What is the physiology behind pyramiding?

[Tom]

I do not feel that it is very satisfactory to advance specific husbandry advice when you cannot adequately explain why a particular method works (or not). Guessing is not the same as explaining. You must be able to present a viable mechanism. That must be credible from both biological and physiological perspectives. In short, it must make scientific sense.

Here we are going to disagree. No it mustn't make sense or be fully explainable for it to be true. See my blue sky reference above. Things are either fact or they are not, someone's ability to scientifically explain every detail of it, or their lack of ability to do so, does not make the thing true or false. It would be NICE if it could be clearly explained, and again, I'm all ears here when you are ready to offer your explanation of "What is the physiology behind pyramiding", and fill in all the missing puzzle pieces.

Here again you wish to discuss various wild climate conditions and yet you dismiss thousands of obvious examples that prove points in both directions of this debate as anecdotal. Here is the thing about anecdotes, stereotypes, personal observations, etc: Sometimes they are accurate and true. Sure there are exceptions, but as another forum member noted, "sometimes the exception proves the rule."

The problem is that you can have what appear to be very smooth tortoises externally, but which internally, have very poor bone mineral density - with fibrous lesions and poor mass.

Really Andy? You are now going to tell us that all of these sulcata and leopard tortoises raised in 80% humidity with ideal diets, regular soaks, lots of exercise and sunshine in outdoor enclosures, have "poor bone density - with fibrous lesions and poor mass." This is borderline offensive. Where is your evidence than any of my tortoises have any such thing going on? I'll tell you what. I will put my money where my mouth is: You send me the money to have ANY of my tortoises x-rayed and I will take them to the vet and then post the X-rays right here in public. Here is your chance to prove me wrong. Here is your chance to demonstrate with physical evidence that what you say is true. And if any of my tortoises have poor bone density, fibrous lesions or poor mass, I will eat my words, publicly apologize, and give you back your money. Then I will thank you for the education. What do I get if you are wrong and my tortoises are fine with healthy bone growth? I mean besides some free x-rays?

So again... lets stop talking about what might or might not be happening in wild tortoise climates, and lets talk about pyramiding. Specifically, what causes it and how do we prevent it in our captive enclosures? I have found one way to prevent it, and yes it does prevent it even if the mechanism isn't known to me. If you have another way, I'd like to learn it and see it demonstrated. Please no more debate about who is right or wrong or phantom bone anomalies that you couldn't possibly know exist or not, or who is ignorant of wild conditions.

WHAT CAUSES PYRAMIDING AND WHAT METHOD DO YOU ADVOCATE FOR PREVENTING IT IN LEOPARD TORTOISES AND SULCATAS?

 

[BeeBee*BeeLeaves]

What a fascinating and wonderful thread to read, thank you all ... please do continue ... my friend in Nqweba Dam and I were just wading through ...

 

[nearpass]

What a fascinating and wonderful thread to read, thank you all ... please do continue ... my friend in Nqweba Dam and I were just wading through ...

Thank you for lightening things up a bit

My summary so far, extrapolating from all the posts, is that no one knows for sure what causes pyramiding, but there are likely different causes which play out differently depending on species and environment. Contributing factors can be: humidity levels, hydration, diet (quantity and quality thereof), age, rate of growth, species...and probably others I've missed. If there were a hard and fast, quantitative answer, someone would have published that long before this. Also, pyramiding has a variety of manifestations, not all of which are necessarily harmful.

I believe most of us here try to do our best and educate ourselves as much as possible, hence I welcome this thread, and will probably print it out to read several times. We should acknowledge that keeping many species of animals is a constant evolution of information, and that there are probably no 'right' methods...they are evolving constantly too. Information has certainly changed vastly in my life time.

 

[Testudoresearch]

You are now going to tell us that all of these sulcata and leopard tortoises raised in 80% humidity with ideal diets, regular soaks, lots of exercise and sunshine in outdoor enclosures, have "poor bone density - with fibrous lesions and poor mass."

I am not going to tell you any such thing, because I have not examined enough of them to know. I can certainly tell you that some of the animals raised using that methodology do have such problems, however. In one case, I was able to examine a Russian tortoise raised in that type of environment, which subsequently died from an unrelated infection. It had been reared on a high growth rate regime, but outwardly looked quite good. There was no extensive 'pyramiding', but some degree of spinal region depression. The keeper was fairly pleased with it. However - there were extensive fibrous lesions present throughout the skeleton, and the bone was thickened and of poor density. If we can get back to the topic.... I am trying to explain this. Please be patient. It is not a simple thing.

