There are two popular myths about turtle shells. One says that turtles can slip off from their shells. The other myth claims that turtle shells are unbreakable. I have debunked the first myth in one of my posts, and now, let’s talk about the turtle shell strength.
A turtle can carry up to 1000 pounds (almost 200x of its own weight) on the shell. The endurance limit depends on the turtle’s size, species, posture, and health. Again, the fracture toughness of a turtle shell is 65 MPa. m^½, higher than many natural materials.
Find the secret behind the turtle shell’s hardness and strength in the article below.
- Turtle shells are not unbreakable.
- The shells can carry up to 1000 pounds. This weight limit depends on the turtle’s physique.
- A Turtle shell’s fracture toughness is 65 MPa. m^½. Likewise, the tensile strength ranges from 19 MPa to 52 MPa, and the compressive strength is 100 MPa.
How Much Weight Can A Turtle Shell Withstand?
Experimental values conclude that a turtle shell can handle forces 200 times its own weight. For example, an 8 – 12 inch turtle can withstand up to 620 pounds of equivalent weight. You can increase the pressure up to 1000 pounds and sometimes even more.
The bearable amount of weight actually depends on several factors. For example, if your turtle is sick, it will have a low endurance level. Likewise, a pet suffering from MBD or calcium deficiency can not handle a large load.
How Strong Is A Turtle Shell?
What is the hardest material you know? Diamond, right? But here is one thing about diamonds.
They are brittle and can not carry much weight. So, if you put enough load, the diamonds will break into pieces. It means we can not call it strong! This also shows that hardness and strength are two separate factors.
Experts say the most useful parameter to measure a turtle’s shell strength is fracture toughness. In simple words, it is the energy required to form and propagate a crack into the object.
The experimental results show that the fracture toughness of a turtle’s shell is 36 MPa. m^½. This value is much higher than diamond (2 MPa. m^1/2 ) and aluminium (22 MPa. m^½). In fact, turtle shells are stronger than many low-carbon steels (12 MPa. m^½).
Well, the hard shell benefits turtles in many ways. For example, the shells act as a safe space for these reptiles. You will catch them retracting into the shell when stressed or in danger.
Luckily, turtles can avoid a hard blow on the shell because of the high fracture toughness. But then again, these shells are not unbreakable. Falling from the height or a high pressure can puncture the scutes or crack them open.
This is why the wild turtles mark crocodile, alligator, and honey badger-like predators as red marks. These animals have sharp jaws, and they can bite with immense force. Hence, a collision with these predators will surely damage a turtle’s shell.
How Hard Is A Turtle Shell?
Turtle shell hardness varies with species. For example, the maximum tensile strength of the carapace and plastron can withstand ranges from 19 MPa to 52 MPa.
Tensile strength is the pressure an object can support when stretched. You can compare this value with the tensile strengths of wood (40 MPa) and glass (52 MPa).
Now, if we talk about compressive strength, it is not more than 100 MPa for a turtle shell. Similarly, the bending or flexural strength for the carapace and plastron is 165 MPa.
Are you getting confused? Let me put these values in simple terms.
See, turtle shells are hard. The interior layer can withstand almost 40 MPa, while the exterior may bear 28 MPa. These values are impressive and higher than most naturally occurring materials. Yet the shell will break when you stretch out the scutes or add a huge compressive load.
What Can Break A Turtle Shell?
So, clearly, a turtle shell is not unbreakable. The creature can get a damaged shell when it runs into an accident or falls sick. Here are some common reasons for a broken shell,
1. Predator Attack
Not all predators can damage a turtle’s shell. The animal must have a sharp jaw that can penetrate through the shell.
Crocodile and alligator attacks can crack open a turtle’s carapace and plastron. These animals can generate 3000 to 5000 psi force on the turtle’s shell. The concentrated pressure will puncture the hard scutes.
Honey badgers may not have a bulky body. But they have sharp teeth to scratch and even crack a turtle’s shell. These animals have a biting force of around 1100 pounds.
Likewise, whales and sharks are dangerous predators for the sea turtles. The bites of these mammals can be deadly for the marine turtles.
Surprisingly, birds can also damage a turtle’s shell. There are video proofs featuring a bird flying with a small turtle. The bird will eventually drop the reptile from a height to crack open the shell. Only this way the bird can enjoy the flesh of the turtle.
2. An Accident
Sometimes, turtles run into accidents that can cause fractured bones and shells. For example, running into a car or falling from a height will hurt their shells.
I have talked a lot about metabolic bone diseases on my blogs. Because of this condition, turtles experience a soft, fragile, and deformed bone or shell. Calcium and vitamin deficiencies are mostly responsible for metabolic bone disease.
Turtles need calcium and vitamin D3 to build a solid bone and shell. So, the lack of these minerals will negatively affect the shell and bone growth. In fact, this condition makes the shells so fragile that they become prone to fracture.
What Makes A Turtle Shell So Strong?
Turtle shell has an interesting structure, which provides it strength and hardness. For the starter, the main component of the carapace and plastron is keratin. This makes the shell tough and scratch-resistant.
Secondly, the turtle shell is not a single surface. Instead, it contains 13 plate-like scutes connected. It means when you put pressure on the shell, it gets distributed on each scute.
Finally, when you go deeper, you will notice bones and the ribcage are fused to the plastron and carapace.
In short, advanced engineering and strong materials are the secrets of the turtle shell’s strength.
Frequently Asked Questions
Before You Go…
Turtle shells are undoubtedly strong. But what about the tortoise shell? Get an insight into the engineering and strength of tortoise shells from the attached link.