Depending on the species, tortoises have a biological system primed for a desert, tropical, or sub-tropical environment. The environment significantly affects tortoises’ nutritional requirements and digestion.
One of the most important nutrients animals consume is protein.
Protein consists of amino acids, which are molecules that build, repair, and sustain muscles. Also, they’re essential for bone mass and produce enzymes and hormones like prolactin.
While the benefits of protein are understood for humans, it’s less certain whether protein is beneficial for tortoises. Tortoises’ nutritional needs differ due to their size, physiology, and body composition.
Can Tortoises Eat Protein?
A certain amount of protein is necessary for tortoises to grow and thrive.
However, they don’t require as much protein as humans. Some theorize that this is because tortoises are reptiles. Due to their environment, tortoises have adapted to food with little protein.
Other reptiles, like snakes or crocodiles, need a high-protein diet because they hunt and eat meat. Tortoises are foragers and opportunistic eaters, not hunters.
They only eat meat when they can find it, and for these reasons:
- Slow movers with mobility limitations.
- Lack of claws for attacking.
- Don’t have sharp teeth.
- It takes years to grow to their full size.
- Some tortoises stay small.
This means that the only protein tortoises consume regularly is plant-based, which is found in low quantities in the vegetables and leaves they eat.
How Much Protein Do Tortoises Need?
The amount of protein a tortoise needs depends on its species. The most common pet tortoises are usually strict herbivores; only a few are omnivorous.
Omnivore tortoise species have upper and lower intestines that are the same length to digest meat more easily.
The only tortoises of this kind belong to the genera chelonoidis, indotestudo, manouria, and kinixys. Tortoises in these genera include:
- Hingeback tortoise.
- Elongated tortoise.
- Red-footed tortoise.
- Yellow-footed tortoise.
- Asian forest tortoise.
- Impressed tortoise.
These six types of omnivorous tortoises can consume meat.
According to Zoo Animal Nutrition, protein should only make up 5% of a tortoise’s diet. If you care for one of these species, only add protein to its diet once it’s no longer a juvenile.
This may seem like very little protein for an omnivorous creature. However, omnivorous tortoises don’t consume protein-rich foods often to avoid pyramiding.
As for herbivorous tortoises, they belong to the genera gopherus and Testudo.
They have an upper intestine that’s longer than their lower intestine. This enables them to digest fibrous material from plants and vegetables. A list of herbivorous pet tortoises includes the following:
- Bolson tortoise.
- Russian tortoises.
- Gopher tortoise.
- Texas tortoise.
- Mojave Desert tortoise.
- Hermann’s tortoise.
- Marginated tortoise.
- Egyptian tortoise.
- Spur-thighed tortoise.
These tortoises shouldn’t be given any animal protein as it’s undigestible to them.
How Do Wild Tortoises Get Protein?
Wild omnivorous tortoises get their protein by consuming slugs, tadpoles, snails, and insects. If they can find a carcass with sufficiently fresh meat, they may consume it, but it’s rare.
Juvenile tortoises are less likely to consume large amounts of protein in one sitting because their foraging area is small when young.
According to the University of South Florida, juvenile tortoises don’t venture far from their burrow to search for food.
That’s because younger tortoises are more vulnerable to thermal stress and predators. So, they’re less likely to eat bugs until they’re older.
Herbivorous tortoises consume plant-based protein. Leaves, flowers, fruits, and vegetables contain protein, although not as much as animal products.
Occasionally, wild herbivore tortoises consume slugs or snails because they’re opportunistic eaters. If there’s nothing else to eat, and the tortoise is at risk of starving, it’ll eat a protein-rich meal.
Effects of Too Little Protein
It’s difficult for tortoises to exclusively have a protein deficiency. If a tortoise gets too little protein, it’s usually because it’s lacking in its diet.
Tortoises don’t require as much protein as humans. Most of their nutrients are used to build and maintain their carapace, which requires calcium, not protein.
The little protein they need can be acquired through a regular, herbivorous diet. Even omnivorous tortoises can thrive without animal proteins.
