A question we are asked often is: “Will my gecko get impaction?”, “the vet/breeder told us to use paper towels/repticarpet because of the risk of impaction.” I’ve even had variations of “you shouldn’t use loose substrates because the animal will get impaction!” shouted at me angrily while I’m speaking to a customer about something completely unrelated. (Apparently loose substrate discourse is the reptile-keeping equivalent of bringing politics to Christmas dinner.)
So, before we do anything else, let me make this bold statement…
In its natural environment, where your pet originally comes from, there are loose substrates everywhere. Sand. Soil. Dust. Dirt. Rocks. Leaf litter. Nature, shockingly, did not carpet the desert in reptile-safe kitchen roll.
A brief interlude from what will probably turn into a rant…
What is impaction?
Impaction is when a substance forms a blockage in the intestines which prevents the normal passage of food and fluid through the gut. This blockage is more serious than just a touch of constipation – it can be incredibly painful and potentially fatal. Think “traffic jam on the M25,” except instead of commuters angrily drinking coffee, it’s undigested food and substrate refusing to move.
So, what causes impaction? The shortest answer is anything that goes into the mouth and, for many reasons (as we will discuss), can’t get out the other end. This mass in the gut puts pressure on nerves and blood vessels, causing not only stress and discomfort, but true pain. This can force the animal into clinical shock which will, inevitably, lead to death.
As any veterinarian will undoubtedly tell you, impaction can kill animals. Every vet has a story of opening an animal up (either attempting to save it or during an autopsy) to remove a stinking mass of undigested food and substrate. So the answer is obvious: remove the substrate, remove the danger… right?
Well, not exactly.
I can guarantee you, if you look closer into almost any single case of impaction on the internet, you will find far more husbandry issues than simply “my animal ate the substrate.” I have been involved in more than 100 cases involving impaction of some description, from crested geckos and anoles to tegus and monitor lizards, and in every single instance there were husbandry discrepancies which led to the decline in the health of the animal in question.
In other words, substrate is often the final straw, not the root problem. It’s less “evil sand assassin” and more “tiny grain-shaped accomplice.”
Reptiles: 250 million years of proving people wrong
Reptiles inhabit every continent on the planet (with the exception of Antarctica, because even reptiles know when somewhere is too cold). They are one of the most adaptable and versatile groups in the animal kingdom. Having evolved for more than 250 million years, reptiles have a glorious history and, thanks to their versatility and ability to thrive in close proximity to us, a promising future.
So please explain to me — and use little words, I beg you — how these animals can’t handle a loose, soil-based substrate?
As I’m sure you’re aware, nothing is ever that simple. Impaction can be caused by any one or a combination of the following issues:
- Incorrect temperatures (normally too low)
- Dehydration
- Internal parasites
- Infection
- Physical trauma
- Neurological issues
- Tumours or growths
- Mineral deficiency
Healthy animals will generally be able to pass indigestible matter through their gut without incident. An animal with a pre-existing health issue or poor husbandry, however, may suffer from impaction. Removing the substrate from an animal’s enclosure is akin to giving paracetamol for a broken ankle. You are dealing with the symptom of a problem, not addressing the problem itself.
Or, to put it another way, blaming all impaction on substrate is like blaming shoes for someone tripping over while blindfolded, dehydrated, and carrying a wardrobe upstairs.
Why would a reptile deliberately eat substrate?
Aside from accidentally picking up substrate while feeding, why would an animal deliberately eat substrate?
Have you ever seen nature documentaries where animals of all shapes and sizes — elephants, tapirs, birds and lizards — visit specific spots to literally eat dirt and mud? These places are rich in minerals that may be missing from the animals’ diets. When their bodies detect the deficiency, they descend upon these mineral deposits like shoppers finding discounted chocolate at Tesco.
Quite a simple equation:
Low in minerals → eat dirt → absorb minerals → carry on being alive.
This is one reason our captive reptiles may actively eat their substrates: they are mineral deficient.
However, this process requires other factors to allow proper mineral absorption. Specifically: heat, UV exposure, and hydration. (There are also a whole bucket load of chemical and physiological processes involved, but I’m not smart enough to explain them without accidentally reinventing alchemy.)
If your reptile is at the correct temperature and has access to UV but too little mineral content in the diet, it becomes deficient.
If it has the correct supplementation but no UV, it becomes deficient.
If it has minerals and UV but is too cold, it becomes deficient.
Basically, reptiles are tiny biological chemistry sets with attitude problems.
If any of these parameters are missing, the animal cannot process the substrate properly, and it simply sits in the stomach doing nothing. Because the animal can’t absorb the minerals, its brain still demands that it consume more substrate to replace the missing elements. The animal becomes weaker and weaker, the stomach swells, and the digestive tract struggles to move the indigestible material along.
All of the animal’s internal organs begin to suffer from a lack of vitamins and minerals and the whole system sputters, stalls, and struggles to restart like an old Skoda someone found in a garage in 1997.
Dehydration: the sneaky culprit
The next most common cause we see is dehydration. Reptiles — especially desert-dwelling lizards popular as pets, such as leopard geckos and bearded dragons — are incredibly efficient at making use of available moisture. They reclaim hydration from their food and often rarely drink directly. In fact, many reptiles don’t appear to drink from still water at all.
