Australasian Science: Australia's authority on science since 1938

Catfish among the Pigeons

By Magdeline Lum

It might be time to add to the selection of bait and lures used to catch freshwater fish now that scientists have observed catfish hunting pigeons and tigerfish catching swallows.

Along the banks of the Tarn River in the south-west of France, catfish are hunting pigeons. If that is hard to believe, researchers from the University of Toulouse have observed the catfish temporarily stranding themselves on land to catch their prey. The scientists are hailing this behaviour as evidence of adaptive behaviour.

The pigeon-hunting catfish originated east of the Rhine River, and in 1983 they were introduced to the Tarn River.

In 2011, researchers positioned themselves on a bridge above a gravel island and watched the fish for 4 months. During this time they saw 54 pigeon-hunting events. In 28% of cases catfish successfully captured pigeons on land and dragged them back into the water to eat.

Pigeons gather at the water’s edge to bathe as catfish measuring 1–1.5 metres patrol in the shallows. In nearly all cases, the catfish would launch themselves towards a pigeon moving in water.

In some of these instances the catfish were temporarily stranded on land. The catfish would then wriggle back into the water with its prey. This suggests that the catfish are detecting vibrations through the water rather than relying on vision.

The hunting behaviour of the catfish has been likened to bottlenose dolphins that drive fish onto beaches, and also to killer whales in Argentina that thrust themselves onto beaches when hunting sea lions. The catfish of the Tarn River have thus earned the nickname “freshwater killer whales”.

It is unknown what caused the catfish to develop the behaviour to hunt pigeons. The researchers suggest that the action of introducing a species to a new environment may trigger some individuals of the population to develop new behaviours.

The pigeons in France are not the only birds being targeted by fish. Scientists in South Africa have observed and filmed the African tigerfish Hydrocynus vittatus hunting and catching barn swallows in flight. Rumours of the tigerfish leaping out of the water to catch fish have been circulating since the 1940s but there has never been any evidence of this behaviour until now.

The research team had initially set out for Schroda Dam to study the migration and habitat use of tigerfish. They did not intend to study fish leaping out of the water to catch swallows. In total, the researchers observed up to 20 successful hunts per day over their summer study.

Individual fish were being monitored via radio tags. The fish mostly fed at dawn and dusk on other fishes and spent the rest of the time in sheltered areas. However, tigerfish were observed to swim out to open water in the mid-morning. When the research team observed their behaviour, they saw tigerfish hunting and eating swallows.

The types of attacks from tigerfish varied. Some tigerfish swam at the surface following the birds before leaping to catch their prey. Other attacks came from deeper water.

Bass, eels, piranhas and pike have been acknowledged as freshwater species that prey on birds floating on the surface of the water or at the water’s edge. The African tigerfish is the first freshwater species observed catching birds mid-flight.