Genus Crotalus

Venomous Snakes - Throughout the world there are many snakes whose venomous bite can be fatal to humans. In the United States, however, there are only four: the coral snake, the copperhead, the cottonmouth water moccasin and the rattlesnake.

Rattlesnake Description & Identification - There are 32 known species, which contain numerous subspecies with many color variations. They all share in common a distinctively triangular head and jointed rattles on their tail.

Photo Western Diamondback Rattlesnake

Rattlesnakes, copperheads and cottonmouths are all pit vipers. Pit vipers are snakes with two pits under their nostrils to detect heat, thus enabling them to hunt warm-blooded prey. The pits are so sensitive that the snake can determine the size of the warm-blooded animal and can even detect prey in complete darkness.

Each species can be identified by variations of the colored patterns on their skin. Colors range from shades of brown, gray and black, to tones of yellow, cream, rust, olive and light pink. A rattlesnake's skin may display a pattern that is banded, diamond shaped, or blotched, though some species of rattlesnake have no identifying pattern at all.

Rattlesnakes have a forked tongue that they flick up and down. The tongue picks microscopic airborne particles and gases from the air. When the tongue slips back into its mouth, it touches a sensitive spot on the roof of the mouth called the vomeronasal organ, or Jacobson's organ. This organ picks up the particles collected by the tongue and sends messages to the snake's brain identifying the scent as food, enemy, mate or other object or substance.



Rattlesnakes have external nostrils lined with olfactory cells which also pick up scent, though they are mainly used for breathing. The fork of the tongue is a navigational aid. It can provide information based on which side or fork of the tongue has the strongest presence of a particular odor. This information can help the rattlesnake follow its prey or find its way home.

Rattlesnakes pick up vibrations through their body muscles which send sound through to their jaw bones and on to their inner ear organs. Rattlesnakes do not have outer ears and therefore rely on these vibrations to pick up sound.

The snake's eyes can detect objects or movement from about 40 feet away, but its vision is much sharper when objects are closer. A rattlesnake's pupils are elliptical, not round, which enables the snake to see well in dim light. This is helpful for night hunting.

Photo Desert Sidewinder

Common Questions About Rattlesnakes:

What are the symptoms of a rattlesnake bite?
How can I protect my dog and other pets from rattlesnake bites?
Are rattlesnake bites becoming more dangerous?
The Rattlesnake Video
Get the rattlesnake e-book.

Rattlesnakes have the following physical characteristics:

  • Broad, "triangular" head
  • Eyes have vertical "cat-like" pupils
  • Covered in scales that are a variety of colors/patterns
  • Scales are keeled, with a raised ridge in the center of each
  • Body is heavy or thick (fat) in appearance
  • Large tubular fangs in mouth that fold out when the mouth opens
  • Mouth is like a hinge, opening 180 degrees
  • Blunt tail with jointed rattle (Note: baby rattlesnakes don't have rattles and some adult snakes may break or lose their rattles)
  • In ideal habitats where there is a constant, abundant supply of small rodents, the rattlesnake sometimes attains a length of five feet, but the average adult size is between three to four feet.


photo rattlesnake rattle on tail

Rattlesnake Range: While most rattlers are concentrated in the southwestern United States, they extend north, east and south in diminishing numbers and varieties. Every contiguous state has one or more varieties of rattlesnake. The rattlesnake is found in many different biomes, ranging from along the coast at sea level, to inland prairies and desert areas, and all the way to mountains at elevations of more than 10,000 feet.

Behavior of Rattlers: In the northern areas of their range, and at higher elevations, rattlesnakes congregate in the fall at crevices in rocky ledges to hibernate for the winter. They return to these locations annually. These spots are known as snake dens.

When temperatures begin to warm in April, the rattlesnakes come out of hibernation. They remain near the den entrance for a few days, sunning themselves, then make their way to their summer habitats.

Most snakes are secretive in their summer activities, hunting at night and remaining inactive and out of sight for days at a time during the digestive period, after eating a squirrel or small rabbit.

Consequently, more snakes are seen in the spring and fall migrations to and from their winter homes.

