Scientists observed the catfish lying in wait in shallow water in order to catch the pigeons.
The behaviour was observed on a small island in the Tarn where pigeons go to drink water and wash. Taking pictures and video from a bridge overhead, the scientists recorded 54 ‘beaching behaviours’, where the catfish risked being stranded on the bank to catch their feathered prey. 28 percent of these events were successful with the land birds returned to the river by the fish and swallowed.
Eating pigeons is not a ‘native’ behaviour of catfish; the scientists were alerted to their unusual diet by local fisherman. The catfish were introduced into the River Tarn in 1983 where they have established a self-sufficient population. The scientists believe that catfish may have supplemented pigeon to their diet due to a shortage of their usual prey: crayfish and smaller fish.
Julien Cucherousset, a biologist at the University of Toulouse and lead author of the paper, collected tissue samples from the catfish and examined their nitrogen and carbon content in order to determine the amount of pigeon that made up the catfish diet. They found that it was only particular catfish individuals that were eating pigeons and these individuals were eating correspondingly less fish.
The scientists believe that competition for food within the species may have led some catfish to look for alternative food sources. Further investigation is needed to confirm whether this is the case. The team’s " target="_blank">findings are published in the open-access journal PLOS One.