For many people, spiders are the stuff of nightmares, but do spiders actually have nightmares (or any type of dreams) themselves? That is what researchers wanted to know when they set out on a 2022 study.

The team already knew that spiders have a state that is either sleep or something very similar to it. When they go into this restful period, they stop moving for longer periods of time and seem to shut down, not unlike what humans do.

Each spider is unique in how this happens and when, but it seems to occur across all the species.

For the study, the team looked at European jumping spiders (Evarcha arcuata). This species is known to rest at night. When it is time for ‘sleep’, the spider will usually drop itself down from a thread of silk and hang in the air. It will tuck its limbs in near its body and remain restful.

Dr. Daniela Robler of the Max Planck Institute of Animal Behavior is the author of the study.

She talked about the study, saying:

“A usual night starts with the spider finding a good spot to drop down from. They will build little silk anchors in a zig-zag fashion, and then drop down attached by a silk thread which they hold with one of the back legs. They often first start cleaning themselves (brushing their legs against each other, cleaning their eyes etc.), sometimes they even have a little snack while suspended. Eventually, they become motionless.

Then, in quite regular intervals we can observe what looks like active phases but with uncoordinated movements, these can be either periods with noticeable twitches of the abdomen, spinnerets or single legs, or more extreme with some or all legs curled up resembling a dead spider.”

These motions are very similar to the movements that humans experience while dreaming. Since this spider has a translucent exoskeleton while juveniles, it was possible to look more closely at what was happening with the spider.

Spiders have retinal tubes that move when changing what they are looking at. These tubes were moving at regular intervals in a way that was very similar to what happens to humans (as well as many other animals) during REM sleep.

This is not conclusive evidence that the spider is dreaming, but it does help to create a compelling argument. Robler, for one, is convinced:

“Personally, after watching hundreds of spiders, there is no doubt in my mind that they experience dreams, just like no one would doubt that when watching a cat or a dog dream. Whether we will be able to scientifically prove that this is the case… we will have to see.”

If it can be proven that spiders dream, it would show that creatures that are much less complex than previously known engage in this activity.

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