Poisonous Snakes in New Mexico by NM Fish and Game

Snakes are perhaps the most feared and hated animals in New Mexico, but people's fear of snakes comes from lack of understanding and superstition. Snakes are not mysterious at all, and these fascinating creatures don't deserve the anxiety many people feet about them. Of the 46 snake species found in New Mexico, only 8 are poisonous and potentially dangerous, including 7 species of rattlesnakes and a coral snake.

There are many benefits from having some snakes around the yard or garden. Snakes are one of nature's most efficient mousetraps, killing and eating a variety of rodent pests. While snakes will not eliminate pests, they do help keep their numbers in check. Some harmless snakes (king snakes and coachwhips) eat other snakes, including poisonous ones.

Although you wouldn't want a poisonous snake around your home, snake venom can be beneficial and has been used in developing a variety of human medicines. One type of high blood pressure medicine was developed using information based on chemicals in snake venom. Researchers are conducting studies using snake poisons to develop treatments for blood and heart problems. Snake venom is also being investigated for controlling some types of harmful bacteria.

Some snakes are quite rare and are protected species. These rare snakes are on state and federal endangered and threatened species lists. The ridgenose rattlesnake is on the federal list while the mottled rock rattlesnake, Mexican and narrowhead garter snakes, plainbelly water snake, green rat snake, and western ribbon snake are on New Mexico's endangered and threatened list.

Snakes are ectotherms, meaning they regulate their body temperature by absorbing or giving off heat. Because their body temperature is affected by environmental temperatures and varies with surrounding conditions, snakes become inactive during very hot seasons and very cold seasons. During these periods of inactivity, snakes may go for several weeks without eating. Because they are cold-blooded, snakes must rely on their behavior to regulate their body temperature. During the hot part of the day, snakes move to shaded areas, and on cool days they sun themselves in warm open areas. Snakes often seek out paved roads where they are attracted by the heat from the road surface.

Because snakes have a backbone, they are classified as vertebrates. Although fish, mammals, birds, and people are also vertebrates, the snake's skeletal system is unique. Snake bones are very light and the skeleton is very flexible. The lower jaw and skull are connected by a piece of stretchy material (ligament) that allows the snake to open its mouth very wide and move each jaw independently. Thus, snakes can swallow prey much larger than their head by "walking" their mouth around the food from side to side in a forward movement.

Snakes are specialized animals, with no legs, ears, or eyelids. There are no "walking" snakes. Often the sex organs of a snake may protrude from the anal plate area and be confused with legs.

Snakes use their forked tongue to smell, constantly flicking it to pickup any airborne particles and odors. Once a snake detects an aroma, it inserts its tongue into two holes on the top of its mouth, where the smells are interpreted by its brain. If the snake detects food and is hungry, it will pursue the animal.

Contrary to popular belief, snakes are not slimy; in fact, they feel dry to the touch. Snake scales and skin help retain body moisture. Snakes shed their skin and eye coverings together.

Soon after temperatures rise in the spring, snakes come out of hibernation and mate. Some snakes lay eggs in a damp protected area where they will hatch in about two months. Other snakes hatch eggs inside their bodies. Once the young have been hatched or born, parents do not care for their offspring because they are able to take care of themselves.

All snakes are predators, and many are fussy eaters. Bullsnakes eat rats, mice, and chipmunks. King snakes feed on other snakes, mice, young birds, and bird eggs. Some small snakes, like the smooth green snake, eat insects, while others (earth snakes and worm snakes) eat earthworms, slugs, and salamanders. Toads are the favorite food of hognose snakes.

When people encounter a snake, they often corner it, causing the snake to hiss loudly, open its mouth in a threatening manner, coil up, and strike at the individual-or bluff by advancing toward the intruder. These behaviors, intended to scare off the intruder, lead to a common misconception that snakes charge or attack people. In most cases, a snake advances only if it feels threatened. Usually it crawls away if it can reach cover safely. If you encounter a snake, leave it alone. A snake cannot reach around and grab its tail, rolling away from predators-there are no "hoop" snakes.


In New Mexico, rattlesnakes are the most common poisonous snakes. 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. The rattle begins with a single, soundless button on small snakes and grows with age, a new segment being added every time the snake sheds. Snakes shed variably according to their rate of growth and may shed several times a year. Thus, rattle size is not a good indicator of exact age, as often believed.

Some nonpoisonous snakes, such as bullsnakes, coachwhips, 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.

Although you must be dangerously close, another way to identify a rattlesnake is a conspicuous sensory area known as a pit on each side of the head. The pit looks somewhat like a nostril and helps the snake locate warm-bodied food. It is located about midway between and slightly below the eye and nostril.

Additionally, 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.

The rock rattlesnake occurs 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.

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.

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.

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 rattle-snake is often greenish-gray or olive green, with a white belly. Its venom is highly potent.

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.

The ridgenose 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 bootheel of the state, living in pineoak woodlands, open grassy hillsides, and humid canyon bottoms. Its color is reddish brown, yellowish brown, or gray. Ridgenose rattlesnakes are generally active day or night and tend to have a mild temperament.