If you find anything factually incorrect in what follows, do point it out.

First, I would just make it clear that no tortoises have ever been harmed for any study I have been involved in. All material is derived either from finds in the field (predator victims, etc.), road casualties and specimens donated by keepers and veterinarians. Many specimens are found just like this:

This provides both skeletal and keratin material for analysis.

This is a very typical Testudo graeca graeca carapace section. Please note - the species is not that relevant, the structure of G. pardalis, G. sulcata, T. horsfielii and most other terrestrial tortoises is very, very similar indeed.

The basic 'shell' is formed of a fused rib structure. This is inherently quite a strong structure in terms of resistance to external pressure directed towards the body cavity. The bone is (as you can see) quite thin and very dense. This is overlaid (in life) by a thin membrane packed with blood vessels and nerve endings. Also, in life, the bone itself is not 'bone dry', but rich in moisture. It is alive. This outer membrane supplies the basal area of the scutes with blood and nutrients. It is from this that the keratin cells that form the scutes are generated. There are two prime modes of keratin cell generation and deposition in chelonia. One mode is used by many aquatic turtles. In this mode, new keratin cells push up vertically across the entire plane of the base of each scute. From the inside, out, as it were, in one go. This is why you do not see "growth rings" in those species - and also why in those species, old scute tissue is shed in one go.. to be replaced by a completely new scute, underneath. Like this.

It will be noted that 'pyramiding' is not seen in the same form in these species as it is in terrestrial chelonia (though other carapace deformities can and do occur).

Terrestrial tortoises use a different mode of keratin-cell deposition (epidermal proliferation). In this mode, new cells are predominantly deposited at the edges of the scutes, again building from the inside surface. This is what is responsible for the well-known 'tree ring' effect.

Keratin is a very interesting material, with some remarkable properties. I will return to it shortly.

Tom mentioned some of these captive-reared, intensely deformed animals. This is a classic (and tragic) example.

This is what it looks like inside.

Look carefully. You can clearly see the porous nature of the skeleton, and how the bone itself is deformed precisely matching the scute deformities. The bone is extremely weak. This is very typical of such cases. That is a juvenile G. sulcata, by the way.

For comparison, here are two wild tortoise carapaces viewed internally.

Here, the bone is dense, with no abnormal lesions. This is very healthy, well-formed bone. It has excellent strength and mineralization.

Compare a wild tortoise plastron, here:

To one from a tortoise that suffered 'pyramiding', here:

Again, the characteristic lesions are present. The bone is of poor density and poorly mineralized. It lacks strength and fractures easily. This is classic "MBD".

These two sections (bridge region) graphically illustrate the situation. First from a wild tortoise.

Now, from a CB tortoise that had severe 'pyramiding'.

The differences are obvious. These are Testudo examples, but an absolutely identical situation occurs right across the spectrum of terrestrial tortoises. It makes zero difference if it is a Testudo, a Geochelone, an Indotestudo or even a Kinixys. This pattern of growth and the presentation of MBD is identical.

More to follow.

 

[wellington]

Very interesting. The pics are great for understanding better for us that likes visuals.

 

[Yellow Turtle]

This thread is interesting as all other threads debating about pyramiding cause.

Well, as other hobbyist, I'm very eager to know all of this. But I'm very curious as well for Testudoresearch's id. Is it really Andy CH, or someone using similar name to put all the pictures here? We all know Andy's pov for pyramiding, and many have read his latest article on pyramiding cause, which is more or less the same with what is presented here. Personally, I'd be happy to have Andy here to share his views, as I've read many of his publications online.

I too, not raising any tortoise inside closed chamber due to thinking that it doesn't seem so natural. I put all my torts outside, but I do spray them a lot during hottest days. But I admit all the good results shared by other fellow members here, that this method is the best currently for smoothing captive tortoises. I'm eager to see the X-Ray result of all of those tortoises who have been raised inside the closed chambers as well and will be happy to know that they develop good bone density, as this will be a good contribution to hobbyist caring for their torts.

At the end of the day, I'm all ears about the scientific things presented here, but would expect that Andy or Testudoresesearch shares us the husbandry to raise non pyramiding tortoises. That's the only reason why many forum members following Tom's closed chambers and getting good results. For me, as I raise mines all outdoor, will be very eager to know an outdoor husbandry which can provide 100% smooth tortoise with 100% good bone density and healthy ones.

