Do Tarantulas Sleep? Not Really!

You might have seen your tarantula in the same position for hours if not days and wondered if it is hurt, cold, unhappy or maybe sleeping? Well, one thing we know is that tarantulas don’t roll onto their sides or backs to take a quick nap, but they do rest.

Do tarantulas sleep? Tarantulas don’t sleep the same way that mammals do but they do have cycles of movement and respite. Tarantulas reduce their activity level, lowering their metabolic rate in order to conserve energy.

We really don’t know much about spiders and their sleeping patterns and there is still much for us to learn about arthropods in general, but spiders definitely go into some or other rest mode.

Considering that tarantulas don’t have eyelids and thus can’t close their eyes, it must actually be quite difficult for them to catch some z’s! Or is it?

Tarantula’s Mimic Sleep

Sleep, as we humans understand it, is not the same type of forty winks tarantulas will catch. Ts will reduce their activity level and this will lower their metabolic rate which in turn conserves energy.

This is very useful, especially for web-building spiders; they depend on food to come to them and often, the wait between meals is a long one.

Tarantulas are also referred to as pet ‘rocks’ because they do spend a lot of the daytime just chilling in one spot as a survival mechanism since birds and other predators looking for a snack are more likely to be active during the day.

If you’ve been a tarantula hobbyist for a while now, you will know that Ts are like computers in sleep mode; when there’s no movement for a while, the computer will postpone all activity and reduce energy.

But, as soon as you push a key, the computer will come back too life. The same happens to tarantulas; when there’s some stimulus, the T will become active quickly.

Some T owners have experienced their tarantula staying completely still when nudged a little, but after disturbing them once or twice again, they go into a slight panic without any idea what is going on – much as humans do when we are startled awake.

Since tarantulas are mostly nocturnal, we as keepers usually interact with them while they are in a rested state: we might try to feed it or move it into a container for cleaning purposes.

This will be met with inaction at first but after enough sensory input, the T will then suddenly bolt, flick hairs or lunge towards your hand.

This definitely indicates at least a period of rest, if not sleep. You can call it a stand-by state if you like and during this time, tarantulas may shut down some of its vital parts of the brain to save energy.

Judging by their quick return to reality when disturbed, it seems some selective parts of the brain stay on in order for it to ‘turn on’ immediately with the correct amount of stimuli.

Much like humans, actually, except when we sleep, our bodies go into healing mode, something which likely does not happen when a tarantula sleeps.

Tarantulas’ Brains Are Too Primitive For Sleep

Although tarantulas display behavior that looks like sleep, for example, loss of muscle tension, no movement and delayed responses to stimuli, entomologists believe that a T’s brain is too small to require actual sleep.

It’s claimed that the larger the brain, the more sleep is required to recharge it.

That being said, sleep is universal and almost all organisms require it in one form or another. Take lizards, for example, recent studies have revealed ancient roots to the human REM cycle.

Even though the electrophysiological study of sleep in small invertebrates is a complex and somewhat problematic endeavor, fruit flies have been found to sleep and any disturbance of its sleep leads to a decline in cognitive functioning.

I’m not here to compare brain sizes between tarantulas (although Ts do have quite large brains for their size) and fruit flies.

I will leave you to draw your own conclusion, but since tarantulas have some of the most condensed central nervous systems of any invertebrates, you can safely expect it to have complex neurobiological sleep patterns. Someone just needs to decide to research it!

Tarantulas And Defining Sleep

As mentioned earlier, the tarantula’s nervous system is so different from that of a mammal, we can’t really be certain if their version of sleep is the same as ours.

The first major difference would be their sleep cycle; Ts and other spiders are usually more active at night, whereas most humans go about their day and enter Lalaland at night.

But let’s look at what the experts define sleep as.

The criteria for sleep according to a recent paper on jellyfish and the sleep-like states exhibited are:

• An inactive state with reduced activity.
• Decreased responsiveness to outside stimuli.
• Reversibility of dormant/restful state

The above study did not only cover jellyfish but other inverts such as roundworm and our trusty fruit fly as mentioned above. The fact that so many animals with tiny brains ‘sleep’, shows that sleep evolved in early animals and has remained conserved in most, if not all animals.

And, when we consider how brainy tarantulas are, we can assume that they do indeed hit the hay in some manner of speaking.

Also, the fact that tarantulas have some sort of circadian rhythm (daily activity/inactivity), shows that there is a period of rest involved.

The times when they are inactive are usually characterized by withdrawing to a hiding spot or shelter and a drop in metabolic rate. No, studies have however been done to measure the period of time spent active vs inactive or what different species do during these times.

Interesting fact: Spider species (including tarantulas) that live in the desert, retreat into their burrows during the hottest part of the day. As it gets dark and cooler, the spiders will come out.

Tarantulas And Hibernation

Some of our follicle-enriched spider friends ‘overwinter’, meaning they go into hibernation. This usually happens in colder climates where the tarantula will plug up the openings of their burrows with dirt and webbing and ‘go to sleep’.

They draw their legs into their body, drop their metabolic rate and remain huddled until it warms up outside.

This ability to go dormant for such a long period of time shows that it may be part of their everyday cycle – of course just for shorter intervals. Very little is known about what exactly spiders do during this time, but if you ask me, it can be seen as a form of sleep or rest.

Okay, the most important thing that comes from knowing that your T most likely goes into periods of rest, even though we can’t really call it sleep as we humans define it, is the fact that tarantulas are nocturnal.

So, all the times during the day you’re walking over to say hi to Mr. Grumps, or lifting the lid to see if Sally is doing okay, or digging around to see if Spikey will come out, you’re actually disturbing their rest.

Put yourself in their fuzzy feet; how would you like it to be talked to in a squeaky voice, nudged or worse yet, sprayed with water while you were in dreamland? I didn’t think so!