Man lives on island with 120 giant tortoises

Brendon Grimshaw, an 86-year-old Briton, lives on a tropical island in the Seychelles, with no other human inhabitants, but 120 giant tortoises. That’s at least 15 tons of tortoise! I’ve heard of some keepers with big tortoise collections before, but this takes the prize.

He bought the island in 1962 for just £8000.

Easy way to make an incubator

Commercial incubators for tortoise eggs can cost you $100 or more, but here is a simple way to make an incubator for less than $20.

You will need an empty plastic bottle, preferably one with a wide mouth. Go to a pet shop and get a cheap aquarium heater. These heaters cost about $15 and can be set to any desired temperature.

Fill the bottle with water and put the aquarium heater inside. Place the bottle with heater inside some sort of insulated box. One way to construct a good insulated box is to place a small plastic crate inside a larger box, and fill the space between the two boxes with styrofoam.

Voilá! The temperature in this incubator will remain steady and the humidity will remain high because of the warm water. You may have to top up the water every now and then. The beauty of this method is that the water itself helps passively stabilize the temperature through the thermal mass effect.

Why is my tortoise’s urine white?

Some new owners get concerned when they see their tortoise leaving a white, powdery substance in the enclosure. Many people have asked whether this is a sign of some disease, and there is a rumour going around that this powdery urine is the result of dehydration.

In fact, it is quite normal and healthy for a tortoise to urinate white powder. It is concentrated uric acid. Tortoises, particularly those adapted to arid climates, urinate solid matter instead of liquid in order to conserve water. Whereas most animals eliminate the by-products of protein metabolism using urea, arid-climate tortoises perform the same function with uric acid. This allows them to use less water in the process, which is important for their survival in the wild.

If these white leavings are appearing every day, though, it might indicate a problem. They are the end result of protein metabolism, and, as we explain in the article on tortoise nutrition, the amount of protein you give should be modest. Another reason for excessive production of white powder is dehydration. Dehydration leads to accumulation of uric acid, and this can cause problems in the kidneys and bladder if not taken care of.

So, some white powder in the cage is fine, but if it is every day, take this as an early-warning sign and take another look at your hydration and diet strategy.

Is a vivarium ever a good option?

I am not a fan of keeping tortoises in vivaria. As I discuss in the tortoise housing article, vivaria are a poor choice of housing for several reasons. To review briefly:

  • Vivaria are nearly always too small
  • There is a danger of the glass shattering
  • The reflections and transparency of the glass can be confusing to a tortoise
  • There is little opportunity to create microclimates

Now, it may be possible to work around these problems. A large vivarium might be adequate for a very small tortoise, perhaps a Kleinmann’s tortoise. Such a small tortoise would not be able to break thick glass, like a ramming male red-foot might do. I have even heard of a few keepers covering the inside of the glass with paper to block reflections. Perhaps if you go to these lengths, you could keep a tortoise in a vivarium without too much trouble.

There is one situation where a vivarium, properly prepared, can be quite useful: raising hatchlings. Hatchlings obviously don’t need as much space as full-grown tortoises, and a standard vivarium is often about the right size. As always, you need to provide proper microclimates, perhaps by placing logs and other features in the tank. One great microclimate feature for hatchlings is the ‘humid hide’, which I’ll be describing in my next blog post.

Choosing the right calcium supplement

Most tortoise-keepers get that calcium supplements are a good idea. Tortoises have a huge amount of bone-mass relative to their body size, so naturally they need a lot of calcium. But a more confusing subject is how exactly to give the calcium supplement. Should you use the calcium supplements for humans, or fortified tortoise food, or what?

My usual advice to keepers is to avoid commercial foods, including those ‘fortified’ with calcium or other nutrients. I give my reasons for this in the tortoise diet article. It is simply that most of the commercially available foods are not properly formulated. There are a few exceptions, but no off-the-shelf food should be the mainstay of your tortoise’s diet. So we need to look elsewhere for calcium fortification…

Human calcium tablets should also be avoided. For one thing, they are unneccesarily expensive. It is also difficult to persuade a tortoise to swallow them without crushing them up, and if you are going to reduce it to a powder anyway, why feed your animal the binders and adhesives these pills contain?

The best option for a calcium supplement therefore is calcium carbonate in its powdered form. You can get this quite easily online. (It is sold as a food supplement for humans.) Research seems to suggest that the carbonate form is more easily absorbed than other forms of calcium. Sprinkled this on your tortoise’s dinner about twice a week.

The other option – and it is perhaps the best – is the cuttlebone. This is the bone of a cuttlefish. Ask your local fishmonger for it. When this is left in a tortoise’s enclosure, the tortoise will nibble on it as required for extra calcium. Some tortoises never take to it, and these should be given the calcium carbonate powder, but every tortoise-owner should at least try this out to see if your tortoise likes it.

Until next time,

Tortoise’s skin peeling?

A few keepers get concerned that their tortoises skin is peeling. This is seen as white, flaky wisps of skin detaching from especially around the neck and legs.

It has been suggested that this is a sign of low humidity in the enclosure. While I am pleased that people are starting to pay such attention to humidity levels, it is not the problem in this case. Low humidity levels in your enclosure will lead to shell problems like pyramiding, but the shedding of skin is not a problem like this. Shedding your skin every so often is part of what being a reptile is all about. Tortoises do not shed skin as dramatically as snakes or some lizards, that take their whole pelt off like a coat, but they do shed their skin every few months. Because their shell is in the way, they cannot shed their skin in one go, so it peels off bit-by-bit, in what can easily be mistaken for a skin disease.

