The hunting skills of octopuses are being used to develop next-gen robots. A study has shown that the sea predators use certain tactics depending on the prey they are stalking. Researchers at the University of Minnesota watched a California two-spot octopus as it tackled crabs and shrimp. Among several observations, they found that octopus pounced on crabs with a cat-like movement, while when hunting shrimp they were more careful to avoid spooking the prey. “Normally when you look at an octopus for a short while, nothing is repeatable. They squirm around, and just look weird in their exploratory movements,” said Trevor Wardill, an assistant professor at the university's College of Biological Sciences (CBS), who studies octopuses and other cephalopods. The new study, published in Current Biology this week, aims to offer a better understanding of how octopuses use their arms to aid efforts to develop next-generation, highly manipulative soft robots. Underwater vehicles inspired by octopuses could play a crucial role in deep ocean exploration. Funding and support for this work has been provided by the U.S. Office of Naval Research, a U.S. Navy department tasked to maintain "future naval power and preserve national security". Wardill and colleagues investigated whether octopuses preferred certain arms over others when hunting, rather than using each arm equally. They placed different types of prey, including crabs and shrimp, into tanks where an octopus lurked in an ornamental SpongeBob den. By videoing the results, they realised that the octopus would have one eye facing outward, alerting it to when to time a lunge for their victim. Because crabs move slowly while shrimp can flick their tails to escape quickly, each type of prey potentially requires different hunting tactics. The researchers made a number of observations regarding the octopus hunting tactics: - Octopuses used arms on the same side as the eye viewing the prey. - No matter what type of prey came by, each octopus attacked using the second arm from the middle. - When hunting crabs, octopuses pounced on the prey with a cat-like movement, leading with the second arm. - When hunting shrimp, the octopuses were more careful to avoid spooking the prey. They led with the second arm and after it made contact with the shrimp, they used neighbouring arms one and three to secure it. Flavie Bidel, lead author and a postdoctoral researcher in the lab, noted how predictably octopuses began prey capture with the second arm. The work demonstrates how, for creatures whose movement appears unpredictable, the hunting behaviour was actually notably repeatable. One of the next steps is to study how neurons facilitate the arm movements. Trevor Wardill concludes: “Octopuses are extremely strong. For them, to grasp and open a door is trivial, given their dexterity. "If we can learn from octopuses, then we can apply that to making an underwater vehicle or soft robot application." Underwater vehicles inspired by octopuses could play a crucial role in deep ocean exploration. The Wardill lab is based in the Ecology, Evolution and Behavior Department in CBS.