 

[Testudoresearch]

Let's consider bone in a bit more detail. Most of us think of bone as a rather fixed, static thing. The reality, however, is very different, at least in a live animal (or human). It is certainly inert when dead.. but when living it is a constantly renewing, highly 'plastic' substance. It just tends to move slowly... so we rarely notice it, but it certainly moves.

I apologize for the descent into some technical jargon here, but this is a very valuable quote, worth taking the time to read and think about. It is from a paper called "Plasticity and toughness in bone" by Robert O. Ritchie, Markus J. Buehler, and Paul Hansma (June 2009 Physics Today).

Results suggest that permanent deformation, or plasticity, in bone occurs from multiple, concurrent deformation mechanisms that are active at all hierarchical levels. To appreciate the deformation mechanisms in bone, consider again its different structural levels. Individual collagen molecules deform by stretching and unwinding due first to entropic and then to energetic mechanisms that involve H-bond breaking. In collagen fibrils, molecular stretching competes with intermolecular sliding and the breaking of both weak and strong bonds between tropocollagen molecules. Those sliding motions enable bone to endure large plastic strain without suffering a catastrophic “brittle” failure.

This is important. Bone is highly plastic. Deformation can be caused by an extended period of low-level stress. One example is seen in the bowed legs of people with rickets. The weight of the body and the pull of muscles deforms the bones.... various stressors can do this. Bone is at its most plastic very early in life. Here's a great example. A hatchling tortoise, straight from the egg.

As we know, this straightens out over the next hours and days...it does show just how flexible bone is in those early phases. This becomes less obvious, but this property does remain, and bone can change shape in response to various physical stresses.

The type of deformation presented in a chelonian carapace will depend upon the precise combination of deficiencies (or excesses) present, and at what point in the animals life cycle they occur, but usually fall into one or more of the following categories:

Carapace flattened, depressed and soft.

Typical of classic osteomalacia. Common in animals raised on severely calcium or vitamin D3 deficient dietary regimes. On radiological exam, the bone is of very low density, features mottled radiolucent areas, a coarse trabecular pattern and thinning of cortices (Fowler, 1986).

Carapace displaying pyramid-like raised scutes, pelvic area often depressed.

Typical of fibrous osteodystrophy (juvenile osteoporosis) and nutritional secondary hyperparathyroidism. The condition is also known as “Butcher’s Dog Disease” in canines. This type of deformity is most often observed on animals raised on higher protein, high phosphorus content, high energy, low calcium diets at high growth rates. In many cases, the keratin scutes are thicker and more melanistic than normal, and beaks and claws will be overgrowth due to excess keratin production (Jepson, 2006). Radiological presentation includes diffuse changes in opacity, obvious osteopenia, and abnormally thickened bones of the carapace. There may be pathological folding or compression fractures and coarse trabeculation (Dennis, Kirkberger, Wrigley and Barr, 2001).

Muscular tensions have a direct effect, and this is again most often seen in those cases where the bone is weak and MBD is present in one form or another.

“The muscles of the pectoral (shoulders) and pelvic (hips) girdles pull on the relatively weak shell as the disease progresses. The rear end of the carapace is pulled downwards and the carapace edges curl upwards.” (Redrobe, undated). The same relationship between the deformity of the carapace and appendicular muscle tension was noted by Frye (1991).

Writing in Veterinary Nursing of Exotic Pets, Girling (2003) observes that “The plastron and carapace are weakened due to the hypomineralisation which allows the muscles to deform their structure. This is particularly obvious over the internal attachments of the fore- and hind limbs where depressions are seen”.

In the case of the chelonian carapace, these muscular tensions exert a downward and inward force, producing the characteristic flat, sunken type of carapace deformity.

Another important muscular force acting internally upon the carapace is the result of the unique mode of chelonian respiration (O’Malley, 2005). In terrestrial species, during inhalation, the serratus muscle arises from the front of the carapace to insert on the coracoid while the abdominal obliquus inserts on the skin of the hindlimb. These two muscles, when they contract, result in negative pressure and active inspiration. During expiration the contraction of the pectoralis (which extends from the plastron to the humerus) and tranversus abdominus at the back of the carapace contract, expelling air in the lungs (Gans and Hughes, 1967; Wood and Lenfant, 1976). Here is a particularly terrible example of that.

