Sometime after catfish were introduced to southwestern France in 1983, fisherman working along the winding banks of the Tarn River started to notice something different about the invasive catfish population, writes Ed Yong on his blog Not Exactly Rocket Science: “These particular catfish have taken to lunging out of the water, grabbing a pigeon, and then wriggling back into the water to swallow their prey.”
While observing the catfish, the researchers also noticed that the fish only attacked when the pigeons were active in the water. Motionless birds, even when in the water, were left alone. This led them to conclude that the catfish were not using visual cues to spot the birds, but by sensing water vibrations instead. Essentially, the pigeons, by their movements, were triggering the attacks.
Of the 54 tries they caught on camera, just over a quarter of them ended up with the catfish catching their flighty foe. Such sea-to-soil hunting techniques aren’t unique in nature: killer whales do it, as do dolphins. And, in the opposite direction, sea birds have been invading fishes’ habitats for ages.