Octopuses have been captured throwing dirt at each other, photos reveal

A study published today revealed that octopuses deliberately throw debris such as sand and rocks at each other.

The study led by Peter Godfrey-Smith at the University of Sydney and colleagues indicates that the octopuses grabbed debris and threw it, frequently tossing it several body lengths away, through the water using a jet of water from their siphon. Octopuses had to adjust their siphon into an unusual position in order to conduct the throws, indicating that the activity was intentional.

In 2015 and 2016 by using underwater cameras, the researchers achieved in shooting the gloomy octopuses' behavior in Jarvis Bay, Australia. Despite individual identification was not always possible, they were able to find 102 instances of debris throwing in a group of about 10 octopuses after studying 24 hours of video over many days.

Why do they throw debris at each other?

"Both sexes were observed throwing, but 66 percent of throws were performed by females," says the study. But the main question is "why"?

About 17 percent of throws hit other octopuses, and about half of throws happened during or right after contact with other octopuses, such as arm probes or mating attempts. Dark skin tones are typically associated with aggression in octopuses, and the researchers discovered that these creatures tended to toss more fiercely and were more likely to hit another octopus. When an object was thrown towards an octopus, they frequently changed how they behaved by ducking or elevating their arms in the thrower's direction.

The first time that throwing behavior in octopuses has been documented right now. The actions seen show that octopuses are capable of throwing objects specifically intended for other people, a behavior that has only been seen before in a small number of non-human creatures, according to the authors, even though it can be challenging to ascertain why they are doing it.

“Wild octopuses project various kinds of material through the water in jet-propelled ‘throws,’ and these throws sometimes hit other octopuses. There is some evidence that some of these throws that hit others are targeted, and play a social role,” the authors also add.

Do you know these?

A species of octopus found in the subtropical waters off eastern Australia and New Zealand is called Octopus tetricus, sometimes known as the gloomy octopus or the common Sydney octopus. O. tetricus is a species of commercial value that is a member of the genus Octopus vulgaris. The morphology of every species in the O. vulgaris genus is the same. The name O. tetricus translates to "the gloomy octopus" in English.

The typical coloration of octopus tetricus is grey to brown with rufous arm faces that taper toward the tip. Their eyes are normally white in color, and their skin has numerous small, regular-shaped patches and huge, warty structures that the octopus uses to give the appearance of being spiky when it is trying to pass for seaweed. The adults often have a 2-meter arm span (6.6 ft).

Study abstract:

Wild Octopus tetricus 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 at a site in Jervis Bay, Australia, including in interactions with other octopuses. Material thrown in interactive contexts frequently hits other octopuses. Some throws appear to be targeted at other individuals, as suggested by several kinds of evidence: Throws in interactive contexts were more vigorous than others and more often used silt, rather than shells or algae. High-vigor throws were more often accompanied by uniform or dark body patterns than other throws. Some throws were directed differently from beneath the arms, and such throws were more likely to hit other octopuses. Throwing at other individuals in the same population, as apparently seen in these octopuses, is a rare form of nonhuman projectile use, previously seen only in some social mammals.