natural pyramiding Vs captive Pyramiding

[Neal]

If we are talking specifically about Indian Star tortoises, yes females will typically grow at a faster rate than males...though they grow at about the same rate for the first couple of years. That has been my experience anyways.

But, growth rates likely do not have an effect on the pyramiding if the tortoise is being exposed to "good" conditions and husbandry.

 

[Kapidolo Farms]

There is another component of all this, if we want to talk about wild tortoises, success rate. And how would that be measured? By which individual grows the fastest, getting to reproductive size, and leaving its own offspring? By growing old and having a larger lifetime contribution to offspring? At least a few species of chelonians are considered immortal, not in the biblical sense, but in the biological one. They don't experience reproductive or age senescence. Quite the opposite with females, as they get older (larger) they produce more larger eggs with higher survival rates. So quick growth as a stand alone attribute is not so valuable, but larger size is. Considering a life history (actuarial) table for many in a population - the female that grows big sooner will dominate the population with her offspring, taking into account larger also means less vulnerable to predators.

This size to avoid predators is about when sexual maturity occurs, so the first few seasons of eggs, while having a lower probability of success, will distribute that cohorts influence on to the next cohort.

So fast growth has some advantage in the race to have your genes/offspring be among those occupying the space available for the tortoises in a given habitat area. A few populations of aquatic turtles have been so well studied that it is a likely explanation that within one population of other species of turtle or tortoise, multiple strategies are in play at the same time. This is, in part why chelonians have survived a few major extinction events, you know?

Fast quality growth is neither good nor bad, and it is found in nature to some lesser extent than what we do create in our vivariums. You are tipping a balance among different strategies that are found in nature, but our vivariums are not nature, so fast quality growth is OK. Fast QUALITY growth, that would be such that the tortoise is in general having the morphology (looks) of their wild counterparts.

So, pyramiding bad, smooth shell good, smooth shell occurs in wild star, and tent torts too, not all are pyramided (in the sense of a slight hump on each scute). Some small amount of humping in each scute not so bad either, but then the captive tortoise pyramiding "crisis" was never about some small humping, it was/is about tortoises so disfigured that they did not look like any tortoise ever seen in the wild, that was a part of a viable reproductive cohort

Will

 

[Neal]

Some small amount of humping in each scute not so bad either, but then the captive tortoise pyramiding "crisis" was never about some small humping, it was/is about tortoises so disfigured that they did not look like any tortoise ever seen in the wild, that was a part of a viable reproductive cohort

Great statement Will.

 

[Tom]

The "crisis" for me about pyramiding is that I could NOT raise one even remotely smooth here in the dry desert. I read every book, magazine, or article I could find. I talked to every expert. I went to the tortoise lectures at every reptile show I could get to. I tried and tried and tried. I followed all their advice. I did everything "right". And my reward every single time was a big steaming pile of failure... I almost quit tortoises entirely. I DID quit leopards entirely for many years.

I new something was wrong. Something was missing. There was a huge gaping hole somewhere in our knowledge and understanding. I knew it was about the babies because the 4" imports back in the day, NEVER pyramided, even in the same enclosure with our CB juvies. Every one around me was having the same problems, but the people raising them outside in South FL or New Orleans weren't. It took years, and many other people contributing pieces of this puzzle for me to put it together. It will probably take ANOTHER 20 ears to really suss out all the fine details, but I have the main problem solved. I can grow a smooth healthy tortoise of any species now.

 

[Kapidolo Farms]

I keep losing what thread is focused on what thin slice of an issue it is intended to be about. On another almost identical thread, someone posted a link to the article about neonates and juveniles in burrows and the ambient humidity and how that related to water loss in the young tortoises, compared to adults. Tom mentions the 4" imports being much more resilient than his own 'dry' regiem tortoises, blah blah.

So in reading...

WILSON, D. S., K. A. NAGY, C. R. TRACY, D. J. MORAFKA, AND R. A.
YATES. 2001. Water balance in neonate and juvenile desert tortoises,
Gopherus agassizii. Herpetological Monographs. 15:158-170.

on line, (I did not find a open source copy, so am not adding the pdf) I see that they basically documented the volume to mass dehydration of tortoises, in burrows and in labs.

You know how it is a geometric progression of volume to surface area? A cube that is one inch on each side, has a one cubic inch volume, and six square inches of surface. Like a neonate tortoise. Now grow that cube/tortoise to two inches on each side. It now has 8 cubic inches of volume, but 24 inches of surface. The proportion of surface has become smaller. It went from 1:6 to 1:3 (8:24). Our cube can hold much more as it gets bigger, the surface area gets proportionally smaller, we get a double bang for growing. A water reserve in that bigger cube is better able to deal with a water shortage. There is less place (surface) for water to leave the body as the body gets bigger.

As pyramiding occurs at the seams of scutes where growth is happening on the shell, a similar proportional change occurs.

When tortoises are small they have a very low volume for their surface area (lungs, skin, all areas where water may be gained or lost) They probably (yeah a guess) experience a lifelong water stress feedback in their growth. Many genes only work at certain stages of development. Once that stage is over, the gene becomes a "junk" gene for that individual for the rest of it's life. Young individuals who never have water/hydration stress may never activate some gene or suite of genes. However if those genes do get turned on, they can become more active throughout life, especially if they are turned on during very early post hatching development.

This is exactly how a well studied suite of genes work that produce 'heat stress proteins'. If when young someone experiences heat stress often, their body is better set to deal with heat stress throughout life, than someone, who once aged, does experience heat stress but never had a 'trained response' from a younger age. This is an expensive physiological response, but one that provides survival.

The extension of the explanation here is not so big a leap of speculation from heat stress proteins to water stress response. Those cohorts of water stressed individuals would be cohorts that would not be represented in a wild population, if they are water stressed, they may not be 'doers' for a whole life, and die young, and would otherwise be taking up space, that another cohort of 'doers' could use. If at best one season 'set' the lifelong response to water stress, then any single year with high hydration would represent a cohort that does live long reproductive lives. Considering that tortoises are so long lived, it may be a two or three year period of no water stress sets this in motion.

As tortoises age by growth, not time, early quality growth may be much more critical than has been revealed in these conversations or those intense wild population/lab studies. If a wild sulcata takes two or three years to get out of the water stress critical growth phase, and in captivity it gets to the same size in less time, I would speculate it is going to be similarly set, to be a life long individual without an 'active' water stress response.

Just thinking out-loud here, it would be one hell of an experiment to set up. The hypothesis being that water stress at early development reduces life long survival, as found in expressed gene response to a hydration gradient. The follow-up would be based on cohorts in a maxed out habitat based on carrying capacity of said habitat. Does water stress eliminate low likely survivors with the benefit of having space for none water stress cohorts? Is this cohort competitive competition within one species of a long life low reproductive organism?

Will