The dorsal banding pattern fades with age, so that older individuals are an almost uniform olive brown, grayish brown or black. The belly is white, yellowish white or tan, marked with dark spots, and becomes darker posteriorly.

Stay Prepared! Stay Alive!


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