Video footage captured by divers reveals that octopuses can cover gills, blind fish, or even sacrifice their arms in an effort to cope with much larger eels.
(Video: Jorge Hernández-Urcera)
The European eel is at least three times heavier than the octopus. However, in a video shared by Jorge Hernández-Urcera, a marine ecologist at the Oceanographic Institute of the Spanish National Research Council, the octopus confronts its larger foe by covering the eel’s eyes, stuffing its arm into its mouth, and blocking its gills, according to Wiley Online Library.
“I think the large size difference would make it difficult for the octopus to escape death,” Hernández-Urcera said. However, the octopus not only successfully defended itself but seemed to gain the upper hand. The divers filming the video interrupted the struggle, allowing both animals to survive, with the octopus retreating after expelling ink.
Hernández-Urcera’s research team collected the videos and analyzed previously undocumented behaviors. He is confident that the footage from 2008 off the coast of Galicia in northwest Spain demonstrates the intelligence of octopuses and the richness of their defensive behaviors. However, this alone is not enough to indicate that this technique is a standard offensive maneuver for octopuses.
More recently, Hernández-Urcera obtained additional footage demonstrating that octopuses will choke, blind, or even sacrifice limbs in their efforts to defend themselves against much larger eels. He published his research in the journal Ecology and Evolution. In a 2022 video recorded off the coast of Asturias in northern Spain, another octopus employed a similar tactic against an attacking eel. In response, the eel quickly spun to escape the octopus’s grasp. At the moment the octopus escaped, it dislodged the eyeball from one side of the eel’s head using its powerful suckers.
The eel lost an eye in the battle with the octopus.
In each video, the octopus was able to sacrifice an arm, similar to how lizards drop their tails to distract predators, according to Hernández-Urcera. In the first video, the octopus lost three arms, while the individual in the second video lost two arms, but they can regenerate fully within about 45 days, according to some laboratory experiments. However, octopuses do not always come out on top. In a third video recorded in 2023 near Galicia, an eel caught the octopus by the head, then spun it around and slammed it against a rocky outcrop. The octopus appeared to be paralyzed, and the eel swam 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 arm may act instinctively. He shared that he has observed numerous battles between octopuses, where one blocked its opponent’s gill openings with its arm to suffocate it.
Hernández-Urcera is uncertain whether the fighting techniques in the videos he collected are instinctual or learned behaviors. European eels typically hunt at night, while the footage was recorded during the day. The researcher suggests that such encounters may occur more frequently than expected.
