Here is some diet information related to desert tortoises. The following tables contain
- a nutritional analysis of major foods of desert tortoises in the wild,
- a list of calcium supplements,
- an analysis of foods often eaten by captive tortoises and
- recommended substitutes.
Please note that values are calculated on a % dry weight basis.
I suggest you allow tortoises to graze in the yard as much as possible. Please read the CTTC Desert Tortoise Care Sheet for plant/seed sources for tortoise forage.
Calcium:Phosphorus (Ca:P) ratios
As you can see, most supermarket fruits and vegetables have a relatively low Ca:P ratio, a low % dry matter (high water content) and high protein.
Desert tortoises in the wild eat a diet with a high Ca:P (greater than 2:1) and a high % dry matter (often greater than 30% dry matter). They can develop shell and bone problems (metabolic bone disease) from a low Ca:P, and kidney/bladder problems (i.e., bladder stones or uroliths) from a diet high in water content (low % of dry matter) and excessive protein.
Nutritional Analysis of the Major Foods of the Desert Tortoise in Arizona and Utah *
| Food | % Protein | % Fat | % Fiber | %CHO | % Ca | % P | % Dry Matter |
| Threeawn | 6.3 | 1.5 | 34.8 | 48.7 | 0.59 | 0.09 | |
| Globemallow | 20.4 | 2.4 | 23.2 | 42.3 | 3.34 | 0.31 | |
| Triodia, slim | 9.7 | 2.0 | 33.7 | 44.4 | 1.01 | 0.08 | |
| Brome, foxtail | 8.5 | 31.6 | 0.28 | 0.23 | 35.9 | ||
| Grama, red | 7.6 | 2.3 | 33.0 | 48.4 | 0.61 | 0.10 | 56.9 |
| Muhly, bush | 7.3 | 1.8 | 36.9 | 48.1 | 0.27 | 0.09 | |
| Heronbill | 13.5 | 2.8 | 21.2 | 47.0 | 1.95 | 0.33 | 16.4 |
| Mean | 10.5 | 2.1 | 30.6 | 47.0 | 1.15 | 0.18 | |
| overall Ca:P = 6.4:1 | |||||||
* As reported by Hansen, Johnson, and Van Devender, Herpetologica 32:247, 1976.
Calcium Supplements *
| Form of Calcium | % Ca | % P |
| Calcium borogluconate | 8.32 | 0 |
| Calcium carbonate | 40.04 | 0 |
| Calcium gluconate | 9.31 | 0 |
| Calcium glubionate | 23 mg/ml | 0 |
| Calcium lactate | 18.37 | 0 |
* Use calcium (Ca) supplements without phosphorous (P) to increase the calcium to phosphorous ratio (Ca:P) in your tortoise diet. Cuttlebone is calcium carbonate and allows self-regulation.
Nutritional Analysis of Foods Commonly Eaten by Captive Desert Tortoises
| Food | % Protein | % Fat | % Fiber | %CHO | % Ca | % P | Ca:P | % Dry Matter |
| Apples | 1.1 | 3.6 | 6.4 | 85.5 | 0.04 | 0.06 | 0.7:1 | 15.6 |
| Avocados | 6.1 | 47.3 | 6.9 | 18.2 | 0.03 | 0.12 | 0.3:1 | 26.0 |
| Bananas | 3.0 | 0.6 | 2.5 | 62.1 | 0.02 | 0.07 | 0.3:1 | 24.3 |
| Beans, green | 19.3 | 1.8 | 14.1 | 71.6 | 0.57 | 0.44 | 1.3:1 | 9.9 |
| Beet greens | 24.2 | 3.4 | 14.3 | 50.6 | 1.31 | 0.44 | 3.0:1 | 9.1 |
| Broccoli | 32.9 | 2.8 | 11.9 | 54.1 | 0.94 | 0.72 | 1.3:1 | 10.9 |
| Cabbage | 16.9 | 1.9 | 10.5 | 71.4 | 0.64 | 0.38 | 1.7:1 | 7.6 |
