Jumping spiders sleep in two stages, one REM-like, behaviour study finds

An Australian jumping spider passed every behavioural test for sleep that the team set, including a REM-like stage in which it was slower to wake, but nobody has yet recorded what its brain is doing.

Peer reviewed · Behavioural laboratory study · One species, no brain recordings

The jumping spider Portia fimbriata sleeps in two distinct stages, one of them REM-like, according to a study published in PNAS on 26 October 2026. Nadja Geiger, Daniela Rößler and colleagues, led from the University of Bonn, filmed the spiders day and night, tested how easily they woke and disturbed their nights to see whether they made up lost sleep. They did. The university calls it the first comprehensive confirmation of sleep behaviour in a spider. The catch: every result comes from behaviour in one species, with no recordings of brain activity.

Evidence at a glance

Is this a big deal?

A solid step, not a revolution. Sleep scientists have long used a checklist of behaviours to decide whether an animal sleeps, and this is the first spider study to tick the whole list. Whether its twitchy stage is REM sleep in any deeper sense is still open.

What scientists found

Portia fimbriata is an Australian jumping spider that hunts other spiders. Adults are about the size of a one-euro coin. In the lab, the team found it active in daylight, with a daily rhythm that kept running when outside time cues were removed. Biologists call that a free-running circadian rhythm, and it means an internal clock is setting the schedule.

At night the spiders settled into long spells of stillness in a sleep posture. Those spells were broken, at regular intervals, by short REM-like bouts: eye movements, plus twitching of the legs and body. During those bouts the spiders reacted more slowly to a sound, and some did not react at all, Geiger told ABC News.

After a disturbed night, the spiders slept more. The abstract calls these “rebound effects”, and Geiger said the catch-up was particularly strong in the REM-like stage.

How they found it

The question came from Rößler’s own earlier work. In 2022 she led a study of a European jumping spider, Evarcha arcuata, whose spiderlings have see-through bodies for their first days. At night, the team could watch the tube-shaped retinas inside their heads shift in bouts lasting a median of 77 seconds, about every 17 minutes, while the legs curled and twitched. When that study came out, Rößler told the Associated Press the team still had to test whether the spiders were actually asleep.

The new paper runs those tests. Each spider lived in a 12 cm plastic dish under changing light schedules, so its rhythm could be tracked, with infrared cameras recording sleep posture and REM-like phases after dark. To measure arousal threshold, the strength of signal needed to rouse an animal, the team played a sound and timed the reaction. Then they disrupted the spiders’ sleep and watched the following night. Coverage that drew on the full paper says the disturbance came from fruit flies released into the enclosures; SciQuest could not check that detail.

Think of the arousal test as a fire alarm. A person reading on the sofa reacts at once; a person in deep sleep takes longer. The comparison has a limit: a slow reaction alone could also mean a tired or cold animal, which is why the rhythm and rebound tests matter alongside it.

Why it matters to you

This won’t change how you sleep. It speaks to a bigger question: how old sleep is, and why almost every animal studied seems to need it. If an animal whose ancestors split from ours so long ago shows a REM-like stage, either the stage evolved more than once or its roots run very deep. Either answer would help explain what that stage is for.

What the evidence does not show

It does not show that spiders dream. It also does not show what the spider brain does during the REM-like bouts; the release states that brain activity was not measured. The authors call their conclusion “behavioral sleep” and the REM-like stage a “substate”, which is careful wording.

The abstract and release give no sample sizes. Write-ups based on the full paper describe groups of about 10 animals for the night recordings and 13 for the disruption test, with 5 undisturbed controls. SciQuest has not been able to check those numbers, and they are small. All of the work was done in the lab, on one species.

