Tarantulas normally lose their hair for one or two reasons: either the hairs have been kicked off as a defensive mechanism, or the hairs have rubbed off naturally during daily life.
Let’s look at these two reasons in more detail…
Defensive Hair Loss in Tarantulas
Many tarantulas from the Americas possess special hairs known as “urticating hairs”. These are most commonly found on the abdomen of the tarantula. Viewed under a microscope these urticating hairs often look barbed in design.
Urticating hairs can cause much irritation when they get onto the skin of mammals. The discomfort can be even worse if the barbed hairs get into the eyes, nose or mouth.
Many tarantula keepers report an unpleasant itching sensation after cleaning out their pet. This may result in an uncomfortable rash, particularly on the hands and forearms. Fortunately this irritation is usually temporary, and disappears slowly over the next few days.
These urticating hairs are used by tarantulas to protect themselves from potential predators.
They can be used in a variety of ways to accomplish this.
Most commonly they are kicked off by the rear legs, creating an air-borne cloud of irritating hairs. This can result in the bald patch seen in many tarantulas.
However these hairs may be used in other ways by some tarantulas. For example, they may be incorporated into the web of a tarantula’s eggscac. They may be added to the thick mat of web that tarantulas spin before molting. They may even be pressed directly into the skin of other animals if they feel threatened.
So the use of urticating hairs as a defense is by and large the most common reason for tarantulas to lose their hair. Fortunately, the resulting bald patch is only temporary. The next time your tarantula molts, all of these lost hairs should be regrown.
Natural Abrasive Hair Loss in Tarantulas
Less common but still observed from time to time, is hair loss due to abrasion with the natural world. Burrowing tarantulas are most prone to this issue. Constantly moving up and down a burrow, in an environment where there may be stones, rocks or tree roots, can over time lead to some hairs getting gently rubbed off.
Once again, though, just like the urticating hairs, these should be replaced the next time your tarantula molts.
Other Reasons Why Tarantulas Lose Their Hair
There is also the very unlikely reason that your tarantula may have contracted some sort of parasite. This is very uncommon in pet tarantulas, but all the same can result in hair loss in some specimens.
Should I Worry About Hair Loss in Tarantulas?
The loss of urticating hairs is perfectly normal and natural in tarantulas. It should not necessarily really be considered a cause for concern.
That said, a tarantula that has kicked off lots of hairs may have found itself repeatedly felt threatened. Only when it feels threatened will it kick off clouds of hair. It might therefore be wise to consider your husbandry strategies.
Perhaps your tarantula doesn’t have a hide where they feel safe. Perhaps you’re feeding your tarantula too frequently, or you’re not removing any uneaten feeder insects soon enough.
While a degree of hair loss is perfectly normal in these tarantulas, it is wise to try and minimise hair loss, if only to avoid unnecessary irritation and soreness for you while caring for your spider.
Do Only Old Tarantulas Lose Their Hair?
Tarantulas can lose their hair at almost any age, though it is more commonly seen in larger specimens. It isn’t the case that only old tarantulas lose their hair; even young specimens are perfectly capable of kicking off their hairs if they feel threatened.
Does a Tarantula Losing It’s Hair Mean It Is Coming Up to Molt?
One common myth is that a tarantula that has lost its hair and developed a bald patch must be coming to molt. This is not the case. While tarantulas will regrow lost hairs during a molt, the presence of a bald patch does not indicate that a moult is imminent.
Only when the bald patch turns a shiny black color will you know for certain that a molt is near. Until then, it can be months between losing some hair and a tarantula replacing it in the moulting process.