Pyramid Growth Syndrome
Although rare in nature, pyramiding is a problem too commonly suffered by tortoises in captivity. Pyramiding occurs when the shell experiences excessive growth where the scutes grow vertically. Although the cause of pyramiding has not been conclusively determined several factors seem to contribute greatly to this condition:
- Low humidity: When the tortoise doesn't have the necessary humidity conditions, pyramiding can develop.
- Dietary problems: Overfeeding, excess protein or a diet low in calcium and vitamin D3 are closely linked to the onset of pyramiding.
- Lack of exposure to the sun: Tortoises need exposure to direct sunlight (or an artificial source of UVB light) in order to synthesize vitamin D3 and fix calcium to their structures. If they don't have enough vitamin D3, their shell will become damaged.
Regarding dietary issues, it is important not only to ensure that foods have a favourable Calcium to Phosphous ratio, the calcium must be metabolically available. One needs to pay particular attention to oxalic acid concentrations — a naturally occurring chemical substance present in many plants which can be safely eaten in small quanities. But it is harmful in high levels as it binds with calcium to prevent the absorption of this much-needed nutrient, and because of this, it can result in calcium deficiency in a relatively short period of time. Oxalic acid can be found in plants such as Spinach, Chard, Good King Henry, and Beetroot, which are all members of the Amaranthaceae (formerly Chenopodiaceae) family, as well as Parsley, Rhubarb and even Dandelions (which have a low level in young leaves but can have a higher concentration in older leaves). Basil enjoys snacks of cuttlefish bone which is very high in calcium.
The science of pyramiding in tortoises is complex — far too complicated to do justice to here. A good article to provide a more in depth understanding comes from a lecture given by Andy Highfield at a conference in 2010.