Tarantula Moult Tracking: What to Log Before, During and After

For a tarantula keeper, moult day lands somewhere between exhilarating and nerve-wracking. Your spider will be completely helpless for anywhere from a few minutes to several hours, its new exoskeleton paper-soft and entirely vulnerable. Get the conditions right and the moult is uneventful. Miss the signs or leave live prey in the enclosure and the outcome can be fatal.

The moult is also the most information-dense event in a tarantula’s year. Logging it properly — before, during and after — gives you a health record that no amount of casual observation can match.

Pre-Moult Signs: What to Watch For

Tarantulas rarely moult without warning. The pre-moult period can last anywhere from a few days in spiderlings to several months in large adult species, but the signs are consistent:

Food refusal

The most reliable early signal is a sudden, sustained refusal of food. A tarantula that has been eating willingly may stop accepting prey entirely when entering pre-moult. This can last days to weeks; some large species fast for months before moulting. Do not force-feed and do not mistake pre-moult fasting for illness — context matters.

Web mat construction

When a moult is imminent — typically days rather than weeks away — most tarantulas will spin a thick, dense silken mat on the floor of the enclosure. This is the moulting platform. If you see your spider laying down an unusually thick, flat web on the substrate rather than in its typical web-hammock position, a moult is very close.

Abdomen darkening

In some species, particularly those with dark abdomens, the abdomen may deepen in colour slightly during pre-moult as new exoskeleton develops beneath the old one. This is subtle and not present in all species, but worth noting.

Behavioural changes

Pre-moult tarantulas often become less active, spend more time in or near their hide or burrow, and may seal the entrance. Some burrow-dwelling species will plug the entrance with substrate or webbing.

Critical: Remove All Live Prey

This cannot be overstated: never leave live prey in the enclosure with a tarantula that is showing pre-moult signs, is on its moult mat, or has recently moulted.

Crickets, roaches, and mealworms will attack a moulting or freshly moulted tarantula without hesitation. A spider in moult is completely immobile and cannot defend itself. A single cricket can chew through a soft, fresh exoskeleton and cause severe or fatal injury. If you placed a feeder insect in the enclosure and your spider is showing signs of moult, remove it immediately.

During the Moult

When your tarantula is ready to moult, it will typically flip onto its back or side — a position that looks alarming to new keepers but is entirely normal. The spider will then work its legs free from the old exoskeleton through a rhythmic pumping motion, expanding its body with haemolymph pressure to split the carapace.

Do not interfere. Do not touch, spray, or attempt to assist the spider unless it has clearly been stuck for several hours with no progress — and even then, consult an experienced keeper or vet before attempting anything. Handling during a moult is one of the most common causes of moult deaths in captive tarantulas.

A normal moult takes 20 minutes to three hours depending on the size of the spider. After completion, the spider will be lying next to its old exoskeleton (the “moult skin” or exuvia).

After the Moult: Timing Is Everything

The new exoskeleton is extremely soft immediately post-moult. The fangs will appear white or translucent and the abdomen will look shrunken. This is normal.

When to offer water

Offer a shallow water dish (or lightly mist the side of the enclosure for smaller species) within 24 hours of a successful moult. Tarantulas lose significant fluid during the moulting process and rehydrating promptly supports the new exoskeleton hardening correctly.

When to offer food

Do not offer food until the fangs have darkened to black, which signals that the exoskeleton is fully hardened. Feeding too early risks injury to a soft spider, and prey presented to a tarantula that cannot safely seize it may turn on the spider instead.

Approximate timelines for fang hardening:

• Spiderlings: 3–5 days
• Juveniles: 5–10 days
• Adult females: 10–14 days
• Large adult males: up to 2 weeks

Why Logging Every Moult Matters

A single moult record tells you the spider moulted on a given date. A three-year moult log tells you:

• Typical fasting duration before a moult — so you know whether a four-month fast is pre-moult or something else
• Frequency of moults — useful for monitoring growth rate, and for identifying when an adult female has begun her final maturation moult
• Post-moult hardening time — if the fangs are taking longer than usual to darken, that may indicate a nutritional issue
• Moult quality — was the old exoskeleton discarded cleanly, or did the spider struggle?

HabitatTracker’s shedding log is built for exactly this — log each moult event with stage and quality, and build the timeline that makes future moults predictable. When you ask the AI care assistant “Duchess has been fasting for eight weeks, is this pre-moult?” it reads her previous moult history to give you an answer calibrated to her specific pattern, not a species average.

Saving the Exuvia

Many experienced keepers save the moulted exoskeleton and examine it for health information:

• Deformed or asymmetric legs may indicate a regeneration issue
• Retained tissue inside the exuvia may point to a difficult moult
• Abrupt size increase between moults can be measured from the exuvia (useful for sexing sub-adults)

It dries quickly if set aside in a dry location and can be kept for months as a reference.

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This article is for informational purposes only. If your tarantula’s moult is unsuccessful or the spider appears injured post-moult, contact an exotic-species vet.