Rattlesnakes

Genus Crotalus

Rattlesnakes: Unique Among Venomous Snakes in the United States

Throughout the world, there are many snakes whose venomous bites can be fatal to humans. In the United States, the primary venomous snakes include the coral snake, the copperhead, the cottonmouth water moccasin, and the rattlesnake.

Rattlesnakes: Among these, rattlesnakes are particularly noteworthy due to their distinctive rattle, which serves as a warning signal to potential threats. There are several species of rattlesnakes across the country, each adapted to different environments ranging from deserts to forests. Rattlesnake venom contains a mixture of hemotoxins and neurotoxins, making their bites especially dangerous. Their unique physical characteristics, such as the triangular head and elliptical pupils, set them apart from other venomous snakes.

While the other venomous snakes are also significant, rattlesnakes have unique adaptations and behaviors that make them a fascinating subject of study. Their ability to detect vibrations, their specialized hunting techniques, and their distinctive rattle all contribute to their status as one of the most recognized and researched venomous snakes in the United States.

 

 

Types of Rattlesnakes: An Overview of 32 Species

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

These species include:
Western Diamondback Rattlesnake (Crotalus atrox)
Eastern Diamondback Rattlesnake (Crotalus adamanteus)
Timber Rattlesnake (Crotalus horridus)
Pygmy Rattlesnake (Sistrurus miliarius)
Mojave Rattlesnake (Crotalus scutulatus)
Prairie Rattlesnake (Crotalus viridis)
Sidewinder Rattlesnake (Crotalus cerastes)
Speckled Rattlesnake (Crotalus mitchellii)
Red Diamond Rattlesnake (Crotalus ruber)
Tiger Rattlesnake (Crotalus tigris)
Black-tailed Rattlesnake (Crotalus molossus)
Rock Rattlesnake (Crotalus lepidus)
Banded Rock Rattlesnake (Crotalus lepidus klauberi)
Twin-spotted Rattlesnake (Crotalus pricei)
Santa Catalina Rattlesnake (Crotalus catalinensis)
Midget Faded Rattlesnake (Crotalus oreganus concolor)
Great Basin Rattlesnake (Crotalus oreganus lutosus)
Northern Pacific Rattlesnake (Crotalus oreganus oreganus)
Southern Pacific Rattlesnake (Crotalus oreganus helleri)
Arizona Black Rattlesnake (Crotalus cerberus)
Grand Canyon Rattlesnake (Crotalus abyssus)
Durango Rattlesnake (Crotalus durissus)
Mexican West Coast Rattlesnake (Crotalus basiliscus)
Neotropical Rattlesnake (Crotalus durissus terrificus)
Uracoan Rattlesnake (Crotalus durissus cumanensis)
Tancitaran Rattlesnake (Crotalus polystictus)
Venezuelan Rattlesnake (Crotalus vegrandis)
Western Massasauga (Sistrurus catenatus tergeminus)
Eastern Massasauga (Sistrurus catenatus)
Desert Massasauga (Sistrurus catenatus edwardsii)
Queretaran Dusky Rattlesnake (Crotalus aquilus)
Yucatecan Rattlesnake (Crotalus tzabcan)

These rattlesnakes exhibit a variety of patterns and colors, ranging from shades of brown, gray, and black, to tones of yellow, cream, rust, olive, and light pink. Some species have banded, diamond-shaped, or blotched patterns, while others may lack a distinct pattern altogether.

 

 

Understanding Pit Vipers:
Rattlesnakes, Copperheads, and Cottonmouths

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.

Rattlesnake Tongue: Detecting Microscopic Particles

Rattlesnakes have a forked tongue that they flick up and down. The tongue picks up 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.

Rattlesnake Nostrils: Additional Scent Detection

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.

How Rattlesnakes Hear: Vibration Detection

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.

Rattlesnake Vision: Night Hunting Capabilities

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.

Closeup of a Western Diamondback Rattlesnake.  Photo by Dndavis.

 

Physical Characteristics of Rattlesnakes

Rattlesnakes exhibit several distinctive physical characteristics that make them easily identifiable among other snake species. Here are the key features:

Broad, Triangular Head: Rattlesnakes have a wide, distinctly triangular-shaped head.
Vertical, Cat-like Pupils: Their eyes feature vertical, slit-like pupils similar to those of a cat.
Variety of Scale Colors and Patterns: Rattlesnake scales come in a diverse range of colors and patterns.
Keeled Scales: Each scale has a raised ridge in the center, giving it a textured appearance.
Heavy or Thick Body: Rattlesnakes generally have a stout, robust body.
Large Tubular Fangs: Their fangs are long and fold back against the roof of the mouth when not in use.
Hinged Mouth: The mouth opens wide, up to 180 degrees, allowing them to consume large prey.
Blunt Tail with Jointed Rattle: Adult rattlesnakes have a segmented rattle at the end of their tail. (Note: Baby rattlesnakes do not have rattles, and some adults may break or lose theirs.)
Size and Habitat: In ideal habitats with abundant small rodents, rattlesnakes can grow up to five feet in length. However, the average adult size is between three to four feet.