| Cantaloupe | 7.8 | 1.4 | 6.8 | 85.1 | 0.16 | 0.18 | 0.9:1 | 8.8 |
| Carrots | 8.4 | 1.5 | 8.5 | 73.1 | 0.28 | 0.27 | 1:1 | 11.8 |
| Chard, Swiss | 27.0 | 3.5 | 9.0 | 51.7 | 0.99 | 0.44 | 2.3:1 | 8.9 |
| Chicory | 1.7 | 3.9 | 22.9 | 0.1 | 0.04 | 2.5:1 | 10 | |
| Collards | 32.7 | 5.4 | 6.1 | 51.0 | 1.70 | 0.56 | 3.0:1 | 14.7 |
| Corn, sweet | 7.0 | 2.0 | 2.9 | 44.5 | 0.006 | 0.22 | 0.03:1 | 27.3 |
| Cress, garden | 24.5 | 6.7 | 10.4 | 51.8 | 0.76 | 0.72 | 1.1:1 | 10.6 |
| Dandelion greens | 18.7 | 4.9 | 11.1 | 63.8 | 1.30 | 0.46 | 2.8:1 | 14.4 |
| Endive | 25.7 | 2.9 | 11.4 | 60.0 | 1.17 | 0.78 | 1.5:1 | 6.9 |
| Grapes | 4.0 | 4.1 | 2.7 | 55.4 | 0.05 | 0.04 | 1.3:1 | 18.4 |
| Grape Leaves | 5.6 | 11 | 17 | 0.36 | 0.09 | 4:1 | 27 | |
| Kale | 34.6 | 4.6 | 7.5 | 52.0 | 1.44 | 0.54 | 2.7:1 | 17.3 |
| Lettuce, iceberg | 22.0 | trace | 11.1 | 66.7 | 0.44 | 0.44 | 1:1 | 4.5 |
| Lettuce, romaine | 21.2 | 6.1 | 11.7 | 57.6 | 1.12 | 0.42 | 2.7:1 | 6.0 |
| Mustard greens | 28.5 | 4.8 | 10.5 | 53.2 | 1.74 | 0.48 | 3.6:1 | 10.5 |
| Oranges | 5.2 | 1.2 | 4.3 | 63.5 | 0.21 | 0.10 | 2.1:1 | 14.0 |
| Parsley | 26.8 | 6.7 | 10.1 | 60.4 | 1.34 | 0.40 | 3.4:1 | 14.9 |
| Prickly Pear Fruit | 0.7 | 2.3 | 16 | 0.05 | 0.02 | 2.5:1 | 7 | |
| Prickly Pear Pad | 1.3 | 3.6 | 9.5 | 0.16 | 0.016 | 10:1 | 13 | |
| Peaches | 4.7 | 1.0 | 5.5 | 77.5 | 0.07 | 0.15 | 0.5:1 | 10.9 |
| Spinach | 35.3 | 3.9 | 6.5 | 47.1 | 1.00 | 0.55 | 1.8:1 | 9.3 |
| Squash, Italian | 22.9 | 1.4 | 67.1 | 0.51 | 0.54 | 0.9:1 | 5.4 | |
| Strawberries | 6.7 | 4.7 | 13.9 | 79.9 | 0.20 | 0.20 | 1:1 | 10.1 |
| Tomatoes | 15.4 | 3.1 | 9.2 | 66.2 | 0.18 | 0.38 | 0.5:1 | 6.5 |
| Turnip greens | 30.9 | 3.2 | 8.3 | 51.6 | 2.54 | 0.60 | 4.2:1 | 9.7 |
| Watermelon | 6.8 | 2.5 | 8.1 | 86.4 | 0.09 | 0.14 | 0.6:1 | 7.4 |
• Items highlighted bold can be used if necessary until graze items are growing but should be supplemented with Suggested Substitutes (see below) to increase the Ca:P ratio and lower the water content. Utilize a “salad” style if using greens instead of just one item.
• Broccoli, cabbage and other Brassica family vegetables are not recommended. Neither are fruits except Prickly Pear (Opuntia) fruit which should be seasonal and occasional.
Suggested Substitutes *
| Food | % Protein | % Fat | % Fiber | %CHO | % Ca | % P | Ca:P | % Dry Matter |
| Alfalfa meal, pelleted** | 20.9 | 3.2 | 23.2 | 41.2 | 1.35 | 0.30 | 4.5:1 | 91.9 |
| Alfalfa hay** | 17.3 | 2.1 | 31.4 | 40.3 | 1.64 | 0.26 | 6.3:1 | 89.7 |
| Bermuda grass/hay | 11.6 | 2.1 | 25.9 | 50.0 | 0.53 | 0.22 | 2.4:1 | 36.7 |
* We suggest using these as additions sprinkled on foods if you must use any greens from the list above to increase Ca:P ratio and lower the water content.
** Available in many pet shops and feed stores.
Originally published in the Tortuga Gazette 25(7): 6-7, July 1989.
Updated June 2012 by Don Williams.
