Sometimes, an octopus is so displeased with its fish partner that it demonstrates its ire by suddenly punching the later in the head. But sometimes octopuses punch fishes for no reason at all -- indicating that they did it simply because they wanted to. This analysis was published in "Ecology", which documents octopuses punching fish during collaborative feeding sessions.
There are times when octopuses team up with fish to find food. The hunt together since the collaboration helps them to cover more area, increasing the chances of catching prey.
Analysing collaborative feeding sessions, researchers found that octopuses were punching fishes to prevent exploitation and to ensure collaboration. But there were many instances where the eight-armed animal lashed out at fishes for no reason at all.
Its victims included the following fishes -- Tailspot squirrelfish, black tip, yellow-saddle, and Red Sea goatfishes.
Although the researchers did not completely understand the punching process, they did find that it serves an important aspect in studying how species interact with each other.
"...When big blue octopuses (Octopus cyanea), also known as day octopuses, are displeased with their fish partners, they demonstrate their ire by suddenly punching the fish in the head," a report in Live Science said.
The eight-armed animal use "a swift, explosive motion with one arm," in an attack "which we refer to as punching", the report quoted study authors.
Octopuses punch fishes. YES. OCTOPUSES. PUNCH. FISHES!!
Our new paper is out on @ESAEcology, showing that octos express this behavior during collaborative hunting with other fishes. This was probably the most fun I had writing a paper. Ever! (small )https://t.co/Vwg9BoaSUo pic.twitter.com/PIYuVXpM9t
— Eduardo Sampaio (@OctoEduardo) December 18, 2020
"I laughed out loud, and almost choked on my own regulator," Eduardo Sampaio, the lead study author and PhD student at the University of Lisbon and the Max Planck Institute of Animal Behavior, said.
"But I still marveled at it every time I saw it," he told Live Science in an email.
PARTNERS, AND NOT FRIENDS
Sometimes, fishes and octopuses work together for more than an hour, scouting different locations.
"Octopuses pursue prey that dart around rocks and into tight spaces in the reef, while bottom-feeding fish such as the yellow-saddle goatfish [Parupeneus cyclostomus] scour the seafloor, and other fish species patrol the water column," the study said.
However, these partnerships don't always work out well for the fish. Researchers observed eight distinct incidents while diving in Eilat, Israel, and in El Quseir, Egypt, between 2018 and 2019. They witnessed octopuses suddenly punching out their supposed partners, the report said.
"The fish would get pushed to the edge of the group, or would actually leave the group. Sometimes after a while, it would return, other times it would not return at all. The octopus would leave the fish alone after displacing it," the author said.
BUT WHY DO OCTOPUSES PUNCH FISHES?
Researchers said that the participants in the collaboration are looking out for each other's best interests and it is possible that an octopus might be more productive while working alone -- "One possibility could be that these negative acts, while harmful to the fish, in the end, cost the octopus less energy than cooperation would."
"If opportunity knocks, alliances may be discarded, and the octopus will look out for itself," Sampaio explained.
He said, "Despite collaborating, each partner will always try to maximize its benefits...In the cases where prey is readily available, the octopus seems to use 'punching' as a way to control the partner's behaviour in a self-serving way," literally knocking aside the competition to steal a tempting meal.
Scientists even recorded events where it wasn't immediately evident how the octopus benefited by punching the fish.
"One possibility could be that these negative acts, while harmful to the fish, in the end, cost the octopus less energy than cooperation would. Punching could also be punishment so that the fish would then be a better partner in future collaborations," Samapio said.
However, these explanations are speculative. Researchers need to look at many more octopus-vs-fish knockouts to unravel what motivates an octopus to throw the first punch.
"We suspect that the main reason is related to prey opportunities, of course, because that is also the reason why these groups naturally form in the first place, given the complementary hunting strategies of the partners," the study author said.