Tortoises & Glass

The myth surrounding tortoises and glass

I often hear, or more usually read on internet forums, that tortoises should not be kept behind any enclosure whose walls are made of glass or other non-opaque materials.  The myth assumes that if a tortoise can see through a transparent barrier it will not realise that the barrier is there at all, and as such will therefore try, in vain, to walk through it over and over again, and in doing so completely stress itself out in the process.

Unfortunately, this completely inaccurate and rather ridiculous statement is as popular today as it was when it first started to be banded around in the mid 1980s. And moreover any naysayers who try to quash the myth are often bullied into submission by the internet’s “we know best” mob-mentality of the ill-informed majority, despite the naysayer having a much more sensible and scientifically accurate opinion.

Sadly, like a bad “Chinese whisper”, the myth also has the unfortunate habit of being repeated by the most inexperienced and less-informed keepers, to other even less-informed and even less-experienced new comers to the hobby. And as such the bad advice, no matter how good its intentions, gets repeated over time.

Yet, it is in fact exactly that – a complete and total myth.
And one which I hope to somewhat dispel in this article.

Okay, so let’s start with the humble tortoise’s memory and its mental capacity to act on a memory to plan a future action.

For one to presume that a tortoise is not able to understand that a glass barrier is there, regardless of whether its transparent or otherwise, one must also presume that a tortoise’s mental capacity is lower than that say of a snake, or a lizard, or a common goldfish, for whom the myth doesn’t ever seem to apply?
Of course this is absolutely not true.

Tortoises are very intelligent animals, with some abilities akin to human abilities, and some senses actually far more acute than their human counterparts.

Lets think for a second about their short term and long term memory ability;
For example, as a kid on a pleasant summer’s day back in the 1970’s, I remember one of my pet tortoises; a male spur-thigh, just happened to discover a weakness in his outdoor fencing.
This weak spot allowed him to break free and make a bee line straight to my next door neighbour’s prize vegetable patch. There he stayed, indulging himself, until he was finally discovered.
After repairing the vulnerable weak spot in the perimeter wall he was duly returned to his pen.
I was astonished at the time to see him head straight back to the weak area again; pinpointing it with incredible accuracy, trying with all his might to break out again. This demonstrated to me he had great short-term memory.
However, what really amazed me was what happened later;

During the oncoming winter, we had extensive building work undertaken to our house and so consequently we had to move out and stay with a relative.
During this time we moved my pet to a new pen at my grandmother’s house some ten miles away from our usual home.

Around two years later, on completion of the building works, my family and I, along with my spur-thighed friend, moved back in to our home.
And we returned him to his usual pen.

The very first thing he did?..... Yes you’re right, he went straight back to the former weak spot and gave it another try to see if it had weakened enough over time for him to break free again.

This demonstrated to me that not only did he possess a good short term memory, but a great long-term memory too.
The fact he managed to recognise his old pen, pinpoint the exact spot where he once broke free, and re-try his attempts again, despite not living at home for two years and undergoing two hibernations in the process too, I thought was nothing short of incredible.

For those sci-fi fans amongst you, I liken it to those raptors in the Jurassic Park movie who would demonstrate similar pen-testing abilities.

Furthermore, in more recent times, when I used to keep and breed tortoises commercially,
I could set my watch by my tortoises’ abilities to know exactly where to be at the right times for feeding, bathing, etc; Thus, once again demonstrating incredible memory, thought processing and planning.

So, as we know a tortoise can learn, and demonstrate, the ability to recognise perimeter walls, and know which ones can offer freedom and which ones can’t, storing the information in both the short-term and the long-term memory compartments of their brains, and remembering them so accurately even after numerous years and hibernations, and using the memories to plan future actions.
We also know a tortoise can learn different times and places to arrive for activities like feeding.

Then are we really to believe that when facing a wall made of glass a tortoise somehow loses its entire mental capacity and ability to memorise the fact that its there, and thus, will constantly try, try, and try again, to walk through it?
I think not!
It makes no scientific sense.
In fact, have you ever witnessed this behaviour ever, in any animal? I certainly haven’t.
Even goldfish with a supposedly extremely short memory never demonstrate this behaviour.

