Humidity in a Crested Gecko Terrarium: Managing the Daily Cycle

No parameter in the hobby generates more confusion than humidity for crested geckos (Correlophus ciliatus). On one hand they come from the humid forests of New Caledonia and "need 80 % all the time". On the other, half of the health problems in this species come from enclosures that never dry out. The key is not high humidity — it is a clear daily cycle.

What happens in the wild

Crested geckos live in the lower forest layers of southern New Caledonia. Nights are cool and wet, with condensation on leaves pushing humidity close to saturation. During the day temperatures rise, leaves dry and air humidity drops to moderate values while the animal sleeps in a crevice or under a leaf.

In a terrarium you have to reproduce that variation, not its average. A constant 80 % is worse for a crested gecko than a constant 55 %, because permanently damp skin, fungal growth and composting substrate follow.

Target values

• Night (after misting): 70–90 %, holding for 3–5 hours.
• Day: 40–55 % — the enclosure must visibly dry out.
• Temperature: 22–26 °C by day, 18–22 °C at night. Above 29 °C this species is genuinely at risk — it tolerates heat far worse than most reptiles.

High heat plus high humidity is the worst possible combination: 29 °C at 85 % in a closed enclosure is ideal for bacteria and prevents evaporative cooling.

How to mist

• Evening misting, after lights out — heavy, until droplets are visible on glass and leaves. This is the main drinking source; crested geckos lick droplets rather than drink from a bowl.
• Morning misting — light, just to lift humidity for an hour or two.
• By midday the enclosure must be dry. If the hygrometer still shows 75 % at three in the afternoon, you have too little ventilation or too much wet substrate.

Automatic misting systems are convenient but drown many collections. Set two short daily cycles and verify with a hygrometer, not a hunch.

Substrate and ventilation

Substrate

A mix of terrarium soil, coco fibre and sphagnum, 5–8 cm deep, buffers water and releases it gradually. It must be damp, not wet — a squeezed handful should not drip.

Paper towel is a valid beginner alternative: hygienic and easy to judge, but it buffers nothing, so misting must be more careful.

Ventilation

A crested gecko enclosure needs cross ventilation: low intake at the front, outflow through the top. Without it vapour has no escape route. Glass boxes with one small lid vent are the worst offenders; screen tops with a vent strip above the doors work well.

Measuring

Cheap analogue dial hygrometers are 15–20 points out and useless. Use a digital hygrometer with a probe, placed halfway up and away from the mist stream. Two sensors — one high, one at substrate level — tell you more about ventilation than any guide.

Shedding problems are a symptom

Retained shed on toes and around the eyes is the classic sign of a broken humidity cycle. Note that both too dry and too wet cause it: permanently high humidity prevents the skin from drying enough to come off in one piece.

Immediate treatment: 15–20 minutes in a box with a damp paper towel (not standing water), then gently roll the remains off with a cotton bud. Never pull dry skin. Retained shed left over several cycles causes necrosis and toe loss.

Common mistakes

• Misting during the day "because it looks dry" — it breaks the cycle and wakes a sleeping animal.
• Room humidifiers instead of proper ventilation.
• A thick sphagnum layer across the whole floor.
• A heat mat under a humid enclosure.
• A glass enclosure by a summer window.

Quick checklist

1. Heavy evening misting with visible droplets.
2. Light morning misting.
3. Dry enclosure by afternoon, 40–55 %.
4. Day temperature never above 27 °C.
5. Cross ventilation with a screen top.
6. Damp, non-dripping substrate.
7. A digital probe hygrometer checked every few days.