Scientists have discovered that female octopuses will "throw" objects at males when feeling harassed. When an annoying male enters the scene, a female octopus will gather projectiles like shells or silt using her tentacles before launching the debris with a siphon of water. Though researchers have witnessed octopuses use this throwing technique in den building, this is the first time it’s been documented as a targeted attack on another octopus, according to a new paper published on the pre-print server bioRxiv that has not yet been peer reviewed.
In 2015, biologist Peter Godfrey-Smith of the University of Sydney and his colleagues were studying a group of common Sydney octopuses of the Australian coast, in an octopus-rich area called Jervis Bay. The team observed the octopuses launch objects and sediment several body lengths away. Though scientists call the behavior "throwing," the cephalopods usually situation an object in their tentacles and propel it with a jet of water.
Scientists already knew the clever cephalopods used this throwing behavior as a housekeeping technique to keep dens free of debris, but it appeared some octopuses were aiming detritus at others. The team returned to Jervis Bay the following year to collect more footage.
The recent paper confirms what Godfrey-Smith and his colleagues suspected: Octopuses can intentionally target other individuals with their projectiles. In one example captured in 2016, a female octopus threw silt at a male who was attempting to mate with her. She threw silt at him ten times, hitting him on five of those attempts. The male occasionally tried to dodge the sentiment but was only successful around half of the time, reports Samantha Berlin of Newsweek. Octopuses throw with particular vigor when targeting others and prefer to launch silt instead of shells.
“That sequence was one of the ones that convinced me [it was intentional],” says Godfrey-Smith to New Scientist’s Michael Le Page.
When octopuses throw things during den-building, the object is usually angled between their front two tentacles—but when throwing at other octopuses, they shot between tentacles further to right or left. They found that females used this targeting technique most often, usually at males trying to mate with them. Octopuses are one of just a handful of creatures, including chimps and elephants, that will target members of their own species, per the Independent’s Tom Batchelor.
“It’s pretty rare. Especially rare is throwing of objects at other members of the same population,” says Godfrey-Smith to New Scientist.
Of the 101 throws they observed in 2015, the vast majority—around 90 percent—were done by females, reports Katie Camero for the Herald Sun. Two particular females were responsible for about 66 percent of the oberved throws, both targeted and not.
Though most octopuses used a siphon of water to launch their projectile, one female threw a shell frisbee-style with its tentacles. Interestingly, male octopuses sometimes raised their tentacles in anticipation, but didn’t reciprocate the attack.