I am including all this detail so that there can be no doubt what is causing these particular deformities, and to demonstrate conclusively that carapaces can be - in simple terms - pulled out of shape.

Three classes of animal are most susceptible. Juveniles, younger tortoises undergoing a rapid growth phase, and tortoises where MBD is present. These are the very same classes also subject to the highest incidence of 'pyramiding''. This is no coincidence.

More to follow

 

[Tom]

...First, I would just make it clear that no tortoises have ever been harmed for any study I have been involved in. All material is derived either from finds in the field (predator victims, etc.), road casualties and specimens donated by keepers and veterinarians. Many specimens are found just like this:


More to follow.

I'm with you so far. I have also seen many pyramided and un-pyramided shell cross sections. Most of the ones I've seen were Gopherus agassizii, but also a few leopards and sulcatas. I think yours has been the best and most complete explanation of this subject so far. Thank you for the pics, and please continue.

 

[Levi the Leopard]

Great pictures.

The problem is that you can have what appear to be very smooth tortoises externally, but which internally, have very poor bone mineral density - with fibrous lesions and poor mass.

These pictures don't show what you said about those that look good externally.
They show tortoises who were pyramiding and/or suffered from MBD with the "poor bone density - with fibrous lesions and poor mass."

 

[Yvonne G]

Well, so far, so good. I love seeing those pictures. But you still haven't answered the question, "What is the physiology behind pyramiding?", have you...or did I miss it?

 

[Testudoresearch]

Thank you, and yes, 'tis I. I did not wish to distract from consideration of the data on its own merits. It is very late here in Southern Spain (2.30 am) but I will try to continue for a little while. We have seen above that bone is plastic and can be "pulled out of shape". Let's take a look a keratin. Sorry again for having to draw on some unfamiliar terminology - but this is a highly complex subject, and if I oversimplify too much I would (rightly) be accused of failing to present a sufficiently well-documented case.

Keratin has many interesting and valuable properties. One of these is that it is hygroscopic and takes up water in equilibrium with atmospheric humidity (Spearman, 1973). Keratin becomes notably pliable in the presence of high humidity and high temperatures (Shelley, 1954). This property was routinely exploited in the working of objects made from tortoiseshell, obtained from the carapace of the critically endangered Hawksbill turtle (Eretmochelys imbricata). The same property will also be familiar to anyone who takes a hot bath: human toe and fingernails respond in a similar manner. Veterinary problems associated with “wet foot” are also common in equines, where the keratin of the hoof may become over soft and vulnerable to trauma and infection if the animal is maintained on an excessively wet substrate (Reca, 2005). Similar issues have been identified with the beta-keratin of Ostrich claws when subjected to varying levels of ambient humidity (Bonser, 2000). Studies conducted on a wide range of keratins suggest that at relative humidity levels above 80% and below 20% profound changes in both the molecular structure and mechanical properties of keratins occur (Leeder and Watt, 1965, Duer, et.al. 2003). At levels of relative humidity above 80% absorption of water molecules by keratin is considerable (Leeder and Watt, 1965), and this has a very significant effect upon the mechanical properties of the scute, resulting in a major degree of softening and reduction in stiffness. The effect of increasing humidity on the Young’s modulus of keratin was profound, with 410MPa at 100% RH and 3.36 GPa at 53% RH. (Bonser, 2002). The effect of humidity on a wide range of keratins shows a consistent reduction in stiffness and in hardness as humidity and hydration is increased (Fraser and MacRea, 1980, Tombolato, et. al 2010). These effects occur both in vitro and in vivo. In living animals with a horny keratinised hoof or scute, the interior of the keratin layer, adjoining the proximal germinative region, maintains a high level of hydration, and the outer surface (unless the animal is in water) will attempt to equilibriate to the lower, prevailing ambient level (Bertram and Gosline, 1987). The thicker the keratin layer the greater the potential for an increased differential between the two surfaces.

OK.... we now, for the first time have a direct and verifiable link between a tortoise's tissue and external environmental humidity.

