Owning a pet tortoise can be a long-term commitment. Whenever a new keeper should even think about getting a tortoise for a pet, they should consider the type and amount of care they’ll need to provide for the entire duration of its lifespan, which for some species could go well over 100 years.
They’ll also need to put into consideration any worse-case scenarios they may encounter, including health issues and how to properly prevent or treat them. One of the most common of these health issues is a condition known as Metabolic Bone Disease.
The metabolic bone disease tortoises have is a common long-term result of improper care and husbandry, and if not treated or handled properly, can cause severe weakness, seizures, and eventually, death to the unfortunate tortoise.
Despite it being such a problematic condition, however, metabolic bone disease in tortoises can be reversed with proper care. In order to do so, you’ll need to know what to look out for. You will also need plenty of proper research into what the individual needs of your tortoises are in order to meet them properly.
What is Metabolic Bone Disease?
Metabolic bone disease (MBD) isn’t actually a disease, and more of an umbrella term for numerous conditions that can cause a tortoise’s shell or bones to deform or soften. While certain cases of metabolic bone disease include conditions like osteoporosis, fibrous osteodystrophy, osteomalacia, Paget’s disease or rickets, the most common form of MBD amongst captive tortoises is secondary nutritional hyperparathyroidism.
Nutritional hyperparathyroidism happens when there’s too little calcium in your tortoise’s system, which is needed for healthy bone and shell growth. The most obvious way this can happen is when there’s not enough calcium in your tortoise’s diet, but can also happen when there’s too much phosphorus or there’s too little Vitamin D. Phosphorus inhibits your tortoise’s ability to absorb calcium, while vitamin D helps with it.
Aside from mineral imbalance, the metabolic bone disease tortoises suffer can be aggravated by poor habitat conditions, such as not having the right temperature, humidity, not being able to hydrate, or not allowing a tortoise to hibernate properly, if they’re the type of species that does so.
Metabolic bone disease tortoises commonly suffer from are most damaging to hatchlings and egg-laying females. Hatchlings are particularly vulnerable to MBD mostly because they grow rapidly in the first year of their lives, which means they’ll need a lot of calcium to supplement that growth, especially for their shells.
As for egg-laying females, metabolic bone disease is troublesome since eggs require a large amount of calcium to form, since their shells are practically made of calcium. A female suffering from MBD might produce eggs that are leathery or soft, and might not be strong enough to protect the hatchling forming within, or would eventually collapse due to its own weight.
Diagnosing Metabolic Bone Disease
The diagnosis of metabolic bone disease can be done through x-ray and undergoing bloodwork. When taken to the vet and made to go through radiographs, a tortoise with MBD will have bones that are either irregularly-shaped or abnormally large for their age. They’ll also show a much lower bone density than normal, both on their skeletons and their shells.
As for the bloodwork, low presence of calcium in the blood and elevated levels of phosphorus can be an indication for MBD. Do note, though, that some individuals might have higher calcium than normal by default, which means it’ll look like they have normal calcium levels despite having MBD, though theyir phosphorus levels are abnormally high.
Though lab work can confirm the metabolic bone disease tortoises have, you’ll need to take them to the vet first, and you won’t be able to do so if you’re not familiar with the signs and symptoms of MBD.
Metabolic bone disease is one of those illnesses that don’t show any signs or symptoms until the condition itself has progressed significantly. This is why it’s important for any tortoise keeper to familiarize themselves with the routine and behaviors of their pet tortoise. This is so that even when small changes occur, you’ll know right away, and will be able to act immediately.
Here is a list of some of the signs of metabolic bone disease. Do take note that one or a combination of these symptoms does not automatically confirm MBD. If your tortoise is indeed suffering from any of them, however, it’s best to take them to the vet as soon as possible.
Tortoises with MBD tend to be lethargic and show a lack of enthusiasm than usual. In worse cases, they may become unresponsive. Some species will undergo hibernation in certain times of the year, so when a tortoise suddenly becomes inactive when it didn’t used to, then they might just need to hibernate.
Hatchlings can be an exception to the rule, though. Tortoise hatchlings will spend most of their days sleeping, and would only come out when they need to eat. This is meant to be a defense mechanism for when they lived in the wild. Hatchlings do this to prevent being noticed by predators.
Another known symptom of MBD is anorexia, or the sudden loss of appetite. While tortoises don’t require food daily, and can survive for months without it, they will eat if presented with food. If a tortoise suddenly doesn’t want to eat, then metabolic bone disease can be a possible issue.