As some of you will know, I have kept and bred many hundreds, if not thousands, of tortoises in my time. So I’ve been more fortunate than most to compare the behaviour of individuals, small groups, large groups, numerous species and various age ranges, all in differing types of accommodation.
The vast majority of my set-ups had at least one transparent side, and most of my adults were kept in semi-greenhouse type accommodation.
In four decades I’ve never seen a single incident of a tortoise displaying stressed behaviour as a direct result of confusion over non-opaque barriers. It simply doesn’t happen.

In all of my observations I would concur that a tortoise treats a transparent barrier pretty much the same as an opaque one; it knows it’s there!

Okay, so I’ve mentioned a tortoise’s memory and their capacity to use their memory to put a plan in to action, and how this memory would play a part in recognising previously explored barriers.

Now, for the sake of playing devil’s advocate;

Let’s just pretend that we have an unusual tortoise with a particularly poor memory. Perhaps it has a reptilian equivalent of Alzheimer’s disease, so it loses its short term ability to remember the fact that there is a transparent barrier in its enclosure....

Would it then behave in such a way in which the myth would have us believe? 

I.e. would it constantly be banging its head against the glass repeatedly trying to walk through the invisible barrier?

Well possibly, though to presume so, one would also have to presume that the tortoise is using nothing but its desperately failing memory to try to remember if the barrier is there, and for some reason is also coincidentally, definitively, not relying on its immediate senses to gauge the barrier’s existence, such as sight for example.

So, for the sake of this exercise lets presume the poor tortoise had severe memory loss combined with particularly bad eyesight to the extent it could not see reflections, or any marks on the glass, rendering the barrier completely invisible to the tortoise’s eyes.
Would it then behave in a stressed manner towards the glass, not understanding its presence?

Well maybe, however, unlike humans, who predominantly rely heavily on their sense of vision, a tortoise on the other hand relies predominantly on the sense of smell, just as much, or even more so, than sight.

So, even if a tortoise can’t use its memory to remember that an invisible barrier is there, and can’t use its eyes to detect any visual evidence of it being there, it can still rely solely on its excellent sense of smell, literally smelling the fact that a barrier is there!!!....
And that’s something that we humans certainly couldn’t do.

So in conclusion I would suggest, in reality, the only tortoise that would possibly become stressed or confused about itself not being able to walk through a glass partition, would be a tortoise which has no sense of smell, poor eye sight and no memory!
A very poorly tortoise indeed!

Of course this doesn’t mean that a tortoise will entirely avoid a glassed area. They will check it out and test it out in exactly the same way as they would any other barrier. This is normal.
They will also be inquisitive as to what they can see through it, in the same way as a lizard, fish, hamster or caged canary would. But this should not be confused as stress, unless you apply the same blinkered logic to every single animal we keep in captivity.
But if you do happen to witness a tortoise which is perpetually pacing up and down next to a barrier, transparent or otherwise, then one should assume that the real stress behaviour here is the fact that the owner isn’t providing enough stimuli for the tortoise to engage with; “The caged tiger syndrome”, rather than presuming it’s due to the mystical properties of invisible barriers.

So anyway where did the myth about the glass come from in the first place?

Well, back in the 1980’s there was a book published on the care of Mediterranean tortoises.
Although it was thought by many at the time to be something of a leading authority, sadly we realised as time went by that some of the statements contained within the book left a lot to be desired, and some statements were absolutely endangering to the poor tortoise.

For example the book said that healthy tortoises don’t drink.
This led to owners not providing fresh drinking water. And of course we know healthy tortoises do drink, and moreover drink copious amounts when the opportunity arises.

It also advised the reader to give their pets high protein items such as peas and beans, and of course we now know that Mediterranean species should definitely not be given high protein diets.

Well, it was also this book that sparked the myth that if a tortoise can see through something, it will try to go through it, stressing itself in the process.

Of course this sweeping statement should have only applied to obstacles such as wire fences and chicken-mesh type pens. Because with these types of pens a tortoise can not only see through it, but more importantly smell through it and feel their way through it too, and so observations of tortoises with their heads and limbs poking through the mesh was very real, as they tried “raptor-style” to test for possible weaknesses.
Solid structures, such as glass, polycarbonate, acrylic, etc, regardless of their transparency, create physical boundaries which a tortoise cannot smell through, nor feel through, to the other side, and once it recognises that the barrier is there, will treat it the same as any other opaque barrier.

Well, I hope this short article helps shed a little light on the myth, and also hopefully gives some people the courage to stand up to some of the nonsensical “advice” being forced upon unsuspecting newcomers to the hobby, which we see all too regularly on the internet these days.