The octopus sacrifices its arm to escape the eel

Videos filmed by divers reveal that octopuses can cover their gills, blind their eyes or even sacrifice their arms in an effort to deal with eels many times larger .

 (Video: Jorge Hernández-Urcera)

Sea eels are at least three times heavier opponents than octopuses. But in a video shared by Jorge Hernández-Urcera, a marine ecologist at the Institute of Marine Research of the Spanish National Research Council, and his colleagues, the octopus deals with larger enemies by covering its eyes. eel, stuffing his arm into its mouth and covering its gills, according to Wiley Online Library .

"I think the large difference in size will make it difficult for the octopus to escape death," Hernández-Urcera said. However, the octopus not only successfully defended itself, but also seemed to have the upper hand. Divers filming video interrupted the fight, two animals survived, and the octopus left after spraying ink.

Hernández-Urcera's research team collected videos and analyzed behavior that had never been described before. He is convinced that the video, shot in 2008 off the coast of Galicia in northwestern Spain, shows the intelligence of octopuses and the richness of their defensive behavior. But that is not enough to show that this technique is a common type of octopus attack.

More recently, Hernández-Urcera obtained additional videos to demonstrate that octopuses will choke throats, cause blindness, and even sacrifice limbs in an attempt to defend themselves against much larger eels. He published the research in the journal Ecology and Evolution . In a 2022 video filmed off the coast of northern Spain's Asturias region, another octopus uses similar tactics to fend off attacking eels. In response, the eel quickly rotated to escape the octopus's hand. At the moment the octopus escaped, it popped the eyeball in one of the eel's eyes through its extremely strong suction cup.

The eel lost an eye in a fight with an octopus.

In each video, the octopus can sacrifice its arms, similar to a lizard losing its tail to distract the attention of predators, according to Hernández-Urcera. In the first video, the octopus lost three arms and the individual in the second video lost two arms, but they were able to regrow full limbs in about 45 days, according to some laboratory tests. However, the octopus does not always win. In the third video, shot in 2023 near Galicia, the eel grabs the octopus's head, then spins it around and smashes it against the cliff. The octopus appears to be paralyzed and the eel swims away with its prey.

Piero Amodio, a biologist and comparative psychologist at the Anton Dohrn Zoological Station in Naples, Italy, suggests that when covering the eel's gills, the octopus's arms may act instinctively. He shared that he had observed many fights between octopuses, in which one octopus covered its opponent's gill opening with its arm to suffocate it.

Hernández-Urcera isn't sure if the fighting techniques in the videos he collected are instinctive or learned behavior. Sea eels usually hunt at night while the video was filmed during the day. The researcher believes that these types of clashes may occur regularly.