Quick answer: cork bark is the outer bark of the cork oak, stripped from living trees, and keepers use it in vivariums because it is light, it resists rot in damp set-ups and it gives reptiles, frogs, tarantulas and invertebrates somewhere to hide and climb. Rinse it before use, freeze it for at least a week if you want to cut the risk of mites, keep it well clear of basking lamps, and replace it when it crumbles or stays mouldy.
Cork bark is one of my go-to hides in isopod tubs, and the same material turns up in reptile, frog and tarantula enclosures. This guide covers what cork is, why it lasts, which animals use it and how, and two mistakes to avoid: putting it too close to a heat lamp, and baking it too hot.
What Cork Bark Is
Cork is the outer bark of the cork oak, Quercus suber, a tree of the western Mediterranean, and about half the world's cork comes from Portugal. It is stripped by hand from living trees, which grow a new layer, and felling a cork oak in Portugal needs official permission. A tree is first stripped at around 25 years old, and Portuguese law sets at least nine years between harvests.
A little over 40% of cork, on average, is suberin, a waxy material in its cell walls. The cells are closed and full of air, so cork is light enough to float, and water barely passes through it.
Why Cork Lasts in a Damp Vivarium
Cork resists rot, which is why it outlasts softer woods on damp soil. It is not mould-proof, though. A Portuguese study of cork-stopper making found mould covering damp, freshly boiled cork slabs within three or four days, and a piece that stays wet in still air will grow a surface mould in a vivarium too. Give it airflow and a chance to dry on top, and take out any piece that stays mouldy.
That durability is the difference between cork and bark that is meant to be eaten. Beech bark breaks down over time and becomes food for the isopods and millipedes as it does, so it is a consumable. Cork is furniture, and it lasts longer.
Which Animals Use Cork, and How
Ground-dwelling reptiles
Leopard geckos and royal pythons need hides at both the warm and the cool end of the vivarium, and a curved slab of cork pressed into the substrate makes a good one. Vet care sheets list logs and commercial hides rather than any one material, so cork is a choice, not a requirement. If you use a cork tube as a hide, make sure it is wide enough that the animal cannot get stuck, and short enough that you can reach most of the way into it to get the animal out.
Climbing species
Crested geckos, tree frogs and day geckos use height, and upright cork tubes and flats give them places to climb and rest. Fix every piece so it cannot slide or fall, especially in a tall enclosure.
Tarantulas and scorpions
Ground-dwelling tarantulas shelter under a cork slab, and tree-dwelling species use upright tubes. Keep structures low for ground-dwellers, which can be hurt in a fall, and avoid décor with holes a leg could catch in or sharp edges. A small curved offcut can give a spiderling cover, though the spider may bury it. Scorpions use cork slabs and tubes as retreats too. If you add a clean-up crew to a tarantula enclosure, our guide to isopods with tarantulas and slings covers which species work.
Isopods and millipedes
In an isopod tub, the underside of a cork slab stays damp, and that is where most of the colony gathers. Our article on whether to change the cork bark covers how long a piece stays useful, and if you are building a clean-up crew for a vivarium, see the isopod species that suit vivariums.
Plants
Cork is a standard mount for orchids and air plants, because roots grip it and it dries quickly between waterings, which makes it useful for planting the back of a vivarium. Our bioactive terrarium guide covers planting a set-up, and our guide to leaf litter for vivariums deals with the leaf layer on the floor.
Cork and Heat
Cork insulates, so a cork perch under a lamp can sit at a different temperature from the air around it: check the surface where the animal basks. It also starts to change chemically at about 150°C and breaks down from around 200°C, and the tip of an ordinary incandescent bulb can run at about 175°C. Cork must never touch a lamp or its guard. Every heat lamp needs a guard and a fixing that stops it falling, and fire services in Essex, Devon and London have all attended home fires started by reptile heat lamps. We found no published safe distance between cork and a lamp, so follow the lamp maker's instructions and set the height by the temperature of the basking surface.
Preparing Cork Before It Goes In
Brush it and rinse it in plain water. No home method has been shown to sterilise cork, and boiled cork can grow mould again afterwards, so the aim is to cut the risk of bringing something in, not to make it sterile:
- Freeze it in a bag for at least a week at -18°C or colder. That cuts the risk of mites rather than removing it.
- Or bake it at about 100°C for at least 30 minutes, longer for a thick piece, as a precaution, and stay nearby. Do not go hotter: cork starts to change at about 150°C, and some old advice to bake cork at 200°C would damage it.
Shop-bought cork is low risk to begin with. Use cork sold for enclosures, not floor tiles or noticeboard cork: those are made of granules glued together with resins, and they are often varnished or sealed.
Our Cork Bark
Our small cork bark suits invertebrate tubs and compact set-ups, or works as one hide among several in something bigger, and our extra-small cork bark is offcuts sold by weight, good for crevices and for spiderling cover. We do not treat the extra-small pieces before they leave us. Whichever you buy, freeze it first if you want to cut the risk of mites. For an adult snake or a large lizard, you will want bigger slabs and tubes than ours.
Frequently Asked Questions
Is cork bark safe for reptiles?
Natural cork bark is widely used in vivariums. Keep it away from heat lamps, and avoid cork floor tiles and noticeboard cork, which are glued and often sealed.
How do I clean cork bark?
Brush it and rinse it in plain water, then freeze it for at least a week at -18°C or colder if you want to cut the risk of mites, or bake it at about 100°C for at least 30 minutes.
Does cork bark go mouldy?
It resists rot, but it can grow surface mould if it stays wet in still air. Give it more airflow and a chance to dry on top, and take out a piece that stays mouldy.
How long does cork bark last in a vivarium?
It outlasts softer woods. Replace a piece when it starts to crumble or stays mouldy.
Is cork bark sustainable?
It is stripped by hand from living trees that grow it back, with at least nine years between harvests under Portuguese law.
Does cork bark float?
Yes. It is mostly air, so fix it in place or weigh it down if it goes into water.
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