Do Spiders Dream? These Arachnids Twitch, Curl Their Legs and Move Their Eyes When Asleep, Hinting at a Complex Brain State

A species of jumping spider appears to enter a deep sleep phase that resembles rapid eye movement (REM) in humans, the stage in which we typically dream

Sara Hashemi | Daily Correspondent

November 2, 2026 3:44 p.m.

Even jumping spiders need some shuteye. By filming one species’ nighttime routine—and attempting to disrupt it—researchers have identified that it enters two different sleep stages, including one resembling the phase linked to dreaming in humans.

The work, published on October 26 in the Proceedings of the National Academy of Sciences, marks the first comprehensive confirmation of sleep behavior in spiders. The findings can help scientists unravel how snoozing evolved in animals.

“The fact that they sleep is a really strong push toward the idea that these animals are experiencing a much more complex sensory world that persists beyond just immediate sensation,” says Alex Winsor, a neuroethologist at Columbia University who wasn’t involved in the study, to Julia Vaz at Science.

Study co-author Daniela Rössler, an ecologist at the University of Bonn in Germany, first encountered this spider behavior in 2020. Pandemic restrictions kept her away from her lab, so she caught local jumping spiders of the species Evarcha arcuata and kept them in transparent boxes by her windowsill, Betsy Mason reported for Scientific American in 2022. One day, she noticed something strange—the spiders were all hanging motionless from silk lines hanging from the lids of their boxes.

That discovery led to a paper published in 2022 that suggested E. arcuata entered a stage akin to rapid-eye movement (REM) sleep. In humans, the brain becomes more active during this stage compared with other sleep phases, and we often dream. However, Rössler and colleagues hadn’t proven that the spiders were, in fact, snoozing.

To answer that question, the researchers recorded another species of jumping spider, called Portia fimbriata, with infrared cameras. Continuous recordings revealed that the spiders acted differently during the daytime compared with nighttime. When the sun was up, the arachnids were often stationary but actively monitored their surroundings. They turned, scanned their environment and changed their posture in response to visual stimuli.

But when the sun started to set, their behavior changed. They started to look for a place to rest—usually a silk platform they hang upside-down from—and spent time grooming themselves. Eventually, they dozed off, drooping over the course of the night. This phase, which the researchers call quiescence, was interspersed with short bouts marked by twitching, leg curling and rapid eye movement—signs of REM-like sleep.

“By showing that Portia meets every criterion and even cycles through two distinct sleep stages, we can now confidently say that spiders do sleep, and that their sleep is structured and regulated,” Rössler and study co-author Nadja Geiger, a behavioral ecologist at the University of Bonn, tell Rachael Funnell at IFLScience.

The researchers also attempted to wake up the spiders, since “a hallmark sign of sleep is … [responding] slower or not at all to external stimuli,” Geiger explains to the Australian Broadcasting Corporation’s Jacinta Bowler.

They played a loud noise while the spiders were awake, in the quiescent stage and in the REM-like stage. Awake spiders took an average of 1.69 seconds to react to the sound. In the quiescent stage, however, they took around 2.71 seconds, on average, and during the REM-like phase, they took 4.27 seconds, on average.

The findings can help scientists understand the evolutionary origins of sleep. For instance, the lineage that eventually led to spiders and the one that gave rise to vertebrates, like mammals, diverged from each other around 500 million years ago.

“If animals with such different brains and sensory worlds show structured sleep with REM‑like phases, it suggests that the basic architecture of sleep may be far older and more widespread than we thought,” Rössler tells the ABC.

Showing that spiders are capable of sleep also suggests that the animals have more sophisticated brains than many of us give them credit for. We tend to think of spiders and other invertebrates as less complex, Winsor tells Science, but the new findings challenge that notion. Whether spiders dream during their REM-like state remains an open question that will be difficult to answer, per the outlet, as scientists still have limited understanding of human dreaming.

Next, the team will look at how sleep has evolved among different spider species, according to a statement. They are also comparing how spiders snooze in the wild and in laboratory settings to identify how different conditions might influence their sleep behavior.

“This allows us to ask how natural conditions and anthropogenic changes, such as artificial light and habitat disturbance, influence sleep outside the laboratory,” Rössler tells the ABC.

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• Animals
• arachnids
• Brain
• Evolution
• Sleep
• spiders
• Wildlife