Watching what octopus do all day and night.

Story & Photos By C.E. O’Brien, Ph.D., Associate Professor of Tropical Marine Ecology, School for Field Studies Center for Marine Resource Studies South Caicos

How does an octopus spend its time at home? That’s what I and two researchers from Brazil teamed up to determine in a recent study titled “Octospy; What Octopus insularis do in their dens.” Turns out, these octopuses are pretty lazy, and not nocturnal as previously believed. They also get harassed by their fishy neighbors quite a bit. But more on that later.

Tucked into a coral crevice is a highly intelligent, but somewhat lazy Octopus insularis near South Caicos.

The species we investigated, Octopus insularis (O. insularis for short), inhabits the tropical waters of the western Atlantic, including Brazil, the Gulf of Mexico, and the West Indies. It lives for about a year, dwells mostly in shallow water and eats a variety of crustaceans (crabs, lobster and shrimp), bivalves (clams, mussels, scallops and oysters), gastropods (snails and limpets), and other invertebrates. It makes a temporary home out of conch shells, crevices in coral, or holes in the bedrock, sleeping and eating inside to minimize the risk from its own predators (sharks, eels, rays, large fish), spending days to months returning to a single den before moving on to a new one. Like other octopuses, it is highly intelligent and capable of changing its appearance—color, texture, shape, reflectance—from moment to moment, making it difficult to observe in the wild.

Luckily for me, living and working at the School for Field Studies’ Center for Marine Resource Studies (CMRS) on South Caicos, I have easy access to these enigmatic octopuses. In 2020, I decided to set up timelapse cameras outside O. insularis dens. These cameras were programmed to take a photograph every 20 seconds and using these I was successful in documenting “a day in the life” of six individual octopuses for two or three days each. There were some problems with this technique however, as short battery life meant that cameras had to be changed 4–5 times throughout the day, and with 20 seconds between photographs, many behaviors were missed. It was also not possible to film during the night, leaving it an open question as to whether the species was at all nocturnal, or only active during the day (diurnal). Finally, remember I mentioned that they’re smart? Several of the individuals figured out how to open the waterproof camera housings and tear the cameras apart!

This inspired me to build a more durable, longer- lasting recording device that would be capable of filming at night. Based on the design of Dr. Chelsea Bennice, another octopus researcher working at Florida Atlantic University, I constructed two “Octopus Monitoring Devices” or “OMGs.” Each of these consisted of a 10-inch section of PVC pipe with a removable rubber cap on one end and an acrylic window on the other end. Inside, a battery pack powered a GoPro camera and a red LED light for up to 21 hours at a stretch, while dive weights and rocks were used to keep it anchored to the seafloor. With these OMGs, I managed to record the 24 hour activity cycle of 10 individual octopuses during 2021.

This series of images caught on camera show an octopus “punching” a passing wrasse.

Once these photographs and videos were collected, they needed to be analyzed. I reached out to two Brazilian scientists who have worked extensively with this species: Dr. Tatiana Leite, the scientist who “discovered” and named the species in 2008, and Dr. Sylvia Lima de Souza Medeiros, an expert in O. insularis sleep. Under Dr. Leite’s supervision, Dr. Medeiros and I went through all of the photographs and videos separately, and categorized behavior according to a set list of descriptions (away from den, alert, active, eating, and sleeping) based on our judgment. We then compared our interpretations, and any disagreements that could not be rectified through careful re-analysis were classified as “unknown.” We then used these data to determine how much time each behavior was performed and if there was any pattern as to when they sleep or leave the den to hunt. 

We found that O. insularis spend most of their time (61%) sleeping or resting, and only 15% hunting, 8% eating, 9% alert, and 6% moving around inside the den. (Less than 1% of the time could not be categorized.) This coincides with the findings of previous work in Bermuda, which showed the species to be “lazy,” spending as little time as possible outside the den where it can be attacked by predators, only long enough to obtain sufficient prey for itself.

Interestingly, the time that each individual slept or left the den was highly consistent between the two or three days it was observed, while it varied widely between individuals. This suggests that, like people, octopuses are highly individualized in the amount of sleep they require and the time they need to accomplish certain tasks (hunting, in this case). 

Plotting the number of individuals sleeping or away from the den by hour revealed a loose “schedule” of sorts for the species, although here too there was a great deal of variation. O. insularis tended to sleep for long periods during the night, and take at least one “nap” during the day. There were up to 9 bouts of sleep per day, lasting seconds up to 14 hours. They typically left the den 2–3 times a day for seconds up to 12 hours. Octopuses left the den more often in the morning (6–10 AM) and evening (4–8 PM), and never at night. This shows that the species is diurnal, not nocturnal like many other octopuses. 

Some interesting moments were caught on camera. When they are consuming prey, octopuses are often harassed by scavenging fish, particularly wrasses, that try to nab bits of its meal or even the octopus itself. On several occasions, octopuses lashed out and “punched” one of their “ha-wrasse-rs,” which seemed a fairly effective deterrent. Punching has been seen in other species of octopus, which are often followed by an “entourage” of several fishes as they hunt for prey.

This Octopus is holding a shell as a shield against harm!

On two occasions, both at night, octopuses were attacked by hungry spotted moray eels. But these eels seem to have really bad aim, since on both occasions their strikes missed the octopus and left the eel with a mouthful of rock instead. These octopuses were lucky, though: many octopuses of this species and others living in the Turks & Caicos can be seen missing parts of their arms or with arms growing back due to attacks by these morays. 

Another interesting phenomenon our camera documented was rapid color changes and movements during sleep. After dozens of minutes sitting quietly with pupils narrowed and breathing slowed, octopuses would twitch, change colors, and open their pupils wide for several seconds before narrowing them again. One particularly striking color change consisted of turning light on one side and dark on the other for several seconds, and then reversing the pattern.

These phenomena were first documented in this species by Dr. Medeiros during laboratory trials. The photos and videos taken in this study demonstrate that these behaviors aren’t restricted to, or somehow caused by, captivity. And if it sounds to you like the octopuses are dreaming, you’re not alone in your thinking. Unfortunately, there is currently no way to scientifically evaluate the inner experience of an octopus to definitively determine if it is having a “dream,” so whether that is what is actually what is going on will stay a mystery for now.

While the remote cameras utilized in this study are among the least invasive ways to observe wildlife, the octopuses were definitely aware of them. Almost every octopus touched the camera or OMG with the suckers on their arms at some point during the observation periods. Octopus suckers are amazingly versatile: not only can they feel the way our hands do, but they can taste as well, in addition to being able to grasp objects with great force. Octopuses use their suckers to grope around on the sea floor in search of prey, so they were likely trying to figure out if these strange objects were food or some type of threat.

Our study is the first to document the 24 hour activity cycle of this species in its natural habitat. Our findings give ecological insight into this important species, such as the fact that is diurnal, not nocturnal, which will help scientists better plan future observations and experiments. Our study also shows that remote cameras are a great way to study marine animals. With them, a great deal of information can be collected with minimal stress to the animal. Our work is published open access (free to everyone) in the journal Marine Ecology  [https://onlinelibrary.wiley.com/doi/full/10.1111/maec.12763].