A rattlesnake striking with fangs extended. Rattlesnake bites can be dangerous but are very rarely fatal to humans.
Credit: Audrey Snider-Bell | Shutterstock
Rattlesnakes are a genus of pit vipers, comprising 33 species, all found throughout North and South America. They have the greatest concentration in the Southwestern United States and in Northern Mexico. Arizona is home to 13 species of rattler, more than any other state.
Rattle and hiss
Residents of the Southwestern United States have likely heard the distinctive buzz of these vipers. Their namesake rattle is a highly effective warning sign, signaling predators to stay away. Their rattle comes from a series of interlocking keratin rings that make a hissing buzz when vibrated. Another ring is added to the rattle each time the snake sheds its skin. Scientists consider the rattlesnake’s rattle a highly evolved and sophisticated warning system — which makes sense since these are the newest and most evolved snakes in the world.
Rattlesnakes also hiss, a second element of its warning posture that is often overlooked and overshadowed by its rattle, writes Laurence Monroe Klauber in "Rattlesnakes: Their Habits, Life Histories, and Influence on Mankind, Vol. 1" (1972, University of California Press). The hiss may be produced by exhaling or inhaling, or both. The snake's one functional lung has relatively large air capacity, and as the snake hisses, its body may swell up or deflate. Interestingly, snakes are deaf to airborne sounds, so the hiss is only a warning for animals that can hear and not a means of communication with other snakes.
Rattlesnakes can grow from one to seven feet (30 centimeters to 2 meters), depending on the species. They are thick-bodied snakes with keeled (ridged) scales in a variety of colors and patterns. Most species are patterned with dark diamonds, rhombuses or hexagons on a lighter background.
Like all pit vipers (including the copperhead and cottonmouth), they have sensory pits on their faces, which are used to sense heat from prey when hunting. After the rattle, their most distinctive physical feature is their triangular head. They have vertical pupils, like cat’s eyes.
Young rattlesnakes do not yet have their rattles, though they are as dangerous as adults. Furthermore, some adults may lose their rattles, so it is a good idea to look out for the triangular head. [Image Gallery: Snakes of the World]
These adaptable serpents can thrive in a variety of environments. They are most abundant in the desert sands of the Southwest, but they also like grasslands, scrub brush and rocky hills. They can be found in the swamplands of the Southeastern United States and in the meadows of the Northeast. These snakes can handle high elevation and are found everywhere from sea level to 11,000 feet (3,353 m).
Rattlesnakes spend some time in dens, which they make in rocky crevices. Those in colder climates hibernate there for the winter. Generation after generation of rattlesnake will use the same dens, for hundreds of years. Upon leaving their dens, they like to sun themselves on rocks and other open places. Though they are not nocturnal, in the hot summer months they may be more active at night.
Despite their venom, rattlesnakes are no match for king snakes, which are fond of putting them on their dinner menus.
Rattlesnakes are ovoviviparous, which means that eggs incubate inside the mother’s body. Babies are born live. Rattlers mate in the spring in a process that can take hours. Mothers can carry sperm for months before fertilizing the eggs, and then they carry babies for about three months. They only give birth every two years, usually to about 10 baby rattlers, Mothers don’t spend any time with their offspring, slithering off as soon as they are born.
Rattlesnakes can live up to 30 years.
Rattlesnakes’ favorite foods are small rodents and lizards. They lie in wait until a victim comes along, and then strike at speeds of five-tenths of a second. Their venom paralyzes the prey, which they then swallow whole. The digestive process can take several days, and rattlesnakes become sluggish and hide during this time. Adult rattlers eat about every two weeks.
Most people bitten by rattlesnakes have inadvertently stepped on them — so watch where you’re walking! Rattlesnake bites can be dangerous but are very rarely fatal to humans. With proper medical treatment, including antivenom, bites are usually not serious.
Rattlesnake venom is typically a mix of hemotoxic and neurotoxic components, with more hemotoxins, except in baby rattlesnakes and the Mojave rattler. Hemotoxins affect the circulatory system and can destroy blood cells and skin tissues, and cause hemorrhaging. Neurotoxins immobilize the nervous system and can affect or stop the victim’s breathing. This is the more dangerous toxin. There is some evidence that rattlesnake venom is becoming more neurotoxic across the board, which may be an evolutionary strategy, as some rodents are evolving to be more resistant to hemotoxins.
Some of the most fascinating species of rattlesnake are the timber, diamondback, and tiger.
Sometimes called a cranebrake rattlesnake, these are highly endangered snakes found in the Eastern United States. They are large, growing up to 6 feet (1.8 m) long, and have a large banded or chevron-shaped brown and black pattern. It is hard to see the brown pattern on some snakes and they look uniformly black. On others, the background is tan and their bands are clearly brown.
This is the largest venomous snake in North America, reaching up to 8 feet (2.4 m). They are found from North Carolina to Louisiana. They have a visually striking yellow-bordered black diamond pattern.
At up to seven feet long (2 m), this is the largest of the Southwestern rattlers and considered the most dangerous. Its back is covered with dark diamond-shaped patches lined with lighter scales, and its rattle has a unique black-and-white, raccoon-like color scheme. Unlike many other rattlers who flee, the Western diamondback will stand its ground, coil, and hiss when threatened.
A small rattlesnake reaching less than three feet (1 m), this Southwestern rattlesnake has the most extensive crossbanding of any rattler in its region. Its bands may be brownish or gray in color on a brown or orange-ish background. Its head is small in proportion to its body, so it holds less venom — though it is no less potent.
- San Diego Zoo: Rattlesnakes
- National Geographic: Eastern Diamondback
- California Department of Fish and Wildlife: Snakes
- University of Florida: Timber Rattlesnake
- New Hampshire Department of Fish and Wildlife: Timber Rattlesnake