Nutritional Considerations for Tortoises - The "Balanced" Diet Revealed

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Dec 18, 2008
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Nutritional Considerations for Tortoises - The "Balanced" Diet Revealed

One of the most important aspects of tortoise keeping, and the questions I receive more and more are those of people wanting to know how to properly feed their pet tortoises.

Creating a healthy diet for your tortoise does not consist of simply tossing in some iceberg lettuce and cat food. But, by now, most of us know that. What many do not know is just how easy creating a healthy, balanced diet for your tortoise really is.

Poor diet can lead to many health issues, such as MBD (Metabolic Bone Disease), deformities, bladder stones, renal failure and calcification of the liver, to name a few. It is very important that your tortoise receive a diet that is balanced in protein, calcium, and other vitamins and nutrients, without an overabundance of calcium oxalates and phosphorus, which blocks calcium absorption.

It is important to research what part of the world that your tortoise inhabits in the wild, what types of food items are available to them, and what eating habits of wild tortoises have been observed. A wide selection of food items helps to insure a balanced diet.

As far as balanced diets go, it is vital for me to address how to provide a balanced diet. In truth, the most dangerous thing that a tortoise keeper can do when it comes to feeding is to fall victim to monotony. I do not however intend for every keeper to create an elaborate salad with 15 different ingredients every single day. If you only have one small tortoise, for instance, feeding in that manner will take a lot of time, create a lot of waste and a lot of wasted money, and is plain not necessary.

Imagine a wild tortoise is traveling through its home territory when it happens upon a fig tree that is dropping ripe figs onto the ground. The tortoise that happens upon the tree will stop and begin to eat the figs. As more figs ripen, more will drop to the ground, and continue to do so until the season ends. During the entire span that the figs are available to the tortoise, it will remain in the close vacinity of the tree, eating all the figs that it finds. Once the figs are all gone, the tortoise begins moving again, looking for a new food source. The tortoise will stay with this new food source until it is exhausted, at which time it will begin moving again until another food source is found.

At no point is this tortoise going to stop and think to itself, "I have eaten too many figs! I should go find something else to eat, so that I have a balanced diet!"

Another example is the Sulcata tortoise. In their natural habitat, Sulcata have to walk miles each day to find enough food to sustain their enormous bodies. A Sulcata that happens upon a food source is simply not going to leave part of it uneaten. In the desert, food resources can be scarce, and must be fully utilized.

The point of these little narratives is this; tortoises are and always have been opportunistic feeders. This means that they eat what is available to them. At times in the rainforest, the only food item a Redfoot tortoise may find is Pothos. Pothos is edible, but high in oxalic acid. Oxalic acid in abundance binds the calcium in the diet, causing it to pass through the tortoise's system instead of being absorbed. However, the Redfoot eats the pothos, and does not suffer from calcium deficiency. Why is this?

The reason the Pothos does not harm the Redfoot is that the Redfoot does have a balanced diet. When the Redfoot is is done eating the Pothos, he moves on to another food, one that may have more calcium and less oxalic acid than the Pothos.

The metabolic rate of a tortoise and the way they digest foods is very different than that of a human. Tortoises can potentially live for hundreds of years. A week or even a month is a very short period in the total lifespan of a tortoise. A tortoise may sit for a month under the fig tree, eating figs, but then he moves on to another food source, effectively balancing his diet.

In captivity, it is okay to mimic this behavior. I use approximately 2 pounds of greens a day at the time I am writing this. People that have small tortoises or only a single tortoise would find it impossible to use that amount of food in a week's time. If the store only sells greens in one pound bundles, such as mine does, how do you balance the diet and not create a lot of waste?

The answer is simple. Go to the store, and purchase a bunch of, for instance, collard greens. Feed them until they are gone. When you go back to the store, purchase a different food item, such as chicory. Feed it until it is gone. The next time you go back, purchase again a different food item, such as turnip greens. Feed it until it is gone. Continue using different foods, and eventually you will have come back full circle to collard greens, but that is okay. You have succesfully provided a varied and balanced diet.

