Pyramiding in Tortoise Shells

Why is pyramiding an issue I captive tortoise care? Because it is unhealthy and indicates a bone density as well as an underlying stress and malformation of skeletal structure often called Metabolic Bone Disease (MBD)
Both Alpha and Beta keratins, that the shell is made from, have been studied extensively. Allot is known about how they perform at differing levels of moisture content and in different levels of ambient humidity.
One very important feature is the way in which they gain and lose stiffness as they respond to external humidity.
At levels of humidity above 80% scute keratin possess only a fraction of the strength and durability that it does at 50% RH.
At the opposite extreme of low humidity, below approximately 25% it loses water molecules and becomes very stiff and resistant. At such levels it is exerting a very substantial physical force on the bone beneath. With most tortoise vivarium design, many create extremely dry conditions, with sustained relative humidity as low as 12%.
Directly under basking (heat) lamps very low, very localized humidity well below 20% can occur immediately adjacent to the surface of the scutes of the carapace. This has a profound drying effect, increasing keratin stiffness, driving out water molecules, and at the same time increasing stress forces upon the underlying bony skeleton.
This causes the keratin builds up, vertically, continually.

This vertical and expansive cell proliferation itself creates an upwards force on the skeleton. Where there is concurrent other MBD of any degree (like lack of calcium, sunlight (UV), the effect will be substantial. The bone will attempt to conform to the pattern of growth of the scute. This is the primary mechanism involved in “pyramid” growth syndrome in tortoises
Where the keratin is excessively stiff as a result of very low humidity.
the keratin is unnaturally thickened. It also get porous and weak.

By comparing the color, shape, and growth pattern of the keratin to a wild, healthy specimen you can easily see the difference and the problem. In cases of over-proliferation, it is typically much denser and much darker. These animals tend to share some history in common. In the most cases, this includes being raised in vivarium systems, under heat lamps, low humidity, and frequently deprived of readily available water. The effect of an overhead heat lamp on a tortoise has a very powerful dehydrating influence. Tortoises kept in such conditions also tend to have other health issues related to dehydration: bladder stones, gout, and renal failure.
As they are subjected to extended periods of dehydration, the shell increases growth in an attempt to reduce evaporation losses. This even affects the skin of the limbs, and in particular the proliferation of beta-keratin; bone growth however does not accelerate at the same rate, producing a major problem. This thickened, dry keratin begins to exert an enormously amplified force upon the skeleton.
It is a VERY unhealthy condition for a tortoise. Can shorten their life.
It is PREVENTABLE
1. Keep humidity high in indoor enclosures (by using an enclosed chamber)– water always available in a low dish he can climb in and out of; a terracotta plant saucer works well.
2. Soak young tortoises frequently at least every other day in 80-90f water for 5 minutes
3. Research appropriate food. Do not go by what someone told you in a pet store
4. Give them space to roam and exercise. A 4’x8’ tortoise table if possible
5. Provide sunlight if you can for several hours a day, if you must use artificial UV light, and heat lamps water and humidity to counteract the drying effects are even MORE critical. Consider using extra virgin cold pressed coconut oil on their shell to counteract dryness.
For some of the best and most up to date husbandry information for tortoises go to
www.tortoiseforum.org
There you will find many care sheets on all these issues as well as good advice from members who have raised many a healthy tortoise.

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