No wonder, with so many arms, octopuses make great pitchers. They can even target other octopuses with pieces of debris from the sea floor – and score a direct hit.
For the first time, researchers observed the famous stroke cephalopods hurling clumps of sand, bits of seaweed, and even shells at each other, though they don’t actually fly with their hands like humans do. Instead, they use their arms to gather projectiles and then propel them using jets of water shot from a siphon under their arms. Scientists recorded videos of this unusual behavior in gloomy octopuses (Octopus tetricus) in Jervis Bay on the south coast of New South Wales in Australia and described their findings Nov. 9 in the journal PLoS One (opens in new tab).
“In some cases the projected material hits another octopus or another object (fish or camera),” the scientists wrote in the study.
After reviewing 24 hours of footage recorded on fixed underwater cameras in 2015 and 2016, the study authors found 102 examples of about 10 octopuses picking things up and throwing them away. Often, the objects flew several body lengths away from the thrower.
“Doing this underwater, even at a short distance, seems highly unusual and quite difficult to do, making this an even more impressive behavior,” said the study’s co-author. David Scheel (opens in new tab)a professor of marine biology at Alaska Pacific University in Anchorage, told Live Science in an email.
Related: Octopuses Can Be So Scarily Smart Because They Share Human Intelligence Genes
Both male and female octopuses threw debris, although two females made about 66% of all throws. As for what prompted the octopuses to start flinging debris, about 32% took place while the octopuses were cleaning their dens. But 53% of mud crunching happened during an interaction with another octopus, a fish or one of the cameras.
Other octopuses were struck by the lobed debris on 17 occasions. In some incidents, the target would raise a hand just before a missile was fired, “perhaps in recognition of the act in preparation,” the scientists wrote. “Octopuses in the line of fire ducked, raised their arms in the thrower’s direction, or stopped, paused, or redirected their movements.”
But were the throwers intentionally trying to hit their octopus targets?
“The casts during the interactions differed from the casts when no other octopuses were present,” Sill said. “Shots that hit an obvious target were slightly different, in ways suggestive of a target, than shots that did not,” implying that flying debris was being targeted.
People usually teach toddlers that throwing things is not the best way to communicate. But for other animals that live in close communities — such as chimpanzees, capuchin monkeys and dolphins — smashing objects to members of the same population can serve as an important social cue, according to the study.
Octopuses are known to be extremely dexterous and able to manipulate various objects. For example, the veined octopus (Amphioctopus marginatus) stacks and transports coconut shells, which he uses to build a “mobile home”. But octopuses, as a rule, are not social creatures. They usually live alone and when they meet other octopuses, they sometimes fight them or even eat them.
But in recent decades, a growing body of evidence suggests that octopus interactions in some species are more complex than we once thought — and throwing things may be one way the animals communicate, scientists said.
In areas of Jervis Bay where dusky octopuses live, food and shelter materials are abundant. outside these patches of suitable habitat, resources are scarce. This could explain the unusual density of octopus populations there, which, in turn, would increase the number of encounters between creatures that would probably prefer to be the only octopus in town. Therefore, debris shedding may be a way for these usually solitary creatures to manage interactions with their octopus neighbors — including unwanted sexual advances, the researchers wrote.
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