If you keep tarantulas long enough, you’ll eventually walk into the room and find your spider lying completely still on its back with its legs curled in the air. Your first instinct is likely panic—but if you know what a moult looks like, your second instinct will be relief. Moulting is one of the most extraordinary processes in invertebrate keeping: the tarantula crawls entirely out of its old skeleton, emerges larger, softer, and briefly vulnerable, and then spends the next few days hardening into a brand-new exoskeleton.
Shadow, Dusk, and Onyx—our three resident tarantulas at Toronto Reptiles—have each moulted in our care, and every time it’s the same story: an anxious hour watching the process, then a few days of leaving them completely alone while they harden. Moulting is one of the biggest risk windows in tarantula keeping, not because anything usually goes wrong, but because the most well-intentioned keeper instincts (checking on them, offering food, handling) are exactly the wrong things to do at exactly the wrong time.
This guide covers everything you need to know: the pre-moult signs that tell you one is coming, what actually happens during the moult, how to respond (and how not to), and the warning signs that indicate something has gone wrong. Whether your tarantula is a Chilean rose that moults once a year or a fast-growing juvenile that sheds every few months, the fundamentals are the same.
Key Takeaways
- Moulting (also called ecdysis) is how tarantulas grow—they shed their entire exoskeleton, including the lining of their fangs, book lungs, and digestive system.
- The most critical rule: do not disturb a moulting tarantula. No handling, no feeding, no tapping the enclosure. A tarantula interrupted mid-moult can die from a failed shed.
- Pre-moult signs can appear weeks before the actual event—fasting, darkening abdomen, and sealing the burrow entrance are the main ones to watch for.
- Post-moult fangs are white and soft for days to weeks—never offer live prey until the fangs are fully dark and hardened. A live cricket can injure or kill a freshly moulted tarantula.
- The empty exuvia (shed skin) is a valuable health record—it can confirm sex, reveal parasites, and show whether the moult was clean and complete.
What Is Moulting and Why Does It Happen?
Tarantulas, like all arachnids and insects, have an exoskeleton—a rigid external shell made primarily of chitin that provides structure and protection. Unlike vertebrates, this shell cannot grow continuously. Instead, the tarantula periodically sheds it entirely, emerging with a soft new exoskeleton that hardens over the following days to weeks.
This process is called ecdysis or moulting. During a moult, the tarantula doesn’t just shed the outer shell—it pulls out the inner lining of its entire body cavity, including the delicate lining of the book lungs (the breathing organs), the entire digestive tract, and the fang sheaths. This is why a moult gone wrong is so dangerous: the animal is essentially crawling out of itself.
Each moult produces a measurable increase in size. Juvenile tarantulas moult frequently as they grow toward adult size. Adults moult less often—sometimes only once every one to three years—primarily for regeneration and maintenance rather than growth. Female tarantulas moult throughout their lives; mature males typically moult very rarely after their “ultimate” or mature moult, which signals sexual maturity.
Pre-Moult Signs: How to Know One Is Coming
Tarantulas don’t moult suddenly. The process builds over days to weeks, and there are reliable physical and behavioural signs that tell you it’s approaching. Recognising pre-moult is important because it changes how you manage the enclosure during that window.
Food Refusal
The most consistent pre-moult sign is fasting. A tarantula that normally takes prey readily will suddenly refuse food entirely. This can last anywhere from two weeks to several months before the actual moult, depending on species and individual variation. Do not force-feed or interpret fasting as a health problem—it’s almost always pre-moult behaviour in an otherwise healthy specimen.
Darkening Abdomen
A healthy tarantula typically has a plump abdomen with visible setae (hairs). In pre-moult, the abdomen often darkens noticeably—sometimes dramatically, appearing almost black in species with normally lighter colouration. This darkening is the new exoskeleton visible through the relatively thin abdominal skin. If you see a darkened abdomen alongside food refusal, a moult is likely within weeks.
Webbing and Burrow Sealing
Many tarantulas, particularly burrowing species, will seal the entrance to their burrow with a mat of silk before moulting. Arboreal species may create a silk hammock or pad on the enclosure floor. This is the animal preparing a safe, enclosed space for the vulnerable moulting process. If your tarantula bricks up its burrow or goes completely silent behind a wall of silk, assume pre-moult and leave it alone.
