Spiders adjust sleep after disrupted rest

A study published in October 2026 in PNAS found that jumping spiders of the species Portia fimbriata extend their sleep by 8.5% after a short or disrupted night. This behavior, similar to how some mammals recover lost sleep, was challenging to observe in such small animals.

Experiment involved disturbed and undisturbed spiders

The study used 92 spiders, with 17 of them exposed to 25 live flies for several hours to disrupt their rest. The following night, these spiders increased their rest time by about 8.5%, while their periods of agitation rose by nearly 65%. A control group of five spiders that remained undisturbed for three nights showed no such response, linking the extra rest to accumulated fatigue.

Spider sleep includes physical signs

Spider sleep is marked by brief leg and eye tremors, similar to the paradoxical sleep seen in humans. An asleep spider can be identified by a specific posture—hanging upside down from a silk thread, motionless and hard to wake.

Spiders may experience a state like dreaming

This is not the first time these spiders have surprised researchers. In 2022, the same team observed nocturnal eye movements in a European relative, suggesting a state similar to dreaming. The new study adds evidence that these small predators actively recover from lost rest, much like some mammals do.