A rattlesnake’s warning is a dry, continuous buzz, closer to frying fat or a lawn sprinkler than to the maraca rattle of cartoons. The buzz changes as you move, and that change can trick your ears into thinking the snake is nearer than it really is.1Live Science. Rattlesnake rattles use auditory illusion to trick human brains It’s also an unreliable alarm, because many rattlesnakes stay quiet and several harmless animals imitate the sound.
What the Rattle Sounds Like Up Close
Each shake of the tail makes a short burst of noise, and fast shaking blends those bursts into one continuous sound.2PubMed. Frequency modulation of rattlesnake acoustic display affects acoustic distance perception in humans Up close, that sounds like a hiss-like buzz spread across many pitches rather than a single musical note.3PubMed. Frequency modulation of rattlesnake acoustic display affects acoustic distance perception in humans The rattle is also louder and covers a wider range of pitches than the snake’s breathy hiss.4Journal of Experimental Zoology. Hissing in rattlesnakes: Redundant signaling or inflationary epiphenomenon?
People describe it as sizzling, like bacon in a pan or steam escaping. Others compare it to a cicada or an electric buzz. It is dry and papery with a slightly rough edge, unlike the smooth hum of an insect or an appliance, and nothing like the slow, loose shaking of a toy rattle or a seed pod. A large snake’s buzz is usually louder and fuller than a small one’s, and species differ, so two rattlesnakes may not sound identical.
The sound changes as a threat approaches. The snake shakes faster as the threat comes nearer, up to about 40 shakes per second.5PubMed Central / Current Biology. Frequency modulation of rattlesnake acoustic display affects acoustic distance perception in humans When the threat gets close, it suddenly switches to a faster, steadier 60 to 100 shakes per second.6PubMed Central / Current Biology. Frequency modulation of rattlesnake acoustic display affects acoustic distance perception in humans You may hear the buzz rise steadily, like a car’s parking sensor, and then jump to a higher, more urgent whirr.7PubMed Central / Current Biology. Frequency modulation of rattlesnake acoustic display affects acoustic distance perception in humans Either change is a cue to stop moving toward the sound.
The rattle sits at ground level, often in grass or rock, so the buzz seems to rise from the earth itself, which makes it hard to tie to a single spot. From far off it is a faint dry hiss, and only up close can you pick out the gritty texture. Wind, running water, and your own footsteps can mask a faint buzz, so a quiet rattle may only become audible when you are already fairly near.
How a Rattlesnake Makes the Sound
The rattle is made of the same tough material as fingernails, formed into interlocking lobed segments.8PubMed Central. Evolutionary morphology of the rattlesnake style Because the segments are loose, they clash against each other when the tail shakes.9PubMed. Frequency modulation of rattlesnake acoustic display affects acoustic distance perception in humans A living segment at the base of the rattle, attached over fused tail bones, builds each new segment.10PubMed Central. Evolutionary morphology of the rattlesnake style There are no beads inside.
A baby is born with a single button at the tail tip, and the first true rattle segment appears after its first shed. Each shed leaves a new segment behind, but snakes can shed more than once a year when food and warmth are plentiful. Old segments also snap off with use and wear, so counting rings tells you little about age. Even a rattle with a broken tip can still buzz well.