So, when we subject a tortoise to very low external humidity, the very molecular structure of the keratin changes. It becomes stiffer and exerts a mechanical stress on the underlying bone. This becomes most acute if RH drops to circa 20%. Precisely those conditions do often exist directly beneath heat lamps. RH there can be incredibly low. I have recorded levels of 11%..... for sustained periods. This is far below what any 'desert' species would experience in nature. In addition... when discussing all this with Frances Baines (of the UV Guide), Frances alerted me to the fact that with the exception of some very special medical lamps, all normal reptile incandescent lamps are emitting high levels of IR-A. I will quote Frances directly:

"Sunlight (aldo) emits short-wavelength infrared (IR-A) which is filtered by the water vapour in the atmosphere. So it has been "drained" of energy in the wavelengths best absorbed by water.... in other words, the wavelengths which heat up water most strongly have already been removed from the sunlight before it hits the tortoise. The remaining wavelengths of IR-A penetrate gently and deeply into skin, muscle and bone and can warm an animal -literally - to the core. This beautiful "water-filtered IR-A" is what makes sunlight the perfect basking light.... as Andy says, warming the entire basking animal evenly and deeply.

On the other hand, incandescent lamps, halogen lamps, self-ballasted mercury vapour lamps, so-called "infrared" red bulbs... any lamp producing heat and light - also emit IR-A ...BUT.... there is only a tiny distance, usually less than a couple of feet, between lamp and reptile. You'd need maybe a mile of atmosphere to absorb those water-heating wavelengths.... So where is the first water those rays from a lamp encounter? Yep.... The water in and around the living cells of the reptile's skin, or in the case of the tortoise, in the living cells of its carapace".

So there we have another intense drying effect. Heating and driving water molecules from the keratin. I actually have a lot of data on this, but it is not really necessary to go into it in depth here.

The basic situation is quite simply that if you "bake" keratin you dry it. The drier it gets, the stuffer it gets, and the more mechanical stress it can exert on underlying, plastic bone. This is one explanation of why these ultra-dry enclosures are so especially damaging and are so frequently associated with very severe forms of "pyramiding".

One very interesting effect has been demonstrated in laboratory tests with chelonia. As they are subjected to extended periods of dehydration, the epidermis thickens in an attempt to reduce cutaneous evaporative losses. This affects the skin of the limbs, and in particular the proliferation of beta-keratin that comprises the horny scutes. As the animal is subjected to dehydration, the scute growth accelerates, becoming ever thicker. Bone growth however does not accelerate at the same rate, producing a major differential. This thickened, dry keratin begins to exert an enormously amplified force upon the skeleton (which in such animals is typically of very poor density). This is one other very important reason why we tend to see particularly badly deformed animals that have been raised in conditions of sub-optimal humidity. Where accelerated growth (and typically MBD) meets dangerously low levels of humidity the conditions are ideal for producing gross distortions of the carapace due to the conflicting physical stresses of muscular tension and tension resulting from over-proliferation of the keratin scutes.

Thickened keratin and gross deformity in a Geochelone chilensis showing characteristic upward deformity of scutes, aka 'pyramiding'

Very clear illustration of the 'upward' stresses from keratin proliferation in a Geochelone radiata.

Take the reverse situation. Subject the tortoise to high (80%+) levels of ambient humidity for extended periods. Keep it very warm. Soak/spray the carapace regularly. This too has a huge effect on the keratin as we have read above. It softens it. It changes the Young's Modulus dramatically. Physical stresses on the underlying bone are reduced.... the bones are not "pulled out of shape" by the keratin, and over-thick keratin is not generated. This is the prime physiological mechanism behind the "high humidity" maintenance system.


One big issue however, is that it can have the consequence of suppressing a symptom of MBD, while doing nothing to address the underlying situation. I say 'can'. I am not saying this is always or automatically the case. It is a risk, though. It can happen. It does not have any effect upon the need to generate high quality bone in the first place. If your nutrition or UVB is not adequate, MBD will still occur. The underlying bone will still be weak - even if it is not visibly deformed. All this does is remove or reduce the physical stress from keratin - it has no other effect.

Another potential problem is that wet keratin is much more vulnerable to bacterial and fungal attack. Again, human toenails can suffer for the same reasons! It is not an inevitable consequence, but it is most certainly a risk.. and I have seen such problems.

A quick summary to date.

Keratin proliferates differently between most aquatic turtles and terrestrial tortoises.

Keratin responds dramatically to changes in humidity and temperature (this is why human hairs were often used in humidity measuring devices).

If the bone is compromised due to MBD, or is very flexible as a result of new growth or the young age of the animal, it will deform far more readily than in a fully developed, older animal.

