Do spiders dream?

Spiders, dream or nightmare? - 26th September 2022

A new study suggests that spiders sleep and dream like humans. Dr Rossler, an ecologist from the University of Konstanz, studies a particular species of arachnid called the jumping spider. She discovered signs that spiders have a Rapid Eye Movement (REM) sleep cycle indicating they might dream.

After observing young jumping spiders sleeping, Dr Rossler found that their retina would move for 77 seconds every 20 minutes. The animals’ legs and abdomens also twitched much like a dog during an afternoon nap. These are strong indicators of REM sleep.

Scientists aren’t completely sure why animals like dogs, monkeys or even humans practice REM sleep, but one theory is that it helps them hone skills and difficult manoeuvres. The young arachnids in the study might be training their muscle memory for a future hunt. For humans, some scientists believe REM assists us in dealing with stress.

Arachnophobes may have nightmares about spiders, but Dr Rossler thinks spiders suffer from bad dreams too. While dangling peacefully asleep, the spiders will suddenly wake up and make “all [their] legs get extended at the same time, like aah!” says Dr Rossler.

Scientists still have yet to prove whether spiders really sleep, let alone dream. Although it seems like simple resting, sleep actually varies a lot in the animal kingdom. Some animals like frogs hibernate for weeks or months, while some types of aquatic mammals and birds only sleep with half of their brains at a time.

Spiders are too small for scientists to examine with brain scanners, so we may never know for sure whether they really dream. If they do, scientists think humans could empathise more with arachnids and potentially not be so frightened of them. “If they dream, I mean, what can you do? You cannot smush a spider that dreams,” added Dr Rossler.