Lethargy and Position Changes
In the final days before a moult, the tarantula often becomes very still and may position itself flat on the substrate. This is the point where some keepers mistake pre-moult lethargy for illness or death. A tarantula that is otherwise healthy, has been eating until recently, and shows a darkened abdomen is almost certainly in pre-moult—not dying.
How Often Do Tarantulas Moult?
Moulting frequency varies significantly by species, age, temperature, and individual metabolism. The table below gives general ranges for the species types most commonly kept—including the species you’d encounter at a Toronto Reptiles experience.
| Tarantula Type / Age | Moult Frequency | Notes |
|---|---|---|
| Spiderlings (slings, all species) | Every 4–8 weeks | Growing rapidly; moult frequently regardless of species |
| Juvenile (1–3 years) | Every 2–6 months | Slows as the animal approaches adult size |
| Sub-adult female | Every 6–18 months | Approaching adult size; larger moults, longer recovery |
| Adult female | Every 1–3 years | Some species (Chilean rose, Grammostola) moult infrequently; may fast for months beforehand |
| Adult male (post-ultimate moult) | Rarely or never again | The mature moult is often the last; males typically live 1–2 years post-maturity |
| Curly hair (Tliltocatl albopilosus) | Every 8–14 months (adults) | Moderate; reliable pre-moult signs |
| Greenbottle blue (Chromatopelma cyaneopubescens) | Every 6–12 months (adults) | Faster-metabolising; slightly more frequent |
Temperature influences frequency significantly—warmer enclosures accelerate metabolism and increase moult rate. If your tarantula is kept slightly cooler than optimal, it may moult less frequently. This isn’t necessarily a problem, but it’s worth understanding if your specimen seems to be on a slower schedule than what you read online.
The Moulting Process, Step by Step
Once the moult actually begins, the process moves relatively quickly—typically 15 minutes to a few hours for most adult tarantulas, though large species or difficult moults can take longer. Here’s what you’ll observe:
- The tarantula flips onto its back. This is the moment most keepers panic. It’s completely normal. The tarantula needs to use gravity to help pull itself free of the old exoskeleton—lying upside down is the correct position.
- The carapace (top of the cephalothorax) begins to separate. You’ll see a split forming at the junction between the carapace and the body. This is ecdysis beginning.
- The old exoskeleton peels back. The tarantula begins muscular pumping movements—rhythmic contractions that gradually push the new body free of the old shell. This is the most physically demanding part of the moult and the phase where intervention is most dangerous.
- The legs pull free. One by one, the tarantula extracts its legs from the old exoskeleton. This is where failed moults most commonly occur—if a leg becomes stuck, the animal can lose a limb or die trying to free it.
- The tarantula separates fully from the exuvia. The old shell is left behind as a complete (or nearly complete) hollow replica of the animal. The tarantula lies beside it, pale and soft.
- Recovery begins. The tarantula will lie still for several hours while the new exoskeleton begins to harden. Do not touch, feed, or disturb the animal at this stage.
What to Do (and Not Do) During a Moult
The list of what not to do is more important than the list of what to do. Most keeper intervention during a moult—even well-intentioned—causes harm.
Do
- Leave the enclosure alone. Vibration can disrupt the moult at a critical stage. Move quietly around the enclosure.
- Ensure the enclosure has adequate humidity. Dry conditions are one of the leading causes of difficult moults. If the humidity in the enclosure has been low, a light misting of the sides (not directly on the animal) in the days before a moult is appropriate. Once the moult starts, do not open the enclosure.
- Remove live prey immediately. If there’s a live cricket or roach in the enclosure when the moult starts, get it out as fast as possible without disturbing the animal. Live feeders will attack a moulting tarantula.
- Watch from a distance. You can observe without interfering. If something looks wrong (see below), make a decision about whether to intervene.
Do Not
- Handle the tarantula. No exceptions, even if the moult looks like it’s going wrong. Premature intervention is almost always more dangerous than the problem you’re trying to solve.
- Offer food. The tarantula’s fangs are soft and non-functional immediately after moulting. Live prey is a genuine danger.
