Octopuses are using human garbage as shelter, camouflage and more, study finds

Story Transcript

A new study suggests it's becoming increasingly common for octopuses to use bottles, cans and other human trash to shelter themselves, camouflage their dens and even house their young.

"We believe this is because of the high abundance of these artificial items — you know, the litter item — in the ocean," senior author Maira Proietti, an oceanographer from the Federal University of Rio Grande in Brazil, told As It Happens guest host Gillian Findlay.

"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."

The findings are not surprising. Marine scientists and other people who work on the ocean have long observed octopuses taking up residence in sunken bottles and containers. In fact, those who study the creatures often use such objects to lure and capture them.

But the new study, published in last month's Marine Pollution Bulletin, is the first to use crowdsourced photography to examine just how widespread the behaviour is. 

Hundreds of crowdsourced photographs

The researchers — from the Federal Universities of Rio Grande, Santa Catarina and Pernambuco in Brazil and the University of Napoli in Italy — examined 261 photographs of 24 different species of octopuses interacting with ocean trash from around the world. 

"Through these images, we observed that it's very common for these benthic [deep-sea] octopuses to use artificial shelters instead of natural ones," Proietti said.

Glass objects were present in 41.6 per cent of the photos, while plastic was observed in 24.7 per cent. 

Earlier this month, the UN approved a landmark agreement to create the world's first ever global plastic pollution treaty calling plastic in the world's oceans "an epidemic."

Some photos showed octopuses using the trash as makeshift shelters, or even using bits of garbage to camouflage their natural dens. Others showed females using litter to house their eggs.

Others, still, showed the creatures "stilt-walking" — using their tentacles to walk along the seabed — while clutching onto the various items they've collected. 

"At first glance, it would seem like a positive thing because since they don't have the natural shelters, at least they have some artificial ones to avoid predation and protect themselves," Proietti. "But this could also be concerning."

At least one octopus was pictured sheltering in a broken glass bottle, she said, which could lead to injury. In another case, an octopus was sheltering in an old car battery, which she says could emit chemicals that are dangerous to marine life.

Concerns about methodology

Stefan Linquist, a University of Guelph philosopher and naturalist who has been studying the social behaviour of octopuses, says the findings are not surprising, and present an interesting case study for using crowdsourced photography in marine studies.

While studying octopuses in New South Wales, he says he observed octopuses using discarded scallop shells to build shelters. Those creatures also appeared to have gathered around a large block of concrete on the ocean floor to use as additional shelter.

That said, Linquist says he has concerns about the study's methodology. For one, he says it lacks control subject — another animal to compare the octopuses to. 

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

Proietti says they were not able to study a second species, as crowdsourcing the octopus photos alone was already an "extremely laborious" process, but that it would a good idea for followup research.  

What's more, Linquist says what appears to be an increase in the critters using litter could actually just an increase in the availability of photographic evidence. Underwater photography has become more popular and accessible in recent years, he said.

Proietti admits this is a possibility, and the study includes this caveat as well.

Despite these limitations, Proietti says what they did observe was troubling.

"Unfortunately, we are living a huge environmental crisis … not only climate change, but also this litter pollution in the ocean is extremely worrisome," Proietti said.

"We need to stop the sources and collect what's in the ocean as soon as possible because the impacts will only increase as well."

Written by Sheena Goodyear. Interview with Maira Proietti produced by Katie Geleff.