Now is the perfect time for this discussion because the Effie Yeaw rattlesnakes have been shedding like crazy. Since the end of spring courtship about two months ago, the pregnant females have hunkered down to thermoregulate at optimum gestation temperature while the males and non-reproductive females have been hunting with far less attention to temperature control. All have been shedding over the past few weeks.
If you haven’t yet read my description of the shedding process near the end of my last post, do so now; the following discussion will make much more sense with that background.
Because the corneal layer of the skin does not grow, shedding (or ecdysis) is a recurring process throughout a scaled reptile’s life. Like other animals, baby snakes grow rapidly, so they must replace the corneal layer frequently to accommodate rapidly expanding bodies. Since shedding frequency is highly correlated with growth rate, juveniles usually shed several times per year. Growth rate and shedding frequency slows with size and age, with large adult rattlesnakes sometimes shedding less than once per year.
Rattle growth is a fundamental part of the shedding process for rattlesnakes. The rattle is made of keratin, the same stuff as the acellular matrix of the corneal skin layer – and your fingernails. Each time the snake generates a new corneal layer and prepares to shed the old one, it also produces a new rattle segment. Thus the newest segment is always at the base of the tail and contains live tissue – much like the base of your fingernail. And because each new segment is the width of the tail, young rapidly-growing rattlesnakes produce a tapered rattle (photo below).
The rattle is made up of loose, hollow, interlocking segments. Except for the first segment (or “birth button”), each segment consists of three lobes, yet only one is visible. The two hidden lobes fit loosely inside the older adjacent segments (photo, below). There is nothing loose inside that makes noise, the rattlesnake’s buzz comes from the loose segments vibrating together.
Rattlesnakes are born with a tiny hard cap on the end of the tail. I like to use the analogy of an eraser on a pencil – which is the approximate size of the newborn snake and the cap. During the first ten days or so, the first rattle segment or “birth button” is produced, which is uncovered by the postpartum shed. This is the only time that a part of the rattle comes off with the shed “skin.”
During every subsequent shed, the old corneal layer will simply be an open tube that slips over the rattle. When a shedding cycle begins, formation of the new rattle segment is usually noticeable before the eyes turn blue (photo, below).
Injecting acrylic paint into the first hollow segment allows me to identify rattlesnakes visually, with each animal receiving a unique color combination. The paint also allows me to record how often they shed.
In Female 05 (above), note that her birth button and the next two or three segments are already missing. The location of her original paint tells us that she has shed four times in the 40 months since she was first marked. The slight taper at the end of her rattle provides a hint of her age: considering the number of segments I think are missing and that snakes grow much faster and shed more frequently when young, I estimate that I originally captured her in her third or fourth year, making her about seven years old in this photo. Once all of the tapered segments at the end are lost, we have no way of estimating how old she is from the rattle.
You can also see that the rattle segments produced by Fem 05 (photo, above) as a young rattlesnake are noticeably larger than the more recent thin segments. This happens in the middle of rattles, too, with some segments being wide and robust while others are thin. I think rattle segments are a bit like tree rings in that good conditions with lots of food produce wider thicker segments. In the case of adult females like 05 above, it likely reflects the shift in resource allocation (more below) when she became sexually mature. It is worth mentioning that this snake had reproduced three years in a row when this photo was made (and she produced the four recent thin rattle segments) and her body condition was very poor after three consecutive litters.
In almost all rattlesnake species, adult males are larger than adult females. Yet the growth rate of baby males and females is indistinguishable until they reach sexual maturity. Once they start reproducing, however, female growth slows. We believe this happens because females start diverting most nutritional resources to the production of offspring, leaving much less available for their own growth. Males, on the other hand, are free to continue devoting their resources to increased body size – which is advantageous for fending off predators while searching for females and for battling other males for access to receptive females (click here for video of males fighting).
Finally, can we tell a snake’s age from the rattle? The one sure thing is that each rattle segment does not represent one year. The addition of rattle segments is well correlated with growth rate which, in turn, depends on age and food intake. We can make a pretty good estimate of age from a complete unbroken rattle and even when a few segments are missing, so long as some significant taper remains at the end. But for older snakes with broken rattles having no taper, there is just no way to know how many segments are missing.
