Tarantulas and moulting

Tarantulas are a species of invertebrate that has a hard exoskeleton (external skeleton) covering their bodies. Because this skeleton is on the outside of the body rather than the inside, in order to grow as they age, periodically they must shed the existing exoskeleton for a larger one, to provide room to grow and develop. This process is known as moulting, or to give it its scientific name, ecdysis.

Moulting now and again is a perfectly natural process for the tarantula, and something that all owners of pet tarantulas in captivity should be aware of. Moulting usually happens naturally and without incident, although it is important for the owner of the pet tarantula to understand what happens during moulting, know how to identify an impending moult, and how to recognise any potential problems along the way.

Read on to learn all about tarantulas and the moulting process.

Why do tarantulas moult?

Tarantulas must moult their hard exoskeleton in order to grow, and this process occurs on an ongoing basis throughout the life of many tarantulas, and not just when they are young. If a tarantula is unable to moult or suffers from problems when moulting, this can potentially prove dangerous or even life threatening for your tarantula, as they become stuck in a partially shed “skin” that is too small for them, inhibiting their normal growth, movement and development. You could think of it as wearing a pair of shoes that are too small for you; and never being able to take them off.

How often do tarantulas moult?

Juvenile tarantulas moult frequently as they grow, sometimes as often as every month or so at some stages, but certainly several times a year. When fully grown, male tarantulas do not typically moult once mature, while female tarantulas continue to moult throughout the duration of their lives, generally every year or two.

Indications of an impending moult

Once you are aware of moulting and know what signs to look out for, it is relatively easy to identify an impending moult in your pet. In the stages leading up to a moult, be on the lookout for the following signs in the days leading up to moulting:

• Appearing lethargic and less active than normal
• Having difficulty climbing about or moving as freely as normal
• Losing interest in food and not eating
• Appearing darker over the abdomen (although this can be difficult to spot in species of tarantula that are already rather dark in this area)
• In some cases, tarantulas will develop a bald spot on the abdomen
• Having a generally dull-looking appearance and colour
• Weaving more webs or silk than usual to protect themselves during moulting

How long does it take for a tarantula to moult?

Once moulting itself begins, it is usually all over and done with relatively quickly. Moulting can take anything from an hour to around 12 hours, and sometimes up to 24 hours to complete.

Tarantulas usually lie on their backs to moult, which can appear to the uninitiated as if the spider has keeled over and died! This is not the case, however; the only reason that you might find your tarantula dead on its back is if it happens to die during moulting. The usual death pose for the tarantula is sitting with its legs curled up under it.

Taking care of your tarantula when moulting

Moulting can be a stressful time for tarantulas, and while they are undergoing a moult and for some time afterwards until the new exoskeleton hardens, they are vulnerable to attack from predators and even their normal prey!

You should ensure that the humidity within your tarantula’s tank is at its optimum level to make moulting easier, and do not offer food to your tarantula during this time. As your tarantula will remain vulnerable for a few days before moulting and around a week afterwards until their new exoskeleton hardens, it is vital to ensure that no uneaten live food is left in the tank, which may pose a risk to your tarantula.

After moulting, it takes several days for the tarantula’s new fangs to harden off enough to be able to eat prey, and so you should leave it a week after moulting before offering food.

Problems with moulting

Tarantulas generally shed their exoskeleton in one complete piece, which appears at first glance to be a whole second spider, and can be interesting for the tarantula owner to keep.

Occasionally, the tarantula may have problems shedding the old exoskeleton, or may shed it in individual pieces. While this often indicates that something is amiss, your tarantula will usually be able to resolve this problem themselves without intervention.

• Monitor the humidity levels within the tank, as if the atmosphere is too wet or particularly, too dry, this can lead to problems moulting.
• If your tarantula still retains part of the old exoskeleton after a moult but appears to be able to move around freely and has unobstructed ability to eat and drink, this is usually fine but indicates that the moulting conditions were not optimum, something that you should take care to address before the next moult.
• If your tarantula is stuck for a day or more in a partially shed skin and is unable to move properly or is likely to have problems eating and drinking, you may have to take some action.
• A special exotics veterinary surgeon or an experienced tarantula handler may be able to help you to remove the stuck exoskeleton with forceps, although this is not a procedure to be undertaken lightly.
• A last resort in cases of a firmly stuck exoskeleton may involve amputation of one or more of the limbs that are impeding the shed, although again, this is extremely stressful and potentially dangerous for your tarantula, and something that you should seek advice from an expert on before giving any consideration to.

Getting veterinary care and advice for tarantulas and other exotic pets can be a challenge, as is the case for all venomous animals. So it is wise to have established a suitable vet and support network of arachnid enthusiasts who are knowledgeable and can provide help and advice in the case of any problems, before they arise. More advice on this is available here.