- Attempt to “help” the tarantula free a stuck leg unless it has been completely motionless for more than an hour and you have reason to believe it is dying. The risk of causing a fatal injury by helping is usually higher than the risk of leaving a stuck limb.
- Assume the tarantula is dead. A pale, motionless tarantula lying on its back beside its old skin is completing its moult. Give it 24 hours before drawing any conclusions.
Post-Moult Care: The Recovery Window
Once the moult is complete, the animal enters a recovery window that can last anywhere from a few days to several weeks depending on species and size. During this period, the new exoskeleton gradually hardens—a process called sclerotisation.
The clearest indicator of hardening is fang colour. Freshly moulted tarantulas have white or pale yellow fangs. As the exoskeleton hardens, the fangs darken—moving through yellow, orange, and eventually to their species-normal dark brown or black. Do not offer any food until the fangs are fully dark and hardened. This is non-negotiable. A live feeder insect will attack and can injure or kill a soft-bodied, non-functional spider.
During the post-moult window:
- Maintain humidity at the appropriate level for the species—the new exoskeleton is somewhat moisture-sensitive as it hardens
- Do not handle the tarantula; the new exoskeleton is fragile and a fall at this stage can be fatal
- Provide a water dish if the species normally has one—the animal may drink during recovery
- Remove the exuvia within a day or two once you’re confident the moult is complete
What the Exuvia Can Tell You
The exuvia (the shed exoskeleton) is more than a keepsake—it’s a diagnostic tool. Experienced keepers examine the exuvia after every moult for several reasons:
Sex Confirmation
The exuvia of a female tarantula contains a visible spermathecae—a small, paired structure visible on the inside of the abdominal section when the exuvia is gently flattened and held up to light. This is the most reliable method of sexing a juvenile tarantula that isn’t yet showing secondary sexual characteristics. Males lack the spermathecae and will eventually show tibial hooks (mating spurs) and embolus structure on the pedipalps after their mature moult.
Completeness Check
A complete, intact exuvia with all eight leg sheaths present means the moult went cleanly. A missing leg section or torn exuvia is worth noting in your records—it may indicate humidity was too low, the substrate too hard, or that the animal has some kind of physical issue to monitor.
Parasite Indicators
Mites sometimes attach to a tarantula’s exoskeleton between moults. Examining the exuvia under good light can reveal mite casings or the mites themselves. If you find mites, the enclosure needs a deep clean.
When to Be Concerned: Warning Signs
Most moults go smoothly. When something does go wrong, the table below outlines the warning signs and appropriate responses:
| Warning Sign | What It May Indicate | Response |
|---|---|---|
| Moult has been ongoing for more than 4–6 hours with no visible progress | Stuck moult (dysecdysis); often humidity-related | Lightly mist the sides of the enclosure to raise humidity; do not touch the animal unless it has been completely motionless for 1+ hour |
| A limb appears stuck in the old exoskeleton | Partial failed moult | Monitor for 30–60 minutes; if no movement at all and limb is still caught, extremely careful assistance with damp cotton swab may be necessary—contact an experienced keeper or exotic vet first |
| Tarantula has been on its back for more than 24 hours with no sign of progress | Moult failure; animal may be too weak to complete the process | Consult an exotic vet experienced with invertebrates |
| Animal appears to have moulted successfully but collapses when attempting to right itself | Dehydration or underlying health issue; exoskeleton may be hardening incorrectly | Ensure water access; monitor closely; consult exotic vet if no improvement in 24–48 hours |
| Significant haemolymph (clear or pale blue-ish fluid) loss during the moult | Injury to soft tissue during the moult process | Do not disturb; keep the enclosure stable; monitor. Minor seepage is not always fatal. |
Moulting Across Different Species
Most of the rules above apply universally, but a few species-specific notes are worth flagging:
Grammostola and Aphonopelma species (e.g., Chilean rose, Texas brown): These are notoriously slow-metabolising tarantulas that can fast for 12–18 months before a moult. Do not interpret an extended fast in one of these species as a health emergency unless other warning signs are present. Shadow, our Chilean rose, fasted for nearly a year before her last moult.
Arboreal species (e.g., Psalmopoeus, Avicularia): These often moult within a silk tube on the side or top of the enclosure rather than on the substrate floor. The moult position may look different—sometimes vertical—but the process and rules are identical.
