Tortoise and turtle shells, and potential problems

All turtles, tortoises and terrapins have shells that can vary hugely in terms of sizes, colours and shapes, but with the exception of the three soft-shelled turtle varieties, the one thing they all have in common is that their shells are hard, tough and protective. However, with the huge range of patterns, make-ups and other differences between species, it can be hard for the hobbyist keeper to know what is normal when it comes to the shell of their own pet, and how to spot potential problems.

In this article, we will look into shells in more detail, plus explain some common problems that can arise in the shells of pet turtles and tortoises.

More about the shell

The shell of the turtle and tortoise consists of two parts: The dorsal or top of the shell, which is called the carapace, and the ventral or bottom shell, called the plastron. In the adult turtle or tortoise, both halves of the shell should be hard, but it is worth bearing in mind that for the juveniles of some species, the shell hardens up as they age.

The bottom half of the shell, the plastron, is the part that is most prone to developing problems and infections, as it is in close contact with the ground. However, as the carapace is more obviously easy to observe, when many people think about the shell, this is the area that they think of first.

The shells of turtles and tortoises are constructed of sections, which are called “scutes.” These scutes are made of keratin, the same protein that our own fingernails are made from, and are very hard. The scutes will shed in sections and re-grow as part of the natural process of shell renewal.

The ribs and spine of the turtle or tortoise are attached to the carapace underneath the scutes.

Some common shell problems in turtles and tortoises

Shell rot

Shell rot is the term used to describe an infection of the shell, and this usually happens in sections rather than across the whole shell at once. Shell rot can affect either the carapace or plastron, or both. It is rare for there to be any rot on the carapace of a land tortoise.

Turtles and tortoises are highly susceptible to infection if kept in unclean conditions, with dirty water or soiled bedding quickly leading to health problems. When bacteria are allowed to grow on the surface of the shell, it can eventually result in shell rot. This condition often manifests as pitting, soft spots, and an overall unkempt or patchy appearance on the shell. Shell rot requires immediate treatment with the appropriate veterinary antibiotics, and in some cases, athlete's foot cream has been proven to be an effective treatment. Healing can take a long time. If left untreated, shell rot will cause the scutes of the shell to decay, exposing the bones and organs underneath, which can often be fatal.

SCUD

SCUD, or septicaemic cutaneous ulcerative disease is a serious condition that usually begins with some kind of injury or impact to the shell, which then becomes infected with bacteria through the open wound. This causes poisoning and can eventually affect the liver and other internal organs, which is why it is vital to get any cut or injury on your pet checked out by a vet, even if it appears to be very minor.

Shell shedding

While shedding of the scutes is a natural process that should reveal fresh new scutes underneath, if your pet’s scutes are sloughing off or falling off prolifically, it is likely that an infection is in play or that something has caused damage to the shell.

Pyramiding of the shell

While some tortoise and turtle species have natural peaks on their shells, pyramiding refers to abnormal changes in individual scutes, creating a pyramid-shaped appearance. This is often due to poor UVB lighting or insufficient calcium in the diet and is not seen in wild tortoises.

Severe pyramiding can also result from a tortoise being raised too dry. For this reason, it's recommended that babies be kept in closed setups, as low humidity is a major contributing factor. Proper humidity levels are essential to prevent shell deformities and support healthy growth.

Lighting choices significantly impact shell health. Spot and mercury vapour bulbs dry out the shell, halogen bulbs emit too much IR-A, and UV coil bulbs can cause eye burns or insufficient UVB exposure. Red heat bulbs disorient tortoises and should be avoided. Using appropriate lighting is crucial for their overall health.

These pyramids can take a reasonably long time to form, and so you may not realise at first that there is a problem. Correcting the diet or lighting provision of your pet will prevent further issues, but once a turtle or tortoise has pyramiding, these will not go away even when the pet is kept in the optimum conditions. Humidity and temperatures also affect shell health. Too cool ambient temperatures cause excessive basking, which further dries out the shell and contributes to pyramiding.

Metabolic bone disease

Metabolic bone disease comes about due to a lack of some of the essential nutrients that hard shelled animals need, such as UVB light, calcium or vitamin D. It leads to a softening of the shell over time that can cause malformation, and also potentially a loss of bone density. Ensuring that your pet is eating the right foods, getting enough calcium and has adequate UVB lighting provision and a clean tank should ensure that the problem does not arise.