A tortoise’s shell is its primary means of defense, reflecting its state of health. It comprises a carapace (top) and a plastron (bottom) connected by a bridge. The shell conceals many small bones.
The bones are covered by visible keratin-based plates (a protein) called scutes.
Additional keratin layers are added beneath the existing layers to facilitate expansion, creating ‘growth rings.’ These are layers of epithelial tissue with a lighter shade around individual scutes.
The amount of growth tortoises experience is influenced by diet (especially protein), temperature and humidity, injury and trauma, illnesses and diseases, gender, species, and genetics.
A tortoise can grow too fast, so its health suffers. The early warning signs of accelerated growth in tortoises are pyramiding (upward growth of the scutes), weight gain, and kidney failure.
Measuring and weighing tortoises allows us to determine if growth rates are normal or abnormal.
How Quickly Does a Tortoise Grow?
To grow and thrive, tortoises need good genetics, quality nutrition, and well-optimized living conditions. How quickly a tortoise grows depends on the following factors:
Food Consumption
The most important factor in tortoise growth rates is food variety and consumption levels. All things being equal, the more calories a tortoise consumes, the larger it’ll grow.
Tortoises need a diet high in fiber and calcium but low in fat and protein.
If a tortoise eats excessively, especially the wrong foods, it’ll become fat or obese. Tortoises’ most obvious signs of weight gain include fat deposits around the neck, legs, and eyes.
Due to their shells, it can be difficult to tell when a tortoise is getting too fat. However, you may notice a particularly overweight tortoise struggling to withdraw to its shell.
According to Herpetologica, brumating juvenile tortoises that miss the first 2 years of brumation experience excessive and abnormal growth.
A high-protein diet may contribute to pyramiding in tortoises. This occurs when the scutes grow upward, forming a pyramid-like shape, making a tortoise appear unusually large and distorted.
While pyramiding can’t be reversed, it can be stopped from worsening.
Living Environment
Tortoises are ectothermic reptiles, relying on their environment for temperature regulation. If the temperature is too low, it slows the metabolism, meaning tortoises can’t digest food.
Optimal humidity settings promote healthy shell and skin growth. Sub-optimal settings can lead to dehydration, respiratory problems, and other health issues that affect a tortoise’s growth rate.
Poor husbandry can lead to the growth of harmful bacteria and fungi, which cause health problems.
For example, mouth rot (infectious stomatitis) can adversely affect a tortoise’s eating ability. This bacterial infection makes biting, chewing, and swallowing food very painful.
Species And Genetics
All species have different genetic codes that dictate their growth rate, development, and final adult size. Consequently, some tortoise species are much larger or smaller than others.
For example, Russian tortoises (Testudo horsfieldii) and Hermann’s tortoises (Testudo hermanni) are small tortoise species that can grow up to 5-8 inches long and reach maturity in 5-10 years.
In comparison, large tortoise species like the Galapagos tortoise (Chelonoidis nigra) can reach 60 inches long and weigh over 500 pounds, continuing to grow in size for 40-50 years.
Tortoises inherit genes from their parents that determine their size and shell shape. So, the same tortoise species can grow at different rates, including those from the same clutch.
Gender
Female tortoises are usually larger than male tortoises for ecological and evolutionary reasons. A female’s plastron (underside) tends to be flatter than a male’s, which is more concave.
Females produce and carry eggs, requiring significant energy and resources. A larger body size offers more capacity for eggs when gravid, resulting in higher levels of reproductive success.
Male tortoises prefer larger females for mating. This can lead to a situation where females are larger, leading to sexual dimorphism (a size difference between males and females).
Trauma And Illness
Injured, sick, diseased, and traumatized tortoises may experience inappetence or difficulty eating, resulting in a lower nutrient uptake than healthier specimens.
Depending on the severity of the injury or health condition, the healing process can take a long time. During this time, the tortoise’s energy and resources are diverted to healing and recovery.
Sometimes, injury or trauma can result in deformities that affect growth. For example, a cracked shell or broken limb can result in a distorted or weaker shell structure that inhibits physical growth.
Is It Bad If My Tortoise Grows Too Fast?
Rapid growth can negatively impact a tortoise’s health. According to Zoo Biology, excessive growth is linked to serious health problems in tortoises such as:
- Metabolic bone disease (MBD), like pyramiding.
- Renal disease (loss of kidney function).
- Weight gain and obesity.
The best way to stop a tortoise from growing excessively or too quickly is to feed it the right foods. A tortoise needs lots of fiber and calcium, so restrict its fat and protein intake.
Juvenile tortoises should be fed daily, but adult tortoises should be fed 5 days a week once they’re old enough. It’s normal for a healthy tortoise to have 2 ‘starve days‘ per week.
When Do Tortoises Stop Growing?
Once a tortoise reaches sexual maturity, its growth rate slows down considerably. So, you’ll notice that even an old tortoise will still shed some of its skin and shell.
There comes the point in a tortoise’s life where the growth is so slow and unnoticeable that you could technically say it has reached its full size.
On average, different tortoise species will reach their maximum size within this timeframe:
| Tortoise Species | Reaches Full Size |
| Russian Tortoise | 20-30 years old |
| Egyptian Tortoise | 7-10 years old |
| Hermann’s Tortoise | 10 years old |
| Greek Tortoise | 2-30 years old |
| Sulcata Tortoise | 15-20 years old |
| Marginated Tortoise | 20 years old |
| Leopard Tortoises | 10-15 years old |
| Indian Star Tortoise | 10-15 years old |
A tortoise’s growth fluctuates at certain points in its life. Given the growth variations among tortoises, a sudden growth spurt is expected.
According to The Herpetological Journal, captive tortoises grow much faster than their wild counterparts due to being fed better quality foods in higher quantities.
