A tortoise shell forms while the baby tortoise develops as an embryo in the egg. A hatchling will enter the world with a shell, which will get bigger as the baby tortoise increases in size.
Despite what pop culture suggests, tortoises can’t leave their shells as it would kill them. So, their protective shell needs to grow with them.
When tortoises hatch, they’re born with the shell they’ll have for the rest of their lives. Factors such as nutrition and living environment play a vital role in the condition of the shell and how it grows.
Do Tortoises Shed Their Shells?
Tortoises shed their skin regularly to allow for growth as juveniles. Although they shed more in their youth, adult tortoises will shed throughout their adult lives to:
- Rejuvenate their skin
- Accommodate growth
- Maintain a strong shell
While most shedding occurs on the skin, tortoises also shed the outer layers of their shells. These are known as scutes, or the segmented plates covering the outside of a tortoise’s shell.
Rather than everything coming off all at once, like a snake, they shed in patches and flake frequently during the shedding process. This gives the tortoise the room needed to grow new skin and a bigger shell, which tortoises do every few months.
Do Tortoises Lose Their Shells When Shedding?
Tortoises aren’t like hermit crabs, which leave their old shells in search of better, stronger shells.
Instead, tortoise shells are fused to their skeleton, preventing them from ever removing their shells. The shell they have upon hatching is what they’ll have for their entire lives.
Since tortoise shells are attached to their skeletons, they can’t shed their shell. Bits of keratin may flake off occasionally as the tortoise grows, which is a form of shedding.
When Is Shell Shedding Bad?
The flaking of keratin is a natural part of tortoise growth. However, sometimes tortoises shed too much, removing some healthy tissue. This issue can be caused by the following:
- Metabolic Bone Disease (MBD)
- Malnourishment
- Dehydration
- Injury and trauma
Tortoises rely on their skin and shells to protect them from injury, hold water, and avoid diseases. The only time it’s unsafe for a tortoise to shed is when its tissue is compromised.
How Do Tortoises Grow Their Shells?
Tortoise shells are comprised of three layers of different materials:
- Bony inner plates
- Hard scutes
- Epithelial cells
The most visible part of the shell, the carapace, is covered in scutes.
These plates are made up of many layers of keratin. This ensures they’re in a constant state of growth so that the tortoise can generate new scutes every few months or years.
As the tortoise grows, new layers of keratin are added to the base of the scutes. This gives tortoise shells a tree-ring look with a unique texture and shape.
Each shell looks different depending on the tortoise’s breed, age, size, and health.
How it grows will be similar for all tortoises. Shells, like bones, take time to grow. During growth periods, all three layers that make up the shell expand, adding new material to the shell.
Egg Stage And Hatching
Like most creatures, tortoise development starts with fertilization. This transitions to the embryo stage, where the baby and its shell continuously grow over the course of 100-160 days of incubation.
There are several stages to tortoise development. At around stage 16 or 17, the carapace begins to form. This is the hard upper layer of the shell, which will do the most work defending the tortoise from harm.
Once hatched, the shell of the baby tortoise will be soft because it’s still developing. It’ll harden gradually in the following weeks, taking 1-5 years to fully harden.
From here, the shell will continue to grow throughout the tortoise’s life.
The shell will cease growing once it reaches the maximum width of the tortoise. However, it’ll still be prone to shedding, as the tortoise must renew the shell regularly.
Adulthood
Since the shell is fused to the skeleton, tortoises benefit from extra calcium and minerals. Calcium not only helps tortoises maintain strong bones but also strengthens their shells.
Growth varies between species, as does the amount of time it takes for that species to be fully grown.
Leopard tortoises are usually fully grown in a year, whereas sulcata tortoises are fully grown in 5 or more years, depending on the tortoise, care, and other miscellaneous factors.
According to the Journal of Zoology, the growth of tortoises can differ between males and females.
Females tend to be larger than their male counterparts. The species also play a role in how big a tortoise will grow. For example, sulcata tortoises grow much larger than red-footed tortoises.
Nonetheless, both males and females shed their shells at certain points. For some, it may take longer or happen at more infrequent intervals. Even still, shedding is a vital part of growth and life.
How Fast Do Tortoise Shells Grow?
Shells grow along with the tortoise itself, as the shell is vital to the skeletal system. The rate the tortoise grows depends on factors such as:
- What it eats
- Level of food consumption
- Enclosure
- Living environment
The growth rate also depends on the tortoise species because some species grow faster than others.
According to the University of New Mexico, annual measurements of the various North American tortoise species showed how environmental changes, like rainfall, affected the growth of the tortoise shells.
Below is the average rate that different species grow from hatchling to adult:
| Species | Average Adult Size | Grow Time to Adult |
| Horsefield Tortoises: | 5 to 8 inches | 10 Years |
| Red Foot Tortoises: | 10 to 18 inches | 10 Years |
| Leopard Tortoises: | 10 to 18 inches | 12 to 15 Years |
| Sulcata Tortoises: | 3 to 4 Feet | 15 to 20 Years |
Tortoise shells grow much like human fingernails and bones. Shells grow gradually with the tortoise throughout its life, averaging several extra inches per year.
Tortoises never shed their shells, so they grow with them from embryo until adulthood.
