Recent observations made at The Rockefeller University in New York show an octopus potentially experiencing a nightmare. Costello, an Octopus insularis, was filmed several times by postdoctoral researcher Eric Angel Ramos sleeping peacefully and then suddenly thrashing its tentacles, reports Live Science, indicating a sleep disturbance.

Octopi-ing The Thoughts

Scientists spent four weeks filming Costello in a laboratory and observed him jolting out of sleep and flailing around on four separate occasions. The footage suggests the cephalopod was experiencing a sleep disorder. The data was posted on bioRxiv but has not been peer reviewed.

The behavior was unusual; however, Costello may not have been experiencing a nightmare. Ramos pointed out that despite all the studies that have been performed on octopuses and cephalopods “there’s still so much we don’t know.”

In two of the four thrashing instances, Costello released black ink into the tank, which octopuses commonly do in the wild for defensive purposes when squared off with a predator.

“It was really bizarre, because it looked like he was in pain; it looked like he might have been suffering, for a moment,” Ramos explained. “And then he just got up like nothing had happened, and he resumed his day as normal.”

The researchers believe Costello “may have been responding to a negative episodic memory or exhibiting a form of parasomnia,” a.k.a., a sleep disorder. They noted that, “While nothing can be concluded rigorously from such data, we share the data and our analysis with the community, in the hope that others will be on the lookout for such rare events.”

Potential Explanations

Like vertebrates, cephalopods exhibit active and inactive sleep states. In active sleep states, octopuses display camouflage patterns and “modulation of basal rhythms, while remaining relatively unresponsive to outside stimuli.” Some believe these states are comparable to what mammals experience when dreaming.

A 2021 study published in iScience examined the active and quiet sleep patterns of octopuses, which is like humans’ REM and non-REM sleep. Humans experience most of their dreams during REM.

Still, Costello’s behavior was not necessarily a nightmare.

Robyn Crook, a comparative neurobiologist from San Francisco State University who was not involved in The Rockefeller University observations, told Live Science there is simply not enough research about cephalopod sleeping behavior to come to a definitive conclusion. Plus, if octopuses do dream, it may be very different from the way humans dream.

While Costello’s actions are “very interesting,” Crook cautioned that it could have been a result of something else, such as an external stimulus. He may have been startled by something, or he could be in the senescence stage, which occurs right before death when an octopus’s body begins to fail.

Crook and her colleagues have studied senescence in the giant Pacific octopus (Enteroctopus dofleini) and found a link between the condition and nervous system degradation. As a result, Costello’s behavior may be attributed to a lack of motor control instead of a defense mechanism.

It should be noted that Costello, whose life span is 12 to 18 months, died following these observations. Ramos also noted that senescence could be “one of the drivers” of his behavior. He also pointed out that many octopuses in a laboratory are euthanized before senescence occurs, and most labs do not constantly film the animals, so behavior similar to what Costello exhibited may simply not have been noticed.

By Noelle Talmon, contributor for


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