Rattlesnakes are cold-blooded (ectothermic) and they rely on external sources to regulate their body temperature. When rattlesnakes are too hot they retreat into the shade or into a burrow. When a rattlesnake is too cold they sun themselves or find a surface, such as a paved road, to absorb the heat from the asphalt. It is common to find snakes on the road in the evening hours as they attempt to warm their bodies by lying on asphalt or concrete paved areas.

Life Cycle of Rattlesnakes: While some types of snakes lay eggs, a rattlesnake's young are born alive. The rattlesnake does have eggs, but the eggs are carried inside the female's body. Once the eggs are fertilized, they are carried for approximately 90 days. The eggs hatch inside the rattler's body, then she gives birth to her young. A reproductive system of this type is called ovoviviparous.

Rattlesnakes reach sexually maturity at about three years of age. Mating usually occurs in the spring after emerging from hibernation, but can also occur in the fall. During the process of mating, the female rattlesnake is passive while the male crawls on top of her. Making jerking motions with the hind portion of his body, the male presses his tail beneath the female's tail to inseminate her. The male continuously flicks his tongue throughout the mating process which can continue for several hours or more. Females are able to store the semen for months, allowing them to fertilize the ova sometimes six months later. The female rattler may carry from four to 25 eggs, from which an average of nine or ten young are born live. A female rattlesnake usually reproduces every two or three years. Young are usually born between August and October.

The newborn rattlesnake is about ten inches long and has a small horny button on the tip of its tail. Rattler babies have venom, short fangs and are dangerous from birth. In fact, they are more pugnacious than the adults. Although unable to make a rattling sound, the youngsters throw themselves into a defensive pose and strike repeatedly when disturbed.

Young rattlers are completely independent of the mother. They remain in the area of their birth for the first seven to ten days, until they shed their first baby skin and add their first rattle. The litter will begin to disperse as they venture out in search of food. Many newborn rattlesnakes do not survive their first year, either dying of hunger or being eaten by birds and animals. Even if they survive the first summer, they may perish during the first winter, if they can't find a suitable warm crevice in which to hibernate.

If all goes well, youngsters grow rapidly. Each time they come out of hibernation, they shed their skin. With each skin shedding (molting) a new rattle appears. During the rapid growth of the first few years, they may molt three times annually. Thus, the number of rattles is not a true indicator of age. Rattles also wear out or break off, so it is unusual to find an adult snake with more than 8 or 10 rattles.


The average lifespan of a rattlesnake is 20 to 30 years in captivity. In the wild, the lifespan is less due to predation, disease or death by accident.


The kingsnake is well known for being immune to the venom of many pit vipers, including rattlesnakes. Rattlesnakes are part of the kingsnake's diet. Roadrunners, pigs, hawks, eagles and humans are also rattlesnake predators.


Rattlesnakes are carnivorous. Instead of chewing their food, they swallow it whole. The size of the prey a rattlesnake selects is limited by its own ability to eat it, based upon its own size. Rattlesnakes eat lizards and small rodents such as ground squirrels, small rabbits, rats and mice, striking rather than attempting to hold their prey.

The rattlesnake first bites its prey to immobilize it with a toxic venom. When the hollow fangs of the rattler penetrate the victim's flesh, venom is injected as though through twin hypodermic needles. Most small prey is immediately stunned. The venom stuns and immobilizes the prey, allowing time for the rattler to swallow the victim whole. The venom also begins the digestive process as it breaks down the tissue of the prey.

Rattlesnakes have a highly-efficient digestive system which takes a lot of metabolic energy. After a rattlesnake swallows its prey, it will normally hide out while the meal is digested. Rattlesnakes become sluggish while digesting, a process that can take several days depending on the size of the meal.

Common Questions about Rattlesnakes:

What are the symptoms of a rattlesnake bite?
How can I protect my dog and other pets from rattlesnake bites?
How can I keep rattlesnakes out of my yard?

If you need help with a venomous bite or if you have a poisoning emergency, call your Poison Center immediately.   If the victim has collapsed or is not breathing, call 911. Poison Centers across the country now have a new national emergency phone number - 1-800-222-1222



What are the symptoms of a rattlesnake bite?
How can I protect my dog and other pets from rattlesnake bites?
Are rattlesnake bites becoming more dangerous?
The Rattlesnake Video


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