Humidity and aridity

[GeoTerraTestudo]

BTW - I wonder one other thing about the proposed link between humidity and pyramiding. If dryness causes scutes and underlying bone to warp, why doesn't it do the same in comparable tissues in other animals?

Many animals (including turtles) have claws, hooves, or fingernails, which also consist of a keratin sheath overlaying bone. And what about the horns of bovids or rhinos? Why don't they get warped under dry conditions? The beaks of birds and turtles are also made up of keratin that lies atop bone. Yet, the only time they are misshapen is when they have either not been worn down through normal use, or else the animal has MBD that warps the jawbone itself. Dryness does not appear to affect the growth of the beak.

The shape of the keratin may have something to do with pyramiding, since scutes are flatter than structures like claws or horns, which are conical. However, our fingernails are flat, too, and although they can became misshapen from a variety of factors (including dryness), the effects are small compared to pyramiding and apparently limited to the nail, and do not include the phalanx bone.

Again, whatever role dryness plays in pyramiding, I suspect it is not acting alone, because diet and metabolism are probably just as important, if not more so.

 

[chairman]

I read the original post as being about the roles of substrate humidity vs ambient humidity.

My personal experience on the matter is... my first tortoise was a Home's hingeback. I knew he needed humidity and I kept the ambient humidity upwards of 80%. I lived in FL at the time so it was really easy to do, I kept my windows open when temps were above 70 and never ran my air conditioning. However, I rarely added any moisture to the substrate, it was always fairly dry/dusty. That hingeback now has a reverse pyramided shell though he is otherwise quite healthy/active almost 10 years later.

About a year or so ago I picked up 2 juvenile Home's hingebacks, small enough to not have their hinges yet. I have raised them indoors in a climate controlled room with low ambient humidity (about 50-60%). I keep their substrate nice and moist and their shells get misted twice daily. They have grown quite a bit in the last year and are not reverse pyramided.

My sulcata, which I got slightly pyramided at around 4", was raised from that point with high substrate humidity and low ambient humidity and all her new growth is smooth. I probably got her a little too late in the game to accurately tell whether the growth had anything to do with husbandry, though.

So at least for me, with a humidity loving species, substrate humidity was significantly more important than ambient humidity, almost to the point where ambient humidity did not matter at all. I also misted shells, so my results could be placed in the keratin hydration camp as well.

I suppose you could also argue that for any tortoise, any micro-climate they live in really only extends a couple feet below ground to a couple feet above ground. Whatever else is happening outside of those few square feet surrounding the tortoise, including "ambient" humidity, could be completely irrelevant. From that perspective, I would imagine that the humidity within the first couple inches of the ground is likely to be much higher than the humidity a couple feet above the ground pretty much no matter where you are in the world.