When female octopuses are trying to keep males at bay, they throw stuff. Sometimes. So found a study that has yet to be peer-reviewed. Researchers from the US, Canada, and Australia say their finding builds on research done in 2015, in which they recorded wild octopuses in Jervis Bay off Australia throwing things. They returned and videoed the creatures again in hopes of learning more, and they say their analysis of the footage found female octopuses will occasionally throw material at a male, typically one attempting to mate with her. The males duck and evade the projectile about half the time, reports Phys.org.
As for what's thrown, the researchers say it's rocks, silt, or shells, which they release "from their arms while creating a forceful jet from the siphon held under the arm web," per the paper. New Scientist reports one female octopus in particular convinced researcher Peter Godfrey-Smith of the University of Sydney that the behavior is intentional: She was seen throwing silt 10 times at a male who was trying to mate with her. The male tried to duck four times and dodge the throw in advance twice; she successfully hit him five times.
The researchers say they didn't spot any males returning fire, but they did observe females "throwing" in other contexts, like when building a nest or trying to move objects out of the way. In the paper they note that all this throwing is less usual than you might think. "The throwing of objects is an uncommon behavior in animals" and "has sometimes been seen as distinctively human." Targeted throwing has been spotted in animals like chimps, elephants, mongooses, and birds, though many were seen doing so in captivity or among "populations acclimated" to human presence. (Read more discoveries stories.)