These physical traits not only help in identifying rattlesnakes but also play crucial roles in their hunting, defense, and overall survival in various environments.

Rattlesnake Range: Habitats Across North America

While most rattlesnake species 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: Seasonal Movements and Habits

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. 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.

 

Rattlesnake Temperature Regulation: Cold-blooded Adaptations

Rattlesnakes are cold-blooded (ectothermic) and rely on external sources to regulate their body temperature. When rattlesnakes are too hot, they retreat into the shade or a burrow. When they are 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: Do Rattlesnakes Lay Eggs?

While some types of snakes lay eggs, rattlesnake young are born alive. Rattlesnakes do 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 rattlesnake's body, and then she gives birth to her young. This reproductive system is called ovoviviparous.

Rattlesnakes reach sexual 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 mating, the female rattlesnake is passive while the male crawls on top of her, making jerking motions with the hind portion of his body to inseminate her. The female can store the semen for months, allowing them to fertilize the ova sometimes six months later. A female rattlesnake may carry from four to 25 eggs, from which an average of nine or ten young are born alive. Young are usually born between August and October.

What Does a Baby Rattlesnake Look Like?

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

Baby Western Diamondback Rattlesnake. Photo by Brian Magnier from Getty Images.

Do Baby Rattlesnakes Have Rattles?

Young rattlesnakes 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.

Rattlesnake Growth and Molting

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.

Lifespan and Predators of Rattlesnakes

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. Predators include the kingsnake, which is immune to rattlesnake venom and preys on rattlesnakes. Other predators include roadrunners, pigs, hawks, eagles, and humans.

What Do Rattlesnakes Eat? Rattlesnake Diet and Feeding Habits

Rattlesnakes are carnivorous and swallow their food whole. The size of the prey a rattlesnake selects is limited by its own size. Rattlesnakes eat lizards and small rodents such as ground squirrels, small rabbits, rats, and mice. The rattlesnake first bites its prey to immobilize it with toxic venom. The venom stuns and immobilizes the prey, allowing time for the rattlesnake to swallow the victim whole. The venom also begins the digestive process as it breaks down the tissue of the prey. After swallowing its prey, a rattlesnake will hide out while the meal is digested, a process that can take several days depending on the size of the meal.

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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?
Are rattlesnake bites becoming more dangerous?
The Rattlesnake Video

Laurence Klauber
His Groundbreaking Rattlesnake Research

Laurence M. Klauber, a renowned herpetologist, made significant contributions to the understanding of rattlesnakes. His extensive research has provided invaluable insights into various aspects of rattlesnake biology, behavior, and physiology.

Comprehensive Study and Classification

Klauber authored the seminal work "Rattlesnakes: Their Habits, Life Histories, and Influence on Mankind," which remains one of the most detailed and authoritative books on rattlesnakes. His classification work laid the foundation for much of what is known about the different species and subspecies of rattlesnakes. He meticulously cataloged various species, documenting their physical characteristics, behaviors, and habitats.

Behavior and Physiology

Klauber conducted numerous studies on rattlesnake behavior, physiology, and ecology. His research provided insights into their reproductive habits, feeding patterns, and defensive behaviors. He explored how rattlesnakes use their distinct rattle as a warning mechanism, their hunting strategies, and their interactions with prey and predators.

Vibration Detection Study

Klauber was particularly interested in how rattlesnakes detect vibrations. One notable experiment involved placing rattlesnakes in controlled environments to observe their reaction to vibrations. He found that rattlesnakes are highly sensitive to ground vibrations, which they detect through their body muscles and transmit to their inner ear via their jaw bones. This ability allows them to sense the presence of prey and predators, even when they are not visible.

Sensory Abilities

In addition to vibration detection, Klauber studied other sensory capabilities of rattlesnakes. He examined their heat-sensing pits, which allow them to detect warm-blooded prey even in complete darkness. He also explored their keen sense of smell, facilitated by their forked tongue and Jacobson's organ, and their vision, which is adapted for detecting movement and seeing well in low light conditions.

Field Studies and Conservation

Klauber's field studies included tagging and tracking rattlesnakes to understand their movements and habitat preferences. He collected extensive data on their distribution and population dynamics. His work emphasized the importance of conserving rattlesnake habitats and understanding their role in the ecosystem.

Legacy

Klauber’s meticulous approach to studying rattlesnakes has left a lasting legacy in the field of herpetology. His research has not only enhanced scientific knowledge but also contributed to public education and awareness about these fascinating reptiles. His efforts in classification, behavioral studies, and sensory research have paved the way for future herpetologists to build upon his foundational work.

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