There is immense confusion and misinformation about what to feed tortoises. I have seen many websites and pet stores disseminating completely wrong advice and I have some pretty shocking deformities in tortoises resulting from bad nutrition. This need not be the case, as the basics of tortoise nutrition can be understood in ten minutes. This article will give you those basics.
Of course, there is much to learn beyond the basics. You could spend years studying the biochemical and micronutrient requirements of a tortoise and it is impossible to give guidelines that are correct for every species of tortoise at all times. Expert keepers adjust diet based on species, age, sex, activity levels and time of year. All I can give here are some general guidelines. Having said that, if you follow these guidelines, you will still be doing better than 90% of the tortoise keepers out there!
The first thing you need to know is that there are herbivorous tortoises and omnivorous ones. The herbivorous ones must only ever be fed plants. Other species are omnivorous and will take insects, snails and slugs, but can also be raised successfully on a plant-only diet. (Humans are omnivorous, but can survive without eating meat. Omnivorous tortoises are the same.)
For the purposes of this article, I will divide all tortoises up into two broad categories: tropical tortoises (whose Latin names begin with geochelone), which are omnivorous and Mediterranean tortoises (whose Latin names begin with testudo), which are herbivorous. (For those of you keeping desert tortoises (gopherus agassizii), everything I say here about Mediterranean tortoises also applies to them.) It would be better to consider each species individually, but this is only an introductory article and that would take too long. I strongly encourage you to find out as much as possible about the specific requirements of the species you have. A more in-depth guide is given in Practical Tortoise Care. It is absolutely fundamental for all tortoise keepers to know for sure what species their tortoise is. (Believe it or not, there are people who buy tortoises from pet stores without knowing which species they’re buying.)
In general, a tortoise’s diet should be high in fiber, high in calcium, low in phosphorous, high in other minerals, low in fat and low in protein. Read that sentence again. Memorize it. Calcium, fiber and minerals: good. Phosphorous, protein and fat: bad.
This is a good diet for a Mediterranean tortoise. The size of the words represents the quantity of the food
This is a good diet for a tropical tortoise. The size of the words represents the quantity of the food
Leafy green plants are high in calcium, fiber and minerals. Therefore they should form the backbone of most tortoises’ diets. This can include weeds, salad greens, leaves and flowers. Some favourite tortoise foods are
- White clover
- Mulberry leaves
- Prickly pear
- Cos lettuce, romaine lettuce, lamb’s leaf
- Flowering maple
- Timothy hay
- Bermuda grass
- Strawberry leaves
- Raspberry leaves
- Blackcurrant leaves
- Blackberry leaves
- Wild rosemary
To make dinner for your tortoise, grab about a handful of mixed greens and chop it all up quite finely. You can use a blender or food processor, but I find it’s just as easy to chop it all up with a kitchen knife. Use the ‘hinge’ method of chopping like you wanted to finely chop herbs for an omelette. (This is where you put your fingers on the back of the blade to hold one end down; look it up on YouTube if you don’t know what I mean.)
A good rule of thumb for most species is to feed them once a day with the amount of food they can eat in half an hour. You will need to experiment a bit to determine how much this is. Most species do not need to be fed every single day: five or six times a week is best. You never need too feed them more than once in a day. (Overfeeding is one of the common dietary blunders we teach about in Practical Tortoise Care.)
One of the nice things about keeping tortoises is that it is easy to grow the food yourself in a small garden. If you have an outdoor tortoise enclosure, you can turn it into a little edible landscape for tortoises by growing things like dandelions and nettles. Tortoises eat so little that it is possible to grow everything they need in a small garden. Some tortoise oweners have let their toroise roam around the garden, watching it carefully to see what plants it goes for, then planting more of those as tortoise food. It might take a little while to establish the growth you need to keep the tortoise fed, but once the system is set up, it can be really beautiful to see a tortoise roving around an outdoor enclosure, munching on living plants that are a perfect diet for it.
Other tortoise keepers I know have gotten free food just by going to local fields and gathering up dandelions, nettles or other weeds. The point is that you can easily feed a tortoise for free. I wonder why they don’t mention this in pet shops?
As with human nutrition, variety is a good policy. Tortoises observed in the wild tend to wander over a wide area, eating everything they come across, and some have been observed eating over 200 species of plant. I try to keep this image in mind when designing a diet for tortoises. Let them eat the way evolution built them to eat.
Variety is good for two reasons. First, it ensures they’re getting everything they need. If a nutrient, such as a trace mineral, is absent from one food, they will get it in another. Secondly, variety means they are not getting too much of any one thing. If a certain plant contains a toxin or lots of phosphorous or something, making sure they don’t eat it all the time allows the tortoise’s body to eliminate it before it becomes a problem.
Species that hibernate will generally slow down their metabolism greatly during the winter months. Even if you choose not to hibernate them, they will reduce their intake of food, sometimes to the point of only eating once a week or so. This is no cause for alarm; the tortoise knows what it’s doing.
What not to eat
A word of caution on feeding tortoises grass: some species are very well adapted to eat large amounts of grass. Others can not handle the levels of silica foud in grasses and hays.
Species that evolved to graze include African Spurred tortoises, Leopard tortoises, Aldabra tortoises and Galapagos tortoises. These should be fed grass as two-thirds or three-quarters of their diet and the rest should come from weeds, flowers and leafy greens.
For Mediterranean tortoises, the inverse is true. Leafy greens should make up the bulk of their diet, and grass can be given occasionally, perhaps making up 5% of their diet.
Vegetables in the brassica family – cabbage, kale, broccoli, Brussels sprouts etc – contain substances that can block the absorption of calcium, so they should not be given to your tortoise only in moderation. It is generally not necessary to eliminate them completely.
