Tortoises can overeat and being chronically overfed (whether they are overweight or not) can cause long term health problems. Determining when your tortoise is sated is more of an issue of looking at your tortoise's growth and overall well being than on how much he is eating in one sitting. Many tortoises will eat and overeat on prepared commercial foods for dogs and cats (yes people feed their tortoises commercial dog and cat food) and the high protein content of this food can cause an enormous health problem. I have found no articles supporting the use of commercially prepared tortoise pet food, the experts all seem to agree that this does not meet the needs of any type of tortoise.
How much should I feed my tortoise?
General rule for feeding Mediterranean tortoises
In captivity, a high fiber, low fruit content, low protein and calcium rich diet will ensure good digestive tract function and smooth shell growth.
A tortoise's dietary needs will vary depending on whether it is kept indoors, outdoors, it's activity level, and whether it is a herbivore or omnivore.
However, determining what your individual tortoise's needs are is not clear cut and cannot be answered with a generalised answer.
Tortoises have such a range in growth rates and hence feeding needs it's impossible to give a quantifying amount of what to feed tortoises generally, in terms of overall quantity. One good tip is to give the tortoise an off day, this has also shown to improve growth smoothness. This article, Mediterranean Tortoises: How much to feed? By A C Highfield, The Tortoise Trust gives a good overview of the varying nature of tortoise needs and growth.
Determining whether your tortoise is eating enough is more a scientific endeavour, rather than an intuitive one. This FAQ with The Tortoise Trust:
Therefore study the natural habits of your animal and keep accounts of how much, when and what you offer. Keep regular weight measurements and make adjustments if you notice weight lost or gains. After awhile you'll learn the specific requirements to keep your individual animal well fed and healthy.
Problem associated with overfeeding:
- A diet with too much protein can lead to a condition known as pyramiding, where the shell forms pyramid protrusions, in it's most severe form this can be life threatening.
Finding the right balance of vitamin D, calcium and protein is essential for any tortoise's health, this is done through diet, and environment, so the tortoise's diet cannot be examined in isolation from the environment.