An octopus raises its arm in the wild. Credit: Chelsea Bennice, Florida Atlantic University
Octopuses are well known for their incredible intelligence and dexterity. A new study is the first of its kind to connect the animals’ arm movements to broader behaviours when navigating their natural habitats in shallow ocean waters.
The researchers hope their findings will help inform the development of soft robotics which can mimic the flexible nature of octopus arms.
“Observing them in the wild, we saw octopuses use different combinations of arm actions,” says Chelsea Bennice, lead author of the study and research fellow at Florida Atlantic University in the US.
“Sometimes just one arm for tasks like grabbing food, and other times multiple arms working together for behaviours like crawling or launching a parachute attack – a hunting technique they use to catch prey.”
The researchers recorded 25 videos of 3 wild species across shallow-water habitats throughout the Atlantic, Caribbean and in Spain.
They identified 12 distinct arm actions after observing about 4,000 arm movements. Each involved one or more of 4 fundamental arm deformations, where the arm shortened, elongated, bended or twisted.
While every octopus arm can perform all the different actions, the researchers detected a clear pattern. An octopus will use its back arms mainly to transport itself around, and its front arms to explore its surroundings.
The front 4 arms were used 64% of the time, while the back 4 were used in the remaining 36% of actions.
“These versatile abilities allow octopuses to thrive in a wide range of habitats,” says Bennice.
“Beyond foraging and locomotion, their arm strength and flexibility are essential for building dens, fending off predators, and competing with rival males during mating.”
A common octopus in South Florida waters. Credit: Chelsea Bennice, Florida Atlantic University
The authors say that these results show that octopuses use specific limbs to carry out specific tasks, a behaviour previously seen frequently in only primates, rodents and fish.
While previous studies have attempted to examine the strength or flexibility of octopus arms, most have been limited to studying the arm in a lab environment.
“I’m a strong believer that you have to get into the natural world, and especially the sensory world, of whatever animal you study,” said Roger Hanlon, a co-author of the study from the University of Chicago’s Marine Biological Laboratory in the US.
“The fieldwork is very arduous, and it takes a lot of luck to get valid natural behaviours.”
The researchers hope that the implications of this study will stretch far beyond the sea floor, suggesting their results could be used to improve how robotic arms operate.
For Hanlon, an octopus-like robotic arm could prove critical in moments where buildings or submersibles collapse and a rescue team needs to deliver important resources.
“How do you deliver a drug or a phone or water to someone who’s down there?” says Halon.
“You need some snaky little arm with high flexibility that can not only get down there but can do something useful when it arrives.”
“Understanding these natural behaviours not only deepens our knowledge of octopus biology but also opens exciting new avenues in fields like neuroscience, animal behaviour and even soft robotics inspired by these remarkable creatures,” adds Bennice.
The research has been published in the journal Nature Scientific Reports.