Old World species (e.g., Horned baboon, Asian ornamentals): Old World tarantulas tend to be faster and more defensive; post-moult recovery times can be shorter, but the soft-fang rule still applies. Do not offer food until fangs are fully darkened regardless of how quickly the animal seems to recover.
Tarantulas missing limbs: A tarantula that has lost a limb to a previous failed moult or injury will often regenerate that limb over one to three moult cycles, with each iteration producing a progressively more complete replacement. The regrown limb is typically slightly smaller than the original after the first moult and approaches normal size by the second or third.
Frequently Asked Questions
My tarantula is on its back. Is it dead?
Almost certainly not, if it’s otherwise been healthy. A tarantula lying on its back is the classic moulting position. A dead tarantula typically curls its legs inward underneath its body rather than stretching them upward and outward. Wait, watch from a distance, and do not touch the animal for at least 24 hours.
How long does a tarantula moult take?
The active moulting process—from flipping over to pulling fully free of the old exoskeleton—typically takes 15 minutes to 2 hours for most adult tarantulas. Larger species or difficult moults can take longer. If the process has been ongoing for more than 4–6 hours with no visible progress, that’s a warning sign.
When can I feed my tarantula after a moult?
Not until the fangs are fully darkened—not pale yellow, not orange, but the species-normal dark brown or black. For small species this might be 5–7 days post-moult. For large, slow-hardening species, it can be 2–4 weeks. Offering a live feeder before hardening is complete is one of the most common causes of keeper-caused tarantula death.
Should I remove the exuvia?
Yes, within a day or two of the completed moult. Left in the enclosure, the exuvia provides shelter for mites, fungus gnats, and other pests. Examine it first (sex check, completeness check), then remove it. Some keepers preserve the exuvia as a record of each moult.
My tarantula hasn’t eaten in months. Is this pre-moult or a health problem?
Extended fasting in otherwise healthy tarantulas is almost always pre-moult. Look for a darkened abdomen, which is the most reliable corroborating sign. If the abdomen looks shrivelled rather than darkened—indicating dehydration—that’s a different problem. Ensure the animal has access to a water dish and mist the substrate corner lightly. If the abdomen is plump and dark, the animal is almost certainly pre-moult.
Can I handle a tarantula during pre-moult?
It’s strongly not recommended. Pre-moult tarantulas are internally soft and vulnerable—the new exoskeleton is developing beneath the old one. They are also typically more defensive during this period. More practically: you can’t reliably know exactly when the moult will begin, and a tarantula that starts moulting mid-handling is a dangerous situation for both you and the animal. Suspend handling entirely once you see reliable pre-moult signs.
My tarantula lost a leg during the moult. What do I do?
In most cases, do nothing except maintain optimal care. Tarantulas can survive with missing limbs and will regenerate them over the next one to three moult cycles. The missing-limb side of the body will produce a small, incomplete leg at the first post-injury moult; subsequent moults produce progressively larger, more complete replacements. If the wound is actively bleeding haemolymph, a tiny dab of corn starch or tissue paper can help clot it—but this is rarely necessary.
Is it normal for my tarantula to not eat for weeks after a moult?
Yes. Many tarantulas refuse food for several weeks post-moult even after the fangs have fully hardened. The digestive system is re-establishing itself, and the animal may simply not be hungry. Continue offering prey every week or two and remove uneaten prey after 24 hours. Most specimens resume normal feeding within 4–6 weeks of a successful moult.
See a Tarantula Up Close at a Toronto Reptiles Experience
Shadow, Dusk, and Onyx have all gone through moults in our care—and that experience of watching the process firsthand, understanding what’s normal and what isn’t, is part of what makes us confident bringing them to schools and parties. If you’re curious about tarantulas and want to spend time with ours before deciding whether one is the right pet for you, a Toronto Reptiles visit is a good way to get hands-on experience with no commitment. You can read more about our ambassador animals or find out what a reptile experience looks like through our birthday party and experience packages.
Curious about what else goes into keeping tarantulas well? Our complete tarantula care guide for beginners covers housing, temperature, humidity, diet, and handling from the ground up.