So how long can rattlesnakes live? Decades! I have personally kept some southern California species in captivity over twenty years. The Splash Education Center at Mather Field has a healthy Northern Pacific Rattlesnake that has been in captivity for a well-documented 32 years! But how long they survive in the wild is a much different question. Captive snakes do not have to contend with coyotes, hawks, owls, king snakes, temperature extremes, and all the other hazards of a natural existence – not to mention humans and their cars. While references like Robert Stebbins’ Field Guide to Western Reptiles and Amphibians (2003; Houghton Mifflin Co.) list the maximum size of our northern California species as over five feet, the fact is that three-footers are now uncommon. Large rattlesnakes have become very rare all over the United States, with individuals approaching old record lengths almost never found. Of course, in some remote wilderness where people rarely visit (if there is such a place today!), maybe there are still a few very large wild rattlesnakes…
We have property in Hawk Creek Canyon, Lincoln County, WA. In July 2016, we found a western rattlesnake between our cabin and the creek that we (carefully) estimated to be between 45 and 48 inches long, about 2 inches in diameter. It had the button, seven hollow rattles, and the dark new rattle. My son-in-law, a biologist, thought it was in its third or fourth year, but was not certain. We try not to bother the rattlers, they kill gophers and mice, and we appreciate them. …But a big one, just 20 feet from the cabin, was a bit much.
We captured it, put it into a garbage can, and transported it a few miles up the road, where we released it. Knowing how far they can travel, he may be back next year. I have a few pictures of it, but don’t know how to post them here.
Hi Jim. Wow, rattlesnakes must grow fast in Lincoln County! You have the same species of rattlesnake as we have here in northern California (Crotalus oreganus) and a nearly four-foot animal would be the largest I have seen. Yet your son-in-law’s estimate of age is probably right in the ballpark for a rattlesnake with an unbroken rattle of nine total segments. The good news is that, at that size, the snake is almost certainly a male and males tend to wander widely, rather than hang around in a small area… like around your cabin! Here and farther south, the males’ wandering is usually greatest during their courtship season which is in spring and late summer/fall, not in July. But I’m not sure how the courtship season might change at greater latitudes with shorter summers. In any event, thanks for carefully moving him rather than killing him. There’s an excellent chance that you’ll never see him again.
So a rattler with 22 rattles could be how old? It’s 9 feet long, too.
You really cannot tell a rattlesnake’s age from its rattle. The exception is young rattlesnakes with a tapered unbroken rattle, which allows for a good estimate of how old they are. They produce a new rattle segment each time they shed the outer layer of their skin and the frequency depends on how fast they are growing: more frequently when young and growing fast and less often when old, large, and not growing much. They almost always shed more than once per year, so the old “one rattle segment per year” idea is not accurate. The rattle grows from the base and big rattlesnakes invariably have broken off the tapered part of their rattle, which means we have no idea of how many segments have been lost when we encounter these big guys. By the way, nine feet is a record-length rattlesnake of any species!
Hi there, asking if there is a ‘rattle skin’ left behind when the snake sheds. In Terlingua, Texas we recently found a 3′ rattlesnake skin and it looked like there was a part for the rattle.
I do have a pic but not sure how to attach.
Thanks!
Julie z.
Hi Julie,
Except for the first natal shed that occurs about 10 days after birth (when the snakes are the size of pencils), the tail end of the shed “skin” from a rattlesnake is just an open tube that slips off over the rattle. If an adult rattlesnake’s rattle is damaged or deformed, I suppose old rattle segments could come off with the shed skin as the snake crawls out of it. I have never seen that but the old dry rattle segments routinely get brittle and cracked, allowing them to fall off or be broken off. I don’t know why this could not happen during the shedding process but the rattle segments would not be actually attached to the shed skin.
Mike
Is that how you tag a rattlesnake by putting paint on it rattle
The paint in the rattle allows me to easily identify a rattlesnake visually that I have captured before. A rattle without paint signals an animal I have never captured and processed. Each animal that I process for the study gets a unique color combination of acrylic paint harmlessly injected into a hollow rattle segment.
