Jacqui's Captive Bred Tortoises

Many people think that a tortoise shell is exactly that, just a shell with no feeling etc, a bit like a snail shell. It was common, years ago to find owners that would drill a hole in the shell and tether thier tortoise in the garden, so they could not wander off. The practice is now, thankfully, outlawed and prosecutable as cruelty! However, this does lead me to feel that a littel exploration of what the shell actually is, is beneficial to anyone interested in tortoises.

There are 2 parts to a tortoise shell. The upper section, called a carapace and the lower part called a plastron. Both sections are made of fused bones.

The carapace is a fusion of around 50 bones which includes the ribs and vertebrae.

The plastron is a fusion of bones which includes the clavicals or collar bones and some portions of the ribs.

Both sections are then joined together at the side by a bony bridge.

The shell has a blood and nerve supply, so bleeding and pain occur if injured, hence the cruelty of drilling the shell!

The shell is covered with a layer of keratin, the same product that makes finger nails. It is arranged in scutes. the carapace usually has 38 scutes and the plastron has around 12 to 14. The names and numbers of each scute correspond to the adjacent bone and body section. They are staggered over the bones to help give the shell its rigidity. Different species have scutes which form different patterns and there can be individual differences between memebers of the same species. There is also a genetic predisposition to a particular arrangement of scute, often seen in generations which fiolow each other. This is not an abnormality that cuases any problems in the same way a birth mark on a human does not. I have an adult female with an unusual scute pattern and she has produced offspring who have the same pattern!

As the shell grows, the number of scutes does not generally change, but thier size does. they enlarge in diameter as new keratin is laid down. age can not be accurately measured by growth rings on scutes, however, as soem tortoises can produce multiple growth rings in one year. growth is also determined by the environmental conditions, ie it is not uncommon to see escalated growth in tortoises that have lived in vivariums and been fed inappropriate diets(particulalry high protein), although this is usually accompanied by pyramiding too. The growth layers can also wear with age, so older tortoises can look like they have not laid down any new keratin for years!

The main condition apparent in the shell of tortoises which indicates a problem is metabolic bone disease. This is primarily caused by inadequate calcium or vitamin D uptake from the diet, inadequate ultra violet light exposure, maily, although can develop following liver, renal and thyroid disease.

The disease causes softening and malformation of the bones. The shell is often deformed, with the rear area of the carapace often pulled downward and the marginal scutes pulled upwards.

Metabolic bone disease can be fatal and any tortoise suspected of having this should be examined, for confirmation, by a reptile vet. Environmental, husbandry and dietary changes may be able to correct the calcium inbalance etc but the deformities are usually permanent.

Injuries to the shell can occur as a result of trauma, such as being dropped or falling from a step etc. Such injuries WILL cause pain, often bleeding and lead to infection (if left untreated) and mis shapen scutes as they heal. The shell has a remarkable ability to repair iteslf BUT a tortoise with any shell injury MUST be seen by an experienced reptile vet, as over ambitious attempts to close the fracture can in fact seal in an infection and create more problems than it resolves, as these infections can in fact be fatal!

The shell of a tortoise is an amazing adaptation or nature which has allowed them to exist for an age. The proper diet, care and environmental conditions are important to allow it to remain healthy.

This section is aimed at being an introduction to the tortoise shell. Further research can be undertaken, but as this site is used for new keepers, I did not intend it to be too in depth, hope it is helpful.

If you have any further questions, please contact me.

5 Vertebral scutes
8 Coastal scutes, as below.