In a paper published in 1807, Prussian naturalist and explorer Alexander von Humboldt claimed to have observed South American electric eels exhibiting a behavior that has not been recorded since. Von Humboldt hired local fishermen to collect electric eels (Electrophorus electricus) for his research, which they did by a process he dubbed "fishing with horses." The fishermen led about 30 horses and mules into a pool known to be home to electric eels, which provoked the eels to attack by swimming to the surface and pressing themselves against the horses while discharging. This exhausted the eels, which could then be safely collected.
According to Kenneth Catania, a scientist at Vanderbilt University in Tennessee, subsequent investigators have been skeptical of Von Humboldt's account, mostly because no similar eel behavior had been observed in the intervening 200-plus years - until now. But in a study published in the Proceedings of the National Academy of Sciences (PNAS) today, Catania reports the results of a study in which he was able to provoke a defensive behavior by eels housed in an aquarium that largely supports Von Humboldt's story.
Catania writes in the PNAS paper that the behavior consists of the eels approaching a target and leaping out of the water to press their chins directly against the threat and deliver their "high-voltage volleys."
"This shocking behavior likely allows electric eels to defend themselves during the Amazonian dry season, when they may be found in small pools and in danger of predation," Catania writes.
You can see the behavior for yourself in this video, in which an eel attacks an imitation predator embedded with LEDs powered by the eel's electric attack:
Sources: taken and re-shared from Mongabay News