The specific stresses upon the underlying bone relating to keratin are two-fold; the proliferation of new beta-keratin cells at the edges of the scute that result in an uplifting force (Alibardi) on the older corneous center, and tensions resulting from expansion and contraction as a consequence of hydration status. Where the keratin has an excessively low moisture content and becomes stiff these stresses will be maximised, and where the moisture content is excessively high they will be minimised, as the keratin becomes increasingly soft and pliable.

It is proposed that this is the mechanism responsible for the reported relationship between humidity levels in captive maintenance and so-called scute “pyramiding” in terrestrial tortoises.

There some areas we still need to know more about - particularly why some tortoises seem to have a similar 'deformed' scute formation, but without any concurrent MBD or any other detectable pathology. These, for example...

But that will have to do for now. Time for bed.

Hope you have found this interesting and that it has given you something to think about.

 

[tortadise]

Yes. Please do explain what you can on the psammobates(pictured lastly) I am very curious as to the differences of a smoothly grown chilensis(wild of course and when I use smooth it is used in context similar to a pardalis) compared to that of the tents that naturally "pyramid" especially when found in similar climactic zones.

 

[MasterOogway]

Testudoresearch, I just want to say how happy I am that have you have joined our forum and are sharing with us your experiences, thoughts and knowledge! Please do not stop.

I also want to extend a welcome. I am enjoying this thread. I have great respect for you and Tom discussing also disagreeing without belittling one another but instead challenging each other in a positive fashion. Its a breath of fresh air and an interesting thread. Welcome

 

[Sulcata_Sandy]

Do you have normal radiographs for examples? Since I don't have access to a DEXA unit, just your average "analog" machine, I'd love to compare your findings with mine, I radiograph every tortoise that comes in, whether a rescue or for my personal collection.

Tom, if you lived up here, I'd radiograph all of yours! [SMILING FACE WITH SMILING EYES]

Wait...I lied...I've not xray'd Oliver...he's too enormous for our table, and I can't get the mAs high enough to blast thru that shell without causing a brown-out in western Oregon. LOL

Excellent, data, excellent comparative images. This is a greatly educational debate. Tom, I'm on board with you as well. You have carefully documented many years of hard work and have paid the price. Your recommendations and experience are highly valued.

 

[FLINTUS]

I am curious by saying it is the same with Kinixys. I have only seen pictures of 3 properly pyramided kinixys species. A lobatsiana, a homeana which went very white and a nogueyi-the latter was thought of as a Russian. They seem to stay smooth even with poor care, but I would be interested to see a cross section of a smooth, captive one. I have seen a few slightly raised scutes on others, but most people would still interpret it as 'smooth'. They also seem to grow differently to other species. With my reds, and other species I have observed, you have clear white growth lines in periods of fast growth. With my erosa, the scutes kind of move apart to form a small depression which is later filled in with new growth which looks the same as the old. I will try and get some pics when I get back on Monday.

 

[Testudoresearch]

Moving rapidly on...

I will address some of the above points shortly. I would like to cover 'wild pyramiding' and what might be happening with Tent tortoises first. Then just give a summary of the husbandry practices that can be used to raise very nice looking tortoises, with excellent bone growth - or at least the methods I now employ to do so.

First the mystery of 'natural' pyramiding. This has been a subject that has fascinated me and frustrated me in equal measure. Of course, it is all a matter of degree too - I totally agree with Tom that in pardalis, for example, you never see anything wild as bad as some of these captive-raised examples. Never. Not even close.

This also applies to many other species. What you do see, though, are somewhat raised scutes. Simply not perfectly flat. A few examples.

An adult wild T. marginata in Greece. The central point of the scutes is definitely raised to a degree. That's a wild juvenile found in the same area. That one is very 'smooth'. Interesting point: That adult marginata is much darker than average.

Yes, this is a 100% wild Testudo graeca graeca juvenile (2-3 years of age). You saw this before next to my own CB T. g. g. Again, there is some degree of raising present - look at the frontal vertebral. It is obvious there.

This is a wild young adult Testudo nabeulensis in Tunisia. Once more - not entirely smooth. Certainly not 'deformed', but some clear evidence of raising.

Wild Testudo hermanni hermanni in Italy. Slight raising present.

This is fairly common. I stress again - nothing like the 'deformed' captives we are all so concerned about, but not 100% 'perfectly smooth' either. Whether you call this "pyramiding" or not is debatable. Some may overlook it, I would note it, and would include examples on this scale in the 15-20% of animals I'd regard as having some degree present.

