Rattlesnakes are venomous pit vipers with a rattle of keratin rings on the tail that buzzes as a warning. There are 33 species, all in the Americas. They sense the body heat of prey with pits on their faces, eat mostly rodents, and give birth to live young. They are shy, but a bite needs medical help straight away.
rattlesnakes quick facts
- The rattle is made of keratin, the same material as your fingernails.
- A rattlesnake gains a new rattle segment every time it sheds its skin.
- Heat pits can detect prey just a tenth of a degree warmer than its surroundings.
- Arizona has 13 kinds of rattlesnake, more than any other US state.
- A mother rattlesnake usually gives birth to 10 to 20 live babies.
Stay safe: if you see a rattlesnake, stay calm, keep still or back away slowly, and give it plenty of room. Never try to touch or catch one.
What is a rattlesnake?
A rattlesnake is a venomous snake with a rattle on the end of its tail. When it shakes its tail, the rattle makes a loud buzzing sound, a warning that says “keep away”.
Rattlesnakes live only in the Americas, from southern Canada all the way to central Argentina. They are most common and most varied in the deserts of the south-western United States and northern Mexico.
Encyclopaedia Britannica counts 33 species. Arizona has 13 of them, more than any other US state.
Rattlesnakes are pit vipers, a group of snakes named after a special heat-sensing pit on each side of the head. More about those pits later.
Most rattlesnakes belong to a group called Crotalus, which includes the small sidewinder of the North American deserts. Three species belong to an older group called Sistrurus, including the massasauga and the pygmy rattlesnake. These have nine large scales on the top of the head, where most rattlesnakes have lots of small ones.
What rattlesnakes look like
Most adult rattlesnakes are between 0.5 and 2 metres long, and a few reach 2.5 metres. Most are 2 to 4 feet (about 60 cm to 1.2 m) long.
The smallest is the twin-spotted rattlesnake, which is less than 12 inches (30 cm) long and weighs just 3 to 4 ounces. The longest is the eastern diamondback, which can grow up to 8 feet (2.4 m) and weigh 4 to 10 pounds.
Most rattlesnakes are blotched with dark diamonds, hexagons or other shapes on a lighter background, usually grey or light brown. Some are shades of orange, pink, red or even green. These patterns help them blend in with rocks, sand and dry leaves.
The western diamondback has an easy way to spot it. Its tail has jet-black and white rings, just before the rattle.
How the rattle works
The rattle is made of interlocking rings, called segments. They are made of keratin, the same material as your fingernails.
When the snake shakes its tail, the loose segments knock against each other and make a buzzing sound. A western diamondback can shake its rattle 40 to 60 times a second.
A baby rattlesnake is born with just a small button at the end of its tail. At one to two weeks old it sheds its skin for the first time, and the first real segment of its rattle appears. After that, it gains a new segment every time it sheds its skin.
You may have heard that you can tell a rattlesnake’s age by counting its rattle segments. That isn’t true. A snake may shed several times a year, and old segments can break off.
Seeing heat in the dark
Between each eye and nostril, a rattlesnake has a small pit. It is not an ear or a nose. It senses heat.
The pits are so sensitive that a rattlesnake can detect prey that is just one tenth of a degree warmer than its surroundings. With two pits, it can tell exactly where warm prey is, a little like seeing in heat. It can even strike a warm animal in complete darkness.
That is very useful, because most rattlesnakes hunt at night. They hide during the hot day and come out in the evening or at twilight.
What rattlesnakes eat
Rattlesnakes mainly eat small mammals, especially rodents such as mice, ground squirrels and rats. They also eat rabbits, birds and lizards. Young, small rattlesnakes eat mostly lizards.
A rattlesnake usually waits in hiding for prey to come close. Then it strikes, in about half a second, and injects venom through its fangs.
Adult rattlesnakes eat about once every two weeks. Younger ones eat more often, about once a week.
By eating so many rodents, rattlesnakes help to keep rodent numbers down. That is one reason they are important to the places where they live.
Fangs and venom
A rattlesnake’s fangs are long and hollow, a bit like curved needles. When the snake is not using them, they fold back against the roof of its mouth.
The venom is made in glands above the upper jaw. It flows down a tube, called a duct, and out through the fangs.
Some rattlesnakes have stronger venom than others. The Mexican west coast rattlesnake, the Mojave rattlesnake and the South American rattlesnake are the most dangerous, because their venom attacks the nervous system more strongly.
Where rattlesnakes live
Most rattlesnakes live in dry places, such as deserts and rocky scrubland. The western diamondback likes dry, rocky, shrub-covered land, where it can hide in rock cracks or mouse holes.
