Unlike humans, who may be right-handed or left-handed, octopuses do not have a dominant arm. But new study shows they tend to rely more on their front arms when carrying out everyday tasks.
Scientists analyzed hundreds of short video clips of wild octopuses crawling, swimming, standing, fetching, and groping to understand how their eight limbs work in the wild.
“All of the arms can do all of this stuff – that’s really amazing,” said Roger Hanlon, co-author of the study and a marine biologist at the Marine Biological Laboratory in Woods Hole, Massachusetts.
Unlike many mammals, octopus limbs are not specialized. However, the study found that three octopus species showed a clear preference for using their four front arms about 60 percent of the time. The rear arms were more often deployed for walking, stilting, and rolling.
“The forward arms do most of the exploring, the rear arms are mostly for walking,” said Mike Vecchione, a zoologist at the Smithsonian National Museum of Natural History who was not involved in the study.
The research, based on video footage collected between 2007 and 2015 in the Atlantic Ocean and the Caribbean Sea, is the first large-scale analysis of octopus limb use in the wild. Unlike lab-based studies, it showed no preference for right or left arms.
Results were published Thursday in the journal Scientific Reports.
“I’m in awe that the researchers managed to do this,” said Janet Voight, an octopus biologist at the Field Museum of Natural History in Chicago, who was not part of the study.
Octopuses are notoriously shy and elusive, spending much of their time hidden in dens. Capturing their behavior on camera required years of patience and persistence.
Each octopus arm is highly complex, equipped with 100 to 200 suckers that serve as sensory organs “equivalent to the human nose, lips, and tongue,” said Hanlon.
And in the wild, where losing arms to predators is common, redundancy comes naturally.
“When you’ve got eight arms and they’re all capable,” Hanlon said, “there’s a lot of redundancy.”