Urates (Protein in Diet)
For herbivorous tortoises, excess protein is metabolized and excreted as insoluble uric acid (urates). Urates are not a result from excess calcium in the diet, nor are they a result from being dehydrated, which are both commonly cited by beginners as the cause of urates. In reality, the presence of urates indicates elevated levels of protein in the diet. The consistency of the urates indicates the level of hydration. Calcium intake is completely unrelated to urate production.
For herbivorous tortoises, limiting protein intake is very important. If uric acid (urates) levels rise beyond what can be flushed by the kidneys, uric acid crystals can be deposited in joints and vital organs. This can lead to articular or visceral gout (Frye, 1991). Additionally, excess protein can also be converted by the liver to carbohydrate and fat, leading to liver disease (Highfield, 1990; Jarchow, 1992).
The tables are turned when we are discussing omnivorous tortoises, however. Any forest-dwelling species, such as redfoots, yellowfoots, elongated, or hingebacks, are from native regions that are plentiful of worms, millipedes, slugs, fungi, and other protein rich food sources. Tortoises, being opportunistic in nature, will accept any food sources. Therefore, these tortoises have evolved different digestive systems that can tolerate higher protein diets. In fact, feeding these tortoise species a protein source every 1-2 weeks is a healthy option, especially because animal proteins are an additional source of vitamin D (making them less reliant on UV exposure).