So, if a tortoise shows signs of protein deficiency, it’s because it’s not eating enough food. Signs that point to malnourishment in tortoises include:
- Getting sick or injured easily.
- Having trouble recovering from illness or injury.
- Being smaller than is normal for its age.
- Thin limbs.
The optimal tortoise diet contains fruits, vegetables, leafy greens, and pellets. A varied diet provides tortoises with all the necessary nutrients, including protein.
Effects of Too Much Protein
It’s far easier for tortoises to ingest too much protein. They already get protein in their regular diets, so high-protein foods will affect their body in the following ways:
Too much protein harms a tortoise’s digestive system, especially if it’s a herbivorous species.
Meat takes significantly longer to digest properly because the protein and fats comprise complex molecules and are harder to break down.
Herbivorous tortoises have a short lower intestine, which is the intestine responsible for absorbing nutrients from food. Ultimately, they can’t reap the benefits of consuming meat because they can’t absorb all the protein.
Digesting such a heavy, complex food is metabolically difficult for tortoises, as it requires a lot of energy for little gain. The high stress on their intestines can lead to constipation or diarrhea.
Too much protein causes kidney hyperfiltration. The kidneys filter waste from the bloodstream and turn it into urine so the body can excrete it.
When a tortoise has kidney hyperfiltration, its urine will be dark and contain too many blood cells. This is a sign of a damaged kidney; if it continues for too long, it can result in kidney failure.
Pyramiding is the excessive, upward growth of the scutes on a tortoise shell. This shell deformity indicates something is wrong with the tortoise’s diet or lifestyle.
Excessive pyramiding can lead to mobility issues, interfere with lung function, inhibit mating, and prevent female tortoises from laying eggs properly.
Excessive protein consumption causes pyramiding because the nutrients a tortoise needs to grow its scutes differ from those needed to grow its bones or carapace.
Tortoises need calcium, phosphorus, and other minerals to grow their bones. According to São Paulo State University, tortoises need starch to grow their carapace.
Their research revealed that a high starch diet resulted in rapid carapace growth but poor bone density. Meanwhile, the Journal of Animal Physiology and Animal Nutrition proved that excessive dietary protein accelerates pyramiding in tortoises.
The outermost section of the shell, where the scutes are located, is made of keratin. Keratin is a type of protein, so high-protein diets increase the protein content on the shell.
Some tortoise species, such as Indian star tortoises, have natural humps on their carapace. These tortoises are more likely to develop pyramiding thanks to their naturally raised scutes.
Reducing the number of plant-based foods with protein, such as edamame, chickpeas, spinach, and asparagus, is recommended for this tortoise species.
Unfortunately, once a tortoise has pyramiding, it can’t be reversed. However, you can prevent pyramiding from worsening by providing your pet with an adequate, low-protein diet.
Protein can result in inflammation because it releases too many amino acids into the body. Bowel inflammation can cause diarrhea.
The tortoise’s joints can also be affected, causing mobility problems and pain. This muscular inflammation makes it hard for the tortoises to move around, which is why inactivity is a common symptom.
Meat causes weight gain in tortoises due to the fat content.
Tortoises are smaller than humans, so they expend less energy than us. So, they store fat quickly and burn it far more slowly.
According to Zoo Biology, tortoises fed meat and grain were much bigger than those fed a more appropriate diet.
Obesity in tortoises is a dangerous health condition. Due to the excess fat, they have limited mobility and can’t hide inside their shells. Also, they develop rubbing sores, which can get infected.
Protein Foods for Tortoises
Tortoises should eat a herbivorous diet, but not because meat is inherently bad.
If you give tortoise meat, measure all the food to ensure it doesn’t get excessive protein, especially when it’s young, due to the risk of pyramiding.
If you want to give a tortoise protein-rich foods occasionally, you can offer the following foods:
- Boiled eggs.
- Unseasoned, boiled chicken.
- Unseasoned, boiled beef.
- Canned snails.
- Canned worms.
- Green beans.
Protein-rich foods should be a small percentage of a tortoise’s overall diet. It’s safe to give a tortoise a small amount of these foods once every 3-4 weeks.