There is no need to do anything to take care of this peeling it will usually finish in its own time. Your tortoise may enjoy burrowing and scratching around in its substrate; to get the skin off quicker. You can give your tortoise a bath if you like, but don’t try to pull the flakes of skin off, as this can pull off fresh skin underneath.

Help save the Philippine forest turtle!

The Philippine Forest Turtle (siebenrockiella leytensis) is one of the most endangered animals in the world, with only a handful left in the wild. So it’s good to hear that a small, committed group of conservationists on the Palawan islands are creating a protected space where this species can continue to thrive. They have a fundraising campaign on and, at time of writing, have reached 91% of their funding goal. This is great news, as it means they will almost certainly raise their target amount and be able to continue taking care of this fragile piece of life.


One of the most misunderstood topics in tortoise husbandry is how to pick the right substrate for your species. There is a lot of bad advice going around on the Internet, plus a lot of good, but very incomplete advice. People tend to be great advocates of what worked for them, and think everybody should do the same, but different species of tortoise require very different substrates.

Your choice of substrate is going to have a huge impact on your tortoise’s life. Whatever material you choose, your tortoise will have its belly pressed up against that pretty much 24 hours a day. If it is too moist, upper respiratory tract infections are almost guaranteed. If it is too dry, dehydration and associated shell problems are probable.

As that last paragraph implies, the most important factor in substrates is the amount of moisture it will hold. Some substrates – like compost – are pretty soggy, and this will lead to a humid microclimate just above the substrate (i.e. where your tortoise lives). Others – like sand – hold much less moisture, and create much less humid conditions.

So what are some good substrates? Sphagnum moss is good for many tropical species, either on its own or mixed in with compost and sand. You can get it either in horticultural stores, where it is sold for growing orchids in, and some, but not all, reptile shops stock it.

Perhaps the best substrate is a mixture of play sand and loamy compost. When I was first given that advice, I had no idea what either ‘play sand’ or ‘loamy compost’ were, so let me help you out: play sand is the sort used in children’s sandboxes and is sold in hardware shops. Loamy compost means compost with intermediate water retaining capacity – not too soggy and not too sandy – and is sold in gardening shops.

The neat thing about using these as a substrate is that you can alter the ratio to any desired level. More sand makes for a drier substrate; more compost for a wetter one. Tropical species, that are adapted to the rainforest floor, might need a mixture off 60% compost to 40% sand. For a Horsfield’s tortoise, it might be as high as 80% sand to 20% compost. You can also add in a little sphagnum moss too, so your finished substrate might contain 75% sand, 15% compost and 10% moss.

If you keep your senses open, your tortoise will tell you whether you have the right humidity balance in the substrate. Does your tortoise spend all its time up on a basking rock or log, off the substrate? That likely means he doesn’t like it down there.

Besides humidity, there are a few other considerations with substrates. One obvious rule: don’t use things that are poisoned. A lot of woodchips that are sold have been treated with fungicides and things like that; steer clear of all but organic woodchips. Resinous woods like cedar should also be avoided. Another rule: don’t use thing that will catch fire. This is pretty much the opposite of rocket science, but there are keepers out there who have used shredded newspaper as a substrate. Put that under a basking lamp, and I think the warranty on your tortoise becomes void.

Why is calcium:phosphorous ratio important?

As I explain in the article on tortoise nutrition, even if you are feeding your tortoises heroic doses of calcium, it is still possible for calcium deficiencies to develop. Metabolism is a complex game, and the relationships are never quite linear. More calcium going down the hatch does not necessary mean more calcium is available for metabolism and building a strong, healthy shell and skeleton.

Calcium plays other roles in the metabolism of a tortoise besides building the skeleton. After ingestion, calcium goes to the kidneys, where it is allocated to different tasks, depending on the balance of other chemicals present.

To understand how phosphorous can act antagonistically to calcium, it is important to first understand that all foods contain an indigestible fraction. This is called ‘ash’ – the leftovers of food when it is fully digested, just like the ‘ash’ that is left over when a fire burns out. All foods are determined by the kidneys to have either acidic or alkaline ash, and one of the jobs of the kidneys is to maintain the acid-alkaline balance in the body.

The presence of a lot of phosphorous correlates with a high intake of foods that form acidic ash. The kidneys take this as a signal to offload acidic compound so that the delicate pH balance in the body can be maintained. The way it does this is by secreting calcium-based compounds in the urine. So, when a tortoise is taking in too much phosphorous, all the calcium gets diverted to the urgent task of decreasing the acidic load in the body. This leaves little for bone development and shell problems such as pyramiding are the result.

In practice, what does this mean to the tortoise-keeper? Mainly, that you need to avoid or severely limit foods that are high in phosphorous. Many commercial foods, dog food, cat food, and all meat products fit this bill. Now, if you have an omnivorous species, meat products are a necessary part of an optimal diet, but they need to be limited to an ounce or two once or twice a week. Acid-forming foods aren’t bad, and phosphorous certainly isn’t bad (it is an essential mineral, after all!) and we don’t want to get rid of them completely. What is important is that for every serving phosphorous-rich and acid-forming foods, you are giving your tortoise at least three servings of calcium-rich, alkaline-forming foods: vegetables.