Octopuses Are Reusing Human Trash as Shelter

In crowdsourced images, the cephalopods were observed making refuse their home, even using the junk as a place to lay eggs

An image of a red octopus resting inside of a rusted tin can on the ocean floor
For decades, researchers and divers have observed curious and intelligent octopi utilize oceanic pollution as tools or taking up residence in glass bottles. Katie Lee Osborne via Wikimedia Commons under CC BY SA 4.0

When seashells are sold as souvenirs on the seashore, various kinds of marine life are forced to adapt and use other abundant materials along the ocean floor as shelter—even human garbage.

A new analysis found octopuses use trash, like plastic and glass bottles, as camouflage, shelter and even a place to lay their eggs, reports the Independent's Vishwam Sankaran. The study, published last month in the Marine Pollution Bulletin, analyzed images from social media, marine institutions and diving interest groups that show octopuses interacting human garbage, reports Linda Geddes for the Guardian.

For decades, researchers and divers have observed curious octopuses investigate trash, often using the objects as tools or taking up residence in containers like glass jars or bottles. However, the study illustrates just how widespread the behavior is. Marine biologists gathered 261 underwater images and videos of octopuses using marine waste from posts shared on social media websites and collected by research institutions. In total, 24 different species of octopus were found sheltering in broken glass bottles, soda cans, and even old batteries. According to the Guardian, some buried themselves under a mix of seashells and bottle caps.

"It's becoming so common that they're using these items to protect themselves with instead of their natural shelters, such as seashells, which are becoming scarce in the ocean," study author Maira Proietti, an oceanographer at the Federal University of Rio Grande, tells CBC.

Scientists even observed a coconut octopus (Amphioctopus marginatus) "stilt walking," which occurs when the animal hides their upper body inside a vessel, but pokes their arms out from under the item to creep along the floor and forage for food. Usually, this species "stilt-walks" using shells or coconuts. The coconut octopus was the species most frequently observed interacting with the litter, reports Carly Cassella for Science Alert.

In total, the research team found 40 percent of the interactions occurred with glass objects, while 25 percent were with plastic items, the Independent reports. Scientists suspect this might be because glass more closely mimics the texture and feel of seashells.

While analyzing the data, biologists also found the octopuses' interactions with waste increased the most between 2018 and 2021. However, the boost could be attributed to the increased accessibility of underwater photography, but could also indicate ocean pollution is worsening, Science Alert reports. Footage obtained from remotely operated vehicles found for the first time that deep-sea octopuses in the Mediterranean are using discarded sunken waste, too.

Shockingly, the team found the recently described pygmy octopus (Paroctopus cthulu) has only been observed using marine litter, like beer cans, for shelter. Scientists have yet to observe the tiny sea creature using natural items, like seashells, which could indicate scarcity in their environment, per Science Alert.

While the results are eye-opening, Stefan Linquist, a philosopher of biology at the University of Guelph, tells CBC that the study lacked a control subject. Comparing the octopuses to other sea creatures that may use trash in a similar way would allow the research team to observe how common the behavior is among different species. 

"Ideally, you would want a comparable species that also burrows for shelter. Then we could at least ask the question of whether octopuses rely more or less on litter, based on the images. As it stands, we have no comparative information," Linquist tells CBC via email.

Study author Proietti tells CBC that collecting the crowdsourced images was a complicated process, so a control subject was not studied but could serve as an entry point for a follow-up study.

Despite their adaptability to the growing presence of rubbish in their habitat, using batteries or plastic objects could expose the cephalopods to heavy metals or harmful chemicals, per the Independent.

"This information is fundamental to help prevent and mitigate the impacts of litter on octopuses and identify knowledge gaps that require attention," the study authors write in the paper.