I got a really interesting question a few weeks ago on my tarantula blog – do spiders sleep?

I actually did not know the answer! In fact, does anyone know?! I had to find out and do some research.

Now, I will say that in my time with Spidey, I have seen her do some crazy stuff that LOOKS like she is sleeping. One of these things is staying perfectly still in a restful, relaxed position for HOURS (sometimes days, let’s be honest). It certainly LOOKS like she could be a sleeping spider, dreaming about tasty crickets and digging around in her substrate. And I’ve even seen her fill her water dish or teacup with dirt to make a sort of “bed” (or throne) for herself so she could lay in it for a long time. But does that mean that spiders sleep? Let’s see what the research says.

According to The Tarantula Keeper’s Guide, this answer isn’t really known and because their nervous systems are so different from ours, it’s uncertain if their sleep would be like our version of sleep:

“We might be able to answer this if we knew what sleep really was.”

However, anyone with a tarantula who is a “pet rock” can attest that these animals do go through long periods of rest and seem to suddenly jump awake when startled, as if they had been sleeping.

This was a great explanation of the “startle”, by rustym3talh3ad on Arachnoboards:

i dont know if u guys have ever really experienced this, but even some of the more quick to bolt or not so friendly T’s that ive encountered can be “Startled” if u catch them at the right moment, u move them with a pencil or pair of tongs and nothing happens, give them a slight nudge and they more or less sit there, do it again and its an explosion of panic…running every which way until they gain some sort of idea whats going on and then they react. perhaps its not sleep but i know im certain ive even caught my OBT off guard…got right on top of her, and even moved her around a bit and then BANG she came off like a bat outta hell but it wasnt her normal reaction, it was more like a “WTF is going on….im going to bite things” so…i would have to go with there IS a rest period for them, but at what level we can compare it to sleep im uncertain…i dont have the scientific background to know that.

It would be hard to tell if spiders sleep – because first of all, they don’t have eyelids to close their eyes! And secondly, many tarantulas and spiders tend to be more active at night by nature, so their sleep cycle likely wouldn’t look anything close to ours! It a really complicated question and one that we must do more research into. Here’s a great example about just how involved tarantula/spider “sleep” could get:

It really depends on how you define ‘sleep’. All animals have some sort of ‘circadian’ rhythm – a daily activity/inactivity pattern. Some are active during the day – diurnal – others are active at night time – nocturnal/crepuscular. The periods of inactivity are characterized by withdrawal (to a shelter perhaps) and a drop in metabolic rate.

This applies to spiders as well, although no studies have been done to measure the period of time spent in such a state or at what times different species do it. It seems that spiders with good eyesight that rely on vision to capture prey may tend to be more active in daylight hours, whereas others that rely on snares/webs could be active at other times, but this is not necessarily the case for all species.

In cold climates, spiders ‘overwinter’, which means that they have a kind of hibernation period. Overwintering involves a drop in metabolic rate, where the spiders bring their legs into their body and remain huddled in a shelter during the coldest months of the year.

This ability to shut down for a long period of time indicates that they might be able to do it for shorter periods in their everyday cycle, which could be seen as a form of sleep or rest.

Wikipedia noted this:

The electrophysiological study of sleep in small invertebrates is complicated. However, even such simple animals as fruit flies appear to sleep, and systematic disturbance of that state leads to cognitive disabilities..Flies deprived of sleep require a longer time to learn and also forget more quickly. If an arthropod is experimentally kept awake longer than it is used to, then its coming rest period will be prolonged. In cockroaches that rest period is characterized by the antennae being folded down and by a decreased sensitivity to external stimuli. Sleep has been described in crayfish, too, characterized by passivity and increased thresholds for sensory stimuli as well as changes in the EEG pattern, markedly differing from the patterns found in crayfish when they are awake.

On Reddit, user 006fix said this:

They certainly have behaviour that mimics sleep (loss of muscle tension, no movement for duration, delayed response to stimuli compared to normal, and with somewhat more ‘jump’ than might be expected for that level of stimuli). The easiest way to see when this happens to your tarantula is if they fall asleep on the side of their enclosure, horizontal to the ground. Their abdomen slumps down with gravity noticeably if they sleep like this.

As to the why they sleep – sleep is universal to almost all organisms. Various organisms use variants on sleep to preserve constant attention (such as dolphin uni-hemispheric sleep), but they basically all do it. Studies in lizards recent have revealed very ancient roots to the human style REM, slow wave and fast wave sleep cycles, and even v.simple invertebrates like fruit flies will suffer cognitive declines if deprived of sleep. Spiders have some of the most concentrated CNS’s of any invertebrates, so will almost certainly exhibit complex neurobiological sleep patterns if anyone cares to study them. I doubt they dream though.

Do spiders sleep? As of right now, we really don’t know. There is so much we have yet to learn about the bodies of arthropods in general, and spiders remain a mystery to us. But I hope that this post gave you some food for thought!

By the way, I am in the middle of creating a monthly tarantula magazine – if you’d like to be a part of that, you can visit the magazine’s Patreon page to subscribe or make a submission! You can also contact me at theavenmag@gmail.com for more info!

If you want to learn more about tarantulas, feel free to check out my big tarantula guide (I talk about lots of tarantula facts and enclosure/care tips). You can also get free tarantula tips by signing up for my newsletter or subscribing to my YouTube channel! I release new tips every Tuesday for Tarantula Tuesday! And I also sell some pretty cool tarantula t-shirts, if I do say so myself 😉