The snake holds the rattle up off the ground and shakes it side to side until the tail is a blur. The movement is concentrated in the last stretch of the tail, and the front of the snake can stay still or coiled. The tail’s shaker muscles are packed with energy-producing parts and stored fuel.11PubMed. Rattlesnake shaker muscle: I. A light microscopic and histochemical study They contract extremely fast yet resist tiring far better than ordinary fast muscle.12PubMed. Rattlesnake shaker muscle: I. A light microscopic and histochemical study A rattlesnake can therefore keep up a buzz far longer than a harmless snake can shake its tail.13Ethology Ecology & Evolution. Microevolutionary change in mimicry? Potential erosion of rattling behaviour among nonvenomous snakes on islands lacking rattlesnakes
Why the Rattle Makes Snakes Seem Closer
Human ears seem to track how fast the buzz rises as you approach and use it to gauge distance.14Live Science. Rattlesnake rattles use auditory illusion to trick human brains When the snake suddenly jumps to the faster rate, listeners judge it to be closer than it actually is.15Live Science. Rattlesnake rattles use auditory illusion to trick human brains That may give the snake a built-in safety buffer between itself and an intruder.16Live Science. Rattlesnake rattles use auditory illusion to trick human brains Other mammals hear in similar ways, so the trick likely works on them too.17Live Science. Rattlesnake rattles use auditory illusion to trick human brains
If you think the snake is closer than it is, you are more likely to stop or back off, which gives the snake the space it wants. The effect comes from the change in speed, not from volume.
Location is also hard to judge. A buzz spread across many pitches is harder to pin down than a clear note, and rocks and brush scatter the sound so it seems to come from everywhere. Your sense of where the snake is may be off, so look before stepping in any direction.
A sudden move in a random direction could put you nearer the snake. Freeze, find the snake with your eyes, then back away the way you came, giving at least a couple of body lengths of space, more if unsure.
Rattlesnakes Also Hiss
Rattlesnakes hiss at pitches roughly from 400 to 4,700 Hz, about as loud as normal conversation.18Journal of Experimental Zoology. Hissing in rattlesnakes: Redundant signaling or inflationary epiphenomenon? The hiss likely happens when the snake inhales quickly to inflate its body in defense.19Journal of Experimental Zoology. Hissing in rattlesnakes: Redundant signaling or inflationary epiphenomenon? The air passes only through the nostrils, not the mouth.20Journal of Experimental Zoology. Hissing in rattlesnakes: Redundant signaling or inflationary epiphenomenon?
To your ear, the hiss is a breathy sound like air leaking from a tire. It comes and goes with the snake’s breaths, so it has pauses, whereas the rattle is a steady mechanical buzz with no gap. Because the hiss is only about as loud as conversation, you will usually hear it only at fairly close range.
A snake that hisses while its body swells is defensive, even if it never rattles. The hiss is a reason to give more space, since the snake is already alarmed and close enough for you to hear it. A rattlesnake with a broken or missing rattle may only hiss, so a hiss with no buzz does not mean the snake is harmless.
Rattlesnakes That Stay Silent
Some rattlesnakes rarely rattle: in one study of pygmy rattlesnakes, only about 3 in 100 rattled when provoked.21Eaglemountain Publishing (Biology of the Vipers). Rattle Loss in Pygmy Rattlesnakes (Sistrurus miliarius): Causes, Consequences, and Implications for Rattle Function and Evolution Having a longer, intact rattle didn’t make them any more likely to rattle.22Eaglemountain Publishing (Biology of the Vipers). Rattle Loss in Pygmy Rattlesnakes (Sistrurus miliarius): Causes, Consequences, and Implications for Rattle Function and Evolution
Some snakes can’t rattle at all. Young ridge-nosed rattlesnakes lose their first rattle segment and are effectively silent for about their first year.23Journal of Herpetology. Rattle Button Loss in Juvenile Ridge-nosed Rattlesnakes (Crotalus willardi): A Novel Mechanism for the Developmental Delay of the Rattle Adults that lose loose segments can lose nearly all sound.24Journal of Herpetology. Rattle Button Loss in Juvenile Ridge-nosed Rattlesnakes (Crotalus willardi): A Novel Mechanism for the Developmental Delay of the Rattle The Santa Catalina Island rattlesnake of Mexico has no rattle at all.25ACTA ZOOLÓGICA MEXICANA (N.S.). GENETIC RELATIONSHIPS OF THE SANTA CATALINA ISLAND RATTLELESS RATTLESNAKE, CROTALUS CATALINENSIS (SERPENTES: VIPERIDAE) So a silent snake is not necessarily a harmless one, and wear and breakage can leave a rattle too short or too light to make a loud buzz. Many snakes rely on camouflage first and rattle only if that fails.
