Metabolic bone disease in turtles


There are several misconceptions which surround metabolic bone disease (MBD) and many people do not understand quite what it is and why it happens. Firstly, MBD is has far more symptoms than just giving the turtle a soft shell and it can affect most reptiles, not just chelonians. Many of the symptoms, including anorexia and generalised weakness, happen before the softening of the shell becomes obvious. Secondly, the condition is not caused by a simple lack of calcium in the diet and using supplements alone will not cure it; it is much more a case of the proportions of vitamins and minerals in the diet being incorrect and in fact adding just calcium alone can have a detrimental effect. Getting proper advice from a vet, allied with blood tests and possibly x-rays, is vital.

What are the very first symptoms of MBD?

You may notice that your turtle is moving rather differently. When you first get a turtle you need to watch it carefully and get to know all its little habits so that you will notice any changes in behaviour. This is essential as it is often small alterations in gait, swimming patterns and daily routine which will alert you to whether the animal is well or not. In the case on the early onset of MBD, you may notice that the turtle is having problems climbing out of the water, and it may seem generally weak. It may have a tremor as well, but this can be intermittent. Calcium levels have an effect on muscle contraction, so these small changes in the animal’s movement can be the very first sign. You may also notice that the turtle’s bite may have changed, with the jaw seeming a bit floppy. This will go with the anorexia which may follow and constipation is also something to watch for – this can be difficult as most turtles prefer to defecate in the water, but if you see your turtle straining this may be the explanation.

Examining your turtle

Try not to stress the animal, but pick up the turtle gently and examine the shell closely. The shell will seem soft and may be deformed. Where most turtles have fairly flat shells, it may appear more domed, because of a deformation of the spine. Because one of the symptoms of soft shell is the inability of the animal to raise itself from the ground properly, look at the underside (plastron) and you will probably see marks indicating that it has been dragging along the floor. The edge of the shell will probably turn up as well – any of these signs indicate a visit to the vet is in order.

Causes of soft shell disease in turtles

At the root of this problem lies the issue of calcium levels, but it isn’t as simple as just not having enough calcium in the diet. For a turtle or any animal to be healthy, it is necessary for the calcium to phosphorus ratio to be at around 2:1. If there is not enough calcium in the diet for this to happen, then calcium is leached from the bones to make the ratio right. Because this ratio is vital for other metabolic processes, the bones have ‘last call’ on the calcium, as it were, and so softening occurs. This will carry on until the animal cannot survive any longer, so it is very important to put the imbalance right as soon as possible.

Also in the mix is the need for vitamin D. This is a vital part of the metabolism of calcium in the body and without it the calcium from the diet will simply be excreted. Reptiles all need sunlight to manufacture vitamin D – along with most animals, including humans – and so the turtle needs either natural sunlight or a good quality bulb to give the right wavelengths of light. This only has to be for around half an hour a day, but is absolutely vital. The last link in this chain is an adequate diet, properly balanced. Too much phosphorus is just as bad as too little calcium – it is the ratio not the totals which are important and even if the calcium level is more than enough, with too much phosphorus calcium will still leave the bones and shell and MBD will be the result.

Treatment and prevention

In most cases which are diagnosed early, treatment and prevention of future problems are the same – improved diet, exposure to the right wavelength light (UVA and UVB) and proper attention to day length and temperature in the habitat. If these matters are attended to, the turtle will quickly improve, although any deformities will be permanent so its shell will not return to its previous shape. When buying a baby turtle, it is important to check its outline – if the shell is domed it means that at some point it has had inadequate care and you should think very carefully about taking the animal home as it may have other underlying problems.

In very severe cases it may be necessary to follow a strict regime of calcium and vitamin supplements in the diet. This is something for the vet to advise on and you will need to work out a way of giving these additives in a way that means your turtle will definitely be getting them, rather than have them wash away in the water. Some vets will inject calcium in the first instance to give the turtle a bit of a head start and this certainly helps. If your turtle has shown a tendency to MBD, it is a good idea to keep it isolated for a while, to make sure it eats a balanced diet and isn’t too picky – they can be quite hard to feed sometimes.


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