Why Does My Tarantula Have a Bald Abdomen – Is It Coming Up to Moult?

One of the most commonly asked questions about pet tarantulas relates to a bald patch on their bum, where the hair seems to have come off the abdomen. You can often see paler skin beneath, which worries many new tarantula keepers.  

What does it mean?

Is it a bad thing?

How does it happen?

And most commonly of all – does this mean that a tarantula is in “pre-moult” – i.e. it is nearing the time when it will change it’s skin? 

Let’s look at each of these topics in turn to answer any questions you may have…

Why Do Tarantulas Lose Hairs on Their Abdomen?

Many tarantulas have special hairs on their abdomen called “urticating hairs”. They’re commonly found on New World tarantulas – those from the Americas. Examples of tarantulas that have these special hairs include:

All of the above tarantula species are popular with beginners, which helps to explain why so many first time tarantula keepers are faced with this question. 

Urticating hairs are a defensive feature of tarantulas. As you might have guessed from their name, these hairs are irritating when they make contact with the skin, eyes or nose of a potential predator. 

If a tarantula with urticating hairs feels threatened then they may “kick” these hairs off by rapidly rubbing the sides of their abdomen with their rear legs. This creates a “cloud” of irritating hairs in the air, helping to scare off the potential threat.  

In small doses the loss of these hairs is barely noticeable. If it occurs more frequently then bald patches may start to become apparent. 

In other words, a bald patch on a tarantula’s abdomen generally is perfectly natural and shouldn’t be a concern. Even wild tarantulas are often found with these patches. 

What Makes Tarantulas Kick Off Their Hairs?

Tarantulas may choose to kick off urticating hairs whenever they feel threatened. The most obvious situation is when a larger animal starts to pay too much attention to them, and the tarantula worries that it may become dinner. 

As pets there are still things that might lead to a bald patch.

Firstly, some tarantulas will kick off hairs when you open their cage. They likely sense the sudden air movement, assume a large animal is nearby and respond in the only way they know how. 

Secondly, some tarantulas will kick off hairs if physical contact is made with them. Sometimes even a docile tarantula will kick off some hairs if you’re trying to pick it up or move it to another container. 

Lastly, tarantulas can kick off hairs if they get frustrated with feeder insects that have been left in the cage too long. If your tarantula isn’t hungry then a cockroach or locust might continually bumble into them, leading them to display their dissatisfaction. 

Note that tarantulas are individuals, so may respond differently. One Curly Hair might be perfectly fine while another repeatedly kicks off hairs at the slightest stimulus. 

How Do I Avoid a Bald Abdomen in My Tarantula?

If you want to avoid your tarantula getting a bald patch then the following tips can help:

  • Open the cage gently – To avoid a sudden rush of air that might set off your spider, try to gently open the lid for feeding and routine maintenance. In my experience front-opening cages like Exo Terras seem to yield less of a response than top-opening containers. 
  • Only handle when necessary – The less you try to hold your tarantula, the less likely they’ll be to kick hairs off their abdomen. 
  • Remove uneaten food rapidly – If your spider isn’t hungry then remove their prey rather than leaving it in the cage for days or weeks on end. Some keepers like to “hand feed” their tarantulas, offering a feeder insect with long tongs to see if it is accepted. Personally I don’t go this far but all uneaten food is removed promptly if not captured. 
  • Give your tarantula a suitable hide – Lastly, ensure your tarantula has one or more suitable hides where they can feel safe and avoid anything they see as a threat. 

Of course, another option is to choose a tarantula that either doesn’t have these urticating hairs in the first place (like many African or Asian species) or one that is less likely to kick off hairs. 

Should I Worry About a Bald Tarantula?

Tarantulas with a bald patch on their abdomen are perfectly normal. It does not necessarily mean that they’re either old or sick. As a result, a bald patch shouldn’t case you a great deal of worry.

At the same time, however, it could be argued that this is an indicator that their captive conditions aren’t quite right. You may want to consider ways in which your tarantula has been getting stressed recently, so you can reduce or eliminate these, leading to a happier tarantula. 

Will My Tarantula Regrow Missing Hairs?

Bald tarantulas regrow missing hairs when they moult. 

Tarantulas can change their skins at different times, though roughly once a year is normal for adult specimens. Adult males may not moult again before passing away due to old age. Younger tarantulas can moult every few months if well fed. 

The period of time you’ll have to wait until your tarantula regrows these hairs can then vary by the size, sex and species of tarantula you own.  

Does a Bald Abdomen Mean My Tarantula Will Moult Soon?

A tarantula with a bald abdomen is not necessarily coming up to moult. Indeed there really is no correlation between the two. A bald patch on the abdomen is more a sign that your tarantula has been kicking the hairs off to protect itself from a perceived threat.

Interestingly, the bald patch will typically change color when a moult is imminent. A week or two before changing their skin, you may notice that your tarantula not only stops eating but also that the bald patch turns a dark, shiny black color. This is a sign that the new hairs are forming underneath the existing skin.

In time your tarantula should change their skin, revealing a fully-furred rear end!

Richard Adams

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