Two amazing cherry head red foot tortoises currently call the Wild Hearts abode home. At the time of writing this post, Koopa is currently 6 years old and Zamboni is 5. They are both doing really well, even Zamboni who had a bit of a rough start to life.
Today I wanted to write a bit about tortoise shell marbling, sometimes also called mottling.
I shared an older picture of Koopa recently and had a few people ask me why his shell appeared to have different coloration in some spots. They were curious whether this was something normal, or if Koopa had some kind of issue with his shell. In this picture you can probably see the coloration I’m referring too.
In the tortoise world, this change in coloration as a tortoise grows is commonly called marbling. Koopa and Zam are red foot tortoises, so I know the most and will write mostly about their species, but marbling can occur in other species of tortoises as well. When it comes to red foots, marbling is more commonly seen in Brazilian, or cherry heads, than it is in regular red foots.
By the way, cherry head red foots and regular red foots are actually the same species of tortoise! Cherry heads are a population of red foots that originally came from Brazil. They are generally a bit smaller, and more colorful than ‘regular’ red foots. However, they are the same species so their care is the same, and the two types of red foots can be bred together. The scientific name for red foot tortoises, whether they are cherry heads or not, is Geochelone carbonaria.
So is Shell Marbling Normal?
Shell marbling isn’t usually seen in hatching or very young tortoises, instead appearing over time as they grow. As new growth develops, you’ll start to see some of that growth appearing to be a different, lighter, color than the rest of the shell. In some species and/or individual tortoises, lighter growth can eventually darken to match the rest of the shell. In others it will always remain lighter, giving their shell a unique mottled appearance.
Marbling can usually be noticed first on a tortoise’s plastron (the bottom of their shell). Quite awhile before I noticed any distinct color change on Koopa’s carapace (the top shell) I started to notice the new growth of his plastron growing in lighter.
Marbling is part of the normal growth/coloration of some tortoises. Why exactly it occurs is not completely known. It does seem be be genetic, at least in red foot tortoises. In some other species, keepers have reported that marbling seems to be triggered by periods of illness or stress. The lighter coloration is essentially caused by either the loss, or turning off, of pigment cells in portions of the shell. In general, proper diet and lighting will enhance a tortoise’s natural coloration. Although it’s not currently thought to cause marbling, tortoises who receive a proper healthy diet and natural lighting often show more intense marbling, and coloration in general.
Why exactly some tortoises marble is still up for debate.
One theory that makes a lot of sense is that marbling may help to enhance the natural camouflage of tortoises, especially those that live in forest undergrowth. The lighter splotches of coloration may help tortoises blend in better to an environment where splotches of light shine through the tree canopy. Red foot tortoises, one of the main species of tortoises known to marble, are found naturally in a wide variety of habitats – everything from dry savannas to humid tropical forests. Most often, they enjoy humid areas and can be found living near waters’ edge, and in the transitional habitats between forests and plains. Because they generally marble more, I’d be interested to learn whether Brazilian red foots in particular naturally prefer forested areas verses other habitat types. Perhaps this could, at least in part, account for the different levels of marbling in cherry head verses normal red foot tortoises.
Whatever the cause, depending on the species of tortoise, marbling is normal and should not be a cause for great concern. In fact, in red foot tortoises at least, keepers seem to prize marbled tortoises and they are often sold for much more than their normal colored counterparts. If you get your red foot tortoise as a hatchling, as I did mine, there’s no sure way to know whether your little one will marble or not. If possible, you can look to the parents for some indication, since marbling in red foots seems to be a genetic trait. However, the only sure fire way to know your hatchling tortoise will marble is when he/she starts marbling!
Marbling Oftentimes Fades Over Time.
Koopa’s marbling has faded quite a bit overtime. You can compare the photo of him to the left, which is current, to the one at the top of the page. The faded appearance I think, in part, has to due with his new shell growth coming in darker. You can see he does still have some lighter marbling, but it’s surrounded by darker, black, newer shell growth.
I think, at least in Koopa’s case, it also has to due not so much with the marbled areas fading, but that they have become stained/dirty over time. Red foot tortoises are messy! Mine love digging and burrowing in their outdoor enclosure and their shells get very dingy over time. Sometimes Koopa’s shell gets so dirty you can barely see his lighter spots, but if I scrub his shell they become much more noticeable.
I’ll for sure keep you all updated on the progress of Koopa and Zamboni. I’m excited to continue to watch them grow and develop. I have to admit that I love how marbling on tortoises looks, and I was a bit disappointed that, as Koopa aged, his marbling became less intense. But, of course, it doesn’t mean I love Koopa any less! Marbling or no, he’s an awesome tortoise!