How this fits what we already knew

Catch-up sleep itself is not new in invertebrates. In 2000, Paul Shaw and colleagues showed that resting fruit flies are harder to rouse and make up for lost rest. Two-stage sleep is not new either: in 2023, a team led by Sam Reiter recorded brain activity in sleeping Octopus laqueus, a marine invertebrate, and found an active stage roughly once an hour, lasting about a minute. What the spider adds, in the authors’ words, is evidence “for an REM-like sleep substate in a terrestrial invertebrate”. For more on octopus brains, see how octopus DNA folds around brain genes.

Independent perspective

Thomas White, an entomologist at the University of Sydney who was not involved, told ABC News the paper is the most complete behavioural case for sleep in any arachnid. When the 2022 study appeared, UCLA sleep researcher Jerry Siegel told the AP he doubted that such quiet-state activity is REM sleep. The new paper addresses whether spiders sleep, not that deeper objection. Barrett Klein, an entomologist quoted in 2022 as an outside voice, is a co-author this time.

How other headlines framed it

• ABC News Australia led with video of the REM-like sleep and added the only independent comment SciQuest found.
• ScienceAlert headlined the first sleep rebound in an invertebrate. Rebound in fruit flies dates to 2000; the new claim, as the authors told ScienceAlert, is REM rebound.
• The Brighter Side of News (syndicated on Yahoo) asked whether spiders dream, and stressed that no brain activity was recorded.
• StudyFinds focused on spiders catching up on sleep after a rough night.

Several outlets report that REM-like time rose by nearly 80% after the disturbed night. SciQuest leaves that figure out of its own findings until it can be checked in the paper.

What happens next

The Bonn group plans to compare sleep across spider species, between the wild and the lab, and against measures of cognition. It also plans to study how artificial light at night and climate change affect sleep, and to work toward recording brain activity in arachnids and insects. Brain recordings are also the test that could answer Siegel’s objection.

In one sentence

A jumping spider that is active by day, is slower to wake during twitchy REM-like bouts at night and catches up after a bad night is behaving like a sleeper, though only brain recordings can show how close that stage is to REM sleep in mammals and birds.

Read next

• Octopus and squid DNA forms flexible loops linked to brain development: another invertebrate with a complex brain.
• How many hearts does the octopus have? The body plan of the other invertebrate with two-stage sleep.
• What would aliens look like? How evolution can arrive at similar solutions more than once.

Sources and disclosure

1. Geiger N, Capelle MQ, Rosentreter P, Herberstein ME, Bahl A, De Agrò M, Klein BA, Rößler DC. “Behavioral evidence for two-stage sleep in spiders.” Proceedings of the National Academy of Sciences 123(45): e2618030123, published online 26 October 2026. doi:10.1073/pnas.2618030123 (abstract read via Crossref and PubMed; full text not accessible to SciQuest).
2. University of Bonn, “How deeply do spiders sleep?”, news release via EurekAlert, 26 October 2026.
3. Rößler DC, Kim K, De Agrò M, Jordan A, Galizia CG, Shamble PS. “Regularly occurring bouts of retinal movements suggest an REM sleep–like state in jumping spiders.” PNAS 119(33): e2204754119 (2022). doi:10.1073/pnas.2204754119 (full text via PMC).
4. Shaw PJ, Cirelli C, Greenspan RJ, Tononi G. “Correlates of sleep and waking in Drosophila melanogaster.” Science 287: 1834–1837 (2000). doi:10.1126/science.287.5459.1834.
5. Pophale A et al. “Wake-like skin patterning and neural activity during octopus sleep.” Nature 619: 129–134 (2023). doi:10.1038/s41586-023-06203-4.
6. Burakoff M. “Do spiders sleep? Study suggests they may snooze like humans.” Associated Press, 8 August 2022, via WSLS.
7. Bowler J. “Scientists video REM-like sleep in Australian jumping spider species.” ABC News, 27 October 2026.

Disclosure: This article was drafted with AI assistance and checked against the sources above. SciQuest could open only the paper’s abstract, so numbers from the full paper are attributed to the outlets that reported them. The graphic is a SciQuest original built from the 2022 and 2026 papers; it compares which sleep tests each study reported. Spotted an error? See our corrections policy.