Snakes are flexible and can squeeze through tight gaps to escape from predators or to hunt prey. So, given how elastic they are, you might assume that snakes don’t have bones.
This guide covers everything you need to know about snake skeletons. You’ll also find out how many bones a snake has and each of their different functions.
- 1 Do Snakes Have Bones in Their Body?
- 2 Snake Skeleton Facts
Do Snakes Have Bones in Their Body?
Snakes are vertebrates. They have both bones and cartilage.
Their bones give them structure and defense for the essential internal organs, which are vulnerable given their length and inability to protect themselves with their arms and legs as we can.
Given that they’re so flexible, you could be forgiven for wondering are snake bones made of cartilage? They aren’t. They’re the same material as our bones.
How Many Bones Do Snakes Have?
Snakes have a lot more bones than humans. The only difference is that whereas we have a variety of bones, snakes have far more ribs—which makes sense when you think about it.
A paper published by the Royal Society caught and measured dozens of snakes, including boas and pythons, and looked at how their length correlated to how many vertebrae they had. They found that the longer the snake, the more vertebrae it had.
They found that:
- One python they caught had almost 450 vertebrae. Including the snake’s ribs and skull, this snake would have had around 1200 bones.
- Most pythons were between 7 and 9 feet and had around 300 vertebrae on average. These snakes would have had around 850 bones.
- Most boas that they caught were around 5 feet long and had 250 vertebrae on average. These snakes would have had around 700 bones.
Some of their vertebrae—the ones in their tail—don’t have ribs, but all the others do. For reference, we only have 206 bones. Each of our hands has 27 bones, and each foot has 26 bones. That’s more than half of our bones in just our hands and feet alone.
Snake skeletons, by contrast, are about 70% ribs. They don’t have hands, arms, legs, and feet. They don’t even have shoulder blades, and most snakes don’t have hips either. It just has ribs all the way down.
Do Snakes Have Skulls?
Snakes most definitely have skulls. They’re different from the skulls that humans have, though, which is mostly down to how they eat their food. As you know, snakes have to open their mouths incredibly wide to eat their food whole.
That’s how they can eat prey that’s one and a half times the size of their head (almost like you eating an entire watermelon in one go). As such, snake skulls have more moving parts than ours.
So, do snakes have jawbones? They have two long jawbones that run along the length of their skull, in the normal position. But these two jawbones aren’t connected by a chin like ours are.
There’s nothing there to connect them, which means that they can stretch their jaws out to fit prey that’s bigger than their heads.
Do Snakes Have Hips?
Even though they don’t have legs, some snakes do have rudimentary hips. You can find them on primitive snakes, which are snakes that are similar to their ancestors from millions of years ago.
To understand what hips a snake has, you have to know what the individual bones themselves are called. The largest part of the hip bone is the ilium, which is the big, round part on each side.
These are the bones you can feel when you put your hands on your hips. Lower down is the ischium which you sit on. This is the acetabulum which connects to the legs, and the pubis which connects to our muscles. All of these bones aren’t really ‘bones,’ but are one big hip bone.
Boas and pythons have basic hips that they don’t use. They have an ilium that’s long and stretched out. It’s attached to their spine like our hip bones are.
Most blind snakes have a complete hip bone like ours, with an ilium, pubis, and ischium. Other species of blind snake have two single bones on each side.
Do Snakes Have Legs?
No, but some species have tiny remnants of the legs that their ancestors had, called vestigial hind legs or pelvic spurs. Again, you’ll only find them on primitive snakes.
Boas and pythons both have vestigial hind legs. They appear as tiny spurs on the snake’s tail, next to their cloaca. They aren’t attached to the skeleton.
Today’s snakes use them in many ways. Of course, they don’t use them to walk. But male boas, for example, use theirs both for fighting and for holding onto females while they mate.
If you look back in the fossil record, you can find evidence of snakes that had developed hind limbs. An example from Live Science is a recently discovered species, Najash rionegrina, that lived around 90 million years ago.