But to be able to repeatedly find rattlesnakes to study them, I surgically implant a small radio transmitter into their abdominal cavities. The battery lasts a year and the radio must be replaced annually but the signal allows me to find the radio-tagged animals any time I wish. I only have radios in twelve rattlesnakes currently, due to the time it takes to find the that many snakes and record data.
In short, the rattlesnakes are “tagged” in different ways. I now have about 50 Effie Yeaw rattlesnakes marked for visual identification with paint in the rattles and twelve of those are also implanted with radios that allow me to find them frequently.
Mike
I saw a wee snake at a park near our home–about 12″ in length–and it had the patterning of a western rattlesnake, as well as the triangular head shape, but could see no evidence of a rattle. When I looked at a photo I took of it, on the shadow of its tail I did see a slight bulb-shape at the tip. I would post the photo here but I guess this comment section isn’t set up for that.
I was taught (and have observed) that c. Atrox (western diamondbacks’) rattles were straight and c. Viridis (prairie rattlers’) rattles were tapered. Is this a myth or is the tapered rattle = young snake only true for the species you study?
Hi Jerry! Sorry for the late reply… too much spam to sort through. Tapered rattles indicate young snakes in all rattlesnake species and straight rattles are older snakes. The reason is that a new rattle segment forms at the end of the tail each time the snake sheds the outer layer of its skin. Thus, each new segment is the same width as the tail. So small rattlesnakes produce narrow segments and larger rattlesnakes produce wider ones (because the tail is bigger). And like other vertebrates, young rattlesnakes grow rapidly so each rattle segment is a little wider that the one before. Big older rattlesnakes grow very slowly or not at all, so rattle segments are the same width. The rattle is made of keratin, the same stuff as our fingernails, and the older segments get dry and brittle and eventually break off. Over a few years, the snake loses the tapered part of the rattle it produced when it was small and growing rapidly, leaving only the more recent larger untapered segments. I hope that makes sense… it’s really a simple process and it’s the same across the various species. Best wishes, Mike
Any idea what the record is for tapered, fully intact rattles?
My father shot a rattlesnake back in the 50’s, Mohave Desert, so probably a Western Diamondback, and I have the rattle section. It is in great condition, 33 rattles, no joke. Would post a pic if you have an upload link.
Hi Donna,
I’m not sure anyone keeps track of the longest accumulated string of rattles but 33 is certainly very unusual, especially for a wild snake. In my experience with wild rattlesnakes, 10-12 segments is a long rattle. Captive snakes frequently accumulate longer rattles because they are less active and don’t have the vegetation, rocks and rodent burrows to crawl through that are probably responsible for rattle breakage in wild rattlesnakes.
Have a Prairie Rattler with 32 rattles and a button. Is this a record?
Probably not a record for a captive rattlesnake… See my response to Donna below.
When I was a child born dec 1966 we moved to the foothills of a mountain near my grandparents. My father and grandfather killed 8 rattlers the first summer in fields near our home. The largest one had 22 rattlers and a ” button” I carried those 22 rattlers around w me for a couple of years until I somehow lost them. Including to my Headstart programs “Show and Tell” but the teacher didnt get to me that day and I never showed her as I was a shy child. My first experience w death was a small kitten my grandmother gave me. It had 2 fangmarks in its side and was underneath the doorsteps of our rural home. The snakes diameter was described by my father as “large as his upper leg” (he weighed about 170) and the snake was longer than 8 ft possible close to 9 ft. I have always wondered how old that snake was. Any estimates you could give me? I was about 5 years old then and would wake up at night see a shadow or an object on the floor and be so afraid I would barely exhale instinctivly knowing it would sense my presence if I breathed only to have daylight show that it was my imagination not an actual rattler in my room. Any estimates on its age would be appreciated. Thank you, Amanda
Hi Amanda. Very large rattlesnakes are undoubtedly several decades old. We know that rattlesnakes can live well over 30 years in captivity and a colleague of mine recently documented the survival of a male Timber Rattlesnake (Crotalus horridus) in the Appalachian Mountains nearly 50 years after he first marked and released the animal.
