Ultraviolet rays and food play a very important role. Turtles have large requirements for calcium and vitamins. For these reasons, it is not natural to feed tortoises exclusively with lettuce and tomatoes. They are lacking in vitamins and often treated with insecticides, resulting in various malformations and diseases.
With a natural diet, we obtain improvements in health and even recovery for sick turtles.
Tortoises appreciate corpses of animals. Schmitt and Ingu reports even the case of an Indian which knew quickly how to find corpses of drowned persons in lakes, using a gluttonous tortoise attached to a leash.
It is important to know that deficiencies in calcium and vitamins A and D are at the origin of most diseases encountered in chelonians kept in captivity.
It is unrealistic to expect to recreate the exact diet that turtles have in the wild. However, a very similar one can be offered by keeping it as natural as possible.
This is not always obvious; the table below shows a list of foods with phosphorus calcium ratios above 1.5 with a high vitamin A content.
Food to only give occasionally
Be careful! These foods, naturally rich in calcium, do not promote optimal growth and good shell calcification unless the young turtles receive regular exposure to ultraviolet B light (natural light in outdoor enclosures or specific UVB lights in terrariums). Ultraviolet B light enables them to synthesize vitamin D3 which is necessary for the intestinal absorption of calcium.
Leaves and stems 90% of the ration + 10% fruit: daily.
Cuttlefish bones are regularly distributed in the parks to provide additional calcium.
Snails, given from time to time, provide some meat which is generally sought by turtles in the wild.