More significant. and certainly more obvious, is this section of a wild G. pardalis carapace. This is a fine example of what I am talking about.

There is no evidence of any pathological problem here. The bone is of excellent density throughout the entire carapace. There are no abnormal lesions. It looks near perfect from a bone density/quality perspective. Yet... the degree of centrai scute raising is very significant. This is very similar to what I have observed in many other wild Leopard tortoises. Another view from inside:

This is right over the pelvic girdle. If there was a major pathological problem, you should see it here - but these structures are excellent and everything about this skeleton appears normal and very, very healthy. Those of you who have studied carapace bones... would you agree?

So - what is happening?

As I said, this perplexed me for a very long time. Only when the keratin-stress data emerged did it even begin to make sense. This is what I think is happening.

Semi-arid habitat tortoises feed, typically, in two cycles per year. This is where the bulk of food is consumed, especially the in the Spring season, on fresh growth. This is more digestible and higher in energy than later Fall growth. Higher energy and more digestible = promotes more rapid growth. This is confirmed by field data and measurements. New bone growth is more sensitive to stress deformation than old, more stable bone. A lot of new keratin is also generated at this same time. Animals in especially arid zones seem more susceptible than equivalent animals in more moderate zones. This also explains the degree of variability. Not all years are the same. Sometimes you get more regular rainfall and somewhat higher ambient humidity and for longer periods than other... some years are unusually dry. Also, different tortoise can behave in slightly different ways, making different microhabitat choices (digging down more - or less, for example). It is my opinion that the fundamental physiological mechanism is the same as seen in pathological 'pyramiding', namely, the varying mechanical stresses induced in bone by keratin, but that in these animals, the bone is not un-healthy. Quite the opposite - so it resists these stresses to a much, much greater degree. Even so, extended stresses can cause some displacement.

In the case of pardalis, the surface area of the scutes is quite large... also, they do tend to have quite a thick, protective layer of scute material vs. some other species. I speculate that this large area of quite dense keratin, acting on a permanent basis, can and does 'pull' even good, strong bone to conformity.

More reliable field data, from more species, would be very useful in this context. This is why I say I 'think' this is what is happening in these wild animals. In terms of the mechanical stress-humidity connection, I know that is what is going on. Both the theoretical and experimental data confirms it beyond doubt (to my satisfaction, at least).

Psammobates...

I used to think this was probably genetic. Now I am minded to suspect otherwise. I think the primary mechanism is the same. They inhabit a very arid Karoo-Veld zone. They are also cyclic feeders. I suspect (but cannot prove) that some also respond to those conditions by generating quite thick keratin as a defence against dehydration... that would (if true) amplify such stresses. Purely subjective observation here, but I think I see a trend where the darker examples are more 'pyramided' than very light examples... I am not claiming this as a fact. I could be wrong. I have not seen enough to be sure. Unfortunately, museum specimens are also thin on the ground, and obtaining osteological and scute specimens for more detailed study is very difficult. So I acknowledge this particular issue as no more than a vague theory.

Sorry I can't be more specific on the Psammobates question. If it is NOT genetic, and NOT the above, then there is some completely different and entirely unique mechanism in action in these that we know absolutely nothing about.

 

[Yellow Turtle]

Testudoresearch, your whole explanations are the most clear articles to describe pyramiding in tortoise compare to others. The added pictures are also very helpful.

But as I mentioned last time, I read most of those things already in the past. Although i wouldn't mind reading it again now, but the question always coming back to me. How would you do so different to raise a captive tortoise outdoor and get a 100% smooth result as shown in your perfect scute pardalis?

Also I recall you mention taking humidities data 1 meter above ground (as the SOP) and also on tortoise level. Can you share the graph plots for those data along the year? Especially for humidity in sulcata and pardalis natural habitat.

Please enlighten us.

Thanks.

 

[Testudoresearch]

Also I recall you mention taking humidities data 1 meter above ground (as the SOP) and also on tortoise level. Can you share the graph plots for those data along the year? Especially for humidity in sulcata and pardalis natural habitat.

Thank you.

Regarding data from both G. sulcata and G. pardalis habitats, I simply do not feel I have enough of publishable quality. I have some that I have gathered myself, and other material from kind and dedicated people who have shared some of theirs with me. It is 'patchy' and not consistent, however (different equipment used, uncertain calibration, possible errors in methodology - and plain and simple not enough of it).