There are numerous other conditions that cause anorexia in tortoises though, so this one shouldn’t be your number one indicator for MBD. For younger tortoises, anorexia is problematic, since by default, their appetites should be through the roof, since they’re growing.
While constipation is an indicator of metabolic bone disease, it can also be caused by other conditions, like impaction or colic. If you’ve ruled out the possibility of your tortoise suffering from impaction or colic, and are still not sure why your tortoise has problems passing poo, then MBD might be the culprit.
If you don’t see poop in your tortoise’s habitat, then it doesn’t always mean that they are having problems passing. Some tortoises will consume their own poo, especially hatchlings. This is considered to be normal behavior, and tortoises do this to help them cultivate good microfauna, or bacteria, in their gut.
Unsteady Gait or Limping
One of the major effects of MBD on a tortoise is weaker bones, which result in weak limbs. This usually manifests itself through limping, or if your tortoise is having a hard time lifting their shell off the ground. Normal, healthy tortoises should be able to lift their plastron easily to a good height and still be able to walk straight.
If you notice your tortoise wobbling while they walk, provided that they aren’t walking on uneven ground, or that you see them dragging their body on the ground rather than walking, then they may be suffering from metabolic bone disease. You may also see your tortoise dragging one of their limbs or limping, which is common on tortoises with MBD.
A Humped Back
One of the biggest indicators of metabolic bone disease is when a tortoise’s posterior carapace, or the back of their shell, is severely depressed. This gives a tortoise’s profile a hump-back look, where their front shell is significantly higher than the backside. This uneven growth is particularly common amongst hatchlings, when they grow the quickest.
Healthy shell growth should be even on both the front and the back. A tortoise’s spine is directly fused to its shell, which means that if there’s a deformity on it, the spine will also be severely affected. This causes mobility issues on tortoises, especially so since they don’t have a flexible spine like humans do.
A Flat Shell
Severe cases of flattened shell growth, particularly for tortoises with domed shells, like leopard tortoises or radiated tortoises, are a huge problem. A flat shell, when it’s supposed to be domed can prevent your tortoise from flipping over on their own if they end up on their backs. This also indicates improper growth due to the lack of calcium, which is needed to make a healthy shell profile.
Some species, however, like the pancake tortoise, do have flat shells by default, or shells that aren’t domed at all. Generally speaking though, if a tortoise’s carapace profile isn’t raised like it should be, then there is something wrong.
Abnormal Beak Growth
Tortoises do not have teeth like other animals do, and instead interact with the world and their food using beaks, like birds do. A tortoise’s beak has a very unique shape depending on the species. Normally, this beak is trimmed down through normal wear-and-tear. When they’re suffering from MBD, the beak might become overgrown or will not wear down properly.
Abnormal growth can cause the upper and lower beak to not meet evenly, and would result in a tortoise not being able to grab, chew or swallow food effectively. If the beak appears to grow like a parrot’s, or flat like a duck’s, then it’s safe to assume it’s time to take your pet to the vet.
It’s also not a good idea to trim the beak yourself. It should be done naturally, through food consumption. Cuttlefish bone is particularly helpful in this scenario, as not only do tortoises love chewing on them to keep their beaks trim, it’s also a good source of calcium.
Generally speaking, tortoises should have smooth, domed shells as they grow. Whenever a segment on the tortoise’s carapace, known as scutes, grow abnormally high, you have a case of pyramiding. Pyramiding is named for the shape the scute makes when they protrude unnaturally as the tortoise grows.
While some species have natural pyramiding, like leopard tortoises, star tortoises and radiated tortoises, excessive amounts of it can cause deformities on the tortoise’s shell, and consequently, on their spines. A bulky, heavily-pyramided shell can cause mobility problems on your tortoise as well.
Though many tortoise keepers are still on the fence as to what causes pyramiding, since many captive tortoises that are otherwise healthy will develop it anyway, it is well known that it’s a sign of metabolic bone disease, especially in severe cases.
Too Big For Their Shell
In severe cases of metabolic bone disease tortoises are known to suffer from, the tortoise will actually outgrow their shells, giving an appearance of having shells that are too small for them. This is not a natural state. Tortoises should be able to fully retreat their head and their limbs into their shells, and if they are unable to do so, then it’s safe to assume that their growth has been abnormal.
A tortoise’s shell has other distinct uses aside from protection, such as absorbing UV light, air circulation, and thermoregulation. A stunted shell will also mean stunted growth and stunted bodily functions.
Metabolic bone disease is known to cause bones to grow abnormally, which can manifest itself by bending unnaturally, or growing uneven. This gives a tortoise’s appearance of having bowed or deformed legs, which isn’t normal. A tortoise’s legs should be straight when they are standing still. If you push against it, it should be strong enough to push back.
