Years of cartoons and comics have convinced us turtles can hop in and out of their shells in a blink of an eye. Is this really possible? And are turtles born with shells, or do they grow them later on?
If you’ve ever watched a documentary on sea turtles laying their eggs on the beach, you would know that all turtles are born with shells. They hatch from their eggs with their shells already firmly attached to their bodies. These shells are hardened by exposure to air and will grow along with the turtle’s body until it reaches maturity.
So how exactly does this work? When do turtles start growing their shells, and how can a shell grow along with a living organism? All this, along with what turtle shells are made of, why turtles need them, and whether or not a turtle can survive without its shell, are answered in the article below.
How are Turtles Born with Shells?
The most important factor to note when trying to understand how turtles are ‘born’ with shells is that they are hatched, not born.
Similar to most reptiles and amphibians, female turtles lay eggs on land. This is usually done on the beach. A female turtle will dig a hole in the sand, lay her eggs, and then cover them up again.
The baby turtles in these eggs already have their shells, but not in the exact same form as they would when they mature. While still in the egg, and for several days after hatching, a baby turtle’s shell will be a much softer, more pliable version of the one it will have as an adult.
How can a Baby Turtle’s Shell be Soft?
Similar to the way a newborn baby’s skull is soft to facilitate an easier birth, turtles’ shells are soft to ensure the eggs they are in can be passed from the female without issue.
Compared to tortoises, a sea turtle’s shell may feel softer and slightly leathery. This is because it spends most of its time in the ocean.
As a baby, however, most of any turtle’s shell will be made of keratin. Yes, keratin, the same thing your nails and hair are made of! That’s why a baby turtle’s shell is so much bendier than an adult’s.
As they grow and mature the layer of keratin gets thicker and so do the dermal bones forming part of the shell. This makes the turtle’s shell much harder and stronger.
We will learn more about what a turtle’s shell is made of further into the article.
Why do Turtles Have Shells?
Most cartoons we watched as kids would show a turtle hopping in and out of its shell with as much ease as you’d remove a bike helmet. This led many to believe a turtle’s shell is simply his house. It’s where he goes to sleep, or where he hides when he doesn’t want to be bothered. The truth is much more interesting than this. [Source]
Here are the main reasons why turtles have shells;
Probably the most obvious reason a turtle has a shell is to protect itself.
Not entirely different from the bike helmet theory mentioned earlier, the hard layer of shell around a turtle’s body protects them against predators as well as the bumps and bruises they may get throughout their lives.
A turtle’s shell encloses and protects most of its vital organs. It also provides a pretty good hiding spot for its head and limbs if it feels threatened.
Scientists have often debated the real reason why turtles developed shells in the first place. For many years it was believed this was only for protection but now they have finally discovered the original reason for turtles growing shells was for burrowing.
This might seem strange since sea turtles don’t spend much of their time on land, but it makes sense when you study their earlier habits, as well as that of tortoises.
Ages ago turtles burrowed in river banks when they needed to rest or lay their eggs. Most scientists now agree that the main reason they developed shells was to have an anchor for their front arms when they were digging. This anchoring point enabled them to powerfully pull their arms back and dig holes faster and deeper than before.
For Smoother Movement
As mentioned above, many sea turtles have smooth, leathery shells. This slippery shell makes it much easier for the turtle to move around in the water.
The smoothness reduces the friction between the water and the shell and allows the turtle to move with greater ease.
For sea turtles, swimming requires almost exactly the same flipper movement as burrowing or digging would. It makes sense, then, that the same turtle shell that provided an anchor to strengthen a turtle’s arms when digging would enable it to have much more powerful strokes when swimming.
This development allowed turtles to thrive in underwater environments, and to become some of the strongest swimmers of the reptile world.
Turtle shells aren’t only made of keratin, they’re made of bone too! These bones help sea turtles float around underwater without popping to the surface or sinking all the time.
That’s why sea turtles look so much more comfortable moving around in water than they do on land.
For Absorbing Heat
Most turtle shells are dark. Their colors range from nearly black to dark green, and almost everything in between.
Dark colors absorb heat more readily than light colors, which are prone to reflect it. Since turtles are cold-blooded reptiles, absorption of heat is incredibly important to them.
For sea turtles, water isn’t the best place to warm up, so having a shell that absorbs heat is of great benefit to them.
Another reason light absorption through a turtle’s shell is so important is because it is the only way the turtle can synthesize Vitamin D, which is necessary for bone and shell growth.
For Prevention of Infections
Beneath a turtle’s shell lies its organs. These organs form part of its digestive tract, respiratory system, and nervous system, amongst others. Without a shell, all the organs a turtle needs to survive would be in danger of injury and infection either by fungus or bacteria.
The shell acts as a seal, preventing any bacteria or fungus from reaching these vital organs and causing an infection which could result in severe illness or even death.
When do Turtles’ Shells Develop?
Since turtles hatch with their shells intact, you may be wondering when exactly do they grow them?
In the stages of embryonic development, shell growth begins around Stage 14, or between 20 to 30 days after the embryo is formed. At this point, the shell may just look like a rather awkward bulge, but it quickly grows into a far more easily recognizable shape.
From What is a Turtle’s Shell Made?
Turtle shells are more complex than you may imagine. Instead of being a ‘shell’ in the literal sense, it actually forms part of the turtle’s skeleton.
The ‘shell’ is made from two main parts, the upper carapace, and the lower plastron. They are fused to each other at points along their sides called a bridge.
Inside the shell, there is a layer of skin that fuses the turtle to its shell. It is the main reason why turtles can’t climb out of their shells like they do in cartoons.
