Nutrition for a captive tortoise can be a difficult balancing act. If a tortoise’s diet isn’t monitored closely, it can consume too much or too little of an essential mineral, such as calcium.
Tortoises need calcium, vitamin D3, and UVB light to maintain strong bones and healthy shells.
Without enough calcium, tortoises are at risk of metabolic bone disease, broken bones, and paralysis. Female tortoises need extra calcium during the development and laying of eggs.
While a lack of an essential nutrient is bad, an overabundance can be as damaging. Even something as important as calcium is harmful in excess.
Why Do Tortoises Need Calcium?
The tortoises’ physiology relies on calcium to grow and function optimally.
Besides their bone structure, tortoises need calcium because their shell is keratin, and calcium determines how thick and strong keratin is. Without enough calcium, a tortoise’s shell will become soft, deformed, or may not even grow at all.
Females need lots of calcium when developing and laying eggs. Since calcium goes into forming and passing each egg, a lack of calcium will result in health problems for the female and her clutch.
Can a Tortoise Have Too Much Calcium?
A tortoise can have too much calcium, but this is rarely acknowledged.
Too much calcium can result in the calcification of certain body parts. Calcification occurs when calcium builds up in soft tissues, organs, and blood cells.
A large calcium buildup can cause the tortoise pain, depending on where it has accumulated. This happens slowly, as calcium is passed through urine, so it’s hard for a tortoise to build up large calcium deposits overnight.
According to Veterinary Record, tortoises that consume excessive calcium fare better than those that consume less. However, they have the highest rate of metastatic calcifications.
Calcium deposits in tortoises are hard to see unless they’re thoroughly examined by a vet, so frequent check-ups should be performed to avoid this problem.
Tortoises with too much dietary calcium are more at risk of developing stones. If you take it to a vet for an examination, you’ll be able to confirm the cause if there is an excess amount of calcium in the tortoise’s urine and blood.
How Do Tortoises Get Calcium in the Wild?
Tortoises can get calcium from various sources in the wild, and the most reliable way for them to get calcium is through vegetation, such as dandelions.
Plants such as kale, which are common in areas where tortoises are native, contain a good amount of calcium that the tortoises can consume. Fruits and berries are other good sources.
Snails, which have crunchy shells made of calcium carbonate and protein, are another fantastic choice for tortoises that crave calcium.
Egg shells are harder to come by, but tortoises eat them for their calcium content. Sometimes, when times are tough, mother tortoises eat her eggs for their nutritional value.
Tortoise Calcium Deficiency Symptoms
Calcium deficiency affects a tortoise’s mood, the shape and growth of its shell, and skeletal growth.
Health problems related to a tortoise’s bone and shell are called metabolic bone disease, which is an umbrella term used to describe different ailments.
According to Zoo and Wildlife Medicine, metabolic bone disease (MBD) is the most common medical disorder in captive tortoises.
The most common symptoms of MDB in tortoises are:
- Soft shells
- Deformed shells
- Lethargy
- Small shell in comparison to the body
- Pyramiding
- Egg binding
- Trouble walking
- Bone fractures
- Loss of appetite
- Constipation
- Bowed legs
- Shell breakage
Other issues resulting from calcium deficiency include respiratory infections and tortoise cloacal prolapse. An unbalanced diet affects a tortoise’s immune system, so you may hear the tortoise wheezing if it is weak from a lack of calcium.
A lack or overabundance of calcium can cause stones in tortoises. When a tortoise is trying to pass a stone through its cloaca, some of its organs may exit the body cavity along with the stone.
How To Give Tortoises Calcium
To give your tortoise calcium, you can either give it calcium-rich foods and vitamins or let it chew on a cuttlebone or mineral block. The best way of giving tortoise calcium is whichever way it likes it the most. Ensure the tortoise gets the recommended calcium content in its diet.
Cuttlebone is the skeletal structure of dead cuttlefish. It’s made of 85% calcium and provides your tortoise with an interactive way of getting nutrients. Many tortoise owners prefer giving their pet cuttlebone because it also helps the tortoise keep its beak trimmed.
The downside to cuttlebone and mineral blocks is that you need to be extra vigilant about the products you give the tortoise. Many calcium products for tortoises contain harmful chemicals, additives, and binding material that in no way benefit your tortoise.
Tortoise Food with Calcium
Many berries, fruits, and vegetables are rich in calcium, including
| Food | Calcium per 100 grams |
| Collard Greens | 141mg |
| Parsley | 138mg |
| Turnip Greens | 137mg |
| Spinach | 136mg |
| Kale | 132mg |
| Beet Greens | 114mg |
| Oranges | 40mg |
| Mulberries | 39mg |
| Tangerines | 37mg |
| Kiwi | 34mg |
| Blackberries | 29mg |
| Papaya | 20mg |
| Guava | 18mg |
If you’re giving your tortoise calcium-rich foods, you need to limit the calcium supplements it gets if it isn’t very active (elderly tortoise, wintertime inactivity).
Many believe that tortoises will always be able to regulate their need for calcium and only consume as much as they need. However, some tortoise species live in areas where resources are scarce, so their instincts may compel them to gorge on as much as possible.
How Much Calcium Should a Tortoise Have in Its Diet?
There should be 1.2 mg to 8 mg of calcium for every calorie. Of course, you don’t need to get this precise to have a healthy tortoise.
Active tortoises that are still growing, mating, and laying eggs need a lot more calcium than those that are elderly and inactive.
Learn about the early warning signs of MBD and other diet-related disorders to know when to change what you feed your tortoise.