Deformed legs will also contribute to an uneven gait, and the inability of the animal to lift their shells off the ground.
Soft or Leathery Shells
Another dead giveaway of MBD amongst tortoises is the presence of a soft shell. Tortoise shells are supposed to be hard, since they’re mostly made of bone. If a tortoise suffers from MBD, then these bones will not have the calcium they need to harden properly. This consequently gives the shell a leathery consistency rather than the hard, dense one that tortoises are known for.
If you’re dealing with a hatchling, and they have a seemingly soft shell, don’t panic. Hatchlings tend to have pliable shells when they’re less than 6 months old, since most of their carapace is still made up of cartilage, which will eventually be replaced by calcium in time.
A healthy hatchling’s shell should feel springy when you touch it and will have significant resistance when you press against it softly. Leathery or soft shells will have a hard time retaining their shape, and will generally collapse when you put just a soft pressure on it.
Dystocia, or egg binding, is a condition that is exclusive to female tortoises that are suffering from MBD. If the tortoise in question isn’t able to metabolise calcium while they’re carrying eggs, then they will have a hard time expelling these eggs through normal egg-laying activities. Calcium is an important component for muscle contractions, which is required to push these eggs out without a problem.
If your female tortoise seems to be showing nesting behavior, such as straining, without them actually laying anything, then it’s safe to assume that they’re suffering from dystocia.
Preventing and Treating Metabolic Bone Disease
Metabolic bone disease is one of the many illnesses a tortoise could get that is easier to prevent rather than treat. Whether you’re treating or aiming to prevent MBD, however, the best action you can take is to provide proper husbandry for the specific species of tortoise you’re keeping.
Here are just some of the issues you’ll need to address in order to treat and prevent MBD on your tortoise.
- Improved Diet
This one has the biggest impact out of all the husbandry requirements. You’ll want your tortoise to have a good amount of calcium in their diet. The greens you buy in the grocery store tend to have lower calcium than the weeds you can find in the wild, so going natural is still the best.
Of course, if letting your tortoise graze outdoors is not an option, whether it’s because of predators or because the climate doesn’t permit it, then phosphorus-free calcium powder can be dusted on your usual greens to help your tortoise develop their bones nicely.
You should also avoid foods that are rich in phosphorus. Phosphorus acts like a sponge that pulls calcium away from the bones, which can cause them to grow weak. If you haven’t already, you should check whether the food you’ve been giving your tortoise has a higher concentration of phosphorus than it has calcium. You can do this by simply Googling “nutrition facts for (insert food of choice here)”.
A safe ratio for calcium and phosphorus is 2:1, where the amount of calcium should be double the amount of phosphorus.
- Proper Lighting and Heat
As mentioned before, tortoises, much like humans, require vitamin D3 in order to properly absorb calcium into their bones. One of the best ways to get vitamin D is to allow your tortoise to bask under the sun, or if it’s not possible, make use of the proper UV lighting.
If for some reason your UV bulb isn’t providing the right amount of vitamin D, then you can give them dietary vitamin D3. Most calcium supplements for tortoises will have this, though not all of them, so it’s best to double check.
A tortoise will also need the right temperature to properly metabolise its food. It wouldn’t be much use to give them calcium or vitamin D if they aren’t able to digest their food properly.
- Vet Visit
In severe cases, you can take your tortoise to the vet, where they can give them a shot of vitamin D3 directly. This is usually seen as a last resort, as not only will this cause severe stress to the tortoise, but the sudden rush of vitamin D3 into their bodies can cause a severe shock to their systems.
The vet may also provide your tortoise with oral calcium supplements, but again, this can be stressful for the animal.
No amount of medication will reverse the metabolic bone disease tortoises suffer from if the husbandry is not corrected accordingly. The condition itself will only show much of its symptoms once the illness has progressed enough, which means that it’s generally too late to do much when the tortoise is already showing the signs.
Although metabolic bone disease is treatable after the symptoms have already shown, they tend to have lasting effects on the growth of a tortoise, because they are a long-term condition. They may never look normal again, they may have that limp forever, or their shell will always have severe pyramiding. Despite this, however, they will still have the chance to live a normal, healthy life once the right steps are taken.
As a keeper, it’s your duty to make sure that all of your tortoise’s needs are met, and that they are kept happy and content. Providing them with the right exposure to UV light, giving them the proper diet and keeping them warm enough may seem trivial or basic for keeping tortoises and reptiles in general, but their presence, or absence has a huge effect on your pet.