Each of these parts of the turtle’s shell is unique and specially modified to help the turtle survive. Below we discuss them in detail.
This is the most easily recognizable part of a turtle’s shell – its rounded top. It is believed it was originally formed by the turtle’s ribs widening, expanding, and eventually fusing together.
The bumpy part of the outside of the shell is made up of scutes. Scutes are layers of shell made of keratin that protect it from scratches and scrapes.
Not all turtles have scutes, though. Some, like the leatherback sea turtle, have an outside layer of skin instead.
The plastron is the flat part of the shell we might call the turtle’s belly.
Similar to an exoskeleton, the plastron is made of 9 bones amongst other components. The plastron also has scutes, although they do not look the same as the ones on the carapace.
If you want to understand why turtles are born with their shells, it is important to understand what their shells are made of. Since the shell forms a part of the turtle’s body, you can understand why they must be born with one and cannot simply grow one at a later stage.
How does a turtle’s shell become bigger though? How does it grow to fit the turtle? In the next section, we explain it in the simplest way possible.
How Does a Turtle’s Shell Grow?
Since a baby turtle’s shell is so much smaller than an adult’s, you may be trying to understand how they grow.
Simply put, since a turtle’s shell is partly made of bone, it grows in the same way human bones would. As these bones become longer and larger, they create more space inside for the turtle’s body to grow as well. [Source]
The only parts of the turtle’s shell that don’t grow are the scutes. They eventually shed or peel off, an occurrence unique to water or sea turtles (not tortoises). The discarded scutes are then replaced by larger ones, and the growth process continues.
Can Turtles Live Without Their Shells?
Although there is scientific evidence that turtles once lived without shells, in modern times it is nearly impossible. [Source]
A turtle’s shell is part of its skeleton. Removing its shell would be like removing a human’s spine and ribs and expecting it to continue living.
Not only is the shell part of the turtle’s skeleton, but parts of its skin are fused to it too. It might seem like the shell is simply a ‘house’ or ‘suit of armor’ for the turtle, but the truth of the matter is its shell forms part of its body, and a very important part at that.
Shells are to turtles what skin and bone are to humans, so it easy to understand why it would be impossible for turtles to live without them.
Can Turtles Feel Through Their Shells?
A turtle’s shell forms such an integral part of its anatomy that any damage to it will cause the turtle to feel pain.
In fact, turtles can feel far more than just pain through their shells. They can even feel it when you’re touching them!
Since a turtle’s shell is made up of bone covered by scutes, and these bones have nerve endings, they can feel it when they are touched, scratched, or if they bump their shells against something.
Some sea turtles will go so far as to scratch their backs on pieces of coral, much like other land animals will do against a tree. A quick search on the web will provide you with endless numbers of videos where turtles are being scratched by their owners with a toothbrush or even just their bare hands. They seem to enjoy it as much as a dog enjoys being petted.
Although it is cute to see how sensitive turtles’ shells are, this sensitivity also exposes them to a lot of risks.
It is one of the reasons you should never pick up a baby turtle who has just hatched. It is also why the practice of painting a turtle’s shell, although it looks funny, is incredibly dangerous. Painting a turtle’s shell stops it from absorbing light to produce vitamin D. This eventually leads to the parts of the shell that were painted becoming weak and deformed.
Will a Turtle Die if its Shell is Damaged?
Luckily, as sensitive as a turtle’s shell may be, it is equally strong. If the shell is damaged and a minor crack or fracture occurs, there is a very good chance the turtle will survive and the crack will heal on its own.
If the injury is more serious, it may need to have its shell artificially pulled together by bonding material available from most exotic animal vets.
In most cases the turtle will also have to be provided with topical antibiotics as the biggest danger is not only the crack, but the extremely serious infections that could arise from it.
If proper care is taken, it is possible for the shell to heal completely on its own. It is even feasible for the shell to slowly start regrowing in extreme cases too.
Turtle Shells Help Us Identify the Type of Turtle
Just like the colors and patterns of other reptiles help scientists figure out where they come from, and which species they are related to, the colors and shapes of turtles’ shells help us identify them.
One of the simplest aspects that help us recognize different types of turtles is their color. An easy rule to remember is, the lighter the shell, the warmer the habitat.
As one of the main purposes for a turtle’s shell is light and heat absorption and darker colors increase the rate of absorption, it is pretty logical to deduce turtles with lighter shells come from places that are warmer and have more sunlight.
The shape of the carapace, as well as the colors and patterns on the scutes, are also identifying markers for most turtles.
Tortoises, who are turtles that live on land, have much rounder carapaces and are often much larger than sea turtles. Most sea turtles, on the other hand, will have smoother, almost leathery shells to aid their movement through water.
Through understanding the anatomy, growth mechanism, and importance of turtles’ shells, it becomes evident why baby turtles hatch with their shells already intact. It would be impossible for them to live without their shells, not only because they need it for protection, but because it is a part of their body.
Once this point is understood, it is simple to see that baby turtles will always have their shells by the time they hatch. It’s not a house or piece of armor that can be removed and put back on at leisure. It is sensitive to pain, it can be damaged by infections, and it can heal again by itself all because it forms an integral part of their bone structure. A shell is as essential to a baby turtle as a spine and ribs are to a newborn baby.
Besides this, a turtle’s shell plays a vital role in its survival for more than one reason. It is there for protection, for aiding it in its daily life, and to give it the ability to survive when many other animals might not.
It’s no wonder that all turtles, no matter how young, are equipped with this special shield from the very first day they emerge from their eggs.