Molting is an important part of a tarantula’s life.
When a tarantula molts it is able to regenerate lost or damaged body parts, including legs and hair. It is also the process through which a tarantula grows.
But there are also risks – molting is a dangerous time for a tarantula, where it is almost helpless against attacks from predators or parasites.
How often a tarantula molts therefore becomes a compromise between these two opposing forces.
In general, adult tarantulas molt once a year, while juvenile tarantulas molt every 3 months or so.
However, there is a lot of variation in these times, and a number of factors that can affect them.
How Often Do Adult Tarantulas Molt?
Most adult tarantulas follow a yearly cycle, largely dictated by the climate in which they live. All tarantulas of a given species in a given locality mate at a similar time, lay eggs at a similar time and molt at a similar time.
This makes perfect evolutionary sense. When tarantulas molt they don’t just shed their exoskeleton. They also molt internal parts of their body, including the lining of their reproductive organs. This means that every time a female molts, she essentially becomes a “virgin” again.
Couple this with the fact that adult male tarantulas tend to only be fertile for a short period of time (normally measured in months).
As a result, it makes sense for male tarantulas to reach adulthood at roughly the same time as the adult females are molting. In this way the females will be as “fresh” as possible, and will have a good length of time left in order to lay eggs before their next molt.
However there are variations on this theme. It is known that some female tarantulas can go more than a year between molts, particularly in captivity. This may be because the conditions they are exposed to in captivity don’t perfectly match those they would experience in the wild, so they are not “triggered” to molt when they normally would.
It seems that the slower growing (and longer lived) species are most likely to “skip” an annual molt. Tarantulas from the Brachypelma and Grammostola genera are perfect examples. It also seems that the older a female is, the more likely she is to go more than a year between molts.
Some real-life examples of molts from adult females in my own collection:
|Species||Molt #1||Molt #2||Period Between Molts (Months)|
|Brachypelma boehmei||November 2018||July 2020||19|
|Brachypelma boehmei||November 2018||February 2020||15|
|Brachypelma boehmei||February 2020||September 2020||7|
|Brachypelma boehmei||November 2018||August 2020||21|
|Chromatopelma cyaneopubescens||September 2019||February 2020||5|
|Chromatopelma cyaneopubescens||February 2020||October 2020||8|
|Grammostola pulchripes||June 2020||April 2021||10|
|Lasiodora parahybana||May 2018||May 2020||24|
|Lasiodora parahybana||May 2020||July 2021||14|
|Tlilticotl vagans||June 2019||May 2020||11|
|Tlilticotl vagans||May 2020||June 2021||13|
|Omothymus violaceopes||November 2019||September 2020||10|
|Omothymus violaceopes||September 2020||April 2021||7|
|Poecilotheria regalis||October 2019||October 2020||12|
|Poecilotheria regalis||October 2020||July 2021||9|
As we can see, while this averages out to every 12 months, there is significant variation among pet tarantulas.
How Often Do Slings and Juvenile Tarantula Molt?
Slings and juvenile tarantulas are going through the process of rapid growth. A tarantula will grow far more in a year as a youngster, in comparison to a mature specimen. As a result, they tend to molt far more frequently.
In my experience, and again with a fair amount of variation, well-fed tarantula spiderlings or juveniles tend to molt every 3-4 months on average.
Factors That Affect How Often Tarantulas Molt
A huge range of different factors can affect how often a tarantula molts, which can make “hard and fast” rules very difficult indeed. As stated, the examples given earlier show just how much variation there really is, and the conditions in which a pet tarantula is kept can have a significant impact on how often it molts.
However here are some of the biggest factors that affects the period of time between molts in tarantulas:
Some tarantula species are pre-programmed to reach adult size faster than others.
Tarantulas from the Poecilotheria or Psalmopoeus genera, for example, tend to be quite fast-growing.
In contrast many Aphonopelma or Brachypelma tarantulas are very slow growing. As molting is required for a tarantula to grow, it follows that some species will molt more frequently than others.
The more a tarantula eats, the more resources it has to pass through a molt. A juvenile tarantula fed twice a week will molt far sooner than one that is fed only once every week or two.
This has two effects. Firstly, it means that tarantula keepers who want their spiderlings to grow as quickly as possible should consider regular, frequent feeds.
On the other hand, if you buy a pair of tarantulas and want the female to mature a little earlier than the male, then feeding her more often (or in higher volumes) than the male can help make this happen.
Temperature can have a huge impact on how often tarantulas molt, and indeed exactly when they do molt.
A classic example of this is what happens during a heatwave. Suddenly social media and forums are alive with stories from keepers of all their tarantulas molting at roughly the same time.
It’s certainly something I’ve experienced in my own collection too.
If you keep your tarantulas at cooler temperatures – such as normal room temperature rather than providing some artificial heating – then you may find your tarantula molts less frequently.
A successful molt requires suitable hydration. If you’ve neglected to fill up your tarantulas’ water bowl then it may try to hold off molting until it’s able to have a proper drink.
Many of the “unusual” molting cycles in the table above were related in some way to being gravid. It seems that female tarantulas may molt at an unexpected time when they have been mated, either holding off in the hope they can lay an eggsac, or molting early to start the season afresh.
As stated previously, older tarantulas tend to molt less frequently than younger tarantulas. The same applies even among mature adults, where younger females may molt more often.
Do Tarantulas Stop Molting?
Tarantulas continue to molt throughout their lives.
Adult male tarantulas tend to die young, either through exhaustion or being eaten by an amorous female. Therefore they very rarely reach the next molt. If an adult male tarantula does live to old age then they may or may not molt again. If they do molt, this rarely ends well, with such males often losing limbs in the molting process.
Adult females, in contrast, continue to molt throughout their lifetime, though these molts may get less frequent with age.
What Happens If You Disturb a Molting Tarantula?
If you suspect your tarantula is molting then it is best to leave the creature well alone. Molting is a stressful time for your tarantula, and they’re likely to have invested considerable energy into getting conditions just right. They may, for example, spin a thick web to protect them, and choose the hide best suited to them.
The less disturbance there is during this period the better.
This means remaining quiet, avoiding physically disturbing the tarantula, and ensuring any uneaten feeder insects have been removed from the cage.
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