Scientists had thought that snakes had emerged from the water without legs, and had previously been animals like eels. However, this snake was aquatic, but still had hip vertebrae as well as developed and functional legs.
Today’s snakes are descended from snakes just like these. But over millions of years, since they haven’t needed them, they’ve gradually gotten rid of their legs for good.
How Do Snake Bones Work?
Snakes seem to move effortlessly along, no matter what surface they’re on. Their sleek and steady movement almost gives the impression that they’re entirely fluid, with no bones at all, which explains the common misconception that they don’t have any. So, how do they manage to glide and slither along like they do with a full skeleton?
It’s all in the muscles. The muscles between their ribs and the muscles over their ribs move in synchronicity so that they can move. Their ribs come closer together on one side and move further apart on the other side so that they can bend in the traditional S-shape that a snake uses to move.
If you’ve ever wriggled through a pipe or anything like a waterslide, it’s a similar kind of movement to that. It’s just that snakes are much better at it.
These are the same muscles that constrictors use to tighten around their prey. When they constrict, the snake’s intercostal muscles—the muscles between their ribs—tense up so that they can protect their own body from the pressure they’re creating.
According to the Journal of Experimental Biology, enormous reticulated pythons can create a pressure of almost 8 lbs per square inch relative to atmospheric pressure, so they protect themselves using their intercostal muscles and ribs.
Can Snakes Break Bones?
They most definitely can, for all the same reasons that human bones can break. Their ribs are relatively thin, and they have a lot of them, so they can easily break. However, snakes in the wild don’t often encounter situations where they might break their bones, like falling from a height.
In captivity, there’s more of a risk that they might break a bone. It might be when:
- You hold them too tight when you’re handling them
- You accidentally drop them when you’re handling them, which can easily happen if you’re handling a snake other than a constrictor
- Something drops on the snake from a height
To spot where a snake has broken bones, the first thing you should look for is their reaction. They’ll be more nervous or defensive than usual, for a start.
You may also notice that they’re wary of or resistant to handling. Aside from that, look for bruising and swelling. Dark bruises are quite hard to spot on darker colored snakes.
The good news is that since snakes are so flexible, and have strong muscles, it’s quite rare for them to break a bone. If you suspect your snake may have broken a bone, you should perform an initial check to search for bruises and injured areas.
If you think they may have a broken bone, even if you’re not sure, take them to a vet.
Snake Skeleton Facts
Snake skeletons are complicated, refined machines. Let’s look at a few little-known facts:
Snakes Don’t Dislocate Their Jaws
It’s a common misconception that snakes dislocate their jaws to eat their prey. They don’t, and in fact, they couldn’t—because their jawbones aren’t attached to their skull by joints, so there’s nothing to dislocate.
Like we said above, snakes have two separated lower jaw bones. By stretching their lower jaw out, they can eat large prey items in one go. Not only that, though, but their upper jaw bones can do the same. There isn’t a direct connection between their upper jawbones and the skull itself (the skull being the part that holds the brain and nothing more).
Neither are their upper jaw bones attached to the lower jaw bones. This means that snakes can make their jaws incredibly wide both horizontally and vertically.
Not only that, but their snout can move independently too, allowing for even more room when they eat something big.
Snakes Can Expand Their Ribcage
In humans, our ribs are connected in two places. These are the vertebrae at the back, and the breastbone at the front. The ribs, therefore, form a full cage, without any gaps (except those between the ribs, of course).
Snakes don’t have a breastbone. Their ribs are attached to their spine, of course, but they don’t have a breastbone in their belly. While they’re more vulnerable on the underside, it’s still advantageous.
It means that when they eat a large meal, they can expand far more than we can to accommodate whatever they’ve eaten. That’s why big snakes like reticulated pythons can eat small bears, deer, and other impressively large prey.
Having such a flexible ribcage also means that they can shrink and squeeze themselves through tight gaps. Their organs are already squashed and elongated compared to ours, and the fact that they don’t have a breastbone means that they can draw in their ribcage, making it thinner and smaller. This helps them escape predators by hiding in tiny spaces or hunt for rodents in burrows.