In the past I "over-studied" tortoise nutrition. While I do believe that is important to have a basic understanding of which foods provide the most nutrients and which foods contain compounds that are less desirable than others (or to take advice from someone that does,) it is far more simple to provide a varied diet than even I previously believed. I have also in the past given advice such as not to feed spinach, because of the high oxalic acid content, or not to feed romaine* lettuce, because it is not as nutritious as other foods. I no longer feel that omissions of this type are necessary. Lettuces contain compounds that when mixed with saliva, create powerful antibacterial agents. Spinach is nutritious and the good by far outweighs the bad. By using both of these examples sparingly, as a part of a varied and balanced diet, you only further enrich your tortoise's eating experience and health. The truth of the matter is that as long as you avoid relying on one item as a staple, there really are no limits to what you can feed, within reason of course.

So let us explore the food items available.

Grasses- Timothy, Indian Rice grass, Bermuda grass, and Orchard grass are just a few. Grasses are a staple for many tortoise species. Very few wild tortoises live on a diet of fruits and vegetables, but rather graze naturally on a diet of grasses and weeds that are high in fiber, low in moisture content and low in protein. Some adult tortoises will eat good quality grass hay, but younger tortoises most often will not. Alfalfa: In moderation, there is no reason that alfalfa cannot be a part of a varied, healthy diet.

Edible Weeds- Considering that most wild tortoises eat an abundance of weeds, it could be said to be obvious that weeds should make up a considerable amount of a captive tortoise's diet. Clovers, mallows, dandelions, broad leaf plantain, wild violets and wild strawberries (leaves and flowers, the berries themselves fall under the category of fruits,) are all great and easy to find food items.

Edible Flowers, Shrubs and Ornamental Plants- These are great as well. For my tortoises I grow rose bushes, hibiscus, rose of sharon, grape leaves, hostas, ostrich ferns, pansies, and many others.

A wonderful site that lists edible weeds, shrubs, flowers, and tree is the Edible Landscaping page at The Sulcata and Leopard Tortoise site.

Always remember to collect your grasses, weeds and flowers from areas that you know to be completely free from fertilizers and pesticides. Also important is to avoid areas that dogs frequent. Heartworm medications, wormers, and other medications present in dog feces can prove fatal to your tortoise.

Optunia Cactus-Optunia cactus is not only a food that is available to many tortoises in the wild, but also one that is loaded with fiber and calcium both. It is also a food source that is easily propagated both indoors and out, and provides a renewable food source. Spineless varieties are available, but it is also very simple to expose the finer spines to a source of flame, such as the burner of a gas stove or a small hand torch. The larger spines can easily be removed by hand with little danger of injury.

There are varieties that hold up very well to cold weather and can even be planted in areas that receive heavy snowfall and freezing temperatures. Pads are easily rooted by placing them in a cactus media and watering sparingly. There are many suppliers that sell pads online, and they can often be found in Hispanic markets and grocery stores with expansive produce departments.

Other Greens and Veggies- During the warm months it is best to feed as much as possible from the lists above. In the colder months, this is not always possible. Instead we must resort to a diet of dark leafy greens and vegetables.

"Spring Mix" is available at most grocery stores, and is a mix of greens. Some others include kale, collards, mustard greens, beet greens, chicory, dandelion, frisee, endive, turnip greens, spinach (in moderation) bok choy, cabbage (small, infrequent amounts) and pretty much anything you can find in your grocery's produce department. Again, variety is key. Some of your ability to provide variety may be some what seasonal. I know there are certain fruits and vegetables that I am unable to obtain in the winter months.

My favorite vegetables to feed are summer squash, zucchini, butternut squash, sweet potato, pumpkin, and occasional red, yellow, orange, or green pepper. I also will feed any uncooked leftovers of what my family is eating.

Mushrooms- Forest tortoises, such as Home's or Serrated Hingebacks, Redfoots, or Manouria subspecies, thrive on mushrooms. Tortoises that inhabit rainforests or riverine swamp forests often do not have access to fibrous weeds and grasses, and many in captivity turn their noses up at greens. Fiber is important for digestive health, so some sort of fiber is definitely needed in the diet. Fortunately, mushrooms thrive in the same humid, low-light conditions that forest tortoises love, and are very high in fiber, so the tortoises adapted to feeding on the mushrooms. I feed portabella mushrooms to my forest tortoises daily. Other types of mushrooms are available at most grocery stores, but I caution strongly against collecting your own. It is often very difficult to tell what is edible and what is not.

Fruits- Grazing tortoises should not be offered an overabundance of fruit. Some keepers will offer fruits once a month in small amounts as a "treat." I do not recommend offering fruit to grazing species with any greater frequency. I also recommend limiting grazing tortoises to fruits such as cactus pears (also called cactus berries or "tuna") dragon fruits, or other low sugar, yet high moisture and fiber fruits, such as those that come from desert dwelling plants. Figs also are low in sugar and high in fiber, and very well received.

