Why Is My Tarantula Climbing the Glass? 9 Real Reasons
Behavior & Training
··3 min read

Why Is My Tarantula Climbing the Glass? 9 Real Reasons

It can be surprising — even worrying — when your tarantula starts climbing the walls or hanging on the glass. Tarantulas are ground-dwelling animals (especially terrestrials), so persistent wall-climbing usually means something in the enclosure is off.

This guide explains the 9 most common reasons tarantulas climb the glass, how to tell if it’s normal or dangerous, and the fast fixes every keeper should know.

1. Substrate Is Too Wet

Terrestrial tarantulas hate overly damp substrate.
If the bedding is moist, they instinctively climb to avoid it.

Signs the substrate is too wet

  • Tarantula only stays on the walls
  • Condensation on the enclosure
  • Mold forming
  • The substrate feels cold and soggy

Fix:

Let the substrate dry out by increasing ventilation or reducing misting. For most terrestrials, substrate should be slightly compact and dry, especially for desert species.

2. Substrate Is Wrong or Uncomfortable

If the substrate feels unnatural or unstable, tarantulas avoid walking on it.

Common substrate mistakes

  • Sand
  • Gravel
  • Loose coconut fiber that collapses
  • Bark chunks
  • Soil with fertilizers

Best substrate:

A mix of coco fiber + organic topsoil, packed firmly so they can burrow without the walls caving in.

3. Enclosure Is Too Small

A cramped or vertically shaped enclosure can make the tarantula climb more often.

Minimum enclosure size for terrestrials:

  • 3× the tarantula’s leg span in floor space
  • Height no more than the tarantula’s leg span (to prevent deadly falls)

If the tarantula seems restless and pacing the walls, upgrading the tank helps.

4. Lack of Hiding Spots

Without a good hide, your tarantula feels exposed and unsafe — causing stress and wall climbing.

Fix:

Add:

  • A cork bark hide
  • A half log
  • Deep substrate to burrow
  • Fake plants for cover

A secure hide almost always reduces climbing within 24–48 hours.

5. Poor Ventilation or Stale Air

Tarantulas are sensitive to air quality.
If the enclosure lacks ventilation, humidity builds up and the air becomes stagnant, prompting escape behaviour.

Fix:

Ensure:

  • Cross ventilation (holes on sides, not just the top)
  • No standing water
  • Balanced humidity depending on species

6. Mites, Mold, or Pests in the Substrate

If something is living in the substrate — mites, springtails, fungus gnats, mold — your tarantula may climb to avoid the disturbance.

Fix:

  • Spot clean mold
  • Replace contaminated substrate
  • Reduce moisture to prevent mites
  • Add isopods/springtails (bioactive cleanup crew) if appropriate

7. Hunger or Searching for Food

A hungry tarantula may climb or explore more aggressively while hunting.

Signs:

  • Frequent movement
  • Staying near the lid
  • Increased activity at night

Fix:

Offer a mealworm, dubia roach, or cricket.
If they pounce quickly, hunger was the cause.

8. Pre-Molt Behaviour

Before molting, tarantulas become restless and may climb frequently. They may also refuse food and show bald, darkened abdomens.

What NOT to do:

  • Don’t handle
  • Don’t feed
  • Don’t disturb

Climbing usually stops once molting approaches.

9. Normal Exploration (Especially for Slings & Arboreals)

Not all climbing is bad.

Normal for:

  • Arboreal species (e.g., Avicularia, Caribena)
  • Juveniles exploring new setups
  • Newly rehomed tarantulas

Some climbing is simply curiosity.

When Climbing Becomes Dangerous

For terrestrial tarantulas, climbing is risky. They have soft abdomens that can rupture from even short falls.

Seek immediate fixes if you see:

  • Constant wall-climbing
  • Ceiling hanging
  • Falling often
  • Refusing substrate completely

Fatal falls are one of the top preventable causes of death in pet tarantulas.

Fast Checklist to Stop Glass Climbing

1. Check substrate moisture

Is it too wet? Too loose?

2. Repack the substrate

Make it firm and burrow-friendly.

3. Reduce enclosure height

Fill empty vertical space with substrate.

4. Add a proper hide

They need a place to feel secure.

5. Improve ventilation

Add cross-ventilation if missing.

6. Check for pests

Replace dirty substrate.

7. Feed (if hungry)

Try a small feeder insect.

8. Give it time

New tarantulas need 1–2 weeks to settle.

FAQs

Is it normal for a terrestrial tarantula to climb the walls?

Some climbing is normal, but constant climbing usually means something is wrong with the enclosure.

How long will my tarantula climb the glass after rehousing?

Most settle within 3–7 days.
If climbing continues beyond 2 weeks, reassess the setup.

Can climbing injure a tarantula?

Yes. Falls can rupture the abdomen, which is often fatal.

Why is my arboreal tarantula climbing so much?

Arboreals naturally use vertical space, so this is normal as long as they eat and behave normally.

Should I stop the tarantula from climbing?

Never physically interfere. Fix enclosure conditions instead.

Tarantulas climb the glass when something in their environment is uncomfortable — usually wet substrate, poor ventilation, pests, or stress. By adjusting the enclosure and giving your tarantula time to settle, climbing behaviours usually fade quickly.