Peas and beans in general should be avoided. These foods are high in protein, which stresses the liver and kidneys, and contain anti-nutrients like phytic acid.
You will hear a lot of conflicting advice on whether or not to feed tortoises fruit. The truth is, it depends on the species. Mediterranean tortoises are not able to digest fruit properly, and it causes gastric problems including intestinal parasites and diarrhea. Some people say that this is only a problem when fruit is given in large quantities, and to give a little piece of fruit once a week or so is alright. My own belief is that it is safest just to avoid fruit entirely. Certainly no Mediterranean tortoise has ever been harmed by having too little fruit in its diet, and I know some very successful keepers who have raised hundreds of thriving Mediterranean tortoises without ever feeding them a scrap of fruit.
Tropical tortoises are a different story. Their natural environment includes forests where fruit would drop off trees and the tortoises find it lying on the ground. Fruit forms a sigificant portion of their natural diet. It is fine to feed these animals fruit. In the wild, fruit makes up about one-quarter of their diet.
One of the quirks of tortoise nutrition is that they need very high amounts of calcium. The reason for this is obvious if you think about it: calcium is what we use to build and maintain our bone mass. A tortoise’s bony shell, which takes up a huge portion of its body-mass, means it is one of the most calcium-hungry animals there is. During the juvenile growth spurt and when a female is forming eggs, the demand for calcium becomes higher still.
Calcium deficiencies are common among tortoises in captivity. This is sad because it is easily preventable. It is all too common to see inexperienced tortoise owners complaining that their animal has a soft shell. Ninety-nine times out of a hundred, this is simply because they have not been given sufficient calcium. Egg-binding, where a female forms an egg but cannot expel it, is another common problem caused by insufficient calcium. A bound egg can damage the internal organs, sometimes with fatal consequences.
Most tortoise owners supplement with calcium, and I recommend this. One word of warning: make sure the calcium supplement you choose does not contain phosphorous. While high levels of calcium are important, the calcium:phosphorous ratio is arguably more important. If a tortoise consumes plenty of calcium but too much phosphorous, itt can still suffer calcium deficiency because the phosphorous blocks the absorption of the calcium. Get a phosphorous-free calcium supplement.
Supplements that contain vitamin D as well as calcium are great. Tortoises (like us) need vitamin D to absorb calcium from their digestive tract. They can synthesize a certain amount of vitamin D from sunlight or ultraviolet lamps (again like us), but unless you live in a very sunny climate, it is best to be safe and choose a calcium supplement that contains vitamin D.
A lot of people have asked about using ordinary human calcium supplements for their torts. At first, I didn’t want to risk it, but then I started reasoning that, as calcium is just calcium, it should be the same regardless of what species is eating it. It took me some research to find the right kind of calcium supplement, but I am pleased to report to the tortoise-lovers’ community that yes, you can use ordinary calcium supplements from a health food store to feed your tortoise. The trick is to use calcium carbonate powder, which the tortoise can absorb easily. Avoid capsules or pills, as these contain a lot of binders, besides being ridiculously overpriced. You can get calcium carbonate powder on Amazon and I’ve never had any problems with it. This can be sprinkled on their dinner and they seem to like it just fine.
An alternative way to provide extra calcium is with cuttlebone. Cuttlebone is the shell of cuttlefish, a crustacean. Seasoned tortoise owners know that when a cuttlebone is left in a tortoise’s enclosure, the tort will nibble at it when it needs to, expertly regulating the amount of calcium in its diet. This is the perfect solution to meeting the calcium needs of your tortoise. There is just one snag: some tortoises just don’t like cuttlebone. I don’t mean some species; it’s an individual quirk. Some of them just turn up their noses at it and never touch it. In this case, find a good source of phosphorous-free calcium carbonate powder.
As with fruit, there is controversy over whether or not to feed meat to tortoises. And as with fruit, this confusion arises from failure to recognize that different species have very different dietary requirements.
Mediterranean tortoises should never, ever be given meat. No exceptions. Many Mediterranean tortoises have suffered from deformities and diseases as a result of their owners giving them meat. I still see websites advising that dog food or cat food can form a part of a Mediterranean tortoises diet. This is garbage. Meat is high in protein, low in calcium, high in phosphorous and high in fat. What was that sentence you memorized at the beginning of this article?
Tropical tortoises, on the other hand, are omnivorous and meat forms a natural part of their diet. Even so, it is best to feed them only very small quantities of meat, perhaps a spoonful once a week. I know of professional keepers of tropical tortoises who have never fed their tortoises animal-derived foods, preferring to raise them as vegetarians, so to speak. If allowed tog raze, they will probably pick up enough bugs and worms to sustain their need for meat.
Off-the-shelf tortoise foods
Some products sold specifically a tortoise food are some of the worst possible things you could feed a tortoise. One well-known “complete and balanced” commercial tortoise food is made from grains, corn, soy, artificial flavorings and colorings, and barely a vegetable in sight. On the label is a picture of a tortoise with evident pyramiding! This has obviously been formulated by someone entirely ignorant of tortoise nutrition. The sad thing is that many well-meaning owners will buy this food and proceed to kill or deform their pet with it. My sincere hope is that this website will prevent at least a few cases of this happening.
Not all commercial foods are bad, though. Zoo Med is one company we are able to recommend. Their products are made from actual dried vegetables and other plants and have been used by professional zookeepers to keep hundreds of tortoises healthy. They sell different varieties, such as for grazing tortoises and for forest tortoises
However, just because there is a good off-the-shelf food, that doesn’t mean you can forget the law of variety. Remember that tortoises in the wild can eat 200 different plants; do you really think you can just feed them the same thing every day for the rest of their lives? Off-the-shelf foods should be seen as just another item on a varied menu.