In the Line of Fire: Debris Throwing by Wild Octopuses

Abstract

Wild octopuses at an Australian site frequently propel shells, silt, and algae through the water by releasing these materials from their arms while creating a forceful jet from the siphon held under the arm web. These "throws" occur in several contexts, including interactions with conspecifics, and material thrown in conspecific contexts frequently hits other octopuses. Some throws appear to be targeted on other individuals and play a social role, as suggested by several kinds of evidence. Such throws were significantly more vigorous and more often used silt, rather than shells or algae, and high vigor throws were significantly more often accompanied by uniform or dark body patterns. Some throws were directed differently from beneath the arms and such throws were significantly more likely to hit other octopuses. Throws targeted at other individuals in the same population, as these appear to be, are the least common form of nonhuman throwing.