Others live in very different places. The timber rattlesnake lives in the eastern United States, and the prairie rattlesnake lives on the plains of the western United States. The South American rattlesnake is found all the way from Mexico to Argentina, the widest range of any rattlesnake.
In places with cold winters, rattlesnakes hibernate. They shelter underground, often in dens, until the weather warms up again.
Baby rattlesnakes
Rattlesnakes do not lay eggs in a nest. The mother keeps her eggs inside her body for about 90 days, and the babies are born alive.
A mother usually has 10 to 20 babies at a time. They are 7 to 15 inches (18 to 38 cm) long, depending on the species, and each one is wrapped in a thin, clear covering, like cling film, when it is born.
Baby rattlesnakes have venom and fangs from the start, so they can look after themselves very soon.
Rattlesnakes can live for a long time. In zoos, western diamondbacks live about 22 years on average, and some rattlesnakes reach 25.
How rattlesnakes defend themselves
Rattlesnakes are not aggressive. In fact, they are quite shy, and they will not attack people unless they are disturbed or handled.
When a rattlesnake feels threatened, it warns you first. It coils its body into a spiral, raises its head and neck into an S-shape and rattles its tail.
Rattlesnakes have enemies of their own. Hawks, bald eagles, roadrunners and wild turkeys all hunt them.
If you meet a rattlesnake
If you hear a rattle or see a rattlesnake, move away. Give it plenty of space, and it will usually leave you alone.
Watch where you put your hands and feet when you walk in rattlesnake country, especially near rocks and logs. Stay on paths, and never poke into holes. Keep pets on a lead, and if anyone sees a snake, tell an adult straight away.
A rattlesnake bite is very painful, and a bite from a large rattlesnake can kill. With modern treatment, bites are far less dangerous than they used to be, but anyone who is bitten must get medical help straight away.
Rattlesnakes in danger
Some rattlesnakes are rare. The Santa Catalina Island rattlesnake and the Aruba Island rattlesnake are endangered. Each lives only on one island.
They are threatened by people collecting them and by the loss of their habitat. Zoos and conservation groups are working to protect them.
Three things people get wrong
You cannot tell a rattlesnake’s age from its rattle. It gains a segment every time it sheds, which can be several times a year, and segments break off.
Rattlesnakes are not aggressive. They are shy, and they rattle to warn you away rather than to attack.
Rattlesnakes do not lay eggs in a nest. The eggs stay inside the mother, and the babies are born alive.
Did you know? A western diamondback can shake its rattle 40 to 60 times every second.
Try it
Put some dried beans or rice in a small plastic bottle and shake it fast. The buzzing sound is a bit like a rattlesnake’s warning. Now think about why a loud warning could keep a snake safe.
Knowledge check
What is a rattlesnake’s rattle made of?
Show answer
Keratin, the same material as your fingernails.
What do rattlesnakes use their heat pits for?
Show answer
To sense the body heat of prey, so they can find and strike it even in the dark.
Frequently asked questions
How many species of rattlesnake are there?
Encyclopaedia Britannica counts 33 species of rattlesnake. They all live in the Americas, from southern Canada to central Argentina, and Arizona has 13 of them.
What is a rattlesnake’s rattle made of?
A rattlesnake’s rattle is made of interlocking segments of keratin, the same material as fingernails. A new segment is added every time the snake sheds its skin.
Can you tell a rattlesnake’s age from its rattle?
No. A rattlesnake gains a rattle segment each time it sheds, which can happen several times a year, and old segments can break off, so the count does not show its age.
What do rattlesnakes eat?
Rattlesnakes mainly eat small mammals, especially rodents such as mice and ground squirrels. They also eat rabbits, birds and lizards, and young rattlesnakes eat mostly lizards.
Do rattlesnakes lay eggs?
No. A mother rattlesnake keeps her eggs inside her body for about 90 days, and the babies are born alive, usually 10 to 20 at a time.
What should you do if you see a rattlesnake?
If you see a rattlesnake, stay calm and move away, giving it plenty of space. Never touch it. Anyone who is bitten should get medical help straight away.
Sources
- Encyclopaedia Britannica: rattlesnake — the number of species, range, size, colours, behaviour, bites, heat pits and diet
- San Diego Zoo Wildlife Alliance: rattlesnake — the rattle, heat pits, venom, feeding, babies, hibernation, size, lifespan and conservation
- Animal Diversity Web, University of Michigan: western diamondback rattlesnake — range, habitat, tail rings, rattle speed, young, threat posture, predators and lifespan
