Electric eels gathering and herding prey in preparation to launch a coordinated attack. A team of scientists describe this novel behavior in the Jan. 14 issue of the journal Ecology and Evolution. The findings overturn the idea that these serpentine fish are exclusively solitary predators and open the door to new questions about how these little-understood fish live.
For the majority of the day and the night before hunting as a group, the eels lay almost motionless in the deeper end of the lake, only occasionally coming to the surface to breathe. But at dusk and dawn the congregation began to stir.
In these twilight hours, the eels started interacting with each other and then began swimming in a large circle. This churning circle of electric eels corralled thousands of the 1-to-2-inch tetras into tighter and tighter shoals. The researchers watched the group herding the concentrated tetras from the deeper end of the lake—around 12 feet deep—to shallow, 3-foot deep waters.