Mike,
I recently had a friend that killed a large timber rattler on his property in Ashland City, TN. it measured in at 6 1/2 feet long and had 12 rattles and a button, he contacted TWRA before killing the snake to make sure it was okay. I hate that he decided to kill it, but he has three young children and was concerned about them of course. I thought the TWRA would have came and caught it and released it somewhere safe instead of allowing him to just kill it, they informed him that the timber rattlesnake is on the endangered species list in Tennessee, but if the snake is a threat to people or livestock then that would be an exception. I am not sure of the diameter of this snake, but judging from the picture he took it looks to be around 12 to 15 inches and it also had long course black hairs coming from the tail as well, I’m curious to how old this snake might be and is this common to have the black hairs on it tail?
Hi Michael,
Sorry for the delay, with the study field work complete, I check the website pretty seldom now. A 6.5-foot rattlesnake is a big rattlesnake, indeed. If it still had its “button,” it could not have been more than a few years old. But good genes and lots of available food work wonders. Timber Rattlesnakes are known to live to nearly 50 years and likely beyond in remote areas with good cover – although old snakes lose their birth button in less than a decade. Regarding hairs on the tail, that’s beyond unusual – actual hair is a trait peculiar to mammals. Maybe tattered remnants of an old incompletely-shed skin? That’s my best guess! Mike
Was out hiking today at Descanso Gardens near Los Angeles, saw a diamondback I would estimate 4′ – 5′ long from how much of the trail it took up. Biggest one I’ve seen in the wild, but the gardens have a good population of squirrels and rabbits. Dec 2016 I found a young (1~1.5 foot long) one maybe a quarter mile farther down the same trail, and it got me wondering. How long would it take a hatchling to reach 5′, assuming a consistent food supply?
Hi Caitlin,
Sorry for the late reply; this site is inactive now and your question was buried in a ton of spam.
Rattlesnakes are born alive in late summer or early fall, usually around September in southern California. Southern Pacific Rattlesnakes, the only species in the L.A. basin, are about 9-10 inches long when born. Given optimum conditions (lots of food and water, long warm (not hot) summers, and avoiding owls, coyotes and people), I would guess that a wild Southern Pacific might reach 4-5 feet in as many years. Like other animals, they grow rapidly when they’re young but growth slows as they get bigger. They probably get to three feet in the first year or two, then take much longer to add another two feet. The one you saw is about as big as that species gets. True diamondbacks can get larger but they are not found in LA County.
I hope that helps!
Mike
Hi Thalia,
The rattle consists of dry hollow loosely-interlocking segments that make the buzzing sound as they vibrate together when the snake shakes its tail. Baby rattlesnakes instinctively shake their tails when they feel threatened, beginning very shortly after birth, but they cannot make any sound for the first few weeks or months because they have only one segment. But as they grow, all snakes must “shed” the outer-most layer of their skin periodically and each time this happens, rattlesnakes add a new segment to the rattle. So, as soon as a young rattlesnake adds a second rattle segment, it can make some noise because it then has two segments to vibrate against one another. But two segments don’t make much noise. As the snake continues to grow and shed, it adds additional segments and the resulting buzz gets louder as the rattle gets longer. I hope that answers your question!
Mike
April 13, 2019 – Mt. Hamilton Road……I encountered one of those Indian fakir moments: two rattlers doing what I suppose was a mating dance…really groovy; only lacked the background oboe sound. It this a normal action? From the photos, I can count 7 rattles (if you would be interested, I can e-mail a ‘proof’ picture). The several pictures were taken by my passenger while looking down from the open window. Those snakes only glanced at us; then, went back to their get-acquainted dance.
Hey Stan, the first time I saw dancing rattlesnakes, I was a teenager and assumed they were a mating pair. But as my knowledge and understanding of rattlesnake behavior improved, I learned that such “dances” are actually male combat – two males fighting over access to a nearby female. It’s all a wrestling match; no biting involved. Congratulations, witnessing that behavior is not a common event, even for those of us who spend a lot of time studying wild rattlesnakes! Best wishes, Mike