“What and how do I feed my tortoise?” is one of the top questions people have. It does not take much research to become completely confused about this. Part of the problem is that there is no such thing as a “perfect” tortoise diet. For that matter, we really don’t have a “perfect” diet for dogs, babies, or humans in general!
Our starting point are the guidelines that the Association of Zoos and Aquariums’ Nutrition Advisory Group came up with. They suggest offering a diet with the following characteristics
Natural Tortoise Diets
Most tortoise species follow a few basic rules in the wild. They generally live in places that are amazingly low in nutritious foods. Even peak growth rain forests that look so lush have amazingly little usable foods most of the year.
Tortoises are designed to live in places like this: they take food most other animals ignore or cannot live on, eat it slowly, digest it slowly, and spend most of their time sleeping so they can live on the small amount of nutrition they have taken in. They may roam an area the size of several football fields to find enough nutrition for the day. When they do find a pile of something tasty – fallen fruit, yummy flowers, carrion – they will gorge, then sleep (sometimes for weeks), then gorge again until it is all gone.
Seasons play a big role as well. During the dry season, they live on tough grasses, leaves, stems, and other drier foods that tend to be low in calories but high in calcium and fiber. During these lean times, they add very thin growth rings to the shell. When the rainy or wet seasons roll in, they gorge on flowers, fruits, and fungi bursting with carbohydrates, nutrients, and flavor. These periods spur growth and this is reflected in wide growth rings. This pattern of feast and famine probably plays a major role in overall health and shell development, preventing pyramiding, etc.
Compare this to captivity where we generally offer meals that are already high in calories and fats, and low in calcium and fiber, offer the same nutritional profile all year along with a similar climate all year, and greatly restrict their ability to exercise. It is no wonder that so many captive tortoises do so badly.
Most tortoises eat about the same things overall, but there are two general categories:
These eat almost entirely plants, and not even all plants equally since most eat few if any fruits. Most of these tortoises live in grassland or arid habitats, and many of them live in places where they often need to brumate in the cold season. They get about 75% of their calories from carbohydrates (sugars found in the plants), 20% from proteins, and the remaining 5% from fats (note: too much fat in their diet causes stomach disorders!) Most of the calories will come from plant matter although almost all tortoises will relish the occasional piece of meat. (Mader)
These tortoises get much of their needed metabolic water from the plants and the digestive processes, but they should still have access to drinking water.
A typical diet profile would be roughly 95% vegetation and vegetables such as grasses, hays, leaves, stems, flowers, “weeds”, and fungi, and less than 5% fruits or vegetables with seeds, and very little meat. (Mader)
Forest dwelling omnivores (Red- and Yellow-footed Tortoises, Kinixys, Indotestudo and Manouria species, American Box Turtles, and most terrestrial turtles) tend to eat a wider variety of foods, usually including fruits and meats. Much of this is probably due to the lower availability of calories and nutrients in the wild foods. (The frequent heavy rains tend to wash the nutrients out of the soil and in response the plants tend to concentrate what little they can get in the fruits.) Most of these tortoises do not brumate, although they may aestivate in hotter or drier weather. They should get about 50% of their calories from carbohydrates, and 25% each from fats and proteins. (Mader)
Most omnivores drink more freely, or at least eat foods with higher water contents. Again, clean water should always be provided.
The typical omnivore tortoise diet would be 75% vegetation and vegetables, 20% fruits or vegetables with seeds, and 5% meats or high-protein foods. (Mader)
You can get chows and other prepared foods for tortoises just as you can for dogs or yourself (think cereals and other processed meals). While there are several options that work nicely, the three most consistently recommended brands in the US are:
There are varying opinions about using prepared diets, ranging from those who use them most of the time, to those who never do. The arguments for prepared chows include:
Arguments against chows include:
Interestingly enough, there are also arguments against fresh food diets!
Natural or Prepared Diets?
People fall into one of these categories:
How Much to Feed?
This is another tricky area. Some people feel that the tortoise can regulate its own intake and cannot really be over-fed, while others worry about obesity and limit the intake. Either way, the key goal is to help ensure healthy growth and natural behaviors.
One way to determine this is to calculate the daily calorie need: the weight in kilograms, to the 0.75th power, times 32 gives us the “base metabolic rate” for any reptile. (WTkg^.75×32=BMR). The BMR is how many calories the animal needs when healthy but not active, such as being kept indoors in a smaller enclosure. You increase the daily calories offered for animals that are more active, i.e. mating, nesting, or reproducing, and reduce it for animals that are in any form of slow-down (approaching brumation or aestivation), or not well. See “Healthy Weight” and “Dosages and Guidelines” for more. (Mader)
Another, more convenient, solution is to roughly mimic the natural diet:
Overfed tortoises will grow in ways that may not be healthy. One study found that tortoises fed free amounts of Mazuri Tortoise Diet added height and width to their shells without adding length (Lickel). High calorie
It is almost always better to underfeed a captive tortoise because of the limited amount of exercise they can get and because most of the foods we offer are so much “richer” in nutrients than the wild diets are.
Revised 5-29-2012. (C) Mark Adkins