Science Figures Interpreted and Analyzed by RealClearScience
It's a sunny, peaceful day in southern France. A flock of pigeons sets down on a narrow island in the Tarn River. The birds coo and preen themselves in the calm, clear water. Suddenly... chaos. Feathers hurriedly flap and water splashes. The commotion is all over in seconds, except there's one less bird on shore, snatched up in the gaping clutches of a humongous European catfish, a "freshwater killer whale."
European catfish are normally about four to five feet long and weigh upwards of fifty pounds. Originally found east of the Rhine River in Europe, the catfish have been introduced to, and are flourishing in, a host of new environments. The species has been swimming the Tarn River since 1983.
While it usually predates on smaller fish and crayfish along the river bottom, the catfish is now reported to feed on a different type of prey altogether: pigeons.
In the Dec. 5th publication of PLoS ONE, French researchers describe a predation behavior not seen within the fish's native range. The catfish will lurk in the shallow water near flocks of pigeons and intentionally beach themselves in an attempt to capture one of the birds. The researchers observed such a behavior on 45 different occasions. In 28% of them, catfish were successful in snatching a bird, returning it to the water, and swallowing it whole. (See the video!)
The beaching behavior was quick, lasting no more than four seconds. The researchers theorize that the catfish use water vibrations to detect the prey, as no motionless birds were ever attacked.
"Introduced species can display ecological and evolutionary adaptations in their new environment, and the occurrence of new behaviors can increase invasive species success," the researchers say.
"This new predation behavior might represent an extreme example of the ability of introduced species to adapt to a new environment."
It also presents a new reason for French pigeons to not go near the water (cue JAWS music).
Source: Cucherousset J, Boulêtreau S, Azémar F, Compin A, Guillaume M, et al. (2012) “Freshwater Killer Whales”: Beaching Behavior of an Alien Fish to Hunt Land Birds. PLoS ONE 7(12): e50840. doi:10.1371/journal.pone.0050840