According to a new article in the magazine PLoS ONE Octopuses in Australia have been filmed picking up mud, shells and algae and throwing them at each other. This is the first time this type of throwing behavior has been reported in octopuses, and the authors believe there is evidence that some of the recorded throws that hit others were intentionally aimed at others, suggesting that is that this behavior has a social role.
The female octopus throws garbage that hits the male who is trying to mate with her. The thrown material is mud, the throwing intensity is high, and the color pattern of the throwing octopus is uniformly dark.
Throwing behavior has not been observed in many animals, and throwing behavior that involves targeting another is even rarer. This behavior has so far only been observed in chimpanzees, capuchin monkeys, elephants, hippos and birds. Spiders also sometimes shake their webs when they sense a threat or prey, while an archer fish sprays water towards its prey. Dolphins also hit their prey on the water and can also throw objects as a kind of game.
The authors consider targeted throwing behavior as a form of tool use, especially when it involves another member of the same species, and think that it can serve as a means of communication, social bonding, or aggression. You might not expect to see this kind of throwing behavior in octopuses, which are usually aloof and antisocial: they hunt alone, and an unexpected encounter with another octopus can lead to an open fight. Some octopuses have even been seen eating their own kind.
Illustration of how octopuses throw garbage at another target octopus.
However, some recent studies have revealed another side of these amazing and highly intelligent creatures, showing that they can be patient with other octopuses and even use signals. Octopuses are masters of manipulating objects and build and maintain their shelters with various materials and often escape from their aquariums. They are agile enough to open the lids of containers. A viral video from 2015 in Japan showed an octopus opening its glass tank from the inside.
Octopuses have also been observed throwing bottles or toys in circles in their aquariums and catching them as they return. This behavior has been interpreted as a kind of game. The current study focuses on a species of octopus known as the sad octopus and its scientific name Octopus tetricus Is. Researchers studied a population of octopuses in the southern part of Jervis Bay in New South Wales, Australia (these areas are named Octapolis and Octalantis because of the dense population of octopuses).
The authors had previously informally noticed that octopuses in the area appeared to be throwing shells and wanted to investigate this further. In 2015 and 2016, researchers used underwater video cameras to record footage of octopuses and then reviewed the footage for examples of litter-throwing behavior.
The 2015 movies contained a strong collection of data. In these videos, the water clarity was good and many octopuses were recorded by the camera. In this series of videos, an active male octopus is easily recognizable due to the distinctive scars on his body from being bitten by a fish (octopus can be difficult to follow in this area due to their high population density).
The two female octopuses also have distinctive natural markings that can distinguish them from other octopuses. This enabled the researchers to study throwing behavior in interactions with other octopuses.
Thrown by a female octopus who is busy taking care of her nest.
Among a group of about ten octopuses, the scientists observed 102 examples of litter-throwing behavior over 24 hours of video over several days. Both male and female octopuses threw litter, but in 66% of cases, females did so. About half of the throws appeared to be in response to interactions with other octopuses (octopus checking the throwing octopus’s range or attempting to mate), and 17% of the throws hit other octopuses.
Octopuses make throws by repositioning their proboscis, which are tube-shaped structures that help octopuses swim. They shoot a fountain of water through their proboscis and create a reflection that drives the animal facing the water. To perform the launch, the octopus shoots water fountains at high speed through its proboscis to throw the debris it has collected in the opposite direction.
Is this behavior intentional? Determining whether the described behavior is intentional or not is very challenging; But researchers found evidence that some of the launches were targeted and possibly intentional. Throws occurring in the interactive environment were more intense than other throws and often involved throwing mud rather than shell or algae (shell and algae throwing is more associated with nest-cleaning behavior).
Octopuses can change their skin color, and dark colors are usually a sign of aggression. Octopuses that were dark in color threw trash more vigorously and were more likely to hit other octopuses. Target octopuses often responded by backing off or raising their arm, apparently as a defensive behavior. The authors concluded:
Even if the intention behind these throws is not to hit other octopuses, they have social effects in the interactions between the octopuses of this place. Octopuses can definitely be added to the short list of animals that throw or propel objects, and temporarily to the even shorter list of animals that target other animals with their throws.
If they are indeed aimed at others, these launches are aimed at members of the same population, and so octopuses join the small group of animals that have this rare form of launch.