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New Mexico Snakes — recognizing the poisonous ones and controlling them around homes

By James E. Knight, Extension Wildlife Specialist and Billy Tarrant, Extension Assistant

Last updated on Saturday, January 11, 2003

Diamondback Rattlesnakes Photo by Don Lovell
Diamondback Rattlesnakes
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 feel 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 coach-whips) 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 ridge-nose rattlesnake is on the federal list while the mottled rock rattlesnake, Mexican and narrow-head garter snakes, plain-belly water snake, green rat snake, and western ribbon snake are on New Mexico’s endangered and threatened list.

Snake Biology

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 (aestivation) and very cold seasons (hibernation). 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 (liga) 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 pick up any airborne particles and odors. Once a snake detects an aroma, it inserts its tongue into two holes on the top of its mouth (Jacobson’s organ), 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 off-spring because they are able to take care of themselves.

All snakes are predators, and many are fussy eaters. Bull-snakes 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.

Controlling Snakes Around the Home

Various home remedies, including moth balls, sulfur, lime, cayenne pepper, sticky bird repellent, coal tar and creosote, gourd vines, and musk from king snakes, have not proved effective in deterring snakes. No fumigants or poisons are registered for snake control. Although there are chemicals on the market that claim to repel snakes, most scientific investigations have found them ineffective. The only efficient method of discouraging snakes is to modify the environment so they find it unattractive.

Snake Habitat

Snakes often live in cool, dark places where food is abundant.

Likely places to find snakes around homes include:

Modifying the Environment Around Your Home

The environment around a home can be made less attractive to snakes by removing potential snake shelters (usually cool, dark, damp hiding places) and food sources (rodents).

Lawns and fields that are kept clean and closely mowed are less attractive to snakes than areas with tall grass, weeds, brush, and junk. Remove other snake hiding places such as old boards lying on the ground, rock and junk piles, and trash piles. Trim shrubs and bushes so limbs hang no lower than 12” from the ground. Stack fireplace or stove wood away from the home on a rack (not on the ground) that sits at least 12” from the ground.

Keeping the yard clean also removes habitats for rodents, a favorite snake food. Other suggestions for reducing a snake’s food source include placing garbage in sealed trash cans (not bags) away from the house. If you feed pets outside, keep all dog and cat food cleaned up after each feeding and store feed in a steel trash can so it is unavailable to rodents.

Keeping Snakes Out of Your Home

Snakes enter buildings in search of cool, damp, dark areas, or places where rodents and insects abound. To prevent snakes from entering your home, check the foundation for cracks and openings 1/4" or larger. Use mortar to plug holes in poured concrete, concrete block, or brick foundations. Use 1/8” hardware cloth or sheet metal to seal holes and cracks in wooden buildings. Seal cracks and openings around windows, doors, electrical pipes, and wiring with caulk or injectible foam. If you have an open septic tank or sump pump drain outside, cover the opening with 1/4” hardware cloth. Be sure to check it periodically to ensure the wire does not interfere with drainage.

If you have young children and live in an area where poisonous snakes are common, you may want to invest in a snake-proof fence. These fences are expensive to construct, so fencing an entire yard is not practical; however, you can enclose a small area where young children can play safely.

Construct snake-proof fences of 1/4” hardware cloth at least 36” wide. Bury the lower 6“ underground, and slant the fence outward at a 30° angle. To make the fence more sturdy, place supporting stakes inside the fence and attach wires from the fence to the stakes. Make sure all gates fit tightly; they should open to the inside because of the outward slope of the fence. Be sure to keep grass and weeds around the fence mowed close to the ground to prevent snakes from using them to crawl over the fence.

A snake-proof fence can keep snakes from entering an area, shelters (usually cool, dark, damp hiding places) and food sources (rodents).

Removing Snakes from Inside a Building

Occasionally homeowners encounter a snake inside the home, usually in a basement or crawl space. Snakes are attracted to these areas by warmth on cold days and cool shade on hot days.

You can increase your chances of capturing a snake in the basement by placing rumpled, damp cloths covered by a dry cloth in areas where snakes have been seen. You can then remove the whole works (cloths and snakes) or capture the snakes individually and remove them. If you are not afraid of snakes, the best way to remove non-poisonous snakes is to sweep them into a bucket or large garbage can with a broom. The snakes can then be released in a safe place 2 miles or more from human dwellings.

NOTE: Exercise extreme caution when moving in a crawl space, especially if venomous snakes have been seen in the area; a face bite can be very serious. A face-to-face encounter with even a non-poisonous coach-whip or bull snake can be an unpleasant experience.

Use a Glueboard Trap to Catch Larger Snakes

Another effective method of capturing snakes inside a home, under porches, in crawl spaces, or under mobile homes is to use a glueboard purchased from an agriculture supply or hardware store. Most small snakes can be captured using a single glueboard placed against a wall, away from pipes or other objects a snake could use for leverage to escape.

To capture larger snakes, make a large glueboard with purchased glueboards. Construct the trap using a 16” x 24” piece of 1/4” plywood. Drill a 3/4” hole in one comer of the board. When you need to remove the board, use a hook on the end of a long stick to grab the comer through the hole. Fasten or securely glue two to four glueboards along one side of the plywood board. This type of trap, when placed against a wall, is capable of capturing snakes up to 5 or 6 ft long.

Use glueboards only indoors or under structures where children, pets, and other wildlife cannot reach them; the glue is quite messy and hard to remove. Use common cooking or vegetable oil to remove animals from the glue. Once the unwanted guests have been removed, be sure to close any holes or entrances so the snakes do not return.

Remember, snakes are an important part of our natural world. The best approach to managing snake problems, whenever possible, is to leave these animals alone.

Recognizing Poisonous Snakes in New Mexico

Rattlesnakes

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 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.

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 rattlesnake 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 Ridge-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.

Coral Snake

The Arizona 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.

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