3 Things About Tortoises

3 Things About Tortoises

Shells

A tortoise's shell is their exoskeleton and outer part of the spine, having ~60 interconnected bones fused to their endoskeleton. The top part is called the 'carapace', and the bottom is the 'plastron'; both structures are fused by a 'bridge'.

The shell contains plenty of other bones like ribs inside - while the outside has tough scales/'scutes' for protection against injury and infection - possessing a formation similar to keratin (our hair and nails). The drawback is all the 'armour' above being very heavy. They can be as slow as 0.3mph, dependent on species, yet they're still good with rocky terrain navigation.

They even have rings like trees, which can be counted to determine age. They are also symbols of health and wellbeing, so any rotting, 'pyramiding', or atypical growths, for instance, could infer unsuitable welfare standards. It's a myth that tortoises cannot feel anything through the shell as there is an abundance of nerve endings, meaning it's sensitive to touch alongside pain.

In addition, the shell's structured to allow withdrawal of the head for extra safety in response to a perceived threat or scare, except they must exhale before retraction into the shell - fortunately for them, they can hold their breaths for ~30 minutes.

Their large surface area facilitates heat absorption from the sun; as tortoises are ectotherms, they depend on external temperature sources because they can't thermoregulate internally. Usually, ones from warmer climates have lighter shells for cooling, while ones from colder environments have darker colours for heat absorption. The temperature/weather can actually influence gender at birth. The 'aromatase' enzyme converts male hormones to female if warm enough.

Upside down

Despite being able to survive with low blood oxygen levels due to a slow metabolic rate, being upside down will constrain their breathing; since the lungs are at the top end of the shell, the pressure from the other organs' weight bears on it too much.

Tortoises have to sporadically flail their head and limbs to self-right (as long as they have the space), although it's expensive regarding energy - being roughly twice the requirement to walk relative to mass - so for survival purposes, more levelled environments with less chance of them getting flipped over and over should be favoured even if they're good rock climbers.

Nose Drinking and Mouth Smelling?

Tortoises can live in dry climates, so they need to maximise their water intake for hydration. Nasal drinking helps them obtain water from little things the mouth would be too awkward for retrieval, or alternatively, plants with high moisture content, where eating the plant would soak up some of the moisture.

Otherwise, the Jacobson's/vomeronasal organ exists in all snakes, lizards, other reptiles + amphibians and some mammals. It's a soft tissue structure located in the roof of the mouth - which is why tortoises can have their mouths open sometimes, likewise with bearded dragons and snakes using tongue flickers for odour particle accumulation.