It takes years to gather quality data. You can't do it by just making occasional visits. I did that for years, and still could not get the detail necessary. Even living in Morocco for months at a time left significant gaps. The only real way to do it is essentially to relocate and 'move in' with the tortoises you are trying to study! You can then be there when unusual weather conditions occur... you can follow individuals... you can begin to build up a more accurate annual pattern... you can correlate behavior with climate.... even then, as anyone who has done much field work with tortoises can confirm, it is not easy. Tortoises are often found in difficult terrain, and have large ranges. Lost a tortoise ever in a garden? Try finding one in 10,000 acres of thorny scrub at temperatures of 32C or in the middle of a rainstorm (click link for some photos of these habitats and data collection in progress). You can be out there day after day with nothing to show for it.

It is very hard work and very time-consuming. This past few weeks I have been locating hibernating animals and planting data-recorder probes next to them. Recording temperature fluctuations, RH and soil moisture levels. I have been doing that now for 4 years. It would be fantastic to have similar data taken right next to pardalis and sulcata over the same kind of periods. It will have to be someone else who does that, though, as I am fully occupied gathering data on T. g. graeca! All you need are some good quality instruments, and the determination to go out there and do it. It is more rewarding than just talking about it.

Yes, I will get some practical guidelines up. It may take a day or so, however. I am drafting something new right now.

Thank you again for your comments.

 

[Tom]

Testudoresearch,

All of this info and your manner of presenting it is EXCELLENT. Top notch. I can't thank you enough for taking the substantial amount of time to share this all with us.

As I read through and related your observations and study points to what I have learned with my captive observations and experiments, EVERYTHING you have presented here backs up MY assertions. Everything. Not one contradiction. For years I have been saying, "Pyramiding is CAUSED by growth in overly dry conditions." I have attempted to use the analogy of braces on human teeth to attempt to explain the malformation of the bone under the overly dry scute material in some of our captive environments. YOUR explanation has been VASTLY superior to mine. You have also added some significant pieces of the puzzle for me. For example, the info about the drying nature of our indoor heat bulbs. I knew it was bad, but I didn't know it was THAT bad. I have done some experiments with providing other heat sources with positive results and I've been in contact with some other people doing the same thing.

Also, given your excellent explanation of the hygroscopic nature of keratin, I don't see how this differs from my initial proposed theory at the very beginning of this thread. In the past I have equated the keratin to a sponge after noting obvious differences in the scute material after a long sunning session here in the hot dry desert, followed by a nice warm rehydrating soak. I even did a thread on this. I was fumbling around in the dark a bit, but I did manage to stumble upon some some of the points you elucidated here. Please read this thread from all the way back in October of 2010 and tell me how I was wrong, even more than three years ago: http://www.tortoiseforum.org/thread-19252.html

Now I am hoping that you will give us a care and set-up regime to follow that utilizes and takes advantage of all the principals that you have so eloquently enumerated here. MY interpretation of what to do with this info seems to be different than yours. I think THAT is where our disagreement is going to lie. There have been many discussions here on TFO about providing "optimal" conditions year round, or intentionally providing less than optimal conditions for part of the year in an attempt to simulate what we think happens in the wild. I will be especially interested in your recommendations for housing leopards since they have such an ENORMOUS variety of wild habitats, and most of the captive ones here in the US are of totally unknown or mixed origins. Obviously they cannot be housed outdoors year round in a place like New York, for example, so how do you think they ought to be housed when indoors?

In case you missed it above, THANK YOU for sharing your time and experience with us.

 

[tortadise]

Do you have normal radiographs for examples? Since I don't have access to a DEXA unit, just your average "analog" machine, I'd love to compare your findings with mine, I radiograph every tortoise that comes in, whether a rescue or for my personal collection.

Tom, if you lived up here, I'd radiograph all of yours! [SMILING FACE WITH SMILING EYES]

Wait...I lied...I've not xray'd Oliver...he's too enormous for our table, and I can't get the mAs high enough to blast thru that shell without causing a brown-out in western Oregon. LOL

Excellent, data, excellent comparative images. This is a greatly educational debate. Tom, I'm on board with you as well. You have carefully documented many years of hard work and have paid the price. Your recommendations and experience are highly valued.

You have to set it to bone and shoot one left and one right to achieve results. Soft tissue shots wont show what you need to look for.