Forest tortoises, again such as Home's or Serrated Hingebacks, Redfoots, or Manouria subspecies, actually eat more fruit in the wild, and it is completely acceptable to offer fruit in amounts equaling approximately 10% of the total diet. I have also discovered that tortoises seem to prefer fruits that are slightly overripe. This makes complete sense when you really think about it. I do not know of many tortoises capable of scaling a tree and picking a pear, but I do know of countless species that are capable of eating an overripe pear that has fallen to the ground.

Meats and Insects- Do not adjust your screen, and there is nothing wrong with your eye-glass prescription. I actually did say "meats and insects."

Conventional wisdom is that all tortoises are herbivores. While it appears that a majority of tortoises do in fact live mostly off of vegetation alone, there are many species that are in fact omnivores. Even herbivorous tortoises are known to consume carrion from time to time. This does not mean that I advocate feeding meat to herbivores. In fact I do not. However our low-light loving forest tortoises benefit from having a source of protein in the diet.

Some keepers utilize low fat, re-hydrated cat kibble to provide a protein source for their tortoises. I personally do not, because I do not approve of foods that contain grains and other fillers. Lean salmon or mackerel, fresh or canned in water, earthworms, woodlice/pill bugs, edible slugs, snails, roaches and other insects are very well accepted by tortoises that need a bit of meat in their diet.

Forest tortoises live in areas of dense vegetation where the amount of UV light that they receive is greatly reduced by foliage. Meats provide Vitamin D3, and help the tortoises to properly utilize calcium. For my omnivorous tortoises, I feed enough meats/insects to equal approximately 10% of the diet.

Pelleted Commercial Diets-There are many commercial diets that claim that they are "complete" diets. Many keepers opt to use these diets for many reasons, including simplicity. I personally do not rely on such diets. There is no variety. Commercial diets also contain grains, sugars such as molasses, high levels of proteins and other fillers. While I no longer believe that excess protein is the main factor in causing pyramiding of the shell, I do believe that excess protein can cause other health issues, such as renal failure and bone and shell disorders caused by too rapid growth.

If you choose to use such a diet, I recommend using either Mazuri Tortoise Diet or Zoo Med Natural Grassland Tortoise Food.

Vitamin Supplements-
There are many supplements available in the pet industry. If you choose to supplement your tortoise, I suggest using a broad spectrum vitamin, such as Centrum. Our drugs are regulated by the FDA. Personally the only artificial supplementation that I provide is pure calcium carbonate, which is available at most health food stores, and also sold as limestone flour, coral calcium, or powdered oyster shell. It is important to offer calcium to your tortoise free choice as well. This is easily done by leaving a cuttlebone in the enclosure at all times. Cuttlebones can be purchased at your local pet supply store, and are marketed for birds. Remove the hard, sharp layer before offering the bone to your tortoise. Leaving the cuttlebone in the enclosure allows your tortoise to make use of it at will, and also provides a double benefit of helping to keep the beak trimmed. You can also use powdered cuttlebone on the food by simply scraping a serrated knife over the soft surface. You can also provide reptile calcium with Vitamin D3 if you are concerned with the level of D3 that your tortoise is receiving.

*In some countries, foods may be known by other names. Alternate food names indicated by asterisk.

Peppers (bell)* - Capsicum
Beet Greens* - Beetroot Greens/leaves
Cilantro* - Coriander
Romaine Lettuce* - Cos Lettuce
Cantaloupe* - Rock Melon
Beets* - Beetroot
Kale* - Curly Kale

Another great site to visit, that contains detailed nutritional information is Nutrient Analysis of Replacement Turtle and Tortoise Foods from the World Chelonian Trust. There is also the Sulcata Station.

I know that all of this information can be very difficult for a new or prospective tortoise owner to take in all at once. Getting a tortoise is a lifetime and very detailed commitment. If at any time I can be of any help, or if you have any questions, please do not hesitate to send me a PM or to post your questions in the Food and Diet section of the forum. The only stupid question is the one that you don't ask, and in the end, compromises the life and health of your tortoise.

Kristina Duda © November 18th, 2010

Discussions about this topic can be viewed or added to by visiting the Nutritional Considerations for Tortoises - The "Balanced" Diet Revealed discussion thread.
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