Did you know that all 36 species of rattlesnake are native to the Americas? Their overall range stretches from southern Canada to central Argentina, and is concentrated in the American Southwest. They can survive in all kinds of habitats where their prey—birds, rodents, amphibians—is plentiful. Rattlesnakes belong to two genera in the subfamily Crotalinae (the pit vipers): Crotalus, from the Greek word for castanet; and Sistrurus, invoking an ancient Egyptian musical instrument. Both genus names undoubtedly refer to the snakes’ characteristic rattles. More interesting facts about rattlesnakes include: 

1. Venoms in rattlesnake bites are highly variable—even among members of the same species.
Each type of rattlesnake bite venom out there is an intricate cocktail loaded with different enzymes, toxins, and other compounds. Hemotoxins, which break down capillary walls and hinder blood circulation, are key ingredients in most of them. Neurotoxins, which attack the victim’s nervous system and cause seizures or paralysis, are another weapon. Venom composition can be extremely variable among individuals of the same species; for example, some timber rattlesnakes living in the American South have more neurotoxic venom than their northern counterparts do.

2. Rattlesnakes bite with movable fangs.
Cobras, mambas, and other snakes inject their venom into their victims through a pair of proteroglyphous, or fixed, fangs near the front of their mouths. Those snakes have to bite down and hang on to their prey to deliver the venomous punch. Rattlesnakes take a different approach. Like copperheads and Old World vipers, they have solenoglyphous fangs, which can actually swing forward and allow the rattlers to strike quickly, inject venom, and then back off. When the fangs aren’t being used, they’re pulled back and pressed against the roof of the snakes’ mouths.

3. The eastern diamondback rattlesnake is the largest venomous snake in North America.
Native to the southeastern U.S., the eastern diamondback can grow nearly 8 feet long and weigh more than 15 pounds. It’s the largest rattlesnake on Earth and the biggest venomous snake on the North American continent.

4. Rattlesnakes start growing rattles after their first shed.
Each rattlesnake is born with a nubby scale at the tip of its tail called a pre-button. After the snake’s first shed of their skin, the pre-button gets replaced with a button, a larger, hourglass-shaped scale. Later sheds add hollow, interlocking segments of keratin to the end of the tail. By vibrating the segments, the snakes create its distinctive rattling noise. Although it’s a myth that rattlesnakes must vibrate their tails before striking, they do use their rattles to warn approaching animals or people. Another popular myth suggests that each rattle section represents a year in the animal’s life. In reality, a rattlesnake can shed multiple times, and gain multiple rattle segments, in a single year. Segments can also wear down and break off over time. Crotalus catalinensis, the Santa Catalina rattlesnake, has evolved to be rattle-free. It lives on Isla Santa Catalina, a small island in the Gulf of California. Although it belongs to the same genus as diamondbacks and timber rattlers, the snakes’ ancestors may have lost their appendages because there are fewer predators and big, trample-y mammals on the island to warn with menacing noises.

5. Rattlesnakes don’t lay eggs.
Like anacondas, rattlesnakes are ovoviviparous. This means they produce eggs that hatch inside their bodies and give birth to live, fully formed young. Depending on the species, a rattlesnake litter can include anywhere from one to 25 infants.

6. Rattlesnakes help plants by distributing seeds.
In a 2018 study, researchers looked into the guts of 50 dead rattlesnakes preserved at museums. They found 971 plant seeds that were likely carried by the rodents the snakes had eaten. When a rattlesnake devours some hapless mouse, the seeds it carried in its cheek pouches make their way through the snake’s digestive tract intact. By pooping out the seeds, the snakes help to restore plant growth in its habitat.

7. Benjamin Franklin admired timber rattlers.
Benjamin Franklin thought that rattlesnakes embodied uniquely American diplomacy and toughness. “She never wounds till she has generously given notice, even to her enemy, and cautioned him against the danger of stepping on her,” he wrote in a Pennsylvania newspaper in 1775. “Was I wrong, Sir, in thinking this a strong picture of the temper and conduct of America?” He also noted that, like all snakes, timber rattlers don’t have eyelids, which made them naturally watchful. “She may therefore be esteemed an emblem of vigilance,” Franklin wrote. Rattlesnakes later became symbols of America’s war for independence. Christopher Gadsden, a colonel from South Carolina, designed a personal flag to be flown on five ships belonging to the Continental Army. The bright yellow banner sported a coiled rattlesnake emblem and the caption “Don’t Tread on Me.” It remains popular among advocates of smaller federal government today.

About 7,000 to 8,000 people are bitten each year, but thanks to effective antivenins, most do not prove fatal. Even so, bites are extremely painful, require immediate medical attention, and each vial of snake antivenin costs thousands of dollars!  The average snake bite victim requires anywhere from a few vials to dozens of them — it depends on factors like the size of the patient, the potency of venom in the bite and how quickly the patient is treated. The more antivenin needed, the higher the cost— and insurance often doesn’t cover much of it. Why take a chance?  Durable, protective snake gaiters for your lower legs, or snake chaps that protect up to your thigh, can be the best defense against rattlesnakes, copperheads, and other pit vipers. Dog snake vests and dog snake neck gaiters can also help keep your furry companions safe.