A resting or hiding snake may simply stay still and hope you pass. It may still strike if you step on it or put a hand close, because the warning is a choice, not a required step before biting. Treat rock ledges, wood piles, and shaded edges as possible hiding spots whether or not you hear anything.
Without sound to rely on, watch where you put hands and feet, especially around rocks, logs, and ledges. Step onto logs rather than over them blindly, use a flashlight at night on warm trails, and wear sturdy boots and long pants in snake country.
Sounds That Mimic a Rattlesnake
Many nonvenomous snakes vibrate their tail tip when threatened, making a sound like a rattle.26Ethology Ecology & Evolution. Microevolutionary change in mimicry? Potential erosion of rattling behaviour among nonvenomous snakes on islands lacking rattlesnakes Fast tail vibration against the ground is common in many snakes, not only rattlesnakes.27Journal of Herpetology. Muscle Physiology and the Evolution of the Rattling System in Rattlesnakes Defensive tail vibration is widespread in both vipers and common harmless snakes, so rattling likely grew from this older habit.28PubMed. Behavioral Plasticity and the Origins of Novelty: The Evolution of the Rattlesnake Rattle Rattlesnakes can shake faster and much longer than these mimics.29Ethology Ecology & Evolution. Microevolutionary change in mimicry? Potential erosion of rattling behaviour among nonvenomous snakes on islands lacking rattlesnakes Harmless snakes living near rattlesnakes may benefit by sounding like them.30Wikipedia. Tail vibration
In dry leaves or dead grass, the rustle of a harmless snake can sound much like a small rattle. The sound comes from the tail hitting the surrounding surface, so it is loudest in leaves and fades on bare ground or grass. A rattlesnake’s buzz sounds much the same on any surface because the rattle itself is the noise source. Mimics also tend to be fainter and usually stop after a few seconds, while a rattlesnake can keep going, though that is one clue among several, not a sure test. If you can see the tail, a rattlesnake’s tip is usually blunt and made of stacked segments, while a harmless snake’s tail tapers to a point, though a rattlesnake that has lost its rattle may lack the segments.
Cornered burrowing owls and their chicks make a hiss whose sound pattern resembles a rattle.31PubMed Central. Avian hissing sounds: occurrence, mechanism, ontogeny, function and phylogeny Mammals competing for their burrows react to it with caution, as if to a snake.32PubMed Central. Avian hissing sounds: occurrence, mechanism, ontogeny, function and phylogeny That makes the owl’s hiss a true sound imitation of rattlesnakes.33Ethology. Rattlesnake Rattles and Burrowing Owl Hisses: A Case of Acoustic Batesian Mimicry
Insects can fool you too. Cicadas drone loudly from trees or shrubs above ground level. Grasshoppers and katydids click and tick in bursts rather than one steady sizzle. If you can’t identify a buzz from ground level, stop and treat it as a rattlesnake until you’ve seen otherwise.
How Other Animals React to the Rattle
Animals show more fear of a snake with a rattle than of a snake alone.34PubMed Central. The multimodal display of rattlesnakes is a deterring signal that works best with sympatric species Animals from places with rattlesnakes react more strongly than those from places without.35PubMed Central. The multimodal display of rattlesnakes is a deterring signal that works best with sympatric species Experience with real rattlesnakes seems to teach animals what the buzz means. An animal that has never met a rattlesnake may not know to be afraid, so the sound works best on animals that have learned it.
That matters for pet dogs. A dog that has never met a rattlesnake may be curious about the buzz and walk up to it, putting its face and legs at risk. Keeping a dog leashed in snake country lets you pull it back the moment you hear a buzz. If rattlesnakes are common where you live, a vet can tell you what options exist and what to do if a dog is bitten.