Unfortunately, this can lead to chronic dehydration, which brings with it many unpleasant and life-threatening conditions.
Despite the fact that so many popular reptile species come from arid environments, they have evolved alternative methods of hydration — such as collecting moisture from early morning fogs and dew. This can be replicated in captivity by misting your reptile regularly, especially if you rarely see it drink.
For example, we do this with our bearded dragons on a bi-weekly basis. Twice a week we spray around the animal (preferably the cooler section of the vivarium) and allow it to drink as much as it wants. Think less “tropical rainstorm” and more “spa retreat for tiny judgmental dinosaurs.”
Reptiles also possess a highly developed water reclamation system operating in the intestines as food moves through the digestive tract. If waste sits in the colon for too long, water continues to be drawn from it until what remains resembles a small rock. This hardened mass, known as a fecalith, can itself become a blockage.
Which is an incredibly scientific way of saying: the poo turns into a brick.
Neurological issues: when the brain says “eat the carpet”
Neurological problems often raise questions when mentioned alongside impaction. How does an animal with a neurological issue suffer impaction?
Simple answer: they eat rocks.
But not just rocks. Paper. Cardboard. Dirt. Elastic bands. Clothing. Hair bobbles. Toys. Batteries. The list goes on and on like a reptilian version of a toddler unsupervised for five minutes.
Animals with neurological issues are often seen eating anything they can get their jaws around. A wonderful example is one of our own breeding animals — Blue.
Blue is a 15-year-old melanistic leopard gecko and he is, as my dad used to say, “not the full shilling.”
He hunts his food, finds water, digs, climbs, and explores his enclosure exactly as a healthy leopard gecko should. But the second he sees something new in his enclosure, he immediately decides it belongs in his mouth.
It starts with an exploratory lick — reptiles use their Jacobson’s organ to “taste-smell” their environment — but after that it escalates rapidly into full-blown “I’m absolutely going to eat this” mode.
Further observation suggests Blue suffers from a mild neurological issue. Nothing severe like that seen in certain problematic morphs, but enough twitching and stargazing that you can clearly see something isn’t quite right upstairs.
He is, scientifically speaking, an adorable little idiot.
Internal parasites
Internal parasites are not something people often consider with captive reptiles, but they absolutely can be a problem. Particularly if your animal:
- spends time outside grazing,
- enjoys the occasional snail or slug snack,
- is wild caught (still somehow a thing in this day and age), or
- has shared accommodation with a rescue or wild-caught animal.
Parasites are exceptionally good at finding ways into animals to complete their lifecycle. Honestly, if parasites put the same energy into a normal career path, they’d probably run multinational corporations or the government.
Impaction occurs either when there is an especially heavy parasite load or, in some cases, after deworming, when the sheer number of dead parasites creates a blockage.
Preventing impaction in your reptile
1 – Temperature
Make sure your habitat is at the correct temperature with an appropriate gradient between basking spot and cool end. Reptiles are ectothermic — they literally run on external heat. A cold reptile trying to digest food is basically me trying to do maths before coffee.
2 – UV exposure
Provide species-specific UVB levels. UV lighting is not decorative mood lighting for lizards; it is absolutely essential for many species to process calcium and maintain healthy bodily functions.
3 – Supplementation
Ensure your reptile receives the correct mineral and calcium supplements for its species. Reptiles cannot survive on vibes alone, despite what some internet “experts” may imply.
4 – Hydration
Keep your reptile properly hydrated and understand how the species naturally drinks in the wild. Would it drink from puddles, raindrops, dew, or moisture on leaves?
And no, they do not absorb water through their vents while bathing. Another myth busted. If that worked, I’d solve my own hydration problems by sitting in the bath with a sports drink.
5 – Reduce accidental ingestion
Feeding a Horsfield tortoise wet greens directly on fine sand is probably not a great idea. Use a bowl or slate instead. Even the smartest reptile has occasional “fork dropped on the floor” moments.
6 – Be careful where you get advice
The internet is a marvellous tool, but there are online “experts” with all of five minutes’ experience who feel entirely qualified to criticise other keepers. Avoid Facebook groups and forums dedicated to reptile “care” if they exist solely to shout at strangers.
Half the time you ask a simple husbandry question and suddenly Karen from Swindon is typing in all caps about coconut fibre like she’s defending a doctoral thesis.
We all have to get it right for the sake of the animals, and good keepers constantly research reptile behaviour, natural habitats, and evolving husbandry standards to improve the care they provide.
Final thoughts
As always with reptiles and amphibians, prevention is the best cure. Correct heating, appropriate UV lighting, proper supplementation, good hydration, and a clean healthy lifestyle will help ensure your scaly (or slimy) friend stays happy and healthy throughout its life.
And dear reader, don’t be tempted by the chaos of reptile "care" Facebook groups. You’ll go in asking about substrate and emerge three hours later in a blood feud with a man called Jeff whose bearded dragon lives on newspaper and is fuelled by resentment.
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